Abstract:

：Since cables can only pull but not push, the cable-driven parallel mechanism (CDPM) withn degrees of freedom requires at leastn+1 cables to fully constrain the end-effector. However it has been shown that the redundant cable leads to increased costs of actuator and results in the complexity of solving the cable force. When springs are added properly into the CDPM between the end-effecter and the base frame, it constitutes a cable-spring mechanism, which can achieve the same number of actuators with cables to fully constrain the end-effector of the cable-spring mechanism. The static model of a planar cable-spring mechanism with 3 cables and 1 spring is established, and the workspace of different configuration of the cable-spring mechanism is calculated. The effect of spring’s parameters on the workspace of cable-driven parallel mechanism is analyzed, and a genetic algorithm is employed to optimize the structure and the spring’s parameters. The indicators of workspace before and after optimization are analyzed. The results indicate that the cable-spring mechanism with an appropriate configuration parameters of the springs, can significantly alter the quality of the workspace and provide an increased workspace for the trajectory planning of the end-effector.

Key words: genetic algorithm, quality of workspace, workspace, cable-spring mechanism