基于神经网络的多卫星姿态协同控制预测模型

摘要： 针对多卫星近距离对空间目标监测中的姿态协同控制问题，研究基于神经网络的智能控制模型.首先设计了面向任意姿态控制方法的神经网络自适应控制模型，该模型不改变卫星姿态控制方法本身，而是接收由理想控制模型生成的理想控制量，理想控制量经过神经网络后直接生成适用于卫星的控制量.根据神经网络对控制系统的系统级状态预测，基于一致性控制协议，设计了多卫星姿态协同控制模型.采用等效姿态角，通过数值仿真，分别验证了预测控制方法、输出状态预测、协同控制的方法正确性和有效性.     

Deorbiting spacecraft with passively stabilised attitude using a simplified quasi-rhombic-pyramid sail

This paper studies deorbiting using an analogue to the quasi-rhombic-pyramid concept for planar motion. The focus is on maintaining a stable (meaning oscillatory) attitude close to the direction of the velocity of the spacecraft relative to the atmosphere. The study consists of a massive computation of deorbit times chosen in a region of the phase space where atmospheric drag plays a leading role. Here, no damping effects are considered. Thus, any passive stabilisation observed is either due to solar radiation pressure or atmospheric drag. The results show that such stable deorbiting is feasible up to a threshold that depends upon the physical parameters of the sail. This threshold is around 500 km of altitude. Stable deorbiting is also shown to reduce the unpredictability that appears due to tumbling.     

Attitude stability and periodic attitudes of rigid spacecrafts on the stationary orbits around asteroid 216 Kleopatra

In this work, equilibrium attitude configurations, attitude stability and periodic attitude families are investigated for rigid spacecrafts moving on stationary orbits around asteroid 216 Kleopatra. The polyhedral approach is adopted to formulate the equations of rotational motion. In this dynamical model, six equilibrium attitude configurations with non-zero Euler angles are identified for a spacecraft moving on each stationary orbit. Then the linearized equations of attitude motion at equilibrium attitudes are derived. Based on the linear system, the necessary conditions of stability of equilibrium attitudes are provided, and stability domains on the spacecraft’s characteristic plane are obtained. It is found that the stability domains are distributed in the first and third quadrants of the characteristic plane and the stability domain in the third quadrant is separated into two regions by an unstable belt. Subsequently, we present the linear solution around a stable equilibrium attitude point, indicating that there are three types of elemental periodic attitudes. By means of numerical approaches, three fundamental families of periodic solutions are determined in the full attitude model.     

修正Rodrigues参数在飞行器定姿中的应用(英文)

There are two attitude estimation algorithms based on the different representations of attitude errors when modified Rodrigues parameters are applied to attitude estimation. The first is multiplicative error attitude estimator （MEAE）, whose attitude error is expressed by the modified Rodrigues parameters representing the rotation from the estimated to the true attitude. The second is subtractive error attitude estimator （SEAE）, whose attitude error is expressed by the arithmetic difference between the true and the estimated attitudes. It is proved that the two algorithms are equivalent in the case of small attitude errors. It is possible to describe rotation without encountering singularity by switching between the modified Rodrigues parameters and their shadow parameters. The attitude parameter switching does not bring disturbance to MEAE, but it does to SEAE. This article introduces a modification to eliminate the disturbance on SEAE, and simulation results demonstrate the efficacy of the presented algorithm.     

俯仰力矩曲线的“勺形”对飞机稳定性的影响

 本文用微分方程定性理论来分析俯仰力矩曲线随迎角变化的“勺形”对飞机飞行稳定性的影响。 结果表明,“勺形”是飞机在小侧滑角下作大迎角非机动飞行时,引起迎角突跃而进入过失速飞行的一种重要因素。“勺形区”的宽度和深度则较大程度地影响这种过失速飞行的特性及其进入与改出的特点。     

一种高可靠长寿命的推进系统

介绍单元肼为推进剂的卫星推进系统，该系统已成功用于我国地球同步轨道通信卫星，高可靠，长寿命。叙述了系统及各部件的主要性能，关键部件的特性与可靠性试验，材料相容性试验，微粒控制及系统热试车。根据多年的飞行试验及地验对系统进行了可靠性计算。     

俯仰轴飞行品质的PIO准则计算

由于新技术的采用,现代飞机出现驾驶员诱发振荡(PIO)现象大大增加,因此PIO已成为危及飞行安全的主要因素之一。介绍了MIL—STD—1797A规范中的PIO预测准则和美国“人机耦合对飞行安全影响委员会”提出的准则,论述了这些准则要求的背景、机理和计算方法,最后以某机为例进行了PIO预测计算和分析。     

翼型等速上仰绕流结构的观测

 翼型在不同转速下等速上仰时,其绕流结构不一样,转速越高,前缘涡开始形成的迎角越大。给定转速时,初始迎角大前缘涡形成得早。终止迎角对流动结构的影响与转速有关。平板翼型上仰时,前缘涡在较小迎角开始形成,涡的尺寸较大。     

俯仰敏捷性评估与影响因素研究

建立了现代高机动性能战斗机俯仰敏捷性仿真计算数学模型和机动飞行时的操纵动作，以Ｆ－１６战斗机为例，计算并讨论了初始飞行状态以及飞行控制系统参数对战斗机俯仰敏捷性的影响。结果表明，选择适当的飞行状态，有利于更好地发挥飞机的俯仰敏捷性；降低飞机整体系统的阻尼，将有利于提高飞机的俯仰敏捷性；控制系统有关参数的设计，除考虑飞行品质要求外，还需综合考虑飞机敏捷性等方面的要求。