Theoretical and experimental studies of compliant motion control for robot manipulator

The fact that most robot manipulators already have some kind of tracking controllers and, however, studies of the force controllers are more limited is the motivation behind our approach. A nonlinear approach is presented here in the input/output sense for the stability of robot's compliant motion. For stability, we show that there must exist some compliance either in the robot or in the environment. According to the `sufficient' stability criteria, smaller compliance either in the robot or in the environment leads to a narrower stability range. We verify the sufficient stability condition via experiments using a Cartesian manipulator. Some experiments have been performed to demonstrate that the stability criterion is only a sufficient condition. If the condition is satisfied, the stability is guaranteed. However, if the condition is violated, no conclusion can be made. Finally, by knowing disturbance-compliance function, environment dynamics and robot dynamics with tracking controller, we can choose a compensator to shape the contact force if the sufficient stability condition is satisfied.