Research On Force Dragging And Milling Force Control Of A Spine Surgery Robot

Traditional spinal surgery is characterized by high risk and difficulty,and can cause damage to the human body.In contrast,the robot-assisted spine surgery can improve the accuracy of surgery and reduce surgical risk effectively by introducing robots into the operation.In this paper,the admittance control is used to realize force dragging control.The robot can move to the expected operating area under the doctor's guidance.It reduces the difficulty of using robot and conforms to the doctor's practice.In addition,during laminectomy,the milling method based on position control could not meet the operational requirements because of the complex anatomical structure and inhomogeneous bone characteristics of vertebral lamina.An adaptive fuzzy force control method is adopted for vertebral lamina milling in order to stabilize the contact force in the reference range.The robot control system is built,and the force dragging control algorithm and the milling force control algorithm are verified experimentally.Then,by analyzing the configuration of the spine surgery robot,the forward and inverse kinematics model of the robot is established,and the correctness of the robot kinematics model is verified by simulation.Furthermore,the velocity Jacobi matrix and its inverse matrix of the robot are deduced,which provides a model foundation for speed control and monitoring of force dragging control.In order to improve the robot motion control accuracy,the kinematic parameters are calibrated by using a laser tracker,and the accuracy measurement experiment is carried out.The parameters of the admittance control model based on velocity output are simulated and analyzed,and the influence of parameter adjustment on the output of the speed response is analyzed.The stiffness of user's arm is identified on-line by recursive least square method.The admittance model is adjusted according to the identification results to improve the stability of force dragging interaction.By analyzing the interaction force and velocity information during force dragging,the operator's intention is estimated.Then a fuzzy parameter variable admittance control algorithm based on on-line identification of arm stiffness is proposed.In order to control the milling force of laminectomy,the analysis of the movement and force of the milling tool in milling process of bone tissue is presented.For traverse and vertical feed motion of tool,the milling contact force in each direction is controlled by feed speed and feed depth.A multilayer adap tive fuzzy controller is employed to adjust the milling control parameters on-line according to the change of force,so as to improve the adaptive ability of the force controller.Finally,a robot control system is set up and the algorithms are verified by a series of experiments.The effectiveness and compliance of force dragging control algorithm are verified by analyzing the data of speed and force in the process of interaction.Experiments on milling force are carried out,and the milling experimental data of position control and force control are compared.The milling process under fuzzy force control can provide more stable contact force,and improve the safety of operation.