再入制导和弹道跟踪误差分析

新一代可重复使用运载器对再入制导提出了更高地要求。目前的空间运输系统证明基于阻力加速度的制导方法是行之有效的。其基本概念是跟踪基准阻力加速度包线，在飞行过程中可根据需要更新这个包线。跟踪适当的阻力加速度包线保证了飞行器可以飞行准确的距离达到目标，同时满足弹道约束。在横向上，我们可采用类似于美国航天飞机的倾斜反转逻辑或航向角跟踪技术。本文推导出了基于反馈线性化的控制算法，并将其应用于可重复使用运载器纵向和横向的制导。最后，我们分析了阻力加速度跟踪的误差。     

A novel architecture of electro-hydrostatic actuator with digital distribution

To address the flow imbalance rapidly of the asymmetric Electro-Hydrostatic Actuator (EHA), this paper presents a novel architecture of asymmetric EHA with the Digital Distribution (EHA-DD). It also improves the flow nonlinearity and control accuracy of the pump, especially in the low-speed condition. The digital distribution with two High-Speed on–off Valves (HSVs) not only balances flow instead of the check valves, but also replaces the pump at the low-speed to control output flow by adjusting the PWM signal. The pump and HSVs are the crucial components to control flow output. Firstly, the flow calculation models of the pump and the duty ratio inversed model of the HSV are obtained through experimental tests and the identification method. To get the control input signal for the required flow, the pump speed and PWM duty ratio for the HSVs are inversed to compensate for flow output. Further, a multimode digital flow distribution control method based on pump speed, mainly including the pump-controlled mode for large flow demand and valve-controlled mode for little flow demand, is proposed to control the accurate flow output actively. The step extension experiments based on the flow calculation models are conducted on the EHA-DD prototype under elastic, opposite varying load. The results demonstrate that the EHA-DD realizes little position error by accurate flow control, and it is also beneficial to improve the service life of the pump.     

WSO-UV project

During last three decades, astronomers have enjoyed continuous access to the 100–300 nm ultraviolet (UV) spectral range where the resonance transitions of the most abundant atoms and ions (at temperatures between 3000 and 300 000 K) reside. This UV range is not accessible from ground-based facilities. The successful International Ultraviolet Explorer (IUE) observatory, the Russian ASTRON mission and successor instruments such as the Galaxy Evolution Explorer (GALEX) mission or the COS and STIS spectrographs on-board the Hubble Space Telescope (HST) prove the major impact of observations in the UV wavelength range in modern astronomy. Future access to space-based observatories is expected to be very limited. For the next decade, the post-HST era, the World Space Observatory – Ultraviolet (WSO–UV) will be the only 2-m class UV telescope with capabilities similar to the HST. WSO–UV will be equipped with instruments for imaging and spectroscopy and it will be a facility dedicated, full-time, to UV astronomy. In this article, we briefly outline the current status of the WSO–UV mission and the science management plan.     

Optimization and verification of free flight separation similarity law in high-speed wind tunnel

Based on the similarity of separation time, a similarity law optimization method for high-speed weapon delivery test is derived. The typical separation state under wind load is simulated by the numerical method. The real separation data of aircraft, separation data of previous test methods, separation data of ideal wind tunnel test of previous methods, and simulation data of the proposed optimization method are obtained. A comparison of the data shows that the method proposed can improve the performance of tracking. Similarity law optimization starts with the development of motion equations and dynamic equations in the windless state to address the problems of mismatching between vertical and horizontal displacement, and to address the problems of separation trajectory distortion caused by insufficient gravity acceleration of the scaling model of existing light model. The ejection velocity of the model is taken as a factor/vector, and is adjusted reasonably to compensate the linear displacement insufficiency caused by the insufficient vertical acceleration of the light model method, so as to ensure the matching of the vertical and horizontal displacement of the projectile, and to improve the consistency between the test results of high-speed projection and the actual separation trajectory. The optimized similarity law is applicable to many existing free-throwing modes of high-speed wind tunnels. The optimized similarity law is not affected by the ejection velocity and hanging mode of the projectile. The optimized similarity law is suitable not only for the launching of the buried ammunition compartment and external stores, but also for the test design of projectile launching and gravity separation.     

基于高速存储平台的高性能RS编译码器设计

目前,星载高速存储设备中采用商用RS编译码IP核来实现数据纠错功能,能够实现的编译码最高速率为800 Mbps,只能依靠多个IP核同时工作达到吉比特高速数据存取速率的要求。星载存储数据发生错误的主要原因是存储区单粒子翻转和存储介质本身特性产生的单比特数据错误。针对星载存储数据的误码特性,本文提出一种RS编译码改进算法,通过对编码算法中的剩余多项式及译码算法中的伴随多项式进行降次处理,减小编译码过程中运算的迭代次数及计算量,以及对编译码算法中的基本运算单元有限域乘法器采用子项复用技术,实现对传统RS编译码算法的改进。结果表明改进后的编译码器能达到最高数据速率为10.5 Gbps,编码器资源较单个商用IP核减少15%,译码器资源减少40%,能够满足后续高速存储平台的应用要求。     

基于多模型预测的再入飞行器制导方法

在具有控制和轨迹约束的再入制导中,提出了一种新的基于多模型预测再入飞行器纵向制导方法。首先对再入飞行器的纵向运动方程沿着标准轨道线性化,基于分段仿射约束系统建模理论逼近原非线性系统,并采用线性矩阵不等式(LMIs)优化技术离线将保证闭环系统稳定的终端二次代价项求出;然后,在每个制导周期内,基于多模型预测在线求解构造好的有限时域优化目标,从而获得控制量的增量,并把第一个控制增量分量与标准轨道的控制量叠加后形成全量控制,用于实际再入轨道的制导,而在下一个制导周期基于新的状态参数重复上面的优化过程。数字仿真结果证实了所提方法的有效性。     

基于温度信号的高速干铣削试验研究

本文应用红外测温系统对高速铣削过程中切削温度的动态变化进行在线监测.给出了铝合金高速铣削过程中不同磨损程度和不同材料的刀具加工时对应的切削温度以及切削温度随切削速度的变化规律,其结论有助于指导铝合金高速铣削加工、优化高速切削工艺.     

利用"火星快车"三程多普勒跟踪数据限定局部洛伦兹不变性

目前航天器的三程多普勒跟踪技术已经在深空探测的控制与导航领域起到了重要作用。利用包含了对局部洛伦兹不变性(LLI)以及局部位置不变性(LPI)原理有破坏的三程多普勒跟踪理论,研究分析了"火星快车"(MEX)三程多普勒跟踪数据的残差。这些多普勒观测于2009年8月7日和8日进行,利用了欧洲航天局(ESA)在澳大利亚新诺舍(New Norcia)的上行站和三个分别在中国上海、昆明以及乌鲁木齐的下行站。我们发现,这些观测结果给出的LLI上限在10-2的量级。但由于各观测站本身对频率测量的精度有限,这些数据并不适合于检验LPI。     

基于最优化问题的混合再入制导方法

在深入研究机动再入飞行器标准轨道和预测制导方法的基础上,针对标准轨道和预测制导相结合的制导方法,分析了由预测制导指令延迟引起的误差,提出了误差补偿策略.根据最优化理论,设计了相关性能指标函数,提出新的预测制导算法.并结合标准轨道法,通过对有限几个特征点位置上引入预测制导,形成了一种基于最优化问题的混合制导方法.有效减小了预测制导指令的解算时间,进一步降低了落点误差.仿真结果表明,该方法既具有较强的抗干扰能力和较高的制导精度,又具有一定的工程实用价值.     

高速摄像三维图像分析技术与应用

高速摄像是光学测量的重要手段。分析了高速摄像三维图像分析技术的处理过程,重点讨论了像机标定、自动目标检测与跟踪技术、多目标匹配技术和三维姿态测量技术等关键环节所面临的问题及解决方法,并以无人机回收测量系统为例说明了高速摄像三维图像分析技术在无人机位姿参数测量中的应用,对构建高速摄像测量系统提供了参考。