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Laser based method for dynamic calibration of thermocouples
摘要： In dynamic temperature measurement, thermocouple sensors are widely used in harsh environments, and their dynamic characteristics directly affect the accuracy of dynamic temperature measurement. When the dynamic characteristics do not meet the requirements of dynamic test, dynamic errors will occur. In order to obtain the dynamic characteristics, it is necessary to calibrate the thermocouple dynamically. In this paper, a dynamic calibration system for the thermocouple was built. In the system, a high power laser was used to generate pulse temperature excitation. In order to realize the uniform heating, the laser beam homogenization system based on microlens array was studied and added to the dynamic calibration system. The homogenization system was designed and simulated, and the uniformity of the laser spot was measured after homogenization. A K-type butt-welded thermocouple was dynamically calibrated by using the dynamic calibration system. The dynamic mathematical model of the thermocouple was obtained by the system identification method, and the dynamic characteristics of the thermocouple were analyzed.
关键词： pulse excitation,laser,dynamic calibration,microlens array,thermocouple
更新于2025-09-23 15:21:01
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An On-Orbit Dynamic Calibration Method for an MHD Micro-Angular Vibration Sensor Using a Laser Interferometer
摘要： The magnetohydrodynamic (MHD) micro-angular vibration sensor is a signi?cant component of the MHD Inertial Reference Unit (MIRU) and measures micro-amplitude and wide frequency angular vibration. The MHD micro-angular vibration sensor must be calibrated in orbit since the ground calibration parameters may change after lift-off. An on-orbit dynamic calibration method for the MHD micro-angular vibration sensor is proposed to calibrate the complex sensitivity of the sensor in high frequency. An absolute calibration method that combines a homodyne laser interferometer and an angular retrore?ector was developed. The sinusoidal approximation method was applied, and the calibration system was established and tested using a manufactured MHD sensor. Furthermore, the measurement principle and installation errors were analyzed, including the eccentric installation error of the retrore?ector, the tilt installation error of the retrore?ector, and the optical path tilt error. This method can be realized within a rotation range of ±3? and effectively avoid the installation error caused by mechanical errors. The results indicate that the calibratable angular vibration frequency range is 25–800 Hz, and the angular velocity range is 0.076–7590 mrad/s. The expanded uncertainties of the sensitivity amplitude and phase shift of the calibration system for the MHD micro-angular sensor are 0.04% and 1.2? (k = 2).
关键词： micro-angular vibration sensor,laser interferometer,on-orbit dynamic calibration,MHD,installation error,sensitivity
更新于2025-09-16 10:30:52
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Calibration Method for Dynamic Deflection Measurement of Bridges by Photogrammetry
摘要： Heavy vehicular traffic and aggressive environmental conditions can cause unexpected bridge deterioration, thus, periodic inspections to identify and assess possible defects are required. One indicator is the amount of vertical deflection that occurs during loading. Some different types of transducers can be used to measure the deflection. One of them is the photogrammetry. It is a typical noncontact measurement method. Unfortunately, it is difficult to calibrate this type of instruments. The key point is the evaluation of the dynamic deflection measurement capability. A dynamic calibration system of bridge photogrammetric measurement system was composed of the motorized linear stage, LED target and computer. The Fréchet distance was used as a model to evaluate the dynamic deflection measurement capability of bridge deflection photogrammetry. The photogrammetric bridge deflection measuring instruments are products of BIOET, which are used to carry out the measurement experiment. The results show that this system can calibrate the dynamic deflection measurement error of photogrammetric bridge deflection measuring instruments. Fréchet distance can reflect the relationship between the curves. This evaluation method is more accurate than the current evaluation method based on the error of indication of maximum dynamic deflection.
关键词： bridge deflection,photogrammetry,dynamic calibration,Fréchet distance
更新于2025-09-11 14:15:04