垂直起降无人机总体方案分析

垂直起降无人机是垂直起降技术和无人机的结合体。它既有直升机的垂直起降和悬停能力，又具有固定翼飞机的速度快、航程远的特点。还具备一般无人机的基本特点，可满足执行特殊任务的需要。因无需考虑机载人员的因素，垂直起降无人机的总体设计方案更加灵活和多样。在分析现有各种垂直起降无人机方案的基础上，提出了“双旋翼尾座式飞翼”布局，并对其飞行控制策略进行了研究。     

Improving flight performance of UAVs by ice shape modulation

Aircraft icing poses a great threat to flight safety.In response to the characteristics of high-power consumption,large volume,and heavy weight of traditional anti-/de-icing technologies,the concept of ice shape modulation is proposed,which is called ice tolerant flight.Firstly,the flight performance of Unmanned Aerial Vehicle(UAV)was compared in three states:no ice,full ice,and modulated ice through flight tests.It was found that ice shape modulation has a significant improve-ment effect on the aerodynamic performance of aircraft under icing conditions.Under the three modulated ice shape conditions in this experiment,the lift coefficient of the UAV under different ice shape modulation conditions increased by 18％-33％,and the stalling angle was delayed by 3°-5°.Subsequently,the pressure distribution,streamlines in the flow field,and detached vortex dis-tribution of the UAV model in these three states were obtained through numerical simulation,to study the mechanism of ice shape modulation on the aerodynamic performance of aircraft.The sim-ulation found that the reason for the improvement of the wings effect after ice shape modulation is that the modulated area forms a leading-edge protrusion structure similar to a vortex generator.This structure prolongs the mixed flow region on the wings surface and reduces the trend of flow separation,which plays a role in increasing lift and reducing drag for UAVs under icing conditions.Finally,a reverse reachable set that can be used for unexpected state recovery is used as the defini-tion of flight safety boundaries,and an aircraft dynamics model is established to obtain flight safety boundaries for different states.Research has found that the flight safety boundary of the UAV in a no ice state is greater than that in a modulated ice state,and the safety boundary in a modulated ice state is greater than that in a full ice state.Compared with the full ice state,the flight safety bound-ary after modulation has expanded by 27.0％.The scheme of ice shape modulation can provide a basis for the flight safety of aircraft under icing conditions.     

Autonomous navigation to quasi-periodic orbits near translunar Ubration points

Libration-point missions have been very useful and successful. Due to the unstable natures of most of these orbits, the long-time stationkeeping demands frequent maneuvers and precise orbit determinations. Earth-based tracking will have to undertake much more responsibilities with the increasing number of libration missions. An autonomous navigation system could offer a better way to decrease the need for Earth-based tracking. Nevertheless, when an autonomous navigation system is applied, there are three important factors affecting autonomous navigation accuracy, i.e., the accuracy of initial conditions, the accuracy of measurements, and the accuracy of onboard dynamics for propagation. This paper focuses on analyzing the influence from the third factor and finding an appropriate navigation dynamics, which can satisfy the requirement of estimation accuracy but not cause too much burden for onboard computation. When considering the restricted three-body model and the bicircular restricted four-body model as navigation dynamics, the astrin- gency is not shown during the simulations. Meanwhile, when considering the influences of the Sun＇s direct and indirect perturbations and the eccentricity of the Moon＇s orbit, a new navigation dynamic model with the standard ephemerides is proposed. The simulation shows the feasibility of the proposed model.     

UAVs: the future. [A century of powered flight: 1903-2003]

Unmanned air vehicles (UAV) are assuming a prominent role in aviation and the future may have already arrived. Most of us have heard of the Global Hawk and Predator UAVs, which have been collecting real-time battlefield data without risking loss of life. However, the most amazing performance and avionics can be found in airplane-model-size MiniUAVs and insect-like MicroUAVs still on the drawing board. Meanwhile the all-electric NASA Helios "tower in the sky" is moving ever closer to reality.     

Navigating towards the future: transitioning from terrestrial radio navigation to satellite navigation and airborne surveillance

This paper presents a proposal for transitioning from terrestrial-based navigation aids to implementing satellite and airborne surveillance as the primary navigation means. The transition occurs through several steps. First, the installation and use of modern navigation and surveillance equipment is mandated by the regulatory organizations. The installations should take place in a sequenced fashion to allow time for companies to absorb the initial cost. Next, the existing network of terrestrial navigation aids is down-sized leaving only the areas of heaviest use in service. At this point, the global positioning system (GPS) will be deemed the primary method of terrestrial and oceanic travel. Finally, terrestrial navigation stations will be available around airports and the remaining stations will be put in a standby condition for use in the event of a national emergency. This paper will discuss the security benefits and examples of cost savings through implementation of these steps.     

Autonomous navigation method of satellite constellation based on adaptive forgetting factors

To address the problem that model uncertainty and unknown time-varying system noise hinder the filtering accuracy of the autonomous navigation system of satellite constellation,an autonomous navigation method of satellite constellation based on the Unscented Kalman Filter with Adaptive Forgetting Factors (UKF-AFF) is proposed.The process noise covariance matrix is estimated online with the strategy that combines covariance matching and adaptive adjustment of forgetting factors.The adaptive adjustment coefficient based on squared Mahalanobis distance of state residual is employed to achieve online regulation of forgetting factors,equipping this method with more adaptability.The intersatellite direction vector obtained from photographic observations is introduced to determine the constellation satellite orbit together with the distance measurement to avoid rank deficiency issues.Considering that the number of available measurements varies online with intersatellite visibility in practical applications such as time-varying constellation configurations,the smooth covariance matrix of state correction determined by innovation and gain is adopted and constructed recursively.Stability analysis of the proposed method is also conducted.The effectiveness of the proposed method is verified by the Monte Carlo simulation and comparison experiments.The estimation accuracy of constellation position and velocity of UKF-AFF is improved by 30%and 44%respectively compared to those of the extended Kalman filter,and the method proposed is also better than other several adaptive filtering methods in the presence of significant model uncertainty.     

世界垂直起降动力装置的演进和展望

介绍了半个世纪以来世界垂直起降动力装置发展的概况,阐述了垂直起降动力装置的类型、演进情况并展望了其发展前景.     

Aerodynamic scaling to free flight conditions: Past and present

This report summarizes some of the problems when wind tunnel data should be scaled to free flight conditions. The main challenges in performing this extrapolation is how model support, wall interference, aeroelastic effects and a potentially lower Reynolds number in the wind tunnel should be corrected. A historical review of scale effects is presented showing wind tunnel to flight discrepancies of different types of aircraft configurations. An overview of scaling methodologies and Reynolds number effects are presented and discussed. Some modern approaches where computational fluid dynamics (CFD) are used, together with wind tunnel testing, in order to identify scaling phenomena are presented as well.     

HUD——提升飞行安全的有力工具

一、HGS系统综述与工作原理HUD(Head-up Display),平视显示器,一种可以把飞行数据投射到驾驶员正前方的透明显示组件上的显示器,它可以使驾驶员保持平视获取飞行信息。平视显示着陆系统(HUDLS)是具备进近着陆引导能力的平视显示系统,它可在整个飞机进近、着陆或复飞阶段提供平视显示引导,其组成包括自     

Renewal, reform, and return to flight

The Washington Watch column discusses budget issues on Capitol Hill relating to aerospace issues, including the shuttle's delayed return to flight and Michael Griffin becoming the new NASA administrator; the Transportation Security Administration becoming downsized; and new personnel at the Pentagon.     

EASA小型垂直起降航空器专用条件及符合性方法研究

研究了SC-VTOL-01与CS-23各章的主要差异,分析了MOC SC-VTOL的编制思路,总结出EASA小型垂直起降航空器专用条件审定类型与运行场景相匹配的特点以及符合性方法逐渐完善和补充的趋势.     

Leveraging flight heritage to new compactPCI space systems: afusion of architectures

The advent of NASA-JPL's X2000 architecture has brought compactPCI (cPCI) to the forefront as the system bus of choice for space data processing. This paper presents a hybrid architecture allowing the inclusion of new, high performance cPCI modules with heritage VME-based modules. The hybrid system yields a cost-effective, performance optimized processing solution for space     

无人机在伊拉克战争中的作用及其思考

本文通过分析2003年伊拉克战争中美军无人机的作战使用情况和特点,探讨军用无人机未来的发展之路。     

Identification of nonlinear flight dynamics: theory and practice

This article presents an innovative time-domain nonlinear mapping-based identification method. The method reported is applied to identify the unknown parameters of multivariable dynamic systems which are mapped by nonlinear differential equations. A systematic identification method is introduced, and a novel algorithm is developed using nonlinear error maps. An analysis of parameter convergence is provided and the regions of convergence can be found using the second method of Lyapunov. Innovative nonquadratic Lyapunov functions are designed and used. Analytical and numerical studies are performed to illustrate and validate the identification concept. The unsteady flight of a high-alpha aircraft in the longitudinal axis is chosen as a nonlinear case study. The unknown parameters are identified. Simulation results show that the model dynamics match the experimental data. The reported example demonstrates that the time-domain nonlinear mapping-based identification method ensures robustness and reduces major shortcomings in stability, convergence, and computational efficiency compared with other algorithms available     

改善箭机分离载机飞行品质的状态反馈器研究

为了改善内装式运载火箭与载机分离过程载机的飞行品质,应用现代控制理论,以一组期望的闭环极点为设计目标,利用正比于状态变量的线性控制律,设计带有状态观测器的状态反馈系统。通过Bass-Gura法求解反馈增益,基于时域分析法数值模拟了带有状态反馈器飞机的飞行品质。仿真结果表明,长、短周期运动变为收敛的周期模态,飞行品质提高到1级标准,可见状态反馈器设计是一种改善箭机分离过程载机飞行品质的高效可行的方法。     

一种变参数滑模变结构控制及飞行控制应用研究

提出了一种新的负指数分布变参数滑模变结构控制,采用增益调度方法调节变结构控制器参数。通过自适应调节边界层系数、滑动模系数和控制增益系数实现降低能耗、减弱颤振的目标。对某飞机短周期迎角稳定控制系统进行仿真,结果表明了该控制方案的有效性和实用性。     

Intelligent modeling and identification of aircraft nonlinear flight

In this paper, a new approach has been proposed to identify and model the dynamics of a highly maneuverable fighter aircraft through artificial neural networks（ANNs）. In general, aircraft flight dynamics is considered as a nonlinear and coupled system whose modeling through ANNs, unlike classical approaches, does not require any aerodynamic or propulsion information and a few flight test data seem sufficient. In this study, for identification and modeling of the aircraft dynamics, two known structures of internal and external recurrent neural networks（RNNs） and a proposed structure called hybrid combined recurrent neural network have been used and compared.In order to improve the training process, an appropriate evolutionary method has been applied to simultaneously train and optimize the parameters of ANNs. In this research, it has been shown that six ANNs each with three inputs and one output, trained by flight test data, can model the dynamic behavior of the highly maneuverable aircraft with acceptable accuracy and without any priori knowledge about the system.