Direct adaptive force feedback for haptic control with time delay

Haptic devices convey force measurement to a human operator, who closes the control loop by moving the haptic hand controller. In surgical robotics, haptics dramatically improve the quality of the teleoperation. However, time delays can accumulate in the closed loop when haptic hand controllers are located in a different room (or even a different city) than the robot. When puncturing through tissue or hitting a solid surface, the commanded movement or force will be too large during the time delay, until the surgeon feels the effect and can pull back on the control. This paper proposes using a nonlinear adaptive inner-loop control scheme for haptic master/slave systems, to reduce effects of time delay. A Lyapunov analysis ensures stability. Simulation results show the improved response for a one-degree-of-freedom system in a highly nonlinear environment.