Robust estimation-free prescribed performance back-stepping control of air-breathing hypersonic vehicles without affine models

This paper investigates the design of a novel estimation-free prescribed performance non-affine control strategy for the longitudinal dynamics of an air-breathing hypersonic vehicle (AHV) via back-stepping. The proposed control scheme is capable of guaranteeing tracking errors of velocity, altitude, flight-path angle, pitch angle and pitch rate with prescribed performance. By prescribed performance, we mean that the tracking error is limited to a predefined arbitrarily small residual set, with convergence rate no less than a certain constant, exhibiting maximum overshoot less than a given value. Unlike traditional back-stepping designs, there is no need of an affine model in this paper. Moreover, both the tedious analytic and numerical computations of time derivatives of virtual control laws are completely avoided. In contrast to estimation-based strategies, the presented estimation-free controller possesses much lower computational costs, while successfully eliminating the potential problem of parameter drifting. Owing to its independence on an accurate AHV model, the studied methodology exhibits excellent robustness against system uncertainties. Finally, simulation results from a fully nonlinear model clarify and verify the design.     

A Novel Robust Flight Controller Design for an Air-Breathing Hypersonic Vehicle

A novel robust flight control design method is proposed for a generic air-breathing hypersonic vehicle based on a state-dependent Riccati equation technique and a nonlinear disturbance observer. The highly nonlinear dynamics of the hypersonic vehicle are firstly brought to a linear structure having a state-dependent coefficient form. And then a state-dependent Riccati equation is solved at each sampling moment to obtain a nonlinear feedback optimal control law. In order to enhance robustness of the closed-loop system, a nonlinear disturbance observer is introduced to estimate the uncertainty caused by parametric variations and external disturbances. The resulting composite controller achieves not only promising robustness and disturbance rejection performance but also flexible adjustment in the response time. Compared to a Kriging controller, the proposed controller has great advantages in the system response time and robustness. The feasibility of the proposed method is validated by simulation results.     

带有干扰观测器的高超声速飞行器滑模控制

针对高超声速飞行器非线性和易受干扰影响的特点,提出了带有扩张状态干扰观测器的连续滑模控制方法.在对飞行器非线性模型做线性化处理的基础上,设计了一种连续时间滑模控制器.该控制器在对不确定性和未知动态保持鲁棒性的基础上,消除了传统滑模中存在的抖振现象.对系统中存在的外加干扰,设计了扩张状态干扰观测器.将外加干扰作为系统的一个状态变量被估计出来,再将估计值用作滑模控制器的补偿量,进而达到消除外干扰的目的.在高超声速飞行器巡航飞行状态的基础上进行了仿真.仿真结果表明,所提出的方案能够满足控制要求.     

Robust tracking control for an air-breathing hypersonic vehicle with input constraints

The focus of this paper is on the design and simulation of robust tracking control for an air-breathing hypersonic vehicle (AHV), which is affected by high nonlinearity, uncertain parameters and input constraints. The linearisation method is employed for the longitudinal AHV model about a specific trim condition, and then considering the additive uncertainties of three parameters, the linearised model is just in the form of affine parameter dependence. From this point, the linear parameter-varying method is applied to design the desired controller. The poles for the closed-loop system of the linearised model are placed into a desired vertical strip, and the quadratic stability of the closed-loop system is guaranteed. Input constraints of the AHV are addressed by additional linear matrix inequalities. Finally, the designed controller is evaluated on the nonlinear AHV model and simulation results demonstrate excellent tracking performance with good robustness.     

高超声速飞行器输入受限反演鲁棒控制

针对执行机构受限条件下高超声速飞行器的控制问题,提出一种鲁棒反演控制设计 方法.设计一种新的辅助系统对跟踪误差和控制律进行补偿,保证执行器受限时跟踪误差的 有界性.为了避免传统反演方法中虚拟导数计算量膨胀问题,引入滑模微分器对虚拟 导数进行求解.为了增强系统的鲁棒性,基于改进反正切跟踪微分器(MATD)设计 一种新型干扰观测器,对系统的不确定项进行估计和补偿.最后,通过实例仿真验证了所提出控制器的有效性.     

Intelligent control for near-autonomous aircraft missions

The focus of this paper is the design and implementation of a full envelope, nonlinear aircraft controller that includes stability augmentation, tracking control, and flight-path generation. The control system is demonstrated using a 6 degree-of-freedom (DOF) high performance aircraft model with nonlinear kinematics, full-envelope nonlinear aerodynamics, first-order thrust model, and first-order actuator dynamics. Ideas from the field of intelligent control were used in the definition of the controller architecture. More specifically, “levels of intelligent control” were used to provide a systematic structure for the architecture. Several ideas from the field of computational intelligence were also used including neural networks, genetic algorithms, and adaptive critics     

基于随机鲁棒设计的高超音速飞行器线性二次型控制

针对高超音速飞行器具有高度非线性、输入输出之间强耦合以及参数不确定等特点,提出了基于随机鲁棒设计的线性二次型控制。这一控制方案基于系统控制需求,利用蒙特卡罗仿真方法建立随机鲁棒目标函数,并通过遗传算法优化控制系统设计参数。该控制方案保证了飞行的纵向稳定性,改善了其控制性能。基于某常规高超音速飞行器纵向模型进行仿真验证,结果表明该方案能够满足系统控制需求且具有强鲁棒性。     

Output Feedback Dynamic Surface Controller Design for Airbreathing Hypersonic Flight Vehicle

This paper addresses issues related to nonlinear robust output feedback controller design for a nonlinear model of airbreathing hypersonic vehicle. The control objective is to realize robust tracking of velocity and altitude in the presence of immeasurable states, uncertainties and varying flight conditions. A novel reduced order fuzzy observer is proposed to estimate the immeasurable states. Based on the information of observer and the measured states, a new robust output feedback controller combining dynamic surface theory and fuzzy logic system is proposed for airbreathing hypersonic vehicle. The closedloop system is proved to be semi-globally uniformly ultimately bounded (SUUB), and the tracking error can be made small enough by choosing proper gains of the controller, filter and observer. Simulation results from the full nonlinear vehicle model illustrate the effectiveness and good performance of the proposed control scheme.      

基于非线性干扰观测器的变几何进气道飞行器自适应模糊控制

可移动唇罩式变几何进气道高超声速飞行器是指飞行器发动机前端设有一个能沿着来流方向前后平移的唇罩,从而能够实现飞行器的最大气流捕获,以提高发动机的机动性能.针对变几何进气道飞行器强非线性以及存在参数不确定性等特点,提出一种基于非线性干扰观测器的自适应模糊控制策略.首先,基于反步思想将变几何进气道飞行器模型分解为速度子系统和高度子系统,并将其转化为严反馈形式控制系统;其次,利用模糊逻辑系统并结合自适应技术在线逼近模型参数不确定项;再次,采用非线性干扰观测器补偿模糊系统逼近误差和飞行器建模误差;最后,通过仿真结果表明所设计的控制器能对飞行器速度和高度参考指令实现准确、稳定地跟踪,并验证了变几何进气道飞行器的优势.     

Modeling and robust decoupling control for hypersonic scramjet vehicle

In this paper, the modeling and the robust decoupling control for a generic hypersonic scramjet vehicle are studied. Firstly, the dynamics of the hypersonic vehicle are modeled by applying the Lagrangian approach, which captures the most primary characteristics such as elastic deformation, aerodynamics, aero-heating, variable mass, effect of spherical rotating earth and their inherent interactions. Then, a robust output decoupling controller is designed by using nonlinear dynamic inversion plus the desired proportional integral dynamics, and natural time-scale separation theorem between fast and slow variables. Finally, the nonlinear simulations confirm the effectiveness of the robust decoupling controller.     

Adaptive dynamic surface control of a hypersonic flight vehicle with improved tracking

This work presents a nonlinear adaptive dynamic surface air speed and a flight path angle control design procedure for the longitudinal dynamics of a generic hypersonic flight vehicle. The proposed design scheme takes into account the magnitude, rate, and bandwidth constraints on the actuator signals. A new approach is used to enhance tracking performance and avoid a large initial control signal. The uncertain nonlinear functions in the flight vehicle model are approximated by using radial basis function neural networks. A detailed stability analysis of the designed controllers shows that all the signals of the closed‐loop system are uniformly ultimately bounded. The robust performance of the design scheme is verified through numerical simulations of the flight vehicle model for various parameter variation test cases. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Multi-objective robust control based on fuzzy singularly perturbed models for hypersonic vehicles

In this paper, we propose a multi-objective robust controller based on fuzzy singularly perturbed models (FSPM) for the longitudinal motion of an air-breathing hypersonic vehicle. The control objective is to provide velocity and altitude tracking in the presence of the uncertainties and unknown nonlinearities in the model caused by variations in flight conditions. By approximating the multi-time-scale model with FSPM, ill-posed matrix calculations are circumvented. Under this framework, a fuzzy multi-object...     

Fuzzy tracking control design for hypersonic vehicles via T-S model

The main focus of this paper is on designing a T-S fuzzy controller for the hypersonic vehicle. The longitudinal dynamics of the vehicle are studied using time-scale decomposition to reduce the complexity of T-S modeling. The dynamic inversion with PI control technique is applied for the slow dynamics to derive the flight path angle command and throttle setting by taking the pilot altitude and velocity command as its inputs. The T-S fuzzy controller is designed for the fast dynamics to derive the elevator d...     

Back-stepping Robust Control for Flexible Air-breathing Hypersonic Vehicle via α-filter-based Uncertainty and Disturbance Estimator

In this paper, a robust control scheme using back-stepping and α-filter-based uncertainty and disturbance estimator (UDE) is designed for flexible air-breathing hypersonic vehicle (FAHV) in the presence of severe external disturbances. Firstly, with the aid of back-stepping technique, the longitudinal dynamics of FAHV is separated into velocity and altitude subsystems. Feedback linearization (FL) is utilized to design control laws for each subsystem. Secondly, to enhance robustness of the controller, α-filter-based UDEs are constructed to estimate the lumped disturbances, including aerodynamic parameter uncertainties, flexible effects and external disturbances. More importantly, the performance superiority of α-filter-based UDE is clarified via frequency response analysis and comparisons with an extended state observer (ESO). Furthermore, the issue of tuning design parameter α is analyzed. The stability of closed-loop system is proved by Lyapunov stability theory. Simulation results demonstrate the effectiveness of the proposed control strategy.

     

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.     

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.     

高超音速飞行器鲁棒控制研究

针对高超音速飞行器具有高度非线性、输入输出之间强耦合以及参数不确定等特点,提出了基于随机鲁棒设计的动态逆控制;这一控制方案基于系统控制需求,利用蒙特卡罗仿真方法建立目标函数,并通过遗传算法最优化系统设计参数,该控制方案将动态逆控制的非线性解耦控制能力与随机鲁棒设计的强鲁棒性结合,保证了飞行的纵向稳定性,改善了其控制性能;基于某常规高超音速飞行器纵向模型进行仿真验证,结果表明该方案能够满足系统控制需求且具有强鲁棒性。     

DESIGN OF A FLIGHT CONTROLLER FOR HYPERSONIC FLIGHT EXPERIMENT VEHICLE

National Aerospace Laboratory (NAL) and National Space Development Agency (NASDA) of Japan launched a hypersonic flight experiment vehicle (HYFLEX) for flight experiment of reentry phase to the top of the atmosphere in 1996. Flight condition in the experiment varied from an altitude of 107km and a speed of Mach 15 to an altitude of 30km and a speed of Mach 2. This paper describes design of a flight control system of the HYFLEX and evaluation of robustness against variations of command inputs and aerodynamic coefficients. A nonlinear simulation model that describes the vehicle motion has been made using the data obtained from wind tunnel experiments by NAL and NASDA. Linear models are computed from the nonlinear model for every second of the flight, assuming that the flight is a quasi‐trimmed one. Because the vehicle has a cylinder‐like configuration and takes a large angle of attack and a bank angle, coupling between longitudinal and lateral‐directional motions cannot be neglected; hence, the linear models include coupling terms. Averaging the linear models yields a nominal model for controller design, where the type‐1 linear quadratic (LQ) servo controller is employed for attitude control. Since the flight condition varies so much, it is difficult to control the vehicle using a single set of control gains. Therefore the flight period is segmented into eight intervals, for each of which a nominal linear model is computed, and then eight sets of feedback gain matrices are computed and scheduled as a function of flight time. The effectiveness and robustness of the flight control system are examined through computer simulation. Simulation results indicate that the control system works well even when attitude commands and aerodynamic parameters considerably deviate from nominal ones.     

Prescribed performance fuzzy back-stepping control of a flexible air-breathing hypersonic vehicle subject to input constraints

Journal of Intelligent Manufacturing - The design of prescribed performance fuzzy back-stepping tracking control for a flexible air-breathing hypersonic vehicle (FAHV) with actuator constraints is...