Automatic orbital docking with tumbling target using sliding mode control

The present study aimed to propose translational and rotational control of a chaser spacecraft in the close vicinity docking phase with a target subjected to external disturbances. For this purpose, two sliding mode controls (SMC) are developed to coordinate the relative position and attitude of two spacecraft. The chaser is guided to the tumbling target by the relative position control, approaching in the direction of the target docking port. At the same moment, the relative attitude control coordinates the chaser attitude so that it can be aligned with the target orientation. These control systems regulate the relative translational and rotational velocities to be zero when two spacecraft are docking. The robustness of the closed-loop system in the presence of external disturbances, measurement noises and uncertainties is guaranteed by analyzing and calculating the control gains via the Lyapunov function. The simulations in different scenarios indicated the effectiveness of the controller scheme and precise maneuver regarding the accuracy of docking conditions.     

Robust fault-tolerant saturated control for spacecraft proximity operations with actuator saturation and faults

In this paper, the motion control problem of autonomous spacecraft rendezvous and docking with a tumbling target in the presence of unknown model parameters, external disturbances, actuator saturation and faults is investigated. Firstly, a nonlinear six degree-of-freedom dynamics model is established to describe the relative motion of the chaser spacecraft with respect to the tumbling target. Subsequently, a robust fault-tolerant saturated control strategy with no precise knowledge of model parameters and external disturbances is proposed by combining the sliding mode control technique with an adaptive methodology. Then, within the Lyapunov framework, it is proved that the designed robust fault-tolerant controller can guarantee the relative position and attitude errors converge into small regions containing the origin. Finally, numerical simulations are performed to demonstrate the effectiveness and robustness of the proposed control strategy.     

Optimal guidance and collision avoidance for docking with the rotating target spacecraft

The guidance and control strategy for spacecraft rendezvous and docking are of vital importance, especially for a chaser spacecraft docking with a rotating target spacecraft. Approach guidance for docking maneuver in planar is studied in this paper. Approach maneuver includes two processes: optimal energy approach and the following flying-around approach. Flying-around approach method is presented to maintain a fixed relative distance and attitude for chaser spacecraft docking with target spacecraft. Due to the disadvantage of energy consumption and initial velocity condition, optimal energy guidance is presented and can be used for providing an initial state of flying-around approach process. The analytical expression of optimal energy guidance is obtained based on the Pontryagin minimum principle which can be used in real time. A couple of solar panels on the target spacecraft are considered as obstacles during proximity maneuvers, so secure docking region is discussed. A two-phase optimal guidance method is adopted for collision avoidance with solar panels. Simulation demonstrates that the closed-loop optimal energy guidance satisfies the ending docking constraints, avoids collision with time-varying rotating target, and provides the initial velocity conditions of flying-around approach maneuver. Flying-around approach maneuver can maintain fixed relative position and attitude for docking.     

人控遥操作交会对接设计与验证

人控操作交会对接是指操作人员在远端通过遥操作方式控制追踪航天器进行交会对接,主要用于无人航天器自动交会对接系统故障条件下交会对接控制.简要介绍遥操作交会对接的基本概念,给出实现人控遥操作交会对接三种方案,设计一种易于工程实现的遥操作交会对接系统,分析关键技术并给出了解决方法;根据设计的系统方案,进行遥操作交会对接试验,试验结果表明设计方案合理可行.     

天舟二号货运飞船全相位自主快速交会对接技术和在轨验证

介绍天舟二号货运飞船全相位自主快速交会对接技术和在轨飞行结果.介绍21世纪以来交会对接发展的两个趋势：自主和快速；给出天舟二号货运飞船全相位自主快速交会对接方案，以及主要技术特点；给出天舟二号货运飞船5~8 h飞控实施方案和推迟一天发射的飞控实施方案，以及在轨执行效果.天舟二号货运飞船入轨自主快速交会对接是世界上首次进行的全自主快速交会对接任务，为我国空间站工程后续任务奠定了坚实的技术基础.     

航天器交会飞行设计方法研究

针对半自主飞行追踪星,阐述航天器交会总体设计方法。根据对接点的地理位置范围、共面轨道倾角以及目标星轨道周期与追踪星入轨点地理位置,确定交会飞行时间和两星初始相位差范围。考虑最小轨道机动动力要求与飞行轨迹安全性等因素,并兼顾地面测控条件,设计追踪星远程导引段与相对导航段的轨道机动与飞行轨迹,特别是选择与比较不同的初始轨道、调相轨道与漂移轨道以及保持点停泊时间与最终逼近段飞行时间等交会飞行要素,调整飞行时间、相位差与对接点位置,确定最佳交会飞行方案,完成空间交会任务。     

Motion-planning and pose-tracking based rendezvous and docking with a tumbling target

Rendezvous and docking (RVD) with a tumbling target is challenging. In this paper, a novel control scheme based on motion planning and pose (position and attitude) tracking is proposed to solve the pose control of a chaser docking with a tumbling target in the phase of close range rendezvous. Firstly, the current desired motion of the chaser is planned according to the motion of the target. In planning the desired motion, the “approach path constraint” is considered to avoid collisions between the chaser and the target, and the “field-of-view constraint” is considered to make sure the vision sensors on the chaser to obtain tight relative pose knowledge of the target with respect to the chaser. Then, the difference between the chaser’s motion and the desired motion is gradually reduced by a pose tracking controller. This controller is based on the non-singular terminal sliding mode (NTSM) method to make the tracking error converge to zero in finite time. Since the chaser nearly moves along the desired motion and the motion is reasonable, (1) it could safely arrive at the docking port of the target with a suitable relative attitude, (2) it will be always suitably oriented to observe the target well, and (3) the magnitude of the needed control inputs are less than that in existing literatures. The numerical results demonstrate the above three advantages of the proposed method.     

航天器近距离导引轨迹规划仿真系统设计

以航天器近距离导引轨迹规划仿真验证为目标,对基于Visual C+ +,Vega Prime和Matlab的联合仿真系统进行开发研究.首先,建立了数学模型.然后,利用Matlab对所建立的数学模型进行优化求解,得到追踪航天器近距离机动时的位置、速度等信息.并通过Multigen Creator软件建立卫星等对象的模型,使用Vega Prime进行视景仿真.之后,采用Visual C+ +进行系统集成,建立基于三者相结合的仿真验证系统.最后,以椭圆参考轨道下近距离交会的连续推力式燃料最优轨迹规划为例,验证了该联合仿真系统.     

对地观测卫星总体参数多学科优化

针对对地观测卫星总体参数设计问题,建立了以对地观测性能最佳为目标的多学科优化模型,考虑姿轨控制、电源、结构、推进、有效载荷5个分系统的设计变量和相应约束条件,并考虑运载火箭对卫星设计的约束条件,通过经验公式建立分析模型.采用协同优化方法,利用外点罚函数法将系统级优化问题转化为无约束优化问题以改善协同优化系统级的数值缺陷,建立了多学科设计优化框架.计算结果表明通过优化可提升卫星的对地观测性能,验证了该方法的合理性.建模思路与优化方法可望用于更贴合工程实际的卫星参数设计.      

Multivariate bootstrapped relative positioning of spacecraft using GPS L1/Galileo E1 signals

GNSS-based precise relative positioning between spacecraft normally requires dual frequency observations, whereas attitude determination of the spacecraft, mainly due to the stronger model given by the a priori knowledge of the length and geometry of the baselines, can be performed precisely using only single frequency observations. When the Galileo signals will come available, the number of observations at the L1 frequency will increase as we will have a GPS and Galileo multi-constellation. Moreover the L1 observations of the Galileo system and modernized GPS are more precise than legacy GPS and this, combined with the increased number of observations, will result in a stronger model for single frequency relative positioning. In this contribution we will develop an even stronger model by combining the attitude determination problem with relative positioning. The attitude determination problem will be solved by the recently developed Multivariate Constrained (MC-) LAMBDA method. We will do this for each spacecraft and use the outcome for an ambiguity constrained solution on the baseline between the spacecraft. In this way the solution for the unconstrained baseline is bootstrapped from the MC-LAMBDA solutions of each spacecraft in what is called: multivariate bootstrapped relative positioning. The developed approach will be compared in simulations with relative positioning using a single antenna at each spacecraft (standard LAMBDA) and a vectorial bootstrapping approach. In the simulations we will analyze single epoch, single frequency success rates as the most challenging application. The difference in performance for the approaches for single epoch solutions, is a good indication of the strength of the underlying models. As the multivariate bootstrapping approach has a stronger model by applying information on the geometry of the constrained baselines, for applications with large observation noise and limited number of observations this will result in a better performance compared to the vectorial bootstrapping approach. Compared with standard LAMBDA, it can reach a 59% higher success rate for ambiguity resolution. The higher success rate on the unconstrained baseline between the platforms comes without extra computational load as the constrained baseline(s) problem has to be solved for attitude determination and this information can be applied for relative positioning.