Integrated Kinematic Modeling of Reconfigurable Parallel Robot with 3T/3R Motion Patterns

Reconfigurable parallel mechanisms have more than one motion pattern and facilitate complex and compound manipulations. However, it is still a challenge to describe all the motion patterns by an integrated expression, which leads to difficulties in the analysis of transformation process. Furthermore, performance model of each motion pattern is always constructed individually in spite of their coupled relationship. In this paper, a reconfigurable parallel robot with spatial translational (3T) and rotational (3R) motion patterns is presented for on-orbit manipulation of cabins, including target capture, racemization, screwing and plugging. The integrated topology description, transformation process and whole kinematic modeling of this robot are investigated in-depth. Firstly, the topologies of two motion patterns are described in finite screw format and combined by defining a transformation factor. In this way, the transformation process is analyzed algebraically. Then taking advantage of the differential mapping of finite and instantaneous screws, the Jacobian matrix is derived from the motion equations directly. Finally, a numerical example is given to show the on-orbit manipulation process of the reconfigurable robot, involving inverse kinematics and workspace analysis. The method proposed in this paper could connect the topologies under different motion patterns algebraically, which facilitates to investigate the motion and performance of reconfigurable parallel mechanisms as a whole.