A modular sliding mode controller for cooperative closed-chain manipulators with uncertain dynamics

This article presents a decentralized sliding mode control scheme for the complex problem of simultaneous position and internal force control in cooperative multiple manipulator systems. The proposed controller is composed of a sliding mode control term and a force robustifying term to simultaneously control the payload's position/orientation as well as the internal forces induced in the system. This is accomplished independently of the manipulators dynamics. Unlike most controllers that do not require prior knowledge of the manipulators dynamics, the suggested controller does not depend on fuzzy logic inferencing and is computationally inexpensive. Numerical experiments confirm the controller's robustness in the face of varying unknown system's dynamics. The payload's position/orientation and the internal force errors are also shown to asymptotically converge to zero under such conditions.