AN ANALYSIS OF SOME FUNDAMENTAL PROBLEMS IN ADAPTIVE-CONTROL OF FORCEAND IMPEDANCE BEHAVIOR - THEORY AND EXPERIMENTS

Force control in robotic mechanisms has been extensively researched. T here have been several results which have concentrated either on expli cit force control or impedance control. Further, many of these works r equire accurate identification of the stiffness of the environment. In this work we examine the role of adaptive controllers for force contr ol with unknown system and environment parameters and clearly integrat e several fundamental issues such as explicit force control, impedance control, and impedance control combined with a desired force control. All of these issues are treated using standard model-reference adapti ve control (MRAC) approach. Within the same framework, we analyze othe r equally fundamental issues such as environment stiffness identificat ion, stability of the complete system, and parameter convergence. We d emonstrate the effectiveness of the proposed theory through experiment s.