Hybrid Force and Position Control of a 4DOF Surgical Robot with Disturbance Observer

Abstract

The concept of using robot assistance in medical surgery is receiving more and more recognition throughout the world. Robot surgery can reduce the tremor of the surgeon, postoperative complications, and patient pain and in the same time increase operation dexterity inside the patients' body. One of the most important factors in the surgeon's robot is that, in spite of the friction between the tissue and the surgical instrument, it is necessary to be able to control the force and position with high precision. In this paper, path tracking for the surgeon's robot in the presence of friction between the tissue and the surgical instrument and the model uncertainty has been investigated. A disturbance observer is utilized to estimate the friction and then the estimated value is feedback for compensation. The considered surgeon's robot is the compact laparoscopic surgical robot, which prototype system was built at the University of Hawaii. In the simulation of the surgeon robot control systems, PID controller and computed torque method are compared. Moreover a stiffness estimator is utilized to determine the proper reference force.