Adaptive backstepping control for sensor-less haptic joysticks with uncertainty parameters

As a manipulation terminal for a teleoperated system, a joystick requires force sensors to accurately reproduce the haptic information, resulting in large and expensive haptic joysticks. Moreover, the actuator of the haptic joystick usually contains uncertain parameters related to its DC servo motor, making accurate haptic reproduction control a challenge. This study proposes an adaptive haptic control scheme based on the backstepping method for a haptic joystick system with unknown parameters and unmeasurable disturbances without using force sensors. In the scheme, the joystick end force is considered an unknown disturbance of the DC motor. A universal model of the joystick system actuator, i.e., a DC servo motor, and the dynamic model of the joystick are established. The control law is then derived on the basis of the established model. The stability of the closed-loop system is demonstrated analytically on the basis of the Lyapunov function. Furthermore, numerical simulation results verify the effectiveness of the proposed control scheme.