无速度测量下的航天器安全接近位姿一体化控制

针对考虑位姿耦合的非合作航天器交会对接场景,在没有速度测量情况下为了同时解决安全约束、模型不确定性、执行器故障和输入饱和问题,提出一种基于容积卡尔曼滤波算法(CKF)的自主安全接近方法。首先基于容积卡尔曼滤波器和扩张状态观测器(ESO)分别估计目标航天器的位姿信息和相对速度信息;然后通过将一种新颖的安全包络与人工势函数(APF)结合设计自适应滑模控制器,并设计非奇异辅助系统对执行器故障和输入饱和带来的影响进行集中处理。提出的控制策略在不违反安全约束情况下,能在固定时间内实现位置接近和姿态同步。通过李雅普诺夫方法可以保证闭环系统固定时间稳定。仿真结果表明,所提控制方法具有较高的精度和良好干扰抑制能力。     

Square-root quaternion cubature Kalman filtering for spacecraft attitude estimation

A novel quaternion estimator called square-root quaternion cubature Kalman filter is proposed for spacecraft attitude estimation. The filter approach uses a gyro-based model for quaternion propagation and a reduced quaternion measurement model to substantially reduce the computational costs. The process and measurement noises of the system model exhibit the same kind of linear state-dependence. The properties of the state-dependent noises are extended and more general expressions for the covariance matrices of such state-dependent noises are developed. The new filter estimates the quaternion directly in vector space and uses a two-step projection method to maintain the quaternion normalization constraint along the estimation process. The square-root forms enjoy a consistently improved numerical stability because all the resulting covariance matrices are guaranteed to stay positive semi-definite. Extensive Monte-Carlo simulations for several typical scenarios are performed, and simulation results indicate that the proposed filter provides lower attitude estimation errors with faster convergence rate than a multiplicative extended Kalman filter, a quaternion Kalman filter, and a generalized Rodrigues parameters (GRPs)-based cubature Kalman filter for large initialization errors.     

航天器近程编队自主协同相对导航方法

针对GNSS(全球导航卫星系统)拒止环境下近圆轨道多航天器近距离编队自主协同相对导航问题,提出了利用测角相机偏离航天器质心安装时的杆臂效应和多航天器之间几何一致性约束来实现相对导航的方法。首先,在第二轨道坐标下分别建立了基于Hill Clohessy Wiltshire方程的多航天器编队相对轨道演化模型、测角相机偏离质心安装情况下的相对视线角测量模型;然后,引入多航天器之间几何约束建立了相对轨道状态的一致性约束模型,并基于该约束模型设计了一致性扩展卡尔曼滤波估计算法;接着,对所建立的相对导航模型进行了相对轨道状态的可观测性分析,得到了使相对轨道可观测的相机偏置安装条件;最后,通过数值仿真实验对所提算法进行了校验,并与一致性无约束条件下的估计算法进行了对比分析。仿真结果表明,本文所提算法的相对位置误差能够快速收敛,在5 m传感器偏置和10 -3 rad量级测角误差条件下,多航天器相对定位误差在10 m以内。     

基于双目视觉的相对状态自主确定

基于双目视觉系统提出了一种适于交会对接最后阶段的近距离绕飞的相对状态自主确定方法。用修正罗德里格参数(MRP)描述姿态,给出了追踪器与目标器间的相对姿态运动学与动力学方程,以及相对运动方程,根据双目视觉系统的小孔成像原理建立了双目系统的测量数学模型,由扩展卡尔曼滤波(EKF)获得两航天器的相对位姿及其变化率。仿真结果表明该法可行。     

星间相对测量自主导航的改进容积卡尔曼滤波

针对仅利用星间相对位置测量的双星自主导航系统，提出一种基于可观度的改进容积卡尔曼滤波算法。该算法从系统可观度的物理意义出发，通过对预测协方差阵进行在线调整改善标准容积卡尔曼滤波算法对系统可观度敏感和不满足滤波拟一致性等问题。对具体算例进行数值仿真，校验了该改进容积卡尔曼滤波算法在基于星间相对位置测量的双星自主导航系统中的有效性，与标准容积卡尔曼滤波相比趋稳更快，精度更高。     

一种星间相对状态估计方法

编队自主导航是实现分布式遥感系统星间协同观测的基础。为实现分布式遥感系统星间相对状态的精确确定，提出一种基于MEMS激光雷达与纳型星罗盘的星间相对状态估计方法。借助相对姿态、轨道运动学方程建立了星间相对状态的无迹卡尔曼滤波(UKF)算法，解决了MEMS激光雷达测量与参考航天器姿态耦合的问题，并利用预定入轨参数及高精度轨道外推(HPOP)对方法进行仿真校验。结果表明，该方法具有可行性和实用性，估计精度满足分布式遥感任务需求，能够较好解决中远距离星间相对状态估计问题。     

万有引力场中带挠性太阳帆板航天器的姿态稳定性

本文讨论带双侧挠性太阳帆板航天器在万有引力场中的姿态运动，建立带挠性帆板航天器的欧拉方程和帆板强迫振动方程。利用Ｇａｌｅｒｋｉｎ方法对动力学方程离散化，利用Ｋｅｌｖｉｎ－Ｔａｉｔ－Ｃｈｅｔａｙｅｖ定量判断航天器在轨道坐标系内相对平衡的稳定性。导出适用于任意阶模态的解析形式稳定性充分条件。     

关于卫星姿态确定非线性滤波算法的研究

本文探讨了利用方位矢量和陀螺速率观测信息确定卫星姿态的问题。该问题实际上是一个非线性/非高斯状态滤波问题,因此,经典的基于EKF和UKF算法的姿态滤波器有可能失败,尤其是当初始状态的先验估计不可能精确得知的情况下。近来,粒子滤波理论已经开始应用于姿态确定问题,但是,这类算法往往需要大量的“粒子”,这对有限计算能力来说是一个沉重的负担。为此,本文尝试利用双重滤波方法,在每个序贯估计过程中,将有陀螺姿态确定问题暂时分解为1个四元数估计问题和1个陀螺常漂参数估计问题。本文提出了2个双重滤波器,包括1个姿态确定双重粒子滤波器和1个姿态确定的混合型滤波器。这两者都采用一个相同的四元数粒子滤波器,但在粒子重采样和平滑处理方面,不同于近来提出的类似滤波器。至于陀螺常漂估计,双重粒子滤波器发展了一个辅助粒子滤波器,而混合滤波器中则发展了一个参数UKF滤波器。通过与经典的姿态确定滤波器的仿真比较,证实了本文新提的2个算法的有效性和优越性。
     

Relative position and attitude estimation of spacecrafts based on dual quaternion for rendezvous and docking

The capacity to acquire the relative position and attitude information between the chaser and the target satellites in real time is one of the necessary prerequisites for the successful implementation of autonomous rendezvous and docking. This paper addresses a vision based relative position and attitude estimation algorithm for the final phase of spacecraft rendezvous and docking. By assuming that the images of feature points on the target satellite lie within the convex regions, the estimation of the relative position and attitude is converted into solving a convex optimization problem in which the dual quaternion method is employed to represent the rotational and translational transformation between the chaser body frame and the target body frame. Due to the point-to-region correspondence instead of the point-to-point correspondence is used, the proposed estimation algorithm shows good performance in robustness which is verified through computer simulations.     

GPS/速率陀螺组合Kalman滤波姿态确定算法研究

建立了GPS／速率陀螺组合姿态估计系统的模型，研究比较了三种典型的Kalman滤波姿态确定算法：状态扩充法、量测量求差法和时变噪声估计跟踪自适应滤波算法。给出了某航天器采用GPS／速率陀螺组合姿态确定的仿真计算结果，并对结果进行了分析。结果表明，与传统Kalman滤波算法比较，时变噪声跟踪自适应滤波算法和量测量求差滤波算法能较好地消除GPS测量中相关时变噪声的影响，提高姿态确定的精度；而且时变噪声跟踪自适应滤波算法能很好地消除由于噪声统计性能的不确定性对Kalman滤波的影响，提高姿态确定系统的性能。     

一种基于信息融合的深空巡航段自主导航算法

针对自主光学导航在深空巡航段应用中的问题,提出了一种基于信息融合的自主导航算法。由太阳敏感器测量获得太阳相对探测器的视线矢量,由分光计测量获得探测器相对太阳的径向速度,构建自主导航系统的两种信息观测方程;由基于状态估计误差协方差阵奇异值动态确定信息分配因子,用信息融合技术和扩展卡尔曼滤波算法实时估计探测器的位置与速度。对深度撞击任务的实际飞行数据的数值仿真结果表明:自主导航算法的轨道确定精度满足深空巡航段要求。     

带挠性附件卫星的模型化及截断

本文给出了具有中心刚体和P个挠性附件的空间飞行器姿态动力学方程式,并用约束和非约束两种模态展开,得到时域求解的状态方程式和频域中的增广姿态角对控制力矩的逆传递函数阵。推导中考虑了挠性附件对中心刚体的相对运动。本文还给出了两种模态恒等式,其中之一可用来做控制系统分析时截断高阶方程式的截断准则。     

Analytic expansions of luni-solar gravity perturbations along rotating axes for trajectory optimization—Part 2: The multipliers system and simulations

An efficient self-contained trajectory optimization software is generated by making use of de Pontécoulant's analytic lunar theory removing the need for an outside third body ephemeris program to compute the lunar and solar position vectors at each integration step. The accelerations being further resolved along the rotating Euler–Hill frame after expansion to third order in the spacecraft radial distance, the adjoint differential equations are derived in a direct manner complementing the generation of the dynamic system of equations for full compatibility. Because the variation of parameters equations are cast in terms of the nonsingular equinoctial elements with the perturbation accelerations resolved in their analytic form along the rotating axes, the adjoint equations are also derived in the same manner providing a highly efficient and accurate system of equations for rapid computations in conjunction with Aerospace Corporation's NLP2 nonlinear programming codes to search for the initial values of the multipliers that steer the spacecraft towards its target orbit in minimum time. Numerical simulations show that the solutions obtained by the analysis developed in this paper are essentially identical to the more indirect approach based on the use of inertial accelerations obtained from a separate ephemeris generator and subsequent conversions to the thrust frame and equinoctial system.     

高超声速飞行器发射坐标系导航算法

针对高超声速飞行器弹道特点和导航参数的需求，提出基于发射坐标系(LCEF)的高超声速飞行器导航算法。首先，介绍发射坐标系下捷联惯导(SINS)算法编排，推导发射坐标系下姿态、速度和位置离散递推方程。然后，介绍地心地固系(ECEF)下的卫星位置和速度转换到发射坐标系的方法，推导发射坐标系的SINS/BDS组合导航滤波器状态方程和量测方程。最后，以助推-滑翔飞行器为对象，进行了发射坐标系下组合导航仿真，位置精度小于10 m，速度精度小于0.2 m/s。     

对空间碎片的相对位姿估计

针对几何、质量特性参数均未知的空间碎片,提出一种基于扩展卡尔曼滤波（EKF）的相对位姿估计算法。该算法以单目相机获得的目标图像特征视线信息作为测量输入,以目标姿态、姿态角速度、惯量比、相对位置、相对速度和特征位置作为滤波状态。对算法进行可观性分析,给出两个可以保证算法可观性的条件。分别针对不同条件进行数值仿真,仿真结果表明新算法能够对几何和质量参数未知的空间碎片进行有效的相对位姿 估计。     

基于非线性滤波技术的多航天器编队飞行相对导航

航天器编队飞行协调工作,必须精确确定各航天器的相对位置和相对速度,即进行编队飞行相对导航,本文提出了一种UKF和卡尔曼滤波组合的非线性滤波算法,并将算法应用于编队飞行的载波相位差分GPS相对导航。     

利用GPS进行航天器姿态确定的EKF方法

姿态确定是ＧＰＳ在航天器上应用的一个重要方面。采用广义卡尔曼滤波（ＥＫＦ）方法利用ＧＰＳ进行航天器姿态确定，建立了ＧＰＳ载波相位观测和航天器姿态运动的线性误差方程，并进行了仿真计算。     

Impulsive control for angular momentum management of tumbling spacecraft

We discuss an angular momentum control of a tumbling spacecraft. The proposed control method is to apply an impulse by a space robot arm, to measure and control the relative position and attitude between the target spacecraft, and then to apply another impulse until the rotational motion of the target spacecraft is well damped. A discrete controller is designed using the simplified equations of rotational motion through appropriate coordinate transformation. The stationary response under contact model uncertainty is investigated and stability condition is analytically derived. Numerical simulations are given to validate the proposed approach.     

一种非合作目标相对位置和姿态确定方法

针对非合作目标中的从星若无法获得主星的动态信息时,就无法自主进行相对位置和姿态确定的问题,提出了一种采用陀螺、立体视觉系统和加速度计的相对状态确定方法。首先分别建立相对姿态方程、主星动力学方程和相对位置方程等系统的数学模型。然后根据这些方程组成的状态方程和立体视觉系统的测量模型设计了卡尔曼滤波器。该滤波器使得从星根据加速度计、陀螺和立体视觉系统的输出,在仅获得主星的外观特征和一些静态参数的情况下,能够自主进行相对位置和姿态的确定。最后,数值仿真结果表明,在相同仿真条件下,与使用主星陀螺信息的相对状态确定算法相比,该算法能够自主进行相对状态的确定,且位置和姿态稳态误差分别为0.05m和2°。     

Lorentz-force-perturbed orbits with application to J2-invariant formation

The Lorentz force acting on an electrostatically charged spacecraft in the Earth's magnetic field provides a new propellantless means for controlling a spacecraft's orbit. Assuming that the Lorentz force is much smaller than the gravitational force, the perturbation of a charged spacecraft's orbit by the Lorentz force in the Earth's magnetic field, which is simplified as a titled rotating dipole, is studied in this article. Our research starts with the derivation of the equations of motion in geocentric equatorial inertial Cartesian coordinates using Lagrange mechanics, and then derives the Gauss variational equations involving Lorentz-force perturbation using a set of nodal inertial coordinates as an intermediate step. Subsequently, the approximate averaged changes in classical orbital elements, including single-orbit-averaged and one-day-averaged changes, are obtained by employing orbital averaging. We have found that the approximate analytic one-day-averaged changes in semi-major axis, eccentricity, and inclination are nearly zero, and those in the other three angular orbital elements are affected by J₂ and Lorentz-force perturbations. This characteristic is applied to model bounded relative orbital motion in the presence of the Lorentz force, which is termed Lorentz-augmented J₂-invariant formation. The necessary condition for J₂-invariant formation is derived when the chief spacecraft's reference orbit is either circular or elliptical. It is shown that J₂-invariant formation is easier to implement if the deputy spacecraft is capable of establishing electric charge. All conclusions drawn from the approximate analytic solutions are verified by numerical simulation.