Optimization of airplane wing structures under landing loads

A methodology is presented for the optimum design of aircraft wing structures subjected to landing loads. The stresses developed in the wing during landing are computed by considering the interaction between the landing gear and the flexible airplane structure. The landing gear is assumed to have nonlinear characteristics typical of conventional gears, namely, velocity squared damping, polytropic air-compression springing and exponential tire force-deflection characteristics. The coupled nonlinear differential equations of motion that arise in the landing analysis are solved by using a step-by-step numerical integration technique. In order to find the behavior of the wing structure under landing loads and also to obtain a physical insight into the nature of the optimum solution, the design of the typical section (symmetric double-wedge airfoil) is studied by using a graphical procedure. Then a more realistic wing optimization problem is formulated as a constrained nonlinear programming problem based on finite element modeling. The optimum solutions are found by using the interior penalty function method. A sensitivity analysis is conducted to find the effect of changes in design variables about the optimum point on the various response parameters on the wing structure.     

Optimization of airplane wing structures under taxiing loads

A methodology is presented for the optimum design of aircraft wing structures subjected to taxiing loads. The dynamic stresses induced in the wing as the airplane accelerates or decelerates on the runway during take-off or landing are computed by considering the interaction between the landing gear and the flexible airplane structure. The procedure is capable of taking into account both the effects of discrete runway bumps and the effects of runway unevenness. A numerical step-by-step method is developed for solving the nonlinear differential equations of motion. The optimization methodology is illustrated with two examples. The first example deals with the design of the typical section (symmetric double wedge airfoil). This example is studied by using a graphical procedure mainly to understand qualitatively the behavior of wing structures under taxiing loads and also to obtain a physical insight into the nature of the optimum solution. The second example is concerned with the design of a more realistic wing structure. In this case, the problem is formulated and solved as a constrained nonlinear programming problem based on finite element modeling.     

Automated optimum design of wing structures: A probabilistic approach

The optimization of aircraft wing structures is presented by considering the dynamic stresses developed during landing impact and gust load conditions. The random nature of the sinking speed and the forward velocity at the instant of contact is considered in the calculation of landing stresses. The vertical velocity due to gust is treated as a stochastic process for the computation of gust-induced stresses. The optimum designs of a symmetric double wedge airfoil, based on beam type of analysis, and a supersonic airplane wing, based on finite element analysis, are considered to illustrate the procedure. A graphical procedure is used in the case of the double wedge airfoil, and nonlinear programming techniques are used in the case of the supersonic wing, for finding the optimum solutions.     

Design of aircraft wings subjected to gust loads: A system reliability approach

A method for system reliability-based design of aircraft wing structures is presented. A wing of a light commuter aircraft designed for gust loads according to the FAA regulations is compared with one designed by system reliability optimization. It is shown that system reliability optimization has the potential of improving dramatically the safety and efficiency of new designs. The reasons for the differences between the deterministic and reliability-based designs are explained.     

Optimization of airplane wing structures under gust loads

A methodology is presented for the optimum design of aircraft wing structures subjected to gust loads. The equations of motion, in the form of coupled integro-differential equations, are solved numerically and the stresses in the aircraft wing structure are found for a discrete gust encounter. The gust is assumed to be one minus cosine type and uniform along the span of the wing. In order to find the behavior of the wing structure under gust loads and also to obtain a physical insight into the nature of the optimum solution, the design of the typical section (symmetric double wedge airfoil) is studied by using a graphical procedure. Then a more realistic wing optimization problem is formulated as a constrained nonlinear programming problem based on finite element modeling and the optimum solution is found by using the interior penalty function method. A sensitivity analysis is conducted to find the effects of changes in design variables about the optimum point on the response quantities of the wing structure.     

舰载机起落架缓冲性能设计优化

为提高舰载机起落架的缓冲性能,采用多体系统仿真和多目标参数优化协同仿真分析相结合的方法,以iSIGHT为设计和仿真平台,在优化参数的同时调用多体系统仿真软件进行仿真分析.对前起落架缓冲系统进行受力分析,用MSC Adams/Aircraft建立某型舰载机起落架落震功能虚拟样机,实现可循环迭代求解落震质量的优化;考虑舰载...     

Intelligent automatic landing system using time delay neural network controller

This paper presents an intelligent automatic landing system that uses a time delay neural network controller and a linearized inverse aircraft model to improve the performance of conventional automatic landing systems. The automatic landing system of an airplane is enabled only under limited conditions. If severe wind disturbances are encountered, the pilot must handle the aircraft due to the limits of the automatic landing system. In this study, a learning-through-time process is used in the controller training. Simulation results show that the neural network controller can act as an experienced pilot and guide the aircraft to a safe landing in severe wind disturbance environments without using the gain scheduling technique.     

基于优化配平的机翼故障飞机飞行性能分析

分析飞机机翼故障对飞行性能的影响,对飞机故障后能够安全着陆或返航有着重要意义,飞机的机翼作为产生力和力矩的主要部件对飞行性能起着重要的作用。提出一种基于单纯形优化的机翼故障飞机飞行性能分析方法,建立机翼故障参数模型,根据飞机爬升转弯飞行条件进行优化配平计算,得到在不同状态下不同机翼故障的配平数据库,分析了故障后飞机的飞行性能。仿真结果表明所提算法的有效性。     

作战用固定翼无人机落地姿态平衡控制系统设计

为解决当前控制系统存在对无人机落地高度测量误差大,落地各姿态角度大等问题,设计了作战用固定翼无人机落地姿态平衡控制系统。选用CMOS模拟多路复用器ADG508单芯片,对系统硬件电源电路、AD转换电路、信号采集电路、时钟复位电路、存储扩展电路及调试与接口电路进行优化,通过测量无人机落地姿态,完成系统软件设计,结合硬件与软件部分,实现作战用固定翼无人机落地姿态平衡控制系统的设计。实验结果表明,改进系统对无人机落地高度测量误差小,落地俯仰角、横滚角及偏航角小,具有较好的平衡控制效果,充分满足姿态测量需求。     

飞机结构整体优化和细节分析

飞机结构复杂,部件众多,连接形式复杂,传统的单一计算方法已很难满足计算要求,为更好地挖掘飞机的承载能力,还要考虑结构局部进入塑性区应力分布.对飞机结构进行有限元分析,有时需同时考虑整体和局部,大型结构采用较密的网格会耗费大量时间、资源等,甚至会导致计算不收敛;局部结构须划分较细的网格才能得到局部构件的细节应力.以某型飞机机翼为例,简单介绍开展飞机结构整体优化和细节分析的方法与流程.     

Aircraft morphing wing design by using partial topology optimization

A morphing wing concept has been investigated over the last decade because it can effectively enhance aircraft aerodynamic performance over a wider range of flight conditions through structural flexibility. The internal structural layouts and component sizes of a morphing aircraft wing have an impact on aircraft performance i.e. aeroelastic characteristics, mechanical behaviors, and mass. In this paper, a novel design approach is proposed for synthesizing the internal structural layout of a morphing wing. The new internal structures are achieved by using two new design strategies. The first design strategy applies design variables for simultaneous partial topology and sizing optimization while the second design strategy includes nodal positions as design variables. Both strategies are based on a ground structure approach. A multiobjective optimization problem is assigned to optimize the percentage of change in lift effectiveness, buckling factor, and mass of a structure subject to design constraints including divergence and flutter speeds, buckling factors, and stresses. The design problem is solved by using multiobjective population-based incremental learning (MOPBIL). The Pareto optimum results of both strategies lead to different unconventional wing structures which are superior to their conventional counterparts. From the results, the design strategy that uses simultaneous partial topology, sizing, and shape optimization is superior to the others based on a hypervolume indicator. The aeroelastic parameters of the obtained morphing wing subject to external actuating torques are analyzed and it is shown that it is practicable to apply the unconventional wing structures for an aircraft.     

Gain-scheduled directional guidance controller design using a genetic algorithm for automatic precision landing

This paper discusses the guidance controller design problem of an aircraft in automatic landing and touchdown flight, subject to dangerous and unpredictable gusts known as wind-shear and to directional crosswind. The associated airplane in the landing flight was statically unstable in this paper. The wind-shear, based on the Dryden gust model, was included in the nonlinear airplane model. A directional guidance control system with gain-scheduling fuzzy logic was proposed in this paper. In fuzzy logic, an even number of exponential membership functions in the output are considered and their shape, decay rate, and scaling factors are optimized using a genetic algorithm. In this control system, the glide slope capture logic and the flare logic were also included for longitudinal and lateral control, respectively. The nonlinear aircraft model simulation illustrated that the proposed guidance control system shows satisfactory performances in accurate touchdowns and is adequately robust to the strong crosswind and wind-shear turbulences.     

Reachability Analysis of Landing Sites for Forced Landing of a UAS

This paper details a method to ascertain the reachability of known emergency landing sites for any fixed wing aircraft in a forced landing situation. With a knowledge of the aircraft’s state and parameters, as well as a known wind profile, the area of maximum glide range can be calculated using aircraft equations of motion for gliding flight. A landing descent circuit technique used by human pilots carrying out forced landings called high key low key is employed to account for the extra glide distance required for an approach and landing. By combining maximum glide range analysis with the descent circuit, all the reachable landing sites can be determined. X-Plane flight simulator is used to demonstrate and validate the techniques presented.     

飞机起落架半主动控制仿真研究

该文总结了飞机起落架的三种控制方法：被动控制,主动控制,半主动控制。传统的起落架控制方法不能使飞机很快的达到稳定,为了解决这一问题,该文分析了半主动控制的优点。建立起了半主动控制起落架的数学模型和线性状态控制方程,并根据现代控制理论分析被动控制起落架系统的稳定性和可控性。采用常规状态反馈的控制方法对起落架系统进行设计,得到了半主动控制器。最后通过仿真软件分别对被动控制和半主动控制的起落架模型进行了仿真分析。仿真结果表明：被动控制起落架有较强的振荡,系统稳定时间也较长。而半主动控制起落架能够有效的降低飞机冲击载荷和振动响应,使飞机很快达到稳定。     

Computer-augmented preliminary design of aircraft wing structures

A computer system to aid in the preliminary design of aircraft wing structures for minimum weight is described. The system was developed to utilize effectively the best attributes of both computers and the human mind in the iterative process of analyzing highly redundant trial structures and using these results to select new trial structures with the objective of minimizing weight. The computer is used for the routine data processing, and the designer performs those tasks which require judgement and intuition. Cathode ray tube graphical displays are provided for checking input data and for evaluating results. From given basic information on the wing structure, loads, and material properties, a finite element model is developed, analyzed, modified to eliminate violations of design criteria, and optimized to obtain the structural configuration of least weight. The optimization proceeds automatically, but the designer may monitor progress with the aid of tabular and graphical displays and modify the direction in which the optimization is proceeding. The impetus for this work was provided by a need for such a system in teaching structural design to aeronautical engineering students. The modular system was developed for the Control Data Corporation 6400/6500 computer installation at Purdue University using the Purdue Interactive Remote Access Terminal Environment (PIRATE).     

光电经纬仪补充条件定位方法及其应用

在固定翼飞机定点着陆飞行训练过程中,由于测试装备种类数量较少、测试手段有限或装备故障等因素,经常出现测量记录的数据不能满足飞行讲评和飞行质量评估要求的情况,从固定翼飞机定点着陆飞行训练数据分析入手,根据飞机在下滑道中的运动特点,建立了飞机定点着陆训练下滑道段补充条件定位解算的数学模型,在有效测元不足不能运用常规方法进行定位解算的情况下,提供了定位解算的方法.实测数据计算结果验证了这一方法的正确性和有效性.该方法简单实用,可有效提高光电经纬仪有效信息源的利用效率,在固定翼飞机定点着陆飞行训练中具有十分重要的工程应用价值.     

飞翼布局无人作战飞机自动着陆控制系统设计

飞翼飞机是一种先进的飞行结构.但由于气动外形的特殊,无垂直尾翼的飞翼飞机在着陆阶段,极易受到侧风的干扰,而使其偏离航线;根据飞翼飞机的气动参数,建立了飞翼飞机的非线性数学模型,设计了飞翼无人机的着陆轨迹和控制方案;针对飞翼飞机的特性,采用不同于常规飞机的控制律,设计了抗侧风自动着陆控制系统;设计的控制系统经过非线性仿真试验,结果显示,飞机抗侧风着陆性能达到了设计要求,从而验证了设计方案的可行性.     

飞机拦阻网微机自动立网系统的设计

分析了所研制的飞机拦阻网微机自动立网系统的工作原理、组成和功能;该立网系统是飞机拦阻设备中自动立网的控制部分,能够计算飞机在跑道终端的滑跑速度,在飞机的滑跑速度不符合安全规定的情况下,可以快速、准确地做出判断,产生立网控制信号,立起拦阻网拦截色机,同时发出报警信号;在飞机拦阻网中应用泼自动立网系统能够提高飞机安全着陆的可靠性,有着重要的军事意义和经济效益。     

Automatic Control of Aircraft in Lateral‐Directional Plane During Landing

The paper focuses on the automatic control of aircraft in the lateral‐directional plane during the landing approach phase, taking into account crosswind and sensor errors. Two new automatic landing systems are designed using the H‐inf control, dynamic inversion, optimal observers, and reference models. To validate them, we use the dynamics associated with the landing of a light airplane, we software implement the theoretical results, and analyze the accuracy of the results and the precision standards’ achievement with respect to the requirements of the Federal Aviation Administration for lateral error during the lateral‐directional motion of the aircraft during the landing approach phase.