Consideration for an Application of Trajectory control to Robotic Arm

Abstract

In order to realize an advanced motion control for robot arms, many control algorithm have been proposed. Now, for applying the trajectory control to the robot arm, the influence of identification errors concerning physical parameters of the robot arm on both unstable problem and tracking accuracy is the most significant matter.
In this paper, we clarify the consideration points for applying the trajectory control, that was already proposed by Mita, et al., and propose an evasion method of unstable problem. To put it in the concrete, the influence of the identification error of inertial terms or viscous damping on both stability and tracking accuracy is clarified, and it is shown that by tunning the design parameter socalled weighting factor, unstable problem caused by the identification error can be avoided, but the tracking accuracy can not be guaranteed. Moreover, it is shown that the unstable phenomenon occurs in the tracking though the stability concerning the equilibrium point is assured, and its reason is explained by giving attention to the output of the integral compensator. In order to avoid the instability phenomenon, we propose that the disturbance caused by the parameter error should be esimated by using the observer and that the feedback mechanism so as to cancel the disturbance should be constructed.