Abstract: Based on the inverse kinematics equations, some general results on the velocities and accelerations of wires used for motion trajectory planning of 6-DOF wire-driven PKMs have been addressed, which show that the value of the velocity of a wire is always less or equal to the value of velocity of the respective moving platform attachment point, and the value of a plus wire acceleration is always not greater than the projection of the respective attachment point acceleration on the tensio direction. A criterion almost suitable for any trajec-tory in the workspace to calculate the tension of wires is used. A 6-DOF CRPM C Completely restrained positioning mechanism with a compact size has been introduced to demonstrate the kinematic characteristics of wires with the objective that spatial helical shaped trajectory can be realized by the end-effector. The results of trajectory planning are obtained to illustrate the velocities, accelerations and tensions of wires, and prove the correctness of the general results obtained; and moreover, the tension of some wires changes slightly, however, the tension of the other wires changes greatly. The results offer some data for further motion scheme control of this manipulator. Also, the method of motion trajectory planning proposed is applicable for general 6-DOF wire-driven PKMs.

Key words: 6-DOF, Motion trajectory planning, PKM, Wire-driven