MULTI-CONTROLLER STRUCTURE OF SUPERMANEUVERABLE AIRCRAFT

Supermaneuver flight is often operated withhigh angle- of- attack and high angular rates.Su-per- maneuver flight cannot be controlled by aconventional gain- scheduled controller but canbe controlled by using a nonlinear dynamic- in-version controller[1～ 3] .　　 This paper presents a method to use twokinds of controllers,nonlinear dynamic- inver-sion and conventional gain- scheduled con-trollers,in a flight control system.The nonlin-ear dynamic- inversion controller is used to con-trol superm…     

飞机机动飞行的非线性解耦控制研究

本文针对12维非线性飞机动力学模型,利用非线性逆动力学理论和现代最优控制理论设计了一组含有指令静差积分环节的非线性解耦控制规律。这组控制规律使得对状态变量、控制变量以及它们变化率进行加权约束的性能指标极小,并能用平缓的操纵反应和较小的控制能量使飞机达到完全解耦的指定状态。由于这组控制规律计及了飞机动力学模型中的非线性因素,能够弥补飞机机动飞行时非线性特性的恶化影响,在整个飞行包线内都能为飞机提供优良的操纵品质和飞行性能。     

Fractional order modeling and control of dissimilar redundant actuating system used in large passenger aircraft

In this paper, a methodology has been developed to address the issue of force fighting and to achieve precise position tracking of control surface driven by two dissimilar actuators. The nonlinear dynamics of both actuators are first approximated as fractional order models. Based on the identified models, three fractional order controllers are proposed for the whole system. Two Fractional Order PID (FOPID) controllers are dedicated to improving transient response and are designed in a position feedback configuration. In order to synchronize the actuator dynamics, a third fractional order PI controller is designed, which feeds the force compensation signal in position feedback loop of both actuators. Nelder-Mead (N-M) optimization technique is employed in order to optimally tune controller parameters based on the proposed performance criteria. To test the proposed controllers according to real flight condition, an external disturbance of higher amplitude that acts as airload is applied directly on the control surface. In addition, a disturbance signal function of system states is applied to check the robustness of proposed controller. Simulation results on nonlinear system model validated the performance of the proposed scheme as compared to optimal PID and high gain PID controllers.     

Dynamics modeling and control of a transport aircraft for ultra-low altitude airdrop

The nonlinear aircraft model with heavy cargo moving inside is derived by using the separation body method, which can describe the influence of the moving cargo on the aircraft attitude and altitude accurately. Furthermore, the nonlinear system is decoupled and linearized through the input–output feedback linearization method. On this basis, an iterative quasi-sliding mode(SM)flight controller for speed and pitch angle control is proposed. At the first-level SM, a global dynamic switching function is introduced thus eliminating the reaching phase of the sliding motion.At the second-level SM, a nonlinear function with the property of ‘‘smaller errors correspond to bigger gains and bigger errors correspond to saturated gains' ' is designed to form an integral sliding manifold, and the overcompensation of the integral term to big errors is weakened. Lyapunovbased analysis shows that the controller with strong robustness can reject both constant and time-varying model uncertainties. The performance of the proposed control strategy is verified in a maximum load airdrop mission.     

Non-affine parameter dependent LPV model and LMI based adaptive control for turbofan engines

The precise control of turbofan engines thrust is an important guarantee for an aircraft to obtain good flight performance and a challenge due to complex nonlinear dynamics of engines and time-varying parameters. The main difficulties lie in the following two aspects. Firstly, it is hard to obtain an accurate kinetic model for the turbofan engine. Secondly, some model parameters often change in different flight conditions and states and even fluctuate sharply in some cases. These variable parameters bring huge challenge for the turbofan engine control. To solve the turbofan engine control problem, this paper presents a non-affine parameter-dependent Linear Parameter Varying(LPV) model-based adaptive control approach. In this approach, polynomial-based LPV modeling method is firstly employed to obtain the basis matrices, and then the Radial Basis Function Neural Networks(RBFNN) is introduced for the online estimation of the non-affine model parameters to improve the simulation performance. LPV model-based Linear Matrix Inequality(LMI) control method is applied to derive the control law. A robust control term is introduced to fix the estimation error of the nonlinear time-varying model parameters for better control performance. Finally, the Lyapunov stability analysis is performed to ensure the asymptotical convergence of the closed loop system. The simulation results show that the states of the engine can change smoothly and the thrust of the engine can accurately follow the desired trajectory, indicating that the proposed control approach is effective. The contribution of this work lies in the combination of linear system control and nonlinear system control methods to design an effective controller for the turbofan engine and to provide a new way for turbofan engine control research.     

面向航空发动机推力控制的大气参数测量系统设计

为了实现多发飞机推力控制匹配要求,以及提升机载控制参数测量可靠性要求,设计了一套适用于多发飞机的机载环境大气参数测量系统。通过对发动机推力控制需求和适航相关要求的分析,确定了系统设计原则,利用飞机和发动机的有限硬件资源,提出了一种适用于多发飞机的多余度机载环境大气参数测量系统架构。针对不同来源的信号,分别设计了相应信号故障诊断算法、表决算法以及多源信号故障切换逻辑,保证系统在信号发生故障时可及时切换到健康余度。通过仿真和试验对测量系统在信号发生故障时的容错能力进行了验证,结果表明：系统余度设计合理,故障诊断和表决逻辑有效,环境大气参数测量的可靠性和安全性得到了提升;当信号发生故障时,可实现故障重构,且切换过程产生的推力变化小于3%。     

Stability analysis of parallel DC-DC converters

We develop analytic methodologies for stability analyses (using nonlinear and linear methodologies) of parallel dc-dc converters (under unsaturated and saturated operating conditions) using their switching model, discrete model (based on nonlinear map), and averaged model. We describe the approach for investigating the behavior of the stable and unstable equilibrium solutions of a parallel dc-dc converter under parametric variations and illustrate the methodology using a load-sharing dc-dc buck converter. For unsaturated operating condition, using bifurcation analysis and Floquet theory, we predict the stability boundary of the nominal solution, determine its postinstability dynamics, and investigate the dependence of the converter dynamics on its initial conditions. Subsequently, we demonstrate the differences in the predictions of the instabilities and instability boundaries using (conventional) linearized averaged (small-signal) and discrete and switching models.     

A necessary condition for effective performance of the multiplemodel adaptive estimator

Effective adaptive estimation for a general linear system driven by an input modeled by a randomly switching Gaussian process is considered. The performance of the multiple model adaptive estimator (MMAE) is, in some cases, unexpectedly hampered by a necessary condition not satisfied by the linear system. This key dependency for effective MMAE performance is based on a particular property of the DC gain of the linear system     

扩展分支分析方法在飞行动力学中的应用

将分支分析和突变理论方法扩展后,应用于飞机全包线范围内平衡特性的连续计算和稳定性分析,提出了以扩展分支分析方法为基础的反馈参数连续调参的控制律设计方法。研究结果表明,扩展分支分析方法不仅能获得飞行性能指标,而且可确定非线性飞行动力学系统的稳定特性,是综合进行性能计算、品质分析及控制律设计的一种有效方法。     

挠性航天器的退步直接自适应姿态跟踪控制

针对参数不确定的挠性航天器姿态跟踪控制问题,提出了一种退步直接自适应控制算法。首先验证了挠性航天器动力学子系统的近似严格正实性,并设计了具有理想控制性能的参考模型;然后对以姿态四元数描述的运动学子系统设计常系数输出反馈中间控制律,使航天器姿态四元数输出渐近跟踪参考模型输出;最后退一步,对具有参数不确定特性的动力学子系统,基于非线性直接自适应控制理论和Lyapunov稳定性理论,设计了退步直接自适应姿态跟踪控制器,并证明了闭环系统的稳定性。仿真结果表明,所提控制方法能有效抑制挠性附件的振动,对挠性航天器的控制是有效的。     

非线性反馈线性化方法在飞控系统中的应用

应用非线性反馈精确线性化方法进行了飞机自动着陆系统设计。首先,用非线性微分方程组表示的飞机纵向控制系统,在经过输入输出反馈线性化以后,可等效为线性系数;然后,用线性的ＰＩＤ控制方法对变换后的线性系统进行了设计;最后,考虑风的干扰,对所设计的飞机自动着陆控制系统进行了数字仿真。仿真结果表明,用反馈线性化方法设计的飞控系统具有良好的性能。     

A Gaussian Mixture PHD Filter for Jump Markov System Models

The probability hypothesis density (PHD) filter is an attractive approach to tracking an unknown and time-varying number of targets in the presence of data association uncertainty, clutter, noise, and detection uncertainty. The PHD filter admits a closed-form solution for a linear Gaussian multi-target model. However, this model is not general enough to accommodate maneuvering targets that switch between several models. In this paper, we generalize the notion of linear jump Markov systems to the multiple target case to accommodate births, deaths, and switching dynamics. We then derive a closed-form solution to the PHD recursion for the proposed linear Gaussian jump Markov multi-target model. Based on this an efficient method for tracking multiple maneuvering targets that switch between a set of linear Gaussian models is developed. An analytic implementation of the PHD filter using statistical linear regression technique is also proposed for targets that switch between a set of nonlinear models. We demonstrate through simulations that the proposed PHD filters are effective in tracking multiple maneuvering targets.     

无垂尾推力矢量飞机的自适应控制仿真研究

研究了采用自适应控制系统的无垂尾构型推力矢量飞机的飞行控制性能.论述了在有参数未知的情况,使用状态变量反馈可线性化的非线性系统的输出轨迹的控制问题,推导出了自适应控制律的设计方法.最后,针对算例飞机给出了仿真计算的结果,证实了在无垂尾构型推力矢量飞机上应用自适应控制系统的可行性.     

Active fault tolerant control for vertical tail damaged aircraft with dissimilar redundant actuation system

This paper proposes an active fault-tolerant control strategy for an aircraft with dissim-ilar redundant actuation system (DRAS) that has suffered from vertical tail damage. A damage degree coefficient based on the effective vertical tail area is introduced to parameterize the damaged flight dynamic model. The nonlinear relationship between the damage degree coefficient and the corresponding stability derivatives is considered. Furthermore, the performance degradation of new input channel with electro-hydrostatic actuator (EHA) is also taken into account in the dam-aged flight dynamic model. Based on the accurate damaged flight dynamic model, a composite method of linear quadratic regulator (LQR) integrating model reference adaptive control (MRAC) is proposed to reconfigure the fault-tolerant control law. The numerical simulation results validate the effectiveness of the proposed fault-tolerant control strategy with accurate flight dynamic model. The results also indicate that aircraft with DRAS has better fault-tolerant control ability than the traditional ones when the vertical tail suffers from serious damage.     

考虑扰流的舰载机终端进场线性模型

回收舰载机需要精确的终端路径和姿态控制,舰载机线性小扰动模型是这一阶段系统分析和控制器设计的必要工具,它需要足够准确地描述在主要操纵输入和进场路径大气紊流作用下舰载机的动态特性。首先使用代数线性化方法建立舰载机终端进场纵向运动的小扰动模型,仿真证明该模型能精确描述无风条件下进场舰载机对控制指令的响应,但通常的建模气流扰动影响的方法不能正确反映舰尾大气紊流对舰载机进场速度的干扰。针对该问题,重点研究了垂向风引起的进场舰载机轨迹方向上的力瞬变,提出了量化舰载机地速扰动的表达式以优化线性模型参数。最后,通过完成舰载机动力学模型在不同风场下的开环仿真以及在舰尾流场中的终端进场闭环仿真,验证了改进的线性模型的有效性,表明它适用于复杂流场下着舰控制系统的性能分析和设计。     

Non-fragile switched control for morphing aircraft with asynchronous switching

This paper deals with the problem of non-fragile linear parameter-varying (LPV) H∞ control for morphing aircraft with asynchronous switching.The switched LPV model of morphing aircraft is established by Jacobian linearization approach according to the nonlinear model.The data missing is taken into account in the link from sensors to controllers and the link from controllers to actuators,which satisfies Bernoulli distribution.The non-fragile switched LPV controllers are con structed with consideration of the uncertainties of controllers and asynchronous switching phenomenon.The parameter-dependent Lyapunov functional method and mode-dependent average dwell time (MDADT) method are combined to guarantee the stability and prescribed performance of the system.The sufficient conditions on the solvability of the problem are derived in the form of linear matrix inequalities (LMI).In order to achieve higher efficiency of the designing process,an algo rithm is applied to divide the whole set into subsets automatically.Simulation results are provided to verify the effectiveness and superiority of the method in the paper.     

超机动飞行的非线性反推自适应控制

为解决对象参数未知时的超机动飞行控制问题,设计了一种非线性反推自适应控制器。针对超机动飞行的非线性模型,适当选取Lyapunov函数和中间虚拟控制信号,同时通过自适应控制律的设计来调节未知参数并得到了最终的控制信号。仿真结果表明,即使模型参数未知,所设计的控制律也能在过失速机动条件下控制飞机跟踪指令飞行,同时保证了闭环系统的稳定性。     

基于BACKSTEPPING理论的直接自适应飞行控制

BACKSTEPPING理论是继反馈线性化理论之后发展起来的一种的控制理论.基于BACKSTEPPING理论的控制系统是通过Lyapunov稳定性理论推导得出,确保了系统闭环稳定性,避免了反馈线性化理论在飞机控制系统中应用存在的可能不稳定的隐患.然而,BACKSTEPPING理论与反馈线性化方法存在同样的鲁棒性缺陷,即对模型的精确性要求很严格.据此文中给出一种通过直接自适应补偿的方式来增强其鲁棒性的方法.仿真结果表明此方案对模型存在不精确环节时有较强的补偿控制作用.     

不确定性非线性系统的自适应输出反馈控制

研究了一种不确定性非线性系统的自适应输出反馈控制方法.首先引入伪控制信号使系统反馈线性化,然后设计一个线性动态补偿器和在线神经网络,自适应消除不确定性和建模所引起的误差.仿真结果表明,该控制方法能够消除系统的稳态误差,提高系统动态性能,并且具有较好的鲁棒性.     

间隙非线性气动弹性系统的辨识

间隙非线性气动弹性系统有非常丰富的动力学特征。由于工程实际中间隙不易准确测量甚至无法测量,通常需要通过辨识来建立其数学模型,其中间隙开关点位置是辨识问题中的难点。本文利用间隙开关点将间隙非线性系统区分为3个线性子系统,用Hammerstein模型表示其非线性部分,构造了开关点的迭代序列;并采用非迭代和迭代相结合的方法进行求解,从而成功获得包含间隙开关点在内的该系统所有模型参数;以间隙非线性的二元翼段为例,验证了该辨识方法的有效性。