四旋翼无人机姿态系统的非线性容错控制设计

本文研究了四旋翼无人机执行器发生部分失效时的姿态控制问题.通过分析其动力学特性,将执行器故障以乘性因子加入系统模型,得到执行器故障情况下四旋翼无人机的姿态动力学模型.在同时存在未知外部扰动和执行器故障的情况下,设计了一种基于自适应滑模控制的容错控制器.利用基于Lyapunov的分析方法证明了所设计控制器的渐近稳定性.在四旋翼无人机实验平台上进行了实验,验证了该算法对存在未知外部扰动和执行器部分失效时四旋翼无人机的姿态控制具有较好的鲁棒性.     

倾转式三旋翼无人机的有限时间收敛控制设计

倾转式三旋翼无人机是一种多旋翼无人机的特殊构型,其兼具单旋翼无人机与普通多旋翼无人机的特点.目前对于此类无人机的鲁棒控制设计研究成果较少,多数已有的控制方法未考虑模型参数的不确定性与外界扰动对此类无人机控制的影响.为此本文针对倾转式三旋翼无人机动力学模型存在的转动惯量未知,以及飞行中受到未知外界扰动影响的情况,基于super-twisting算法,设计了一种新型非线性鲁棒控制方法.通过基于Lyapunov的稳定性分析方法,证明了闭环系统的稳定性,并得到在有限时间内三旋翼无人机的姿态跟踪误差收敛的结果.本文中所提出的控制算法,在倾转式三旋翼无人机实验平台上进行了实时飞行控制实验,取得了较好的控制效果.     

一种小型倾转旋翼无人机的建模与仿真

传统无人机多为四旋翼无人机和固定翼无人机,现设计一种小型可倾转旋翼无人机,可实现垂直起降与悬停,并能在空中高速巡航。建立该无人机的动力学模型,对该无人机的旋翼飞行模式,设计了基于滑模控制(Sliding Mode Control)的姿态控制器和位置控制器,并通过Matlab仿真和传统的PID算法进行比较验证。仿真结果表明:基于滑模鲁棒控制的无人机,其姿态收敛过程和位置收敛过程都远快于传统控制方法。     

四倾转旋翼无人机无源控制与飞行实验

倾转旋翼无人机以低速悬停以及快速巡航能力得到了大量的关注,但是其变化的飞行器结构(旋翼的倾转)以及较强的非线性特性(飞行速度的大范围变化)都增大了飞行控制的难度.针对一种四倾转旋翼无人机的飞行控制问题,本文中的研究内容主要基于无源性概念,改进了互联和阻尼分配无源控制以提出此飞行器的姿态与高度控制方法.通过对于飞行器动力学模型的公式化,其姿态与位置模型均可表示为端口受控哈密尔顿算子模型形式,模型中的旋翼倾转角度被格外关注以实现对于飞行模式过渡时动力学特性的分析与简化.根据上述模型简化,改进且包含积分作用的互联和阻尼分配无源控制被用于进行姿态与高度控制器设计,基于无源性概念可进行进一步的稳定性分析.最终,仿真对比实验与包含飞行模式过渡的巡航飞行实验验证了所提出控制方法的有效性.     

多无人机编队递归非奇异终端滑模容错控制

为解决四旋翼无人机编队飞行过程中易受到外部干扰、空气阻力、执行器故障等不确定因素影响的问题,提出了一种基于补偿函数观测器(CFO)的递归非奇异终端滑模控制(RNTSMC)方法来提高四旋翼无人机编队系统性能。首先,引入具有高精度估计的补偿函数观测器,实时估计外部干扰、执行器故障等信息,通过设计递归积分终端滑模面改进非奇异终端滑模面等效控制器对估计信息进行补偿控制,并给定滑模面初始值,保证两滑模面依次连续到达平衡点,确保跟踪误差在有限的时间内快速收敛到0。其次,根据长机-僚机法建立编队模型,基于滑模控制理论,设计编队协同控制器,保证无人机编队完成飞行任务。最后,通过对比仿真结果表明,该方法对四旋翼无人机编队具有良好的容错性能。     

倾转式三旋翼无人机非线性鲁棒控制设计与实验验证

针对倾转式三旋翼无人机的建模及控制设计问题,本文通过对此类无人机动力学特性的分析,构造了以电机转速和尾舵倾角作为控制输入的动力学模型.为补偿动力学模型中未知的外部扰动及参数不确定性,设计了一种非线性自适应鲁棒控制策略.在此基础上,基于Lyapunov分析方法及Barbalat引理证明了所设计控制器的闭环系统稳定性,以及误差渐近收敛性.最后通过半实物仿真平台进行了实验验证.实验结果表明,本文中提出的控制策略对倾转式三旋翼无人机外部扰动及参数不确定性具有较好的鲁棒性.     

倾转式三旋翼无人机非线性鲁棒控制设计与实验验证

针对倾转式三旋翼无人机的建模及控制设计问题,本文通过对此类无人机动力学特性的分析,构造了以电机转速和尾舵倾角作为控制输入的动力学模型.为补偿动力学模型中未知的外部扰动及参数不确定性,设计了一种非线性自适应鲁棒控制策略.在此基础上,基于Lyapunov分析方法及Barbalat引理证明了所设计控制器的闭环系统稳定性,以及误差渐近收敛性.最后通过半实物仿真平台进行了实验验证.实验结果表明,本文中提出的控制策略对倾转式三旋翼无人机外部扰动及参数不确定性具有较好的鲁棒性.     

三倾转旋翼无人机直升机模式建模与控制研究

针对一种新型三旋翼构型的倾转旋翼无人机的直升机模式控制问题进行研究,采用牛顿欧拉法对这种新型三旋翼构型的倾转旋翼无人机直升机模式进行了详细的动力学建模分析,建立了该无人机悬停模式6自由度非线性模型;在对该模型进行线性化的基础上,设计了这种三倾转旋翼无人机直升机模式下的高度、俯仰通道、滚转通道以及偏航通道的PID控制器,并在Matlab/Simlink环境下建立其仿真模型,对所设计的控制算法进行验证;实验结果表明,所设计的控制器能够满足系统的控制性能要求。     

一种可倾斜六旋翼无人机容错控制方法

常规六旋翼无人机在单个旋翼完全失效后, 存在姿态与高度不完全可控的情况, 此时采取降级控制策略会 使无人机失去静态悬停能力. 针对此问题, 本文提出了一种可倾斜旋翼的容错控制方法, 在经典旋翼结构布局的基 础之上, 将其中一个旋翼设计成可倾斜结构, 通过倾斜角度的改变与控制分配重构, 无人机在任意单个旋翼完全失 效后均能保持力与力矩的平衡. 利用线性规划方法得到无人机的可达力矩集, 同时对电机饱和度进行分析, 确定了 不同旋翼失效后的最优倾斜角. 搭建飞行测试平台进行对比验证, 实验结果表明, 本文提出的方法具有良好的容错 效果与鲁棒性, 能够保证六旋翼无人机在故障后的稳定飞行与平稳降落.     

具有执行器故障的四旋翼无人机有限时间容错控制

本文主要研究了四旋翼无人机在外部干扰、执行器存在部分失效和偏置故障并发情况下有限时间轨迹跟踪的控制问题. 通过分析四旋翼无人机动力学特性, 构建了带有外部干扰、执行器机构故障的动力学模型. 基于鲁棒全局快速终端滑模控制算法, 设计了一种有限时间容错控制器, 提高了系统对故障的响应速度. 其次, 针对常值/时变故障和干扰,在控制器设计中采用改进的连续函数进行补偿, 减少了由切换函数引起的系统抖振, 并基于Lyapunov函数对控制器的稳定性进行了分析. 最后, 通过仿真实验验证了所设计控制器的有效性和可靠性, 同时存在执行器故障和外部干扰的情况下, 无人机能够实现较好的轨迹跟踪性能.     

Adaptive logic‐based switching fault‐tolerant controller design for nonlinear uncertain systems

This paper deals with the problem of fault‐tolerant control (FTC) for a class of nonlinear uncertain systems against actuator faults using adaptive logic‐based switching control method. The uncertainties under consideration are assumed to be dominated by a bounding system which is linear in growth in the unmeasurable states but can be a continuous function of the system output, with unknown growth rates. Several types of common actuator faults, e.g., bias, loss‐of‐effectiveness, stuck and hard‐over faults are integrated by a unified fault model. By utilizing a novel adaptive logic‐based switching control scheme, the actuator faults can be detected and automatically accommodated by switching from the stuck actuator to the healthy or even partly losing‐effectiveness one with bias, in the presence of large parametric uncertainty. In particular, two switching logics for updating the gain in the output feedback controllers are designed to ensure the global stability of the nominal (fault‐free) system and the boundedness of all closed‐loop signals of the faulty system, respectively. Two simulation examples of an aircraft wing model and a single‐link flexible‐joint robot are given to show the effectiveness of the proposed FTC controller. Copyright © 2010 John Wiley & Sons, Ltd.     

飞翼无人机复合连续非奇异终端滑模姿态跟踪容错控制

本文针对受多源干扰和舵面故障影响的飞翼无人机系统姿态跟踪控制问题进行研究, 提出了一种基于高阶滑模观测器的复合连续非奇异终端滑模主动抗干扰容错控制算法, 在实现姿态跟踪误差有限时间收敛的同时, 保证了控制量的连续. 并且针对控制力矩的具体实现问题, 结合飞翼无人机气动舵面冗余特性, 给出了基于加权伪逆算法的舵面分配方案, 该方案在满足舵面约束的情况下, 保证了舵面偏转角度的最优. 仿真结果表明, 所提控制方案显著提升了飞翼无人机姿态跟踪精度和跟踪误差的收敛速度, 并且保证了所有舵面满足偏角约束.     

Robust Actuator‐Fault‐Tolerant Control System Based on Sliding‐Mode Observer for Thrust‐Vectoring Aircrafts

In this paper, a robust actuator‐fault‐tolerant control (FTC) system is proposed for thrust‐vectoring aircraft (TVA) control. To this end, a TVA model with actuator fault dynamics, disturbances, and uncertain aerodynamic parameters is described, and a local fault detection and identification (FDI) mechanism is proposed to locate and identify faults, which utilizes an adaptive sliding‐mode observer (SMO) to detect actuator faults and two SMOs to identify and estimate their parameters. Finally, a fault‐tolerant controller is designed to compensate for these actuator faults, disturbances, and uncertain aerodynamic parameters; the approach combines back‐stepping control with fault parameters and a high‐order SMO. Furthermore, the stability of the entire control system is validated, and simulation results are given to demonstrate the effectiveness and potential for this robust FTC system.     

基于神经网络观测器的飞控传感器在线故障诊断

为提高无人机飞行安全可靠性,针对飞行控制系统中常出现的传感器故障以及非线性气动力模型参数难以确定的问题,提出了基于BP神经网络观测器估计的故障诊断方法;引用LM改进算法对网络参数进行调整,构造了神经网络观测器模型逼近非线性系统,并运用于飞行控制系统进行在线数字仿真,对垂直陀螺输出卡死故障、恒偏差故障和恒增益故障分别进行仿真分析;仿真结果表明,所设计神经网络观测器可以有效估计系统输出,在线诊断传感器故障。     

Sliding‐mode fault‐tolerant control using the control allocation scheme

This paper is devoted to the design of a novel fault‐tolerant control (FTC) using the combination of a robust sliding‐mode control (SMC) strategy and a control allocation (CA) algorithm, referred to as a CA‐based sliding‐mode FTC (SMFTC). The proposed SMFTC can also be considered a modular‐design control strategy. In this approach, first, a high‐level SMC, designed without detailed knowledge of systems' actuators/effectors, commands a vector of virtual control signals to meet the overall control objectives. Then, a CA algorithm distributes the virtual control efforts among the healthy actuators/effectors using the real‐time information obtained from a fault detection and reconstruction mechanism. As the underlying system is not assumed to have a rank‐deficient input matrix, the control allocator module is visible to the SMC module resulting in an uncertainty. Hence, the virtual control, in this scheme, is designed to be robust against uncertainties emanating from the visibility of the control allocator to the controller and imperfections in the estimated effectiveness gain. The proposed CA‐based SMFTC scheme is a unified FTC, which does not need to reconfigure the control system in the case of actuator fault or failure. Additionally, to cope with actuator saturation limits, a novel redistributed pseudoinverse‐based CA mechanism is proposed. The effectiveness of the proposed schemes is discussed with a numerical example.     

Unified FDI and FTC Scheme for Air Path Actuators of a Diesel Engine Using ISM Extended with Adaptive Part

A unified fault detection and isolation (FDI) and fault tolerant control (FTC) strategy for the diesel engine's air management system has been formulated. Diesel engines need to comply with the strict emission requirements for which they are equipped with specialized sub‐systems for the purpose, such as the variable geometry turbo (VGT) charger and exhaust gas recirculation (EGR). Hardware‐based controls tend to make the system more complex and prone to structured and unstructured faults. This calls for an advanced FTC technique that can ensure desired level of emissions even in the presence of minor system malfunctions. The scheme proposed in this paper detects, isolates and estimates the structured faults and minimizes their effects by re‐positioning the actuators using integral sliding mode (ISM) control. Estimating the magnitude of structured faults help to reduce the ISM controller gains, eventually reducing the chattering. The stability of the system is analyzed using Lyapunov stability criterion. Simulations have been performed using fully validated industrial scale model of a diesel engine to elucidate the effectiveness of our scheme.     

Fault‐tolerant control synthesis for a class of nonlinear systems: Sum of squares optimization approach

This paper studies the fault‐tolerant control (FTC) problem for nonlinear systems, with guaranteed cost or H_∞ performance objective in the presence of actuator faults. The faulty mode is built as a multi‐model framework of the typical aberration in actuator effectiveness. The novelty of this paper is that the effect of the nonlinear terms is described as an index in order to transform the FTC design problem into a semi‐definite programming. The proposed optimization approach is to find zero optimum for this index. Combined with other performance indexes, the conceived multi‐objective optimization problem is solved by using sum of squares method in a reliable and efficient manner. Numerical examples are included to verify the applicability of this new approach for the nonlinear FTC synthesis. Copyright © 2008 John Wiley & Sons, Ltd.     

Observer‐based fault‐tolerant control for a class of hybrid impulsive systems

This paper investigates the fault‐tolerant control (FTC) problem for a class of hybrid nonlinear impulsive systems. Two kinds of faults are considered: continuous faults that affect each mode and discrete faults that affect the impulsive switching. The FTC strategy is based on the trade‐off between the frequency of switching and the decreasing rate of Lyapunov functions along the solution of the system, which maintains the stability of overall hybrid impulsive systems in spite of these two kinds of faults. A switched reluctance motor example is taken to illustrate the applicability of the proposed method. Copyright © 2009 John Wiley & Sons, Ltd.