Position Encoder Analysis and Low Delay Control for a Medical Robot with Six DoFs

Medical robots are in great demand for orthopedic surgery. The robotic control could be divided into two layers, the top layer and the bottom layer (also called joint control). However, how to improve the dynamic performance of joint control is still a challenging issue. Traditional PID control and PID-based sliding mode control are commonly used methods for the joint control of medical and industrial robots. In this paper, the proposed joint control is based on dynamic compensation. Dynamic compensation includes inertia and friction. The joint control diagram includes PID, sliding mode control, and adaptive dynamic compensation as a module unit. The design of the proposed joint control method could overcome the disadvantages of model uncertainty and dynamic disturbances and improve robot dynamic performance. Additionally, since control feedback is based on the joint position encoder, position encoder analysis is included in this paper. The dynamic performance of the proposed joint control was tested on the six-DoF medical robot, and the indexes of rising time, task space tracking, and contact space tracking were adopted to evaluate the dynamic performance. The experimental results show that the proposed control method has a much smaller rising time than the commercial controller product. The control proposed in this paper realized low delay control and improved the dynamic response of the control.