PARAMETERIZATION AND ADAPTIVE-CONTROL OF SPACE ROBOT SYSTEMS

In space application, robot systems are subject to unknown or unmodele d dynamics, for example, in the tasks of transporting an unknown paylo ad or catching an unmodeled moving object. We discuss the parameteriza tion problem in dynamic structure and adaptive control of a space robo t system with an attitude-controlled base to which the robot is attach ed. We first derive the system kinematic and dynamic equations based o n Lagrangian dynamics and the linear momentum conservation law. Based on the dynamic model developed, we discuss the problem of linear param eterization in terms of dynamic parameters, and find that, in joint sp ace, the dynamics can be linearized by a set of combined dynamic param eters; however, in inertial space linear parameterization is impossibl e in general. Then we propose an adaptive control scheme in joint spac e, and present a simulation study to demonstrate its effectiveness and computational procedure. Because most takes are specified in inertial space instead of joint space, we discuss the issues associated to ada ptive control in inertial space and identify two potential problems: u navailability of joint trajectory because the mapping from inertial sp ace trajectory is dynamic-dependent and subject to uncertainty; and no nlinear parameterization in inertial space. We approach the problem by making use of the proposed joint space adaptive controller and updati ng the joint trajectory by the estimated dynamic parameters and given trajectory in inertial space.