Rotary Encoders - Motion Control Tips

Large through-hole angle encoders from HEIDENHAIN offer high accuracy

November 6, 2018 By Miles Budimir Leave a Comment

HEIDENHAIN’s new sealed angle encoders can be used as an alternative to modular angular encoders in motion control machining applications that require a larger than usual through-hole. The new RCN 6000 series absolute sealed angle encoders with integral bearings have an exceptionally large hollow shaft diameter of 180 mm (7.09 in.), allowing larger scale machines to take advantage of high resolution and signal quality that’s expected from HEIDENHAIN angle encoders.

Common applications for the RCN 6000 encoders are large-scale rotary tables and radio telescopes which can easily adapt their design to the encoder while the integrated stator coupling ensures ideal alignment of the components involved in the scanning process, even if there are deviations in the shaft coupling.

Unlike other angle encoders with integral bearing, the RCN 6000 series encoders use HEIDENHAIN’s METALLUR process (in which the graduation is applied directly to the bearing ring) and a reflected light scanning method which gives it compact dimensions and larger mounting tolerances when compared to other products of its type. These integrated features along with the compact design keeps mounting difficulty to a minimum while making the most of its unique shape.

The RCN 6000 encoder provides a through hole of 180 mm, overall height of 44 mm, a system accuracy of ±2 in., can handle speeds up to 200 rpm, is able to interface with EnDat22, Fanuc05 and Mit03-4, and has an IP 64 protection reducing the effort required for protective measures.

For more information, visit www.heidenhain.us.

Posital upgrades family of analog programmable rotary encoders

October 19, 2018 By Paul Heney Leave a Comment

Encoder specialist Posital has announced a new generation of analog rotary encoders for position control. Compared to the company’s earlier analog encoders, these new models feature improved accuracy, faster dynamic response and new programming options. They also accept a wider range of supply voltages, an advantage for mobile machinery applications.

Posital’s analog encoders are designed for positioning tasks that use analog control systems. Outputs are either voltage (0-5 V, 0.5-4.5 V, 0-10 V or 0.5-9.5 V) or current (0-20 mA or 4-20 mA). The magnetic measurement mechanism is wear-free and extremely durable so that these devices offer much better accuracy, reliability and service life than conventional potentiometers.

An important feature of the analog encoders is that they are programmable with measurement characteristics that can be customized to meet specific application requirements, (This feature is also available with Posital’s digital encoders with SSI and incremental interfaces.) Programming can be carried out at the factory, in a distributor’s warehouse or at the customer’s job site, thanks to the company’s easy-to-use UBIFAST programming tool.

Programmable characteristics include direction of rotation (CW or CCW), zero set and the encoder output range. Measurement range programming allows the full range of electrical outputs (voltage or current) to be set to match a user-defined range of mechanical motion, resulting in significant improvements to control system accuracy.

For single-turn models, the measurement range can be set to 90°, 180°, 270° or 360°. For multi-turn models, the range can be set anywhere between 1 and 65,536 complete rotations. Analog encoders are available with push-buttons on the housing that enable the user to easily specify the upper and lower limits of the mechanical motion, with the electrical output fully spanning this range.

Posital
www.posital.com

Totally encapsulated J1 rotary encoders IP69k electrical protection from Joral

May 9, 2018 By Lisa Eitel Leave a Comment

Joral LLC now has a new method to impart total encapsulation in its J1 electronic components. Specially crafted to ensure total protection from extreme temperature fluctuation, intense machine vibration, and pressure wash down, the Joral J1 line-shafted rotary encoders perform rotary motion feedback for industry, ranging from directional drilling rigs to timber harvesters.

Shafted J140 with shell removed displaying total encapsulation

Totally encapsulated J1 rotary encoders IP69k electrical protection from Joral

The new IP69k electrical protection and encapsulation process now available for J1 line shafted rotary encoders is comperable to that of the newly released ProxEncoder noncontact rotary encoder. The Joral encoders in the J1 Line come in J1939, voltage, and quadrature outputs, and other versions.

Prototyped on a FDM 3D printer, the new encapsulation method creates a fully protected electronics package, which creates an environmental barrier between the J1 Line Encoder’s shaft and bearing package. The new IP69k encapsulation is available immediately as a standard production item. Visit www.JoralLLC.com for more information on totally encapsulated J1 rotary encoders — as well as customizable connections and various output options.

Connection options include terminal, block, M12, M12 Pigtail, flying lead cable, M8, and Deutsch connectors.

Features of the totally encapsulated J1 rotary encoders

Totally encapsulated electronics (IP69k); shaft seal available for IP68 housing protection (IP67 standard)
Absolute multi-turn capable and rated MIL-STD 202 for shock and vibration
From the manufacturer of the PE18 ProxEncoder
Available outputs include quadrature, CAN J1939, PWM, analog, and more
Customizable connector options available

Founded in 2005, Joral LLC is the culmination of a long history of development in encoder and sensor technology by companies including Joral Devices, Joral Computer Services, and GS Global Resources. Today, Joral develops and manufactures harsh-duty electronic devices for mobile hydraulics and industrial applications. Joral has redefined the “rugged duty” position sensor by introducing protection methods such as total electronic package encapsulation, LED status indicators, and patented true non-contact coupling. For more information, visit www.joralllc.com or email sales@joralllc.com.

Joral introduces true non-contact rotary encoder with rectangular design

April 2, 2018 By Paul Heney Leave a Comment

PE18 ProxEncoder non-contact rotary encoder product line receives a square housing with side sense capacity. Enhancing the original PE18 proximity style form factor, the new rectangular design allows for easy mounting on flat surfaces. Two USPTO patents enable the PE18-BX ProxEncoder to detect on-axis rotation with up to 0.5-in. (12mm) air gap between the application and sensor.

The PE18-BX is 100% encapsulated for an IP69k configuration that survives destructive conditions like submersion in hydraulic oil, deep sea salt water, dust control spray, or corrosive wash. The PE18 ProxEncoder product line is designed to cater to both mobile hydraulic and industrial installations. It is available in common communications including analog, quadrature, and CAN J1939.

Highlights of the Joral PE18 ProxEncoder include:

Face or side oriented sensor target area
Patented true non-contact position sensing:
- 5-in. (12mm) gap between sensor and application
- 10-in (2.5mm) axial misalignment
- 30° planar tilt
IP69k environmental protection class
Rated MIL-STD 202 for shock and vibration resistance
Available Outputs: Quadrature, CAN J1939, PWM, Analog, and more
Customizable connector options available

Joral
www.ProxEncoder.com

POSITAL expands rotary encoder offerings with new through-hollow incremental encoders

March 22, 2018 By Miles Budimir Leave a Comment

POSITAL has extended is portfolio of rotary encoders with a new family of through-hollow incremental encoders. These devices are designed to be installed with the machine shaft passing through the sensor. They can be used to monitor rotary motion in a wide variety of machinery, including servomotors, material handling equipment and printing presses, offering cost-effective, space-saving solutions. For motors, they can be easily installed between the body of the motor and other components mounted on the shaft.

POSITAL’s through-hollow encoders are available for shaft diameters ranging from 3/8 in. (9.5 mm) to 1-3/4 in. (44.5 mm). The smaller units (up to 14 mm shaft opening) have an external diameter of 2-1/4 in. (58 mm), while the larger units (5/8 in. to 1-3/4 in. shaft size) have external diameters of 3 or 4 in. (77 or 100 mm). Available resolutions for these devices extend from 360 PPR to 4,096 PPR (pulses per revolution.)

All through-hollow encoders have rugged aluminum housings and environmental protection rated at IP65, ensuring longevity and high levels of operational safety. All variants are available with a variety of communications interfaces, including RS422 (TTL) 5 V or 11-30 V and Push-Pull (HTL, 5-30 V). Connection options include built-in cables or MIL-type connectors.

POSITAL’s through-hollow encoders are a good option for machine builders and system integrators who are looking for accurate motion feedback devices that are easy to build into new or existing designs.

For more information, visit www.posital.com.

True non-contact rotary encoder

March 2, 2018 By Mike Santora Leave a Comment

Joral LLC introduces the PE18 ProxEncoder non-contact rotary encoder product line. Modeled in a threaded proximity switch housing, the 18mm true non-contact encoder is designed to capture rotary motion where conventional sensors fail. Two USPTO patents enable the PE18 ProxEncoder to detect on-axis rotation with up to 0.5-in. (12mm) air gap between the application and sensor.

The PE18 is 100% encapsulated for an IP69k configuration that survives destructive conditions like submersion in hydraulic oil, deep sea salt water, dust control spray, or corrosive wash. Immediately available in common communications including analog, quadrature, and CAN J1939. The PE18 ProxEncoder product line is designed to cater to both mobile hydraulic and industrial installations.

Additional highlights of the Joral PE18 ProxEncoder include:
18mm threaded proximity switch style housing
Patented true non-contact position sensing:
o 0.5-in. (12mm) gap between sensor and application
o 0.10-in. (2.5mm) axial misalignment
o 30° planar tilt
IP69k environmental protection class
Rated MIL-STD 202 for shock and vibration resistance
Available Housings: Anodized aluminum and stainless steel
Available Outputs: Quadrature, CAN J1939, PWM, Analog, and more
Customizable connector options available

Joral
www.joralllc.com

Joral debuts non-contact rotary encoder for harsh environments

March 1, 2018 By Miles Budimir Leave a Comment

Joral LLC introduces the PE18 ProxEncoder non-contact rotary encoder product line. Modeled in a threaded proximity switch housing, the 18-mm true non-contact encoder is designed to capture rotary motion where conventional sensors fail. Two USPTO patents enable the PE18 ProxEncoder to detect on-axis rotation with up to 0.5-in. (12 mm) air gap between the application and sensor.

The PE18 is 100% encapsulated for an IP69K configuration that survives destructive conditions like submersion in hydraulic oil, deep sea salt water, dust control spray, or corrosive wash. It is available with common communications including analog, quadrature, and CAN J1939. The PE18 ProxEncoder product line is designed to cater to both mobile hydraulic and industrial installations.

Additional features of the PE18 ProxEncoder include:

18-mm threaded proximity switch style housing
0.10-in. (2.5-mm) axial misalignment
30° planar tilt
Rated MIL-STD 202 for shock and vibration resistance
Available Housings: Anodized aluminum and stainless steel
Customizable connector options available

To learn more about the PE18 ProxEncoder and see a working animation, visit www.ProxEncoder.com.

What is modulo positioning?

January 12, 2018 By Danielle Collins Leave a Comment

Cutaway of a multi-turn encoder.
Image credit: A-Tech Instruments Ltd.

In motion control, there are typically two types of positioning that can be used for a linear or rotary axis: relative, in which each position is based on a previous position, regardless of the actual position of the axis; or absolute, in which each position is referenced to a home, or zero, point.

Axes that have very long strokes, or those with “endless” positioning, such as rotary tables and conveyors, typically use multi-turn absolute encoders. Multi-turn designs can track the encoder’s position over many revolutions – typically up to 4096. (This is in contrast to single-turn encoders, which reset the position value after each full encoder revolution.) But even absolute positioning using a multi-turn encoder leaves the axis at risk of significant positioning error if the application exceeds the maximum number of encoder revolutions.

In mathematics, the modulo operation finds the remainder after the division of two numbers. A simple example: (9 mod 4) equates to 1, because when 9 is divided by 4, the remainder is 1.

This is where modulo positioning comes in. Take for example, a rotary table with a 16-bit multi-turn absolute encoder (capable of 2¹⁶, or 4096 turns) mounted to the motor, and driven through a 5:1 gear ratio. In this configuration, every 1 turn of the table requires 5 turns of the motor and encoder. Once the encoder exceeds 4096 turns, an overflow occurs, and the encoder starts counting from zero again.

When a multi-turn encoder exceeds its maximum number of revolutions, modulo positioning stores the overflow and ensures that no position information is lost.
Image credit: Lenze Automation GmbH

The first move requires 4.8 table revolutions (4 revolutions + 288 degrees), meaning the motor and encoder have made 24 revolutions (4.8 * 5 = 24). The encoder stores this information, and when the system is powered off and back on, it recognizes the position correctly.

The next move is much larger, with 825.6 table revolutions (825 revolutions + 216 degrees), meaning the motor and encoder make 4128 revolutions (825.6 * 5 = 4128). Because the encoder has exceeded its maximum of 4096 revolutions, an overflow occurs, and the encoder starts counting from zero again, recording only 32 motor/encoder revolutions (4128 – 4096).

When the system is switched off and then on again, it only recognizes that 32 motor/encoder revolutions, or 6.4 table revolutions (6 revolutions + 144 degrees), have taken place. The additional 72 degrees of table movement (216 – 144 = 72), which equals one full motor revolution (72 * 5 = 360), is missing. This loss of position happens each time the encoder exceeds its 4096 revolution limit.

Note that the overflow problem does not occur if the maximum number of encoder turns can be evenly divided by the gear ratio. For example, a gear ratio of 8:1, when used with a multi-turn encoder that has a maximum of 4096 turns, does not cause lost position, because 8 divides into 4096 evenly (4096 ÷ 8 = 512).

With modulo positioning, the overflow occurrence is stored in the controller, preventing the loss of positioning information. Alternatively, if the drive offers a “modulo” function, it can be enabled to track and store any encoder overflows. The modulo function is straight-forward to use, requiring the user to enter the modulo value (typically 360 degrees), the relationship between motor/encoder turns and axis turns (or linear travel), and the encoder type and resolution. Both modulo positioning solutions – controller-based or drive-based – ensure that the overflow is accounted for and the actual position is corrected accordingly.

Bearing-free SIKO encoder: Redundant non-contact angle and distance measurement for mobile machines

April 7, 2017 By Lisa Eitel Leave a Comment

In the field of mobile commercial vehicles, safety requirements are increasing, especially within the EU. This presents not only suppliers, but also manufacturers of vehicles, with new challenges. To make it as easy as possible for manufacturers to adapt to new requirements, the Buchenbach based firm SIKO GmbH has developed the MSK320R bearing-free rotary encoder. Designed especially for use in forklift trucks, it helps users to implement safety requirements such as EN 1175 (safety of industrial trucks). For example, in AGVs (driverless transport systems), the compact magnetic sensor can be used directly on the wheels for speed or rotation detection.

To meet functional safety requirements, many manufacturers rely on redundant signals. This can be achieved either by attaching two sensor heads or a redundant sensor. The MSK320R is equipped with two magnetic sensors for redundant position measurement. It thus has two completely separate position channels (A1, A2, /A1, /A2, B1, B2, /B1, /B2), and can be used in combination with a secure input card in the overall system up to performance level PLd.

Despite the higher component density, the housing of the MSK320R encoder remains very small and compact at 35 x 25 x 10 mm.

The advantage of the MSK320R lies in cost and space savings when compared to the use of two separate magnetic sensors with simple channels. There is also no need for the additional wiring and mounting required for two sensors.

Linear or rotary — By selecting the appropriate scale, the sensor can be used for linear displacement measurement (in combination with the MB320/1 magnetic tape) or for angle and speed detection (in combination with different SIKO rings – for example, the MRI01, MR320, or MBR320 rings can all be used).

Functional even in extreme conditions …

With an IP67 safety rating and a wide operating temperature range from -40 to 85°C (-40 to 185 °F) the MSK320R can also be deployed in extreme conditions. Negative temperatures and condensation in outdoor use, and even extreme solar radiation, are no problem for the sensor.

Like all of the magnetic sensors manufactured by SIKO, the MSK320R is also resistant to dust, chips, oils, grease, and moisture.

The MSK320R in continuous operation

The open, contact-free measuring system is extremely wear-resistant and low-maintenance, and the MSK320R is predestined for long-term use in the field of mobile automation. Other features of the MSK320R encoder include:

Increased safety provided by independent output channels
Two magnetic sensors and two signal conditioners in one housing
SIKO ZM-housing (small, compact, and space saving)
Accuracy: to 2 mm
Repeatability: +/- 1 increment (linear +/- 0.0125 mm)
Ambient temperature: -40 to +85°C
Also available with German plug
Cut costs by mounting an MSK320R sensor instead of two standard MSK320 sensors

For more information, visit siko-global.com.

FAQ: How do digital encoders simplify setup and zeroing?

February 28, 2017 By Lisa Eitel Leave a Comment

In a recent Design World video, my esteemed colleague Miles Budimir and I got to assemble and zero an AMT31 commutation encoder series from CUI Inc.

As we’ve covered in other editorial, capacitive technology can outperform optical technology. Used for years in digital calipers and to measure rotational movement, capacitive technology in encoders replaces optical disks with a printed circuit-board rotor containing a metal-trace sinusoidal pattern that modulates an electrical field. The receiving end of the modulated signal then passes back to a transmitter where it’s compared against the original through an ASIC. CUI’s AMT encoder series uses such capacitive technology.
Capacitive encoders advantages over common optical-based encoders include immunity to contaminants such as dirt, dust and oil; reduced sensitivity to temperature and vibration; higher reliability; and lower power draw.

Traditional installations of commutation optical encoders onto brushless dc motors is tedious and time consuming — because the optical disk must be physically and precisely rotated to align with the correct motor windings. Once aligned, the assembly must then be checked via back EMF for accuracy. This can take upwards of 15 minutes per motor.

In contrast, digital encoders allow for alignment in seconds. Case in point: The AMT31 has an ASIC and MCU so lets installers use a One Touch Zero feature and install the encoder in a few seconds. After physically mounting the encoder, energize phase 1 and phase 2 of the motor to lock the windings into place. Now align the encoder using CUI’s One Touch Zero alignment module. Turn the module on, plug it into the encoder, and check for proper communication with the encoder. Then press the alignment button — and just that easy, the encoder is aligned.

FAQ: How do digital #encoders simplify setup and zeroing? 🎯 @CUIInc Click To Tweet

Featuring three-phase U, V, W commutation signals, the AMT31 series output can accommodate brushless dc motors with 2 to 20 poles, programmable via CUI’s AMT Viewpoint graphical user interface. The series also offers supplementary A, B and Z channels for servo positioning and startup sequences. 20 programmable quadrature resolutions are available with a range of 48 to 4096 PPR.

The encoder works in temperature from -40 to 105°C and has a low current draw of 10 mA at 5 Vdc — so the AMT31 series is suitable for mobile and battery-driven equipment. An input range of 4.5 to 5.5 Vdc is standard, with options for CMOS voltage or line-driver outputs. Additional options include radial or axial connector orientations, nine mating sleeves ranging from 2 mm to 8 mm, and base plates with multiple pre-drilled mounting hole patterns to mate with a wide range of motors.

Thanks to its One Touch Zero module and AMT Viewpoint GUI, the AMT series simplifies control. Combined with high accuracy and simple assembly, the AMT31 works in myriad industrial, automation, robotics and renewable-energy applications.