| In recent years,software robotics technology has become a research hotspot and has been rapidly developed.At the same time,based on the high flexibility and deformation characteristics of the soft robot,the flexible material of the drive body is susceptible to the influence of the contact object,the load and its own gravity.Therefore,the accurate feedback of the shape information of the flexible drive body with the shape sensor is an important link to realize the precise control of the soft robot.Traditional strain sensors based on electromagnetic principles have problems such as large rigidity,large size,weak signal interference,zero point drift,and poor compatibility,and it is difficult to meet the shape measurement requirements when fused with a soft robot.Fiber Bragg Grating(FBG)has become the preferred sensing element for flexible robot shape measurement due to its advantages such as high accuracy,small size,light weight,corrosion resistance,easy integration,immunity to electromagnetic interference,good biocompatibility,and a single optical fiber that can connect multiple measuring points in series.However,there are still many shortcomings in the current research on the shape sensor of flexible robot based on FBG.For example,the response rule of FBG and flexible matrix in shape measurement is not explored from the perspective of the combination of FBG and flexible matrix.Most sensors can only realize multi-point curve shape sensing,but not multi-point surface shape sensing.The sensor only tested the single-direction pure curved surface,and did not measure the shape of complex surface.In addition,the sensor manufacturing process also needs to be improved.In response to the above problems,this paper combines the advantages and characteristics of FBG sensing technology.Conducted research on FBG flexible sensing technology used for shape measurement is researched.The specific work is as follows:1.The research status of shape sensing technology based on implantable FBG soft robot is investigated.The layout method and sensing algorithm of fiber grating are summarized and classified,the limitations of existing research technology are proposed,and the preliminary conception for the subsequent work is carried out.2.Combining the sensing principle and sensitive mechanism of FBG,the shape sensing technology based on FBG is theoretically analyzed,the principle of curvature measurement is deduced,and the proportional relationship between the wavelength change of fiber grating and the curvature is obtained.Afterwards,according to the possible deformation of the optical fiber in the actual situation,a three-dimensional coordinate system was established and a set of surface reconstruction algorithms were proposed.3.PDMS and silica gel were selected as flexible substrates,and the response characteristics of bending measurement of soft materials with different Young's modulus implanted with FBG were studied.When a flexible material with a low Young's modulus is combined with a rigid silica with a high Young's modulus,there are practical problems such as creep and strain transmission differences caused by rigidflexible strain coupling.The greater the difference between the Young's modulus of the flexible substrate and the FBG,the more serious the creep caused by the rigid-flexible coupling.Moreover,the strain transmission rate of the FBG is related to the Young's modulus of the flexible matrix,and has nothing to do with the flexible matrix material.The maximum strain transfer rate is 0.680,the minimum strain transfer rate is 0.260,the maximum sensitivity is 56.649,and the minimum sensitivity is 35.668.Then a strain transfer model was established to verify the consistency between the experimental results and the theoretical derivation.4.Experimental research on reconstruction of flexible sensor based on FBG First,a flexible sensor based on unidirectional parallel array FBG was studied.An experiment platform was built,the sensor was subjected to a curvature calibration experiment,and then a shape test was carried out on a single-direction pure curved surface.The maximum curvature measurement error was 5.7%,and the minimum curvature measurement error was 3.4%;on this basis,a flexible sensor based on upper and lower orthogonal FBG is designed.An experimental platform was builted,the sensor was subjected to a curvature calibration experiment,a complex surface was reconstructed and tested,and the test results were analyzed for error.The maximum curvature measurement error was 4.5% and the minimum curvature reconstruction error was 2.8%.It proves the feasibility of the reconstruction algorithm,solves the defects in the existing research on the shape sensor of the flexible robot based on FBG,and provides a scientific reference for the research on the shape measurement technology of the soft robot based on the implanted FBG. |
PDF Full Text Request