Compliant Control Of Total Knee Replacement Robot Osteotomy Process

Total Knee Arthroplasty(TKA)was one of the most significant innovations in bone surgery in the 20 th century.The artificial joint prosthesis manufactured by 3D printing is currently the most reliable and effective method for treating osteoarticular diseases to replace the damaged knee joint.TKA surgery can effectively reduce the pain of patients with osteoarticular diseases and re-repair the normal physiological function of joints in patients.Total knee replacement osteotomy is the most time-consuming and tedious part of the operation steps,and the location accuracy of the osteotomy plane directly determines the installation accuracy of the prosthesis and to a large extent,the final quality of the operation.In this paper,a three-degree-of-freedom osteotomy actuator and an eight-degree-of-freedom knee replacement fixing brace are designed.The lateral axis stroke length of the special actuator is 127.34mm;Longitudinal axis stroke length: 127.65 mm.Working radius≥100mm,measured rated speed: 12.93mm/s,force feedback accuracy: 2.32%,and force feedback response time error: 0.03 s,which met the requirement of force feedback response time < 100 ms during the operation.The tool coordinate system was calibrated using the external reference six-point method,and the calibration results were good.The maximum projection error in the TCP calibration was 0.67 mm,which met the requirements of surgical bone cutting.And generates a bone cutting reference path based on the constraint of the virtual guide plate.In order to solve the error problem caused by the uncertainty of the relative position of the pendulum saw and the human leg bones and the stiffness of the human leg bones in the robot bone cutting process,an adaptive impedance control method was proposed,which can track the dynamic force in the bone cutting process of knee joint replacement surgery and further compensate the uncertainty of the bone stiffness.The contact force is used as the feedback force of the position-based impedance control,and the dynamic desired force is actively tracked in an uncertain environment.The impedance parameter is adjusted online through the tracking error,so that the adaptive impedance control is achieved.The stability and convergence of adaptive impedance control are proved by theoretical derivation.Through simulation and experiment,the position tracking and force tracking comparison between the constant impedance control and the adaptive impedance control are carried out.The result shows that this method has better force tracking effect than the constant impedance control.Finally,the experiment of knee joint replacement robot cutting bone from cadaveric specimen is performed.The experimental data results show that the force tracking and position tracking effects are good in the process of bone cutting.Compared with the traditional method,the non-bone area formed by the new bone cutting trajectory cutter is only 1.65% of that by the traditional method,which can achieve the compliance control requirements of the knee joint replacement robot.In order to realize that adaptive operation of the special bone-cutting pendulum saw,the data fed back by the six-dimensional force sensor at the end of the bone-cutting actuator is combined with the self-defined key of the handle,and the miniature linear servo drive is automatically controlled according to the fed back force value in the knee joint surgery process,so that the pow of the pendulum saw is adjusted.The final experiment shows that this method can realize the adaptive operation of the special bone-cutting pendulum saw well.