ESO-Based Antisaturation Motion Control for Cable-Driven Continuum Robots

High precision motion control is the key to complete the refined operation tasks for cable-driven continuum robots. However, the existence of model inaccuracy and actuator saturation pose great challenges to the high precision motion control of cable-driven continuum robots. This article proposes an extended state observer (ESO)-based antisaturation control scheme for cable-driven continuum robots with consideration of unmodeled dynamics and actuator saturation. First, the dynamic model of the cable-driven continuum robot is derived. To facilitate the design of the overall control scheme, the driving input dimension of the dynamic model is reduced from three to two based on the principle of space rotational symmetry. Taking the actuator saturation into consideration, the saturated dynamic model of the cable-driven continuum robot is further developed. Then, an ESO is designed for the saturated cable-driven continuum robots to estimate the unmodeled dynamics, and an auxiliary system is proposed to handle the actuator saturation. Hereby, a novel control law based on the ESO and auxiliary system is put forward to compensate for estimated unmodeled dynamics and actuator saturation. Moreover, the stability of the closed loop system is analyzed by Lyapunov method, and a practical and effective tuning method is provided to optimize the parameters of the proposed control scheme. Finally, comparative simulations and experiments are conducted to verify the effectiveness of the proposed control scheme.