Workspace analysis and optimal design of cable-driven planar parallel manipulators

A cable-driven parallel manipulator (CDPM) possesses a number of promising advantages over the conventional rigid-link manipulators, such as simple and lightweight mechanical structure, high-loading capacity, and large workspace. However, the formulations and results obtained for the rigid link manipulators cannot be directly applied to CDPM because of the unilateral property of cables. This paper focuses on the workspace analysis and optimal design of a specific type of CDPM, i.e. a completely restrained symmetric cable-driven planar parallel manipulator (CDPPM). The tension plays a key role in building up the workspace. In the analysis, performance criteria such as tension bound and stiffness condition are considered to construct the feasible workspace. Moreover, simplex search method is employed to obtain the optimal feasible workspace with respect to the locations of the connecting points and suspending points. Computation results have shown that the optimal workspace can be always obtained at configurations where either the base or the platform is degenerated to a line.