Compliance at the end effector of an electrohydraulically controlled robot

A general mathematical model for a robot, where each link is driven by an electrohydraulic servo motor, is developed. Based on this model, definitions for compliance of the end effector of the robot due to changes in the external load on the end effector are defined. Both global and local and dynamic and static compliance definitions are introduced. A formula for the closed loop local, static compliance of the end effector is derived in terms of the robot parameters, the hydraulic leakage parameters, and the feed-back gains. Design limits to this compliance are determined explicitly by the hydraulic stiffness parameters. It is shown that effective feedback control design involves consideration of a tradeoff between closed loop response properties and closed loop end effector compliance.