Estimation of interaction force between tissues and a surgical robot instrument

Abstract

Robot-assisted telesurgery has many advantages for patients and surgeons such as less incision, bleeding, precise manipulations compared with existing open surgery. However, conventional surgical robot systems only offer unilateral position tracking from a master manipulator to a slave robot and force information is not available in commercial systems because of the difficulty of attaching force sensors at a surgical robot instrument. In the lack of force feedback, the surgeons are limited to dexterous manipulation during the operations. With this background, this thesis discusses force estimation methods interacting with tissues by using joint torque measurements of a surgical slave robot to convey force feedback to the surgeons. This thesis is divided into two parts. The first part is to design joint torque sensors using strain gauges which can be attached in a surgical slave robot as the driving joints to drive a surgical robot instrument. In addition, sensor performance was evaluated by comparing with a commercial torque sensor in a calibration device. Hence, it can be applicable to real surgical slave robot systems by avoiding constraints of attaching force sensors at a surgical robot instrument. The second part is to estimate the interaction force using joint torque sensors. The purpose of second part is to classify the interaction forces from the exerted torque at the driving joints of a surgical robot instrument. To obtain more accurate force information, the exerted torque of the driving joints was compensated by adequate dynamics of a surgical robot instrument which consists of rigid dynamics and the viscous and friction estimations. In addition, signal conditioning approach is suggested by tuning signals measured in the driving joints with the interaction force signals using low-pass filters, which is to intentionally induce signal delays. To verify the effects of compensations and tuning approaches, Test-kit was designed and manufactured as an expe...