Stepper Motors - Motion Control Tips

New integrated stepper motors and drives from AutomationDirect

July 17, 2018 By Miles Budimir Leave a Comment

AutomationDirect has added integrated motors and drives to its SureStep line of stepper motion control products. Integrated stepper motor/drives save panel space, require less wiring and are less expensive.

The new SureStep integrated drive/motor units provide accurate micro-stepping position and speed control for smooth motion and step response and require only two components; power supply and integrated stepper motor/drive. Standard motor/drives and advanced motor/drives are available. Existing SureStep systems require four components including power supply, stepper drive, motor extension cable, and motor.

SureStep advanced integrated motor/drives have available torque from 54 to 340 oz-in. and software-selectable resolutions ranging from 200 steps per revolution. The advanced drives can operate with traditional high-speed inputs, but can also be commanded via 0 to 5 V analog input. An internal indexer can accomplish point-to-point moves controlled via ASCII communication.

Free SureMotion Pro drive configuration software is available for Advanced integrated motor/drives (not required for Standard drives) to easily configure and setup the drive, including drive, motion control mode, I/O, and motor. A Status Monitor screen aids in troubleshooting alarms and faults.

SureStep integrated motor/drives start at $97.00.

For more information, visit www.automationdirect.com/integrated-motor-drives.

Oriental Motor 60 W (1/12 hp) right-angle motor joins BMU and BLE2 series brushless motors

July 9, 2018 By Lisa Eitel Leave a Comment

Oriental Motor now sells an expanded line of its popular BMU and BLE2 Series brushless dc motor with the addition of a new right-angle 60-watt (1/12 HP) model.

The new right-angle 60 watt (1/12 HP) brushless motor uses the BL5 motor and features an IP66 connector. It is combined with a hollow shaft right-angle hypoid JH gearhead, making this new model release the most compact right-angle brushless motor available in the brushless dc motor product group offered by Oriental Motor.

The BL5 brushless motor with this new connector offers IP66 degree of protection and allows for easy and direct connection between the motor and driver with two available orientation of cable outlet direction. The BL5 brushless motor with IP66 connector is also designed to work interchangeably with both the BMU and BLE2 speed controllers. This common BL5 motor design allows for maximum design flexibility.

The JH type hypoid right-angle gearhead offers a maximum rated torque of 138 lb-in. (15.6 N-m) through a stainless steel, metric output shaft with no permissible torque limit and a wide output speed range of 80 to 3,600 rpm.

Added value benefits include space saving features, increase maintenance-free performance, continuous flat torque, stable and wider speed control thanks to the brushless motor design advantage.

To learn more about Oriental Motor’s brushless DC motor speed control system line up, visit this deep link to the dc-motor product page at orientalmotor.com.

Since its founding in Japan in 1885, Oriental Motor has been a world leader in motion control systems. For over a century, we have concentrated on technological advancement and product design improvement — an emphasis evident in the sophisticated devices we market today.

Three ways to reduce heat when operating a step motor

June 29, 2018 By Lisa Eitel Leave a Comment

Reduce motor heat by reducing idle and running current — or switch to closed-loop control.

Eric Rice | Applied Motion Products

Step motors are widely used motion-control devices because of their simple setup and accurate positioning with an open-loop configuration. But problems associated with heat generation can arise. That’s because the drive that powers an open-loop step motor doesn’t use feedback to control the amount of current provided to that motor. Instead, the drive provides full current at all times … regardless of torque demand on the motor. So the motor consumes power at excessive rates …. wasting energy and generating avoidable amounts of heat.

In some applications, operators run open-loop step motors with as much current as possible to generate the most torque possible. That ensures the motor will reach its position in the application. But as current increases, so does motor temperature. If motor temperature rises too high, windings short and the motor ceases to function. So design engineers (and motor end users) must find ways to maximize motor torque while avoiding motor overheating.

One industry approach is to set the drive to give the motor its rated current. Doing that will make the motor hot but not too hot. It’s normal for step motor temperatures to reach 70°, 80°, or even 90°C. While these temperatures make it too hot to touch the motor, the motor itself is unharmed.

But how else can design engineers (and motor end users) reduce motor heat? Here we’ll explore three more ways:

Reduce idle (holding) current
Reduce running current
Switch to closed-loop control

First — Reduce the idle (holding) current for the motor

Many motion control applications need the most torque when the motor accelerates and decelerates to meet its mark. But when the motor idles, or holds position, it requires much less torque. These instances are a good time to reduce motor current.

Most modern stepper drives do this automatically. For example, the drive might reduce idle current to 50% of the running current. More sophisticated stepper drives let design engineers program the idle current to any value between 0 and 100%. If a step motor spends even a modest amount of time sitting still, reducing idle current has a significant impact on motor heat.

Second — Reduce running current

Many design engineers err on the side of caution when selecting a step motor — often choosing a motor with more than enough torque (rather than just enough) for the application at hand. In these scenarios, it may be possible to reduce the motor’s running current with some trial-and-error testing. Basically, this requires reducing running current by a small amount and monitoring the motion output. If this trial run proves successful, reduce running current again and retest motor performance.

Continue making adjustments until the motor mispositions or stalls. Then slightly increase the current so the motor resumes accurate positioning. In some cases — especially when a step motor is oversized for an application — the engineer can reduce running current enough to measurably reduce the temperature of the motor.

Third — Switch to a closed-loop step motor system

The most dramatic reduction in heat generation occurs when replacing an open-loop step motor system with a closed-loop step motor system. Step motors are operable within a servo control loop when outfitted with a high-resolution encoder and powered by a suitable closed-loop drive. This relatively new system configuration necessitates that the engineer replaces the application’s motor and drive. But the magnitude of temperature reduction is usually worth it.

To review, a closed-loop step motor system uses feedback loops to accurately control step motor current, velocity, and position. The current loop ensures that the current provided to the motor by the drive is only the amount needed to meet torque demand. When the motor isn’t producing torque (or producing anything less than maximum torque) current to the motor automatically drops accordingly. This closed-loop control scheme significantly improves motor temperature … reducing it by as much as 50% or more in some applications.

Additional benefits of closed-loop steppers are quicker acceleration and higher throughput (up to 50% more torque than rated holding torque) as well as quieter operation (even to 10 dB quieter) because there’s less current in the motor windings. Plus without stalls, system accuracy is higher.

Closed-loop step motors incorporate a high-resolution encoder and are driven by an integrated, closed-loop drive that automatically reduces current to the motor when the load isn’t demanding torque.

Test results confirm that closed-loop step motors draw current only when needed, so they run cooler and with less power consumption than open-loop options. Consider actual tests that run both the open-loop and closed loop variations to get the same motion profile:

Acceleration = 100 rev/sec² and deceleration = 100 rev/sec²
Distance = 5 rev and speed = 10 rev/sec
Dwell time = 0.1 sec

Both carry a set load inertia and rotor inertia and operate from a 48-Vdc power supply. Results in the graph below show that the average power consumption of an open-loop stepper system delivering such output uses 43.8 W.

In contrast, a comparable closed-loop stepper system consumes only 14.2 W to deliver the same routine. That reduced power consumption translates into less heat generation and lower energy bills.

Results from tests conducted by Applied Motion Products confirm that closed-loop stepper systems consume less current than comparable open-loop stepper systems — and stay cooler too.

Applied Motion Products | applied-motion.com

Eric Rice graduated with an Electrical Engineering degree from the University of Illinois Urbana-Champaign.

He joined Applied Motion Products as an applications engineer in 1997 and specializes in step motors, servo motors, drives, and controls.

What’s the difference between cogging torque and torque ripple?

June 25, 2018 By Danielle Collins Leave a Comment

The basic operation of an electric motor relies on the interaction between the rotor’s permanent magnets and the stator’s energized windings. But even when the motor is not powered and no current is flowing though the windings, there is a magnetic attraction between the permanent magnets of the rotor and the ferromagnetic teeth of the stator. The magnetic attraction varies depending on the flux density, or strength, of the magnetic fields, and this variation causes uneven torque production, which is referred to as “cogging torque” or “torque ripple.”

While these two terms are sometimes used interchangeably, cogging torque generally refers to the phenomenon that causes torque variations, and torque ripple is the effect these variations have on motor performance.

Cogging torque

Cogging torque is a product of the magnetic interaction between the poles of the rotor’s permanent magnets and the steel laminations of the stator’s teeth. In other words, when the poles of the rotor line up with the teeth of the stator, a force is required to break the attraction, and this force is referred to as cogging torque. Cogging torque is position-dependent, according to the location of the stator teeth relative to the permanent magnets, as the magnets constantly search for a position of minimum reluctance.

A motor’s cogging torque profile depends on the number of permanent magnets in the rotor and the number of teeth in the stator and can be minimized through mechanical means by optimizing the number of magnetic poles and teeth, or by skewing or shaping the permanent magnets to make their transition between stator teeth more gradual.

Cogging torque occurs in permanent magnet motors, including brushed and brushless DC motors and synchronous AC motors. Because it occurs in an un-energized motor, it is sometimes referred to as “open-circuit torque.”

Torque ripple

The result of cogging torque is a variation in torque production — referred to as torque ripple — that occurs when the motor is energized with constant current. Due to the nature of the interaction between the magnetic fields of the rotor and the stator (described above), torque ripple varies sinusoidally. At high speeds, it is often filtered out by the inertia of the system, but at lower speeds, torque ripple can cause unwanted speed fluctuations, vibrations, and audible noise.

Torque ripple (green) varies sinusoidally due to the interaction between magnetic fields of the stator and rotor.
Image credit: Precision Microdrives Limited

Cogging in stepper motors

Stepper motors also exhibit cogging torque, but in stepper motor discussions, it is often referred to as “detent torque.” Like cogging torque, detent torque is a result of magnetic equilibrium in a non-energized motor. This magnetic equilibrium must be overcome before the motor will rotate, which means that the detent torque reduces the amount of running torque the motor can produce. The amount of detent torque a stepper motor experiences is proportional to the motor’s speed, so the effect of detent torque on running torque is more substantial at higher motor speeds.

Permanent magnet and hybrid stepper motors, which use a permanent magnet rotor, exhibit detent torque; but variable reluctance steppers, which use a non-magnetized, soft iron rotor, do not. Of permanent magnet and hybrid types, hybrid steppers have higher detent torque due to their toothed rotors, which allows them to better manage the magnetic flux between the stator and the rotor.

Detent torque reduces the ideal torque (and power) that the motor could produce, with the effect becoming larger as speed increases.
Image credit: Geckodrive Motor Controls

Detent torque is typically 5 to 20 percent of the motor’s holding torque, which is the amount of torque the motor can produce when the windings are energized but the rotor is stationary. But detent torque is not always a liability: When the motor is decelerating, it counters the motor’s momentum and helps it to stop more quickly.

Integrated motors from Applied Motion Products enable high-speed motion control

June 5, 2018 By Miles Budimir Leave a Comment

Three new models of StepSERVO Integrated Motors from Applied Motion Products offer cost-effective and high-speed motion control for high throughput applications such as packaging and labeling, automated test and measurement, and automated assembly. With encoder feedback and advanced control loops that incorporate servo control, Applied Motion StepSERVO Integrated Motors provide a cost-effective motion control system that operates faster, cooler and quieter than competitive technology.

Using closed loop feedback and advanced control technology, the StepSERVO Integrated Motors create more torque for higher acceleration in meeting faster machine cycles that results in greater productivity. The StepSERVO Integrated Motors also operate cooler and more quietly than standard motors by drawing just enough current to control the load. In fact, closed loop StepSERVO Integrated Motors automatically reduce current to the motor when the load is not demanding torque and provide reductions of 10 dB in noise due to less current in the motor windings.

“Our StepSERVO Integrated Motors combine a high-resolution incremental encoder and closed-loop servo firmware to create peak torques up to 50% higher than open loop step motors, as well as cooler and quieter operation,” explains Eric Rice, Marketing Director, Applied Motion Products. “As motor power consumption is often an issue for faster machines, our StepSERVO Integrated Motors consume less power to reduce operating costs.”

Applied Motion Products offers three models of StepSERVO Integrated Motors that support step and direction, streaming commands, fieldbus communications and stored Q programming for standalone operations.

TSM Series Integrated Motors feature 8 digital inputs, 4 digital outputs and 1 analog input and support RS-232, RS-485, CANopen, Ethernet, EtherNet/IP and Modbus communications. Motors are available in various frame sizes, including a new NEMA 34.
SSM Series Integrated Motors feature 3 digital inputs, 1 digital output and 1 analog input and support Ethernet, EtherNet/IP and Modbus TCP communications.
TXM Series Integrated Motors combine the features of the TSM Series with IP65 rated environmental capabilities and M12 connectors for operating in wet and dusty environments.

For more information visit www.applied-motion.com.

Distributor insight: Conversation with Warren Osak on motion-control trends

March 2, 2018 By Lisa Eitel Leave a Comment

In a recent phone interview, we got to chat with Warren Osak, CEO of Toronto-based Electromate Inc. — a distributor founded in 1986 that focuses on electromechanical motion control. More specifically, Osak’s company sells primarily servo systems and stepper systems — often for demanding or challenging applications requiring high precision, accuracy, and bi-directional repeatability. Electromate also specializes applications destined for harsh environments and high duty cycles. Here’s what Osak had to say about current trends in the motion industry.

Lisa Eitel • Design World: One trend we see is an uptick in both traditional stepper-motor applications and those for hybrid steppers … especially in robots and medical applications.

Osak • Electromate: In the field of stepper motors, it’s a tale of two technologies. On one end of the spectrum, you have low-end steppers … and these can take the form of tin-can stepper motors (also known as can-stack stepper motors) that output rotary or linear motion. For the latter, the motor often incorporates an acme screw instead of an output shaft. Such technology is low cost and highly customizable — but there’s a lot of price pressure in this marketplace.

On the other end of the spectrum are integrated stepper motors. These have servo-like performance by closing the position loop around a feedback device such as an encoder. Plus, anti-resonance circuitry built into these stepper motors can ensure smooth acceleration between 50 and 500 Hz.

We see the middle of the market — actuated by the traditional 1.8° hybrid stepper motor as a standalone device — kind of going away. Technology is either migrating upward (and taking the form of integrated motors or smart motors) or migrating downward — to lower-cost motors with less sophisticated structures. More specifically, the use of traditional hybrid stepper motors has been yielding to integrated products … while in lower-end applications, we see more use of less-sophisticated motors with customer-provided integrated chips (ICs) to drive them.

Eitel: Battery-powered equipment is proliferating — especially in the form of ATVs, AGVs, drones, and service robots. What are the design challenges here?

Osak: For embedded robotic applications, we’re seeing a lot more 48-V and 24-V designs … and even some 12-V applications. Note that when I say embedded robotic, I’m talking about frameless motors — the brushless motors that run off low voltage and directly integrate into the wheel drives of AGVs, ATVs, and utility-task vehicles. In our marketplace, size requirements are increasingly challenging — with torque-density requirements also increasing … and that’s especially true for motion designs that run off low-voltage battery-operated systems.

Eitel: No conversation about trends is complete without some discussion of IIoT. What are your thoughts?

Osak: IoT has been a buzzword over the last few years, and we see a lot of IoT connectivity in the HMI and automation-control space … where HMIs connect on fieldbus networks to enterprise networks and other systems outside the motion design — including vision systems, supervisory control systems, and SCADA systems. All of these are increasingly interconnected — primarily through HMI devices with full IoT (Industrie 4.0) connectivity. But we’re not seeing a proliferation of IoT devices on the motion-control side of things — in motion controllers or programmable automation controllers, for example. I believe that adoption will come, but right now we’re not seeing it.

Today’s localized motion controllers or distributed controllers primarily handle I/O and not vast data processing and analysis … as they’re still task-specific motion-system components. In contrast, at the HMI level there’s much more networked manufacturing I/O.

Eitel: Do you see more OEMs wanting turnkey motion solutions?

Osak: There’s definitely continued push for more integration, and our customers often want to tie their machine controls into our motion control for a unified integrated solution — programmable under one language. That said, we don’t see individual component providers going away, as there will always be need for bespoke and best-of-breed manufacturers that build custom products for custom applications.

maxon precision motors EC 4 brushless dc motors (which can be fitted with GP 4 planetary gearheads) are 4 mm in diameter with an ironless winding.

Eitel: Anything you’re seeing in design miniaturization that impresses you?

Osak: There have been big advancements in the construction of servomotors. The physics of optimizing the magnetic flux generated from rare-earth magnet assemblies (and new production techniques) have leveraged improvements in motor designs. So, we’re seeing continued improvement in the torque density of servomotors well beyond what I once believed achievable.

In layman’s terms, the torque output one could get out of a NEMA-34-frame servomotor from eight or 10 years ago is now achievable with a NEMA-23-frame servomotor. In the same way, torque output of a NEMA 23 frame servomotor from eight to 10 years ago is now what today’s NEMA-17-frame motors can produce. So motors are definitively more power dense than in the past — and in fact for a given package size, there’s 50 to 100% increase in torque output versus motors produced a decade years ago.

What’s more, miniaturization is going to continue, because miniaturization imparts better use of space, reductions in mass, and reductions in cost — so I don’t see a point of diminishing return. Of course, there will be a point at which we get diminishing returns — where gains in servomotor construction simply don’t boost torque output appreciably — but we haven’t gotten there yet.

Eitel: Anything you’re seeing that’s prompting new uses for linear-motion technologies?

Osak: We’re seeing adoption of roller-screw actuation devices, which are more efficient than traditional forms of actuation (such linear bearing systems and round-rail bearing systems paired with ballscrew and acme screw drives). Increasing linear servo-actuator efficiency in turn allows design engineers to use more compact (yet higher thrust) actuators in applications traditionally driven by hydraulic actuation. In fact, electric linear actuators with roller-screw drive mechanisms can in some cases replace hydraulic drives even in very high-powered systems.

Eitel: Onto the topic of fluid power … what’s your take on servo-pneumatic designs?

Osak: We don’t sell any pneumatic systems, so I can’t comment on that directly … But I can say we get feedback from customers who want reliable solutions with longer mean time between failure (MTBF) — and a reduction in part count is a great way to get a higher MTBF. Because electrically driven servo actuators have fewer parts than pneumatic or hydraulic systems, they ultimately need (in theory at least) less downtime.

Eitel: Do you see any products that incorporate advanced materials to boost performance?

Osak: We see increased use of ceramics in gearing technology — with a few gearbox manufacturers now replacing case-hardened and steel and alloy gears with ceramic gears. We’re also seeing ceramic shafts and bits (such as pins) in gearboxes as well. Ceramic has a lot of unique properties — the most important being noise reduction. So in fact, planetary gearboxes with ceramic internals are half as noisy as traditional planetary gearheads … and they have a lower coefficient of heat expansion, so exhibit less stress than metal alloys when hot. Because ceramic components don’t expand as much, they also have tighter backlash and runout tolerances than comparable internals made of metal.

Eitel: This is news to me — because I primarily associate the use of advanced ceramics with rotary bearings.

Osak: Well, consider maxon precision motors. If I had to give a very rough guesstimate, I’d say 10% of all their gearbox products we see now have ceramic internals. They have a division that manufactures ceramic injection molding (CIM) and metal injection molding (MIM) gearbox internals for high-performance gearmotor designs. These include low-moisture gearboxes, low-backlash gearboxes, and high-torque gearboxes. Ceramic subcomponents definitely make sense in smaller-frame motors — especially those destined for medical applications where minimization of noise and vibration (and high load capacity) are critical.

Eitel: What technologies for motion control are currently showing the most innovation?

Osak: Sensor technologies seem to be advancing about twice as fast as other components used in motion-control systems. New developments for feedback devices also outnumber those for servo drives, rotary actuators, linear actuators, and motors — and I don’t know why that is. There’s certainly a lot of cutting-edge R&D in the world of feedback devices … so the pace of advancement in encoder, resolver, and linear variable differential transformer (LVDT) designs has just been astounding.

Eitel: We see electronics improving sensing and motion feedback.

Osak: Yes — and even with all this new technology, the price for feedback is coming down — it’s unbelievable. Just to give real-world example: Traditionally a design engineer would buy a motor and specify encoder resolution — and (whether incremental or absolute) encoder resolution was preset. But sometimes after that motor or servo actuator was deployed, you’d realize more (or less) resolution was needed. So what do you do? In the past, you had to buy another motor … or (in some rare cases) you could send the motor back, and the supplier would fit a different encoder.

Well today encoders can be field programmable. So you can buy an encoder … and if you think you need more resolution, you just program it (while it’s still in the field) with a handheld device. How cool is that? The ability to program an encoder for an application in the field in 30 seconds or less — without a pre-specified resolution — also means you can stock a supply of one given encoder model and just pull them off the shelf for programming as they’re needed. So design engineers have a lot more flexibility to standardize.

In fact, this is just the tip of the iceberg. Some encoders even include ASICs to allow more than just the programming of resolution. Some linear encoders even let end users program for pitch, N+1 feedback, and redundant feedback.

Eitel: Posital Fraba comes to mind here, as they sell very configurable encoders.

Osak: We sell Posital Fraba products, including encoders that have multiple tracks: One feedback signal is absolute, and one feedback signal is incremental, but they come from the same device. Each signal can be at a different frequency range and a different resolution. Electronics enable all this functionality and (in a lot of cases) field programmability. In short, this manufacturer listens to engineers and identifies their requirements … and then comes out with specialized product to meet those requirements. That differs from the “build it and they will come” motion-manufacturer mentality. So Posital Fraba manufactures more than a million encoder varieties — literally more than a million — and each is one customizable to each specific customer requirement.

Electric motors: Trends in stepper, battery-powered, and integrated motion designs

March 2, 2018 By Lisa Eitel Leave a Comment

From induction motors in electric vehicles to tiny coreless dc motors in drug-delivery equipment, electric motors continue to proliferate. Last year we saw consumer products, implantable medical devices, and automation of previously manual tasks spur the most innovation in motor design and use. This year those trends continue — and now we see increased use of servo and stepper motors in robotics.

maxon precision motors EC 4 brushless dc motors (which can be fitted with GP 4 planetary gearheads) are 4 mm in diameter with an ironless winding; ISO 13485 certified; and suitable for use in laboratory robots, micropumps, and diagnostic devices. Two lengths deliver power to 0.5 and 1 W. “We also want to offer more value-add services, as more companies than ever in the U.S. want finished motor and motion systems — so-called drop-in designs,” said McGrath of maxon. “So to that end, our expanding U.S. factory will have the capacity to supply custom assemblies and PCBs.”

In fact, whether it’s basic tin-can motors for low-cost custom actuation or integrated motors that output servo-like performance, overall use of stepper motors is growing. On the latter, a study by P&S Market Research projects a CAGR of 6.3% through 2023 for the global closed-loop stepper motor market. P&S cites the well-known benefits of control-feedback signals and power-adjusted current control as key reasons for the technology’s steady adoption.

Low-current dc motors from ISL Products Intl. Ltd. come in myriad mechanical and electrical configurations. Sometimes gearmotor modifications help the dc motors meet exacting OEM application specifications. In other cases, the motor must have special construction to avoid inducing EMI and RFI interference (Here, raw materials in the motor components are a main consideration, said to Kawaller of ISL.) Designs with reduced power consumption benefit from motors with specialized internal construction and nontraditional component materials.

Warren Osak, CEO of Toronto-based distributor Electromate Inc., sees this trend for integrated stepper motors, even while the middle of the stepper-motor market (actuated by standalone 1.8° hybrid stepper motors) recedes. Technology is either migrating upward (and taking the form of integrated motors or smart motors) or migrating downward — to lower-cost motors with less sophisticated structures, according to Osak.

“The use of traditional hybrid stepper motors has been yielding to integrated products … while in lower-end applications, we see more use of less-sophisticated motors with customer-provided integrated chips (ICs) to drive them,” he added.

Full interview with Osak: Motion-control trends distributor insight

Some closed-loop stepper manufacturers we surveyed for the Design World Trends issue include Schneider Electric Motion USA, Applied Motion Products Inc., Lin Engineering, MICROMO of Faulhaber, Oriental Motor Co., and Nippon Pulse America Inc. — with commentary from the latter in our actuator trends coverage. All detail pre-integrated or application-specific motor offerings. Case in point: Automation in the oil and gas industry has created numerous opportunities for motion control products, but stringent requirements for hazardous location ratings rule out most standard motor and drive solutions.

Use of tin-can stepper motors is on the rise, and now some new tools let engineers check their programming on the little motors more easily. Consider the Motion Checker 5 controller from Nippon Pulse America Inc. — a standalone handheld controller with an integrated driver circuit. Using it is as simple as plugging it into a normal outlet and connecting a stepper motor to run through motion sequences.

“To serve engineers in this industry, we’ve released the world’s only ATEX-rated stepper drive for hazardous locations … and this year we’ll introduce our first explosion-proof step motor to pair with it,” said Eric Rice of Applied Motion Products. “The drive is already being used on rigs in the oil field for applications where accurate braking and speed control of drill strings are required.”

Motors in (proliferating) battery-powered designs

Battery-powered designs such as ATVs, mobile robotics (including AGVs), scooters, ebikes, and drones present unique motion-system challenges. Motors that integrate into these designs might need to accept 48, 24, or 12-V input, and nearly all of them must meet tough efficiency requirements … NEXT PAGE →

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Applied Motion intros UL-listed and CSA-certified stepper and servo motors

February 8, 2018 By Miles Budimir Leave a Comment

Applied Motion Products introduces a range of UL-listed and CSA-certified stepper motors and servo motors for use in applications requiring certifications in North America and Canada. Units are recognized to Standard UL-1004-6 for Servo and Stepper Motors, UL 1004-1 Standard for Rotating Electrical Machines, and Canadian CSA Standard C22.2 No. 100-14 for Motors and Generators. Customers are now assured that Applied Motion stepper and servo motors meet high-quality standards for electrical safety associated with UL and CSA certifications.

Applied Motion UL-Recognized stepper motors include both single and double-shaft versions in NEMA frame sizes 17 through 34, with torque values from 31 to 1,841 oz-in. These motors are designed to work optimally with Applied Motion stepper drives, ensuring smooth motion and high performance in every application. The company’s UL-Recognized servo motors include J Series models in frame sizes 40 mm through 80 mm. Units feature a 10,000 count incremental commutating encoder and an IP65 rating for the motor body. The servo motors are specifically designed to work with Applied Motion servo drives.

Applied Motion UL- and CSA-certified motors are suitable for a wide range of motion control and automation applications in both the commercial and industrial markets.

For more information, visit www.applied-motion.com.

Lin Engineering hybrid stepper motors now in NEMA-6 frame sizes

October 4, 2017 By Lisa Eitel Leave a Comment

Lin Engineering now sells 106 Series hybrid stepper motors with a step angle of 3.46° and 104 steps per revolution. The compact motors are just 16 mm wide but deliver to 1.85 oz-in. holding torque. That equates to quadruple the holding torque of can-stack PM steppers … and in fact, the 106 Series hybrid stepper motors are five times more accurate than can-stack PM steppers as well.

The 106 Series motors are designed to satisfy increased demand for ever-smaller equipment with enough torque and speed to be useful in these applications — particularly useful for medical devices and laboratory automation. The aim is to eliminate the need for OEMs to pick large-framed motors and then shrink the rest of the design to accommodate the motor. More after the jump.

Lin Engineering hybrid stepper motor expertise spurred creation of the new NEMA-6 motor.

Increasing the step angle from a typical 1.8° to 3.46° allows for twice the holding torque of competing designs and nearly quadruple the holding torque of conventional permanent-magnet (PM) stepper motors of comparable size — which typically have to0.5 oz-in. of holding torque maximum.

Or consider how a typical PM motor may only deliver a step angle of 18° or 20 steps/rev. Because the Lin Engineering 3.46° hybrid stepper motor delivers 5.7 times higher resolution than that, output motion is more precise.

In addition, the 106 Series leverages the speed advantages of BLDC motor technology. The step angle pairs with the low-inertia rotor design to deliver 1 oz-in. of dynamic torque at speeds to 8,000 RPM.

Specific applications include miniature pumps, optical sensor controls, and fluid metering and control. Other applications include motorized hand tools such as electronic pipettes. For more information, visit the Lin Engineering product page on the 106 Series motors.

Hybrid linear stepper motors: Operation and applications

September 27, 2017 By Danielle Collins Leave a Comment

Like servo motors, stepper motors are available in both rotary and linear designs. When an application requires force (rather than torque) output and can operate in open loop control, a linear stepper motor is often the preferred solution. Although linear stepper motors are available in both variable reluctance and hybrid designs, the more common version is hybrid linear stepper motors.

In a hybrid linear stepper motor, the base, or platen, is a passive steel or stainless steel plate with slots milled into it. The forcer contains motor windings, permanent magnets, and laminations with slotted teeth that serve to concentrate the flux that’s created when current is applied to the coils. The teeth of the forcer and the platen are staggered by ¼ tooth pitch in relation to one another to ensure that constant attraction is maintained and that the next set of teeth will come into alignment as current is switched in the coils. This means that for each full step of the motor, the forcer moves along the platen by ¼ tooth pitch.

In a hybrid linear stepper motor, the platen is passive and the forcer contains laminations with slotted teeth, windings, and permanent magnets.
Image credit: Parker Compumotor

Whereas variable reluctance linear stepper motors can only operate in full step mode, hybrid versions can operate in either full step or microstepping modes. Microstepping, which divides the step angle into smaller increments, enables higher resolution motion and better control of speed and force. Because each phase of the motor is driven with (theoretically) ideal sine waves, 90 degrees apart, microstepping also allows the current to increase in one winding as it decreases in the other, providing smoother operation at low speeds than can be achieved with full- or half-step operation.

Microstepping makes the current waveform more sinusoidal and provides smoother motion at low speeds.
Image credit: Servo-drive LLC.

For guiding the load on hybrid linear stepper motors, either mechanical roller bearings or air bearings are typically used. (Because the platen in a hybrid linear stepper motor is passive, it can serve as the air bearing surface.) The magnetic flux between the forcer and platen creates a strong magnetic attraction, so these support bearings actually serve two purposes – to guide and support the load and to maintain the correct air gap between the forcer and the platen.

Like other linear motor designs, hybrid linear stepper motors can incorporate multiple forcers onto one platen, with each forcer moving independently. In addition to smooth low-speed operation (obtained with microstepping control), they are also able to achieve very high speeds and accelerations with high resolution and low to moderate force generation.

With simple mechanical construction and easy setup (no servo tuning required), hybrid linear stepper motors are ideal for applications that can operate in open-loop mode and that require either high speed with low force production or very smooth motion at low speed.

Featured image credit: H2W Technologies, Inc.