Categorizing Admittance Control Parameters for the Ranger 8-DOF Tele-operated Space Manipulator

Abstract

Position-based admittance control of a robotic manipulator is a strategy that allows the manipulator to achieve compliance without sacrificing positional accuracy or modifying the underlying position controller. Desired manipulator stiffness and damping can be specified so that the tool tip behaves as a spring-dashpot system. This work characterizes the range of parameters that allows stable task execution in contact with an environment of varying stiffness for the Ranger dexterous manipulator. A classical stability analysis and simulation of the controller is conducted to predict its response in contact. The manipulator's behavior is then observed during a series of simple tasks involving contact in one and two degrees of freedom. Suitable gains are chosen such that interaction forces at the tool tip are kept low. A compliant peg-in-hole insertion task is successfully accomplished. The work also outlines the implementation of an algorithm that removes unwanted gravity forces measured at the tool tip.