Kinematics analysis of a four degree-of-freedom parallel manipulator

In this paper, a 2-RPU&2-SPS parallel mechanism is studied. Firstly, the number and property of degrees of freedom of the mechanism are confirmed base on the screw theory, this mechanism can realize two rotational and two translational movement. Secondly, the position analyses are invested. For the inverse position analysis, the only expressions are obtained in an explicit form, and the forward position problem is solved by calculating a set of non-linear equation system. Then, the singularity analyses of the mechanism are acquired by Jacobian matrix of the parallel manipulator. Finally, the kinematic transmission performance analyses of the mechanism have been analyzed by defining transmission efficiency coefficient between limbs. This work will provide the theoretical basis for prototype development and application of the mechanism.