According to the structure character of the passive sub-chain of the 3TPS-TP parallel mechanism, the kinematic constraint equations of the movable platform are established, based on which the closed-form inverse kinematics formula of the parallel mechanism are presented. Through parting the spherical joints of the active sub-chains and using the force and moment equilibrium of both the active sub-chains and passive sub-chain, the constraint forces acting on the parted joints are determined. Subsequently, the analytic expressions of the actuator driving forces are derived by means of the force equilibrium of the upper links of active sub-chains.
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