Dynamic Model-Free Control Approach for Fully Constrained Cable-Driven Parallel Robots: Prescribed Control Range

Cable-driven parallel robots (CDPRs) utilize cables instead of rigid linkages. Considering the complexity of the cable dynamics and the positive constraint on the cable tension, the precise tracking control of CDPRs is highly challenging and of great significance. The positive tension distribution (PTD) for the CDPRs has been conventionally done via redundancy resolution methods which are optimization based in nature. Hence, the unpredictable worst-case computation time of these methods limits their practical applications. Moreover, a performant tracking control traditionally requires an exact knowledge of the cable dynamics which is practically hard to obtain for CDPRs due to their complicated dynamics. To remedy these challenges, we propose a real-time dynamic model-free PTD scheme for the redundant CDPRs. This control structure brings two major benefits to the control of redundant CDPRs. First, the elapsed time of the analytic proposed method is considerably less than that of the iterative literature methods. Second, high-precision tracking accuracy is achieved despite the challenging cable dynamics and the presence of external disturbance. It is owing to the dynamic model-free structure of the controller. Eventually, the performance analysis is assessed through the simulation and experiment, verifying the efficiency of the proposed method.