ROBUST SERVOSYSTEM DESIGN WITH 2 DEGREES OF FREEDOM AND ITS APPLICATION TO NOVEL MOTION CONTROL OF ROBOT MANIPULATORS

In this paper, we propose a novel robust servosystem design method based on the two degrees of freedom (TDOF) controller and its application to the advanced motion control for a robot manipulator. This servosystem is derived from the simple parametrization. It has the remarkable feature that the command input response and the closed loop characteristics can be specified independently by using two parameters which belong to the ring of stable and proper rational functions. We can determine the sensitivity and the complementary sensitivity functions straightforwardly through the optimization of the two design parameters. The control performances of our servosystem are shown by laboratory experiments. Next, by applying the TDOF position servosystem, we realize the completely decentralized joint control system of multi-axis robot manipulators. We do not need to take care of the influence of various kinds of dynamical forces, i.e., the centrifugal, Coriolis, and gravity forces, payload torque and even the frictional torque because they are sufficiently suppressed by the robust servomechanism at each joint. Furthermore, since there are no need to perform any coordinate transformations with respect to the speed and acceleration, the structure of our controller is extremely simple. This means that we do not need the complicated calculation of inverse dynamics which has been inevitable for high-speed control of robot manipulators. We realize various kinds of robot motion controls such as compliance, force, and hybrid controls in a unified way based on the robust position control. We implement our idea by using DSP and confirm their efficacy by laboratory experiments with respect to trajectory, compliance, and hybrid controls.