The Study on Robust Control of a 6-Link Hydraulic Manipulator : A Comparison of Robustness among each Robust Control Methods based on Experimental Results

Abstract

A hydraulic manipulator has more advantages than an electrical drive system in terms of lightweight and high output, but from the standpoint of control performance, a hydraulic manipulator has some problems not found in an electric manipulator such as fluctuations of system parameter. In this paper, author is comparing some of robust control methods with conventional PI-D control regarding robustness with respect to changes in the system parameters of a 6-axes hydraulic manipulator. It was confirmed that distubance observer is robust only in the sense of model-matching characteristic' to the output of the nominal model. On the other hand, the system with disturbance observer could be transformed into a model matching 2-DOF control system with stabilizing filter Q(s), in which Q(s) plays a very important roll regarding robust stability of control system. Author proposed new design method for the Q(s) by applying H-Infinity control theory. As the result of this paper, author conclude that the 2 DOF control system with stabilizing filter Q(s) designed by proposed method is the best among other robust control methods.