Instantaneous Reaction and Vibration Suppression Using Two-Degree-of-Freedom Admittance Control with H_∞ Feedback Controller in Surgical Training Simulator with Chiseling Operation

Abstract

Surgical training simulators with virtual reality have been developed to enable surgeons to efficiently acquire and improve their surgical skills. In hard tissue surgery, the surgeon uses a chisel and mallet to cut a bone or tooth with large and instantaneous forces. In the previous study by present authors, to represent the force sensation of the cutting operation in the virtual training simulator, we constructed the force display device using the ball-screw mechanism to obtain high stiffness and display the large force. Additionally, we applied the two-degrees-of-freedom (2DOF) admittance control to react instantaneously to the impact force by pounding with the mallet. The feedback controller of the 2DOF admittance control is required to increase the high-frequency gain for improving the responsiveness of the force display device. However, the vibrational mode of the force display device can be excited by increasing the controller gain. Therefore, this study develops the design approach of the feedback controller using the H_∞ control in the 2DOF admittance control system, which can be systematically constructed to reduce the vibrational mode and react instantaneously in the force display device. The efficacy of the proposed force display control system is verified through the virtual experience of the free movement and the hard contact operations.