Modeling and flapping vibration suppression of a novel tailless flapping wing micro air vehicle

This paper establishes and analyzes a high-fidelity nonlinear time-periodic dynamic model and the corresponding state observer for flapping vibration suppression of a novel tailless Flapping Wing Micro Air Vehicle(FWMAV), named NPU-Tinybird. Firstly, a complete modeling of NPU-Tinybird is determined, including the aerodynamic model based on the quasi-steady method, the kinematic and dynamic model about the mechanism of flapping and attitude control,combined with the single rigid body dynamic mod...     

OVERSEAS BRIEFS(Feb.1-28,2002)

▲Feb. 1 UAL Co. announced a US$308 million loss for the fourth quarter and a US$2.1 billion yearly loss, a record loss in the history of aviation sector. ▲Early in Feb. Swiss Air Lines, the new Swiss national airlines, released its registered trademark.…     

DOMESTIC BRIEFS

▲Sept. 1 Minister of CAAC Yang Yuanyuan and Canadian Transport Minister signed an MoU on safety technology cooperations between CAAC and Transport Ministry of Canada with an aim to carry out cooperations in safety management system and personnel training. ▲Sept. 7 CAAC and a civil aviation delegation from Chile held a meeting in Beijing to discuss a more relaxed air transport agreement. ▲Sept. 9 A B737-800 of the Chongqing Branch of Air China was handed over to Ameco for MRO s…     

OVERSEAS BRIERS

▲Oct. 2 Having completed reorga-nization and merger, Japan Airlines, thelargest airline in Japan, and the third largest,Japan Air Systems, began to operate underthe uniform name of Japan Airline Group.▲Oct. 7 The EU said it would notoppose the 1.43 billion EURO reinvestmentprogram of Alitalia, a key part of the airline'srestructuring plan.▲Oct. 7 The 12th ACI World/PacificConference and Exhibition was held inJapan. The theme of the exhibition was: glo-bal airlines face common …     

Nonlinear dynamics of a flapping rotary wing: Modeling and optimal wing kinematic analysis

The analysis of the passive rotation feature of a micro Flapping Rotary Wing(FRW)applicable for Micro Air Vehicle(MAV) design is presented in this paper. The dynamics of the wing and its influence on aerodynamic performance of FRW is studied at low Reynolds number(~10~3).The FRW is modeled as a simplified system of three rigid bodies: a rotary base with two flapping wings. The multibody dynamic theory is employed to derive the motion equations for FRW. A quasi-steady aerodynamic model is utilized for the calculation of the aerodynamic forces and moments. The dynamic motion process and the effects of the kinematics of wings on the dynamic rotational equilibrium of FWR and the aerodynamic performances are studied. The results show that the passive rotation motion of the wings is a continuous dynamic process which converges into an equilibrium rotary velocity due to the interaction between aerodynamic thrust, drag force and wing inertia. This causes a unique dynamic time-lag phenomena of lift generation for FRW, unlike the normal flapping wing flight vehicle driven by its own motor to actively rotate its wings. The analysis also shows that in order to acquire a high positive lift generation with high power efficiency and small dynamic time-lag, a relative high mid-up stroke angle within 7–15° and low mid-down stroke angle within -40° to -35° are necessary. The results provide a quantified guidance for design option of FRW together with the optimal kinematics of motion according to flight performance requirement.     

Reorganization of China''''s Civil Aviation Takes Shape

Following a long period of consideration and discussion, thereorganization of airlines and air service enterprises under the directadministration of CAAC has finally been launched.On April 27, the CAAC held a meeting posting the reorganization planbased on the principle of "self-willingness of the enterprises, guidance of thegovernment and giving play to strong points of groups". According to theplan, new airline groups will be organized, based on Air China, China Easternand China Southe…     

Review on ultra-lightweight flapping-wing nano air vehicles:Artificial muscles,flight control mechanism,and biomimetic wings

Flying insects are capable of flapping their wings to provide the required power and control forces for flight. A coordinated organizational system including muscles, wings, and control architecture plays a significant role, which provides the sources of inspiration for designing flapping-wing vehicles. In recent years, due to the development of micro-and meso-scale manufacturing technologies, advances in components technologies have directly led to a progress of smaller Flapping-Wing Nano Air V...     

Shanghai Aviation Hub Strategic Planning Approved

he Shanghai Aviation Hub Construction LeadingGroup held its second working meeting in Beijingon November 1. Present at the meeting wereCAAC Minister Yang Yuanyuan, Shanghai Mayor HanZheng, Vice-Mayor Yang Xiong, CAAC Vice-MinisterYang Guoqing, Zhang Yaokuan, director of Air TrafficAdministration under the Headquarters of the GeneralStaff and deputy office director of the State Air TrafficCommission, Yu Zhixue, vice commander of Air Forceunder the Nanjing Military Area, and o…     

Navigation sensors and systems in GNSS degraded and denied environments

Position, velocity, and timing(PVT) signals from the Global Positioning System(GPS)are used throughout the world but the availability and reliability of these signals in all environments has become a subject of concern for both civilian and military applications. This presentation summarizes recent advances in navigation sensor technology, including GPS, inertial, and other navigation aids that address these concerns. Also addressed are developments in sensor integration technology with several examples described, including the Bluefin-21 system mechanization.     

An anti-image interference quadrature IF architecture for satellite receivers

Since Global Navigation Satellite System（GNSS） signals span a wide range of frequency, wireless signals coming from other communication systems may be aliased and appear as image interference. In quadrature intermediate frequency（IF） receivers, image aliasing due to in-phase and quadrature（I/Q） channel mismatches is always a big problem. I/Q mismatches occur because of gain and phase imbalances between quadrature mixers and capacitor mismatches in analog-to-digital converters（ADC）. As a result, the dynamic range and performance of a receiver are severely degraded. In this paper, several popular receiver architectures are summarized and the image aliasing problem is investigated in detail. Based on this analysis, a low-IF architecture is proposed for a single-chip solution and a novel and feasible anti-image algorithm is investigated. With this anti-image digital processing, the image reject ratio（IRR） can reach approximately above50 dB, which relaxes image rejection specific in front-end circuit designs and allows cheap and highly flexible analog front-end solutions. Simulation and experimental data show that the antiimage algorithm can work effectively, robustly, and steadily.     

Ameco-Beijing——a big name in a booming market

Catching up with the fast development of worldeconomy,China pulled up its bamboo curtain andsponsored an even more faster revolution of economytill 1978.The cooperation with German Lufthansa isone of China’s major steps to upgrade its civil avia-tion industry.The Aircraft Maintenance＆EngineeringCo.-Beijing(Ameco-Binjing),a partnership start-ed in 1989 by Air China and German Lufthansa is thelargest and the most powerful civil aircraft mainte-nance company in China.     

Application of Active Flow Control Technique for Gust Load Alleviation

A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi "Global Hawk" airfoil using arrays of jets during the gust process. Based on unsteady Navier-Stokes equations, the grid-velocity method is introduced to simulate the gust influence, and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well. An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil’s surface to emulate the time dependent velocity boundary conditions. Firstly, after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack, it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references. Furthermore, gust response characteristic for the quasi "Global Hawk" airfoil is analyzed. Five kinds of flow control techniques are introduced as steady blowing, steady suction, unsteady blowing, unsteady suction and synthetic jets. The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice. Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation, can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.     

OVERSEAS BRIEFS(Nov.1-30)

▲Nov. 1 United Airlines of the U.S. reports a record $1.16 billion loss in the third quarter, the worst quarterly deficit in the company＇s history. ▲Nov. 1 Delta Air Lines says it＇s going to lay off 2 000 employees based on its cost-reducing plan as declared earlier. ▲Nov. 1 The Dutch KLM Airlines issues its Q2 results, posting a sharp 77% decline of profit to only 27 million EURO. ▲Nov. 4 The Emirates Airlines announces an aircraft deal with Boeing and Airbus with a total value…     

More International Conferences To Be Held This Year

More friends will come to Shanghai as more than 70 international conferences and events will be held in the city. Some meetings will have more than 3,000 participants apiece, city government spokeswoman Jiao Yang said at a press conference.Some important international conferences will be held in Shanghai in April, including the Global Help-the-Poor Conference held by the World Bank and the 60th Annual Meeting of the UN Economy and Society Commission for Asia-Pacific (ESCAP).Jiao said VIPs, who will attend these conferences, will include UN Secretary General Kofi Annan and presidents of South Africa, Brazil and Tanzania to indicate the importance of these events.     

一种新的气动弹性鲁棒稳定性分析方法(英文)

Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation （LFT） representation of perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by using the structured singular value ,u-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.     

Reinforcement learning based UAV formation control in GPS-denied environment

Highly accurate positioning is a crucial prerequisite of multi Unmanned Aerial Vehicle close-formation flight for target tracking, formation keeping, and collision avoidance. Although the position of a UAV can be obtained through the Global Positioning System(GPS), it is difficult for a UAV to obtain highly accurate positioning data in a GPS-denied environment(e.g., a GPS jamming area, suburb, urban canyon, or mountain area); this may cause it to miss a tracking target or collide with another UA...     

Comparison of alternative route selection strategies based on simulation optimization

Air traffic flow management (ATFM) is a collaborative process between the airspace provider and the airspace users. The result of the collaboration should be an outcome that maxi-mizes the utility of the system without excessively penalizing any of the agents. This paper develops a discrete-event simulation model which consists of aggregate departure/arrival airports, flight routes, and sectors for evaluating the alternative collaborative route selection strategy. Given the different perspectives from air traffic control center (ACC) and airlines, eight performance-metrics and five alternative route selection strategies represent the past, current and proposed air traffic flow management operations that were evaluated. The Monte Carlo method combined with the Optimal Computing Budget Allocation (OCBA) simulation optimization technique is employed to assess the performance of different strategies. A case study of the upper air routes in central and southern China shows that the proposed model can be readily implemented to simulate different kinds of air traffic flow management strategies and predict the effect of changes on the airspace sys-tem. It also shows that the proposed alternative collaborative route selection strategy is an effective way in alleviating the en-route traffic congestion.     

CFD Study of NO_x Emissions in a Model Commercial Aircraft Engine Combustor

Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics (CFD) is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes (RANS) equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection (LDI) combustor. The test rig studied in this paper is called low emission stirred swirl (LESS) combustor, which is a two-stage model combustor, fueled with liquid kerosene (RP-3) and designed by Beihang University (BUAA). The main stage of LESS combustor employs the principle of lean prevaporized and premixed (LPP) concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.     

Isothermal study of effusion cooling flows using a large eddy simulation approach

An isothermal numerical study of effusion cooling flow is conducted using a large eddy simulation(LES) approach.Two main types of cooling are considered,namely tangential film cooling and oblique patch effusion cooling.To represent tangential film cooling,a simplified model of a plane turbulent wall jet along a flat plate in quiescent surrounding fluid is considered.In contrast to a classic turbulent boundary layer flow,the plane turbulent wall jet possesses an outer free shear flow region,an inner near wall region and an interaction region,characterised by substantial levels of turbulent shear stress transport.These shear stress characteristics hold significant implications for RANS modelling,implications that also apply to more complex tangential film cooling flows with non-zero free stream velocities.The LES technique used in the current study provides a satisfactory overall prediction of the plane turbulent wall jet flow,including the initial transition region,and the characteristic separation of the zero turbulent shear stress and zero shear strain locations.Oblique effusion patch cooling is modelled using a staggered array of 12 rows of effusion holes,drilled at 30° to the flat plate surface.The effusion holes connect two channels separated by the flat plate.Specifically,these comprise of a channel representing the combustion chamber flow and a cooling air supply channel.A difference in pressure between the two channels forces air from the cooling supply side,through the effusion holes,and into the combustion chamber side.Air from successive effusion rows coalesces to form an aerodynamic film between the combustion chamber main flow and the flat plate.In practical applications,this film is used to separate the hot combustion gases from the combustion chamber liner.The numerical model is shown to be capable of accurately predicting the injection,penetration,downstream decay,and coalescence of the effusion jets.In addition,the numerical model captures entrainment of the combustion chamber mainstream flow towards the wall by the presence of the effusion jets.Two contra-rotating vortices,with axes of rotation along the stream-wise direction,are predicted as a result of this entrainment.The presence and characteristics of these vortices are in good agreement with previous published research.      

A Seminar On Shanghai Airport Airspace Held

A seminar on Shanghai airport airspace, sponsored by the airport's second-phase project headquarters and East China Air Traffic Administration, was held in Shanghai between March 21 and 23.Present at the seminar were Shanghai Vice-Mayor