2011: The Year in Motion

True to its name, the motion control industry didn’t stand still in 2011. There was quite a bit of activity on a wide variety of fronts. Here is a very brief, necessarily incomplete, and of course highly subjective take on a few of the top motion control technology trends we saw in 2011.

1. Networks

Perhaps the most significant and ongoing trend is the rise of Ethernet-based control networks. You see this with Rockwell’s Integrated Motion over Ethernet/IP as well as network standards based on Ethernet protocols such as Beckhoff’s EtherCAT standard. And a major reason for this trend is that using an Ethernet-based standard allows the manufacturing floor to more readily coordinate with other areas of an organization, most significantly with the larger enterprise resource planning, or ERP, functions within a company. But it also lets you integrate motion control with process and discrete machine control and even safety control.

2. Software

Specifically, simulation and modeling software. The relative ease of simulation and modeling is growing, with the benefits including the ability to slash design time and effort by doing increasingly sophisticated real-world modeling simulation of complex control systems and getting useful results from which to tweak the model before investing substantial time and material in building a prototype.

Another trend with software is the increased integration of what were once separate software packages. So for instance, many companies are offering software packages that integrate modeling and simulation functions with the motion controller, allowing an entire design to be done within one common software environment.

3. Controllers

Last but certainly not least is the area of motion controllers, the hardware itself. The general trend here is for manufacturers to add features, such as support for Ethernet-based network protocols and other more sophisticated features such as diagnostics and programming capabilities. And this trend of more features is common across the full spectrum of controllers, from stand-alone controllers for simple single-axis applications to powerful multi-axis controllers.

Summary

Of course, the motion control industry isn’t an island but is integrated with the larger world of global politics and economics. As just one example, this is why the supply of neodymium in China, used in the manufacture of rare-earth permanent magnets, is watched so closely, as China is the main exporter of neodymium at this time. So the price and availability of the material can easily affect the supply chain for motor manufacturers around the world. In addition, as the direction of the world economy remains uncertain and the world now more interconnected than ever before, recessions or upheavals in one part of the world can have a significant impact elsewhere.

It’s these global factors as well as technological ones that will make for an intriguing and anything-but-dull 2012.

BEI’s HS52 explosion proof rotary encoder revealed

BEI Sensors (www.beisensors.com) has unveiled a space-saving and ultra rugged industrial encoder that meets the required standards and certifications for use in potentially explosive environments. Model HS52 is the industry’s first ATEX and UL rated explosion proof hollow shaft encoder.

This rotary encoder can be operated directly in Zone 1 and Division 1 work environments where ignitable concentrations of flammable liquids vapors or gases are likely to exist in normal operating conditions.

The reliable and rugged rotary encoder eliminates the need for an accompanying Intrinsic Safety barrier, effectively simplifying installation. This also results to a more streamlined feedback system for the explosion proof environments.

Utilizing the explosion proof construction method, the HS52 rotary encoder is fitted in an enclosure that has the capability to contain and withstand even the most volatile gas-to-air mixture internal explosion.

The rotary encoder is equipped with a flexible shaft bore design, allowing it to be rigidly mounted to prevent stress to encoder bearings. The design also provides a more secure attachment to the hazardous area conduit fittings.

In addition, the encoder’s compact hollow shaft design provides engineers space-saving advantages not otherwise found in traditional shafted encoders. As ideal position sensing solution for oil and gas industries, the HS52 is also suitable for use in spray painting applications, solvent refining operations and other explosive environments where operating conditions are extreme and space is a premium.

Baldor enhances performance of Dodge tapered roller bearing

Baldor (www.baldor.com) has unveiled the latest Dodge Type E-Xtra tapered roller bearing, which comes with advanced sealing system and high load ratings.

Since the launch of the first Dodge Type E bearings in 1938, the range has been continuously improved to meet the changing demands of industrial customers. This innovation is continued with the addition of the newest Dodge Type E-Xtra bearing. It has been specifically designed with features that will ensure optimum performance with outstanding reliability.

The US-made high capacity tapered roller bearing insert permits a combination of thrusts and radial loads, producing the industry’s highest load ratings. Lab tests prove that the latest tapered insert offers 13 percent to 14 percent increase in ratings than the previous insert. It features a carburized inner ring that can resist cracking and absorb shock.

The new bearing comes with XTS triple-lip seal, a state-of-the-art system that protects the bearing from contamination in wet or dusty environments, while the oversized dual Springlok collars serve as flingers for added seal protection. Customers can also opt for the XTS Plus sealing system, which is integrates the Dodge E-Tect seal kit for additional protection, making it suitable for extreme conditions.

For easy installation, the bearings have been pre-lubricated, preassembled and factory adjusted. They are also offered in various configurations, including two- and four-bolt pillow blocks, piloted flanges, flanges, wide slot take-ups and top angle take-ups. They are also available in imperial and metric versions.

Right Angle DC Gearmotor comes with integral failsafe brake

Midwest Motion Products, Inc. (www.midwestmotion.com), a distributor of a vast array of mechanical and electronic products, has announced the release of its latest DC Gear Motor that features an integral failsafe brake.

Model No. MMP D22-376D-24V GRA60-032 BR-005 accepts any 24VoltDCsource, including battery or solar power. Measuring just 2.24 inches in diameter and 7.2 inches long, including the brake, this robust Gear Motor comes with a keyed output shaft of 14 mm diameter and 25 mm long. It can easily mounted as it features four “face mount” M5.5 threaded holes, spaced equally on a 52 mm Dia. B.C.

This reversible gear motor delivers a 3.3 Nm (29 lb. in.) torque output, at 230 rpm. Weighing around six pounds, the compact gear motor offers an efficient design that requires only four Amps at 25 Volts DC to produce its Full Load Torque. This translates into very low noise operation, long battery charge and reduced costs for related drive electronics.

The model’s integral failsafe “holding” brake measures only 2.25 inches in diameter, as well as operates on similar supply voltage as the motor.

Rated with “IP 54” protection level, the DC Gear Motor’s unique design makes it suitable for operation in hazardous environments. Variable speed control can be achieved with the company’s compatible speed controls, Model MMP 20A-24V-RSP or MMP 25A-24V.

What is a Gear?

The primary task of a gear is to mesh teeth with another toothed part to transmit torque or to translate rotation. Thus, geared devices can change the speed, torque, and direction of a power source. When two gears of unequal number of teeth combine, it results in a mechanical advantage, with both the rotational speeds and the torques of the two gears differing in a simple relationship.

A number of devices use gears in some mechanical arrangement and these devices go by a number of names, depending on the branding of the manufacturer. Here is a look at some of the more common terms.

Gear reducers
Gear reducers, also known as speed reducers, are a component of many mechanical, electrical, and hydraulic motors. Essentially it is a gear or series of gears combined in such a manner to alter the torque of a motor. Typically, the torque increases in direct proportion to the reduction of rotations per unit of time.

Speed reducers come in two varieties: base mounted and shaft mounted. The shaft-mounted type, in turn, has two variations. One is truly shaft mounted in that it is supported entirely by the input shaft of the drive machine, with torque reaction absorbed by a special link. The other is mounted to the driven-machine housing so the input shaft does not absorb reducer weight or torque reaction. By AGMA definition, the term “speed reducer” is applied to units operating at pinion speeds below 3,600 rpm or pitch-line velocities below

5,000 fpm. Reducers operating at speeds higher than these are called “high-speed units.” Catalog ratings and engineering specifications for speed reducers are generally based on AGMA standards.

There are as many types of speed reducers as there are types of gears. Worm gear reducers are used in low to moderate horsepower applications. They offer low initial cost, high ratios, and high output torque in a small package, along with a higher tolerance for shock loading then helical gear reducers. The ratio of a worm gear set is the ratio of the number of teeth in the gear to the number of threads (starts or leads) on the worm.

Helical reducers are used in higher horsepower applications where long-term operational efficiency is more important than initial cost. The ratio of a helical or bevel gear set is simply the number of teeth in the larger gear divided by the number of teeth in the smaller gear.

Spur gear reducers have a gear wheel with radial teeth parallel to the axle. In bevel and spiral bevel gears, the gear wheel meshes with another at an angle between 90o and 180o.

Gearhead
A gearhead is often another term for gear reducer; however, it does not limit the unit’s function to speed reduction. Gearheads are mainly used wherever an application calls for high torque at low speed. It reduces a load’s reflected mass inertia, which makes accelerating heavy loads easier, enabling a design to use a smaller motor.

Gearheads come in a variety of styles from basic spur gearheads to more complex planetary gearheads and harmonic-type gearheads, each with their own characteristics and suitable applications.

In some applications, gearhead backlash may become an issue. In this case, consider using a gearhead with low backlash or zero backlash.

What are Motion Control Networks?

Multi-axis motion control typically uses event-based synchronization. This level of synchronization is defined as scheduled, absolute hard delivery of time-critical cyclic data across the network. Delivery variability must be less than 1 µs, which is also known as jitter.

While a number of networks exist for “motion control,” it is important to define the time delivery needs for the given application. Synchronized multi-axis motion will have different timing needs than a divert actuator on a conveyor system.

A requirement for jitter-free motion can narrow network choices. Here is a brief synopsis of a few common networks used in motion control applications.

EtherCAT®
Ethernet for Control Automation Technology (EtherCAT) was developed by the Beckhoff company. It is fast and deterministic, and processes data using dedicated hardware and software

It uses a full duplex, master-slave configuration, and accommodates any topology. It can process 1,000 I/O points in 30 µs and communicate with 100 servo axes in 100 µs. Axes receive set values and control data and report actual position and status. A distributed clock technique that is a simple version of IEEE 1588 synchronizes the axes with less than 1 µs of jitter.

This protocol can deliver fast throughput because messages are processed in hardware before they are forwarded to the next slave. Slaves read data relevant to them as the data frame passes and they insert new data into that same data stream on the fly. This procedure does not depend on the run-time of the protocol stack, so processing delays are typically just a few nanoseconds.

EtherNet/IP (EIP)
Standard Ethernet cannot guarantee jitter of less than 1 µs because of the data layer’s use of Carrier Sense Multiple Access/Collision Detection (CSMA/CD) techniques to control packet transmission. To overcome this issue, ODVA developed EtherNet/IP, and it did so without changing any of the four lower layers of Ethernet.

EtherNet/IP is an industrial application layer protocol operating over the Ethernet medium and used for communication between industrial control systems and their components, such as programmable automation controllers, programmable logic controllers or I/O systems. The “IP” stands for “Industrial Protocol,” referring to Rockwell Automation’s adoption of Common Industrial Protocol (CIP™) standards as EtherNet/IP was developed.

EtherNet/IP with CIP Motion as the application layer removes the requirement for strict determinism from the network infrastructure and entrusts the end devices with the timing information necessary to handle the real-time control needs of the application. Thus, this network can deliver the high performance, deterministic control required for closed-loop drive operation using standard, unmodified Ethernet (complying with Ethernet standards, including IEEE 802.3 and TCP/IP). CIP is also used by DeviceNet and ControlNet, so these networks are interoperable.

CIP Motion accomplishes real time data transmission through the application profiles that define the technology. Those profiles allow position, speed and torque loops to be set within a drive. This protocol makes use of CIP Sync technology, the IEEE-1588 compliant Precision Clock Synchronization, which is also mapped into the CIP object model, to coordinate precise, synchronized motion control.

CIP Sync consists of a Time Sync object and associated services for synchronizing nodes to within ± 100 ns of one another. EtherNet/IP with CIP Motion allows 100 axes to be coordinated with a 1 ms network update to all axes.

Sercos
Sercos is a digital bus that interconnects motion controllers, drives, I/O, sensors and actuators for numerically controlled machines and systems. It is designed for high-speed serial communication of standard closed-loop real-time data over a noise-immune, fiber optic ring (Sercos I & II) or Industrial Ethernet cable (Sercos III).

In a Sercos interface system, all servo loops are normally closed in the drive to reduce the computational load on the motion controller and synchronize more motion axes than it otherwise could. In addition, closing all the servo loops in the drive reduces the effect of the transport delay between the motion control and drive.

Sercos III is the open, IEC-standard third-generation version that transmits data over Industrial Ethernet cabling and protocol for real-time control. It combines the best of both Ethernet and previous Sercos designs for deterministic bi-directional real time motion and I/O control. It delivers rich I/O communication capabilities while enabling all conventional protocols to be transmitted over the same Ethernet network efficiently in parallel with Sercos real-time communication.

Sercos III achieves cycle times as low as 31.25 µs. It supports up to 511 slave devices in one network, with multiple networks possible in a system.

What is Linear Motion?

Linear motion is an area of motion control encompassing several technologies including linear motors, linear actuators, and linear rolling guides and bearings, among others.

Linear motors
Traditional linear motors are basically a permanent magnet rotary motor rolled out and laid flat. It’s as if the stator and rotor were cut along a radial plane and then unrolled so that they could provide linear thrust. When the stationary part of the motor is energized, it causes motion in the moving part that contains some kind of conductive material.

Linear motor benefits include high speeds and fast response times, high precision and stiffness, and because there are no mechanical transmission components the elimination of backlash.

On the down side, linear motors can be more expensive than other traditional solutions. They also demand better response from controllers such as increased bandwidth and higher update rates. Linear motors also typically cannot produce as much force as some other types of solutions such as ball screws. Another issue may be heating from I2R losses, which may require special cooling considerations.

Choosing the best linear motor for an application involves a number of factors including force and thermal considerations, loads on bearings, and space and clearance considerations.

Early linear motors were cylindrical. In these motors, the forcer is cylindrical in construction and moves up and down a cylindrical bar that houses the magnets. U-channel types of linear motors have two parallel magnet tracks facing each other with the forcer between the plates. The forcer is supported in the magnet track by a bearing system. Lastly there are flat type linear motors, which can be one of three different types: slotless ironless, slotless iron, and slotted iron.

Linear actuator
Linear actuators essentially produce linear motion. Sometimes the primary source of motion is non-linear or rotary, such as a motor. In this case, some other mechanical means such as belts, pulleys, chains or other mechanical components convert the rotary motion to linear motion. Other types of linear actuators produce linear motion on their own, such as through fluid (hydraulic or air) pressure. Common linear actuators include mechanical, electro-mechanical, hydraulic, pneumatic and piezoelectric.

A rotary source linear actuator typically uses an electric motor to provide its input energy. This actuator can use a lead screw to turn the motor’s rotational motion into straight-line motion.

The best fit for the application depends on factors such as required output, size and power requirements. There are several important factors to consider when choosing a linear actuator. First is determining the stroke or length of motion required. Next, how much force is required of the actuator? That is, what is the weight of the object the actuator will need to move? How will the actuator be mounted—horizontally or vertically?

Linear actuators are used in a wide array of both industrial applications such as material handling equipment and robotics as well as everyday consumer applications such as appliances and in computer equipment such as printer heads and scanners.

Linear motion rolling guides
Linear rolling guides are not actuators themselves but the mechanical component that guides a linear motion, which could be a rail or a shaft connected to some type of actuating device. Rolling guides for linear motion applications can help reduce friction in machines. They’re used in various fields ranging from advanced semiconductor manufacturing devices to large machine tools or construction equipment.

Linear rolling guides come in different forms including linear ways and linear roller ways rail guiding systems and ball spline-based shaft guiding systems.

Important considerations for choosing a linear-motion rolling guide include the load, the static load, the stroke and speed as well as the desired precision and accuracy. Pre-loading may also be required depending on the application requirements. Lubrication is another important consideration, as is any method to minimize contamination of the linear guide system from environmental factors such as dust and other contaminants using bellows or special seals.

What is a Motor Drive?

Defining a drive can be a bit tricky. Some drives are wholly incorporated into the controller, so that the profile generation takes place in the controller as well as the torque command for the motor. On the other hand, a drive can also refer to the specific power electronic circuitry needed to drive the motor. Electric motors that drive industrial machines need some way to control motor speed. And at its most basic level, a motor drive controls the speed of the motor.

Some manufacturers refer to a controller and motor together as a drive system. However, from the electrical side of things, the drive is often specifically the electrical components that make up the variable frequency inverter itself. So drives are the interface between the control signals and the motor and include power electronic devices such as SCRs (silicon controlled rectifiers), transistors, and thyristors.

Matching the correct drive to the type of motor in an application is critical for getting the best fit for torque, speed, and efficiency. There are a wide range of drives available depending on the needs of the specific application and motor type. In general though, drive types typically fall into two categories; dc and ac drives.

DC drives control dc motors. A basic dc drive is similar in operation to an ac drive in that the drive controls the speed of the motor. For dc motor control, a common method is a thyristor-based control circuit. These circuits consist of a thyristor bridge circuit that rectifies ac into dc for the motor armature. And varying the voltage to the armature controls the motor’s speed.

AC drives
AC drives control ac motors, such as induction motors. These drives are sometimes known as variable frequency drives or inverters. AC drives convert ac to dc and then using a range of different switching techniques generate variable voltage and frequency outputs to drive the motor.

An adjustable speed drive is a general term used sometimes interchangeably with variable speed drive or variable frequency drive. Again, from an electrical perspective, all of these ultimately refer to the frequency converter circuitry.

An ac motor’s speed is determined by the number of poles and the frequency. Thus, as frequency is adjusted the motor’s speed can be controlled as well. A common way to control frequency is by the use of pulse width modulation (or PWM). A PWM drive sends pulsed inputs to a motor and by modulating the pulse width, making it either narrower or wider, increases or decreases the average dc voltage seen by the motor.

Another powerful kind of drive function is known as regenerative braking or regen braking. This is a way of stopping a motor’s rotation by using the same solid-state components that control the motor’s voltage. The energy generated from braking can be channeled back into the ac mains or into filter capacitors. Advantages of regen drives include the ability to run a motor in either forward or reverse direction without having to physically switch the polarity of the motor leads and without the need for reversing contactors or switches.

What are Integrated Servomotors?

A newer subcategory of servomotor is often called the integrated servomotor. In this type of design, the motor itself is combined with the other essential components of a complete motion control system including the feedback device (generally an encoder), the amplifier or motor drive, a communication port and the motion controller itself.

Such systems are said to offer greater reliability mainly because there are fewer parts to connect together. Also, fewer external connections means less cabling and wiring. Less cabling and wiring reduces costs, as does the fact that the components that one would usually purchase separately such as the motion controller and the drive are integrated into one package.

These integrated servomotors are also designed to be programmed easily and quickly, which can help reduce development times. Communication options range from simple serial communication links such as RS232 or RS485 to more advanced network topologies suited to complex motion control tasks such as CANopen, DeviceNet, or Ethernet protocols.

As with any motor, when selecting an integrated servomotor for an application, the most important step is determining the characteristics of the load. This is why properly calculating the load torque is such an important part of selecting the right motor and designing it into the application. A good rule of thumb to keep in mind is to try and keep the actual operating conditions below the published limits of the motor in order to ensure reliable and long-life operation.

Motor sizing parameters are usually based on the torque curve and moment of inertia of the load. These two factors can help determine the motor’s operating bandwidth. Sets of torque curves depict limits of both continuous and peak torque for the given motor over their full range speed.

There are different types of torque curves, dealing with peak torque and continuous torque as well. Peak torque curves can be derived from dyno testing and represent the point at which peak current limit hardware settings of the drive prevent further torque in an effort to protect drive stage components.

For any mechanical system, if the motor is operating in its optimum range, then the system will be performing at its best. Beyond the motor itself, depending on the specifics of the application it may be necessary to adjust mechanical components such as gear reducers, belts, lead screw pitch or pinion gears in order to achieve optimal system performance.

What is a Servomotor?

Nailing down precisely what a servomotor is can be a tricky exercise, but basically the hallmark of any servomotor is the presence of feedback and closed-loop control. Servomotors are able to provide precise control of torque, speed or position using closed-loop feedback. They also have the ability to operate at zero speed while maintaining enough torque to maintain a load in a given position. Servomotors have several distinct advantages over other types of motors. For starters, they offer more precise control of motion. This means they can accommodate complex motion patterns and profiles more readily. Also, because the level of precision offered is high, the position error is greatly reduced.

All servomotors have essentially three components; an electric motor, a feedback device, and some type of electronic control.

The electric motor itself can be either an ac or a dc motor. Under the dc heading, brushed dc servomotors are generally less expensive than brushless servos, but do require more maintenance due to the brushes needed for motor commutation.

Brushless servomotors are more expensive than brushed dc motors. Generally, these are used in applications requiring higher torque. Brushless dc servomotors are highly reliable and virtually maintenance free. However, the drives for brushless dc servomotors are more complex because the commutation is done electronically rather than mechanically as in the brushed dc motor.

Another way to classify servomotors can be as either single-phase or three-phase motors. Motors of the single-phase variety can range from the simple and inexpensive brushed dc motors mentioned above to voice coils for small micro- and nano-positioning applications.

Servomotors also require a form of feedback, often with the feedback device, such as an encoder, built right into the motor frame. The feedback signal is needed by the control circuitry to close the control loop. It is this closed-loop control that gives servomotors their precise positioning ability.

Lastly, the control circuitry typically involves a motion controller, which generates the motion profile for the motor, and a motor drive which supplies power to the motor based on the commands from the motion controller.

Servomotors are used in many different industrial applications from machine tools, packaging machinery, communications and robotics applications to newer applications such as solar panel control and a broad range of automation control applications. The diversity of applications means that servomotors are designed for general-purpose indoor environments but also for specialized situations requiring them to withstand extreme temperatures and pressures outdoors as well as the special demands of food processing industries in washdown environments.

What are Flexible Couplings?

Couplings join together two shafts as a way of transmitting power from one to the other. It is part of the drivetrain which may include other power transmission components such as lead screws or ball screws, gearboxes, belts and pulleys or chains.

There are two fundamental types of couplings; rigid and flexible. Rigid couplings are generally used in applications requiring precise alignment, whereas flexible couplings can be used where there is a slight amount of misalignment between shafts. So a flexible shaft coupling accommodates misalignment while still transmitting torque. Misalignments can be one of several fundamental types, including lateral, axial, angular, or skewed. The greater the misalignment the less efficient the motor is in generating speed and torque. And misalignment contributes to premature wear including broken shafts, failed bearings and excessive vibration.

Flexible couplings are typically the most compliant of components in mechanical motion systems, making torsional stiffness a critical factor in terms of maintaining positional control over a load.

Types of motion differ in applications as well. For instance, in manufacturing lines, motion may be either continuous or start and stop. With the latter type there is a lot of vibration generated and couplings can help dampen the vibrations and diminish the settling time of the system and improve throughput. In contrast, continuous motion applications give greater weight to torsional strength over damping capabilities. Motion applications that require precise motion control such as in packaging and scanning and inspection call for zero-backlash couplings.

What is a Servo Controller?

More specific types of controllers, such as servo controllers, are used to control servomotors. When dealing with servo systems, it’s important to note that definitions for servomotor, servo system, and servo controllers can differ widely throughout industry. When selecting a servo system for an application, it’s best to ask suppliers what exactly their offerings entail.

A servo controller is the heart of a servo system. A typical servo system consists of a motor, feedback device, and the controller. The control circuitry typically involves a motion controller, which generates the motion profile for the motor, and a motor drive which supplies power to the motor based on the commands from the motion controller. Servo systems are closed-loop systems which have some benefits over open-loop systems including the fact that they improve transient response times, reduce steady state errors and reduce system sensitivity to load parameters.

Servo controllers perform two types of tasks; tracking some commanded input and improving a system’s disturbance rejection. One of the most powerful methods of control is PID control, which stands for proportional-integral-derivative control. PID control is a combination of proportional control, integral control and derivative control. A PID control method works on the error signal which is the difference between a commanded value and the actual value of an output variable, and driving the error to zero. The proportional value can be thought of as a simple gain value. The integral value integrates the error over a period of time and helps to drive the error to zero. The derivative value helps to stabilize a system that uses an integral and proportional term only.

There are a few important factors to consider when selecting a servo controller for an application. The first thing is knowing which type of motor is to be controlled. Is the servomotor an ac or dc motor? If dc, is it brushless or brushed? This will help in determining the kind of commutation the motor needs and if the controller can accommodate it.

How many axes of motion does the application have? Is it a single axis of control or are there multiple axes? Servo controllers are available to control simple single axis applications as well as more complex motion such as robotics applications involving multiple axes.

Next, how many channels of I/O are needed? Are special input types needed beyond inputs for feedback signals such as speed and position? Be sure that the controller can accommodate the appropriate feedback device, such as incremental encoder signals, resolver signals, SSI, Hall sensor signals, or tachometer inputs.

Another important factor that is sometimes overlooked is the controller set up. Is the controller easy to set up and program? Is programming done via keypad or can it be programmed from a computer screen? Also consider the available communication links. Are there basic RS232 or RS485 links? Does the controller include bus interfaces for common networks such as CAN, DeviceNet, Sercos or Ethernet?

Motion controller

Motion controllers are the brains of any motion control system. In feedback-based systems, they take an input command from the user, compare it with a feedback signal from the motor, and take corrective action to bring the output (or actual position) and input (or desired position) in line with one another, ideally with little or no error.

A motion controller also creates the trajectories that the motors follow in order to meet the desired commands. Also called motion profiles, a profile is a sequence of position commands vs. time. This tells the motor where to position the load and how fast it must do so. The motion controller uses the trajectories it creates to generate the proper torque commands. These torque commands are then sent to the drive, which powers the motor and creates motion.

Because of the large amount of signal processing required for these actions, motion controllers typically use digital signal processers (or DSPs) for this task. DSPs are specifically designed to perform mathematical operations quickly and efficiently, and can handle the algorithmic processing better than standard microcontrollers which aren’t designed to handle large amounts of mathematical processing.

There are a number of common motion profiles including trapezoidal, ramp, triangular, and complex polynomial profiles. Each of them is used in certain conditions and situations where that type of motion is desired. For instance, a trapezoidal profile is characterized by constant velocity and acceleration and a graph of the velocity vs. time profile is in the shape of a trapezoid.

Motion controllers also use some of the basic control laws to implement motion. The simplest of these is called proportional (P) control, which represents a constant integer gain. This is the simplest type of control to implement. From P controllers, one can add either a derivative gain (known as D) or an integral gain (or I). The combination of these three, known as PID, represents one of the most common and most powerful types of control algorithms.

Practically speaking, motion controllers come in a variety of sizes and types. In general, motion controllers fall into one of three categories; stand-alone, PC-based, and individual microcontrollers.

Stand-alone controllers are entire systems typically mounted in one physical enclosure that includes all of the necessary electronics, power supply, and external connections. These types of controllers can be built into a machine and are dedicated to one motion control application that could involve controlling a single axis of motion or multiple axes.

PC-based controllers are mounted onto the motherboard of a basic PC or industrial PC. These types of controllers are mainly processing boards that may generate and execute motion profiles. The advantage of PC-based controllers is that they provide a ready-made graphical user interface that makes programming and tuning the control much easier.

Lastly, there are individual microcontrollers. These are individual ICs that are often designed onto a printed circuit board along with feedback inputs and outputs to drivers to control a motor. While these controllers are relatively inexpensive and have the advantage of giving designers chip-level access to their systems, the drawback is that they require good programming skills to configure and implement.

Incremental encoders

Incremental encoders, like absolute encoders, are used to track motion as well as to determine speed and position. Incremental encoders generally supply square-wave signals in two channels, A and B, which are offset by 90 degrees, or out-of-phase by 90 degrees. This helps in determining the direction of rotation.

The output signals of an incremental encoder only have information on relative position not absolute position like an absolute encoder. In order for the encoder to provide any useful position information, the position of the encoder has to be referenced in some way, traditionally using an index pulse. So the incremental encoder sends incremental position changes to electronic circuits that perform the counting function.

On start-up, the encoder will home in on a known, fixed position, which serves as a fixed reference point going forward. This fixed position can be either fixed by a magnetic point or strip of mechanically by a limit switch.

One traditional limitation of an incremental encoder is that the number of pulses counted is stored in an external or buffer counter which can be lost if there is an interruption of power. For instance, if a machine with an encoder is turned off, the encoder will not know its position when switched on again. The encoder has to perform a homing routing in order to know its exact position, forcing the motor to move until a home limit switch is activated. Then, a counter or buffer will be zeroed and the system will determine where it is relative to fixed positional points. One way around this issue of loss of power is to use a battery backup system. Such a solution ensures that the memory is backed up and can store the count information and provide an absolute count once power is restored.

Standard Quadrature A and B signals used in incremental encoders are shown in the graph above. Electronic circuitry interprets the raw data to determine position as well as the direction of rotation.

Torque limiter

Torque limiters protect equipment or loads from excessive torque. In essence, they are used to shut down a machine and dissipate any rotational energy without causing damage to the machine. Often, systems operating at low speeds can develop a large quantity of torque. In the event of a malfunction, this excess torque can damage machine components such as gearing, couplings, and motor and/or drive shafts. A torque limiter will prevent damage by limiting the amount of torque to some pre-set level.

Some consider mechanical torque limiters outdated because there are other ways to control torque overload, most notably via electronic current limitation of the motor. While this may work in some cases, as machinery becomes more dynamic, the inertia of moving parts becomes more critical. So, for instance, it’s possible to abruptly decelerate a rotating mass through unintentional blockage or the application of a dynamic braking system at a rate faster than the drive would normally accelerate.

This can create torque overload through the reflected inertia which is completely independent of the electronic system and so can easily exceed the peak torque rating of the motor. While older and bulkier designs may be out of the question, these modern mechanical torque limiters offer a high level of sensitivity and accuracy, with increasingly smaller impact on the size, mass, balance, and power consumption of the drive system.

There are fundamentally two types of torque limiter technologies, the disconnect type and the slip type. Disconnect torque limiters, as the name implies, physically disconnect the drive from the load. Several methods exist for the disconnecting process. The shear pin method actually destroys the pin joining the load with the drive. Another common method is via magnetic disconnection using permanent magnets. The common feature of disconnect type torque limiters is that they permanently separate the drive and driven shaft and require a manual re-engagement.

Slip type torque limiters work by letting the drive shaft run faster than the driven shaft. It effectively “slips” at some preset torque setting and reengages when the torque falls below the limit.

The most important factor in selecting a torque limiter is determining the proper torque rating, which will help determine the proper torque limiter size. Torque limiters are ideally installed as physically close to the point of impact or overload as possible in order to enhance sensitivity.

Torque limiters are often used in conjunction with a proximity sensor to detect the movement of an external ring around the disengaging safety clutch, and then trigger an e-stop condition in the machine. Free wheeling safety clutches will permanently separate the drive and driven shaft hubs of the coupling, requiring a manual re-engagement. This cuts back significantly on potential wear between the two halves of the torque limiter as they ratchet against each other.

Stepper motors

One of the most common motors used in motion control applications is the stepper motor. These motors are used mostly in positioning applications and have the advantage of being able to be very accurately controlled for the most precise positioning applications, down to fractions of a degree without the use of feedback devices such as encoders or resolvers. They are operated in open-loop (not closed-loop), without the need for tuning parameters as in closed-loop servo systems.

Steppers are generally classified by the number of allowable steps they can be commanded to move. For instance, a 1.8 degree step motor is capable of 200 steps/revolution (1.8 x 200 = 360 degrees, or one full revolution) in full-step mode. If operated in half-step mode, each step becomes 0.9 degrees and the motor can then turn 400 steps/revolution. Another mode called microstepping subdivides the degrees per step even further, allowing for extremely precise movements.

There are several different stepper motor technologies including permanent magnet motors, variable reluctance, and hybrid types. The principle of operation for stepper motors is fairly straightforward. Traditional variable reluctance stepper motors have a large number of electromagnets arranged around a central gear-shaped piece of iron. When any individual electromagnet is energized, the geared iron tooth closest to that electromagnet will align with it. This makes them slightly offset from the next electromagnet so when it is turned on and the other switched off, the gear moves slightly to realign. This continues with the energizing and de-energizing of individual electromagnets, thus creating the individual steps of motion.

Hybrid stepper motors are more expensive than permanent magnet stepper motors but provide better performance with respect to step resolution, torque and speed. Hybrid steppers combine the best features of both the permanent magnet and variable reluctance type stepper motors. The rotor is multi-toothed like the variable reluctance motor and contains an axially magnetized concentric magnet around its shaft. The teeth on the rotor provide a path to help guide the magnetic flux to preferred locations in the airgap. This further increases the detent, holding and dynamic torque characteristics of the motor when compared with both the variable reluctance and permanent magnet motor.

Stepper motors are relatively inexpensive and can be run open loop, requiring no feedback devices. Also, because the speed is proportional to the frequency of the input pulses, a wide range of speeds is attainable. However, while stepper motors are capable of producing high torque at low speeds, they generally are well suited for lower power applications not for applications requiring lots of torque to move heavier loads. They are best for applications requiring the control of rotation angle, speed, and position.

A few drawbacks are that not properly controlling the motor can produce undesired resonance in the system. Also, stepper motors are generally not easy to operate at extremely high speeds. And as the motor speed increases, torque decreases.

For two-phase stepper motors, there are two basic kinds of winding structures; unipolor and bipolar. A unipolar arrangement uses 6 wires but current can only flow in one direction. These types of motors also require a unipolar driver. A bipolar winding uses 4 wires and current can flow in 2 directions and it requires a bipolar drive. Bipolar motors are generally more efficient and can provide more torque than unipolar models, although they can heat up faster than unipolar motors.

A stepper motor’s low-speed torque varies directly with current. How quickly the torque falls off at higher speeds depends on a number of factors such as the winding inductance and drive circuitry including the drive voltage. Steppers are generally sized according to torque curves, which are typically specified by the manufacturer.

Bellows Couplings

One form of flexible coupling with very low and near zero-backlash is the bellows coupling. The key benefits of bellows couplings include misalignment compensation and precise transmission of velocity, angular positioning and torque. Bellows couplings are known for their exceptional torsional rigidity, which allows for flexibility in dealing with axial, angular and parallel shaft misalignment.

Bellows couplings are typically made from a stainless steel tube hydroformed to create deep corrugations that make them flexible across axial, angular, and parallel shaft misalignments. The bellows absorbs any slight misalignments between the mounting surfaces of two components.

When coupling shafts, bellows couplings absorb slight misalignments from perpendicularity and concentricity tolerances between the mounting surfaces of the two connected components. Bellows couplings tend to have the highest torsional stiffness of any servo motor coupling, and so are used in applications requiring high precision positioning.

Selecting the right bellows coupling for an application starts with knowing the torque involved. For instance, it’s helpful to know the peak torque capacity of the servo motor. This value, multiplied by the gear reduction ratio and a safety factor of 1.5, gives the minimal torque calculation.

In most cases, couplings are rated according to the maximum peak torque to be transmitted. The peak torque should not exceed the coupling’s rated torque. And by rated torque is meant the torque that is continuously transmittable within the specified acceptable speed and misalignment ranges.

Flat Cabling

An alternative to flexible cabling in some motion applications are flat cables. These cables can incorporate any variety of power, signal, and video conductors in a single compact cable. In addition to every type of electrical conductor, flat cables can also include tubing for air or liquids, and even fiber optics. By incorporating all these elements into a single flat cable, motion equipment can be significantly smaller, quieter, and more energy efficient.

Most industrial automation equipment today operates continuously, with robots that execute rigorous motions repeatedly, sometimes thousands of times a day. These applications stress not only the moving parts of the machine, but also the electrical cabling. All too often, designers spend more time sizing components like motors, actuators, and controllers and give little thought to the cabling needed. The result is that if standard cabling is used in these applications, the cables, not being designed to flex continuously, can’t handle the rigors of the application and can result in costly premature failures. Flat cables are best for continuous flexing. Their wire conductors can individually flex in a single plane, which provides optimum flex life.

Some motion control systems may encase separate wires, cables, and tubes in a carrier track to contain and manage the separate elements and to constrain their motion. These tracks are usually made of plastic and they usually have a rather large bend radius due to their size and the rolling link element design. These tracks do not add performance to the motion device or machine, as they are simply cable management devices. Cable tracks can add bulk, mass and inertia to the motion system, and moving this extra mass requires more energy. While certain motion systems such as robotic applications may require this type of cabling design, other designs may not and can use standard flat cabling instead to save weight and cost.

Some flat cable manufacturers offer cables with silicone jacketing. These types of flat cables are durable and need no external armor for protection. They resist abrasion and will even self-heal minor nicks. Silicone encapsulation also provides protection against oils, acids, ozone, steam, and extreme temperatures.

When specifying flat cables in motion control applications, four considerations are key; the bend radius, life cycles under constant flexing, any packaging constraints, and environmental factors.

The bend radius ultimately depends on the gauge of the wire and the kind of conductors used in the cable. As a general rule, the finer the conductor gauge the smaller the allowable bend radius. Flat cables with PTFE jackets can have a larger bend radius than cables with silicone jacketing, given that each cable contains the same conductors.

For cabling used in flexing applications, two key factors are the wire conductors and the cable jacket. With continuous flexing, conductors containing multiple strands of fine-gauge wire generally last the longest.

Chief environmental factors include exposure to harsh conditions such as temperature and humidity, and resistance to environmental contaminants such as any oil or corrosive materials.

Machine Controller

In the most general sense, a controller receives some type of input and produces outputs for some device, most commonly an electric motor. More specifically, machine control, unlike a more specific type of controller such as a motion controller, refers to the control of an entire stand-alone machine such as a CNC machine, packaging machine, or even a vending machine.

The machine controller’s primary operations include scanning I/O, updating output and process control. After an initialization phase, the controller will continuously read inputs, calculate control parameters for the machine process using application-specific logic based on the input data, and then update outputs to the machine. If the controller is turned off, some shutdown process may be completed.

The central part of a machine controller is the controller itself, which can take on several forms. For single machine control, a programmable logic controller (PLC) or a programmable automation controller (PAC) is usually sufficient to handle the job. PLCs are usually programmed using ladder logic or sequential function charts. The controller receives various sensor data, processes this information and executes controls via some combination of digital and/or analog I/O signals to turn on or off processes, actuate or stop movement, and take user or environmental input and make decisions based on these inputs. Machine controllers will generally work together with some type of human-machine interface (HMI). These can be either integrated with the controller as one piece or can be stand-alone units that communicate with the controller.

More recently, machine control has seen a move to PACs because they can offer better performance and a wider range of functions than traditional PLCs. For instance, PACs can support high-speed data acquisition and processing, as well as motion control and vision functions.

In order to take advantage of all the features and capabilities of a PAC, the application code must be well designed, balancing and coordinating various controller processes such as I/O, process control logic, communication to an HMI unit and other tasks.

There are a number of considerations to keep in mind when selecting a machine controller. One of the most important is the number and type (i.e. analog or digital) of I/O the controller will have to handle. Also, do the speed requirements of the machine match up with the controller’s capabilities? For instance, some machine controllers may be tasked with closing servo loops and thus must be capable of handling such a task.

Another consideration is the type of communication link needed. The machine may have special demands or may be wired to accommodate a specific networking protocol, so ensure that the controller can communicate with the machine. Related to the communication link is the programming environment. Is the controller simple to program? Can programs be edited quickly and easily? Lastly, consider any environmental factors in which the machine will have to operate such as shock and vibration, extreme temperatures, and moisture or humidity.

Absolute encoders

Encoders can be either absolute or incremental. Absolute encoders have a unique code for each shaft position. Or in other words, every position of an absolute encoder is distinctive. The absolute encoder interprets a system of coded tracks to create position information where no two positions are identical. Another feature is that absolute encoders do not lose position whenever power is switched off. Since each position is distinctive, the verification of true position is available as soon as power is switched on. It is not important to initialize the system by going back to a home base for a reference.

Absolute encoders can be either single-turn or multi-turn. Single-turn encoders are well suited to short travel motion control applications where position verification is needed within a single turn of the encoder shaft. Multi-turn encoders, on the other hand, are better for applications that involve complex or lengthy positioning requirements.

Absolute encoders have a number of advantages. First is the non-volatility of memory. An absolute encoder works as a non-volatile position verification device. True position is not lost if power is lost or the system moves while power is switched off. A continuous reading of position is not needed. This is specifically useful in those applications, such as satellite-tracking antennas, where position verification is key.

Absolute encoders also provide programming flexibility. By removing the need for system homing, the encoders can be controlled to give positioning programs based on setting up reference from point-to-point, rather than from a home position. Additionally, a microprocessor interface module allows for programming various operating parameters, such as resolution.

Safety is another benefit. In some applications where a loss of position could lead to operator injury or machine damage, an absolute encoder automatically provides position verification when the power is switched on.

Absolute encoders also have good immunity to electrical noise. The device determines position by frequently reading a coded signal. Stray pulses from electrical noise will not build up and accurate position is presented again on the next reading.

Roller chains

In any motion control system, the object is ultimately to move some kind of load. The component in the motion system that converts electrical energy into mechanical energy is the motor. But the task doesn’t end there. A motor’s output shaft has to connect somehow to whatever the load is.

This final connection can take many forms. Some of the most efficient ways to connect with the load are so-called direct drive methods, where the motor is directly coupled to the load. When this isn’t feasible, various intermediary methods are available to couple the motor to the load. One of these is a roller chain.

Roller chains have the benefit of being a fairly straightforward and simple method of transmission of mechanical energy. Roller chains are constructed like a typical chain link structure; that is, a series of cylindrical rollers connected by links. A rotating sprocket which is connected to the motor moves the chain. The other end of the chain can then be connected to some part of the load.

On the down side, chains wear out over time and when they do the pitch increases, making them looser and more compliant, which can add instability in the form of “play” into the system. Also, chains need to be lubricated to keep them operating effectively.

The primary factors that limit chain life are corrosion, wear, and fatigue. However, following a few simple guidelines can help extend the life of roller chains. For starters, in order to maximize useful life, chains should be properly lubricated to minimize wear. Also, corrosion can accelerate the effects of wear and fatigue. To combat this, make sure that the chain is protected. A properly lubricated chain can minimize exposure to the environment and extend product life.

Also, some manufacturers offer options to improve fatigue resistance including specially manufactured components such as hardened pins and rivets as well as optimized chain dimensions for given applications. However, the general rule for chains is that when a chain becomes between 1.5 and 2% longer than the original length, it begins to ride up the sprocket teeth. This is the point at which sprocket and chain wear accelerates.

Some manufacturers offer corrosion-resistant chains. These can be made from one of several types of materials including stainless steel, nickel-plated chains, titanium, or stainless steel chains combined with special polymers.

AC motors

Motors can be classified as either ac – alternating current, or dc – direct current, motors. An ac motor, like any electric motor, converts electrical energy to mechanical energy. AC motors take as their input an ac current, but differ from dc motors in that there is no commutation involved, and can be single or multi-phase.

Because ac motors have no commutators or brushes, they require less maintenance than brushed dc motors.

With dc motors, control is done by varying voltage and current, while on ac motors the voltage and frequency (along with the number of magnetic poles) are used to control the motor.

There is one common way to break down ac motors that is based on the magnetic principle that produces rotation. So there are two fundamental types of ac motors; induction motors and synchronous motors.

In induction motors, the key idea is the rotating magnetic field. The most common source of this in ac motors is the squirrel cage configuration. This is essentially two rings, one at each end of the motor, with bars of aluminum or copper connecting the two ends.

Induction motors have properties that make them especially well suited to a number of industrial as well as home appliance applications. For starters, they are simple and rugged motors that are easy to maintain. They also run at constant speed across a wide range of load settings, from zero to full-load. The only drawback is that induction motors are generally not amenable to speed control, although the availability of sophisticated variable-frequency drives means that even induction motors, usually three-phase induction motors, can now be speed controlled as well.

The other type of ac motor is a synchronous motor. Synchronous motors are so named because they run synchronously with whatever the frequency of the source is. The motor speed is fixed and doesn’t change with changes to the load or voltage. These motors are primarily used where the requirement is precise and constant speed. Most synchronous motors are used in heavy industrial applications, with horsepower ratings ranging from the low hundreds up to thousands of hp.

Synchronous motors can be used in motion control applications, but there are some down sides to using these motors. Because of the rotor size, the motor’s response in incrementing applications is typically not good. Also, because acceleration of inertial loads may not be as high as other motor types, these motors may operate at irregular speeds and produce undesirable noise. And generally, synchronous motors are larger and more costly than other motors with the same horsepower rating.

Brushless dc motors

A brushless dc (BLDC) motor is essentially a dc motor without the mechanical commutation of the brushed dc motor. BLDC motors are powered by direct current and have electronic commutation systems instead of the mechanical brushes and commutators used in brushed dc motors.

All dc motors generate a magnetic field, either via electromagnetic windings or permanent magnets. An armature, which is often a coil of wires, is placed between the north and south poles of a magnet. When current flows through the armature, the field produced by the armature interacts with the magnetic field from the magnets and eventually generates a torque and thereby motion.

For motion control applications, the most common dc motor types are the basic brushed dc motor, brushless motors, and permanent magnet motors.

In a brushed dc motor, the magnet acts as the stator. The armature is integrated onto the rotor and a commutator switches the current flow. The commutator’s function is to transfer current from a fixed point to the rotating shaft. Brushed dc motors generate torque straight from the dc power supplied to the motor by using internal commutation, fixed permanent magnets, and rotating electromagnets.

Brushed dc motors have the advantage of generally low initial cost and simple control of the motor speed. However, there are some drawbacks. At certain periods during the dc motor rotation, the commutator must reverse the current, causing reduced motor life due to arcing and friction. Consequently, brushed dc motors require more maintenance such as frequently replacing the springs and brushes which carry the electrical current, as well as replacing or cleaning the commutator. These components are important for transferring electrical power from outside the motor to the spinning coil windings of the rotor inside the motor.

BLDC motors, on the other hand, do away with mechanical commutation in favor of electronic commutation, which eliminates the mechanical wear and tear involved with brushed dc motors. In BLDC motors, the permanent magnet is housed in the rotor and the coils are placed in the stator. The coil windings produce a rotating magnetic field because they’re separated from each other electrically, which enables them to be turned on and off. The BLDC’s commutator does not bring the current to the rotor. Instead, the rotor’s permanent magnet field trails the rotating stator field, producing the rotor field.

For successful commutation, it’s important to have precise rotor position data, which is often achieved via magnetic sensing with a Hall Effect sensor, which also allows for tracking of speed and torque.

BLDC motors have quite a few advantages over their brushed counterparts. Compared to brushed dc motors, BLDC motors are more efficient due mainly to the elimination of the friction from the brushes. They’re also more reliable and typically have longer life spans as well. Getting rid of the brushes also means a decrease in EMI (electromagnetic interference) noise and no sparking from the brushes making contact with the commutator.

Some servomotor systems use brushless dc motors instead of other types of motors (either a brushed dc motor or an ac motor such as an induction motor.)

BLDC motors are used in everything from low-power applications such as consumer products to high power applications in electric vehicles and industrial equipment.

Gearing

Gearmotors
Gearmotors are an all-in-one combination of an electric motor and one or more pairs of gears (which is also known as a gearbox). A gearmotor simplifies combining a motor with a gear reducer system.

Planetary gears
Planetary gears consist of one or more outer gears, or planet gears, revolving about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier that may rotate relative to the sun gear. These systems often use an outer ring gear or annulus, which meshes with the planet gears.

The gear ratio in this type of system is not obvious, particularly because there are several ways in which an input rotation can be converted into an output rotation.

Typically, one of these three gear wheels is held stationary; one is an input providing power to the system, while another is an output, receiving power from the system. The ratio of input rotation to output rotation is dependent upon the number of teeth in each gear, and upon which component is held stationary.

Planetary gears offer several advantages over parallel axis gears. These include high power density, the ability to achieve a large reduction in a small volume, multiple kinematic combinations, pure torsional reactions, and coaxial shafting. The disadvantages include high bearing loads, inaccessibility, and design complexity.

In a planetary gearbox arrangement, one advantage is power transmission efficiency, which is typically 3% per stage. Thus, a high proportion of the energy transmitted through the gearbox is used rather than wasted on mechanical losses inside the gearbox.

Planetary gearbox arrangements distribute load efficiently too. The transmitted load is shared between multiple planets, which greatly increases torque density. The more planets in the system, the greater load ability and the higher the torque density. This arrangement is also very stable due to the even distribution of mass and increased rotational stiffness.

Strain wave gearing
Strain wave gearing is an approach to speed reduction using metal elasticity (deflection) of the gear to reduce speed. (Strain wave gearing is also known as Harmonic drives–a registered trademark term of Harmonic Drive Systems Inc.) The benefits of using this approach include zero backlash, high torque, compact size, and positional accuracy.

A strain wave gear is comprised of three components: Wave Generator, Flexspline, and Circular Spline.

The Wave Generator is an assembly of a bearing and a steel disk called a Wave Generator plug. The outer surface of the Wave Generator plug has an elliptical shape machined to a precise specification. A specially designed ball bearing is pressed around this bearing plug causing the bearing to conform to the same elliptical shape of the Wave Generator plug. The Wave Generator is typically used as the input member, usually attached to a servomotor.

Strain wave gearing uses the metal elasticity of gears to reduce speed. The teeth of the Flexspine and Circular Spline are engaged near the major axis of the ellipse and disengage at the minor axis of the ellipse. The elastic radial deformation acts like a very stiff spring to compensate for space between the teeth that would otherwise increase backlash.

The Flexspline is a thin-walled steel cup. Its geometry allows the walls of the cup to be radically compliant, yet remain torsionally stiff since the cup has a large diameter. Gear teeth are machined into the outer surface near the open end of the cup (near the “brim”). The Flexspline is usually the output member of the mechanism.

The cup has a rigid boss at one end to provide a rugged mounting surface. The Wave Generator is inserted inside the Flexspline so that the bearing is at the same axial location as the Flexspline teeth. The Flexspline wall near the brim of the cup conforms to the same elliptical shape of the bearing. This causes the teeth on the outer surface of the Flexspline to conform to this elliptical shape. Effectively, the Flexspline now has an elliptical gear pitch diameter on its outer surface.

The Circular Spline is a rigid circular steel ring with teeth on the inside diameter. It is usually attached to the housing and does not rotate. Its teeth mesh with those of the Flexspline. The tooth pattern of the Flexspline engages the tooth profile of the Circular Spline (circular) along the major axis of the ellipse. This engagement is like an ellipse inscribed concentrically within a circle. Mathematically, an inscribed ellipse will contact a circle at two points. However, the gear teeth have a finite height. So there are actually two regions (instead of two points) of tooth engagement. Roughly 30% of the teeth are engaged at all times.

The pressure angle of the gear teeth transforms the output torque’s tangential force into a radial force acting on the Wave Generator bearing. The teeth of the Flexspline and Circular Spline are engaged near the major axis of the ellipse, and disengaged at the minor axis of the ellipse.

The Flexspline has two less teeth than the Circular Spline. Thus, every time the Wave Generator rotates one revolution, the Flexspline and Circular Spline shift by two teeth. The gear ratio is calculated by:

Number of Flexspline Teeth / (Number of Flexspline Teeth – Number of Circular Spline Teeth)

The tooth engagement motion (kinematics) of the strain wave gear is different than that of planetary or spur gearing. The teeth engage in a manner that allows up to 30% of the teeth (60 teeth for a 100:1 gear ratio) to be engaged at all times. This contrasts with maybe 6 teeth for a planetary gear, and 1 or 2 teeth for a spur gear.

In addition, the kinematics enable the gear teeth to engage on both sides of the tooth flank. Since backlash is defined as the difference between the tooth space and tooth width, this difference is zero in strain wave gearing.

As part of the design, the gearteeth of the Flexspline are preloaded against those of the Circular Spline at the major axis of the ellipse. They are preloaded such that the stresses are well below the material’s endurance limit.

In the gear as the gear teeth wear, this elastic radial deformation acts like a very stiff spring to compensate for space between the teeth that would otherwise cause an increase in backlash. This allows the performance to remain constant over the life of the gear.

Strain wave gearing offers high torque/weight and torque/volume ratios. The lightweight construction and single stage gear ratios of up to 160:1 allows the gears to be used in applications requiring minimum weight or volume. Small motors can exploit the large mechanical advantage of a 160:1 gear ratio to create a compact, lightweight, and low cost package.

A new tooth profile for strain wave gearing has become available in the last few years. This “S” tooth design allows more gear teeth to engage. The effect is to double torsional stiffness, double peak torque ratings, and lengthen operational life.

The “S” tooth form does not use the involute curve of a tooth. Instead, it uses a series of pure convex and concave circular arcs that match the loci of engagement points dictated by theoretical and CAD analysis.

The increased root filet radius makes the “S” tooth much stronger than an involute curve gear tooth. It will resist higher bending (tension) loads while maintaining a safe stress margin.

Linear motion bearings

This class of bearings generally uses a pad, bushing, or roller system to carry a load on a rail that need not be a straight line. The rail can be most any length, although that dimension is limited by the actuator. The durability of the bearing is determined by the load and required speed. Furthermore, rails can generally be any profile – simple flat surfaces, round polished rods, or complex profiles with polished ground surfaces on which balls or cylindrical rollers can ride. Hard (Rockwell 60) and ground bearing surfaces work best. Further classifications might be by size. For instance, miniature linear bearings might work well moving a biologic slide sample just a few millimeters beneath a microscope lens while industrial-bearings on injection molding machines carry tooling of several tons.

Bushings provide possibly the simplest linear bearing. These thin-walled cylinders can be injection molded of proprietary polymers infused with a lubricant. An oil-infused bronze design, also cylindrical, rides on a polished round rod. This linear-bearing classification is often referred to as slides.

Purpose-built linear bearings are available for frequently encountered tasks, such as pull-out equipment drawers or storable work surfaces. These usually light-duty devices let polymer wheels or ball bearings ride on stamped or rolled steel rails. Telescoping arrangements allow designing pull-out equipment drawers into cantilevered positions while supporting up to 50 lb or more for maintenance.

Heavier loads are carried by linear guides that use re-circulating ball or roller bearings in rectangular mounting pads or slide units. These are so constructed that a loop of balls or cylindrical rollers cycles into and out of a load area along shafts at most any required load. Two, three, and four rails can work in unison to carry loads that exceed the rating of one rail.

The ball spline is a variation on this design. In it, the sliding unit is a cylinder with at least three and up to five circuits of re-circulating balls. There are dozens of cylindrical shapes to choose from. For instance, miniature designs are intended for instrumentation and pillow blocks are available when the rod must move while the rolling elements remain stationary. Some manufacturers boast of maintenance-free designs, which can mean several years between scheduled maintenance.

Long lengths can make use of a design in which the profile on a bearing-mounted wheel carries a V-shape that rides in a mating V on a rail edge. Such a design is less affected by debris and is said to operate without bellows and covers.

Nonlinear-linear bearings are also possible with permutations to the designs above. For example, so-called rectangular circuits have generously rounded corners, and oval rail circuits are possible by letting two sets of wheels or rollers ride in a groove on either side of the rail. Actuation can be provided by a timing belt mounted on the inside of the track.

Accessories for linear bearings include wipers that sweep a rail in front of a slide unit to keep dirt and debris from damaging rolling elements. Seals provide a similar function but are more intended to keep lubricant from seeping out of the bearing area.

A brief design checklist of considerations for a device requiring linear-motion bearings would include required rigidity, load, moment loads, and needed accuracy. Designers might also consider whether or not regular maintenance will be available, the possibility of vibration and how it could affect operations, and noise requirements. Of course, design is more complex than this. Manufacturers are likely to offer a range of shaft support shapes and materials, shaft material options such as particular carbon steels versus stainless, or even tubular shafts.

Cable Carriers

Motion control systems can vary from simple, straightforward single-axis direct-drive systems with little wiring to large and complex multi-axis robotic systems with a hornet’s nest of cables. This is usually where cabling, which was an afterthought, now takes center stage.

Especially where there are lots of cables and wiring, cable management becomes an issue. A simple form of cable management uses twist-tie type bundlers that tie together groups of wires and cables. These are low cost and easy to use. The problem is that with more and more cabling, they become impractical. Also, if the wiring and cabling have to be suspended, bundling them together may pose weight problems which cause sagging and put undue strain on the cables.

Using cable carriers is another option. Cable carriers are essentially structures designed to house cables. The structures themselves can be made of many materials such as plastic, steel, or a metal alloy. Cable carriers are used to protect cables and hoses on moving machinery. They prevent tangling and increase safety by not having cables susceptible to getting caught in moving parts of a machine. Applications for cable carriers can range from machine tools and robotics to cleanroom applications and large industrial equipment like cranes and other construction machinery.

Carriers can house a large volume of cables and wires and support the weight of them all without sagging or putting stress on the cabling. They also make managing and routing the cables through a machine or factory much simpler and provide easy access for troubleshooting or maintenance as well.

Selecting the right kind of cable carrier for an application starts with a few simple guidelines. The most important points to consider are the specifics of the application. These include the length of travel, the number of cables or hoses, the size and weight of the cables, the required speed and acceleration and environmental factors such as exposure to any debris, excessive heat or chemicals. Knowing the weight of the cables ensures that the carrier won’t fail by snapping in two.

Cable carrier styles can be either open or closed. Open varieties allow for easy access to the cables and visible access as well, whereas closed carriers seal off the cables from the environment to protect from environmental contaminants such as metal filings.

Environmental conditions play a large part in selecting a cable carrier. If the application is in a dirty or contaminated area, an enclosed carrier is the best choice. An open carrier is lightweight and makes inspecting and replacing cables easier.

Another important consideration is the bend radius of the cable carrier. Bend radius is measured from the center of the curve loop to the center of the pivot pin on the side link. A larger bend radius means less stress on the cable and a longer service life.

Ball Screws

Ball screws are mechanical devices that convert rotational motion to linear motion with a minimal amount of friction. There are several components to a ball screw including a nut and a screw with helical grooves and balls that roll between the nut, the screw and the grooves, while the screw or nut is rotating. Balls are routed into the ball return system of the nut and travel in a continuous path to the ball nut’s opposite end.

Ball screws are used in an array of applications ranging from low accuracy transport guides to exceptionally high accuracy precision grade screws. They’re also used in robots, machine tools and precision assembly devices.

Ball screws are usually classified according to factors such as axial play and preload, lead accuracy and life/load relationship. Axial play is the degree to which a ball nut can be moved in the screw axis direction without any rotation of either nut or screw, while preload is usually considered as the negative axial play. The process of preloading removes backlash and increases stiffness.

Lead accuracy refers to the degree to which the shaft’s rotational movements are translated into the run’s proportional linear movement. With lead accuracy and axial play primarily determined by the manufacturing method of the ball screw shaft, high lead accuracy and zero or negative axial play is generally associated with relatively higher cost and precision ground ball screws, while lower lead accuracy and positive axial play with lower cost rolled ball screws. Fabricated by rolling or other means, ball screw shafts yield a less precise but mechanically efficient and less expensive ball screw.

Perhaps the biggest benefit of a ball screw in general is that it has high efficiencies that can be well over 90%. There are also minimum thermal effects and they can be easily preloaded to eliminate backlash. They also offer smoother movement over the full travel range.

Compared to other alternatives, a ball screw’s low friction generates high mechanical efficiency. Unlike comparable Acme lead screws, which are only 50 percent efficient, a typical ball screw offers 90 percent efficiency. The higher cost of ball screws can be offset by decreased power requirements for similar net performance.

One drawback to ball screws is that they require higher levels of lubrication. Ball screws should always be properly lubricated. Lubrication prevents corrosion, reduces friction, extends operating life and leads to more efficient operation.

However, contaminated lubrication can increase friction. Ball screws can fail if the balls travel over metal chips or dirt in the ball thread raceway. Using lubricants recommended by machine tool manufacturers can help prevent this. Also, consider using telescopic covers or bellows if ball screws are used in environments with a lot of contaminants. Aside from being bulkier, ball screws are more prone to damage when installed compared to conventional lead screws.

When selecting a ball screw, a few parameters are essential. Knowing the expected load, the operating speed needed, as well as the positional accuracy are a good start to sizing the right ball screw for the application. This information can help determine the ball screw diameter and lead and help make further decisions based on expected life, any special mounting configurations and assembly considerations as well as environmental conditions.

DC Motors

A direct current – dc  motor is an electric machine that converts electrical energy to mechanical energy. DC motors are one of two general types of motors, the other being the alternating current – ac motor. DC motors have a few basic components including the commutator, armature, a stator and a rotor.

All dc motors generate a magnetic field, either via electromagnetic windings or permanent magnets. An armature, which is often a coil of wires, is placed between the north and south poles of a magnet. When current flows through the armature, the field produced by the armature interacts with the magnetic field from the magnets and eventually generates a torque and thereby motion. Part of the simplicity and attractiveness of dc motors is that they operate at a constant speed for a fixed voltage.

DC motors are available in a few basic configurations; the basic brushed dc motor, brushless motor, permanent magnet motor and wound-field motors.

In a brushed dc motor, the magnet acts as the stator. The armature is integrated onto the rotor and a commutator switches the current flow. The commutator’s function is to transfer current from a fixed point to the rotating shaft. Brushed dc motors generate torque straight from the dc power supplied to the motor by using internal commutation, fixed permanent magnets, and rotating electromagnets.

Brushed dc motors have the advantage of generally low initial cost and simple control of the motor speed. However, there are some drawbacks. At certain periods during the dc motor rotation, the commutator must reverse the current, causing reduced motor life due to arcing and friction. Consequently, brushed dc motors require more maintenance such as frequently replacing the springs and brushes which carry the electrical current, as well as replacing or cleaning the commutator. These components are important for transferring electrical power from outside the motor to the spinning coil windings of the rotor inside the motor.

Brushless dc (BLDC) motors, on the other hand, do away with mechanical commutation in favor of electronic commutation, which eliminates the mechanical wear and tear involved with brushed dc motors. In BLDC motors, the permanent magnet is housed in the rotor and the coils are placed in the stator. The coil windings produce a rotating magnetic field because they’re separated from each other electrically, which enables them to be turned on and off. The BLDC’s commutator does not bring the current to the rotor. Instead, the rotor’s permanent magnet field trails the rotating stator field, producing the rotor field.

Field-wound dc motors use a coil to generate a magnetic field and are used where high power and constant horsepower is required. Among the field-wound motors there are series-wound, shunt-wound, and compound-wound configurations. The armature and the field coils in a shunt-wound motor are connected in a parallel formation that causes the field current to be proportional to the load on the motor, while in series-wound motors, the armature and field coils are placed in series and the current passes only through the field coils. The compound-wound configuration combines both the series-wound and shunt-wound types and uses both configurations.

Lastly, the permanent magnet (or PM) motor uses permanent magnets such as high-energy neodymium to generate a magnetic field. These motors tend to be smaller and weigh less than the other common types of dc motors and so are well suited for applications where size and weight are important factors. One limitation of PM motors is that they cannot be speed controlled because the magnetic field is fixed.

Portescap unveils coreless DC motors with REE technology

Portescap (www.portescap.com) has announced that its coreless DC motors range meets the demanding requirements of intrinsic safety application with proprietary Reduced Electro Erosion (REE) technology.

“DC motor commutation is accomplished via brushes, which leads to electrical arcing during rotation. To reduce electro erosion while extending commutator life, Portescap innovated the proprietary REE coil system to reduce the effective inductivity of brush commutation by optimizing the mutual induction of the coil segments,” said Dave Beckstoffer, Project Manager for Strategic Markets.

“Portescap conducted tests on motors with and without REE coil optimization and found that commutator surface wear with REE coils showed improvements ranging from 100 to 300 percent.”

Aside from the benefits of REE technology, the company’s brush DC coreless motors also offers salient features such as no cogging, low moment of inertia, high efficiency, compact commutation and low friction resulting in high acceleration, higher continuous torque and very low joule losses. The motors deliver maximum continuous torque ranging between 0.66 mNm and 158.6 mNm, a low motor regulation factor (R/K2) of .3 103/Nms, and no load speed that range from 11,000 RPM (eight mm) to 5,500 RPM (35 mm).

Its intrinsically safe motor operation is especially important in ambulatory applications subject to extra-ordinary operating conditions and/or harsh environments. Typical applications include environmental analyzers, fuel cells and gas analyzers.

This highly efficient, lightweight coreless DC motors also serves as an ideal solution for miniature pump manufacturers faced with issues of intrinsic safety in portable applications.

Magnetek’s adjustable frequency drives suitable for crane/hoist applications

Magnetek, Inc. (www.magnetek.com) has introduced its latest IMPULSE® Series 4 Adjustable Frequency Drives, which continues the company’s tradition of providing the most cost-effective and reliable adjustable frequency crane control in the market, said Dan Beilfuss, Director of Sales at Magnetek.

The IMPULSEoG+ Series 4 can be utilized as a V/F crane control or as an open-loop vector for mechanical load brake hoists or traverse motions, while the IMPULSEoVG+ Series 4 can be utilized as a closed-loop flux vector crane control for high performance traverse motions and non-mechanical load brake hoists.

Beilfuss said that IMPULSE Series 4 drives integrates innovative control and safety features, such as Load Check II, which continuously monitors the frequency range’s hoist overload conditions and halting upward motion, while enabling the load to be lowered.

The latest Adaptive Ultra-Lift feature — which Magnetek has a patent pending — permits for hoist operation above base speed with an empty hook or light load. It constantly monitors motor torque while adjusting motor speed, allowing it to operate at peak performance to optimize plant safety and throughput. The Safe Torque Off feature eliminates the need for external disconnects as it offers a redundant hardware safety circuit to ensure that brake and motor power are removed when a safety controller or an E-STOP switch opens the drive input.

“We are excited to provide our customers with the advanced technology of the IMPULSE Series 4 line of crane controls and want to remind them that every IMPULSE drive is backed by Magnetek’s unsurpassed three year warranty,” quipped Beilfuss.

Posital introduces a magnetic rotary encoder with hollow shaft design

Posital (www.posital.com) has announced that its Magnetocode (MCD) absolute rotary encoders now features a new hollow-shaft variant of the MCD encoder, making the devices easier to mount on shafts up to 20 mm in diameter.

Featuring excellent accuracy, adaptability and reliability, the new devices are offered with digital or analog electrical interfaces. With measurement technology based on a Hall-effect sensor and a rotating magnet, the analog models make a great alternative for traditional potentiometers as it provides superior longevity, reliability and accuracy.

Unlike potentiometers, these new encoders do not run the risk of losing accuracy due to surface contamination or wear since there is no contact among its components. The encoders also offer flexible range-setting feature that allows the installer to “teach” the device the potential mechanical motion’s limits during operations. When the limits have been established, the device will instantly self-calibrate to enable the full range of electrical output to exactly match the mechanical movement’s full range.

This results to a remarkable improvement on the control system’s overall accuracy. To simplify the setup, the analog-output models also provide LEDs and buttons on its casing.

The MCD encoders’ digital outputs include CANopen, serial (SSI) and DeviceNet. These tough MCD encoders feature heavy-duty enclosures to protect the measurement components from dust, shock and vibration, as well as mechanical loads and moisture (up to IP 69K ratings). The hollow-shaft models also feature permanently lubricated brass and steel gear-set for a trouble-free and long service life.

Siko AH36M rotary encoder features “teach-in-function”

Siko GmbH (www.siko.de) has proudly announced the release of a new rotary encoder that adapts to the application and not vice versa — the AH36M rotary encoder. With this principle, the company has taken a new direction in the rotary encoder segment, and has incorporated a magnetic analog absolute encoder that features a “teach-in-function” to the range.

The new AH36M rotary encoder comes with two external inputs that allow it to be set to the preferred measurement range in just a few simple steps. This provides users the complete signal amplitude (from 0 to 10 V or four to 20 mA) across the exact measurement range that the user has selected. Whether the user wants to measure two, 10 or 100 revolutions, this new rotary encoder provides the best solution for the job, as it eliminates the need to stock encoders with various measurement ranges or gear ratios.

Using battery-free multi turn and non-wearing technology, the cost-effective rotary encoder completes the chosen measurement range in 4096 steps or 12 bits. Specifically designed for high loads, the AH36M rotary encoder features twin ball bearings.

Its battery-free multi turn technology and non-wearing magnetic measurement principle makes it suitable for positioning tasks in mechanically challenging work environments. Measuring 36.5 mm in diameter, the rotary encoder’s compact construction makes it ideally suited for use in applications with limited space. Although it comes in a compact design, the new AH36M rotary encoder still features a six mm hollow shaft.

Compact DC Gearmotor delivers 443 lb-in. torque at 2.0 rpm

Midwest Motion Products, Inc. (www.midwestmotion.com) has announced the release of the latest DC Gearmotor that comes with four “face mount” M5 threaded holes that are equally spaced on a 40 mm Dia. B.C. — the Model No. MMP-TM57-24V GP52-2076. Measuring 2.24 inches in diameter and 8.35 inches long, the robust Gear Motor accepts any 24 V DC source and features a keyed output shaft of 12 mm diameter by 52 mm long.

At 2.0 rpm, this reversible gearmotor delivers an output of 443 lb. in. (50 Nm) torque. Although it weighs only 4.5 pounds, this compact gearmotor offers an efficient design that requires only 3.6 Amps at 24 V DC to produce its Full Load Torque. This translates into very low noise operation, long life battery charge and lower costs for related drive electronics.

Rated with IP 54 protection level, the gearmotor’s unique design makes it suitable for operation in harsh environments. Its fully compatible speed controls — Model MMP 20A-24V-RSP or MMP 25A-24V help the gearmotor accomplish variable speeds.

The company’s typical options include Failsafe Brakes, Servo Motors with integral Optical Encoders, Analog Tachometers and Planetary Gearheads that comes with standard ratios ranging between 3:1 and 2653:1 as well as standard or low backlash precision gearing. It also offers various Motor Winding Options that include 28V, 12V, 48V, 36V, 90V and 60 Volts DC.

Midwest also offers standard ancillary equipment such as DC Servomotors, DC power supplies, Motor Speed Controls, PWM Servo Amplifiers, Linear Actuators and a vast array of DC gear-motors.

Roboteq’s HBL2350 drives two brushless DC motors

Roboteq (www.roboteq.com) has unveiled an all-new smart controller that can simultaneously drive two brushless DC motors each about 50V and 75A — the HBL2350.

The first in the group of high current, dual channel brushless motor controllers, HBL2350 can be utilized to control automatic guided vehicles, two-wheel driven small electric vehicles, balancing scooters and other applications that require high power brushless motors.

The controller receives commands either through an analog pedal or a joystick. Its standard R/C radio allows for easy robotic applications by means of remote control through USB or RS232 interface.

The controller can execute over 50,000 basic instructions in 1s through an integrated basic language interpreter. This feature is particularly helpful for adding custom functions through scripts without needing an external PLC or microcomputer.

The motors can operate in an open or closed loop position with an update rate of one kHz. Meanwhile, optical encoders can be used to measure the speed and travelled distance with high accuracy. The controller’s smart current sensing capability narrows down the highest power output to 75A under all load forms.

The controller can also hold up to 11 analogue inputs, six pulse and 19 digital and deliver up to eight 1A digital outputs, which can be utilized for activating brakes, valves, lights and other instruments. Housed in a strong aluminum case, the controller measures 228 mm x 140 mm x 40 mm.

Yaskawa AC Servo Motor comes in plug-and-play design

Yaskawa America’s (www.yaskawa.com) Drives & Motion Division has launched the latest servo technology that offers a superior alternative to the usual stepper technology at similar price. The Junma AC Servo features a plug and play design that does not require gain adjustments or parameter settings.

Delivering optimum servo performance, Junma eliminates time consuming setup while accepting pulse reference input from the PLC or host controller. After connection, users can then choose the reference pulse switch settings on the amplifier that will match the controller’s reference output. Connecting the feedback and power cables enables the motor to run and deliver a maximum torque of 4,500 rpm.

With system parameters set on system power up, Junma’s machine load inertia is automatically calculated, while its tuning gains are dynamically adjusted, even during load changes, enabling the system to adjust to varying conditions.

Featuring advanced control functionality, Junma’s vibration suppression and adaptive tuning functions simplify the commissioning of the machine while maintaining optimum efficiency and high-precision positioning. Junma also features other functions such as homing to marker pulse, jogging, torque limiting and electronic gearing.

Customers can select from Junma’s four different servo motor and amplifier sets, which feature rated output ranging between 100W and 750W capable of both 200V and 100V input voltages. It also offers servo motor feedback with a 16-bit incremental encoder, offering resolution of 65,536 pulses per revolution.

POSITAL offers new interface options for rotary encoders

POSITAL (www.posital.com) has announced that its Optocode (OCD) absolute rotary encoders now come with a new combined interface that allows simultaneous communication of both incremental and absolute position data. The company’s new interface is specifically developed to deliver cost effective and robust point-to-point communications between various kinds of programmable logic controllers (PLC) and encoders.

Utilizing the synchronous serial interface (SSI) standard, the new interface relays absolute rotary position information to the PLC. While the shaft is rotating at a maximum speed of 16,384 pulses per rotation, the encoder also sends a series of electronic pulses. An optional index pulse can also be transmitted once every complete rotation.

Meanwhile, the incremental pulses can be transmitted via a push/pull connection or over an RS-422/485 link. Responding to a request from the controller, the dual-personality encoders offer access to absolute rotary position information while accurately measuring the rotational velocity in real-time and making it suitable for monitoring rotating machinery or for motor control applications.

These encoders also offers other new features such as optimized diagnostic reporting through the SSI connection or through case-mounted LED’s, and an optional case-mounted push-button that enables the operator to re-set the absolute position readout’s zero-position (datum).

The new OCD encoders keeps the previous generation devices’ best features, including accuracy, highly effective shaft and connection seals (up to IP66 protection), precision (up to 216 steps per turn) and single- or multi-turn capabilities. Available in hollow, solid and hub shaft variants, the units can be supplied with a cable exit or a connector.

Bison Gear unveils globally compatible AC Gearmotors

Bison Gear & Engineering Corp. (www.BisonGear.com) has introduced a new range of parallel shaft gearmotors which are globally compatible with various AC power sources — the VWDIR14 AC. Designed as Von Weise Drop-In Replacements, the VWDIR14 AC parallel shaft gearmotors were developed to meet the growing interest of OEM’s in designing equipment for export markets.

Offered in six standard, off-the-shelf versions, the new gearmotors employs 1/20 PS (37.3 W) AC motors that can be easily operated from either 230V or 115V, 50Hz or 60Hz power sources. Delivering gear ratios ranging between 10:1 and 494:1, the gearmotors provide output speeds between 181 and four RPM, and maximum continuous torque ratings of 50 in. lbs (5.65 Nm).

The integral gear reducers and totally enclosed non ventilated (TENV) permanent split capacitor (PSC) AC motors are reversible, and also feature all-position face mounting with an overhung load capacity of 50 pound (22.7 kg.).

“These Bison drop-in replacements for VW14 AC gearmotors feature permanent split capacitor four-pole motors that operate at half the speed of the competitive units they replace. With corresponding gear ratio changes, this result in a quieter, longer life gearmotor,” Bison Gear Application Engineering Supervisor Clayton Hinkle said.

“An engineered resin first-stage gear further contributes to quiet operation which makes these gearmotors ideal in such applications as foodservice equipment, automated displays, peristaltic pumps, business machines, ticket dispensers and even pellet stoves.”

Available with CSA and U.L. recognition as standard, the new VWDIR14 AC parallel shaft gearmotors can be also provided to OEM’s with CE recognition.

POSITAL unveils compact Profinet IRT Encoders

POSITAL (www.posital.com) has unveiled optimized PROFINET I/O encoders that support RT, IRT and NRT data transfer (isochronous real-time/real-time/non-real-time).

Featuring an Ertec200-based platform, the improved encoders delivers cycle times as low as 10 ms (RT) and 1 ms (IRT). With a diameter of just 58 mm, the compact devices are parameterized through the control system while a GSDML device file facilitates its configuration.

Aside from eliminating the need for connection cap, the new encoders do not require switches or terminating resistors for address allocation. Since it is shorter than most Industrial Ethernet encoders offered in the market, the new encoders can be utilized in various applications that require limited installation space. The encoders are available in two options — the solid shaft version or the hollow version.

To record position value, the PROFINET I/O models employs a proven opto-electronic scanning method similar to those used in OPTOCODE encoders. In single-turn mode, the sensor delivers a resolution of 16 bit per revolution, while the multi-turn sensor achieves a maximum revolution of 16.384 (14 bit).

The new encoders are ideal for use in applications in packaging technology, automotive body construction and standard machine construction. The retention of the device profile management allows easy migration from the current Profibus systems to the new standard.

Specifically designed for temperature ranging from -40°C to +85°C, the units provide the side of the housing IP67 protection, while the shaft side is also provided with IP64 protection.

CGB Precision Products offers Barden angular contact bearings

CGB Precision Products (www.cgb.com.au), a specialist supplier of super precision ball bearings and related components, has announced that it is offering a series of Barden precision bearings, such as angular contact bearings for machine tooling applications.

With one ring shoulder totally or partially removed, angular contact bearings ensure higher speed capabilities and greater load capacity by allowing larger ball complement than those found in comparable deep groove bearings.

The spindle bearings are assembled to a contact angle by altering the radial clearance and feature nominal contact angles of either 15º or 25º, which enables them to deliver improved radial rigidity and capacity.

The angular contact bearings are available in two variants — non-separable and separable.

In a separable bearing, the cage keeps the balls in place to separate the outer ring assembly, which holds the cage and the balls, from the inner ring.

Ideal for use in applications where bearings must be integrated in blind holes, the separable angular contact bearings are also used in applications where press fits are needed both in the housing and on the shaft.

The separable variant of angular contact bearings permit a dynamic balance between a rotating component and an inner ring mounted in place, and the housing and the outer ring.

Angular contact bearings support combinations of thrust and radial loading or thrusts loads alone. Angular contact bearings, however, do not accept radial loads only.

Technosoft iPOS3602 compact and intelligent drive solution

Technosoft (www.technosoftmotion.com) has introduced a new range of intelligent servo drives anchored on a revolutionary design concept that provides compact solutions higher-power density — the iPos line.

Modularly engineered to cover both low-volume and high-volume applications, iPOS3602 (36 V, 2 A, 75 W) — which is the first member of this family — offers drive solution fitted on just 21 mm x 54 mm of PCB space as well as a complete motion control. It integrates all the basic motion control functionality, motor control functions as well as the PLC functionality on one compact plug-in module. Featuring CAN / CANopen interfaces and an optional EtherCAT interface, the iPOS drive controls any linear or rotary brushless, DC brush or step motor.

With the integrated EasyMotion Studio platform and motion controller, Technosoft’s iPOS3602 can execute complex motion programs at drive level. It can also operate as an intelligent CANopen and EtherCAT slave. In simple applications the new iPOS3602 can operate as a single-axis motion controller and drive while in a stand-alone mode and independently running the program within its non-volatile memory. In systems that need a host, the new iPOS drive functions as an intelligent slave executing motion sequences propelled by commands or input lines received though RS-232 or CAN bus.

The drive’s iPOS card features motion capabilities that include 3rd order PVT and 1st order PT interpolation, position or speed profiles (trapezoidal, S-curve), electronic gearing and camming, digital or analog external reference, matched with the cyclic synchronous position, torque and speed modes specific to EtherCAT.

The new drive can operate with a vast array of feedback devices. Sin/Cos and incremental encoders, linear or digital Halls are supported by default, while BiSS, SSI, EnDAT absolute encoders as well as resolver interfaces are offered through an additional extension.

Bishop-Wisecarver Releases UTCSK Camera Slider Kit

Bishop-Wisecarver Corporation announce the availability of a camera slider kit based on their UtiliTrak Linear Guide Technology. The UTCSK camera slider is a sleek, compact motion solution for filmmakers looking to create smooth, professional camera shots with minimal equipment and hassle.

“The UtiliTrak product line has been successful in diverse industrial applications as linear guides due to the smooth, and precise rolling characteristics of the guide wheels,” said Brian Burke, Project Engineer for Bishop-Wisecarver. “Our creative in-house video production staff requested a camera slider for producing impressive dynamic shots to incorporate into product demonstration videos. We realized that this useful application would be valuable to other B2B professionals as a cost-effective solution to their own in-house video productions.”

Ideal for small to medium lightweight DSLR cameras and lenses, UTCSK is available in two standard lengths of aluminum track (1000 mm and 1500 mm). For easy tripod mounting, ¼-20″ threads are located at the center and on both ends of the track. The anodized aluminum wheel plate with linear guide wheels includes a ¼-20″ camera thumb screw for use with or without a ball head mount. For camera safety, two adjustable end stop blocks with nylon screws come as standard.

For more information on the UTCSK camera slider including pricing and product sheet, visit www.utcsk.com

Bishop-Wisecarver
www.bwc.com

Crouzet’s Brushless DC Motor delivers high speed and torque

Crouzet (www.crouzet.com), a world manufacturer of automation control components such as pneumatics, micro motor and micro control products, solid-state relays and sensors, has announced the release of the second generation 150 Watt Brushless DC Motor, which is durable enough to support high loads without operation interruption.

Featuring 150 Watt power, the new three-stage planetary gearbox provides expanded capabilities for applications demanding high torque and speed.

The company’s Model 80199701 gear motor offers variable torques and speeds, as well as maintains a quiet, smooth operation. A part of the 801997 series, the motor improves the company’s output torque to 120 Nm from 25 Nm. With 200 N axial and 1000 N radial, the robust motor easily handles high side loads and lends itself to long life and controllability.

Measuring just 229 mm in length and 81 mm in diameter, the compact motor integrates a shaft extension on the motor’s rear, enabling for brake or encoder. It is offered with one, two or three stage gearboxes, can operate with voltages from six to 75 VDC, and utilizes industry-standard eight-wire connection scheme and hall sensors.

“The use of this brushless DC motors is a logical choice where long life is a concern,” said Jim McNamara, Applications Engineer at Crouzet.

“That combined with the long life gear motor, makes it an excellent solution for many applications,” he added. “Other benefits include reduced noise, increased efficiency and the elimination of brush dust.”

Maxon’s New EC 40 Brushless Motor

Maxon’s new EC 40 is characterized by high quality materials and high performing specifications. The motor features a neodymium permanent magnet, stainless steel housing and welded flanges. It features a very flat speed/torque gradient (about 3.6 rpm/mNm), mechanical time constant 2.1 ms, permissible speed 18’000 rpm, and efficiency of 89%. The ironless winding offers extra quiet running and high stall torque.

As all maxon motors, the EC 40 can be combined with a multitude of components, such as encoders or gears. As a new member, the permanent magnet brake AB 32 joins the maxon modular system. It is designed for operating temperatures of 40 to +100°C and is the EC 40′s perfect match. A wide range of compatible controllers, from 1-quadrant and 4-quadrant servo amplifiers to programmable positioning controllers, make the EC 40 a multi-talented high-power unit.

This new EC 40 is an excellent choice when it comes to industrial applications, logistics equipment, mobile robotics, packaging machinery and power tools or aerospace.

maxon motor
www.maxonmotorusa.com

PCC offers new brushless DC motors and drives

PCC (www.process-control.com) has announced the launch of its latest gearmotor/drive package for its auger based, continuous loss-in-weight blenders and feeders. To rotate the metering auger, the AFG/PF feeders and X-Series blenders previously integrated a permanent DC gearmotor and a PWM drive. The company has developed a new breed of motor drives that would control its previous permanent magnet motors and its latest generation of brushless DC motors.

Encoderless and brushless, the new gearmotors offers far more superior performance, reliability and a longer service life as against the old model. Unlike the eight gear/power ratio combinations of the previous permanent magnet gearmotors, the new gearmotors only needs two gear/power ratio combinations to cover the required range of the RPM for the feeders and blenders. The company’s latest gearmotor/drive is 100 percent compatible with PCC feeders and blenders already in service and has already started shipping new systems in April.

PCC General Manager, Dana Darley, said that the company’s new auger drive package represents a significant advancement in the reliability and performance of PCC’s premium line of gravimetric feeders and blenders.

He added that the company is so confident of this latest system that it is considering giving three-year warranty on both the gearmotor and the drive, whether it was purchased as a spare part, an upgrade or on a new feeder or blender.

Renishaw Resolute absolute encoder offers sub-micron accuracy

Renishaw (www.renishaw.com) has announced the release of its latest Resolute absolute encoder which features Fanuc serial communication in linear encoder formats for grinding machines, high-precision machine tools and diamond-turning machines.

Resolute was designed to deliver sub-micron accuracy and resolution to one nm. A true absolute encoder, Resolute automatically determines absolute position upon switching on, effectively eliminating the need for reference returns or battery backup.

The new absolute encoder utilizes a detection method that is similar to an ultra-high-speed digital camera reading from a fine-pitch, non-repeating barcode scale.

Users can easily capture images, analyze and interpolate them to fine resolutions of up to one nm, even when operating at a maximum speed of 100 m/sec.

With immunity from contamination, this technique achieves broader setup and running tolerances attributed to the absolute encoder’s dirt-rejection and cross-checking capability.

Renishaw guarantees safety since the absolute encoder has been integrated with separate checking algorithm, which regularly monitors position and ensures problems are flagged up before reaching the controller.

To provide users with remarkably higher-fidelity encoder feedback, Resolute offers a harmonious mixture of scale technology and high-performance redhead.

With Sub-Divisional Error (SDE) controlled to within +/-40 nm, the dynamic response of the absolute encoder is optimized. As standard on RELA Invar scales, Resolute offers overall accuracy that is better than +/-1 um, while high accuracy at lengths up to five m is offered on RSLA stainless-steel scales.

RTLA-S and RTLA rugged steel tape scales, which offer +/-5 um/m accuracy, quicker and easier installation as well as lengths up to 10 m, are also available.

BEI Brushless Generator withstands high shock and vibration

BEI Kimco Magnetics (www.beikimco.com), a subsidiary of Custom Sensors & Technologies (CST), Inc., has been unveiled the DIH18-21-BBNA Brushless Generator. The generator, which is used to power a remote brake health monitoring system, was developed in response to a railroad train signaling application requirement.

The challenging generator requirement demands that at the speed of 10,000 rpm, the generator must be able to supply a continuous voltage output of 40VDC Volts DC. It also requires the generator to be remarkably durable and reliable to withstand the consistently high vibration and shock levels common of a railcar environment.

Measuring 2.1” in axial length and 1.8” in diameter, BEI Kimco’s DIH18-21-BBNA Brushless Generator meet these requirements. At speeds of 11,000 rpm, the generator delivers a constant output of 40VDC. To absorb the intense shock and the relentless vibration associated with the application, BEI Kimco has integrated patented bearing suspension technology to the generator which also improves its reliability and longetivity. The generator was also designed with innovative robust “one piece” housing to effectively eliminate vulnerable attachment points. Similar technology has also been successfully utilized to reduce noise in medical applications demanding minimal acoustical noise levels.

After the development of the product, the generator has been placed in a series of demanding reliability and vibration qualification test protocol.

“The successful completion of the tests is a testament to the robustness of the BEI design,” said Walter Smith, Application Engineer at BEI.

ACS Stepper Drive/Controller offers affordable Electric Actuator Solutions

Tolomatic (www.tolomatic.com) has unveiled its latest ACS Stepper Drive/Controller. Specifically designed for use with electric actuators, the company’s latest actuator control solution (ACS) is a low-cost, easy-to-use stepper drive and controller.

Integrated with configurations for the ERD, Tolomatic’s rod-style electric actuator linear motion is easily and automatically created in the desired linear units (inch or mm).

The ERD range of actuators, which has been originally developed as an economical replacement for pneumatic cylinders, has become an affordable solution for applications such as pick-and-place, heat-staking, sorting and diverting, changeovers and more.

“The primary goal in designing the ACS Stepper Drive/Controller for the ERD product family was to create a low-cost, extremely easy-to-use drive and control product intended for single-axis actuator solutions,” said Aaron Dietrich, Electric Products Manager at Tolomatic.

“What makes creating motion so easy is that through two simple configuration steps, the ACS drive knows everything about the axis of motion. Combined with any of Tolomatic’s electric actuator products, the entire axis of motion is available from one supplier.”

For infinite position capability, the ACS provides four, eight or 16 move command modes (incremental, absolute or jog). This range of command modes is flexible enough for a vast array of single-axis actuator solutions. It also features adjustable motion profile parameters (velocity, position, force, acceleration/deceleration) that are configurable separately for each move.

To save energy, the ACS reduces holding current when not in motion. Aside from its force-limiting capacity, the ACS is also capable of zone output based on the position of the actuator. Its digital I/O can be configured in either 24 VDC Opto-Isolated, NPN or PNP, while its drive/controller is suitable for use with most brands of 24 VDC stepper motors.

Transtecno unveils compact DC electric micro gearmotors

Transtecno has unveiled a new range of micro motors which are suitable for intermittent, reversing or continuous operation applications — the Intecno micro gearmotors.

Featuring power ratings ranging from eight watts to 140 watts (intermittent duty), these micro motors have low voltage power supply  of 12 VDC or 24 VDC and are available in five sizes — 35 mm, 42 mm, 52 mm, 65 mm, and 80 mm (diameter).

These compact motors can be easily installed in mounting position and provide coaxial arrangement of input and output. Lubricated with grease, the planetary gearboxes are maintenance-free and are offered with 72 reduction ratios from 3.7:1 for single-stage to 2,076:1 for four-stages.

“Intecno DC micro gearmotors are perfect for many applications where both small dimensions and good performances are required,” said Moreno Ferrari, General Manager at Transtecno.

“These characteristics are important in medical, robotics and electric vehicles. Another popular application is in electric windows or doors where the movement can be done with a small powerful micro gearmotors like these.”

To complete the product line, the company also offers options such as DC motor controls and bearing mounted input shafts.

“Planetary gearboxes were chosen because of the wide range of reduction ratios. We offer 72 ratios from 3.7: 1 (1 stage) to 2076:1 (4 stages) and they are lubricated with grease therefore maintenance-free,” said USA Sales Manager Jon Roetman.

“These planetary gearboxes can be customized to the application due to the possibility of using metal, plastic or material mix versions. The LN (low noise) version is also available, which significantly lowers the gearbox noise.” he added.

New Falk V-Class™ Gear Drives Line from Rexnord

Milwaukee, Wis. – Rexnord Industries announces the Falk V-Class, a new line of gear drives designed for maximum uptime and durable performance.

The Falk V-Class incorporates the latest advances in materials technology, engineering design, and manufacturing processes to produce a tough, reliable gearbox for demanding applications. These advancements, coupled with innovative mounting and cooling accessories, provide a reliable, sustainable gearbox. Features are built into the drive to provide maximum uptime in a smaller drive at a lower total cost of ownership (TCO).

One of the most distinguishable features of the Falk V-Class is the housing. The heavy-duty, horizontally split housing design incorporates advanced gearing, optimized through the latest materials and technologies, to provide maximum performance under load. The housing shape and features were designed through the use of Computational Fluid Dynamics (CFD), to enhance the drive’s superior thermal dissipation qualities.

Additional features were built into the Falk V-Class to increase productivity and profitability. The drive incorporates exclusive Magnum no-leak seals with oil drain backs and purgeable grease chamber to eliminate oil leaks. An optional, eco-friendly DuraPlate™ cooling system requires no water or electricity to operate and provides optimal cooling to fully use the unit’s torque density.

Rexnord offers standardized monitoring and lubrication packages, 24/7 customer support, readily available spare parts, and a product services team that offers onsite support, in addition to a 36-month warranty.

Learn more about the Falk V-Class at www.rexnord.com and www.falkv-class.com.

Compact servo motors: shorter – lighter – more dynamic

The 8LV servo motor series has been expanded to include additional high-performance products. With the motto “Highest power density in the smallest installation space” in mind, all mechanical and electrical elements in this series of servo motors have been integrated into an extremely compact unit. Equipped with the smallest possible absolute encoder system with a resolution of 262144 (=218) steps per revolution, the system is able to achieve the highest precision while taking up the least amount of space.

In order to save weight, installation space and the amount of mass being moved, gearboxes are mounted directly on the motor. This new mounting system was made possible by totally reconstructing the motor’s output flange and adapting it completely to the gearboxes. The center gear rests directly on the motor shaft and replaces the input shaft on the gearbox. This type of mounting renders an adapter flange, the clamp system and the gearbox input bearing obsolete. In addition to an approximately 20% savings in weight and installation space, the amount of mass that has to be moved is considerably reduced as well.

Because of the rigid structure and the small amount of mass, high-performance control loops can be created for dynamic applications, even in tight spaces.

With gearboxes that are mounted directly on the motor, it’s possible to select between the 8GM30 economy series, the 8GM40 standard gearboxes and the 8GM50 reinforced gearboxes.

Gearboxes in the standard series are available as single-stage and two-stage units with a backlash <8- <15 arcminutes. The 8GM50 series uses bearings optimized for radial and axial forces for mechanical compatibility with Wittenstein products.

With the characteristics mentioned above, this series is optimally suited for applications that place the highest demands on dynamics and torque when limited space is available.

B&R Industrial Automation Corp.
www.br-automation.com

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