Shape control of spacecraft formation using a virtual spring-damper mesh

This paper derives a distance-based formation control method to maintain the desired formation shape for spacecraft in a gravitational potential field. The method is an analogy of a vir-tual spring-damper mesh. Spacecraft are connected virtually by spring-damper pairs. Convergence analysis is performed using the energy method. Approximate expressions for the distance errors and control accelerations at steady state are derived by using algebraic graph representations and results of graph rigidity. Analytical results indicate that if the underlying graph of the mesh is rigid, the convergence to a static shape is assured, and higher formation control precision can be achieved by increasing the elastic coefficient without increasing the control accelerations. A numerical exam-ple of spacecraft formation in low Earth orbit confirms the theoretical analysis and shows that the desired formation shape can be well achieved using the presented method, whereas the orientation of the formation can be kept pointing to the center of the Earth by the gravity gradient. The method is decentralized, and uses only relative measurement information. Constructing a distributed virtual structure in space can be the general application area. The proposed method can serve as an active shape control law for the spacecraft formations using propellantless internal forces.     

Cooperative guidance of seeker-less missile considering localization error

To perform an accurate fire-and-forget attack of seeker-less missile with the consideration of the localization error, a new cooperative guidance strategy of multi-missiles is proposed in this work. Firstly, an estimated position of the seeker-less missile is carefully selected, based on which the slant angle of the line between the estimated and real positions of the seeker-less missile is approximately derived inspired by the localization theory of GPS(Global Position System).Then, respectively based on the guidance law considering the impact angle and time constraints, the consensus theory and the finite-time convergence approach, three cooperative guidance laws employing the previously obtained slant angle are derived for intensive attack to address either a stationary or maneuvering target. Simulation results well demonstrate the effectiveness and advantages of the proposed cooperative guidance strategy.     

Three-dimensional guidance law based on adaptive integral sliding mode control

For the terminal guidance problem of missiles intercepting maneuvering targets in the three-dimensional space, the design of guidance laws for non-decoupling three-dimensional engage-ment geometry is studied. Firstly, by introducing a finite time integral sliding mode manifold, a novel guidance law based on the integral sliding mode control is presented with the target acceler-ation as a known bounded external disturbance. Then, an improved adaptive guidance law based on the integral sliding mode control without the information of the upper bound on the target accel-eration is developed, where the upper bound of the target acceleration is estimated online by a designed adaptive law. The both presented guidance laws can make sure that the elevation angular rate of the line-of-sight and the azimuth angular rate of the line-of-sight converge to zero in finite time. In the end, the results of the guidance performance for the proposed guidance laws are pre-sented by numerical simulations. Although the designed guidance laws are developed for the con-stant speed missiles, the simulation results for the time-varying speed missiles are also shown to further confirm the designed guidance laws.     

航空术语的构词分析

以全国科学技术名词审定委员会公布的"航空科学技术名词"为览本,对航空术语的词性和构型进行分析,通过举例作出了某些详述,并推导出对外来术语的吸纳方法和原则。     

弹-架间隙的非线性模拟与特性分析

以大长径比低速旋转火箭为例,探讨弹-架间隙非线性特性对不同发射装置系统的动力响应的影响,当飞行器以S个定心部沿发射装置滑移时,根据弹、架横向相对位移确定其定心部处接触刚度和支承特性,模拟弹-架间隙效应。分别就刚性和柔性两种发射装置,分析了间隙量、支承刚度和转速等因素对飞行器发射中的姿态和系统动力特性的影响,算例与实际情况的相吻合证明了该方法的有效性。     

相对测量在编队卫星自主定轨中的应用

针对编队卫星自主定轨问题进行了研究,设计了一种完全不依赖于地面站和GPS系统的自主导航方案。利用星间测量信息进行卫星编队相对轨道状态的自主确定;并在利用磁强计进行卫星绝对轨道自主确定的基础上,引入星间测量信息提高绝对定轨精度;设计扩展卡尔曼滤波器进行卫星编队轨道状态估计,数学仿真结果验证了这种导航方案和算法的有效性。     

Deep Impact: A Large-Scale Active Experiment on a Cometary Nucleus

The Deep Impact mission will provide the first data on the interior of a cometary nucleus and a comparison of those data with data on the surface. Two spacecraft, an impactor and a flyby spacecraft, will arrive at comet 9P/Tempel 1 on 4 July 2005 to create and observe the formation and final properties of a large crater that is predicted to be approximately 30-m deep with the dimensions of a football stadium. The flyby and impactor instruments will yield images and near infrared spectra (1–5 μm) of the surface at unprecedented spatial resolutions both before and after the impact of a 350-kg spacecraft at 10.2 km/s. These data will provide unique information on the structure of the nucleus near the surface and its chemical composition. They will also used to interpret the evolutionary effects on remote sensing data and will indicate how those data can be used to better constrain conditions in the early solar system.     

无人机编队飞行控制器设计

主要对两架无人机斜线编队控制进行研究,建立了相应的数学模型,并基于PI控制律分别设计了x,y两个方向的控制器,利用解析和数值计算两种方法解算.仿真结果表明,设计的控制器可以控制僚机跟随长机机动,保持原有的相对位置和姿态.     

机载聚束式合成孔径雷达的成象处理设计

针对机载聚束式合成孔径雷达工作模式可在小目标范围内实现高分辨力成象的特点，提出了一种以解线性调频技术为核心的，适于聚束式ＳＡＲ成象的灵活高效的信号处理方法和流程。     

地地战术导弹子母弹抛射与散布建模仿真

基于对子弹的抛射和末端弹道的物理过程建模进行了仿真计算,研究了各层子弹抛射速度、抛射延时给子弹分布带来的影响。结果表明,通过适当调整母弹弹道、抛射延时等参数,可以有效提高子母弹的覆盖面积。