Contact instability of the direct drive robot when constrained by a rigid environment

A sufficient condition for the stability of robot manipulators in constrained maneuvers is derived. Attention is focused on the class of direct drive robots whose rigid links dominate the robot's dynamic behavior; compared to the robot, the environment is assumed to be infinitely rigid. The stability of the manipulator-environment system is investigated, and a bound for stable manipulation is determined. This bound is verified via simulation and experiment on the Minnesota direct drive robot.>