Abstract:This article mainly aims at the problem of low accuracy of environmental mapping of wheeled robot system. Based on the theoretical and analytical research of wheeled robot kinematics model, sensor model and fusion algorithm, the model of wheeled robot system is established. Finally, through the simulation experiment, the impact of the performance parameters of laser radar (field of view, angular resolution) on the position and pose of wheeled robot and the quality of mapping during the environmental mapping process is comprehensively analyzed. It is found that the position uncertainty curve in the direction of the x and y coordinate axes shows a periodic downward trend with time, and the angle error shows a trend of oscillation up and down around a value. As the angle of view of the lidar increases, the curve oscillation decreases and tends to be smoother, and the white boundary of the mapping results becomes clearer and more complete. As the angular resolution of the lidar increases, the curve oscillations increase, and the amplitude is larger. At the same time, the white boundary of the mapping results is more blurred, and the accuracy is lower. Therefore, the accuracy of robot system environment mapping can be improved by increasing the angle of view of the lidar and reducing the angular resolution.

Abstract:In order to solve the problem that the calibration equation established by linear regression is not ideal for the aircraft landing gear load calibration experiment, considering the nonlinear influence of factors such as landing gear compression stroke and strain gauge position on the calibration load in the experiment, the landing gear load calibration model is constructed by using AdaBoost and XGBoost nonlinear regression methods using feature fusion and ensemble learning theory. Firstly, experimental data are obtained through landing gear load calibration experiments, and the input feature matrix is established using principal component analysis method. Then, a landing gear load calibration model is constructed, using the three directional loading loads of the landing gear as label vectors. The training and testing sets are divided according to the random sampling principle, and the calibration model is trained using AdaBoost and XGBoost methods. Finally, the load is fitted and predicted in the testing set, and the model is evaluated using four evaluation indicators: root mean square error, average absolute error, determination coefficient and time. The experimental results show that compared with the widely used least squares method, the calibration model established by XGBoost method can better fit the loading load. XGBoost algorithm is more advantageous in scenarios without considering timeliness. The research results have important value for improving the accuracy of aircraft landing gear load measurement and further research on aircraft Structural health monitoring.

Abstract:In view of the lack of indicators and the imperfection of technology in measurement and evaluation of mobile robot environment mapping, this paper takes wheeled robot and FastSlam mapping algorithm as the research object, constructs physical scene and standard digital map, and extracts accurate, effective and reliable environmental map evaluation indicators to measure and evaluate the mapping sensor lidar and its mapping results from all directions. This method proposes multiple evaluation indicators such as global feature parameters and local feature parameters, providing support for the reasonable evaluation of the quality of mobile robot environmental mapping and the superiority of environmental mapping algorithms.

Abstract:In order to solve the problem of common mode interference that affects the accuracy of data acquisition system in industrial field, the manifestation of AC common mode interference is studied by means of waveform analysis, and its typical characteristics of DC offset superimposed AC fluctuation and background noise are revealed. It is proposed to characterize the interference intensity by the amplitude of the effective value of the waveform, and quantitatively express the common mode rejection ratio (CMRR). At the same time, the effect of the system background noise is eliminated by using the effective value superposition model, which improves the measurement accuracy of the common mode rejection ratio. Based on this method and process, the main sources of uncertainty, such as signal source error, data acquisition system gain error, amplitude measurement error, amplitude resolution error and measurement repeatability, are discussed. The measurement uncertainty is analyzed and evaluated. Combined with an example, the uncertainty evaluation result of channel CMRR is given, and the practicability and feasibility of the method is verified.

Abstract:The surface of aero?engine blades has large bending and torsion, and it is difficult to ensure consistent surface roughness during machining. In view of the lack of definitions of measuring position and direction in the current roughness measurement method when measuring blades, which leads to the problem that the measured roughness value cannot determine the eligibility of blade roughness, the research on blade roughness measurement method is carried out. Based on the measured section data of blades, using the roughness probe carried on the CMM, the blade roughness measurement method is obtained by carrying out multi?position and multi?direction roughness measurement experiments on different types of blades and analyzing the difference of the roughness measurement results in different positions and directions. This method associates the blade roughness with the blade profile, and solves the problem that the measurement position and direction of blade roughness are not standardized. The research results are of great significance to accurately and effectively evaluate the qualification of blade surface quality.

Abstract:In the fields of structural health monitoring, seismic monitoring, and aerospace, low?frequency micro?vibrations with frequencies below 10 Hz and amplitude less than 1 mm need to be measured accurately. The acceleration values of low?frequency micro?vibrations are on the order of mg ~ μg, while the sensitivity of existing commercial accelerometers is mostly below 0.5 V/g, which can no longer meet the requirements. In this paper, high?sensitivity low?frequency optical accelerometers is carried out. Based on the sensing principle of accelerometers, the technical requirements related to the design of low?frequency accelerometers are determined through theoretical modeling, and one?dimensional (1D), two?dimensional (2D), and three?dimensional (3D) elastic mechanisms are constructed by using leaf springs and flexible hinges as elastic elements with single and multiple seismic masses; based on high?precision optical sensing principles such as the principle of image dispersion, laser triangulation, and laser auto?collimation, a high?sensitivity optical sensing system is designed. 1D, 2D and 3D low?frequency optical accelerometers have been designed and their performance has been verified by experiments, with sensitivity better than 9 V/g and resolution better than 1 mg, which can be used for low?frequency micro?vibration measurements.

Abstract:Research has been conducted on the issue of high price and inconvenience in use of laser vibration measurement system. A low?cost prototype of all?fiber laser vibration measurement system is developed by using 1 550 nm mature narrow linewidth light source and optical fiber components. In the optical path part, a heterodyne laser interferometer is built using Mach?Zehnder interferometer struct ure, the reference light is modulated by a 40 MHz acousto?optic modulator and interferes with the measurement light on the photodetector surface to produce the original laser Doppler signal. In the signal demodulation part, the phase demodulation method is used to demodulate the original laser Doppler signal to obtain the motion characteristics of the vibration target, including the displacement, velocity and acceleration information. The performance of this prototype is tested with the vibration standard device in our center, and the experimental results show that, the measurement errors of peak displacement, velocity and acceleration of this 1 550 nm all?fiber laser vibration measurement system are within the range of -0.6% ~ 0.7%, in the medium to low vibration frequency range of 10 ~ 2 000 Hz. This system has both high measurement accuracy in medium to low vibration frequency range, and relatively low cost, convenient operation, which has technical reference value.

Abstract:In order to solve the problem of the Raman effect on the generation of optical frequency comb in microcavities under whispering gallery mode, especially at GHz repetition frequencies, which makes it difficult to generate a very smooth optical comb spectrum. Firstly, design and adjust the coupling length between the waveguide and the microring. Then, optimize the coupling angle, adjust the matching mode between the waveguide and the microring, the coupling Q value in the long wavelength is reduced, the threshold of Raman generation is increased, and the Raman effect is suppressd. According to the simulation analysis, compared with the general straight waveguide microring coupling structure, the designed pully waveguide microring has three times increase in the Raman threshold at the short wavelength, and the optical frequency comb power generated at the short wavelength has increased by 20 dB. This provides a certain reference value for the design of whispering gallery mode microcavity structures.

Abstract:Aiming at the problem of inaccurate measurement of aero?engine intake flow,this paper investigates a new type of aero?engine flow pipe with a throat structure.Its advantage is that on the one hand, due to the optimization of the flow field by the throat structure, higher intake flow measurement accuracy can be obtained by arranging fewer measuring probes. On the other hand, the static pressure difference between the straight pipe section and the throat is used to obtain the flow in the pipe in a non?contact way, which greatly simplifies the test method of the inlet flow in the test site.The feasibility of the design scheme is verified by simulation and experiment. The research results provide a new solution for the accurate measurement of aero?engine intake flow.

Abstract:In order to solve the problem of low accuracy of long?distance transmission in fiber optic time transfer system, the basic principles and technical characteristics of four mainstream high?precision fiber optic time transfer methods, namely round?trip, dual?fiber bidirectional time synchronization, bidirectional wavelength division multiplexing and bidirectional time division multiplexing, were analyzed. Based on this, a single?channel time?frequency transmission device was developed. The device adopts the electrical phase compensation method to realize frequency transfer synchronization, and uses the round?trip method combined with bidirectional time division multiplexing to achieve time transfer synchronization. It uses 1 PPS and 100 MHz to jointly mark the time signal, with 1 PPS as the coarse time marker and 100 MHz as the fine time marker, to achieve high precision time synchronization. Experiments show that the uncertainty of the single?channel time?frequency transmission device is about 13 ps, which can meet the requirements of the existing fiber optic time?frequency synchronization network metrology calibration. The device has broad application prospects in the fields such as cascaded time transfer synchronization and fiber optic time?frequency synchronization network metrology calibration. It provides an important technical support for the construction of high stability, high reliability and high precision time service system.

Abstract:In order to meet requirements of transient heat flux measurement and solve the problem that the response time of radiant heat flux meter cannot be accurately measured, we designed a response time measuring device of radiant heat flux meter, which uses the fast response characteristics of high?power laser to form a heat flux step system, uses a high?speed acquisition system to collect the output of the heat flux meter synchronously. The response curve of the heat flux meter is analyzed and calculated to obtain the response time. A variety of response time testing schemes are compared, and the fast response characteristics of the radiation heat flux meter response time measurement device is verified through experiments. The results show that the fastest response time of the device to measure the radiation heat flux meter is 4.4 ms, which can effectively meet the response time test requirements of large?range and fast response radiation heat flux meter, and promote the development of transient radiant heat flux measurement technology in China.

Abstract:In order to ensure that the strength of the truss meets the application requirements of centrifugal composite calibration under the ultimate load condition of the centrifugal composite calibration device, the finite element analysis and verification test process of the truss structure were studied. ANSYS finite element analysis software was used to design the simulation process to complete the centrifugal boom truss structure analysis. The whole analysis process was described from the structure composition, model establishment, grid division, load constraint setting and other programs. By analyzing the result nephogram, it is confirmed that the stress result of truss meets the requirement of mechanical structure. The results of structural analysis are verified by the calibration test of the linear accelerometer. The results show that the structural strength of the truss meets the requirements of use, the deformation is close to the measured value, the structural analysis results are in accordance with the actual application test value, and the analysis results are reliable. The process and verification method of truss analysis can provide reference for similar truss analysis.

Abstract:In order to solve the problems of time?consuming, labor?intensive, low efficiency and insufficient accuracy in the calibration of strain gauges using the split flow method and achieve high?precision acquisition of strain signals, a low drift and low noise self?calibration circuit has been studied and designed. The acquisition channel and calibration signal are configured by program control. The functional relationship between the acquisition signal and the self?calibration signal is fitted, and the calibration coefficient is obtained. The strain measurement results are corrected, which effectively reduces the temperature drift error and noise error of strain measurement and meets the accuracy requirements of strain measuring instruments.

Abstract:The strain method is one of the commonly used methods for load measurement of metal structures. The accuracy and linear correlation of the data measured using the strain method under the individual effect such as bending moment, shear force, and torque are very good. In reality, the structural stress situation is complex and structures are often subjected to coupling effects of bending moment, shear force, and torque. Therefore, the linear correlation between the data measured by the strain method and the multiple linear regression equation generated by the input load value needs further verification. A typical flexural?torsional beam structure is designed. Under the coupling effect of bending moment and torque, the strain method is used to measure the load. The accuracy of the measurement data is good, and the linear correlation of the multiple linear regression equations generated by multiple variables such as input load value, bending moment and torque is strong.

Abstract:In order to solve the problem that the calibration of widely used handheld digital multimeters still relies on manual work, according to JJF 1587-2016 "Calibration Specification for Digital Multimeter", an automatic calibration device for hand?held digital multimeter is designed. The calibration device realizes the position control, function, range switching and motion control of the hand?held digital multimeter through the electromechanical system. The data reading of hand?held digital multimeter is realized through the visual recognition system. Combined with calibration software, 8?station continuous automatic calibration is realized. It is verified through test that the device improves the calibration efficiency of handheld digital multimeter and can meet the calibration requirements of handheld digital multimeter.

Abstract:With the development of aviation technology, higher requirements are put forward for the dynamic characteristics of thermocouples. In view of the problem that the existing thermocouple acquisition scheme cannot continuously acquire and obtain the temperature value in real time, a set of thermocouple dynamic characteristics measurement system based on LabVIEW is designed. The working principle, hardware structure and software design of the system are described in detail, and the system is compared with the oscilloscope data collection scheme. The test results show that the system has high reliability and high automation, which effectively improves the working efficiency, and provides support for the performance evaluation of temperature sensors.