Cable suspended robots: feedback controllers with positive inputs

Cable-suspended robots are structurally similar to parallel actuated robots but with the fundamental difference that cables can only pull the end-effector but not push it. From a scientific point of view, this feature makes feedback control of cable-suspended robots a lot more challenging than their counterpart parallel-actuated robots. This paper describes the structure of two closed-loop asymptotic controllers that assure positive cable tensions. These controllers are based on the Lyapunov design technique and feedback linearization, respectively. The effectiveness of the approach is demonstrated through simulation and experiments on a six degree-of-freedom cable suspended robot.