DSP motor controller eases automation design

OCTOBER 10--The brute-force approach to dealing with flexibility requirements for robotic systems is to make the robot's structural and drive members more massive and rigid.

OCTOBER 10--The brute-force approach to dealing with flexibility requirements for robotic systems is to make the robot's structural and drive members more massive and rigid. But the resulting large inertial forces require large actuators. So, system integrators are installing motor controllers to cancel excited vibrations in the robot.

Researchers at CAMotion Inc. (Atlanta, GA; www.camotion.com) have developed an optimized filter to fix these vibrations. However, their approach requires prior knowledge of the system's natural frequencies. These frequencies must be measured to adjust the frequencies generated as the robot's arm moves to different places in the work space or to impose longer operational delays to reduce sensitivity to natural frequency variations. By coupling this command filtering with learning control on repetitive motions, the errors between commanded and achieved positions are reduced.

CAMotion has embedded its motion-control algorithms in a series of scalable computer-controlled x-y-z gantry systems. To locally control the axes of these robotic systems, the company has built a remote-axis serial-interface device (RASID) that consists of a DSP-based motor controller with supervisory control provided by a PC. In operation, RASID receives reference trajectories and learned feed-forward motor currents from the PC via a USB interface. It then performs proportional-plus-derivative control of linear or rotary permanent magnet drives.

The company is exploring sublicenses of this technology with other industrial automation companies.

For more on this story, see the October issue of Vision Systems Design.

More in Robotics