Structural Analysis And Tremor Suppression Method Of Master-Slave Surgical Robot Manipulator

With the rapid development of the country’s comprehensive strength,medical equipment is constantly being updated iteratively.The master-slave minimally invasive surgical robot has a broad application prospect in the field of clinical surgery by virtue of its remote operability,human-machine collaboration and high precision.However,there are still many deficiencies in the master-slave surgical robot that is widely used in the world,such as increased collateral damage during application,narrow field,unrecognized misuse,and end-of-arm tremor.Among them,the flexibility of the robot arm structure and the end tremor of the robot arm caused by the physiological shaking of the operator’s hand have the most significant impact on the reliability,safety and stability of the surgical robot.Among them,due to the structural flexibility of the robotic arm itself and the physiological shaking of the human hand during the remote operation,the end of the robotic arm produces a certain tremor phenomenon.This affects the reliability,safety and stability of the surgical robot.In this thesis,the finite element method is used to analyze the structural and mechanical properties of the master-slave surgical robot manipulator,and a master-slave tremor suppression strategy is designed according to the physiological tremor mechanism of the human hand,which improve the comprehensive performance of the master-slave surgical robot.The dynamic theory of the manipulator and the mathematical characteristics of the tremor signal of the human hand are studied.Firstly,a robot arm dynamics model considering joint flexibility is established based on the Lagrange equation.Secondly,a manual tremor signal acquisition experiment was designed using an optical 3D motion capture system to analyze the motion characteristics of manual physiological tremor signals.The experimental results showed that the amplitude of physiological tremor in human hands was within 1 mm and the frequency band range was between 5-15 Hz.Based on the experiments,a mathematical model of the physiological tremor signal in human hands was established by using Fourier fitting method,which provided a theoretical basis for designing a master-slave tremor suppression strategy.The finite element model of the robotic arm was established,and the static analysis,modal analysis,harmonic response analysis and structural optimization design of the robotic arm were carried out using Abaqus 6.14 finite element simulation software.The results of the static analysis show that the maximum deformation of the end of the robot arm is 0.513mm,the maximum stress value is 15.560MPa and the maximum strain value is 2.11×10-4 when it is subjected to 100N horizontal force in the zero position state.The results of the modal analysis show that the first six orders of the arm’s intrinsic frequency are between 50 and 320 Hz,and the main vibration patterns are back and forth,left and right oscillation,left and right twisting and up and down pitching and twisting.The results of harmonic response analysis show that the maximum amplitude of 0.104 mm is generated at the RP-1 point at the end of the robot arm when the simple harmonic excitation frequency is 56.419 Hz.After structural optimization,the overall mass of the arm has been reduced,the end displacement,maximum stress and maximum strain values under the same force conditions have been slightly reduced,the first six orders of inherent frequencies have been increased compared with those before optimization,and the maximum amplitude has been reduced.The master-slave control strategy is designed according to the structural characteristics of the force feedback handle and the robot arm to realize the remote control of the robot arm by the force feedback handle.On this basis,a master-slave tremor suppression strategy based on the Kalman filter algorithm is proposed by combining the traditional digital filtering algorithm with the Kalman filter algorithm to achieve theoretical filtering of the tremor signal.In order to verify the effectiveness of the master-slave tremor suppression strategy,this thesis designs a tremor suppression simulation experiment by combining the mathematical model of manual physiological tremor.The simulation results show that the physiological tremor signal is almost completely filtered,and the master-slave tremor suppression strategy has higher filtering accuracy and less delay compared with the traditional low-pass filtering algorithm,which can meet the surgical requirements.In order to verify whether the master-slave tremor suppression strategy is effective in practical applications,a master-slave control experimental platform consisting of a force feedback handle/operating master,a robotic arm/operating slave,a master-slave control system host computer and an optical 3D motion capture system is built in this thesis.Twenty-four sets of master-slave tremor suppression experiments were designed,and the trajectory,velocity and acceleration of the end of the robotic arm were compared before and after tremor suppression in each set of experiments.The experimental results showed that the standard deviation of velocity and acceleration in each group after tremor suppression was smaller than the standard deviation of velocity and acceleration before tremor suppression.This shows that the tremor suppression algorithm can improve the reliability,safety and stability of robotic arm operation.