Authors:
Stephen van Duin
;
Christopher D. Cook
;
Zheng Li
and
Gursel Alici
Affiliation:
Faculty of Engineering, University of Wollongong, Australia
Keyword(s):
Impulsive control, static friction, limit cycle, stick-slip, impulse shape, friction model, accuracy.
Related
Ontology
Subjects/Areas/Topics:
Control and Supervision Systems
;
Informatics in Control, Automation and Robotics
;
Robotics and Automation
Abstract:
This paper presents a modified impulse controller to improve the steady state positioning of a SCARA robot having characteristics of high non-linear friction. A hybrid control scheme consisting of a conventional PID part and an impulsive part is used as a basis to the modified controller. The impulsive part uses short width torque pulses to provide small impacts of force to overcome static fiction and move a robot manipulator towards its reference position. It has been shown that this controller can greatly improve a robot’s accuracy. However, the system in attempting to reach steady state will inevitably enter into a small limit cycle whose amplitude of oscillation is related to the smallest usable impulse. It is shown in this paper that by modifying the impulse controller to adjust the width of successive pulses, the limit cycle can be shifted up or down in position so that the final steady state error can be even further reduced.