某型电动飞机螺旋桨振动特性实验研究

某型电动飞机采用螺旋桨产生拉力,为了防止螺旋桨工作时共振,利用ES-2-150振动实验系统进行了两叶木质螺旋桨和碳纤维螺旋桨的振动特性实验,采用谐振搜索与驻留方法测量出木质螺旋桨的第一阶固有频率为36.07Hz,碳纤维螺旋桨的第一阶固有频率为73.58Hz。螺旋桨爬升状态转频为39Hz,这与木质螺旋桨的第一阶固有频率非常接近,导致木质螺旋桨在爬升状态出现比较严重的振动故障。因此,某型电动飞机最终选择两叶碳纤维螺旋桨作为其拉力产生装置。     

Aeroelastic analysis of swept pre-twisted wings

In this paper, aeroelastic modeling of aircraft wings with variations in sweep angle, taper ratio, and variable pre-twist angle along the span is considered. The wing structure is modeled as a classical beam with torsion and bending flexibility. The governing equations are derived based on Hamilton’s principle. Moreover, Peters’ finite state aerodynamic model which is modified to take into account the effects of the wing finite-span, the wing sweep angle, and the wing pre-twist angle, is used to simulate the aerodynamic loads on the wing. The coupled partially differential equations are discretized to a set of ordinary differential equations using Galerkin’s approach. By solving these equations the aeroelastic instability conditions are derived. The results are compared with some experimental and analytical results of previous published papers and good agreement is attained. Effects of the wing sweep angle, taper ratio, bending to torsional rigidity, and pre-twist angle on the flutter boundary in several cases are studied. Results show that these geometrical and physical parameters have considerable effects on the wing flutter boundary.     

DYNAMIC MODELING AND STABILITY CONTROL OF FOLDING WING AIRCRAFT 1)

折叠翼飞行器在变形过程中,其动力学模型呈现多刚体、多自由度和强非线性特点,同时气动力/力矩、压心、质心和转动惯量等参数也会大幅度变化,严重影响飞行稳定性. 由此,本论文将对飞行器的多刚体动力学建模与变形稳定控制进行研究.基于凯恩方法建立了折叠翼飞行器的多刚体动力学模型,并从中得到了变形所产生的附加力和力矩表达式.通过气动计算拟合出气动参数与折叠角之间的函数关系,由此分析了不同折叠角速度下飞行器的纵向动态特性, 结果表明,折叠翼飞行器变形过程中速度、高度和俯仰角均会发生变化,飞行器无法保持稳定飞行.为此提出了一种基于自抗扰理论的飞行器变形过程中的稳定控制方法.将折叠翼飞行器纵向非线性动力学模型中存在的非线性项、耦合项以及参数时变项都视为系统内外总扰动,利用扩张状态观测器对总扰动进行实时估计和补偿, 针对补偿后的系统设计PD控制器,实现了速度通道和高度通道的解耦控制.通过Lyapunov稳定性原理证明了系统的稳定性, 并进行数学仿真验证. 仿真结果表明,基于自抗扰理论设计的稳定控制器能够解决飞行器变形所带来的强非线性和参数时变等问题,保证飞行器的高精度稳定控制.     

Theory of Disappearance of the Electric Signal Induced by an Aircraft Jet Engine in the Afterburner Regime

Electrical aspects of aircraft jet engine operation are considered. A phenomenon previously observed experimentally, namely, the disappearance of the engine current and alternating electric signal induced by the engine jet in the afterburner regime, is explained. It is shown that this phenomenon results from the detachment of electrons from negative ions when the gas temperature in the afterburner increases. This leads to an increase in the effective conductivity of the gas. As a result, the engine current circuit is closed on the internal duct walls and engine charging becomes insignificant.A physico-mathematical model of the electrical processes in the afterburner is formulated and model problems are solved.     

基于3G-ASCX的小型飞行器异常导航信号检测系统设计

传统方法在异常导航信号信噪比较低时对小型飞行器异常导航信号的检测效果不理想。设计并实现了一种基于3G-ASCX的小型飞行器异常导航信号检测系统,硬件设计时着重于ASCX传感器模块、异常导航信号检测模块、主控基站模块、3G/GPRS传输模块的研究,3G/GPRS传输模块的硬件设计中,通过功耗低体积小的CC1100完成异常导航信号的收发,传输过程中通过芯片STC12C5410AD完成电容的平衡转换,选取了MC3486进行电压的转换,最终实现异常信号数据的安全快速传输;软件设计中,系统软件流程设计及异常导航信号检测模块软件设计,最后进行仿真实验,实验结果证明,相比传统系统,所设计系统检测到的小型飞行器异常导航信号同实际测量的异常导航信号具有较高的匹配度,与实际值相比,误差小于1dB,适合推广使用。     

基于Flowmaster的飞机燃油供油系统仿真研究

飞机燃油系统作为飞机不可或缺的功能和保障系统,对飞机的安全性有着重大的影响。针对飞机燃油供油系统的故障诊断问题,利用流体仿真软件Flowmaster建立了供油系统模型。仿真了飞机燃油系统增压泵供油、交输供油、重力供油的工作情况。分析了飞机燃油供油系统的故障模式,仿真了在几种典型故障模型下的工作情况,并对仿真结果进行了分析。结果表明利用Flowmaster所建立的供油系统模型能有效地仿真飞机燃油系统正常与故障工作情况,为飞机燃油系统的故障诊断打下了基础。     

基于敏度阈值拓扑优化方法在飞机加强框设计中的应用

为了能够有效地降低飞机结构承力件的重量，针对飞机骨架，以加强框的概念设计为研究内容，通过对“敏度阈值”概念的分析，指出其不足，提出了“改进的敏度阈值”概念，并与“约束补偿”策略结合而形成新的拓扑优化算法，用于加强框的材料布局设计．多个算例中的拓扑优化结果均显示其结构型式十分新颖，值得深入地探讨．     

飞机－道面－土基动力耦合系统有限元分析

本文将飞机－道面－土基作为一个相互作用的动力系统，对飞机滑行情况下，弹性半空间地基上刚性道面板的动响应，采用有限元法进行了计算分析。结果表明，本文计算结果与现场实测值吻合很好。由于考虑了飞机和道面之间的耦合作用，避免了实测飞机对道面作用荷载的繁琐工作，因此本文方法具有明显的实用意义。     

NONLINEAR DYNAMICS OF A CRACKED ROTOR IN A MANEUVERING AIRCRAFT

The nonlinear dynamics of a cracked rotor system in an aircraft maneuvering with constant velocity or acceleration was investigated, The influence of the aircraft climbing angle on the cracked rotor system response is of particular interest and the results show that the climbing angle can markedly affect the parameter range for bifurcation, for quasiperiodic response and for chaotic response as well as for system stability. Aircraft acceleration is also shown to significantly affect the nonlinear behavior of the cracked rotor system, illustrating the possibility for on-line rotor crack fault diagnosis.