Robust control of position and force for robot manipulators involving both free and constrained motion

The problem of the robust control of the position and force of robot manipulators during free and constrained motion is addressed. The issue of collision avoidance during the transition between free and constrained motion is also examined. Using the proposed control scheme, it is shown that the controller can be automatically switched when a free moving robot comes in contact with a rigid environment, or vice versa. A stability analysis and a numerical example of a three-degree-of-freedom robot performing free and constrained motion are presented. It is shown that the proposed controller is robust with respect to the system parameter uncertainties