光纤陀螺组件误差标定ARLS算法

捷联惯性导航系统误差参数标定的准确程度对于系统的导航和定位精度具有重要影响.针对常规速率标定法不能辩识陀螺零偏,未充分预热时光纤陀螺的误差标定易受温度变化影响这两个问题,提出了一种用于光纤陀螺捷联惯性导航系统的新标定算法--自适应递推最小二乘法(ARLS).在建立光纤陀螺误差及其补偿模型的基础上,通过大量温度实验研究了自适应遗忘因子的求取方法,详细推导了ARLS算法及其实现思路.最后通过算法仿真和速率试验证明了在器件特性不稳定条件下,ARLS算法能有效辨识陀螺的误差参数及减小温度变化对光纤陀螺误差标定的影响.     

Study on error calibration of fiber optic gyroscope under intense ambient temperature variation

A novel adaptive forward linear prediction (FLP) denoising algorithm and a temperature drift modeling and compensation concept based on ambient temperature change rate for fiber-optic gyroscope (FOG) are presented to calibrate the errors caused by intense ambient temperature variation. The intense ambient temperature variation will bring large temperature errors, which will degrade the performance of FOG. To analyze the temperature variation, characteristics of FOG temperature experiments are developed at first. Then the adaptive FLP denoising algorithm is employed to eliminate the noise aiming at reducing noise interference. After that, a simple modeling concept of building the compensation model between temperature drift and ambient temperature change rate is first to be given (we have not found a report of better results in any literature). The semiphysical simulation results show that the proposed method significantly reduces the noise and drift caused by intense ambient temperature variation.     

光纤陀螺的温度试验与误差补偿

分析了光纤陀螺的温度特性及非线性特性,并在组建光纤陀螺温度试验系统的基础上,进行了全温度范围下的位置试验和角速率试验,研究不同的温度及输入角速率对光纤陀螺输出的影响.根据试验结果,分别建立了光纤陀螺零偏的温度模型以及标度因数的温度和非线性模型,并采用最小二乘法拟合模型的参数.通过实测数据进行仿真验证,结果表明,建立的模型能够较好地描述光纤陀螺的温度及非线性特性,利用该模型进行光纤陀螺的温度和非线性误差补偿,取得了较好的效果,光纤陀螺的测试精度得到了较大程度的提高.     

A novel intelligent strategy for improving measurement precision ofFOG

This paper discusses a neural network-based strategy for reducing the existing errors of fiber-optic gyroscope (FOG). A series-single-layer neural network, which is composed of two single-layer networks in series, is presented for eliminating random noises. This network has simpler architecture, faster learning speed, and better performance compared to conventional backpropagation (BP) networks. Accordingly after considering the characteristics of the power law noise in FOG, an advanced learning algorithm is proposed by using the increments of errors in energy function. Furthermore, a radial basis function (RBF) neural network-based method is also posed to evaluate and compensate the temperature drift of FOG. The orthogonal least squares (OLS) algorithm is applied due to its simplicity, high accuracy, and fast learning speed. The simulation results show that the series-single-layer network (SSLN) with the advanced learning algorithm provides a fast and effective way for eliminating different random noises including stable and unstable noises existing in FOG, and the RBF network-based method offers a powerful and successful procedure for evaluating and compensating the temperature drift     

Calculation of the Characteristics of Infrared Synchrotron Radiation

Subroutines for calculating the spectral and angular characteristics of infrared synchrotron radiation are developed. Corresponding calculations are carried out for a number of proton and electron accelerators. The results obtained enable methods to be developed for beam diagnostics as well as highly sensitive detectors of infrared radiation for remote contactless nondestructive diagnostics and for investigating bunches and high-speed processes in ring-type (CERN/SEPS-LHC) and linear (GSI bunch target) accelerators, and also the thermal fields in nuclear power plants.Translated from Izmeritel’naya Tekhnika, No. 3, pp. 53–58, March, 2005.     

Angular checking systems having vertical base arms

A brief survey is presented of angular checking systems produced individually or in regular production. Formulas are given for the errors of measurement due to error in certifying the length of the base lever and to the thermal expansion o the main components. A scheme and design are presented for a system having the base lever vertical and thermal compensation applied to the main links that govern the basic error.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 27–30, February, 1995.     

Study on the thermally inducedspindle angular errors of a five-axis CNC machine tool

Thermally induced spindle angular errors of a machine tool are important factors that affect the machining accuracy of parts. It is critical to develop models with good generalization abilities to control these angular thermal errors. However, the current studies mainly focus on the modeling of linear thermal errors, and an angular thermal error model applicable to different working conditions has rarely been investigated. Furthermore, the formation mechanism of the angular thermal error remains to be studied. In this study, an analytical modeling method was proposed by analyzing the formation and propagation chain of the spindle angular thermal errors of a five-axis computer numerical control (CNC) machine tool. The effects of the machine tool structure and position were considered in the modeling process. The angular thermal error equations were obtained by analyzing the spatial thermoelastic deformation states. An analytical model of the spindle angular thermal error was established based on the geometric relation between thermal deformations. The model parameters were identified using the trust region least squares method. The results showed that the proposed analytical model exhibited good generalization ability in predicting spindle pitch angular thermal errors under different working conditions with variable spindle rotational speeds, spindle positions, and environmental temperatures in different seasons. The average mean absolute error (MAE), root mean square error (RMSE) and R² in twelve different experiments were 4.7 μrad, 5.6 μrad and 0.95, respectively. This study provides an effective method for revealing the formation mechanism and controlling the spindle angular thermal errors of a CNC machine tool. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00409-x     

简易光纤陀螺测试系统的设计与实现

光纤陀螺是20世纪70年代发展起来的一种新型惯性仪器，由于具有精度高、抗干扰能力强、预热时间短等一系列优点，在各个领域得到了广泛的应用。而要保证光纤陀螺的测试精度，一套高精度的测试系统是必不可少的。论文针对模拟光纤陀螺进行测试系统设计，以往采用较多的测试方法为：首先对信号进行A/D转换，再利用计算机进行数字信号采集；但由于AD转换存在精度低及连续性差等缺点，大大限制了测试系统的精度。基于这一方面考虑，论文中设计了一种简易的高精度光纤陀螺多路测试系统，直接对输出的模拟信号进行采集，再利用采集到的电压信号进行解算，得到角速度值。在组建完整套测试系统后，对设计的测试系统进行了试验验证及精度标定，试验结果表明，该测试系统具有较高的精度，完全可以满足中低精度模拟光纤陀螺的测试要求。     

Thermal Behavior of a Multi-layered Thin Slab Carrying Periodic Signals Under the Effect of the Dual-Phase-Lag Heat Conduction Model

The thermal behavior of a two–layered thin slab carrying periodic signals under the effect of the dual-phase-lag heat conduction model is investigated. Two types of periodic signals are considered, a periodic heating source and a periodic imposed temperature at the boundary. The deviations among the predictions of the classical diffusion model, the wave mode, and the dual-phase-lag model are investigated. Analytical closed-form solutions are obtained for the temperature distribution within the slab. The effect of the angular frequency, thickness of the plate, dimensionless thermal relaxation time, dimensionless phase-lag in temperature gradient, thermal conductivity, and thermal diffusivity on the temperature distribution of the slab was studied. It is found that the deviations among the three models increase as the frequency of the signals increases and as the thickness of the plate decreases. It is found that the use of the dual-phase-lag heat conduction model is necessary when the metal film thickness is of order 10^–6 m and the angular frequency of the signals is of order 10¹²rad · s^–1.     

Measurement of the thermal activity of dielectric liquids with an accuracy of ∼ 104

A method of measuring small (∼ 10⁻⁴) relative changes in the thermal activity of liquids is developed. A theoretical substantiation of its accuracy is given based on an investigation of the factors responsible for errors in the experiment. Results of experiments on a study of the temperature dependence of the thermal activity of a solution of polystyrene in toluene are reported.     

弹载光纤陀螺旋转惯组误差自补偿技术

目前弹载惯性测量组合测试标定精度受外界干扰影响较大,特别是光纤陀螺温度稳定性低,易受环境温度影响参数变化,导致误差补偿效果不好。针对该问题,提出设计一种光纤陀螺旋转惯性测量组合。在惯性测量组合外加旋转轴,在导弹飞行过程中使惯性测量组合绕旋转轴连续旋转,将射前补偿不完全误差调制为周期项,从而达到误差自补偿的效果。理论分析和仿真结果表明,通过旋转不仅能自动补偿与转轴垂直方向惯性仪表的常值误差和部分安装误差,而且能补偿加速度计部分一次项误差、二次项误差和部分交叉轴耦合项误差,选择合适的旋转方案还可以完全消除旋转速度与陀螺仪标度因数误差、安转误差的耦合误差。     

Optimization of thermo‐elasto‐plastic processes using Eulerian sensitivity analysis

A computational scheme for the analysis and optimization of quasi‐static thermo‐mechanical processes is presented in this paper. In order to obtain desirable mechanical transformations in a workpiece using a thermal treatment process, the optimal control parameters need to be determined. The problem is addressed by posing the process as a decoupled thermo‐mechanical finite element problem and performing an optimization using gradient methods. The forward problem is solved using the Eulerian formulation since it is computationally more efficient compared to an equivalent Lagrangian formulation. The design sensitivities required for the optimization are developed analytically using direct differentiation. This systematic design approach is applied to optimize a laser forming process. The objective is to maximize the angular distortion of a specimen subject to the constraint that the phase transition temperature is not exceeded at any point in the model. Copyright © 2003 John Wiley & Sons, Ltd.     

高精度光纤陀螺信号的在线建模与滤波

针对高精度光纤陀螺随机误差,在分析其一般时间序列模型的基础上,提出了一种改进型二阶自回归AR(2)模型,可以在线建立光纤陀螺随机误差模型.根据该模型,采用卡尔曼滤波算法,实现了光纤陀螺惯导系统在对准与导航过程中光纤陀螺随机误差的实时滤波.滤波结果和Allan方差分析证明,光纤陀螺信号中角随机游走、零偏不稳定性、速率随机游走、速率斜坡和量化噪声五项噪声源误差系数都小于滤波前的二分之一,有效减小了光纤陀螺随机误差,提高了光纤陀螺精度.     

A CFD Study on a Calibration System for Contact Temperature Probes

Surface-temperature measurements by means of contact probes require a detailed investigation of the probe-surface interaction. For an accurate calibration of such probes, the heat transfer processes involved in contact measurements must be well known and the impact of any influence parameters must be taken into account. At present, contact probes are generally calibrated by means of a temperature-controlled hot plate. A calibration system for contact surface-temperature probes, based on such a hot plate, was developed at INRIM. It covers the temperature range from ambient to 350 °C. The reference temperature is available on the upper surface of a metal block and is determined by linear extrapolation of the readings of three calibrated thermometers embedded into the block at different depths. However, the actual temperature of the reference surface largely depends on the sensor-to-surface interaction. The contact thermal resistance, the thermal conductivity of the block, the geometry of the probe, and the temperature of the surrounding fluid are just some of the parameters that affect a calibration and that may cause measurement errors if they are not properly taken into account and corrected for. Better insight into the interaction between the surface and the probe is therefore required. Since the experimental evaluation of measurement errors is not straightforward, mathematical modeling could represent a crucial tool to better understand the interactions between the probe and the calibration system. In this paper, a finite-element numerical model of the INRIM calibration system was developed in order to investigate the temperature field across the reference block as well as on its surface during a calibration. The thermal load introduced by a commercial contact probe during a calibration was also included in the simulation and its effect on the temperature field was studied. In order to obtain a detailed mathematical model, the surrounding air was also included in the simulation, avoiding the imposition of boundary conditions at the interface between solid parts and fluid. The proposed model was validated by comparing the results obtained with the available experimental data.     

Knudsen-effect errors with transient line-source measurement in fluids

This paper decribes the Knudsen-effect errors of the transient line-source method used for accurate measurements of the thermal conductivity and thermal diffusivity of fluids. The analysis demonstrates that the instrument can be used with a good accuracy (>0.5%) to lower densities than previously thought. The principal errors are illustrated by measurements on propane in the temperature range 250–300 K at densities less than 9 kg · m^–3.     

A Method of Measuring the Angular Coordinates for Objects Moving in a Group

A method is proposed for measuring the angular coordinates of objects moving in a group. It is based on the statistical characteristics of the complex reflection coefficients of a group and the errors of measuring the velocities of the members. Inverse antenna aperture synthesis is used to increase the angular resolution.Translated from Izmeritel’naya Tekhnika, No. 3, pp. 12–18, March, 2005.     

Thermo-elastic-plastic porous material undergoing thermal loading

A model for predicting elastic–plastic stresses within a surface-heated porous structure has been developed. The relevant phenomena for the moisture, pressure, temperature and displacement fields in thermo-elastic-plastic porous material are analysed. Considering mass and energy transfer processes, a set of governing differential equations is presented. The solution of the problem has been obtained with a finite difference scheme. The results demonstrate the influence of the evaporation mechanism on pressure and thermal stresses within the porous material.     

Development of a Laser Interferometric Dilatometer for Measurements of Thermal Expansion of Solids in the Temperature Range 300 to 1300 K

A laser interferometric dilatometer has been developed for measuring linear thermal expansion coefficients of reference materials for thermal expansion in the temperature range 300 to 1300 K. The dilatometer is based on an optical heterodyne interferometer capable of measuring length change with an uncertainty of 0.6 nm. Linear thermal expansion coefficients of silicon were measured in the temperature range 700 to 1100 K. The performance of the present dilatometer was tested by a comparison between the present data and the data measured with the previous version of the present dilatometer and the data recommended by the Committee on Data for Science and Technology (CODATA). The present data agree well with the recommended values over all the temperature range measured. On the other hand, the present values at lower temperatures are in poor agreement with the previous experimental data. The combined standard uncertainty in the present value at 900 K is estimated to be 1.1×10^–8 K^–1.     

Analysis of room temperature magnetic regenerative refrigeration

Results of a room temperature magnetic refrigeration test bed and an analysis using a computational model are presented. A detailed demonstration of the four sequential processes in the transient magnetocaloric regeneration process of a magnetic material is presented. The temperature profile during the transient approach to steady state operation was measured in detail. A 5 °C evolution of the difference of temperature between the hot end and the cold end of the magnetocaloric bed due to regeneration is reported. A model is developed for the heat transfer and fluid mechanics of the four sequential processes in each cycle of thermal wave propagation in the regenerative bed combined with the magnetocaloric effect. The basic equations that can be used in simulation of magnetic refrigeration systems are derived and the design parameters are discussed.     

Angular displacement fiber-optic sensor: theoretical and experimental study

An optical-fiber sensor based on twist-induced optical activity has been developed for measuring angular displacements at low temperature. The sensing part is composed of a fiber coil rotated between two points, which induces a twist of two sections of fiber. A theoretical study of the evolution of a general input state of polarization in the sensor gave us its main characteristics. Then experimental investigations permitted the construction of a sensor to take angular measurements over a 100-deg range with an accuracy of 0.2 deg. The thermal sensitivity of this kind of sensor is also briefly reported.