Hybrid force-motion control of coordinated robots interacting with unknown environments

This paper presents a unified framework for system design and control in cooperative robotic systems. It introduces a highly general cooperative system configuration involving any number of manipulators grasping a rigid object in contact with a deformable working surface whose real physical parameters are unknown. Dynamics of the closed chain mechanism is expressed based on the object´s center of mass, and different robust controllers are designed for position and force control subspaces. The position controller is composed of a sliding mode control term, and involves the position and velocity feedback of end-effector, while the force control is developed based on the highest derivative in feedback methodology. The force controller does not use any derivation of the force signal as well as the internal force controller induced in the system, and it appears to be very practical. Simulation results for two three joint arms moving a rigid object are presented to validate the theoretical results.