Position/Force Control System Stability of Robotic Manipulators

Based on a simple 2-DOF manipulator,we analyse the instability of Raibert andCraig's hybrid position/force controller and develop two methods to stabilize theforce control system:force derivative feedback and position feedback in force com-manded directions.For a general manipulator,we propose an unified position/forcecontroller,the effectiveness of which is demonstrated by simulations.We also givesome important conclusions on force controller design.