Kinematic analysis of a 3-CS in-parallel platform mechanism with three-degree-of-freedom

With the development of parallel mechanisms research, spatial imperfect-DOF parallel mechanisms especially some constrained 3-DOF parallel mechanisms have received more attention for the advantages of their simple structure, easy control and low cost. In this paper, a novel model of constrained 3-DOF parallel manipulator-3-CS in-parallel platform mechanism is introduced firstly. The instantaneous possible motion characteristics for this mechanism are analyzed in detail by applying the screw theory. In addition, the first order kinematic analysis of the 3-CS mechanism is discussed thoroughly, which involves deriving three motion constraint equations for the output motions of the manipulator and formulating the kinematic influence matrix (also called Jacobian of the mechanism) reflecting the velocity relationship between three independent input motions and three independent output motions in a closed form. At last, the closed-form solutions are developed for both the inverse and forward position kinematics.