Research On Combined Impedance-admittance Control Method Of Bone Grinding Surgical Robot

With the development of medical robotics technology,the clinical application and advantages of orthopedic surgical robots have gradually become prominent,becoming a research hotspot in the field of medical robots and medical equipment.At the same time,complex orthopedic surgery has put forward higher requirements for robots.Intelligent,minimally invasive and precise have become the development direction of orthopedic surgical robots.In robot-assisted orthopedic surgery,the interaction between robotic grinding tools and bone tissue,as well as the stability and compliance of human-machine interaction have a huge impact on orthopedic surgery.Therefore,in this paper,the impedance control is used to realize the stable grinding of the interaction between the tool and the tissue,the admittance control is used to realize the man-machine compliant operation,and the impedance-admittance joint control method is established to realize the robotassisted bone grinding operation.This paper is mainly composed of the following aspects:Firstly,aiming at the actual demand and safety of the interaction between the robot end and the bone tissue in orthopaedic surgery,on the basis of completing the dynamic model of the robot and the bone tissue interaction,the impedance control method with variable stiffness is studied.The dynamic relationship between the end position and the contact force is established,and the force tracking error can be effectively reduced by changing the stiffness of the robot itself.The stability and robustness of the variable stiffness impedance control are analyzed through simulation experiments.Secondly,for the flexibility of the human-computer interaction process and the accuracy of dragging and teaching,this paper proposes an admittance control algorithm based on the operation intention,applies the fuzzy control logic to the identification of the operation intention,quantifies the operation intention,and quantifies the operation intention according to the operation intention.It is intended to modify the admittance coefficient online to improve the flexibility of human-computer interaction.The end-operating force calculation method based on Kalman filter completes the compensation of the gravity of the end tool and the error of the sensor itself,and reduces the required drag force.Thirdly,in view of the complex environment interaction problem in the bone grinding process,this paper combines impedance control and admittance control to establish an impedance-admittance joint control method.The joint control method based on duty cycle can adjust the impedance control online according to the change of environmental stiffness.The fitting relationship between the contact force and the duty cycle is obtained through the neural network,and the estimated value of the environmental stiffness is obtained online.The performance of the impedance-admittance joint controller is analyzed by simulation.Finally,a bone grinding operation platform was built based on the six-degree-offreedom collaborative robot,and the experiment of instrument-tissue interaction,drag teaching experiment and bone grinding experiment were carried out.The experimental results show that the force tracking error of the interaction experiment between the robot and the bone tissue is within 5N,the drag teaching error of the admittance control algorithm based on the operation intention in the Cartesian space is 1.5mm,and the robot-assisted bone grinding based on the joint control method.This job reduced grinding force overshoot by 13.2%and increased grinding speed by 0.57mm/s.