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Investigation of lateral-directional aerodynamic parameters identification method for fly-by-wire passenger airliners

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Chinese Journal of aeronautics 2014年第4期27卷 781-790页

作者： Wu Zhao Wang Lixin Lin Jiaming Ai Junqiang school of aeronautic science and engineering Beihang University

A new identification method is proposed to solve the problem of the influence on the loaded excitation signals brought by high feedback gain augmentation in lateral-directional aerodynamic parameters identification of fly-by-wire（FBW） passenger airliners. Taking for example an FBW passenger airliner model with directional relaxed-static-stability, through analysis of its signal energy distribution and airframe frequency response, a new method is proposed for signal type selection, signal parameters design, and the appropriate frequency relationship between the aileron and rudder excitation signals. A simulation validation is presented of the FBW passenger airliner＇s lateral-directional aerodynamic parameters identification. The validation result demonstrates that the designed signal can excite the lateral-directional motion mode of the FBW passenger airliner adequately and persistently. Meanwhile, the relative errors of aerodynamic parameters are less than 5%.

关键词： Excitation signal design Flight test Fly-by-wire (FBW)passenger airliner High feedback gain augmentation Identification Lateral-directional aerodynamic parameter

Flight strategy optimization for high-altitude long-endurance solar-powered aircraft based on Gauss pseudo-spectral method

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Chinese Journal of aeronautics 2019年第10期32卷 2286-2298页

作者： Shaoqi WANG Dongli MA Muqing YANG Liang ZHANG Guanxiong LI school of aeronautic science and engineering Beihang University

Solar-powered aircraft have attracted great attention owing to their potential for longendurance flight and wide application *** to the particularity of energy system,flight strategy optimization is a significant way to enhance the flight performance for solar-powered *** this study,a flight strategy optimization model for high-altitude long-endurance solar-powered aircraft was *** model consists of three-dimensional kinematic model,aerodynamic model,energy collection model,energy store model and energy loss *** solve the nonlinear optimal control problem with process constraints and terminal constraints,Gauss pseudo-spectral method was employed to discretize the state equations and constraint *** a typical mission flying from given initial point to given final point within a time interval was *** indicate that proper changes of the attitude angle contribute to increasing the energy gained by photovoltaic *** of gravitational potential energy can partly take the role of battery *** these two measures,the optimized flight strategy can improve the final state of charge compared with current constant-altitude constant-velocity *** optimized strategy brings more profits on condition of lower sunlight intensity and shorter daytime.

关键词： Battery pack Flight strategy optimization Gauss pseudo-spectral method Photovoltaic cell Solar-powered aircraft

Change rules of a stratospheric airship's envelope shape during ascent process

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Chinese Journal of aeronautics 2017年第2期30卷 752-758页

作者： Zhao Shuai Liu Dongxu Zhao Da Wu Gang Yin Shi Zhou Pan school of aeronautic science and engineering Beihang University

Stratospheric airship is a special near-space air vehicle,and has more advantages than other air vehicles,such as long endurance,strong survival ability,excellent resolution,low cost,and so on,which make it an ideal stratospheric *** is of great significance to choose a reasonable and effective way to launch a stratospheric airship to the space for both academic research and engineering *** this paper,the non-forming launch way is studied and the method of differential pressure gradient is used to study the change rules of the airship＇s envelope shape during the ascent *** simulation results show that the head of the envelope will maintain the inflatable shape and the envelope under the zero-pressure level will be compressed into a wide range of wrinkles during the ascent *** airship＇s envelope will expand with the ascent of the airship and the position of the zero-pressure level will move downward *** the same time,the envelope will gradually form a certain degree of stiffness under the action of the inner and external differential *** experimental results agree well with the analytical results,which shows that the non-forming launch way is effective and reliable,and the analytical method has exactness and feasibility.

关键词： Non-forming launch Pressure gradient Stratospheric airship Wrinkles Zero-pressure level

LCP method for a planar passive dynamic walker based on an event-driven scheme

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Acta Mechanica Sinica 2018年第3期34卷 578-588页

作者： Xu-Dong Zheng Qi Wang school of aeronautic science and engineering Beihang University

The main purpose of this paper is to present a linear complementarity problem （LCP） method for a planar passive dynamic walker with round feet based on an event-driven scheme. The passive dynamic walker is treated as a planar multi-rigid-body system. The dynamic equations of the passive dynamic walker are obtained by using Lagrange＇s equations of the second kind. The normal forces and frictional forces acting on the feet of the passive walker are described based on a modified Hertz contact model and Coulomb＇s law of dry friction. The state transition problem of stick-slip between feet and floor is formulated as an LCR which is solved with an event-driven scheme. Finally, to validate the methodology, four gaits of the walker are simulated： the stance leg neither slips nor bounces; the stance leg slips without bouncing; the stance leg bounces without slipping; the walker stands after walking several steps.

关键词： Passive dynamic walker Non-smooth dynamics Dry friction Linear complementarity problem Stick-slip

Digital virtual flight testing and evaluation method for flight characteristics airworthiness compliance of civil aircraft based on HQRM

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Chinese Journal of aeronautics 2015年第1期28卷 112-120页

作者： Liu Fan Wang Lixin Tan Xiangsheng school of aeronautic science and engineering Beihang University

In order to incorporate airworthiness requirements for flight characteristics into the entire development cycle of electronic flight control system（EFCS） equipped civil aircraft, digital virtual flight testing and evaluation method based on handling qualities rating method（HQRM）is proposed. First, according to HQRM, flight characteristics airworthiness requirements of civil aircraft in EFCS failure states are determined. On this basis, digital virtual flight testing model,comprising flight task digitized model, pilot controlling model, aircraft motion and atmospheric turbulence model, is used to simulate the realistic process of a pilot controlling an airplane to perform assigned flight tasks. According to the simulation results, flight characteristics airworthiness compliance of the airplane can be evaluated relying on the relevant regulations for handling qualities（HQ） rating. Finally, this method is applied to a type of passenger airplane in a typical EFCS failure state, and preliminary conclusions concerning airworthiness compliance are derived quickly. The research results of this manuscript can provide important theoretical reference for EFCS design and actual airworthiness compliance verification of civil aircraft.

关键词： civil aircraft compliance preliminary verification pilot turbulence realistic passenger concerning

Modeling and experimental investigation of drilling into lunar soils

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Applied Mathematics and Mechanics(English Edition) 2019年第1期40卷 153-166页

作者： Tao CHEN Zhen ZHAO Qi WANG Qingyun WANG school of aeronautic science and engineering Beihang University

Dry drilling only with the assistance of an auger is a reliable and realistic approach to remove abundant soils from the side of a bit in the harsh, dry conditions on the Moon. Based on an elementary analysis, using Janssen's model to reflect the coupling effect among the different components of the stress, the present paper models the conveying dynamics along the helical groove and the sampling mechanism in the centering hole of the stem for an auger drilling into lunar soil simulant. Combining the two parts as well as a simple cutting model for the bit, a whole drilling model is established to investigate the complicated relation among the conveying ability of the auger, the coring rate, and drilling parameters such as the penetration and rotation speeds. The relation is revealed by the complicated transition between different sub-models with the help of the physical transition conditions. A series of experiments with constant penetration and rotation speeds are conducted to verify the model. Three aspects of characteristics of the drilling dynamics are manifested,(i) the loads on the bit are almost independent of penetration;(ii) three obvious drilling stages with respect to cut per revolution are grouped;(iii) a linear relationship is found between the coring rate and the revolution per penetration.

关键词： coring drill helical groove conveyance mechanism sampling mechanism

Fatigue behavior of direct laser deposited Ti-6.5Al-2Zr-1Mo-1V titanium alloy and its life distribution model

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Chinese Journal of aeronautics 2018年第11期31卷 2124-2135页

作者： Xiaofan HE Tianshuai WANG Xiaobo WANG Weigang ZHAN Yuhai LI school of aeronautic science and engineering Beihang University

The present work aims to investigate the fatigue behavior of Direct Laser Deposition(DLD) Ti-6.5 Al-2 Zr-1 Mo-1 V titanium alloy under constant amplitude stress. 22 pieces of DLD Ti-6.5 Al-2 Zr-1 Mo-1 V titanium alloy standard cylinder specimens were tested under a stress level of 800 MPa with a stress ratio of 0.06. Fatigue fractography and fatigue life data were *** the fracture surface analysis, the specimens were divided into two categories in accordance with the location of crack initiation and defect types. Comparison of fatigue life and behavior between two specimen types was given, which was followed by a discussion about the impact of defect type, size and position on the fatigue life of the specimen. The fatigue test results also show a large variation of fatigue life. To illustrate the statistical characteristics of the fatigue life, probabilistic analysis was performed, and a novel bimodal lognormal model was established. The model has a good fit with the experimental data and can reduce the scatter of the fatigue life significantly.

关键词： Additive Manufacturing Bimodal Lognormal distribution Direct Laser Deposition Fatigue life Mixed failure behavior

Numerical investigation on jet interaction with a compression ramp

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Chinese Journal of aeronautics 2013年第4期26卷 898-908页

作者： Zhen Huaping Gao Zhenxun Lee Chunhian school of aeronautic science and engineering Beihang University

A numerical investigation on jet interaction in supersonic laminar flow with a compres- sion ramp is performed utilizing the AUSMDV scheme and a parallel solver. Several parameters dominating the interference flowfield are studied after defining the relative increment of normal force and the jet amplification factor as the evaluation criterion of jet control performance. The computational results show that most features of the interaction flowfield between the transverse jet and the ramp are similar to those between a jet and a flat plate, except that the flow structures are more complicated and the low-pressure region behind the jet is less extensive. The relative force increment and the jet amplification factor both increase with the distance between the jet and the ramp shortening till quintuple jet diameters. Inconspicuous difference is observed between the jet-before-ramp and jet-on-ramp cases. The variation of the injection angle changes the extent of the separation region, the plateau pressure, and the peak pressure near the jet. In the present computational conditions, 120 is indicated relatively optimal among all the injection angles studied. For cold gas simulations, although little influence of the jet temperature on the pressure distribution near the jet is observed under the computation model and the flow parameters studied, reducing jet temperature somehow benefits the improvement of the normal force and the jet efficiency. When the pressure ratio of jet to freestream is fixed, the relative force increment varies little when increasing the freestream Mach number, while the jet amplification factor increases.

关键词： Air pressure Amplification factor Computational aerodynam- ics Navier-Stokes equations Pitch control Transverse jet

An experimental investigation on static directiona stability

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Chinese Journal of aeronautics 2016年第6期29卷 1527-1540页

作者： Wen Jing Wang Yankui Deng Xueying school of aeronautic science and engineering Beihang University

A generic aircraft usually loses its static directional stability at moderate angle of attack(typically 20–30°). In this research, wind tunnel studies were performed using an aircraft model with moderate swept wing and a conventional vertical tail. The purpose of this study was to investigate flow mechanisms responsible for static directional stability. Measurements of force, surface pressure and spatial flow field were carried out for angles of attack from 0° to 46° and sideslip angles from-8° to 8°. Results of the wind tunnel experiments show that the vertical tail is the main contributor to static directional stability, while the fuselage is the main contributor to static directional instability of the model. In the sideslip attitude for moderate angles of attack, the fuselage vortex and the wing vortex merged together and changed asymmetrically as angle of attack increased on the windward side and leeward side of the vertical tail. The separated asymmetrical vortex flow around the vertical tail is the main reason for reduction in the static directional stability. Compared with the wing vortices, the fuselage vortices are more concentrated and closer to the vertical tail, so the yawing moment of vertical tail is more unstable than that when the wings are absent. On the other hand,the attached asymmetrical flow over the fuselage in sideslip leads to the static directional instability of the fuselage being exacerbated. It is mainly due to the predominant model contour blockage effect on the windward side flow over the model in sideslip, which is strongly affected by angle of attack.

关键词： Asymmetric flow Directional stability Flow mechanisms Sideslip Yawing moment