Adaptive Quasi Fixed-Time Orbit Control Around Asteroid with Performance Guarantees

This paper investigates a novel quasi fixed-time orbit tracking control method for spacecraft around an asteroid in the presence of uncertain dynamics and unknown uncertainties.To quantitatively characterize the transient and steady-state responses of orbit tracking error system,a continuous performance function is devised via using a quartic polynomial.Then,integrating backstepping control technique and barrier Lyapunov function leads to a quasi fixed-time convergent orbit tracking controller without using any fractional state information and symbolic functions.Finally,two groups of illustrative examples are employed to test the effectiveness of the proposed orbit control method.

A Status Graph Based Control Allocation Algorithm of Digital Micro-Thruster Array for Micro/Nano-Satellites Orbit Control Application

Digital micro-thruster arrays can be used for special missions of micro/nano-satellites with the requirements of high precision and small impulse.This paper presents a novel control allocation algorithm for the digital micro-thruster array,namely status graph based control allocation(SGBCA)algorithm,which aims at finding the optimal micro thrusters combination scheme to realize the sequential control synthesis for micro/nano-satellite during real-time orbit control tasks.A mathematical model is set up for the control allocation of this multivariate over-actuated system.Through dividing thrusters into disjoint segments by offline calculation and combining segments dynamically online to provide a sequence of the required impulse for the micro/nano-satellite,the time complexity of the control allocation algorithm decreases significantly.All levels of impulse can be generated by the digital micro thruster arrays and the service life of the arrays can be extended using the segment converting strategy proposed in this paper.The simulation indicates that the algorithm can satisfy the requirements of real-time orbit control for micro/nano-satellites.

Chang’E-2 satellite asymmetric-descent orbit control technology

To accomplish high-resolution imaging of the preselected landing area, it was necessary for the Chang＇E-2 mission to perform orbital maneuvering on the far side of the moon to meet the conditional height requirement of the imaging area. Engine shutdown would be executed invisibly on the back side of the moon if the descent maneuver mode opposite to the target perilune or the fuel optimal maneuver mode was used. To ensure the satellite safety, the project collectivety required that the engine shutdown should be designed to be executed in the domestic segmental arcs and meet the requirement of satellite emergency treatment simultaneously. Accordingly, the asymmetric-descent orbit control technology was adopted by offsetting the ma- neuver point, which obtained the orbit control parameters of finite-thrust mode with an iteration algorithm and modified the results with target perilune drift estimation. The Chang＇E-2 satellite declined to the target of 100 km×l5 km orbit successfully on 26 October 2010, and has been flying for 32 circles in the experimental orbit to accomplish the preselected landing area imaging. This paper describes the mechanism and realization method of the asymmetric-descent orbit control technology and evaluates the maneuver effect with the actual mission data.

Controlof Orbitand Controlof Chaosina Class of Dynamic System

The problem of control of orbit for the dynamic system x ¨+x(1-x)(x-a)=0 is discussed. Any unbounded orbit of the dynamic system can be controlled to become a bounded periodic orbit by adding a periodic step excitation to the system. By using a nonlinear feedback control law presented in this paper the chaos of the dynamic system with excitation and damping is stabilized. This method is more effectual than the linear feedback control.

Multi-spacecraft Intelligent Orbit Phasing Control Considering Collision Avoidance

This paper proposes an intelligent low-thrust orbit phasing control method for multiple spacecraft by simultaneously considering fuel optimization and collision avoidance. Firstly,the minimum-fuel orbit phasing control database is generated by the indirect method associated with the homotopy technique. Then,a deep network representing the minimum-fuel solution is trained. To avoid collision for multiple spacecraft,an artificial potential function is introduced in the collision-avoidance controller. Finally,an intelligent orbit phasing control method by combining the minimum-fuel neural network controller and the collision-avoidance controller is proposed. Numerical results show that the proposed intelligent orbit phasing control is valid for the multi-satellite constellation initialization without collision.

Adaptive control for autonomous rendezvous of spacecraft on elliptical orbit

A strategy for spacecraft autonomous rendezvous on an elliptical orbit in situation of no orbit information is developed. Lawden equation is used to describe relative motion of two spacecraft. Then an adaptive gain factor is introduced, and an adaptive control law for auton- omous rendezvous on the elliptical orbit is designed using Lyapunov approach. The relative motion is proved to be ultimately bounded under this control law, and the final relative position error can achieve the expected magnitude. Simulation results indicate that the adaptive control law can realize autonomous rendezvous on the elliptical orbit with relative state information only.

Orbit and attitude control of spacecraft formation flying

Formation flying is a novel concept of distributing the functionality of large spacecraft among several smaller, less expensive, cooperative satellites. Some applications require that a controllable satellite keeps relative position and attitude to observe a specific surface of another satellite among the cluster. Specially, the target space vehicle is malfunctioning. The present paper focuses on the problem that how to control a chaser satellite to fly around an out-of-work target satellite closely in earth orbit and to track a specific surface. Relative attitude and first approximate relative orbital dynamics equations are presented. Control strategy is derived based on feedback linearization and Lyapunov theory of stability. Further, considering the uncertainty of inertia, an adaptive control method is developed to obtain the correct inertial ratio. The numerical simulation is given to verify the validity of proposed control scheme.

The present status and prospects in the research of orbital dynamics and control near small celestial bodies

Small celestial body exploration is of great significance to deep space activities. The dynamics and control of orbits around small celestial bodies is of top priority in the exploration research. It includes the modeling of dynamics environment and the orbital dynamics mechanism. This paper introduced state-ofthe-art researches, major challenges, and future trends in this field. Three topics are mainly discussed： the gravitational field modeling of irregular-shaped small celestial bodies, natural orbital dynamics and control, and controlled orbital dynamics. Finally, constructive suggestions are made for China’s future space exploration missions.

Shift control method for the local time at descendi ngnode based on sun-synchronous orbit satellite

This article analyzes the shift factors of the descending node local time for sun-synchronous satellites and proposes a shift control method to keep the local time shift within an allowance range. It is found that the satellite orbit design and the orbit injection deviation are the causes for the initial shift velocity, whereas the atmospheric drag and the sun gravitational perturbation produce the shift acceleration. To deal with these shift factors, a shift control method is put forward, through such methods as orbit variation design, orbit altitude, and inclination keeping control. The simulation experiment and practical application have proved the effectiveness of this control method.

双机械臂布局下的电推进位保策略

对于地球同步轨道的电推进卫星,可采用双机械臂式电推布局进行轨道维持控制.本文研究了双机械臂式电推布局的自主位保控制策略,针对南北各一台机械臂,每台机械臂分别配置一台电推力器的布局方式,通过每天1~2次点火,以尽量少的点火指向变动实现东西/南北联合位保控制.在双侧机械臂、电推力器正常情况下研究具有解析形式的在轨位保算法.研究基于单侧矢量调节机构和该侧电推力器的故障位保策略,给出衡量不同矢量机构能力和推力比冲下的位保效率衡量方法.仿真结果表明,正常/故障情况下的位保控制精度均能够满足同步轨道位保控制要求.本算法为解析形式,计算量较小,可以实现多星共轨和定点捕获/轨位漂移,便于量上自主实施.

东方红系列通信卫星控制技术发展综述

自1975年至今,我国已成功发展了以东方红系列为主的多型通信卫星平台,累计发射卫星70余颗,为我国国民经济和国防建设做出了重大贡献.概述我国东方红系列通信卫星平台的发展历程,梳理通信卫星控制系统发展脉络及主要特点,重点从姿态控制、轨道控制、信息体系架构和自主健康管理4个方面阐述了通信卫星控制技术主要进展.在此基础上,结合空间任务需求,对通信卫星控制技术的未来发展方向进行分析和展望,助推未来创新发展.

200 N推力装置上肼类分解催化剂的应用性能

研究制备了一种单组元姿轨控发动机用肼类分解催化剂,采用200 N推力装置对其应用性能进行了研究和考察。在催化剂物化性能指标满足应用要求的基础上,利用200 N推力装置通过力学环境试验考察了催化剂力学环境适应性,通过双-10℃低温冷启动、低温稳态及脉冲、正负拉偏以及脉冲寿命热试考核程序考察了自制催化剂的低温冷启动性能、低温稳态性能、常温正负拉偏稳态性能以及脉冲寿命性能。结果表明:该催化剂肼催化分解效率在99%以上,机械强度高且力学环境适应性良好,具有较高的肼催化分解活性和稳定性,能够在200 N推力装置上于双-10℃正常启动,顺利完成了低温稳态、常温正负拉偏和脉冲寿命等考核程序,发动机室压平稳,响应特性良好,脉冲一致性好,可满足推力装置的使用要求。

新型绿色单组元液体推进剂发展现状与趋势

随着对生态环境、安全的日益关注以及航天推进技术的不断发展,对推进剂提出了绿色无毒的性能要求,新型绿色单组元液体推进系统成为航天推进的重要研究方向之一。硝酸羟铵基单组元液体推进剂(HAN基单组元推进剂)和二硝酰胺铵基单组元液体推进剂(ADN基单组元推进剂)具有绿色无污染、密度大、比冲性能可调节、饱和蒸汽压低和使用维护成本低等特点,可以应用于卫星、飞船、运载火箭等飞行器的姿轨控动力系统,二者均已完成多次飞行演示验证并获得应用,受到了各国航天领域的广泛关注。

基于功能链的北斗三号卫星控制技术

为适应卫星研制技术和规模空前发展,在卫星高可靠的同时做到低成本,将传统的分系统设计方法按特点和学科进行了重新梳理,提出国内首创的功能链设计理念和方法,并成功应用于北斗三号首发试验星、组网星及备份星中,实现了北斗三号卫星的快速批产组网.阐述基于功能链的设计理念,重点介绍基于功能链的北斗三号卫星姿态及轨道等控制技术,在轨运行结果表明,卫星实现了连续可靠的工作,全面适应ka及激光星间链路的高控制精度要求以及导航卫星对高连续性的要求.

基于弗洛凯特理论的Halo轨道辐轮构型编队控制设计

面向未来使用平动点航天器编队进行深空探测的需求,研究了特殊的定向辐轮构型航天器编队在日地L2平动点Halo轨道上的动力学和相关控制问题。首先,建立了圆型限制性三体问题(CRTBP)的相对动力学和辐轮构型编队模型的数学表达;其次,基于Floquet理论和傅里叶级数展开推导了Halo轨道的相对运动解析解,该解的推导同样可应用于其他小偏离的周期时变系统;接着,以深空探测任务为导向,基于Floquet模态法和LQR控制法分别给出编队主星和从星的分层控制策略;最后,对控制策略进行仿真,详细分析了辐轮构型维持控制力的规律等,得到了构型参数(半径和频率)与维持代价的关系。

太阳成像仪镜筒舱内压力控制技术研究

文章阐述了太阳成像仪镜筒舱内压力控制技术研究,主要包括限流小孔机械尺寸理论分析、慢速泄压阀设计、镜筒压力控制模拟测试等内容。目前,所研制的慢速泄压阀已顺利交付使用,并随46.5 nm极紫外太阳成像仪在中科院空间新技术试验卫星上进行了搭载,实现了在轨顺利开机,验证了太阳成像仪镜筒舱内压力控制手段的正确性。

嫦娥六号环月飞行双环容错姿态控制

嫦娥六号着陆器和上升器组合体(着上组合体)环月飞行阶段,利用安装于上升器的10 N发动机(可形成力偶控制方式)和安装于着陆器的150 N发动机进行姿态控制。根据发动机安装布局,当力偶控制方式下某10 N发动机常关故障、其配对使用的10 N发动机正常工作时,推进系统将产生与期望相反的控制力矩,导致姿态发散。为了保证在10 N发动机故障情况下着上组合体姿态稳定,给出了双环容错姿态控制策略,包括10 N发动机内环控制和150 N发动机外环控制。数学仿真结果表明,着上组合体环月飞行阶段双环容错姿态控制下,10 N发动机故障后,着上组合体姿态可以稳定在给定范围内。针对配置力偶姿控发动机和冗余发动机的探测器,采用双环容错姿态控制策略,可以有效应对力偶姿控发动机故障影响,保证探测器姿态稳定。

欠驱动航天器模糊自适应增强耦合姿态控制

在快速轨道机动期间,针对固体推进作用下推力偏心、安装误差等因素带来的姿态强干扰问题,提出了一种基于推力矢量控制技术的航天器姿态欠驱动智能控制方法。首先,建立了航天器姿态误差动力学模型,并分析推力矢量控制输入的欠驱动特性。然后,考虑强干扰不确定性和滚转通道耦合弱的问题,设计了基于增强耦合策略与自适应模糊观测器的欠驱动智能控制律,结合模糊逻辑函数逼近强干扰不确定项并引入控制律中,实现航天器的姿态欠驱动智能控制,通过Lyapunov理论证明了系统的稳定性。最后,通过与分层滑模控制方法进行对比仿真,验证了所设计的方法能够使得三轴姿态稳定时间缩短14%,滚转通道耦合弱产生的静差被有效消除,为快速轨道机动期间的强干扰抑制技术提供基础。

全电推卫星用可分离推进舱设计及应用

亚太6E卫星是我国第一颗全电推卫星,卫星采用低成本火箭发射,星箭分离轨道为近地轨道.针对全电推卫星电推轨控推力小和入轨时间长的特点,卫星设计采用可分离推进舱进行快速轨道提升的方案,完成任务后可抛离.由于在轨工作时间短,可分离推进舱采用低成本设计,轨道控制方面,设计采用可分离推进舱进行轨道控制以及与卫星分离后自主离轨方法.可分离推进舱轨控任务完成后与卫星分离,减少了卫星的质量,进而减少后续电推变轨时间,降低电推进剂氙气的消耗,对提升卫星承载能力以及提高卫星寿命有较大优势.

对地观测卫星编队协同容错姿轨耦合控制

面向对地观测场景下卫星编队的姿轨耦合特性和完全失效故障,提出了基于空间构型重构的协同容错控制方法。首先,根据对地观测的任务需求,分别建立了无故障情况下的卫星编队构型,以及故障发生后将故障卫星移出编队的构型重构方案,包括拓扑网络重构、卫星编号更新和编队构型重构算法;其次,根据上述构型,考虑外部干扰和姿态轨道耦合特性,设计了基于非奇异终端滑模控制的分布式控制律,使得编队在有限时间内稳定,即在故障发生前后卫星编队都可以实现对观测区域的协同覆盖;最后,分别通过数值仿真和实验验证表明了所提方法的有效性。