Download Development of a PC-Based Object-Oriented Real

Abstract
The industrial world of robotics requires leading-edge controllers to match the speed of new
manipulators. In order to improve the performance of the Deltabot, an ultra high-speed cable-based
robot, a new controller called the QNX Multi-Axis Robotic Controller (QMARC) was developed.
QMARC is a PC-based controller built for the replacement of the existing commercial controller
called PMAC, created by Delta Tau Data Systems. Although the PMAC has its own real-time
processor, the rigid and complex internal structure of the PMAC makes it difficult to apply advanced
control algorithms and interpolation methods. Adding unconventional hardware to PMAC, such as a
camera and vision system is also quite challenging. With the development of QMARC, the flexibility
issue of the controller is resolved. QMARC’s open-sourced object-oriented software structure allows
to the addition of new control and interpolation techniques as required. In addition, the software
structure of the main Controller process is decoupled for the hardware, so that any hardware change
does not affect the main controller, just the hardware drivers. QMARC is also equipped with a userfriendly graphical user interface, and many safety protocols to make it a safe and easy-to-use system.
Experimental real-time test has proven QMARC to be a reliable real-time system. Despite minor
fluctuations in the servo loop periods, the controller can still achieve close path tracking running at
2.5 kHz.
In comparing the PMAC and QMARC controller performance on two pick-and-place
paths, it was found that for both paths QMARC yielded better results than PMAC on all three motors
of the Deltabot. Accumulated following error for the PMAC was at least one order of magnitude
greater than QMARC, and QMARC was more easily tuned than PMAC. These experimental results
show that QMARC is a reliable and safe controller with consistent results.
The stable software foundation created by the QMARC will allow for future development of the
controller as research on the Deltabot progresses. Its open source structure will ease the way for new
researchers implementing software modules such as servo control algorithms and trajectory, or new
hardware like grippers and vision sensors, creating a flexible and powerful system that can be used
for many applications.
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