REEDMAN, A.V.C. and BOUAZZA-MAROUF, K., 2004. An actively constrained two degree-of-freedom manipulator for passive deployment applications. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 218(2), pp. 63-74.
A two degree-of-freedom manipulator using actively constrained revolute joints is presented in this paper. Each revolute joint drive mechanism consists of two motor-driven worms coupled to a single worm wheel. A mathematical model of the manipulator system is used in order to develop a computed-torque control algorithm. Experimental results show that the position of the end-effector can be successfully controlled to track a path generated from a user-input force command signal while cancelling backlash at the gear interface. This system has been designed for the purpose of following a predefined path under the direct physical control of the user. The joint mechanism and control strategy used in this paper allow for backlash to be continuously cancelled. The safety of the user is ensured by enabling joint motions only if a user force is applied, and this force is in a direction that allows the controller to restrict joint motion along a predefined path.