仿真软件YHSIM中“集中－混合”式数值积分技术

连续系统实时仿真软件ＹＨＳＩＭ中所采用的运用多种数值积分方法进行“集中一混合”式数值积分的积分程序的工作原理和实现技术,在本文中作了介绍。     

GLONASS-M卫星的研究与应用

对GLONASS-M卫星进行多方面的分析与描述,探讨它在原有GNSS接收机上新的应用并进行了试验验证。试验结果表明,GLONASS-M卫星从总体上提升了GLONASS系统的工作性能,包括精度与功能,揭开了卫星导航发展史上新的一页。     

高超声速进气道优化设计初探

以总压恢复系数为目标,利用无粘流斜激波关系式和约束最优化计算方法,在考虑混合气体比热随温度变化的条件下,对二维混压式高超声速进气道设计方法作了初步探索,利用数值模拟软件对附面层作了修正,研究了进气道的基本性能。数值模拟结果表明:该进气道在飞行马赫数Ma=4～6.5范围内能够可靠工作。     

风洞试验多通道数据采集与动态参数实时处理系统

为新型飞机发动机进气道动态畸变参数测试而研制了两代全数字化、智能化测试系统。64通道独立同时采样；高速32bit浮点运算DSP对畸变参数作实时处理；100Mbyte以上大容量在线存储器，存储全部原始数据、中间结果和处理结果；被测参数时间历程曲线、采样数据时间历程曲线及2D、3D动态图形和数表显示及输出；系统自检功能及坏点自动检测与修补功能；图形化及汉化菜单，友好的人机界面。硬件与软件的模块化与开放式结构，以便广泛应用于其他需要作多通道数据采集和动态参数实时处理的场合。     

Event-triggered adaptive fuzzy attitude takeover control of spacecraft

The problem of attitude takeover control of spacecraft by using cellular satellites with limited communication, actuator faults and input saturation is investigated. In order to lighten the communication burden of cellular satellites, an event-triggered control strategy is adopted. The filtered attitude information needs to be transmitted only when the defined measurement error reaches the event-triggered threshold in this strategy. Then, to deal with the unknown inertia matrix, actuator faults, external disturbances and the errors caused by event-triggered scheme, fuzzy logic systems is introduced to estimate the uncertainties directly. Combining fuzzy logic control strategy and the event-triggered method, the first event-triggered adaptive fuzzy control law is developed. Then, torque saturation of cellular satellites is further considered in the second control law, where the upper bound of the uncertainties is estimated by fuzzy logic systems. The resulting closed-loop systems under the two control laws are guaranteed to be bounded. Finally, the effectiveness of two proposed control laws is verified by the numerical simulations.     

Identification of uncatalogued LEO space objects by a ground-based EO array

A ground-based electro-optical (EO) array, deployed at the Jilin Space Tracking Base of Changchun Observatory, China, has been in operation since April 2017. The array has 8 small telescopes, each has an aperture of 15 cm and a field of view of 14° × 14°. On average, the array can collect angles data over 3–4 thousand Very Short Arcs (VSAs) of Low Earth Orbit (LEO) space objects each night. Correlation of the VSA angles data with the NORAD catalogue objects results in about 85% of all the VSAs being correlated to NORAD objects. The remaining 15% VSAs angles data could be supposed from uncatalogued objects. The Initial Orbit Determination (IOD) solutions of the VSAs with the range-search method and the association results of the IODs with the geometrical method are presented. The mean IOD success rate is about 91% and the True Positive (TP) rate is more than 86%. In addition, the classical Gauss, Laplace, Gooding and Double-r angles-only IOD methods are applied to process VSA angles data and their performance is assessed. The CBTA method is used to associate the IOD tracks and compared with the geometrical method. A set of procedures for identifying the uncatalogued objects based on the VSA angles data is designed. Processing of the VSA angles data from Aug 4 to Sep 30, 2017 reveals there are possibly 415 uncatalogued LEO objects.     

Characterizing slope correction methods applied to satellite radar altimetry data: A case study around Dome Argus in East Antarctica

Slope correction is important to improve the accuracy of satellite radar elevation measurements by mitigating the slope-induced error (SE), especially over uneven ground surfaces. Although several slope correction methods have been proposed, guidance in the form of stepwise algorithm on how to implement these methods in processing radar altimetric data at the coding level, and the differences among these methods need to be presented and discussed systematically. In this paper, three existing types of slope correction methods—the direct method (DM), intermediate method (IM), and relocation method (RM, further divided into RM1 and RM2)—are described in detail. In addition, their main differences and features for various scientific applications are analyzed. We conduct a systematic experiment with CryoSat-2 Low Resolution Mode (LRM) data in a physically stable area around Dome Argus in East Antarctica, where in-situ measurements were available for comparison. The slope correction is implemented separately using the three methods, with the latest high-accuracy Reference Elevation Model of Antarctica (REMA) as the a-priori topography model. The bias and precision of the slope-corrected CryoSat-2 data results from the RM2 is ?0.18 ± 0.86 m based on the comparison with the field Global Navigation Satellite System (GNSS) data. The results from the RM2 indicate higher precision compared to those from the RM1. According to the correlation analysis of the slope-corrected CryoSat-2 data results (RM1 and RM2), the bias enlarges and the precision becomes worse when the surface slope increases from 0 to 0.85°. After a comprehensively comparative analysis, we find that the results from the RM1 and RM2 are superior in precision (0.93 m and 0.86 m) with respect to the GNSS data. The relatively low precision (1.22 m) from the IM is due to the potential error from the a-priori digital elevation model (DEM). The DM has the lowest precision (2.66 m). Another experiment over rough topography in West Antarctica is carried out for comparison, especially between the RM1 (precision of 15.27 m) and RM2 (precision of 16.25 m). In general, the RM is recommended for the SE elimination among the three methods. Moreover, the RM2 is firstly considered over smooth topography due to the superior performance in bias and precision, while the RM1 is more suggested over the rough topography because of the slightly smaller bias and better precision. The IM relies much on the accuracy of the a-prior DEM and is not usually recommended, because of the strict requirement in the sampling time between the radar altimetry data and the a-priori DEM to avoid any surface change over time.     

在经济型数控车床上加工变螺距螺纹

在数控机床上加工恒螺距螺纹有G32,G92,G76指令,加工变螺距螺纹有G34指令。但是G34指令的使用要求有高档的数控系统,研究在经济型数控车床上加工变螺距螺纹,介绍一些宏程序的编制方法,实现对数控系统的二次开发。     

经济有效的轴承修复技术

铁姆肯公司已经开展了60多年的轴承修复业务,广泛应用于航空、交通、水泥建材、冶金、电力和造纸等行业.2006年以来,铁姆肯公司在中国的修复中心也已经为水泥、钢铁和造纸等客户修复轴承达到6800余套,其中50%以上为其他进口品牌的轴承.经验表明:修复后的轴承其使用周期完全能达到新轴承的同等使用周期要求.而且轴承修复与新品轴承采购相比在交货期和降低成本上更具有突出的优势.