固定鸭舵二维修正弹比例导引律参数优化

针对固定鸭舵二维修正机构控制力有限和比例导引法控制末段需用过载变化过大的问题,提出了一种基于重力补偿比例导引律的过载阈值控制策略。分析了固定鸭舵二维修正机构的控制力及力矩,以落点弹目距离最小为目标函数,选取纵向和横向平面导引系数及过载阈值为设计变量,在重力补偿比例导引律的基础上建立了导引律参数优化模型,并采用差分进化算法（DE）对其进行优化。最后通过外弹道仿真分别从控制段飞行稳定性、控制效率、控制机构过载及控制精度几个方面与传统比例导引律进行对比分析,同时使用蒙特卡洛法验证了控制策略的有效性。结果表明：与传统比例导引律相比,使用该控制策略提高了二维弹道修正迫弹的控制效率,有效降低了控制末段需用过载,弹道控制段飞行稳定性明显提高。     

Usage of pre-flight data in short rendezvous mission of Soyuz-TMA spacecrafts

The paper describes the reduction of the vehicle autonomous flight duration before docking to the ISS. The Russian Soyuz-TMA spacecraft dock to the ISS two days after launch. Due to the limited volume inside Soyuz-TMA the reduction of time until docking to the ISS is very important, since the long stay of the cosmonauts in the limited volume adds to the strain of the space flight. In the previous papers of the authors it was shown that the existing capabilities of Soyuz-TMA, the ISS and the ground control loop make it possible to transfer to the five-orbit rendezvous profile. However, the analysis of the cosmonauts' schedule on the launch day shows that its duration is at the allowable limit and that is why it is necessary to find a way to further reduce the flight duration of Soyuz-TMA before docking to less than five orbits. In a traditional rendezvous profile, the calculation of rendezvous burns begins only after determination of the actual vehicle insertion orbit. The paper describes an approach in which the first two rendezvous burns are performed as soon as the spacecraft reaches the reference orbit and the values of the burns are calculated prior to the launch based on the pre-flight data for the nominal insertion. This approach decreases the duration of the rendezvous by one orbit. The demonstration flight of a Progress vehicle using the proposed profile was implemented on August 1, 2012 and completely confirmed the correctness of the imbedded principles. The paper considers the possible improvements of the proposed approach and recovery from the contingencies.     

亚轨道飞行器的固液火箭发动机的高维多目标设计优化

为完成应用在亚轨道飞行器上的固液火箭发动机系统设计优化,且考虑到系统设计优化问题的复杂性以及采用单目标优化难以获得全局最优解,建立了固液火箭发动机系统设计的4目标设计优化模型,采用非支配排序遗传算法获得超空间Pareto 解集。利用基于变偏好区间的超径向可视化技术对超空间Pareto解集进行直观地分析,提高最优解选择的效率。最终获得了全局最优的固液火箭发动机系统设计方案,验证了建立的优化模型的准确性和相比于单目标优化的优势,论证了固液火箭发动机应用在亚轨道飞行器上切实可行以及变偏好区间超径向可视化技术处理超空间Pareto解集的高效性。     

Life-sciences research opportunities in commercial suborbital space flight

Commercial suborbital space flights will reach altitudes above 100 km, with 3–5 min of weightlessness bracketed by high-g launch and landing phases. The proposed frequency of these flights, and the large passenger population, present interesting opportunities for researchers in the life sciences. The characteristics of suborbital flight are between those of parabolic and orbital flights, opening up new scientific possibilities and easing the burden for obtaining access to 0g.     

On Lambert’s problem and the elliptic time of flight equation: A simple semi-analytical inversion method

In the two-body model, time of flight between two positions can be expressed as a single-variable function and a variety of formulations exist. Lambert’s problem can be solved by inverting such a function. In this article, a method which inverts Lagrange’s flight time equation and supports the problematic 180°$180°$ transfer is proposed. This method relies on a Householder algorithm of variable order. However, unlike other iterative methods, it is semi-analytical in the sense that flight time functions are derived analytically to second order vs. first order finite differences. The author investigated the profile of Lagrange’s elliptic flight time equation and its derivatives with a special focus on their significance to the behaviour of the proposed method and the stated goal of guaranteed convergence. Possible numerical deficiencies were identified and dealt with. As a test, 28 scenarios of variable difficulty were designed to cover a wide variety of geometries. The context of this research being the orbit determination of artificial satellites and debris, the scenarios are representative of typical such objects in Low-Earth, Geostationary and Geostationary Transfer Orbits. An analysis of the computational impact of the quality of the initial guess vs. that of the order of the method was also done, providing clues for further research and optimisations (e.g. asteroids, long period comets, multi-revolution cases). The results indicate fast to very fast convergence in all test cases, they validate the numerical safeguards and also give a quantitative assessment of the importance of the initial guess.     

基于航迹分割的航空器噪声预测模型

根据航空器的航迹来预测其影响区域的噪声情况,基于航迹的几何特性,将航迹分成直线段航迹和曲线段航迹两个基本航迹元素;确定了直线段和曲线段的各自影响范围之后,分别计算各航迹段对它们影响区域的噪声值贡献情况;统计了各个航迹段对监测点的噪声影响之后,综合得出整个航迹段对监测点的噪声影响,从而建立了航空器航迹噪声预测的模型。将该模型计算的结果分别和软件模拟数据、实际监测数据进行对比分析,发现该模型在航迹段内对监测点噪声均值的预测较为准确,监测点噪声峰值预测结果更接近实测数据。     

Water movement on the convex surfaces of porous media under microgravity

A plant growth system for crop production under microgravity is part of a life supporting system designed for long-duration space missions. A plant growth in soil in space requires the understanding of water movement in soil void spaces under microgravity. Under 1G-force condition, on earth, water movement in porous media is driven by gradients of matric and gravitational potentials. Under microgravity condition, water movement in porous media is supposed to be driven only by a matric potential gradient, but it is still not well understood. We hypothesized that under microgravity water in void spaces of porous media hardly moved comparing in void spaces without obstacles because the concave surfaces of the porous media hindered water movement. The objective of this study was to investigate water movement on the convex surfaces of porous media under microgravity. We conducted parabolic flight experiments that provided 20–25?s of microgravity at the top of a parabolic flight. We observed water movement in void spaces in soil-like porous media made by glass beads and glass spheres (round-bottomed glass flasks) in the different conditions of water injection under microgravity. Without water injection, water did not move much in neither glass beads nor glass spheres. When water was injected during microgravity, water accumulated in contacts between the particles, and the water made thick fluid films on the particles surface. When the water injection was stopped under microgravity, water was held in the contacts between the particles. This study showed that water did not move upward in the void spaces with or without the water injection. In addition, our results suggested that the difficulty of water movement on the convex (i.e. particle surfaces) might result in slower water move in porous media under microgravity than at 1G-force.     

大飞行包线控制律的神经网络调参设计

对于具有大飞行包线的现代电传飞行控制系统,给出了一种3层BP(Back Propagation)神经网络代替传统的根据动压、高度或马赫数单一调参的控制律,解决了大飞行包线内控制参数复杂、单一调参无规律性、在全飞行包线上特别是在平衡点之间的飞行状态的稳定性无法保证等问题.通过离线训练,得出了一组隐层只有6个节点的网络结构参数,输出为各平衡点设计的最优鲁棒反馈增益.利用该网络实现了大飞行包线的根据高度和马赫数的双参数增益调参.仿真表明,利用该神经网络可以保证在所有平衡点上原设计的最优反馈增益不变,响应过程不变,同时可以细化平衡点之间的控制参数,在较大建模误差(约50％)和平衡点间也可以具有较好的控制效果.     

推力协同的大柔性飞行器纵向姿态控制

为了研究大柔性飞行器飞行/结构耦合动力学特性,提出了改进的面向控制的大柔性飞行器多体模型,开展了大柔性飞行器纵向动力学耦合特性分析与推力协同下纵向姿态控制律设计。采用二面角动态近似描述大柔性飞行器结构动力学特征,并推导了纵向耦合动力学模型。根据改进模型在配平点处的线性化模型,分析了飞行/结构耦合系统的纵向稳定性与结构变形量之间的关系。针对大柔性飞行器姿态稳定与跟踪,设计了纵向姿态控制器。与常规飞行器相比,大柔性飞行器飞行过程中会发生大变形,当载荷较大时,配平构型近似“U”形,此时纵向动力学具有长周期不稳定的特征。分析结果表明:大柔性飞行器各模态之间的耦合程度随着变形的增大而增大。此外,纵向姿态控制需要升降舵与推力协同控制速度和俯仰角并且考虑结构动力学的影响,否则飞行/结构的耦合作用会导致姿态跟踪误差衰减缓慢甚至发散。      

基于试飞数据的航空发动机状态监测与故障诊断

在航空发动机飞行试验阶段,发动机技术状态变化快、故障频发,为了实时监控发动机工作参数变化情况,快速及时地预测并诊断发动机故障,本文研究了试飞数据驱动的航空发动机状态监控与故障诊断技术。文章基于实际试飞数据建立了航空发动机ANN-NARX参数预测模型,考虑到建模样本量大、模型结构复杂、训练时间长、输入输出延迟等因素,采用遗传算法对模型的最小数据样本需求和结构进行了改进优化,并利用蒙特卡洛方法确立了参数预测模型的自适应告警门限,同时基于构建奇偶空间残差模型实现了航空发动机典型故障诊断。结果表明：实际试飞中只需有限架次试飞数据的训练学习,即可得到发动机参数预测模型,高压转子转速、压气机后压力、涡轮后总温及滑油总回油温度预测相对误差最大值分别为：1.0%、1.7%、0.2%和1.2%,综合模型建模误差和参数测量误差后的自适应告警门限有效降低了模型预测结果的不确定性,在已有数据样本集上的典型故障识别率达到95.2%。