绳索-弹簧机构工作空间分析

对于绳索牵引并联机构,因绳索只能承受拉力而不能承受压力,因此完全约束的n自由度绳索牵引并联机构至少需要由n+1根绳索来驱动,冗余驱动会导致成本增加,绳索拉力求解复杂。绳索牵引并联机构中,在末端执行器与机架之间选择适当位置引入弹簧,构成绳索-弹簧机构,由弹簧来提供被动力,则可以实现绳索驱动器与自由度数目相同的可控绳索-弹簧机构。以平面3根绳索1根弹簧机构为例,建立模型,求解可行工作空间,分析弹簧参数对绳索-弹簧机构可行工作空间的影响,采用遗传算法对机构构型进行优化,并对比分析优化前后的工作空间指标。结果表明,绳索-弹簧机构在构型优化选择适当的弹簧参数后,可以显著改变工作空间及其质量,为后期规划动平台的运动轨迹提供参考。

Analysis of the Workspace of the Cable-spring Mechanism

Since cables can only pull but not push, the cable-driven parallel mechanism (CDPM) with n degrees of freedom requires at least n+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.