With the advantages of simple structure, low power consumption, high ratio of load to self-weight, and good flexibility, the cable-driven robots are especially suitable for medical instruments and home service. Due to the alignment of cables, there is a problem of motion coupling between the manipulator joints, leading to the degradation of control accuracy. Moreover, the hysteresis and the dead zone of the cable driving unit make it difficult to control the joint accurately. To effectively solve above-mentioned motion-coupling problem, a novel motion-decoupling mechanism is proposed and investigated. An experimental setup is established to verify the kinematic decoupling characteristics. Based on the ''static friction + Coulomb friction'' model, the friction model is established and verified. Thus, studies on the friction model have provided theoretical basis for the accurate force coordinated control of the cable-driven system.
The joint coupling relationship was studied aiming at the motion coupling among multi cable-driven robot joints. A novel motion-decoupled mechanism is proposed and investigated. Two driving cables of distal joint traverse the modular in a specific routing. As a result, cables will wind and unwind at a certain angular along the groove in the following wheel. This design can effectively compensate the length change of cables during the rotating moving of proximal joint. Afterward, a 2–degree-of-freedom cable-driven manipulator platform using this motion-decoupled modular was set up. The verification experiment has shown a productive performance in realizing motion independence. Then, a new robust controller using time-delay estimation and fuzzy algorithm is proposed for the decoupled cable-driven manipulator. Thanks to time-delay estimation and fuzzy algorithm, the proposed controller is model-free, precise and easy to use under practical applications. Finally, contrast control experiments have been performed, and the result illustrates the superiority of the proposed control strategy.
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