Direct inverse control of cable-driven parallel system based on type-2 fuzzy systems

This paper investigates the control problem for a cable-driven parallel system by using type-2 fuzzy logic systems (FLSs). The considered cable-driven parallel system is divided into six subsystems, and corresponding to each subsystem, a direct inverse controller is developed, which is expressed by an interval type-2 fuzzy nonlinear autoregressive exogenous (NARX) model. To determine the parameters of the inverse controller, the monotonic property of the fuzzy NARX model is proved. According to this property and based on the input–output training data, the heuristics and prior knowledge, the antecedent parameters of the inverse controller are determined. Furthermore, the consequent parameters are computed offline via a constrained least squares algorithm. By applying the proposed type-2 fuzzy direct inverse control scheme to the cable-driven parallel system, experiment results show that the proposed control method can not only level the top surface of a payload, but also balance the tensions of the four cables, and finally can ensure the safety of the payload.