多导弹三维编队控制

 多导弹编队控制可极大提高多枚导弹协同作战的效能。重点研究了多导弹编队控制涉及的2个主要问题：编队结构问题和三维编队保持控制器设计问题。提出了改进的领弹-跟随弹编队模式,结合多级分布式控制策略,解决了领弹失效时队形无法保持的问题;设计了基于相对误差的三维非线性跟随弹编队控制器,得到相应的跟踪控制律。不管领弹如何机动,跟随弹与领弹的相对距离始终为指定的期望值,同时跟随弹的速度、航向角和滚转角也能与领弹保持一致,通过仿真验证了所设计的编队控制器具有鲁棒性和稳定性。     

Results About Ocean Satellite Observation

They have played more and more important roles in marine pollution monitoring, marine environment and marine disaster monitor and forecasting, marine resource investigation and marine scientific research. In this paper, the author will give a brief review of China's operational and scientific activities in satellites ocean observation during 2008 to 2010. These activities include the application of the HY-1B for red tide and green tide detecting and monitoring, sea ice monitoring, fishery resources assessment at coastal zone and ocean, marine water quality assessment, sea surface temperature monitoring and forecasting, ocean primary productivity and carbon cycle research, and the development in the ocean dynamic environment parameter application technology before launch of HY-2. The achievements we have made in the ocean observation and monitoring during the past 3 years indicate that, the development of the ocean satellite series and the application of the ocean satellite can greatly promote the development of China's three-dimensional marine observation system and earth-observation system from space, accordingly we can improve the ability of acquiring the marine environmental parameter to sustain the marine economy development and the sea defense construction.      

空间失效慢旋卫星视觉特征跟踪与位姿测量

空间碎片或者失效卫星往往绕其惯性主轴做自旋运动,虽然处于一种稳定状态,但是对其运动状态测量的难度相比三轴稳定目标而言又增加了许多,主要体现在复杂光场环境下和目标观测面周期性进出视场引起的特征点丢失、尺度变化和旋转变化,以及长时间连续观测引起的累积误差增大、位姿解算不收敛等难题。通过构建优化目标特征数据库,将传统测量方式中前后帧的匹配转变为当前帧与特征数据库的匹配和特征点的优化,即使中间过程帧出现了偏差仍然可以较好地跟踪后续图像帧的正确位置。在李代数空间下建立位姿向量微分扰动方程,获得测量值与估计值的残差目标函数,基于贝叶斯法则最大后验概率和李群与李代数的对指变换法则,求取位姿向量最优解。解决了李群空间下由于位姿变换矩阵不可加性而无法优化的问题,提高了连续测量过程中系统的测量精度。实验结果表明,无优化测量方法无法保证整个旋转周期的有效测量;通过增加位姿优化过程,连续稳定测量时间明显延长,针对以12（°）/s自旋运动的目标,测量稳定段误差在2°以内,旋转角速度测量误差为0.12（°）/s。     

基于深度强化学习的固定翼无人机编队协调控制方法

由于运动学的复杂性和环境的动态性,控制一组无人机遂行任务目前仍面临较大挑战。首先,以固定翼无人机为研究对象,考虑复杂动态环境的随机性和不确定性,提出了基于无模型深度强化学习的无人机编队协调控制方法。然后,为平衡探索和利用,将ε-greedy策略与模仿策略相结合,提出了ε-imitation动作选择策略;结合双重Q学习和竞争架构对DQN（Deep Q-Network）算法进行改进,提出了ID3QN（Imitative Dueling Double Deep Q-Network）算法以提高算法的学习效率。最后,构建高保真半实物仿真系统进行硬件在环仿真飞行实验,验证了所提算法的适应性和实用性。     

FY-3 Meteorological Satellites and the Applications

FY-3 is the second generation polar-orbiting meteorological satellite of China. The first satellite named FY-3A of this series was launched on 27 May 2008. The first operational satellite named FY-3C of this series was launched on 23 September, 2013. The new generation satellites are to provide three-dimensional, quantitative, multi-spectral global remote sensing data under all weather conditions, which will greatly help the operational numerical weather prediction, global climate change research, climate diagnostics and prediction, and natural disaster monitoring. They will also provide help for many other fields such as agriculture, forestry, oceanography and hydrology. With the abovementioned capability, the FY-3 satellites can make valuable contributions to improving weather forecasts, global natural-disaster and environmental monitoring.      

Coordinated attitude control for flexible spacecraft formation with actuator configuration misalignment

This paper investigates the coordinated attitude control problem for flexible spacecraft formation with the consideration of actuator configuration misalignment. First, an integral-type sliding mode adaptive control law is designed to compensate the effects of flexible mode, environmental disturbance and actuator installation deviation. The basic idea of the Integral-type Sliding Mode Control (ISMC) is to design a proper sliding manifold so that the sliding mode starts from the initial time instant, and thus the robustness of the system can be guaranteed from the beginning of the process and the reaching phase is eliminated. Then, considering the nominal system of spacecraft formation based on directed topology, an attitude cooperative control strategy is developed for the nominal system with or without communication delay. The proposed control law can guarantee that for each spacecraft in the spacecraft formation, the desired attitude objective can be achieved and the attitude synchronization can be maintained with other spacecraft in the formation. Finally, simulation results are given to show the effectiveness of the proposed control algorithm.     

Optimal spacecraft formation establishment and reconfiguration propelled by the geomagnetic Lorentz force

The Lorentz force acting on an electrostatically charged spacecraft as it moves through the planetary magnetic field could be utilized as propellantless electromagnetic propulsion for orbital maneuvering, such as spacecraft formation establishment and formation reconfiguration. By assuming that the Earth’s magnetic field could be modeled as a tilted dipole located at the center of Earth that corotates with Earth, a dynamical model that describes the relative orbital motion of Lorentz spacecraft is developed. Based on the proposed dynamical model, the energy-optimal open-loop trajectories of control inputs, namely, the required specific charges of Lorentz spacecraft, for Lorentz-propelled spacecraft formation establishment or reconfiguration problems with both fixed and free final conditions constraints are derived via Gauss pseudospectral method. The effect of the magnetic dipole tilt angle on the optimal control inputs and the relative transfer trajectories for formation establishment or reconfiguration is also investigated by comparisons with the results derived from a nontilted dipole model. Furthermore, a closed-loop integral sliding mode controller is designed to guarantee the trajectory tracking in the presence of external disturbances and modeling errors. The stability of the closed-loop system is proved by a Lyapunov-based approach. Numerical simulations are presented to verify the validity of the proposed open-loop control methods and demonstrate the performance of the closed-loop controller. Also, the results indicate the dipole tilt angle should be considered when designing control strategies for Lorentz-propelled spacecraft formation establishment or reconfiguration.     

A photoionization method for estimating BLR “size” in quasars

We describe an alternate way to estimate Broad Line Region (BLR) radii for type-1 AGN based on determination of physical conditions in the BLR under the assumption that the line emitting gas is photoionized by a central continuum source. We derive “diagnostic” intensity ratios involving UV lines Aliiiλ$\lambda$1860, Siiii]λ$\lambda$1892 and Civλ$\lambda$1549 which enable us to compute the ionizing photon flux, and hence BLR radius from the ionization parameter definition. We compare our estimates of BLR radii with values independently obtained from reverberation monitoring of Hβ$\beta$ and, in a few cases, of C ivλ$\lambda$1549. We analyze the interpretation of the photoionization estimates in the 4D eigenvector 1 context, and discuss in some detail the case of 3C 390.3. For this object we are able to provide not only the ionizing photon flux, but also an estimate of density and ionization parameter from the measured diagnostic ratios. We also compare black hole masses obtained from this method with values derived from widely-applied correlations between mass, line broadening and luminosity. Good agreement is found for both radius and black hole mass comparisons.     

Design and performances of laser retro-reflector arrays for Beidou navigation satellites and SLR observations

Beidou is the regional satellite navigation system in China, consisting of three kinds of orbiting satellites, MEO, GEO and IGSO, with the orbital altitudes of 21500–36000 km. For improving the accuracy of satellites orbit determination, calibrating microwave measuring techniques and providing better navigation service, all Beidou satellites are equipped with laser retro-reflector arrays (LRAs) to implement high precision laser ranging. The paper presents the design of LRAs for Beidou navigation satellites and the method of inclined installation of LRAs for GEO satellites to increase the effective reflective areas for the regional ground stations. By using the SLR system, the observations for Beidou satellites demonstrated a precision of centimeters. The performances of these LRAs on Beidou satellites are very excellent.     

静止轨道卫星东西位置保持控制参数的优化方法

为提高静止轨道卫星东西位置保持的轨道控制精度,提出一种优化轨道控制参数和推进剂消耗量估算的方法.这种方法考虑卫星轨道机动期间其姿态控制喷气对卫星轨道的摄动力,据此对位置保持参数中的轨控推力器点火时间进行补偿,并根据所有推力器的喷气时间估算推进剂消耗量,以修正轨控策略,实现更加精准的轨道控制效果.以在轨运行的静止轨道卫星的多次向西位置保持的变轨参数优化过程为实例,验证本方法的有效性和正确性,可应用于后续静止轨道卫星东西位置的实际操作中.