Abstract:Silicon microcavity photonic temperature measurement includes International Temperature Scale (ITS) temperature measurement based on the thermo-refractive effect and thermodynamic temperature sensing based on optomechanical principle. In the 2018-2027 development strategy of the Consultive Committee of Temperature (CCT), silicon microcavity photonic thermometry was designated as the first priority within the emerging contact temperature measurement techniques. This paper briefly introduces the mechanisms of the two photonic temperature measurement techniques, and summarizes the research progress of metrology institutes and metrology organizations such as NIST in the United States and EURAMET in Europe in the above fields in recent years, as well as the exploratory research achievement from academia. Finally, the latest research results of the National Institute of Metrology, China are introduced including the fabrication and testing of self-developed photonic thermometers with a milli-Kelvin (mK) level resolution, the sub-mK level resolution enhancement approach by means of the Fano resonance, and the sub-mK level self-heating suppression by Si₃N₄ microcavity.

Abstract:With the development of femtosecond laser applications such as femtosecond optical comb spectroscopy and femtosecond ranging, there is a growing demand for femtosecond lasers with higher repetition rates. In this paper, the main technologies and technical progress of solid-state lasers and fiber lasers used to generate femtosecond pulses with GHz repetition rate are reviewed. Finally, the latest development trend of GHz lasers is summarized. It provides a reference for the relevant personnel who carry out the research on GHz repetition rate femtosecond lasers later.

Abstract:With the continuous expansion of application scenarios and measuring range of laser vibrometer, its calibration becomes more and more important. However, according to the current calibration standard of vibrometer, the whole machine calibration under high frequency and high speed environment cannot be realized, so it is urgent to improve the calibration method in this respect. In recent years, researchers have used non-mechanically modulated light in the calibration and testing of vibrometers, built theoretical models and obtained calibration test data. This paper analyzes these theoretical models and experimental data, classifies relevant methods according to different optical modulation generation positions and core modulation devices, and introduces their working principles, system structure and main parameters. It then compares and analyzes the calibration functions and application scope of different methods, and finally looks forward to the development potential and research direction of relevant methods. It provides a reference for further research on the calibration technology of vibrometer.

Abstract:To address the problem that the ICP algorithm relies heavily on initial values and may fall into local optimum solutions during the alignment process, an improved ICP algorithm incorporating geometric features is proposed. Using the feature that the part has rich geometric parameters, the curvature-based voxel sampling is first performed on the measured point cloud to preserve the geometric features as much as possible, and then the curvature difference and normal vector angle difference of the point cloud are introduced into the target error function of the algorithm for iterative calculation, and the final alignment results are obtained when the target error function reaches a set threshold. Experimental verification of point cloud alignment is carried out using standard parts with complex surfaces, and the results show that the improved ICP algorithm incorporating geometrical features converges faster and has lower errors than the ICP algorithm, and that the improved ICP algorithm incorporating geometrical features reduces the need for initial values and simplifies the point cloud alignment process while maintaining the accuracy of the alignment compared with the fast global registration plus ICP alignment algorithm. The improved ICP algorithm incorporating geometric features provides a strong support to facilitate accurate digital measurement and evaluation of parts, and has a technical reference value.

Abstract:The fast Fourier transform (FFT) is commonly used for signal frequency estimation, and the zero-filling method can reduce the quantization error of the amplitude spectrum frequency search interval, but it will increase the computational effort of frequency estimation exponentially. In this paper, a fast and high-precision frequency estimation algorithm based on FFT amplitude-phase combination is proposed. First, the amplitude spectrum and its peak position are determined by using the spectrum sequence of signal sampling and the difference between tail and head samples. Then, the quantization error correction value of the frequency search interval is determined by the spectrum sequence peak position in the amplitude spectrum and the tail sample difference of signal sampling. Therefore, the proposed method utilizes both the position information and the phase information of the peak value of the amplitude spectrum. Simulation results show that the proposed algorithm has lower computational complexity and higher positioning accuracy compared with the FFT algorithm based on amplitude spectrum search only.

Abstract:In order to study the effect of the variation of the received signal amplitude of the acoustic velocity method on the temperature field reconstruction, a thermal calibration wind tunnel simulation test was conducted based on the acoustic thermometry method to successfully simulate the temperature field reconstruction at the exit of an aero-engine combustion chamber. Firstly, features are extracted from the received signal data and a feature matrix is established to feedback the change of signal amplitude. Then, based on the collected signal data, the temperature field reconstruction is carried out by the least squares method. Finally, the effect of the change of signal amplitude on the temperature field reconstruction by the acoustic velocity method is analyzed by comparing the actual effects of temperature field reconstruction under different feature matrices. Through experimental verification, it can be seen that: the larger the received signal amplitude is, the larger the root mean square error of the reconstructed temperature field is, when the amplitude is 40% greater than the theoretical value, the root mean square error is 14.38% greater than the theoretical value; the smaller the received signal amplitude is, the larger the maximum relative error of the reconstructed temperature field is, when the amplitude is 40% less than the theoretical value, the maximum relative error is 44.3762 K greater than the theoretical value.The research in this paper has an important technical reference value to promote the development of acoustic temperature measurement technology in the field of aero-engine combustion chamber outlet temperature field testing.

Abstract:The rapid acquisition of 3D surface information and measurement of dimensions of workpieces online in the flow production lineis strongly required in the current intelligent upgrading process of manufacturing industries such as roll forming. The speckle projection based 3D reconstruction method can reconstruct the 3D data of object surface only by using a single object speckle image, which has certain advantages in the rapid measurement of workpieces online. In this paper, on the basis of optimizing the time-consuming corresponding point search algorithm in speckle 3D reconstruction, a rapid 3D measurement system for online workpiece measurement that is suitable for the roll forming production line is developed. The experimental results show that the system has a fast 3D data reconstruction speed, and the measurement error is within 0.035 mm, which can meet the requirements of rapid online measurement of 3D structural dimensions of rolled parts.

Abstract:With the continuous improvement of gas turbine, its blade temperature is getting closer to the temperature tolerance limit of materials. However, the current temperature measuring instruments on the market cannot accurately reflect the blade temperature and distribution. To solve this problem, a scanning radiation temperature measuring system is designed. When the system is working, the probe is installed on the engine casing and aimed at the surface of the blade. The infrared radiation emitted by the blade is reflected by the reflector at the front end of the probe and enters the probe. It is transmitted to the controller through the optical fiber at the end of the probe, and the optical signal is processed and converted into a temperature value. Through the coupling simulation of the flow field and the temperature field of the scanning probe, the results show that the whole probe can be effectively protected in the engine when 25 ℃ cooling gas is introduced at a flow rate of 0.1 kg/s and the probe detection time is not more than 15 s; the fluid pressure at the end of the probe is about 17.0 MPa, which is much higher than the gas pressure of 1.4 MPa, so this area can isolate the high-temperature gas to prevent it from entering the probe and contacting the reflector. Experiments were carried out in the laboratory to verify the system. The results showed that the repeatability and stability of the probe at each temperature point did not exceed 7.5 ℃,that the temperature measurement system can meet the needs of turbine blade surface temperature measurement.

Abstract:The unified evaluation method of spatial straightness deviation in Cartesian coordinate system has not been established at present. For the situation, an evaluation method of spatial straightness deviation in Cartesian coordinate system based on point features is proposed in this paper. Using the relationship between the spatial straightness deviation measurement model and the point characteristics, and based on the spatial straightness measurement method in Cartesian coordinate system, the mathematical models for the spatial straightness deviation evaluation in Cartesian coordinate system are established. On the basis of the cross-section measurement method, the measurement model of spatial straightness deviation is established. Based on the mathematical equation of arbitrary symmetric quadratic curves in space, the least square measurement section profile curve is constructed to solve the problem of obtaining the center of the measured section profile. Finally, the accurate evaluation of the spatial straightness deviation is realized according to the point characteristic relationship. Moreover, the rationality and accuracy of the proposed method are verified through practical tests, which provides a strong support for promoting the development of spatial straightness measurement technology.

Abstract:In order to realize numerical control transformation and application of SJJF digital display manual indexing head with highaccuracy, meet practical requirements of automatic calibration and detection of angular displacement sensor used in an aeroengine performance test bench, and solve the time-consuming and labor-intensive problem of manual angle indexing, a design scheme for automatic angle indexing control system is proposed. It uses a programmable logic controller (PLC) in conjunction with a special ladder diagram programming command torealize automatic digital acquisition of angle grating signal, angle value conversion, proportion integration differentiation (PID) control positioning and grating zeroing, which can effectively meet calibration accuracy requirements such as linearity and sensitivity of the angular displacement sensor for platform, save 70% of original manual calibration time, improve angle indexing efficiency and reduce labor intensity.

Abstract:The current calibration method of pressure parameters of a flight test system is laboratory calibration, which is time-consuming and has the problem that multiple dismounting operations may damage the sensor's interface. In this paper, a field calibration method of pressure parameters is studied, and the in-situ comparison calibration is realized under real working conditions. The characteristic of the magnitude of the standard pressure sensor under the condition of temperature compounding is obtained through experiments, and the temperature compensation model is constructed to realize the accurate acquisition of the standard pressure value. A calibration device consisting of three standard pressure sensors with different ranges, ambient temperature, humidity and atmospheric pressure sensors, and field calibration software was developed. The rationality of the calibration method and device was verified through preliminary experiments. This method can be used as an effective supplement to laboratory calibration, reducing the labor and time cost of calibration and improving the efficiency of flight tests.

Abstract:Ultra-high shock acceleration sensor plays an important role in weapon development, aerospace and other high overload measurements. Based on the primary calibration by laser interferometry, an ultra-high shock acceleration calibration device is established to calibrate the high shock acceleration. The composition and design optimization of the system are introduced. A suitable demodulation program and filtering algorithm are designed to demodulate the original Doppler signal. In the range of peak shock acceleration of 1 × 10⁴ g ~ 2.5 × 10⁵ g and shock pulse width of 20 ~ 50 μs, the semi-sinusoidal shock waveform is absolutely reproduced. Finally, the uncertainty components affecting the measurement results are evaluated. The measurement uncertainty of ultra-high shock acceleration is 8%, which is of great significance for the calibration of shock acceleration above 2 × 10⁵ g.

Abstract:At present, pointer pressure gauges are often calibrated using image method, but there are some problems in the measurement process, such as difficult to segment the pointer of the pressure gauge, difficult to separate the background and low recognition accuracy. In order to solve the above problems, combined with the appearance size of the pressure gauge dial of different specifications, the automatic measurement and calibration system of the pressure gauge is studied. Firstly, the optimal working distance between the camera and the pressure gauge is automatically determined according to the external dimension of the pressure gauge dial within the field of view of the industrial camera. Secondly, the image sharpness is evaluated by the image edge gradient value, and the camera focusing is automatically completed. Finally, the polar coordinate transformation method is used to realize the functions of scale line positioning, pointer extraction, real-time reading and so on. The test results show that the system is suitable for the calibration of pointer pressure gauges with shell diameters of 40, 60, 100, 150, 200 and 250 mm.

Abstract:Embedded operating system plays a crucial role in the process of instrument intellectualization. By analyzing the technical architecture and distributed and microkernel characteristics of Harmony OS, comparing with the existing domestic and foreign embedded operating systems, and combining with the actual application cases of data acquisition of measuring instruments, it is concluded that Harmony OS has superiority in independence and controllability, real-time and smooth connection, and meets the needs of measuring instruments for operating system.

Abstract:Through the analysis, research and judgment of the current status of military measurement capability, considering the deficiencies of the characteristic measurement capability, frontier exploration capability and digital basic capability of military measurement, combined with the new situation and new requirements faced by military measurement in the new era, this paper discusses the innovative development direction of military measurement capability. It puts forward relevant development suggestions on strengthening the research capability of frontier technology, consolidating the measurement capability with military characteristics, and developing the digital basic capability, which can provide reference for the next development path of military measurement capability.

Abstract:Aiming at the measurement planning problems caused by the huge parameter system and long measurement chain in the equipment development process, the general methods of establishing measurement models, designing measurement schemes and evaluating measurement results are analyzed, and the basic ideas to solve the measurement problems in equipment development are proposed, which provides a reference for the formation of universal, procedural and standardized measurement solutions.