Research On Dynamic Analysis And Impedance Control Of Surgical Drilling Robot

The surgical bone-drilling robot is an auto-machine applied in orthopedic surgery,oral surgery and plastic surgery which need to process screw hole.such as,the total knee arthroplasty,dental implant spinal surgery,skeletal fixation,facial plastic surgery and so on.In the surgical process,it is mainly used to assist the chief surgeon with end-effector to working the screw hole.The reason why discusses the bone-drilling robot is that there are so many capillaries,muscles,nerve tissues,blood vessels around bone,which can easily bring out cross infection or some other serious injury.Bone is a kind of non-uniform material,so it is hard to establish the accurate drilling model.Which made great difficult to achieve precise motion control.This paper talk about the problems based on the bone-drilling process and motion control as follows:1.The analysis of bone drilling process: the mechanical property and generation of force and torque of bone in the process of drilling were analyzed.The drilling whole procedure was divided into three stages: drilling stage,stable drilling stage and drilling out stage.And then,the expression of force and moment produced by drill bit in three stages of drilling was obtained.2.The finite element analysis of bone drilling process: the finite element model of medical drill bit and bone tissue was established in ABAQUS software.The bone model and drill bit model were meshed and the failure model was established to simulate the rule of force and torque during drilling,which applied basis of bone material mathematic model.3.Design,calculation and modeling of surgical drilling robot: the end-effector of drilling robot was designed,and the overall design of bone drilling robot was completed with 6 DOF UR robot as manipulator body.And the forward kinematics and inverse kinematics of the bone drilling robot was calculated with the D-H parameters.The dynamic model was established.and the dynamic characteristics of angular velocity,force and torque of each joint in the process of robot motion under specific trajectory were analyzed.Which can be used to verify the rationality of the surgical drilling robot design.4.The motion control of surgical drilling robot: According to the analysis results of bone drilling process,the mathematical model of bone was established to calculate the contact force in the process of bone drilling.The mathematical model of the robot joint was built,and the impedance control algorithm was designed to calculate the dynamic relationship between contact force and position of end-effector.The impedance parameters were analyzed and optimized,and the position correction of the end actuator was calculated,which can achieve the motion control of the bone drilling robot.In summary,this paper designed the surgical drilling robot based on the analysis and simulation of the bone drilling process,and carried out the kinematics and dynamics analysis.According to the dynamic characteristic curve of each joint under the specific trajectory,the angular velocity,force and torque of each joint of the robot in the process of movement were relatively stable,and there was no excessive impact.The mathematical model of the bone was established based on the analysis results of the drilling process to calculate the contact force.And then,the impedance control algorithm was used to control the position of the bone drilling robot,and the impedance control parameters were optimized.The results of the contact force response of the impedance control under the optimal parameters show that the impedance control has smaller overshoot and no significant oscillation.