Abstract:In cold atom interference experiments, the atoms need to be cooled and manipulated by laser, so the frequency stability of semiconductor lasers is required. Because of the large linewidth, poor power stability, slow drift and mode hopping, it is necessary to stabilize the frequency of semiconductor lasers. This paper introduces six common frequency stabilization methods in cold atom interference experiments, including saturated absorption spectrum stabilization, wavelength modulation frequency stabilization, modulation spectrum frequency stabilization, modulation transfer spectrum frequency stabilization, two-color laser frequency stabilization and frequency-voltage conversion frequency stabilization. The principles, characteristics and application fields of these methods are described respectively, which provide reference for the practical application of semiconductor lasers.

Abstract:Molecular absorption spectrum of fluid medium is related to the physical properties of itself，which contain abundant information and have the advantages of high sensitivity, fast response and strong anti-interference ability. The pressure measurement method combined with tunable diode laser absorption spectroscopy is a new idea of pressure and vacuum metrology. In this paper, the basic principle of measuring pressure based on tunable diode laser absorption spectroscopy is analyzed. The direct absorption spectroscopy and wavelength modulation spectroscopy are introduced, and their advantages and disadvantages are compared. The main research research advances and applications at home and abroad in recent years are reviewed. On this basis, the key technical bottlenecks of pressure measurement technology based on TDLAS are summarized, and the main application fields in the future are prospected.

Abstract:In order to analyze the aeroengine comprehensive performance, the evaluation model was set up. Firstly, with different aeroengine working states the suitable flight data were selected as performance evaluation indexes. Then the analytic hierarchy process and fuzzy membership function were used to calculate the weight values and the normalization values of the performance evaluation indexes respectively, and the aeroengine comprehensive performance value was calculated by using the linear weighted sum method. The example analysis showed that, the aeroengine comprehensive performance value which was calculated by the evaluation model could well reflect the good and bad of aeroengine comprehensive performance and had an important guiding significance to the condition monitoring and fault diagnosis of aeroengine.

Abstract:Force Limit Method can decrease the over-testing problem associated with traditional vibration testing by dual control of the force and acceleration. Force specification is difficult to estimate, especially for equipment vibration test that exists the source definition problem. This paper demonstrates a modified complex two-degree-of-freedom method adapted to fixed boundary conditions of the mounting structure. Some methods are also given to acquire the mass parameters of source and load, which are critical to the reasonably conservative force specification. Practical examples have been performed with the modified method to verify its validity, which provides reference for force specification determination.

Abstract:Aiming at the redundancy problem in wireless sensor network, a step-by-step compression-aware codec algorithm decomposes the original signal according to the sparsity of the same or different dictionaries, and compresses and encodes the decomposed signal by using the Bernoulli observation matrix to generate a dictionary mask during the compression process. The terminal restores the data step by step according to the coding information, the sparse dictionary and the dictionary mask. This method is more robust than traditional coding compression technology and is not sensitive to packet loss. Compared with the original compressed sensing algorithm, it saves the transmission bandwidth and improves the real-time performance of data information acquisition.

Abstract:Optical SINS error accumulate over time,as an error compensation technique,discrete calibration is a necessary means to improve navigation accuracy. SINS calibration parameters are mainly the scale factor、installation angle and bias, the article described IMU calibration principle, derived the transmission way of calibration parameters errors, theoretically analyzed the correlation effects of the calibration parameters, and get the following results: Bias repeatability errors have no effect on the scale factor and the installation angle calibration; Scale factor linearity and repeatability errors have no effect on the installation angle and bias calibration; Bias stability errors have effect on calibration of scale factor as well as installation angle ; Angle random walk has effect on the gyroscope three calibration parameters; Random noise has effect on the accelerometer three calibration parameters; Asymmetry of the calibration scale factor has effect on installation angle and bias of gyro;Installation angle repeatability errors have effect on bias and no effect on scale factor calibration of gyro ,and have no effect on scale factor or bias calibration of accelerometer.The conclusion is of great significance for INS performance evaluation, error allocation and device selection.

Abstract:Aiming at the problem of corner information extraction in automatic recognition and location of key points to be measured in machine vision measurement applications, a real-time video image corner detection system is built based on the heterogeneous architecture of ARM+FPGA in ZYNQ series expandable platform, using hardware and software co-design method. Using Vivado HLS tools, corner detection algorithm is encapsulated into an IP core that can be deployed to the PL end, which greatly shortens the development cycle. Reasonable task allocation is made for each module of the system, which makes the system have the flexibility of ARM and the parallel processing ability of FPGA, and shows the advantages of parallel heterogeneous architecture. The IP core of image algorithm in the system can be replaced and updated flexibly, which provides an important reference for miniaturized application based on machine vision detection.

Abstract:Aiming at the problem of high temperature vibration measurement in the development and test of major equipment, an all-optical fiber high temperature vibration measurement device based on photon Doppler principle is established. Vibration measurement performance was tested in the temperature range of 0～1200 ℃. The experimental results show that the device can measure the maximum vibration speed of 1 m/s and the maximum vibration acceleration of 378.4 m/s2. The linearity of velocity sensitivity is less than 0.5%, and the frequency response range is 0-2 kHz. It has good stability and reliability. It also shows that the device can measure the vibration at high temperature above 800 ℃. The advantage of low reflectivity requirement improves the important reference for the development of high temperature vibration measurement equipment applied in aerospace and other fields.

Abstract:On-machine measurement and testing takes machine tool as hardware carrier to realize the integration of processing and measurement, which is of great significance to improve product quality and production efficiency. This paper introduces the composition and implementation process of the in-situ measurement and testing system for NC machining, and tests the performance of the system. The results show that the in-situ measurement and testing system for NC machining of large structural parts can realize the size and position errors in the process of large NC machining parts. Position measurement greatly shortens the positioning time of large NC parts, effectively improves the efficiency and qualified rate of one-time clamping, avoids the second clamping of workpieces, reduces the production cost, and provides a strong guarantee for digital assembly.

Abstract:With the development of aviation technology, the existing testing methods of angle of attack and sideslip sensors cannot meet the needs of a large number of airborne system testing. In view of this situation, based on LabVIEW language, a set of measurement and control system of standard airspeed tube angle test device is designed, and the working principle, hardware structure and software design of the system are described in detail. The experimental results show that the measurement and control system have good reliability and high automation, which provides an important basis for the performance evaluation of airborne systems.

Abstract:A device for measuring thermal diffusivity based on laser flash method is developed. The furnace is vacuum pumped by mechanical pump and molecular pump, then heated. The measured sample is stimulated by high-power pulsed laser instrument. The temperature of the sample increases on the laser irradiation surface, and the heat begins to transmit to the other side. The infrared detector records the temperature rise process in real time and converts it into an amplifier after amplification. The voltage signal is input to the acquisition card and communicates with the computer software. The self-compiled measurement software calculates and processes the data in real time, and then gets the thermal diffusivity value of the sample. The system was used to test the standard sample in the temperature range of 300 ~1300 C. The repeatability of the measurement was less than 0.85%.

Abstract:In order to find a precise and effective method to characterize micro-hardness of Au coating to meet the demands for space applications. The micro Vickers hardness test method and Nano-indentation test hardness method were selected to characterize micro-hardness of Au coating under different test position and different force conditions. According to the requirements of the relevant technical standards, the feasibility of the test method is analyzed. The results showed that: The optimized micro Vickers hardness test parameters and results meet the QJ482 technical standard requirements. The depth of indentation is less than 1/7 of the thickness of the Au coating, the impact of matrix material on hardness test results is avoided. The test method is feasible and the results are valid.

Abstract:In order to study the influence of the position of the pressure intake on the measurement of periodic fluctuating flow through Venturi tube, the flow field of sinusoidal fluctuating flow in the lower venturi tube is simulated by FLUENT software. The differential pressure between the flow rate and four groups of pressure intake in a single cycle under different fluctuating frequencies and amplitudes is obtained. The four groups of differential pressure are used to calculate the fluctuating flow rate separately, which is a mistake in the calculation of flow rate. The differences were compared and analyzed. The results show that the different axis positions of Venturi tube pressure intake will lead to different integral values of reciprocal cross-sectional area between pressure intake, which will affect the measurement error of pulsating flow.

Abstract:It is an international hotspot to monitor the working condition of aero-engine using vibration data. Firstly, three familiar analysis methods for vibration data are introduced; secondly, emulation analysis based on vibration data under steady flight condition are made; lastly, qualitative analysis for the extrusive frequence in the emulation are made. Statistical analysis based on the frequency of multi vibration data suggests that there may be some asymmetry failures in the free turbine which is important for the novelty detection of aero-engine vibration.

Abstract:The calibration system of the photoelectric tracker is developed. The laser tracker is used to track the photoelectric tracker and collect measurement data. The gross errors in the system are eliminated and the center of the photoelectric tracker is determined by spherical fitting least square method. A reasonable coordinate conversion model is established to realize the transformation from the center of laser tracker to that of photoelectric tracker, and the calibration results are obtained by comparing the measured data of the two. The method of combining VB and MATLAB software is used to analyze and process the data, so as to improve the operation efficiency. The test results of the photoelectric tracker calibration system are given with examples, and the uncertainty of the system is analyzed. The reliability of the calibration system is proved, which provides a reference for the parameter calibration of the tracking and aiming system.

Abstract:Signal conditioner is a significant part of dynamic measurement system, the bandwidth, amplification and filtering are main indexes to evaluate the performance. The output signal amplitude and phase of the dynamic measurement system mainly characterized the test results. The influence research about dynamic performance of signal conditioner to dynamic measurement system output signal amplitude and phase are studied in this paper, conducted the experiment then analyzed the attenuation of output signal amplitude and phase caused by the bandwidth, amplification and filtering. Improving the accuracy of dynamic measurement results, optimizing the dynamic performance of measurement system is the significance of this paper.

Abstract:In the process of vibration testing of a certain type of aircraft，The causes of abnormal values such as generation，screening and elimination are analyzed. Through experimental comparison and the method of analogy exclusion, The influence of vibration sensor on test results is demonstrated.

Abstract:Throughthe specific circumstances of large experimental equipment to carry out in-depth study of measurability, making large experimental facilities and equipment related to the relevant managers, designers, testers, users and maintenance personnel canintegrate measurability idea into their own work. By means of measurement, the parameters of the large experimental equipment, especially the output parameters of the system level can be traced back to the approved national measurement standards, and ultimately to achieve effective control of the technical state of the system.

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