Point-to-Point Trajectory Planning And Dynamic Control Of Cable-driven Parallel Manipulators

Traditional parallel manipulators have small workspace and complicated mechanical structures. In order to overcome these drawbacks, cable-driven parallel manipulators (CDPMs) have simpler structures with cables instead of rods, which have low mass, low cost, large workspace et al. However, cables bring new challenges to parallel manipulators. Because cables can only provide tension, i.e. cables are unable to push the moving platform, it becomes more complicated to study CDPMs. Thus, our research includes dynamic trajectory planning, stiffness analysis and dynamic control of CDPMs. The main work is summarized as follows:(1) Because CDPMs should ensure positive tensions and avoid cables slackness all the time, the traditional trajectory planning methods cannot be applied to CDPMs. In this dissertation, a new combined planning method with S-trapezoid curve is proposed for the point-to-point motion of a planar 2-DOF CDPM, and the unilateral constraints on cable tensions are computed according to the dynamic model. CDPMs with the dynamic trajectory planning methods work in the dynamic workspace, having large range of movement. Furthermore, performances of the combined planning method with S-trapezoid curve are verified on a 2-DOF CDPM in Matlab.(2) Because cables are easy to be bent and stiffness is weaker than the rigid structure, the stiffness analysis of CDPMs becomes more important. Therefore, the effect of different trajectories on stiffness and the stiffness matrix of the dynamic model are studied on a 6-DOF CDPM in this dissertation. The point-to-point straight trajectories and sine trajectories are planning with three different methods such as S-type velocity profile, quintic polynomial and trigonometric function. Meanwhile, the effect of accelerations on stiffness is analyzed for the three different methods.(3) The dynamic models in orientation workspace and joint workspace are built for a 6-DOF redundant CDPM with 8 cables. The internal forces among the cables and a PD controller are denoted in the dissertation. The dynamic control method is implemented on the 6-DOF CDPM in the experiment and performances of the PD controller are verified with two sets of experimental results. Furthermore, the software application for the experimental equipment is designed and generally introduced.