Adaptive Robust Impedance Control for an Ear Surgical Device with Soft Interaction

The required suitably soft-contact interaction in certain surgical device applications brings great challenges on the force and position control because the soft-contact environment is nonlinear, viscoelastic, and inhomogeneous. In this paper, a novel adaptive robust control approach, namely adaptive integral terminal sliding-mode-based impedance control (AITSMIC), is formulated to simultaneously regulate and control the position and force for a piezo-actuated ear surgical device with soft interaction. Firstly, the target impedance's steady-state performance is discussed by utilizing the nonlinear Hunt-Crossley model. To achieve the desired impedance, an integral terminal sliding manifold based on the auxiliary variable containing the impedance error is proposed to improve tracking performance and obtain the required finite-time convergence. Furthermore, an adaptive law is designed to get rid of system nonlinearities, uncertainties and disturbances, and to retain high robustness. The stability of the proposed control system is proven via the Lyapunov theory. Significantly, implementing the AITSMIC is straightforward, where only essentially one uniform controller is applied. Finally, several experiments are conducted to evaluate the effects of associated impedance parameters, verify the force tracking performance and validate the suitably practical application of AITSMIC on the procedure of ear surgery with soft interaction. The results show that excellent tracking performance and successful operation are achieved by the proposed controller.