On the Kinematic Analysis of a Spatial Six-Degree-of-Freedom Parallel Manipulator

In this paper, a novel spatial six-degree-of freedom parallel manipulator actuated by three base-mounted partial spherical actuators is studied. This new parallel manipulator consists of a base platform and a moving platform, which are connected by three legs. Each leg of the manipulator is composed of a spherical joint, prismatic joint and universal joint. The base-mounted partial spherical actuators can only specify the direction of their corresponding legs. In other words, the spin of each leg is a passive degree-of-freedom. The inverse pose and forward pose of the new mechanism are described. In the inverse pose kinematics, active joint variables are calculated with no need for evaluation of the passive joint variables. To solve the forward pose problem, a much simpler method compared to the traditional method is introduced. Closed form relations for the inverse and forward rate kinematics are proposed. Finally, two sets of singular con guration of the newly introduced manipulator with di erent natures are obtained.