Investigation of Nonlinear PI Multi-loop Control Strategy for Aircraft HVDC Generator System with Wound Rotor Synchronous Machine

In order to enhance the transient performance of aircraft high voltage DC(HVDC)generation system with wound rotor synchronous machine(WRSM)under a wide speed range,the nonlinear PI multi-loop control strategy is proposed in this paper.Traditional voltage control method is hard to achieve the dynamic performance requirements of the HVDC generation system under a wide speed range,so the nonlinear PI parameter adjustment,load current feedback and speed feedback are added to the voltage and excitation current double loop control.The transfer function of the HVDC generation system is derived,and the relationship between speed,load current and PI parameters is obtained.The PI parameters corresponding to the load at certain speed are used to shorten the adjusting time when the load suddenly changes.The dynamic responses in transient processes are analyzed by experiment.The results illustrate that the WRSM HVDC generator system with this method has better dynamic performance.

Analysis and Research on Aerodynamic Characteristics of Quad Tilt Rotor Aircraft

For the quad tilt rotor aircraft, a computational fluid dynamics method based on multiple reference frames (MRF) was used to analyze the influence of aerodynamic layout parameters on the aerodynamic characteristics of the quad tilt rotor aircraft. Firstly, a numerical simulation method for the interference flow field of the quad tilt rotor aircraft is established. Based on this method, the aerodynamic characteristics of isolated rotors, rotor combinations at different lateral positions on the wing, and rotor rotation directions under different inflow velocities were calculated and analyzed, in order to grasp their aerodynamic interference laws and provide reference for the design and control theory research of such aircraft.

涡轴-涡扇变循环发动机方案及性能匹配设计研究

针对旋转机翼式垂直起降高速巡航飞行器,提出了一种新概念结构形式的涡轴-涡扇变循环(TSFVCE)发动机,能够分别在涡轴和涡扇两种模态工作。首先对涡轴-涡扇变循环发动机的结构及工作模式进行了介绍,并建立基于变比热的部件级性能仿真模型;然后通过循环分析,确定发动机第二涵道比为3,Flade外涵风扇压比为1.98,第一涵道比为0.11,完成发动机设计点性能方案设计;最后分析了核心机驱动风扇(CDFS)可调机构对发动机性能影响机理,得出CDFS放气阀对发动机涡扇模态下的推力与涡轴模态下的功率影响较大,对涡扇模态的推力影响最大为61.5%,对涡轴模态的功率影响最大为33.3%,可利用此特性实现发动机在涡扇和涡轴模态下推力和功率输出的匹配。

基于PIRD-CNN的航空发动机轴承故障诊断方法研究

航空发动机结构与系统的复杂性导致轴承的故障诊断方法通常面临特征提取与模式识别的困难。针对以上不足,考虑实际工程诊断的实时性与准确性,提出了一种新的基于转子位移概率密度信息(probability density information of rotor displacement,PIRD)的航空发动机轴承智能故障诊断方法。其主要对一维卷积神经网络(1-dimensional convolutional neural network,1DCNN)模型进行改进,在传统的卷积层前面增加了PIRD的提取层,可以提取转子振动位移信号的概率密度信息,有效地降低了数据的冗余度,同时保留了故障监测的重要指标。提出的PIRD-CNN诊断模型保留了1DCNN端到端的故障诊断优势,将该模型在航空发动机试验台产生的轴承故障数据进行测试,其对轴承故障诊断精度可达96.58%,与基准研究相对比表明,PIRD-CNN能够快速且更加精准地诊断航空发动机轴承的故障。

Global optimization for ducted coaxial-rotors aircraft based on Kriging model and improved particle swarm optimization algorithm

To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example and Fluent software was applied to the virtual prototype simulations. Through simulation sample points, the total lift of the ducted coaxial-rotors aircraft was obtained. The Kriging model was then constructed, and the function was fitted. Improved particle swarm optimization(PSO) was also utilized for the global optimization of the Kriging model of the ducted coaxial-rotors aircraft for the determination of optimized global coordinates. Finally, the optimized results were simulated by Fluent. The results show that the Kriging model and the improved PSO algorithm significantly improve the lift performance of ducted coaxial-rotors aircraft and computer operational efficiency.

Inverse Model Control for a Quad-rotor Aircraft Using TS-fuzzy Support Vector Regression

An inverse model control based on TS-fuzzy support vector regression( TS-fuzzy SVR) for a quadrotor aircraft is developed. The TS-kernel is the product of linear combination of input and a cluster of output corresponding to a cluster of TS-type fuzzy rules. The output of TS-fuzzy SVR is a linear weighted sum of the TSkernels. The dynamical model of the quad-rotor aircraft is derived. A new control scheme combined with TSfuzzy SVR inverse model control and PID control is presented so that the TS-fuzzy SVR inverse model control enhances capabilities of disturbance rejection and the robustness while the PID control enhances fast responsiveness and reliability of the system. Simulation results show the capabilities of the developed control for the attitude system of quad-rotor aircraft.

Hex-Rotor无人飞行器及其飞行控制系统设计

提出了一种Hex-Rotor无人飞行器以克服现有多旋翼飞行器的欠驱动和强耦合特性对其飞行控制效果的影响,利用6个旋翼独特的结构配置来保证飞行器独立控制空间六自由度的能力。介绍了这种新型飞行器的结构特点并建立其动力学模型,引入滤波反步法与自抗扰算法设计了具有双环并行结构的飞行控制系统,在数字仿真中实现了飞行器的空间六自由度独立控制并克服了未知外部扰动以及模型不确定性带来的影响。结果显示,原型机试飞实验中,飞行器的水平位移跟踪误差不超过±4m,高度误差不超过±3m,姿态角误差不超过±0.05rad,均保持在传感器的测量误差范围内,飞行器较为准确地跟踪了期望指令。仿真和实验结果证明了该新型Hex-Rotor飞行器具有期望的六自由度独立控制能力,建立的数学模型准确,设计的飞行控制系统能够实现轨迹与姿态跟踪飞行。

Autonomous Landing of Small Unmanned Aerial Rotorcraft Based on Monocular Vision in GPS-denied Area

Focusing on the low-precision attitude of a current small unmanned aerial rotorcraft at the landing stage, the present paper proposes a new attitude control method for the GPS-denied scenario based on the monocular vision. Primarily, a robust landmark detection technique is developed which leverages the well-documented merits of supporting vector machines (SVMs) to enable landmark detection. Then an algorithm of nonlinear optimization based on Newton iteration method for the attitude and position of camera is put forward to reduce the projection error and get an optimized solution. By introducing the wavelet analysis into the adaptive Kalman filter, the high frequency noise of vision is filtered out successfully. At last, automatic landing tests are performed to verify the method's feasibility and effectiveness. © 2014 Chinese Association of Automation.

Research on a combinatorial control method for coaxial rotor aircraft based on sliding mode

Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.

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 quasi-periodic 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.

基于改进Event模型的多旋翼型eVTOL垂直间隔安全评估方法

电动垂直起降飞行器(eVTOL)是1种新兴的交通工具,也是近年来研究的热点。受限于垂直定位精度低、穿越飞行风险隐患多等问题,eVTOL运行间隔标准难以确定,尚不具备实际应用条件。为探索该飞行器垂直间隔标准,针对多旋翼型eVTOL的底部较宽、顶部逐渐变细的外形特性,改进了经典Event垂直碰撞模型,并提出了基于改进Event模型的多旋翼型eVTOL垂直间隔安全评估方法。该模型考虑了多旋翼型eVTOL的外形特征、导航精度、运行特点、定位误差、飞行速度特性及速度误差等因素,引入相对速度、侧向重叠概率、垂直重叠概率等计算模型参数,并将原长方体碰撞盒修正为圆台体碰撞盒,有效降低了计算冗余,提高了碰撞模型的精确性。以亿航216-S型多旋翼型eVTOL为例,计算了其在不同安全目标水平和不同导航精度下的最小垂直间隔,计算结果表明:①安全目标水平与导航精度的降低,都会导致最小垂直间隔的减少;②当安全目标水平为1×10^(-6)次/飞行小时且导航精度为RNP10时,最小垂直间隔可缩小至11 m;③当导航精度为RNP10且垂直间隔为11 m时,基于改进Event模型计算的碰撞风险比原模型降低了24.78%。研究结果表明,在计算多旋翼型eVTOL的碰撞风险中,引入圆台体碰撞盒的垂直间隔安全评估方法更加精确合理,能够为多旋翼型eVTOL垂直间隔标准制定提供理论支持。

基于串级模型预测控制的倾转旋翼机过渡段控制

针对倾转旋翼机过渡阶段存在的纵垂向控制通道切换问题,基于串级控制框架提出了一种具有自适应权重矩阵的模型预测控制(model predictive control,MPC)策略。首先,通过分析直升机模态和定翼机模态的控制结构差别,构造了兼容全部飞行模态的增广串级控制结构。然后,在确立了倾转旋翼机的模糊建模策略后,设计了MPC目标函数中权重矩阵的参数自适应变化律,从而使内环和外环中高度、前飞速度的跟踪误差惩罚项根据所处模态的不同有着不同的惩罚占比。这样可以使在过渡阶段设计的增广串级控制结构能始终满足时标分离原则。该控制方案将2个飞行模态和过渡阶段的控制纳入一个统一的控制结构中,实现了各飞行模态间的自由切换。仿真结果表明,所提控制方案有良好的控制效果,控制量较为平滑。

四旋翼飞行器齿轮箱-支臂组件动态特性分析

为提高重载油动四旋翼飞行器的稳定性,研究齿轮箱-支臂组件动态特性并进行结构优化。利用Lanczos特征值求解器,进行齿轮箱-支臂组件模态分析,并通过试验采集组件中心位置的振动加速度值,优化芯轴长径比。采用Runge-Kutta法编程求解组件的动力学方程,揭示组件振动的规律和影响因素。研究结果表明:传动芯轴长径比超过20会产生较大弯曲振动,优化传动芯轴长径比(<14)可有效改变其固有频率,避开激励频率及倍频;振动加速度随转速增大先增大、后减小,当激励频率与系统固有频率相等时达到最大;通过优化斜支撑的角度提高组件刚度可实现减振。

基于模糊-比例积分偏差修正的多旋翼飞行器姿态测算系统

以多旋翼飞行器为平台,结合遥感技术可实现对近地面农田信息进行遥感监测。飞行控制是多旋翼飞行器的核心,它主要负责实时收集传感器测量数据,解算飞行姿态,通过控制算法控制电机运转。因此,准确实时获取姿态信息是实现多旋翼飞行器的飞行控制基础,该文提出了基于模糊-比例积分(fuzzy-proportion integration,Fuzzy-PI)偏差修正的多旋翼飞行姿态测算系统。该系统由加速度传感器、陀螺仪、电子罗盘和STM32F103微处理器组成。采用四元数坐标转换,将测算系统中各传感器测量的姿态偏差代入模糊-比例积分偏差修正解算方法得到多旋翼飞行器的姿态,通过串口显示测算结果,并在SGT320E型3轴多功能转台上对测算的姿态进行验证。试验结果表明该文提出姿态测算系统解算时间达450次/s,静态测量时横滚角和俯仰角平均误差为1.213°和1.072°,长时间静态测量并未产生漂移,为多旋翼飞行器准确控制姿态奠定基础。当转台以频率为0.1 Hz,幅度为30°的正弦波方式运动时,测算系统测量精度能达到1°。试验结果表明在该文提出的多传感器姿态测算硬件系统中,模糊-比例积分偏差修正的多传感器信息融合方法能动态修正传感器间的偏差,满足快速准确跟踪运动姿态的要求。该成果为多旋翼飞行器的姿态控制提供参考。

基于改进LADRC的矢量推力双旋翼飞行器姿态控制

针对矢量推力双旋翼无人机姿态控制过程中存在强耦合、模型不精确的问题,提出了一种改进型的线性自抗扰姿态控制(linear active disturbance rejection controller,LADRC)方法。该方法利用改进线性扩张状态观测器(linear extended state observer,LESO)提高对总扰动的实时观测精度,根据姿态角的误差及其变化率引入模糊控制思想对线性状态误差反馈控制律进行在线参数整定,最后以矢量推力双旋翼飞行器为研究对象,对比PID和常规LADRC对外界扰动的抗扰效果,仿真试验验证了该方法能够较好估计补偿系统的总扰动,具有更好的抗扰性能和收敛速度。

四旋翼飞行器姿态与位置的DIC-PID控制

针对四旋翼飞行器姿态与位置的解耦控制,提出了一种动态逆控制与PID结合的混合控制策略。首先,将四旋翼当作单刚体,通过牛顿-欧拉方程获得其非线性动力学模型。其次,用动态逆控制设计内回路控制器,用PID控制设计外回路控制器,实现姿态与位置通道的解耦控制。最后,在仿真环境下,通过阶跃响应和跟踪上升螺旋线检验了所提控制算法的稳定性与有效性。同时,将控制算法写入飞行控制器,通过飞行实验验证了所提控制算法的实用性。结果表明,所提控制算法对外界扰动与未建模动态有较好的抑制能力,能够满足四旋翼飞行器姿态控制与位置控制的需求。

涡轮叶片装配智能优化算法

涡轮组件装配是发动机制造过程的重要组成部分,在装配过程中为保证涡轮叶片装配完成后的转子不平衡量符合设计标准,需对叶片进行分组试装等步骤,装配效率因此受到影响。为解决此问题,提出一种基于改进模拟退火算法的叶片装配序列优化方法。建立由轮盘自身不平衡量与叶片不平衡量相结合的数学模型,采用多邻域搜索机制,改进退火机制,增加升温、记忆模块等方法来改进算法,通过实例验证了算法的有效性,并与蝴蝶算法,天鹰算法,原始模拟退火算法进行比较,有效地降低了涡轮转子不平衡量。结果表明,改进的模拟退火算法能够有效的减少叶片装配后的不平衡量。为使该算法能够更方便的服务于装配现场,基于MFC框架开发一款叶片装配软件,为解决叶片装配需进行多次拆装以及装配效率低的问题提供了一种有效的方案。

抑郁症治疗的新靶点-mTOR信号通路

近年临床研究表明,单次注射低剂量谷氨酸N-甲基-D-天门冬氨酸(NMDA)受体拮抗剂氯胺酮可以在2小时内缓解抑郁症状,药效持续长达一周,引发抑郁症治疗领域的高度关注,但氯胺酮的快速起效抗抑郁机制至今尚不明确。最近李楠欣等人研究发现氯胺酮能快速激活哺乳动物的雷帕霉素靶点(mTOR)途径,从而导致大鼠前额皮质突触信号蛋白增多及棘突触数量增加。NMDA受体的其他拮抗剂,如CP-101606(曲索罗地)等也能产生与氯胺酮类似的抗抑郁作用,激活mTOR信号通路。这些研究表明,mTOR信号通路很有可能是一种新型快速起效抗抑郁药治疗的靶点。

V-22“鱼鹰”倾转旋翼机研制历程与关键技术

倾转旋翼机具有速度快、噪声小、航程远、载重大和耗油率低等优点,本文介绍了贝尔直升机公司V-22"鱼鹰"倾转旋翼机从原理验证阶段的XV-3机到方案验证阶段的XV-15机,再到实用工程研制阶段的V-22"鱼鹰"机循序渐进的研制历程,并叙述了倾转旋翼机研制中的几项关键技术。

利用旋翼机和固定翼飞机的空气动力学理论综合估算电动垂直起降飞行器的飞行性能

根据旋翼机和固定翼飞机的气动理论开发了一个综合方法过程用于估算电动垂直起降(Electric vertical takeoff and landing, e VTOL)飞行器的飞行性能。这种飞机通常采用多旋翼垂直飞行,螺旋桨和机翼的不同组合方式实现飞行。其中,对旋翼和螺旋桨的气动性能采用传统动量理论分析和旋翼元素分析。本文利用此综合理论研究了12架e VTOL飞行器的飞行性能,包括多旋翼飞行器、矢量推进飞行器和升力巡航飞行器。计算了悬停、爬升和下降以及巡航水平飞行,不同飞行状态时驱动电机、旋翼和机身的飞行特性。据此,可以进一步确定电力推进系统的性能指标,以匹配螺旋桨或旋翼,从而满足飞行任务。