Path constrained robot control with limited torques-experimental evaluation

A path velocity controller for modification of the velocity along the path when torques saturate can be used to improve path tracking. The path velocity controller acts as an outer feedback loop outside the ordinary robot controller, and modifies a nominal velocity profile, computed by minimum time optimization using available methods. An experimental evaluation of such a controller is presented. The experiments are performed on an industrial robot where the original robot control system has been replaced by a VME-based computer system. Experimental results demonstrate that the path velocity controller can adjust a nominal minimum time velocity profile, such that the result is good path following and good utilization of the available torque range. It is also demonstrated how the path velocity controller is able to compensate for time variations in the robot dynamics