Robust position and force/position control of robot manipulators

Abstract

As the employment of robots has been increased due to automation, the needs of effective control scheme for various robots have also been enhanced. Moreover, high performance control of robots becomes indispensable since modern industrial societies require fast and accurate handling of products. In practical situation, every physical system has uncertainties to some degree. Since traditional linear control schemes do not perform satisfactorily, there have been various control schemes in order to cope with uncertainties. Uncertainties belong to one of two categories. The first is uncertainty with known structure when functions governing a system dynamics are known but the parameters related to the functions are unknown. The second category is uncertainty with unknown structure when we do not know about the system dynamics at all. A useful robot is one that is able to control its motion and the forces it exerts on its environments. In this paper we deal with two categories of the control : motion control and force/motion control. Our control objective in each control category is to design a controller whose output will drive the actual trajectory to the desired trajectory. We derive controllers which are able to achieve our control objective under two kinds of uncertain conditions discussed above. Firstly, we propose a robust control scheme for the control of robot motion under parametric uncertainty with known structure. The proposed controller is based on the Lyapunov based theory of guaranteed stability of uncertain systems, sometimes referred to as the Leitmann or Corless-Leitmann approach in recognition of the pioneering work of Corless and Leitmann in this area. In order to combine the advantages of adaptive controllers we include an estimation law for the upper bound on unknown parametric uncertainty. Secondly, we consider the control of robots with unknown dynamics. We use CMAC network to approximate and compensate unknown dynamics. Unlike the previous ap...