A novel trajectory planning strategy for aircraft emergency landing using Gauss pseudospectral method

To improve the survivability during an emergency situation, an algorithm for aircraft forced landing trajectory planning is proposed. The method integrates damaged aircraft modelling and trajectory planning into an optimal control framework, in order to deal with the complex aircraft flight dynamics, a solving strategy based on Gauss pseudospetral method （GPM） is presented. A 3-DOF nonlinear mass-point model taking into account the wind is developed to approximate the aircraft flight dynamics after loss of thrust. The solution minimizes the forced landing duration, with respect to the constraints that translate the changed dynamics, flight envelope limitation and operational safety requirements. The GPM is used to convert the trajectory planning problem to a nonlinear programming problem （NLP）, which is solved by sequential quadratic programming algorithm. Simulation results show that the proposed algorithm can generate the minimum-time forced landing trajectory in event of engine-out with high efficiency and precision.     

Clearance of Nonlinear Flight Control Laws Using Hybrid Evolutionary Optimization

The application of two evolutionary optimization methods, namely, differential evolution and genetic algorithms, to the clearance of nonlinear flight control laws for highly augmented aircraft is described. The algorithms are applied to the problem of evaluating a nonlinear handling quality clearance criterion for a simulation model of a high-performance aircraft with a delta canard configuration and a full-authority flight control law. Hybrid versions of both algorithms, incorporating local gradient-based optimization, are also developed and evaluated. Statistical comparisons of computational cost and global convergence properties reveal the benefits of hybridization for both algorithms. The differential evolution approach in particular, when appropriately augmented with local optimization methods, is shown to have significant potential for improving both the reliability and efficiency of the current industrial flight clearance process     

基于PSO算法的WNN大包线增益调参控制律设计

提出了一种基于粒子群优化算法的小波神经网络大包线调参控制律设计方法.该方法用小波函数代替了Sigmoid函数作为激活函数.由于结合了小波变换良好的高频域时间精度、低频域频率精度的性质和神经网络的自学习功能,因而具有较强逼近非线性函数的能力.为了克服局部极小值问题并进一步提高对非线性函数逼近能力,利用粒子群优化算法对小波神经网络进行参数训练,并利用该网络实现了大包线增益调参.飞行仿真结果表明,所设计的小波神经网络增益调参控制器具有优良的控制性能,不仅能够保证平衡状态下的控制效果,而且在未训练的平衡状态下依然具有良好的控制性能,并且在存在20%的建模误差时,最大超调量仅为6 m,仅是使用常规增益调参方法的18%.     

Nonlinear identification and control of aircraft

The major goal of this paper is to approach and solve a spectrum of extremely important problems in nonlinear analysis, identification, optimization, and control of current and next generation advanced aircraft. High-performance aircraft must satisfy the required performances in the specified operational flight envelope at various attitudes and velocities, high-angle-of-attack regimes, all-weather, day and night operation. To improve mission effectiveness, ensure the specified flying and handling qualities (agility, manoeuvrability, controllability, and other pilotage quantities), guarantee survivability, damage adaptation and recovery, this paper reports a new, completely automated realtime motion control conceptual framework with failure accommodation features (self-repairing flight control). Innovative highly efficient identification and design methods are applied and verified. To attain the desired aircraft performance and expand the operational flight envelope at high-angle-of-attack regimes, identification and constrained optimization problems are solved using the developed motion control framework. An example is thoroughly studied to demonstrate the practical use and capabilities of the reported nonlinear design and identification procedures.     

Flight envelope protection of aircraft using adaptive neural network and online linearisation

Flight envelope protection algorithm is proposed to improve the safety of an aircraft. Flight envelope protection systems find the control inputs to prevent an aircraft from exceeding structure/aerodynamic limits and maximum control surface deflections. The future values of state variables are predicted using the current states and control inputs based on linearised aircraft model. To apply the envelope protection algorithm for the wide envelope of the aircraft, online linearisation is adopted. Finally, the flight envelope protection system is designed using adaptive neural network and least-squares method. Numerical simulations are conducted to verify the performance of the proposed scheme.     

飞机俯仰运动自抗扰控制器设计

提出了利用自抗扰控制器在大包线范围内设计飞机俯仰运动控制器的新方法．利用二阶自抗扰控制器补偿系统模型扰动和外扰，实现了纵向运动俯仰角变量的跟踪控制．自抗扰控制器直接依据飞机的非线性模型，符合飞机动力学模型摄动大的特点，在很大的包线范围内不需要改变控制器的结构和参数，简化了飞行控制律的设计过程．大包线范围内的仿真结果表明，系统具有良好的动态和稳态性能，控制器具有很强的鲁棒性，为解决大包线范围内的飞行控制问题提供了一种有效的新途径．     

On improvement of transient performance in tracking control for a class of nonlinear systems with input saturation

This paper studies the technique of the composite nonlinear feedback (CNF) control for a class of cascade nonlinear systems with input saturation. The objective of this paper is to improve the transient performance of the closed-loop system by designing a CNF control law such that the output of the system tracks a step input rapidly with small overshoot and at the same time maintains the stability of the whole cascade system. The CNF control law consists of a linear feedback control law and a nonlinear feedback control law. The linear feedback law is designed to yield a closed-loop system with a small damping ratio for a quick response, while the nonlinear feedback law is used to increase the damping ratio of the closed-loop system when the system output approaches the target reference to reduce the overshoot. The result has been successfully demonstrated by numerical and application examples including a flight control system for a fighter aircraft.     

An implementable digital adaptive flight controller designed using stablized single-stage algorithms

Adaptive flight control systems are of interest because of their potential for providing uniform stability and handling qualities over a wide flight envelope despite uncertainties in the open-loop characteristics of the aircraft. Because of the potential for actual implementation of adaptive control algorithms using contemporary, small digital computer equipment, a study has been made to define an implementable digital adaptive control system which can be used for a typical fighter aircraft. Towards such an implementation, an explicit adaptive controller, which makes direct use of on-line parameter identification, has been developed and applied to both the linearized and nonlinear equations of motion for the F-8 aircraft. This controller is composed of an on-line weighted least squares parameter identifier, a Kalman state filter, and a real model following control law designed using single-stage performance indices. The corresponding control gains are readily adjustable in accordance with parameter changes to ensure asymptotic stability if the conditions of perfect model following are satisfied, and stability in the sense of boundedness otherwise. Simulation experiments with realistic measurement noise indicate that the controller was effective in compensating for parameter variations and capable of rapid recovery from a set of erroneous initial parameter estimates which defined a set of destabilizing gains.     

A QFT SUBSONIC ENVELOPE FLIGHT CONTROL SYSTEM DESIGN

An aircraft's response to control inputs varies widely throughout its full flight envelope. Furthermore, the aircraft configuration impacts control response through variations in centre of gravity and moments of inertia. Quantitative feedback theory (QFT) is a robust control system design method which provides a full-envelope flight control system design and gives the engineer direct control over compensator order and gain. A full subsonic flight envelope FCS is designed for using QFT for four representative aircraft configurations. Flying qualities are embedded in the longitudinal design by using a control variable which varies with the aircraft's energy state throughout the flight envelope. Linear simulations with realistically large control inputs are used to validate the design. © 1997 by John Wiley & Sons, Ltd. This paper was prepared under the auspices of the US Government and it is therefore not subject to copyright in the US.     

FAULT TOLERANT CONTROL SYSTEM: QFT DESIGN

This paper addresses flight control system synthesis and the accommodation of controlled plant variation in an aircraft design envelope by using the frequency domain based quantitative feedback theory (QFT) robust control system design method. Plant variations considered include varying flight conditions in the flight envelope and damage to aerodynamic control surfaces. A robust flight control system is designed for the aircraft's longitudinal and lateral directional channels and validated with simulations containing nonlinear saturation elements. © 1997 by John Wiley & Sons, Ltd. This paper was produced under the auspices of the US Government and it is therefore not subject to copyright in the US.     

Adaptive flight control using optimal linear regulator techniques

Simple mechanical linkages are often unable to cope with the many control problems associated with high performance aircraft maneuvering over a wide flight envelope. One procedure for retaining uniform handling qualities over such an envelope is to implement a digital adaptive controller. Towards such an implementation an explicit adaptive controller, which makes direct use of online parameter identification, has been developed using linear analysis, and has been evaluated using both the linear and nonlinear equations of motion for a typical fighter aircraft. The system is composed of an online weighted least squares parameter identifier, a Kalman state filter, and a model following control law designed using optimal linear regulator theory. Simulation experiments with realistic measurement noise indicate that the proposed adaptive system has the potential for on-board implementation.     

Multiobjective optimization–based fault‐tolerant flight control system design

The loss of measurements used for controller scheduling or envelope protection in modern flight control systems due to sensor failures leads to a challenging fault‐tolerant control law design problem. In this article, an approach to design such a robust fault‐tolerant control system, including full envelope protections using multiobjective optimization techniques, is proposed. The generic controller design and controller verification problems are derived and solved using novel multiobjective hybrid genetic optimization algorithms. These algorithms combine the multiobjective genetic search strategy with local, single‐objective optimization to improve convergence speed. The proposed strategies are applied to the design of a fault‐tolerant flight control system for a modern civil aircraft. The results of an industrial controller verification and validation campaign using an industrial benchmark simulator are reported.     

Command and stability systems for aircraft: A new digital adaptive approach

Ensuring good handling qualities of aircraft in the whole flight envelope is a difficult and time consuming task, because aircraft parameters are subjected to drastic changes. Adaptive control is a very promising technique to solve these problems and to improve the performance deficiencies of conventional stability systems with preprogrammed control gains.The approach used in this paper is based on digital control and on a special stabilization concept which requires only three dynamic parameters of the aircraft to meet standard handling qualities criteria. These three parameters cannot be measured directly. Therefore a recursive, weighted least squares algorithm is used, which delivers sufficient fast and accurate on-line parameter estimates. The adaptive control system has proven its very satisfactory performance in several digital and hybrid simulations including fast parameters variations and turbulence conditions. Real flight test data have been used to verify the performance of the identification process and recently flight tests of the complete adaptive system have been successfully carried out with the DO 28 D SK YSERVANT aircraft.     

自抗扰控制器在超机动飞行快回路控制中的应用

提出了一种利用自抗扰控制器算法设计超机动飞行快回路控制律的新方法．根据自抗扰控制器能够动态补偿系统模型扰动和外扰的特性,在超机动飞行的快回路中引入自抗扰控制器。实现了快变量的动态解耦控制．控制律设计直接依据超机动飞行的强耦合、强非线性模型。在较大的包线范围内不需要改变控制器参数．简化了设计过程．仿真结果表明,系统具有良好的动态和稳态性能,控制器具有很强的鲁棒性．     

逐点线性化后退区间最优控制在飞机非线性控制中的应用

常规线性飞控系统针对推力矢量飞机这样的多控制冗余、非线性MIMO系统,无法实现非线性控制．本文针对推力矢量飞机非线性系统,阐述了一种逐点线性化后退区间最优控制算法满足飞行品质要求．首先将作动器,飞行品质和逐点线性化的飞机线性模型综合实现在线建模,然后以飞行状态与预测状态之间的误差、作动器的位置限制和速率限制作为最优指标,最后以此为基础,根据最优控制原理计算当前时刻飞机最优控制指令,实现飞机非线性控制．采用国内某型号飞机气动数据验证此算法的鲁棒性和稳定性．     

涵道尾座式垂直起降飞行器全包线飞行控制

本文针对一种新型涵道尾座式垂直起降飞行器的非线性控制问题, 提出一种全包线飞行控制方案. 在设计 的控制框架中, 采用统一的坐标系描述该飞行器的多模态特性. 对于不可测量的外部力矩, 设计了辅助系统进行观 测及自适应律进行补偿; 对于可测的合外力, 设计了一种基于加速度测量的拉力/姿态几何解耦方法; 同时, 给出了 保证闭环系统全局指数稳定的充分条件. 最后, 所述控制方案成功应用于一小型涵道尾座式无人机上, 并完成了飞 行器垂直/水平模态转换飞行试验, 验证了所提出方法的有效性.     

四轴飞行器姿态控制系统设计

由于四轴飞行器系统具有不稳定、非线性、强耦合等特性,所以姿态控制在飞行器完成飞行任务的过程中尤为 重要。本文着重对飞行器姿态控制算法进行研究。首先对飞行器建立合理的坐标系,根据角度传感器所测得的角度,得到以 四元数表示的姿态转换矩阵。根据空气动力学原理,牛顿第二定律,对飞行器建立动力学模型,得到四个独立通道的控制输入 量,该控制输入量可以通过控制四轴飞行器各个方向的加速度来对飞行器进行姿态控制。     

地效飞行器的纵向稳定性和增稳系统研究

针对地效飞行器因地面效应对纵向系统稳定性的影响,从系统稳定性定义和状态空间稳定判据两个方面,分析了地效飞行器的静稳定性判定条件,利用劳斯维茨判据分析了系统纵向模态的动稳定性,针对纵向动稳定性不足和高度稳定控制的问题,基于飞行包线内典型状态点处的线性模型,采用线性二次型调节器设计了系统的纵向增稳控制律,采用自抗扰控制设计了高度控制律。仿真结果表明,所设计的增稳控制律可以使系统稳定,且具有较强的鲁棒性,所设计的高度控制律使系统具有较强的动态性能,能够准确达到预定飞行高度并保持稳定,响应时间不超过15s。     

含攻击角度约束的三维制导控制一体化鲁棒设计方法

针对具有攻击角度约束的STT飞行器对象,提出了一种三维制导控制一体化鲁棒设计方法.首先,基于某些可行性简化原则,推导出面向三维制导控制一体化设计的非线性数学模型.然后,针对一类多变量非线性系统,通过引入控制补偿项,提出了一种鲁棒动态逆设计方法.结合鲁棒动态逆和动态面控制方法,完成了制导控制一体化鲁棒算法的设计.仿真结果表明,所提出的三维制导控制一体化算法可保证飞行器的稳定飞行和精确制导,并且满足攻击角度的约束要求.此外,该方案具备针对参数不确定性和等效干扰的强鲁棒性能.