Delta Tau Simplifies Robotic Control

See demo in Omron’s Pack Expo Exhibit, Booth C–1928

FullSizeRender_silo_1Thanks to their speed, accuracy and cost, delta robots shine in a wide variety of pick-and-place and packing applications. The main challenge with these useful robots involves integration. Delta robots typically need to work with other motion axes and vision systems. That’s where our Power PMAC® controller comes in.

The Power PMAC embedded controller makes it easy to coordinate the delta robot’s movements with ancillary motion and vision systems—even at the fast cycle times typical of these robots.

To make the delta robot work seamlessly as part of a more complex material handling or packaging system, we take advantage of Power PMAC’s immense computing power. Capable of handling up to 256 motion axes simultaneously, the Power PMAC easily makes all of the robot’s kinematic calculations and synchronizes them with other motion systems.

From the controller’s standpoint, it doesn’t much matter what the other motion system looks like. As long as we can talk to a motor and drive via standard protocols such as EtherCAT or MACRO, we can synchronize that motion axis with the delta robot.

See For Yourself. A demo of Power PMAC’s robot control benefits will be on display at the Pack Expo Show in our parent company Omron’s exhibit (Booth C–1928).

The Vision Delta demonstration uses a vision-guided delta robot to move six dice from an outer rotary table to an inner rotary table. The tricky part is that both tables spin in opposite directions during the pick and place operations. With the six dice scattered randomly on the outer table, the vision system first locates the position of each die on the outer table and sends the information to the Power PMAC controller. The controller then commands the delta robot to pick and place the dice onto the inner table in an orientation specified by a C# application running wirelessly on a Windows tablet.

Thanks to a servo loop update that reaches 40kHz for four axes and a program execution rate up to 10,000 blocks per second, the Power PMAC CPU easily makes all the calculations required to smoothly and accurately move the dice from one moving table to another.

Plug-and-Play for Pick-and-Place. For standalone robot and motion controllers, synchronizing robot movements with other motors and drives can be a difficult task. While possible, making standalone systems work together typically requires custom integration work and many engineering hours. With Power PMAC, the robot and other motion axes work together as one.

→ Send me the technical specifications

Taking The Errors Out of Your Encoders

For all their advantages in high-resolution motion control systems, sinusoidal encoders do produce measurement errors that you should take into account. These errors result from encoder signal imperfections and include gain mismatch, phase mismatch and excessive DC offsets. Left unchecked, they can ultimately reduce your system’s positioning fidelity.

Fortunately, we’ve just developed a brand new way to fix these errors on the fly using the interpolation software and circuity that processes the encoder signals. Called the auto-correcting interpolator, this new technology continuously identifies encoder errors and automatically corrects the calculated interpolated positions based on the most recently identified error characteristics.


Over the years, there have been many attempts to fix encoder errors during the interpolation process. These attempts have had limited success because of the constantly changing, unpredictable nature of encoder errors. And in the past, analog-to-digital converters (ADC) simply didn’t offer the combination of speed and resolution required for reliable error correction—particularly in high-frequency applications.

The auto-correcting interpolator, by contrast, uses new algorithms made possible by the growing availability of fast ADCs. How fast? The auto-correcting interpolator fully processes encoder signals at 20 MHz or about 400 times faster than our previous, already-fast interpolator.

Here’s a look at what this new technology can deliver:

Dramatically Reduced Position Errors. The automatic correction functionality typically reduces the position errors from encoder signal imperfections by more than 95%.

The Highest Positioning Resolution. Dividing each line of encoder output into more than 65,000 states, the auto-correcting interpolator drastically improves the resolution you can achieve with a given sinusoidal encoder. In our lab, we’ve used the new interpolation technology to make positioning moves within 32.5 picometers, or slightly more than the radius of a helium atom. This extreme resolution has implications for all kinds of inspection systems for optics, semiconductors and other precision manufactured goods.

The Smoothest Velocity and Acceleration Signals. Of course, not every application needs all that resolution. But keep in mind that the high resolution produced by the new interpolators can be valuable even in applications that do not require very high position accuracy. The high position resolution reduces quantization noise in the feedback, especially in the estimated velocity and acceleration, permitting higher servo gains and better performance. By using the auto-correcting interpolator, you not only get better position control, but velocity and acceleration signals become cleaner and more reliable too.

We’re just scratching the surface here. The auto-correcting interpolator has other technical advantages too. You can read about them in our latest white paper, which includes a detailed description of how the interpolator works and how it stacks up to earlier technologies.



Simplify The Control Of Complex Laser Scanning Jobs

Controlling complex laser scanning systems just got a whole lot easier, thanks to the addition of a laser galvanometer interface to our Power PMAC motion controllers.

The interface dramatically simplifies and improves the controls for laser scanning applications that require a motion system to position the scanning head relative to the work piece. These applications include laser marking, PCB processing, micromachining and medical device manufacturing.

In the past, these applications typically required separate controllers for the scanner and the motion axes. The new interface, which we based on the laser industry’s XY2–100 communication standard, allows a single motion controller running a unified program to govern every aspect of a laser scanning process.

Here’s why this unified approach to laser scanning control matters:

Improved positioning performance. Laser scanners have traditionally relied on stand-alone PC-based controllers to position the galvo mirrors and modulate the laser power. A separate motion controller would take care of positioning the scanning head relative to the work piece.

This dual-controller arrangement can work well in applications with modest performance requirements. Increasingly, however, laser scanning applications required positioning accuracies and speeds that are not easy to satisfy with separate networked controllers for different parts of the process.

From a positioning accuracy standpoint, using two controllers increases the chance that there will be errors at the boundaries of the laser scanner’s field of view as it moves over different parts of a larger work piece. These “stitching errors”  can reduce the system’s overall accuracy.

Faster laser processes. From a speed standpoint, it takes time to execute two programs and pass data back and forth between two controllers. The control system ends up executing its programs sequentially—moving the scanning head, firing the laser, moving the scanning head. The inefficiencies of this stop-and-shoot approach translate directly to added cycle time.


The combined control system, by contrast, executes only a single motion program that positions the galvo mirrors in the laser scanner and the x-y position of a scanner or workpiece. Our Spectral Decomposition algorithms allow a seamless coordination of the galvo actuator’s high-frequency movements and of the x-y positioning actuators.

In applications that require frequent positioning of the laser scanning head in relation to the work piece, we’ve found that the speed improvements from the unified control system can be significant.

Simplified controller programming. Another benefit to the single-controller architecture is simplified programming. Rather than writing, troubleshooting and maintaining several distinct chunks of controller code, the Power PMAC with XY2–100 interface needs just one program for all the positioning tasks. That same program will also control laser power on-the-fly through PMAC’s PWM outputs.

Detailed technical specifications for the Power PMAC can be found here.

Power PMAC

New Motion Controller For Embedded And Low-Axis Applications

Advanced motion control applications with a modest axis count can now get all the computational muscle of our Power PMAC controllers at a fraction of the cost, thanks to our new Power Clipper embedded motion controllers.

Intended for up to 4-axis applications, or up to 8-axis with an optional daughter board, the Power Clipper is built on a Power PMAC processor and custom digital signal processor. As a result, the new controller offers the same resolution, servo filters and advanced trajectory generation capabilities as Power PMAC systems capable of controlling up to 256 axes.

At the same time, the Power Clipper’s compact panel-mount design and limited axis count can keep costs as much as 50 percent lower than our flagship controllers.

The Power Clipper controller addresses a wide variety of precision motion control applications—including CNC machine tools, robotics, semiconductor equipment and general automation systems.

Despite its small form factor, Power Clipper supports all common motor feedback devices, thousands of general purpose I/O points and many cabled or plug-in accessories. For a more detailed look at Power Clipper’s capabilities, download the technical specifications here.


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