Robot Path Control with a Decentral Structure

Abstract

One of the experiments of the D-2 spacelab mission was the Robot Technology Experiment ROTEX was which designed to test the use of robots in space. The expressly developed joint control concept for the manipulator arm with six joints is described. But first the modelling of a joint shows that the robot has to be modelled with joint elasticity. With the use of decentral disturbance observers for each joint not only the friction torques but also the coupling torques between the axes can be detected and compensated for. Furthermore, the observed states are utilized for a state feedback which allows an active vibration damping. Feedforwards are used to guarantee a high path accuracy whereby with the use of the disturbance observer the feedforward coefficients are independent of variable robot parameters. As the controllers were implemented as a linear discrete state-space system, they could be changed for the ground space during the mission.