有限推力下相对绕飞轨道的直接形成

提出了一种有限推力下主动航天器在完成轨道转移的同时形成相对目标航天器绕飞的方法。根据以改进春分点轨道根数表示的非奇异轨道摄动方程,用变分方法将问题转化为经典的最优控制,由相对运动动力学获得主动航天器实现绕飞须满足的终端约束条件,再用非线性规划求解。给出了求解模型。理论分析和仿真结果表明,该方法理论上可行,但为减少干扰产生的偏差,还需对绕飞形成过程中的导引率进行研究。     

基于T-H方程的卫星轨迹模型参考输出跟踪控制方法

当目标卫星沿椭圆轨道运行时,描述追踪星与目标星相对运动的线性化方程为T-H方程。将描述航天器相对运动的T-H方程变换为周期系统的状态空间形式,并给出卫星轨迹跟踪控制问题的数学描述。基于周期系统的参量Lyapunov方法和模型参考跟踪控制理论,提出了卫星轨迹跟踪控制器的设计方法。利用该方法设计了带有收敛速率保障的反馈镇定控制器和具有自由参数的前馈控制器。对追踪星相对目标星悬停任务进行了数值仿真,仿真结果表明提出的控制方案是有效的。     

对无控旋转目标逼近的自适应滑模控制

对追踪器逼近无控旋转目标器的轨迹和姿态六自由度控制问题进行了研究.基于适用于任意偏心率的航天器相对运动轨道和姿态动力学模型,对追踪器逼近无控旋转目标的参考轨迹和参考姿态进行了分析与设计,推导了一种用于六自由度逼近控制的自适应滑模控制器.通过仿真分析,证明了所设计的逼近参考轨迹和参考姿态的合理性,同时验证了自适应滑模控制器的有效性.     

追踪星跟踪空间非合作目标的相对轨道设计

对空间非合作目标跟踪飞行可以执行观测或监视等任务。首先从一般性出发对追踪星与非合作目标之间的椭圆轨道相对运动方程进行分析,给出具有任意初始条件的相对运动方程解析表达式。其次,对追踪星沿航向跟踪目标并考虑约束条件时的相对轨道设计进行分析后,给出设计追踪星轨道的方法,该方法使得追踪星在保持对地定向的同时也满足测量敏感器的约束条件。最后通过数学仿真进行了验证。     

空间非合作目标燃料最优终端接近策略研究

针对一类姿轨控制系统失效的目标航天器实施空间救援等在轨服务任务。要求追踪航 天器跟踪到达指定目标点,对目标航天器进行在轨捕获,建立了目标航天器在空间自由翻滚 情况下追踪航天器跟踪目标点的动力学模型,并建立了安全无碰撞的燃料最优终端接近模型 。数学仿真表明,当初始条件合适时,燃料最优终端接近轨迹自然满足安全性要求。
     

月球探测器直接软着陆最优轨道设计

研究月球探测器直接软着陆最优轨道的设计问题。首先根据探测器直接软着陆的特点，提出了有限推力最省燃料的最优轨道设计问题；然后利用有限推力月面软着陆的最优推力控制方向的计算公式，研究了边值条件和计算方法；最后通过直接软着陆最优轨道的算例及结果分析，发现开始制动高度越低越省能量；推力方向可变时比不可变时节省能量；推力大小可变相当于采用了多级制动，对安全定点着陆非常有利。     

近距离航天器相对轨道的鲁棒自适应控制

针对近距离航天器的相对轨道提出了一种鲁棒自适应控制律。在追踪星本体坐标系中考虑航天器的相对运动。首先,在转动惯量未知的情形下提出了自适应控制律,保证系统的全局渐近稳定性。其次,将两星地心引力加速度之差作为干扰加速度,并假设干扰有未知上界,对自适应控制律进行修正,提出了鲁棒自适应律,使得系统是全局一致最终有界稳定的。控制律的设计不需要绝对轨道信息,适用于任意轨道。对航天器编队飞行和空间交会两种情形分别进行了仿真分析,结果表明所设计的控制律是合理有效的。     

固体微推力器阵列的推力估计与分配补偿方法

针对固体微推力器阵列(SPMA)中微推力器一次性点火，推力测试中难以获得精确推力的特点，为实现推力在线估计和实时补偿，提出一种利用二次规划对微推力器阵列推力进行估计，同时结合混合整数规划算法进行推力分配的方法，对估计算法收敛性以及控制系统稳定性进行了分析。该方法在不修改控制律的前提下，对推力器推力进行在线估计，并采用推力分配的方法实时补偿推力器出现的推力偏差，对系统稳定性的分析证明该方法可以保证系统的有界稳定。将其应用到微纳卫星编队保持中，仿真结果表明，在微推力器阵列出现推力偏差的情况下，该方法能很好地补偿推力偏差对控制系统造成的影响。     

Automatic rendez-vous scheme proposed for an unmanned (or manned) vehicle with a space station

A method for automatic rendez-vous between an active vehicle, and a passive orbiting vehicle (typically a space station on a circular orbit) is presented. The main interest of the method is the simplicity of system implementation, and the small requirements on vehicle maneuvres and on-board computations, rather than in the mathematical optimization of fuel expenditure or elapsed time.The chaser is at first put on a circular orbit, lower and nearly coplanar to the orbit of the target (space station). An open-loop transfer of the chaser is performed, in order to put it in a window appropriated for automatic rendez-vous. When the relative distance of the two vehicles is small enough, a radar is used on the chaser for continuous determination of relative position and speed. An on-board computer is used then to derive the moments of application of corrective thrusts and their orientation. The scheme leads to a series of corrections nearly equally spaced in time, and the chaser approaches the target exponentially. Out of plane errors are also corrected. When the vehicles are close, the docking phase is initiated, which can be performed either automatically or manually. Even in manual control, an automatic loop is used in order to give the pilot simple motions in response to the control.     

考虑地球非球形摄动的固体动能拦截器助推段最优控制方案研究

针对三维空间内的高速飞行目标,提出了一种可用于固体动能拦截器助推段的精确最优控制方法。考虑了地球非球形摄动的影响,建立了有限推力拦截器最优控制问题动力学模型,并用直接配置法与SQP方法进行了数值求解,得到了更加精确的助推段控制方案。算例证明该方法有效。     

On solving the problems of optimization of trajectories of many-revolution orbit transfers of spacecraft

The problem of optimal control over many-revolution spacecraft orbit transfers between circular coplanar orbits of satellites is considered. The spacecraft flight is controlled by a thrust vector of a jet engine with restricted thrust (JERT). The mass expenditure is minimized at a limited time of flight. The optimal control problem is solved based on the maximum principle. The boundary value problem of the maximum principle is solved numerically using the shooting method. A modified computation scheme of the shooting method is suggested (multi-point shooting), as well as a method (correlated with the scheme) of choosing the initial approximation with the use of a solution to the optimization problem in the impulse formulation. The scheme and method allow one to construct many-revolution spacecraft orbit transfers.     

有限推力交会的最省燃料轨迹

给出了航天器有限推力交会的最省燃料轨迹。首先应用三角变换技术将推力约束 转化为没有任何约束的虚拟控制,进而利用直接优化方法,应用参数化控制方法以及强化技 术将控制向量表示为分段常值函数,将上述最优控制问题转化为非线性规划问题。应用经典 的参数优化方法即可求得最优控制律的一个近似解,通过增加参数个数,重复优化得到逼近 连续最优解的参数化解。仿真结果表明提出的控制方案是行之有效的。
     

空间停靠动力学和控制

本文研究空间停靠是广义的，它包括停留和靠近两个内容。本文首先研究空间靠近动力学方程；其次讨论保持点的动力学特性和保持点轨迹稳定的必要条件；最后介绍靠近段安全可靠的控制策略，其中包括主动稳定保持点轨迹的控制方案。     

非合作目标交会相对导航方法研究

本文对一类非合作目标交会的相对导航问题进行了研究。基于近圆轨道上运行的非合作目标航天器初始轨道、追踪航天器在惯性空间的瞬时位置及追踪航天器到目标航天器的视线仰角和方位角等信息,文章从相对距离和相对姿态的确定及相对导航滤波器的设计三方面入手,提出了相对位置和相对速度等相对导航参数的获取方法。数学仿真验证了该方法的有效性。     

Method of continuation for optimization of interplanetary low-thrust trajectories

The problem of local optimization of interplanetary low-thrust trajectories is considered with the use of the maximum principle and continuation numerical methods. Two types of problems are analyzed: problems with limited power and problems with limited thrust. The latter problem is generalized by introducing the dependence of thrust and specific impulse on available electric power. In order to reduce the problem of optimal control to a boundary value problem, the Pontryagin maximum principle is used, and then, using the continuation method, this boundary value problem is reduced to the Cauchy problem. Variants of the continuation method for optimizing low-thrust trajectories are presented in the paper, including a new method of continuation for the limited thrust problem, which does not require any choice of the initial approximation for boundary values of conjugate variables.     

火箭垂直回收多阶段最优轨迹规划方法

针对火箭高空再入定点回收，基于凸优化方法提出一种考虑气动力和推力控制的多阶段轨迹优化方法。在气动减速段，通过控制总攻角，实现气动升力和阻力的调制。由于气动力连续变化，使用Legendre-Gauss-Radau伪谱离散方法进行离散化，利用较少的离散点实现较高的数值精度。在动力减速段，推力矢量为控制变量。由于推力调节可能出现不连续，采用等距离散方法进行离散。在此基础上，将发动机开、关机时间也作为优化变量，并考虑各种约束，构建了多阶段离散最优控制模型。使用无损凸化方法对升力约束和推力约束进行松弛，并通过逐次凸化消除由气动力、自由时间变量以及质量引入的非凸约束，最终将问题描述为序列迭代求解的二阶锥规划问题(SOCP)。通过仿真校验，经过少量的逐次凸化迭代，可快速收敛到最优解，且落点调节范围更大，燃料更省。     

基于在线轨迹优化的运载火箭可重构制导方法（英文）

In order to improve the safety and reliability of a launch vehicle, we present a reconfigurable guidance method based on online trajectory optimization for thrust decrease at the ascending stage of the launch vehicle in this paper. We used a multiple shooting method to convert the optimal control problem into a nonlinear programming(NLP) problem. Finally, we used the interior point method to solve the NLP problem. The simulation results show that the method can effectively adapt to thrust decreases by 5% and 10%. This reconfigurable guidance method based on online planning is proposed to realize launch missions under the condition of power descent, thus verifying the feasibility of the method.     

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.     

Optimization of transfer trajectories to the Apophis asteroid for spacecraft with high and low thrust

The problem of optimization of a spacecraft transfer to the Apophis asteroid is investigated. The scheme of transfer under analysis includes a geocentric stage of boosting the spacecraft with high thrust, a heliocentric stage of control by a low thrust engine, and a stage of deceleration with injection to an orbit of the asteroid’s satellite. In doing this, the problem of optimal control is solved for cases of ideal and piecewise-constant low thrust, and the optimal magnitude and direction of spacecraft’s hyperbolic velocity “at infinity” during departure from the Earth are determined. The spacecraft trajectories are found based on a specially developed comprehensive method of optimization. This method combines the method of dynamic programming at the first stage of analysis and the Pontryagin maximum principle at the concluding stage, together with the parameter continuation method. The estimates are obtained for the spacecraft’s final mass and for the payload mass that can be delivered to the asteroid using the Soyuz-Fregat carrier launcher.