Sliding Mode Control for a Surgical Teleoperation System via a Disturbance Observer

To obtain accurate trajectory tracking with robustness and faithful force feedback in a practical application, a sliding mode controller (SMC) combined with a compensation controller based on a nonlinear disturbance observer (DOB) is proposed. The DOB estimates the disturbances arising mainly from the uncertain dynamic model of a surgical manipulator, frictional forces and external interaction forces, and compensates for these disturbances in the control law. Accordingly, it alleviates the chattering problem caused by the SMC and improves tracking performance. The surgical teleoperation system using the proposed SMC-DOB is proved to be asymptotically stable using Lyapunov theory. The simulation and experiment results show that the surgical manipulator with the SMC-DOB can better track the trajectory of the master even in the presence of disturbances and the interaction forces between the instrument and the patient's tissues are faithfully presented to the surgeon.