KINEMATICS ANALYSIS OF A NOVEL 2R1T PARALLEL MECHANISM

In this paper, a parallel mechanism with two rotational degrees of freedom (DOF) along X- and Y-axes and one translational DOF along the Z-axis is present. At first, a special geometric solid with the property of 2R1T is proposed. Then, a novel 2R1T parallel mechanism which embodies the same property of 2R1T is designed with structure design. The special geometrical nature enables the mechanism to be operated without parasitic motion. The symmetrical structure will increase the mechanism balancing and manipulability. Several important issues including direct kinematics, inverse kinematics, Jacobian matrices, stiffness, transmission coefficient, good transmission workspace and global composite performance index (GCPI) of the mechanism are investigated with screw theory and vector method. In addition, the base radii are optimized for the best GCPI. Finally, the novel mechanism is developed as a forearm rehabilitation of the upper limb rehabilitation system.