Research On Robot Multidimensional Wrist Force Sensor Based On Fiber Bragg Grating

The multi-dimensional wrist force sensor is a key component of the robot.When the robot senses the external environment,the wrist joint needs to feedback the force information sensed by the robot to the robot,and then apply precise force based on the feedback information,so that the robot can perform more delicate operations.Because the multi-dimensional force sensor installed on the robot wrist is the key to the high-precision control feedback of force information between the robot arm and the actuator,the coupling between dimensions and electromagnetic interference are the main problems that affect the measurement accuracy of the multi-dimensional force sensor.In response to this problem,researchers have designed various multi-dimensional force sensors based on the sensing principles of electrical and optical signals,and carried out a series of multi-dimensional force measurement studies for robot joint control feedback.There are many sensitive components,complicated wiring and serious coupling between dimensions.Therefore,this paper has carried out related researches on multi-dimensional wrist force sensors based on fiber Bragg gratings.The main research work is as follows:(1)Based on fiber Bragg grating strain sensing theory and simply supported beam deformation theory,a separate sensing three-dimensional force sensing mechanism is proposed,and a theoretical model of planar two-dimensional force and spatial three-dimensional force sensing is established,revealing the wavelength drift and space of fiber Bragg grating Mapping relationship of multidimensional forces.Based on the fiber Bragg grating temperature sensing theory,combined with the different packaging methods and temperature compensation methods of the fiber Bragg grating,the temperature compensation principle of the fiber Bragg grating multi-dimensional force sensor is studied.(2)For the measurement of the plane two-dimensional force of the robot wrist,a cross-beam type fiber Bragg grating two-dimensional force sensor is designed.The strain distribution characteristics of the elastic body of the cross beam structure were analyzed,and the optimal placement position of the fiber Bragg grating sensing element was revealed;a static experimental calibration platform was built,and the single-dimensional force loading experiment and the two-dimensional force loading experiment under different directions were carried out.The experimental results show that the minimum sensitivity of the sensor for single-dimensional force measurement is about 7.464 pm/N,the worst linearity is about 2.53%,the maximum inter-dimensional coupling error is about 1.01%,and the maximum repeatability error is about 5.828%.The sensor is different in plane the maximum error of force measurement in direction is 4.4%,and the maximum error of direction angle is 2.7°.(3)For the three-dimensional force measurement of robot wrist space,a fiber Bragg grating three-dimensional force sensor with separate sensing structure is proposed.Analyze the strain distribution characteristics and strain output coupling of the elastic body of the three-dimensional force sensor,reveal the location of the sensitive element and the compensation grating,and the coupling relationship between the dimensions of the sensor.Carried out single-dimensional force loading experiments and temperature compensation characteristic experiments in different directions.The experimental results show that the maximum inter-dimensional coupling error of the sensor is about 4.73%,the minimum inter-dimensional coupling error is about 1.10%,and the temperature compensation range is 25?90?.(4)In view of the inter-dimensional coupling problem of the multi-dimensional force sensor,based on the coupling error modeling theory,the data decoupling algorithm of the piecewise third-order fitting is used to carry out the decoupling experiment on the designed three-dimensional force sensor.The test results show that after decoupling,the maximum type ? error value of the sensor is about 2.19%;the maximum type ? error value is about 0.34%.