Variable Admittance Control Method Of Rope-driven Joint Replacement Robot

At present,there are hundreds of millions of patients with osteoarthritis in the world.With the advent of my country's aging population,there are more than 100 million patients with osteoarthropathy in China.Due to the low precision of osteotomy and bone grinding in artificial joint replacement surgery,there are problems such as slow postoperative recovery process and high complication rate.In order to improve the accuracy of the operation,people have introduced the precise control of the robot and the precise positioning of the navigation system into the clinical operation,and carried out the research of the knee replacement surgery robot technology.Different from the master-slave control mode adopted by the Da Vinci surgical robot,the joint replacement assisted surgical robot mainly adopts the working mode of man-machine collaboration.The safety and compliance of the human-robot interaction control method is the key to the clinical development of joint replacement surgical robots,and it is also a current research hotspot.This paper aims to improve the flexibility of joint replacement assisted surgical robots by analyzing the characteristics of rope-driven robots and research on variable admittance control methods.For this reason,firstly,the influence of the rope drive on the joint angle error is analyzed,and a feedforward compensation control method based on the Stribeck friction model is proposed to improve the position tracking accuracy of the joint when the joint rotates at a low speed.Then through kinematic calibration,the D-H parameters of the robot are corrected,and the absolute positioning accuracy of the joint replacement surgery robot is improved.Finally,a variable admittance control method based on the electromyographic signal of the human arm and a compliance control method based on reinforcement learning are proposed to improve the compliance of the robot in human-robot interaction.The main research contents of this article are detailed as follows:In order to improve the control accuracy of the single joint itself,firstly,the influence of the rope drive on the angle error of the joint is analyzed.Secondly,the kinematics of the robot is analyzed using the space motion spin method,and the Jacobian matrix is derived.At the same time,the maneuverability of the robot in a singular configuration is analyzed.Finally,a feedforward compensation control algorithm based on the Stribeck friction model is proposed to reduce the impact of joint nonlinear friction on the accuracy of joint control.The simulation experiment shows that the position tracking accuracy of the joints is significantly improved when the joints rotate at low speeds.In order to improve the positioning accuracy of the joint replacement robot and reduce the influence of geometric parameter errors,a kinematics calibration algorithm based on the differential error model is proposed.After verifying the validity of the calibration algorithm through the MATLAB simulation experiment,the kinematic parameter calibration of the robot is completed by using the NDI measuring equipment and the optical target installed at the end of the robot.The absolute positioning accuracy of the robot is improved by 59.6%.In order to take into account the rapidity of the free movement of the machine and the stability of the surgical operation,a variable admittance control method based on the electromyographic signal of the human arm is proposed,and a human-robot interaction experiment that simulates the real surgical environment is carried out to improve the operator's human-robot interaction experience.In order to improve the motion compliance of the drag task,a variable admittance compliance control algorithm based on reinforcement learning is proposed,a simulation experiment environment is built,and the effectiveness of the algorithm is verified.