直接力与气动力复合控制拦截弹建模与控制

建立了大气层内直接力与气动力复合控制拦截弹的姿态运动模型,应用混杂自动机建立了拦截弹的切换模型,给出了控制系统的切换规律和直接力的控制规律。该方法反映了拦截弹在不同状态间的切换,便于拦截弹的控制,易于工程实现。仿真结果表明,该方法能够在节省使用脉冲发动机的情况下有效的实现拦截弹的姿态调整,显示了该方法的有效性和优越性。     

航天短讯

第三颗瑟拉亚静止轨道区域个人移动通信卫星将于2007年1月发射;亚洲卫星-5将于2008年年中发射。     

务实 高效 创新 中法民航技术合作50年

1966年,中国和法国签订航空交通协定,两国正式建立航空关系。历经50年发展,本着互利共赢的原则,两国在民航众多领域开展了务实、高效的合作。中法两国政治互信和民航关系不断加深,为提升两国民航合作水平、拓展合作宽度和深度,提供了重要支撑和保障。在航空运输之外,中法双方在民航技术领域开展的合作堪称两国民航合作的表率,合作业务范畴涵盖空中交通管理、航空安全、适航与飞行标准、法律法规、人员教育与培训等,促进了中国民航安全监管水平和运营保障能力的有效提升,为法国及欧洲先进的民航产品和技术进入中国市场创造了机遇,也为两国共同致力于民航技术创新、开发新市场提供了基础和平台。其中,空中交通管理、航空安全以及人员教育与培训,是中法两国在民航技术领域有历史、有深度、有成效的合作项目。无论是中法两国民航管理部门,还是两国相关业务领域的航空企业和航空院校,都开展了多层次、多形式的国际交流与合作。从最初的产品技术引进、"送出去"培训,到现在的合资生产、合作办学,合作方式的变化以及合作水平的提升,体现出中法两国面对变化着的市场环境和市场需求,不断扩大在民航技术领域的合作意愿和开放程度,向着越来越密切、越来越频繁的方向发展。     

全方位的中法民航合作

正1966年,法国航空公司成为最早开通中国航线的西方航空公司。作为第一个与中国建交的西方大国,法国也是第一个与中国实现通航的西方国家。作为双边务实合作的重要内容之一,国际航线的开辟与两国的政治、经济交往密切相关。中法民航关系,简而言之,可以包括以下几个方面:第一是航空运输关系,第二是民航技术合作,第三是航空产品与服务贸易合作,第四     

Investigation of MHD power generation with supersonic non-equilibrium RF discharge

Magnetohydrodynamic (MHD) power generation with supersonic non-equilibrium plasma is demonstrated. Capacitively coupled radio frequency (RF) discharge (6 MHz, maximum continual power output of 200 W) was adopted to ionize the Mach number 3.5 (650 m/s), 0.023 kg/m3 airflow. In a MHD channel of 16 mm × 10 mm × 20 mm, MHD open voltage of 10 V is realized in the magnetic field of 1.25 T, and power of 0.12 mW is extracted steadily and con-tinuously in the magnetic field of 1 T. The reasons for limited power generation are proposed as:low conductivity of RF discharge; large touch resistance between MHD electrode and plasma;strong current eddies due to flow boundary layer. In addition, the cathode voltage fall is too low to have obvious effects on MHD power generation.     

Closed-loop dynamic control allocation for aircraft with multiple actuators

A closed-loop control allocation method is proposed for a class of aircraft with multiple actuators. Nonlinear dynamic inversion is used to design the baseline attitude controller and derive the desired moment increment. And a feedback loop for the moment increment produced by the deflections of actuators is added to the angular rate loop, then the error between the desired and actual moment increment is the input of the dynamic control allocation. Subsequently, the stability of the closed-loop dynamic control allocation system is analyzed in detail. Especially, the closedloop system stability is also analyzed in the presence of two types of actuator failures: loss of effectiveness and lock-in-place actuator failures, where a fault detection subsystem to identify the actuator failures is absent. Finally, the proposed method is applied to a canard rotor/wing (CRW) aircraft model in fixed-wing mode, which has multiple actuators for flight control. The nonlinear simulation demonstrates that this method can guarantee the stability and tracking performance whether the actuators are healthy or fail.     

Calibration of a γ-Re_θ transition model and its validation in low-speed flows with high-order numerical method

Based on the Reynolds-averaged Navier–Stokes(RANS)equations and structured grid technology,the calibration and validation of γ-Re_θ transition model is preformed with fifth-order weighted compact nonlinear scheme(WCNS),and the purpose of the present work is to improve the numerical accuracy for aerodynamic characteristics simulation of low-speed flow with transition model on the basis of high-order numerical method study.Firstly,the empirical correlation functions involved in the γ-Re_θ transition model are modified and calibrated with experimental data of turbulent flat plates.Then,the grid convergence is studied on NLR-7301 two-element airfoil with the modified empirical correlation.At last,the modified empirical correlation is validated with NLR-7301 two-element airfoil and high-lift trapezoidal wing from transition location,velocity profile in boundary layer,surface pressure coefficient and aerodynamic characteristics.The numerical results illustrate that the numerical accuracy of transition length and skin friction behind transition location are improved with modified empirical correlation function,and obviously increases the numerical accuracy of aerodynamic characteristics prediction for typical transport configurations in low-speed range.     

SpaceDev公司获得美国空军纳卫星合同

据2006年3月29日报道，SpaceDev公司获得了美国空军研究实验室价值125万美元、初步设计1颗纳卫星的合同。该卫星又被称为“评估局部空间的自主纳卫星护卫者”（ANGELS）。SpaceDev公司负责提供卫星的硬件集成、详细的设计图表、软件及飞行运算、操作手册、试验计划和接口控制文件。     

Reactive oxygen species and antioxidant enzymes activity of Anabaena sp. PCC 7120 (Cyanobacterium) under simulated microgravity

It was found that reactive oxygen species in Anabaena cells increased under simulated microgravity provided by clinostat. Activities of intracellular antioxidant enzymes, such as superoxide dismutase, catalase were higher than those in the controlled samples during the 7 days' experiment. However, the contents of glutathione [correction of gluathione], an intracellular antioxidant, decreased in comparison with the controlled samples. The results suggested that microgravity provided by clinostat might break the oxidative/antioxidative balance. It indicated a protective mechanism in algal cells, that the total antioxidant system activity increased, which might play an important role for algal cells to adapt the environmental stress of microgravity.     

An improved multiple model GM-PHD filter for maneuvering target tracking

In this paper, an improved implementation of multiple model Gaussian mixture probability hypothesis density (MM-GM-PHD) filter is proposed. For maneuvering target tracking, based on joint distribution, the existing MM-GM-PHD filter is relatively complex. To simplify the filter, model conditioned distribution and model probability are used in the improved MM-GM-PHD filter. In the algorithm, every Gaussian components describing existing, birth and spawned targets are estimated by multiple model method. The final results of the Gaussian components are the fusion of multiple model estimations. The algorithm does not need to compute the joint PHD distribution and has a simpler computation procedure. Compared with single model GM-PHD, the algorithm gives more accurate estimation on the number and state of the targets. Compared with the existing MM-GM-PHD algorithm, it saves computation time by more than 30%. Moreover, it also outperforms the interacting multiple model joint probabilistic data association (IMMJPDA) filter in a relatively dense clutter environment.