Research On Position Control And Micromanipulator External Force Sensing For Invasive Surgical Robot

Compared with traditional surgery,robot-assisted minimally invasive surgery has the advantages of being able to overcome the shortcomings of traditional surgery,allow doctors to control the instrument precisely,can improve the efficiency and success rate of surgery,reduce the pain of patients with surgery,shorten postoperative recovery time,expand traditional surgery range of application,and can perform the remote operation remote surgery,etc.Minimally invasive robotic surgery has been widely recognized in the surgical field.Minimally invasive surgical robots are gradually becoming a hot research field in medical robot research.Because of the special configuration of the minimally invasive surgical robot slaver system instrument arm(which does not satisfy with the Pieper criterion),It is difficult to obtain the precise inverse kinematics analytical solution;Due to the micro-instrument size and usage requirements,it is impossible to integrate the position feedback element in the micromanipulator and cannot perform closed-loop position control.These seriously affect the control accuracy of the surgical robots.Meantime,the lack of micromanipulator force sensing,making the operation process is cumbersome,and the doctor cannot apply accurate operation force to perform fine operation.Therefore,it is of great significance to study the key technologies of the precise position control and force detection of surgical robots for the development of the minimally invasive robotic surgery.This dissertation is supported by the National Natural Science Foundation of China under Grant 61203358,the Natural Science Foundation of Heilongjiang Province under Grant F2015034,and the Key Project of Central University Basic Scientific Research Project under Grant HEUCFZ1214.The content of this dissertation focuses on two key aspects: precise position control and micromanipulator force detection for minimally invasive surgical robots.Include four key technical points: the acquire method of the inverse kinematics analytical solutions for surgical robot slaver system instrument arm,closed-loop control of micromanipulator,variable parameter dynamic modeling and identification of micromanipulator,and external forces indirect detection method of micromanipulator.The specific contents of this dissertation are listed as follow:Firstly,a brief introduction of the minimally invasive surgical robot slaver system has been made.The traditional DH method is used to model the positive and inverse kinematics of the laparoscopic arm and the simulation analysis is completed to verify the correctness.A new kinematics modeling method named adjacent joint axes establishing-order rearrangement method is proposed for the question of acquiring instrument arm inverse kinematics analytical solution.The different robot configurations have been analyzed to give the applicable conditions of the method.The new method is used to model the kinematics of the instrument arm and get the exact analytical solution of the inverse kinematics.The correctness and effectiveness of the method are verified through simulation analysis.Secondly,In order to achieve the precise position control of the cable-driven micromanipulator,the closed-loop control strategy and method of the micromanipulator position are studied;the driven principle of the 4-DOF cable-driven micromanipulator is designed based on the asymmetry mechanism of the motor-spring.The overall kinematics(the relationship between the motor rotation angle and the position of the micromanipulator)are analyze by considering the joint coupling characteristics,and given the closed-loop control strategy of the micromanipulator based on the angle estimator.The single joint principle prototype of the micromanipulator is set up,the joint angle estimator of the single joint principle prototype is designed based on the cable-driven mechanism,and obtained the accurate model parameters through experimental identification,simplification and correction.Closed-loop experimental study of the position is performed by considering the output of the joint angle estimator as the feedback signal,and compared with the traditional open-loop control method to verify the correctness and effectiveness of the method.The 4 DOF cable-driven micromanipulator position closed-loop control performances are tested by simulation analysis.Thirdly,the wrist dynamic model of the micromanipulator is established,and the correctness of the wrist dynamics model is verified by Matlab and Adams simulation,and then established the dynamic model of micromanipulator system by combining the model of the drive mechanism.The dynamic model of the whole single-joint principle prototype is established based on the modeling of the subsystem of the single-joint principle prototype system.The parameters of the joint dynamic model is identified by the method of combining the nonlinear model method and genetic algorithm(GA),and compared the results with the traditional weighted least squares(WLS)method.A linear parameter variety model(LPV)of the second-order state space for the joint dynamic model is established for the single-joint principle prototype.The model is treated as a linear time-invariant(LTI)system for a small period of time,and the genetic algorithm(GA)and weighted least squares(WLS)method are used to realizes the parameter identification,and the correctness of the model is verified through experiments.The research can be the foundation for force control and force interaction of the micromanipulator.Finally,a strategy for estimating the three-dimensional external force and clamping force of the micromanipulator was proposed to solve the problem of micromanipulator force detection.Taking the single-joint principle prototype as the research object,the motor-reducer-reel damping model and the cable tension model are established,The external force estimator is designed by combining the motor-reducer-reel damping model,cable tension model and disturbance observer.The parameters of the motor-reducer-reel model and the cable tension model are obtained by the method of experimentally identification.Then the performance of the external force estimator is tested by the single joint principle prototype external force detection experiment.The results show the correctness and effectiveness of the method.The study can provide the technical basis for the further development of 4-DOF micromanipulator with force detection capabilities.