航天器交会最终逼近段相对姿态估计与控制

对航天器交会对接最终逼近段,给出姿态运动学方程统一形式以及相对姿态动力学方程;除了应用交会航天器的绝对姿态运动方程进行相对姿态估计(间接法)外,还直接应用相对姿态运动方程进行相对姿态估计(直接法);阐述相对姿态控制的相平面法与四元数反馈法的设计方法.相平面控制法应用常值推力,针对小姿态角机动的特点,将相对姿态通道解耦为3个独立的二阶子系统,设计相平面推力方向切换函数;四元数反馈法应用简化的基于本征轴旋转的线性二阶系统,选择相对四元数与角速率反馈增益系数,确定控制力矩.此外,对相对姿态估计与控制方法进行模拟计算与比较.理论分析与模拟计算结果表明:应用扩展Kalman滤波的相对姿态间接估计法与直接估计法是有效的,后者有可能简化估计算法;相平面控制法与四元数反馈法均可有效实现相对姿态控制,前者应用常值推力(推力方向与姿态反馈有关),较易实现,但动力消耗较大,后者按控制力矩随姿态反馈量而变,动力消耗较小.      

交会对接气浮仿真平台视觉辅助姿态确定

文章首先介绍了用于空间合作卫星最后逼近段交会对接任务的仿真平台,描述了文中使用的姿态运动学方程和视觉成像算法。为了充分利用陀螺仪和视觉系统进行姿态确定,采用传统的扩展卡尔曼滤波（EKF）对两种测量数据进行融合,实现对姿态和陀螺仪漂移的估计。为了克服EKF调节参数过多和计算过程需要求逆的问题,设计了一种新的非线性观测器。最后,通过在对接仿真平台上进行试验,对比验证了非线性滤波器的有效性以及实用性。     

基于X射线脉冲星的航天器自主导航数值分析研究

基于X射线脉冲星的天文自主导航方法稳定、可靠、精度高,是航天器自主导航领域重要的发展方向.论文介绍了基于X射线脉冲星导航的基本原理,给出了脉冲星自主定位的滤波模型;基于扩展卡尔曼滤波导航算法,以地球同步轨道为例,分析了不同初始误差、轨道倾角、轨道偏心率以及不同脉冲星方位误差下的导航精度.仿真算例表明,在脉冲星方位误差为0.001″、脉冲到达时间测量误差为0.1μs的情况下,导航定位精度优于1km,且对初始误差不敏感;脉冲星方位精度、脉冲计时精度、轨道面位置和轨道偏心率是影响导航精度的主要因素.     

基于X射线脉冲星的航天器自主导航数值分析研究木

基于X射线脉冲星的天文自主导航方法稳定、可靠、精度高.是航天器自主导航领域重要的发展方向.论文介绍了基于X射线脉冲星导航的基本原理,给出了脉冲星自主定位的滤波模型;基于扩展卡尔曼滤波导航算法,以地球同步轨道为例,分析了不同初始误差、轨道倾角、轨道偏心率以及不同脉冲星方位误差下的导航精度.仿真算例表明,在脉冲星方位误差为0.001"、脉冲到达时间测量误差为0.1μs的情况下,导航定位精度优于1 km,且对初始误差不敏感;脉冲星方位精度、脉冲计时精度、轨道面位置和轨道偏心率是影响导航精度的主要因素.     

一种重力卫星质心在轨标定算法

针对重力卫星质心在轨标定问题,提出了一种将预测滤波与卡尔曼滤波相结合的标定算法。该算法首先利用磁力矩器产生一个明显大于干扰力矩的周期性力矩作用于卫星上,然后利用陀螺数据实现了卫星角加速度的预测滤波估计,并通过静电加速度计信息设计卡尔曼滤波器,实现卫星质心的标定;最后进行了数学仿真,仿真结果表明该算法针对卫星的角加速度及质心位置能够实时估计,三轴最佳标定精度分别为[0.0628 0.0324 0.0414]mm,实现了卫星质心较为精确的标定。     

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.     

Two-dimensional phase plane structure and the stability of the orbital motion for space debris in the geosynchronous ring

Based on the orbital resonance model, we study the two-dimensional phase plane structure of the motion of space debris orbiting the geosynchronous ring under the combined effects of the tesseral harmonics J₂₂, J₃₁ and J₃₃ of the Earth’s gravitational field. We present the main characteristic parameters of the two-dimensional phase plane structure. We also analyze the stability of the two-dimensional phase plane structure with numerical method. Our main findings indicate that the combined effects of the tesseral harmonics J₂₂, J₃₁ and J₃₃ fully determine the two-dimensional phase plane structure of the space debris, and it remains robust under the effect of the Earth’s actual gravitational field, the luni-solar perturbations and the solar radiation pressure with the normal area-to-mass ratios.     

振幅相位误差对雷达性能的影响

从工程应用角度出发,分析了振幅误差和相位误差对雷达性能的影响。为了简化起见,只考虑地杂波和单频干扰,且不考虑接收机的热噪声,文中讨论了单脉冲测角精度,时间域中滤波器抑制杂波的能力和空间域中滤波器抑制有源干扰的能力等6个有关雷达设计中的具体问题,结论简明,并给出了曲线提供参考。     

Influence of processing and external storage conditions on the performance of envelope materials for stratospheric airships

Envelope materials are extremely vital for stratospheric airships, which are widely used in numerous applications. The influence of processing as well as the storage and utilization conditions on the performance of envelope materials has been studied systematically for the first time. Results show that the performance of envelope materials depends largely on the hot-pressing temperature and the flexing during processing. The tensile strength of samples dropped to 289.1 ± 8.0 MPa from 346.6 ± 9.3 MPa when pressed at temperature above 180 °C and helium leakage appeared. The outer layers would be worn off when flexed no matter by manual or machine, resulting in dramatic increase of helium permeability and even leakage as well as varying decrease of mechanical properties. Hence, suitable hot-pressing temperature and limitation of flexing as little as possible during processing are essential to obtain products with suitable properties. Besides, the storage and utilization conditions are also critical to the properties of envelope materials. Both naturally aged samples in outdoor storage on ground and samples recovered from actual flight on stratospheric airship exhibited reduced mechanical properties and even helium leakage due to excess solar irradiation, ozone concentration and energetic particles interaction compared with those stored indoors. The weatherability of envelope materials should be further strengthened in the next few years. This research could provide a theoretical guidance for actual practice.     

Thermal properties of molten InSb,GaSb, and InxGa1−xSb alloy semiconductor materials in preparation for crystal growth experiments on the international space station

The thermal properties of InSb, GaSb and In_xGa_1−xSb, such as the viscosity, wetting property, and evaporation rate, were investigated in preparation for the crystal growth experiment on the International Space Station (ISS). The viscosity of InGaSb, which is an essential property for numerical modeling of crystal growth, was evaluated. In addition, the wetting properties between molten In_xGa_1−xSb and quartz, BN, graphite, and C-103 materials were investigated. The evaporation rate of molten In_xGa_1−xSb was measured to determine the affinity of different sample configurations. From the measurements, it was found that the viscosity of In_xGa_1−xSb was between that of InSb and GaSb. The degree of wetting reaction between molten In_xGa_1−xSb and the C-103 substrate was very high, whereas that between molten In_xGa_1−xSb and quartz, BN, and graphite substrates was very low. The results suggest that BN and graphite can be used as materials to cover InSb and GaSb samples inside a quartz ampoule during the microgravity experiments. In addition, the difference of the evaporation rate of molten In_xGa_1−xSb, GaSb, and InSb was small at low, and large at high temperature.