Inverse kinematic and dynamic analysis of a 3-DOF parallel mechanism

This paper presents the inverse kinematic and dynamic analyses of the 3UPS-UP parallel mechanism with three degrees of freedom. For inverse kinematics, the kinematic constraint equations of the movable platform are established according to the structural character of the passive sub-chain, based on which the closed-form inverse kinematic formulas of the mechanism are obtained. In inverse dynamic analysis, the mechanism is decomposed into two parts through cutting the three spherical joints connecting the base and movable platforms, then the constraint forces acting on the parted joints are determined using the force or moment equilibrium's of both the active and passive sub-chains. Finally, the analytic expressions of actuator driving force are derived by means of the force equilibrium of the upper links of active sub-chains.