某型无人机滑跑起降纠偏控制改进分析

地面滑跑起降是轮式无人机飞行过程中的一个重要阶段,研究地面滑跑起降阶段的动力学特性对于无人机抗侧风特性摸底和纠偏控制律设计优化具有重要意义。基于轮胎侧向力模型、弹性轮胎和刚性机体假设,在 Matlab 平台建立地面滑跑阶段全量非线性模型和纠偏控制模型,综合分析发动机扭矩与侧风等工况下滑跑起飞和着陆过程中的响应特性,并对比分析两种不同纠偏控制模型下的纠偏性能和抗侧风特性。结果表明：该仿真模型能够反映无人机滑跑起降阶段的动力学特性,改进后的纠偏控制模型能够大幅缩短滑跑起飞距离,并且可以较好地实现纠偏控制。     

飞机地面转弯和刹车响应动力学分析

 建立了飞机地面运动的数学模型,模型中考虑机体的六自由度运动和起落架弹性;基于滑移率控制方式建立了机轮防滑刹车模型。通过仿真得出了飞机地面匀速转弯和滑跑刹车的动态响应。其结果表明,飞机匀速转弯时,其峰值出现在初始非稳态时刻;弹性起落架在着陆和刹车过程中产生走步现象;采用滑移率控制方式使飞机在整个刹车过程中取得最佳刹车性能。     

起落架四点布局无人机地面运动研究

以起落架四点布局无人机为研究对象,在考虑摩擦力、侧向力和角速率等各种因素的情况下,全面分析研究了四轮无人机地面滑跑时的运动特点和受力情况,建立了四轮无人机地面运动的动力学方程和运动学方程。在此基础上,对全量非线性模型进行了起飞、着陆时地面滑跑情况的仿真,仿真结果表明了系统模型的正确性。     

舰载无人机横侧向着舰控制律设计

舰载无人机横侧向控制一直是着舰控制律设计的难点。为了解决着舰横侧向控制的难题,针对舰载无人机的非线性模型采用了反演控制器设计方法,为解决传统反演的计算膨胀问题,引入了指令滤波方法,同时只设计了一个Lyapunov函数证明了稳定性;由于舰载机动力学模型不能精确获得,采用了自适应方法对其进行估计。设计的横侧向着舰控制器,能较好地解决横侧向控制器设计过程中的耦合问题,并且和传统PID进行了仿真对比,证明了所设计的控制律满足了对参考信号跟踪的性能要求。     

Unmanned aerial vehicle strike on a flat plate: Tests and numerical simulations

The incursion of Unmanned Aerial Vehicles (UAVs) into airports often occurs due to the popularity of drones, which may lead to a threat to aircraft flight safety. Therefore, estimating the dynamic impact load caused by drone strikes is essential. This paper proposes a test method with high precision and low cost involving launching of a UAV to impact a flat plate specimen by using an air gun. The test results of UAVs impacting flat plates at different impact velocities, such as the UAV damage deformation captured by a high-speed camera and strain vs time dynamic response curves of plates, were obtained and analysed. At the same time, a corresponding numerical simulation was carried out by using the explicit finite element software LS-DYNA. The predicted damage to the UAV and strain on the flat plate during the strike process were compared with the test results. The overall trend of the simulation results is in good agreement with the test results, at least for the first three milliseconds of the event. This shows that the numerical simulation model established in this paper is reasonable. The UAV numerical method established in the present paper can be used to carry out numerical simulations and evaluations of the collision safety of UAVs against large aircraft and high-value ground targets. The results show that the local deformation of the impacted target is uneven due to the distribution of concentrated mass components such as motors, battery, and camera. As the impact velocity of the UAV increases, all parts of the UAV are seriously damaged and basically in a fragmented state, and the battery is greatly deformed. The interaction between the UAV and the flat plate specimen is approximately 2.7 ms, and the UAV numerical simulation model established in this paper can well simulate the real UAV impact process.     

某型联翼布局无人机的气动计算与分析

与常规布局飞机相比,联翼布局飞机具有结构重量轻、抗弯扭强度大、诱导阻力低、升力系数大和稳定性好等优点。介绍一种高效的数值模拟方法,完成对某型联翼布局无人机气动特性的初步计算与分析。基于商业软件ANSYS,整个研究过程着重于从网格建模、全机流场模拟、气动模拟数据分析三个方面,探索该型无人机纵向、横向和航向的气动特性以及主操纵面的操纵效率,实现对该型无人机稳定性和操纵性能的表征与评估。结果表明:无人机升降舵偏角的变化不影响无人机的握杆静稳定度,并且在0°~25°的升降舵偏角(下偏)范围内,升降舵偏角与升降舵的升力系数基本呈线性变化;在-4°~12°的迎角范围内,随着迎角的不断增大,该型无人机的横向静稳定性水平越大;两个垂直翼和垂尾是产生航向静稳定性的主要部件。     

基于神经网络补偿动态逆的飞翼布局无人机姿态控制方法

将动态逆控制技术应用于飞翼式布局无人机的姿态控制回路,以适应飞翼布局无人机控制系统要求。介绍了动态逆控制器解耦控制原理,以及神经网络补偿结构的作用和设计方法,并基于无人机非线性姿态运动学和动力学模型设计了基于神经网络补偿的动态逆控制器。在强耦合、强非线性的飞翼布局无人机模型上,通过数学仿真验证了系统具有良好的动态性能和稳态特性,控制器具有很强的鲁棒性。     

Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

To investigate the longitudinal motion stability of aircraft maneuvers conveniently, a new stability analysis approach is presented in this paper. Based on describing longitudinal aerodynamics at high angle-of-attack (a < 50 ) motion by polynomials, a union structure of two-order differential equation is suggested. By means of nonlinear theory and method, analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight. Applying the theories of bifurcations, many kinds of bifurcations, such as equilibrium, Hopf, homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived. The bifurcation curves divide the parameter plane into several regions; moreover, the complete bifurcation diagrams and phase portraits in different regions are obtained. Finally, our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium. The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.     

飞行器自激振荡的流动物理与动力学机制

全局亚迭代耦合求解流体动力学方程和刚体动力学方程,研究轴对称飞行器单自由度俯仰失稳运动的非定常特征.高超音速锥-柱-裙飞行器的单自由度俯仰失稳运动发展为极限环形式,周期性运动伴随着波系结构的非定常变化;自激振荡源于静稳定构型的振动回复机制和尾裙激波流动迟滞效应所构成的阻尼机制.基于第二拉格朗日方程和虚功原理,导出能够描述迟滞现象的参数化非线性动力学模型.多尺度近似分析获得参数化运动特征:自激振动过程是拟简谐运动;静稳定构型才能出现自激振荡周期运动;平衡点阻尼是决定运动稳定特性的分叉参数;振幅特性与阻尼非线性相关,频率特性与刚度非线性相关.基于数值结果的参数辨识,非线性模型的理论分析、重构都与数值结果高度一致,从而有效地佐证了自激振荡建模研究的合理性.     

起落架四点布局无人机地面运动研究

以国内某四轮无人机为研究对象,在考虑摩擦力、侧向力和角速率等各种因素的情况下,全面分析研究了四轮无人机地面滑跑时的运动特点和受力情况,建立了六自由度刚体飞行器地面运动的动力学方程和运动学方程。在此基础上,对全量非线性模型进行了起飞、着陆时地面运动的仿真,该仿真结果表明了系统模型的正确性。     

基于EBA-FLC的飞机急滚机动分支分析与控制

结合扩展分支分析(EBA)和模糊逻辑控制(FLC),提出了一种新的闭环分支控制方法,即EBA-FLC方法,并将其应用于某机动飞机的无侧滑滚转机动研究。揭示了飞机全局非线性动力学特性,实现了无侧滑滚转机动的闭环分支控制,使飞机在大范围内具有期望的动力学特性,改善了飞机无侧滑滚转机动的动态和稳态特性。     

高超声速飞行器纵向大攻角非线性失稳分析与控制

针对滑翔式高超声速飞行器大攻角纵向失稳问题,基于连续算法和分岔理论,求解并分析了多特征点单参数分岔图,对平衡分支的稳定性和突变点进行了分析。结合高超声速飞行器大包线飞行特性,求解并分析了双参数分岔,并计算了稳定分支曲面和不稳定分支曲面,从全包线范围揭示了高超声速飞行器大攻角失稳特性。为了实现高超声速飞行器的稳定控制,基于非线性动态逆和分阶思想,设计了非线性控制器,并计算了非线性开环闭环系统的全局特征根分布,结合所提出的一种基于连续算法的非线性闭环系统全局性能评估方法,评估并分析得出非线性控制器的有效性和较优的全局性能。最后,对闭环系统进行了时间历程仿真,进一步验证了非线性控制器的有效性。     

不同类型的翼梢小翼在无人机设计中的应用

针对某型无人机进行融合式、双叉弯刀式2种不同形式翼梢小翼设计,对6组不同参数的小翼构型进行了基于RNAS控制方程的数值模拟计算,结果表明,双叉弯刀式小翼在气动效率的提高、横航向稳定性影响方面明显优于融合式翼梢小翼。结合数值模拟计算结果,从气动机理上对加装翼梢小翼后的纵向、横航向特性影响进行了分析,得出了2种不同形式小翼的气动特点及其各参数对气动性能的影响,其结论对中小型无人机翼梢小翼的设计提供了一定的参考依据。     

无人机空中加油自主会合的制导与控制

针对无人机空中加油的自主会合问题,进行了相应制导律和非线性控制器的设计。通过改进的带角度约束的三维比例制导律实现对航向角的控制,以协调转弯的方式将航迹角指令转化为姿态角指令。基于无人机六自由度的动力学模型,针对无人机的姿态控制,采用时标分离的方法设计了慢子系统和快子系统,并对这两个子系统分别进行动态逆控制设计。同时,基于滑模控制的方法设计了满足自主会合要求的速度控制律。在保证无人机飞行稳定的基础上,实现了对控制和制导指令的精确跟踪。仿真结果表明,所设计的制导律和控制律能够实现无人机空中加油的自主会合,具有良好的动态特性。     

考虑减摆器非线性特性的前起落架摆振分析

飞机的前起落架摆振通常在飞机起飞或降落滑跑的过程中发生，对飞机的稳定性和操纵性产生危害，是一种严重的飞机故障。针对某型号无人机，基于动量矩定理，建立考虑起落架侧弯、扭转的摆振数学模型，讨论使用传统油液阻尼减摆器和电磁阻尼减摆器时不同的动力学模型。对于传统油液阻尼减摆器，采用等效线性模型，得到摆振临界稳定阻尼曲线的上下边界；而对于电磁阻尼减摆器的非线性模型，使用分岔分析理论确定系统的摆振稳定区域。结果表明：过大的减摆阻尼对摆振无法起到抑制的作用，得到控制参数平面上摆振的稳定区域，可为后续的起落架减摆设计提供参考。     

基于能量的电磁轴承系统建模及控制方法研究

通过介绍电磁轴承的基本组成,针对电磁轴承系统中的大范围稳定问题,在考虑线圈电感的非线性的情况下,从能量的角度对系统进行了非线性建模。并在构建李雅普诺夫函数及理论分析的基础上提出了基于能量的控制器方法。与传统的PID控制进行仿真对比后,得到了一组可使电磁轴承大范围稳定的参数范围。结果表明,这种方法为非线性控制提供了设计基础,在获得满意的动态响应方面是可行的。     

弹性飞翼无人机鲁棒姿态控制设计

针对大展弦比飞翼布局无人机的刚体运动与弹性运动耦合动力学模型,提出了一种基于反步法的鲁棒非线性控制方法。该方法考虑了飞翼无人机的非线性因素,将动态面反步控制作为内环控制抵消系统的非线性因素;同时考虑系统实际存在的弹性耦合项、参数不确定项以及外部扰动,将内环反步控制与飞翼无人机模型整体作为新的被控对象,引入最优化理论对新的被控对象设计了外环鲁棒控制器。仿真结果表明,所提出的控制器不仅满足飞翼无人机姿态跟踪性能的要求,且对模型不确定性和气动弹性影响具有鲁棒性。     

Full mode flight dynamics modelling and control of stopped-rotor UAV

The Stopped-Rotor (SR) UAV combines the advantages of vertical take-off and landing of helicopter and high-speed cruise of fixed-wing aircraft. At the same time, it also has a unique aerodynamic layout, which leads to great differences in the control and aerodynamic characteristics of various flight modes, and brings great challenges to the flight dynamics modelling and control in full-mode flight. In this paper, the flight dynamics modelling and control method of SR UAV in full-mode flight is studied. First, based on the typical flight profile of SR UAV when performing missions, using the theory and method of fuzzy mathematics, the T-S flight dynamics model of SR UAV in full-mode flight is established by synthesizing the flight dynamics model of each flight mode. Then, an explicit model tracking and parameter adjusting control system based on fuzzy theory is designed to enhance the stability of the inner loop of SR UAV in full-mode flight, which effectively reduces the coupling between axes and improves the control quality of the system. Finally, the outer loop control system is designed by using classical control method, and the control law of SR UAV in full-mode automatic flight is obtained. The simulation results show that the proposed control system design method is feasible and effective, which lays a solid foundation for the subsequent engineering implementation of the SR UAV.     

基于结构动网格的无人机地面效应研究

为了更好地分析地面效应对无人机气动特性的影响,采用一种新的结构动网格生成技术,运用CFD手段对某无人机的地面效应进行了研究。在一套静态网格CFD计算基础上,运用结构动网格生成技术,获得非定常的网格移动,得到一系列的不同攻角、地面效应高度的CFD网格及初始流场。在此基础上进行定常流场求解,计算得到地面效应的定常CFD结果。最后对某双尾撑布局无人机的地面效应进行了CFD计算研究,对相应的全机气动特性的影响进行了分析。计算结果表明：地面效应对平尾的影响大于对机翼的影响并使平尾的失速迎角提前;该方法是可行的,具有一定的工程应用价值。     

A study of instability in a miniature flying-wing aircraft in high-speed taxi

This study investigates an instability that was observed during high-speed taxi tests of an experimental flying-wing aircraft.In order to resolve the reason of instability and probable solution of it,the instability was reproduced in simulations.An analysis revealed the unique stability characteristics of this aircraft.This aircraft has a rigid connection between the nose wheel steering mechanism and an electric servo,which is different from aircraft with a conventional tricycle landing gear system.The analysis based on simulation results suggests that there are two reasons for the instability.The first reason is a reversal of the lateral velocity of the nose wheel.The second reason is that the moment about the center of gravity created by the lateral friction force from the nose wheel is larger than that from the lateral friction force from the main wheels.These problems were corrected by changing the ground pitch angle.Simulations show that reducing the ground pitch angle can eliminate the instability in high-speed taxi.