ADAPTIVE SUPER-TWISTING-LIKE SLIDING MODE CONTROL WITH PRESCRIBED PERFORMANCE FOR ROBOT MANIPULATORS

Abstract

In order to minimize the involuntary tremor of surgeon’s hands, the surgical robots are widely applied in the minimally invasive surgeries. However, unlike ordinary robots, the surgical robots require that the manipulator has high precision and strong anti-disturbance ability. Besides that, the manipulators of surgical robots must be able to move smoothly and respond quickly to the surgeon’s instructions during conducting tasks. To solve aforementioned problems, this paper describes a super-twisting sliding mode controller for the robot manipulator. The basic law is combined with the adaptive term to overcome the unknown disturbances and structural uncertainties, and with the prescribed performance allowing to influence the error dynamics. To ensure the robot system has good transient and steady-state performances, the transformation function of tracking errors is devised. Through using transformed errors, we attain the surface of sliding mode and propose a modified structure of traditional super-twisting algorithm. Considering the derivative of lumped disturbance has unknown boundary, a novel adaptive law is derived for the modified super-twisting sliding mode control which does not require the boundary of disturbance. Simulation experiments showed that the proposed control algorithm not only improves the tracking performance of surgical robot manipulators, but also facilitates the parameter tuning of controller. The devised robot manipulators are also potentially applicable to telesurgery where the steady-state response of surgical robots is required.