吸气式高超声速飞行器考虑控制约束的设计优化

为了能够获得性能卓越,可靠的吸气式高超声速飞行器(AHSV)设计,需要考虑其特殊动力学特性及控制系统的性能约束,研究面向控制系统设计的系统设计优化策略.首先,简要介绍了AHSV第1原理建模与参数化建模相关的问题与方法;其次,分析了AHSV系统模型与控制系统性能之间的约束耦合特性:系统模型的不稳定极点及其左特征向量与控制信号的饱和约束确定了反馈控制系统的零可控区域;系统模型右半平面(RHP)零极点对于反馈闭环系统灵敏度函数与补灵敏度函数具有峰值约束与带宽限制;最后,考虑系统模型与控制系统约束耦合的特性,根据选取的总体优化设计目标,介绍了系统本体与控制系统组合优化的相关策略.并简要分析了各优化策略的实用性及适用范围.对于AHSV考虑控制系统性能约束的优化设计提供了一种研究方法和设计思路.     

基于神经网络补偿的高超声速飞行器滑模控制

针对吸气式高超声速飞行器的轨迹控制问题,提出了一种基于自适应径向基函数(RBF)神经网络的滑模控制方法.建立了高超声速飞行器的纵向动态模型;设计了滑模控制器,利用自适应RBF神经网络对系统不确定项进行在线逼近,对滑模控制器进行补偿;基于李雅普诺夫的稳定性分析证明了闭环系统的稳定性.仿真结果表明:控制系统能够实现对于高超声速飞行器给定指令的有效跟踪.     

高超声速飞行器动力学建模与分析

吸气式高超声速飞行器本身具有复杂动力学特性,由于存在强烈的结构弹性/推力/气动的耦合以及其力学环境的诸多不确定因素,使得飞行器本身的动态特性相当复杂.经典牛顿力学方法建模难以清楚反映飞行器结构弹性/推力/气动耦合.为更为精确的分析高超声速飞行器复杂的动力学特性,本文针对吸气式高超声速飞行器采用拉格朗日法进行了建模与动态特性分析,选择了具有代表性的特征点,建立了小扰动模型,在不同特征点上采用拉格朗日模型和牛顿力学模型对比分析高超声速飞行器的动力学特性.结果表明,拉格朗日方法所建立的动力学模型能够更清楚地符合高超声速飞行器结构弹性和气动特性耦合以及发动机尾流和气动特性之间的耦合特性.     

吸气式高超声速飞行器气动耦合干扰效应研究

研究飞行器与冲压发动机耦合干扰效率优化问题,由于吸气式高超声速飞行器机身与冲压发动机之间存在高度耦合,针对耦合效应不可避免对飞行器稳定性产生影响,为提高控制系统性能,提出飞行器机身与发动机之间的耦合干扰效应问题展开深入研究.在高超声速飞行器各部件无粘气动特性的基础上,采用尾气羽流分析模型研究机身与冲压发动机耦合干扰效应,并基于飞行器几何参数化模型进行仿真.结果表明分析模型能较精确地快速反应机身与冲压发动机之间耦合干扰效应,为吸气式高超声速飞行器机身/发动机一体化设计和控制系统优化设计及其动力学特性研究分析提供依据.     

基于模糊控制的高超声速飞行器二阶滑模姿态控制

考虑高超声速飞行器飞行过程中气动参数变动导致的不确定,将模糊控制与二阶滑模控制相结合,形成自适应模糊二阶滑模控制器,用于控制高超声速飞行器姿态的飞行系统中.依据奇异摄动理论,设计快速和慢速双闭环系统控制角速率和姿态角.设计二阶滑模控制器用于有效地衰减抖振,同时对姿态角指令实现准确和快速跟踪.采用自适应模糊逻辑逼近高超声速飞行器动力学和运动学模型中的不确定部分,以对控制器进行有效补偿,基于Lyapunov稳定性理论,推导模糊规则参数的自适应律,确保整个闭环控制系统的稳定.仿真结果表明,所提出的高超声速飞行器的自适应模糊滑模控制系统能够有效抑制气动参数摄动的影响,对姿态角指令有较好的跟踪性能.     

高超声速飞行器的自抗扰控制器设计

由于采用机体一体化设计,吸气式高超声速飞行器的气动特性难以准确获知,建立的数学模型是极为不准确的;设计了一种自抗扰控制器(ADRC),分别设计了速度回路和高度回路的自抗扰控制器;仿真用高超声速飞行器的纵向模型对该控制器进行了验证,证明该控制方法能够有效地跟踪飞行器的高度和速度指令。     

高超声速飞行器姿态控制系统设计

研究气动特性是飞行器姿态稳定性的保证,高超声速飞行器采用姿态控制有助于提高作战效能及生存能力.针对高超声速飞行器作战环境复杂,大气密度偏差大、力/力矩系数不准确造成气动参数偏差较大等特点,采用参数空间方法来设计姿态控制系统.首先建立适用于姿态控制系统的高超声速数学模型,在高超声速气动特性条件下,提出三回路姿态稳定控制系统,根据参数空间方法的原理设计出各回路控制器,最后进行仿真分析验证控制系统的性能.仿真结果表明当气动参数存在较大偏差时,采用基于参数空间法设计的高超声速姿态控制系统可以确保对指令的精确跟踪,并且具有较强的鲁棒稳定性.     

基于特征模型的高超声速飞行器自适应控制研究进展

钱学森先生1945年在论文《论高超声速相似律》中,首次提出了高超声速(hypersonic)的术语.高超声速飞行器具有的强大的军事和民事应用前景,20世纪80年代初,在世界上掀起了研究和发展高超声速飞行器的热潮,其中高超声速飞行器控制是其关键科学和技术问题之一.高超声速飞行器的研究取得了大量理论成果,与其形成鲜明对比的是,高超声速飞行器在试飞实验中却遇到了很大困难,例如X–51A,HTV–2.这种现象不得不引发我们进行深入思考.由于高超声速空气动力学研究的局限性,导致目前所建立的高超声速飞行器的动力学模型,与真实系统相比,其结构和参数不确定性非常大,它从根本上限制了控制理论和方法的研究.并且由于高超声速飞行器动力学模型的复杂性,导致目前工程应用中的控制方法复杂化.因此,针对高超声速飞行器控制问题,需要深入开展气动、控制交叉学科的研究,以及适于工程应用的自适应控制的研究.针对上述问题,我们开展了一定的研究.我们建立了三轴耦合的高超声速飞行器被控对象类X–20及其气动模型,并结合工程应用,直接针对表格形式的气动模型开展控制研究.针对强耦合和无解析动力学的控制问题,特征模型理论有其独特优势.近年来,我们系统研究了基于特征模型的高超声速飞行器的爬升、滑翔和再入控制问题.本文首先介绍特征模型理论和方法,进而综述和分析基于特征模型的高超声速飞行器自适应控制的研究进展,并提出进一步需要研究的问题.     

高超声速飞行器应用保护映射的大包线控制律

针对高超声速飞行器模型具有高度非线性和易变的动态特性,应用保护映射理论提出了一种高超声速飞行器大包线控制律设计方法.首先,结合间隙度量理论建立高超声速飞行器线性变参数(linear parameter-varying,LPV)模型,然后设计控制器结构并计算初始点的控制器参数,并根据保护映射理论分析初始控制器使闭环系统稳定的参数区间,通过迭代运算自适应地获得满足性能要求的控制器参数集合.仿真结果表明,建立的LPV模型具有良好的精确度;所设计的大包线控制律能够满足高超声速飞行器的性能要求,并且保证系统在飞行域内全局稳定.     

高超声速飞行器调度双模预测控制方法

针对一类具有大包线飞行和快时变特性的高超声速飞行器,采用多个线性时变(LTV)多胞模型近似地描述高超声速飞行器的纵向非线性模型.对于各LTV多胞模型,离线设计局部双模预测控制器来显式地处理控制输入和状态的约束问题,并获得相应的稳定域.然后,构造各局部控制器间稳定的切换策略.仿真结果表明,所提方法在控制输入和状态满足给定的约束范围情况下,不仅能更快地跟踪较大范围的速度和高度的指令信号,而且大幅减少了在线计算时间.     

Nonlinear Robust Adaptive Deterministic Control for Flexible Hypersonic Vehicles in the Presence of Input Constraint

A nonlinear deterministic robust control scheme is developed for a flexible hypersonic vehicle with input saturation. Firstly, the model analysis is conducted for the hypersonic vehicle model via the input‐output linearized technique. Secondly, the sliding mode manifold is designed based on homogeneity theory. Then an adaptive high order sliding mode control scheme is proposed to achieve tracking for the step change in altitude and velocity for hypersonic vehicles where the uncertainty boundary is unknown. Furthermore, the control input constraint is investigated and another new adaptive law is proposed to estimate the uncertainties and to guarantee the stability of the system with input saturation. Finally, the simulation results are provided to demonstrate the effectiveness of the proposed method.     

Maximal controllability of input constrained unstable systems by the addition of implicit constraints

The null controllable set of a system is the largest set of states that can be controlled to the origin. Control systems that have a region of attraction equal to the null controllable set are said to be maximally controllable closed-loop systems. In the case of open-loop unstable plants with amplitude constrained control it is well known that the null controllable set does not cover the entire state-space. Further the combination of input constraints and unstable system dynamics results in a set of state constraints which we call implicit constraints. It is shown that the simple inclusion of implicit constraints in a controller formulation results in a controller that achieves maximal controllability for a class of open-loop unstable systems.     

Feedback control design with vibration suppression for flexible air-breathing hypersonic vehicles

This paper investigates the problem of feedback control design with vibration suppression for a flexible air-breathing hypersonic vehicle （FAHV）. FAHV includes intricate coupling between the engine and flight dynamics, as well as complex interplay between flexible and rigid modes, which results in an intractable system for the control design. In this paper, a longitudinal model, which is described by a coupled system of ordinary differential equations （ODEs） and partial differential equations （PDEs）, is adopted. Firstly, a linearized ODE model for the rigid part is established around the trim condition, while vibration of the fuselage is described by PDEs. Secondly, based on the Lyapunov direct method, a control law via ODE state feedback and PDE boundary output feedback is designed for the system such that the closed-loop exponential stability is ensured. Finally, simulation results are given to illustrate the effectiveness of the proposed design method.     

Stabilization on null controllable region of delta operator systems subject to actuator saturation

This paper focuses on stabilization on null controllable region of delta operator systems subject to actuator saturation via constructing suitable controllers. Under a saturated linear feedback law, a set of stable equilibrium points is obtained for the delta operator system with actuator saturation. A comprehensive controller is given to show global stabilization of the delta operator system. Thereby, semi‐global stabilization of the delta operator system is also achieved. For higher‐order systems with no more than two unstable exponentially poles, a new feedback law is constructed to achieve semi‐global stabilization on the null controllable region. Finally, three examples are given to illustrate the effectiveness of the proposed techniques. Copyright © 2016 John Wiley & Sons, Ltd.     

Audio steganography with AES for real-time covert voice over internet protocol communications

As a popular real-time service on the Internet, Voice over Internet Protocol （VoIP） communication attracts more and more attention from the researchers in the information security field. In this study, we proposed a VoIP steganographic algorithm with variable embedding capacities, incorporating AES and key distribution, to realize a real-time covert VoIP communication. The covert communication system was implemented by embedding a secret message encrypted with symmetric cryptography AES-128 into audio signals encoded by PCM codec. At the beginning of each VoIP call, a symmetric session key （SK） was assigned to the receiver with a session initiation protocol-based authentication method. The secret message was encrypted and then embedded into audio packets with different embedding algorithms before sending them, so as to meet the real- time requirements of VolP communications. For each audio packet, the embedding capacity was calculated according to the specific embedding algorithm used. The encryption and embedding processes were almost synchronized. The time cost of encryption was so short that it could be ignored. As a result of AES-based steganography, observers could not detect the hidden message using simple statistical analysis. At the receiving end, the corresponding algorithm along with the SK was employed to retrieve the original secret message from the audio signals. Performance evaluation with state-of-the-art network equipment and security tests conducted using the Mann-Whitney-Wilcoxon method indicated that the proposed steganographic algorithm is secure, effective, and robust.     

基于反步法的高超音速飞机纵向逆飞行控制

针对高超音速飞机纵向运动的数学模型具有严重非线性、不稳定、多变量耦合以及不确定的气动参数等特点，采用非线性动态逆控制与反步法相结合的方法为其设计飞行控制系统．该系统以非线性动态逆控制作为控制内环，通过将非线性的多输入多输出系统进行精确线性化，解除了多变量之间的强耦合关系；并以反步法作为控制外环．保证系统的全局稳定以及抑制不确定参数的扰动．仿真研究表明．所提出的控制方法可以确保高超音速飞机的纵向稳定性．改善其飞行品质．     

Adaptive restricted trajectory tracking for a non-minimum phase hypersonic vehicle model

The design of a nonlinear robust controller for a non-minimum phase model of an air-breathing hypersonic vehicle is presented in this work. When flight-path angle is selected as a regulated output and the elevator is the only control surface available for the pitch dynamics, longitudinal models of the rigid-body dynamics of air-breathing hypersonic vehicles exhibit unstable zero-dynamics that prevent the applicability of standard inversion methods for control design. The approach proposed in this paper uses a combination of small-gain arguments and adaptive control techniques for the design of a state-feedback controller that achieves asymptotic tracking of a family of velocity and flight-path angle reference trajectories belonging to a given class of vehicle maneuvers, in spite of model uncertainties. The method reposes upon a suitable redefinition of the internal dynamics of a control-oriented model of the vehicle dynamics, and uses a time-scale separation between the controlled variables to manage the peaking phenomenon occurring in the system. Simulation results on a full nonlinear vehicle model that includes structural flexibility illustrate the effectiveness of the methodology.     

Adaptive Anti-saturation Tracking Control with Prescribed Performance for Hypersonic Vehicle

For the hypersonic vehicle with external disturbance, input saturation, model parameter uncertainties and prescribed performance constraint, the tracking control strategy is studied in the thesis. Firstly, a prescribed performance function is introduced into the control design by transforming auxiliary variable errors, which guarantees tracking performance of the control system. On the basis of second-order system model of hypersonic vehicle, an adaptive anti-saturation terminal sliding mode (TSM) controller with prescribed performance is presented by using the adaptive control theory and TSM control. The stability theory of the control law is presented by Lyapunov stability theory and the numerical simulations are conducted to indicate the effectiveness of the proposed control scheme.     

输入受限约束下的汽车横摆力矩混合切换控制策略研究

目前在汽车横摆力矩控制器设计中,往往忽略了系统输入是有限的这一约束条件,因此所设计的控制器并不能总是工作在预先设定的反馈规律下。这在实际环境中将导致系统性能的不可靠。为此,在二次最优控制器的基础上,增加抗饱和控制器的设计,并通过混合切换控制策略来达到既保证良好的控制性能,同时又能适应系统输入有限这一约束条件。仿真实验表明,所设计的控制策略与这些控制器单独控制相比,不仅抗饱和性能得到提高,而且控制性能也同样令人满意。该方案的设计为更加合理的汽车稳定性控制策略提供参考。     

Linear unstable plants with saturating actuators: Robust stabilization by a time varying sliding surface

This paper proposes the use of a time-varying sliding surface for the robust stabilization of linear uncertain SISO plants with saturating actuators. A constructive procedure for its design is also proposed, and stability of the closed loop system is proved in the null controllable region. The proposed technique does not require plant stability, and can manage any bounded disturbance term satisfying the matching condition. Theoretical results have been validated by simulation using the missile roll angle control problem.