Study On Flexible Volume Strain Transfer And Shape Reconstruction Based On Fiber Bragg Grating

With the wide application of the traditional rigid manipulator in the society,people put forward new requirements in many fields,including the safety,friendliness and flexibility of human-machine and machine-environment interaction.The flexible manipulator,as a branch of the robot field,has developed rapidly with its good flexibility,safety and environmental compliance.However,most of the motion control methods of the flexible manipulator are open-loop control systems,the effect is not satisfactory.Therefore,it is of great significance for the further development of the flexible robot to carry out the shape monitoring of the flexible manipulator and complete the real-time feedback of its motion and attitude information.Based on FBG strain detection technology,this paper proposes a new shape reconstruction technology of flexible manipulator,which can sense and feedback the movement position,shape change and other parameters of flexible manipulator in real time,and provide theoretical basis for closed-loop control of flexible manipulator,so that it can be controlled more precisely and adapt to more complex environment.The main contents of this paper are as follows:(1)In the process of strain measurement of FBG sensor,there is a problem of deviation between the measured strain of FBG and the actual strain of the substrate.In this paper,a three-layer sensing structure model of substrate adhesive layer optical fiber is proposed.The strain transfer model of surface adhesive FBG sensor is derived,and the expression of the influence depth of the sensor on the substrate is calculated.(2)The influence of various factors on the strain transfer of FBG sensor is studied,and the packaging process and bonding process parameters of the FBG sensor are summarized.At the same time,the finite element simulation corresponding to the variable transfer model is used to verify the accuracy of the transfer theory.(3)At present,the flexible manipulator has a large ratio of length to diameter,in which bending and stretching are the main deformation means,and its shape can be represented by the continuous track or discrete point of the center line.Therefore,this paper proposes to establish the kinematic model of the flexible manipulator by the method of segmented constant curvature.More parameter information can be obtained by interpolation with limited detection information,and the reconstruction accuracy of deformation curve can be improved by introducing strain transfer coefficient.Using the finite element simulation to analyze the strain distribution,a new spiral fiber grating sensing network layout is designed.Combining with the shape reconstruction theory of the flexible body motion model,the dynamic data processing program of MATLAB is compiled,and the deformation shape curve of the flexible body is simulated according to different scenarios to verify the feasibility of the reconstruction algorithm.(4)By comparing the reconstructed shape with the actual shape,the feasibility of the FBG sensor network is verified.By comparing the reconstructed shape with the theoretical shape without introducing the strain transfer coefficient,the influence of introducing the strain transfer coefficient on the precision of shape reconstruction is verified.It shows that the shape reconstruction theory and the layout of FBG sensor network are reasonable and accurate,and the necessity of introducing strain transfer coefficient.The experimental error is analyzed,and the measures to further reduce the error and improve the accuracy are put forward.