Motion decoupling for cable-driven serial robots based on a noncircular pulley

Cable-driven serial robots have gained significant growth because of their compact size and low inertia characteristics. However, one major problem of cable-driven serial robots is motion coupling issue that one joint motion will cause movement of the other joints, resulting in a complicated control. In this paper, we proposed a novel method to decouple the joint motion by using a noncircular pulley. The length change of driving cables on a joint pulley due to the coupling issue is compensated by the noncircular pulley. The calculation process of the pulley profile, the mechanical design of the decoupling system, and control system of the cable-driven robot prototype are introduced. Experiments have been conducted to evaluate the performance of the motion decoupling method. The results demonstrate that the noncircular pulley can solve the motion coupling issue by keeping the cable length nearly constant with small errors.