Estimating the accuracy of the technique of reconstructing the rotational motion of a satellite based on the measurements of its angular velocity and the magnetic field of the Earth

The paper has studied the accuracy of the technique that allows the rotational motion of the Earth artificial satellites (AES) to be reconstructed based on the data of onboard measurements of angular velocity vectors and the strength of the Earth magnetic field (EMF). The technique is based on kinematic equations of the rotational motion of a rigid body. Both types of measurement data collected over some time interval have been processed jointly. The angular velocity measurements have been approximated using convenient formulas, which are substituted into the kinematic differential equations for the quaternion that specifies the transition from the body-fixed coordinate system of a satellite to the inertial coordinate system. Thus obtained equations represent a kinematic model of the rotational motion of a satellite. The solution of these equations, which approximate real motion, has been found by the least-square method from the condition of best fitting between the data of measurements of the EMF strength vector and its calculated values. The accuracy of the technique has been estimated by processing the data obtained from the board of the service module of the International Space Station (ISS). The reconstruction of station motion using the aforementioned technique has been compared with the telemetry data on the actual motion of the station. The technique has allowed us to reconstruct the station motion in the orbital orientation mode with a maximum error less than 0.6° and the turns with a maximal error of less than 1.2°.     

Longitudinal dependence of the H<Superscript>+</Superscript> concentration distribution in the plasmasphere according to <Emphasis Type="Italic">INTERBALL-1</Emphasis> satellite data

The paper has presented a study of the dependence of the H⁺ ions concentration in the plasmasphere on geographic longitude. A vast database of measurements of the cold plasma density by the Alpha-3 instrument on board the INTERBALL-1 satellite has been used for the study. Based on these measurements, a dependence of the H⁺ ions concentration in the filled magnetic flux tube in the plasmasphere in the equatorial plane under quiet geomagnetic conditions has been obtained as a function of geographic longitude. Studies have been performed for two seasons, summer and winter. It has been shown that, during the summer in the near-midnight sector, the minimum in the H⁺ concentration falls within geographic longitudes of 270°–315°. The ratio of the concentration of H⁺ ions at various longitudes could reach a factor of three. During the winter, in the near-noon sector, the maximum of the H⁺ ions concentration falls within longitudes of 180°–225°, whereas the concentration ratio could reach a factor of 2.2.     

Some problems of identifying types of large-scale solar wind and their role in the physics of the magnetosphere

This paper discusses the errors in analyzing solar-terrestrial relationships, which result from either disregarding the types of interplanetary drivers in studying the magnetosphere response on their effect or from the incorrect identification of the type of these drivers. In particular, it has been shown that the absence of selection between the Sheath and ICME (the study of so-called CME-induced storms, i.e., magnetic storms generated by CME) leads to errors in the studies of interplanetary conditions of magnetic storm generation, because the statistical analysis has shown that, in the Sheath + ICME sequences, the largest number of storm onsets fell on the Sheath, and the largest number of storms maxima fell at the end of the Sheath and the beginning of the ICME. That is, the situation is observed most frequently when at least the larger part of the main phase of storm generation falls on the Sheath and, in reality, Sheath-induced storms are observed. In addition, we consider several cases in which magnetic storms were generated by corotating interaction regions, whereas the authors attribute them to CME.     

Dynamics of electron fluxes in the slot between radiation belts in November–December 2014 according to data of the <Emphasis Type="Italic">Vernov</Emphasis> satellite

The variations in the spatial structure and time in electron fluxes with E = 235–300 keV in the slot region (2 < L < 3) between the radiation belts in the period of November 1, 2014 through December 8, 2014 during weak and moderate geomagnetic disturbances (Kp < 4, Dst >–60 nT) are analyzed based on the data of the RELEC complex on board the Vernov satellite (the height and inclination of the orbit are from 640 to 830 km and 98.4°, respectively). Irregular increases in the fluxes of such electrons and formation of a local maximum at L ~ 2.2–3.0 were observed. It has been shown that the intensity of this maximum is inversely proportional to the L value and grows with an increase in the geomagnetic activity level. New features discovered for the first time in the dynamics of radiation belt electrons manifest in the variations in the local structure and dynamics of fluxes of subrelativistic electrons in the slot region.     

Study of the magnetospheres of active regions on the sun by radio astronomy techniques

In the 1990s, based on detailed studies of the structure of active regions (AR), the concept of the magnetosphere of the active region was proposed. This includes almost all known structures presented in the active region, ranging from the radio granulation up to noise storms, the radiation of which manifests on the radio waves. The magnetosphere concept, which, from a common point of view, considers the manifestations of the radio emission of the active region as a single active complex, allows one to shed light on the relation between stable and active processes and their interrelations. It is especially important to identify the basic ways of transforming nonthermal energy into thermal energy. A dominant role in all processes is attributed to the magnetic field, the measurement of which on the coronal levels can be performed by radio-astronomical techniques. The extension of the wavelength range and the introduction of new tools and advanced modeling capabilities makes it possible to analyze the physical properties of plasma structures in the AR magnetosphere and to evaluate the coronal magnetic fields at the levels of the chromosphere–corona transition zone and the lower corona. The features and characteristics of the transition region from the S component to the B component have been estimated.     

高温空气传输特性对边界层稳定性及转捩预测的影响

为了研究黏度和导热系数对边界层内基本流和流动稳定性的影响,首先通过分析比较Sutherland公式和目前常用的Gupta等人的拟合关系式,建立了高温气体下黏度和导热系数的计算模型,并分别将Sutherland公式和新建立的计算模型应用于7组元化学平衡流的平板模型,在马赫数为10,16和20,飞行高度为30-5km等条件下分别对黏度和导热系数的模型进行比较.计算结果表明:在高温范围内,黏度和导热系数均影响着边界层的基本流、流动稳定性及转捩预测,且两者影响的趋势相反,黏度的增加、导热系数的减小都能使扰动的增长率变大,增长区变宽,转捩位置提前.      

双馈型风电系统变流器控制参数对振荡模态的影响

研究双馈型风力发电系统变流器控制参数对振荡模态的影响。在MATLAB/Simulink中建立系统详细的小信号模型,利用特征值分析和相关因子分析,对机网相互作用振荡模态进行辨识和分类。通过改变变流器控制参数,研究振荡模态的变化特性。最后,在MATLAB/Simulink上进行仿真验证。研究表明,优化变流器控制参数,可有效抑制振荡。     

改进型滑模变结构电机控制的脉振电流注入法研究

为了提高永磁同步电机无位置传感器技术的控制性能,在电机动态品质优化的研究中,以滑模变结构控制器替代传统的PI控制器,采用新型趋近律函数改进滑模控制器的输出模型,削弱了传统滑模控制存在的抖振,提高了控制系统的抗干扰能力。在分析无位置传感器技术时,引入高通谐振滤波器,采用具备以高信噪比为特点的两相静止坐标系下高频脉振电流注入法。仿真结果表明,在带高通谐振滤波器的高频脉振电流注入法中运用滑模变结构控制器,提高了转子位置估计的精度,增强了控制系统的鲁棒性。     

基于变刚度特性的轴流压气机叶型重构方法研究

为能准确预估轴流压气机叶片在工作状态下的形状,基于流固耦合迭代策略,考虑离心力和气动力对叶片变形的作用,发展了一种适用于轴流压气机的叶型重构方法。在构型转化过程中,计入了叶片受力载荷随叶型变化的非线性效应以及叶片的变刚度特性。采用叶片变形后状态的受力载荷与刚度矩阵计算叶片节点位移,反复迭代修正热态叶片形状,最终获得满足精度要求的热态叶型数据。利用所提出的方法,对Stage 37的转子叶片进行了叶型重构,经20步迭代计算可获得最大残差小于10-4mm量级的热态叶型,通过与试验数据的对比分析,验证了重构算法的可靠性和工程实用性。     

Development of wireless strain-gauge measurement system for structural tests

A wireless sensor system for data acquisition and processing during structural and fatigue tests is considered. A prototype of wireless strain-gauge measurement system is used in fatigue tests of a utility helicopter’s main rotor hub. The setup of the test rig and software are described.