Research On Wrist Six-axis Force/torque Sensing Of Surgical Robot Based On Fiber Bragg Grating

The rapid rise of surgical robot has promoted the continuous innovation of some traditional surgical fields.Compared with traditional surgical operations,surgical robot has obvious advantages and excellent medical effects.At present,surgical robots basically use master-slave control or remote operation under the intervention of surgeons to complete specific surgical procedures,which makes up for the problems of low accuracy,large trauma and long recovery time of manual operation.However,most surgical robots are unable to provide feedback function,so that surgeons cannot feel the force feedback during the operation.This has brought some hidden dangers to the quality and safety of surgery.As one of the important parts of robot human perception,wrist force perception plays a vital role for doctors in operating robots and performing operations.It can not only fully reflect the force and torque of medical instruments acting on robots.At the same time,the information of force and torque is also helpful for precise force/position control and motion control.Therefore,it is necessary to design a comprehensive,accurate,reliable and compatible new sixaxis force/torque sensor(referred to as six-axis force sensor)for the wrist of medical surgical robot,so as to provide comprehensive and accurate wrist force perception and force feedback data for medical surgical robot.Firstly,this paper analyzes the development status and force perception requirements of medical robot,introduces the classification and research status of common six-axis force sensors at home and abroad,and points out the advantages and disadvantages of six-axis force sensors,which gives the target and direction for the design of new six-axis force sensors in the future.Secondly,the basic theoretical principles related to FBG sensing are studied to provide theoretical support for the design,analysis and manufacture of the six-axis force sensor.At the same time,the four-layer strain transfer relationship model of FBG is analyzed in detail,and the basic beam theory used in the theoretical analysis of the sensor elastic body is introduced.Thirdly,using the design concept of composite beam structure and layered measurement,a novel FBG low-coupling six-axis force/torque sensor for wrist is designed,a novel orthogonal decoupled composite beam structure of FBG low-coupled wrist six-axis force/torque sensor is designed,which is composed of optimized Maltese-T composite beams and orthogonal doublelayer beams(The orthogonal decoupled composite beam structure).Based on Timoshenko beam theory,the mechanical theory of the sensor elastomer structure is analyzed,and the theoretical matrix of force and torque(input)and wavelength offset(output)is obtained.Finite element simulation software is used to analyze the static force load response and dynamic characteristics of the sensor elastic structure,and the excellent characteristics of the sensor are preliminarily proved.Based on the particle swarm optimization algorithm(PSO),the partial structure size of the sensor is optimized to improve the consistency of the structural sensiti vity and the overall stiffness.Then,using 3D printing technology,a six-axis force sensor was made with FBG as the sensitive element.The calibration experiment and correction of the sensor were carried out.The linear fitting of the experimental data was carried out,and the calibration matrix and the static parameter indexes of the sensor were obtained.At the same time,the temperature selfcompensation function of the six-axis force sensor is verified,and the error is less than 0.015Nm.According to the calibration experiment results,the sensors were decoupled in three ways:linear least square method(LS),support vector regression(SVR)and radial basis neural network(RBFNN),and the decoupling accuracy of the three decoupling algorithms was compared.Finally,the application platform of medical surgical robot system was built around the sixaxis force sensor.The demodulation analysis platform of sensor was developed based on Lab VIEW,and the remote operation platform of robot was developed and designed based on wireless communication network.The six-axis force sensor was installed on the end of the sixDOF manipulator to simulate the remote operation of the surgical robot,and the six-axis force and torque of the wrist were sensed in real time.It is proved that the six-axis force/torque sensor has good performance.