Multiple Working Mode Control of Robotic Operations on Mechanisms With Unmodelled Constraints With Online Mode Switching

Robotic operations such as opening doors in an unstructured environment pose a challenge for robot control due to unmodelled constraints. In this article, a multiple working mode approach is proposed to control a mobile serial robot manipulator to perform operations on mechanisms with unmodelled constraints. The multiple working mode control switches the working mode of a number of active joints during the operation to relax the problem of over-actuation of the constrained robot manipulator when modeling errors cause excessive internal and external reaction forces. Three practical criteria are derived for the assignment of active and passive control modes; two based on the coordinate partitioning method for multibody dynamics, and another based on minimizing task friction forces. The proposed control method has been implemented on a mobile reconfigurable robot, performing constrained motion along an elliptical trajectory, similar to a door-opening task. Simulation and experimental results are presented to show the effectiveness of the proposed control approach.