Abstract: The effects of actuator disposition and redundant actuation on performance of the 3-DOF Tricept parallel mechanism are analyzed. For eighteen redundant and non-redundant actuating modes, the corresponding Jacobian and stiffness matrices are educed. According to the distributing properties of the kinematic dexterity, the maximal and minimal stiffness indices on mid section of mechanism’s positional workspace, the performance characteristics of tricept mechanisms with different actuator disposition and redundant actuation are contrastively investigated. As a result, the actuating modes which can simultaneity enhance the kinematic dexterity and stiffness characteristics are presented. The investigation shows that redundant actuation has less effect on dexterity and stiffness of the tricept parallel mechanism in which the sliders of UPS sub-chains are adopted as the driving joints, but it can evidently improve kinematic dexterity and stiffness characteristics of the mechanisms with actuating rotational joints. Thus, the redundant actuators can be added to the Tricept mechanism, in which the rotational joints of UPS sub-chains are used as the driving joints, to acquire better mechanism performance.

Key words: Actuator disposition, Performance comparison, Redundant actuation, Tricept parallel mechanism