February 10, 2023

Why dual encoders are the right choice for robotics design

The demands on robotics designers, engineers and manufacturers are higher than ever. As motion, vision and software technologies improve, the bar gets higher and higher in terms of robotic capability and capacity. Meanwhile, regulators are increasingly focused on functional safety and other operational standards. How will robotic OEMs do it all while keeping costs down and streamlining manufacturing processes?

Answering these demands often comes back to the right components. The right encoder, specifically, can not only help increase function (positioning accuracy, data transfer, etc.) but also streamline manufacturing and keep costs down.

The traditional approach in robotics design is to put two encoders in each robotic joint—one on the back of the motor and one after the gearing. The problem is, the rotation of the motor doesn’t always line up with the rotation of the gearbox on the other side. This can ultimately cause mechanical inaccuracies.

The dual solution

Now, robotics engineers can monitor both the motor and the speed and positioning on the gearbox side, downstream from the transmission gear system—thanks to two-in-one dual encoders. Inductive dual rotary encoders from HEIDENHAIN combine two hollow-shaft encoders that measure motor speed and the rotational motion of the output axis (and thus of the robotic joint). They are made up of two rotors and one scanning unit positioned between them. The rotor for speed measurement is connected to the hollow shaft of the motor, while the rotor for position measurement is attached to the output axis. Let’s review the main advantages of using this type of encoder in robotics design.

Dual encoders enable higher performance and eliminate inaccuracies

To achieve high positioning accuracy, robot designers must first eliminate feedback and positioning errors that could cause mishaps. Inductive dual encoders achieve this by measuring the angular position of the joint directly at its axis. The dual encoder’s low mass also improves the dynamic performance of robotics, thereby shortening cycle time.

HEIDENHAIN dual encoders offer superior data transfer capabilities

As complete components, these encoders make it easy to document functional safety, a particularly important benefit for collaborative robots (cobots). With these encoders, the manufacturer can guarantee the required certification. What’s more, these encoders deliver extensive status data through their digital interface, enabling the implementation of detailed condition monitoring—like temperature—necessary for today’s predictive maintenance demands.

From a manufacturing data standpoint, dual encoders feature an electronic ID label accessible through the EnDat interface, which delivers data about the encoder’s resolution, ID number, serial number and more. Manufacturers can include additional custom data—including operating parameters, test results for fault-proof mounting, robot serial numbers and the date of production.

Dual encoders streamline manufacturing and assembly

HEIDENHAIN inductive dual encoders require only three parts: two rotors positioned on either side of a PCB that is rigidly connected to the stator. Each side of the PCB contains a scanning unit for one of the rotors. This streamlined design eliminates the work of mounting a rolling bearing and attaching a second cable during encoder assembly.

Dual encoders from HEIDENHAIN also enable automatable assembly steps (press-fitting the two rotors onto their hollow shafts). Plus, the remaining manual steps are simplified and less susceptible to error because the rotors don’t require specific orientation on the shaft and encoder components have no prescribed pairing. Parts can therefore be provided to the assembly line without any special orientation. The connection between the rotor and shaft is designed to ensure mechanical fault exclusion, allowing the assembler to simply pick up and install the part.

Dual encoders enable fast quality assurance and process stability testing

Dual rotary encoders from HEIDENHAIN enable electronic mounting diagnostics. This functionality immediately identifies whether the system has been correctly installed and works properly. We also provide Adjusting and Testing Software (ATS) for this inspection. The resulting values can then be incorporated into digital mounting and quality documentation, providing detailed information about every robot.

Malfunction and maintenance statistics, for example, can be analyzed in relation to mounting data in order to identify potential improvements to the manufacturing process. What’s more, the encoder’s own electronics can compensate for mounting inaccuracy between the rotors and the scanning unit, thus reducing rework and scrap. Finally, our dual encoders do not require a calibration run, making them immediately operable after assembly for mount-and-play functionality.

Looking to improve your robotics functionality and manufacturing processes? Contact us today about our dual encoder options.