小型无人机舵面故障的控制重构设计

小型无人机一般采用单余度设计,舵面故障后重构控制只能根据系统解析冗余进行设计,传统辨识方法复杂而且往往不能满足无人机重构控制的实时性。对由于舵面故障多样性引起的无人机参数大范围跳变进行分析,采用基于线性模型的方法离线重构控制器参数,实际飞行中在线自适应选择控制律,并针对存在大扰动的重构过程设计了动态补偿方案,保证无人机在故障发生后重构完成前的过渡过程的安全性。仿真实验表明,该方法能满足无人机舵面故障时控制律重构的实时性要求,保证过渡过程平稳,而且基于线性模型的控制器设计方法简便,工程实用性强。     

基于扩展$L_1$自适应的战斗机大迎角非线性控制

针对常规动态逆控制对系统不确定性较为敏感的缺点,提出一种扩展$L_1$自适应控制方法,用于战斗机大迎角非线性控制.采用时标分离原理将控制系统分为内外两个回路,分别设计动态逆控制器作为基本控制器,用于角速率和角度的跟踪控制.设计$L_1$自适应控制器作为扩展控制器,用于抵消系统中的不确定性.分别在标称和加入参数摄动的情况下进行仿真验证与对比,仿真结果表明所提出的控制方法能够有效抵消系统中的不确定性,提高控制效果.     

基于NDOB的匹配/非匹配不确定性系统滑模控制

针对一类n阶匹配与非匹配不确定性和扰动共存的系统,提出了一种新颖的基于非线性干扰观测器的滑模控制方法。将非匹配扰动的估计值融入到滑模面,设计了集成扰动观测的滑模控制。与传统的滑模控制方法相比,该方法在匹配与非匹配不确定性和扰动出现时具有较好的抑制能力,并能有效地抑制切换增益所引起的抖振现象。利用李雅普诺夫理论和输入-输出稳定性概念严格证明了闭环系统的稳定性。最后通过两个仿真实例验证了所提控制方法的有效性。     

非匹配不确定系统的自适应反演准滑模控制

对于一类n阶非线性系统,提出一种自适应反演准滑模控制方法,控制的前n-1步采用自适应反演算法消除非匹配不确定性的影响,在最后一步,为改进跟踪效果,结合了可变边界层的思想,设计了准滑模控制方法,达到系统的n个状态快速收敛的目的.最终系统中不满足匹配条件的部分也具有较好的鲁棒性.与自适应反演线性滑模方法相比具有更好的跟踪性,理论分析证明了控制系统在削弱抖振的同时也能保证稳态精度,仿真实验证明了该方法的可行性.     

基于改进混沌神经网络的飞机舵面故障预测研究

结合混沌序列的相空间重构理论和BP神经网络预测理论,构建了一个基于时间序列预测的混沌神经网络模型;考虑基本BP神经网络采用的梯度学习算法收敛速度较慢的缺点,文章利用改进的Levenberg-Marquart(L-M)优化学习算法对网络进行训练;最后对一组飞机舵面卡死故障数据进行仿真实验,结果表明该模型不仅提高了预测精度,而且网络收敛速度也得到明显的改善,有效避免神经网络局部极小问题,可以较好地对飞机舵面卡死故障进行预测.     

推力矢量飞机鲁棒故障检测与辨识和指令滤波容错控制系统设计

针对推力矢量飞机(TVA)在超机动飞行中的舵面故障、执行器故障、参数摄动和外界干扰等问题,提出了一种鲁棒故障检测与辨识和指令滤波容错控制(RFDI-CFFTC)系统设计方法.首先针对TVA故障模型提出了一种基于多观测器的RFDI机制,通过引入自适应律和观测器来补偿参数摄动和外界干扰的影响,实现对舵面故障和执行器故障的准...     

非匹配不确定性影响下的无人车路径跟踪控制

针对无人车在非匹配不确定性影响下的路径跟踪控制问题,设计一种基于线性矩阵不等式（LMI）的滑模控制器.首先,根据车辆运动学和动力学方程,同时考虑轮胎侧滑造成的不确定性、车辆侧偏约束以及随机干扰影响,建立车辆非线性不确定系统模型;然后,提出一种线性滑模路径跟踪控制方法,给出线性滑模面存在的充分条件,并推导出线性滑模面存在的显式公式,以保证约束于该滑模面的降阶等价系统的二次稳定性;最后,在SerretFrenet坐标系下验证车辆单、双移线运动时的路径跟踪控制效果.仿真结果表明,所设计的滑模控制器可以保证对参考路径的稳定跟踪,具有较强的鲁棒性.     

一类非匹配不确定性系统的变结构控制

研究一类非匹配不确定性系统的变结构控制问题. 引入适当的状态变换, 将非匹配不确定系统描述成具有分级形式的两个子系统. 在保证第一个子系统二次渐近稳定的条件下, 利用线性矩阵不等式方法得到第二个状态变量的期望值, 并由第二个状态变量与其期望值之差构造滑动模, 并利用滑模运动的到达条件, 得到变结构控制律.     

一类非匹配不确定性系统的变结构控制

研究一类非匹配不确定性系统的变结构控制问题.引入适当的状态变换,将非匹配不确定系统描述成具有分级形式的两个子系统.在保证第一个子系统二次渐近稳定的条件下,利用线性矩阵不等式方法得到第二个状态变量的期望值,并由第二个状态变量与其期望值之差构造滑动模,并利用滑模运动的到达条件,得到变结构控制律.     

Passivity-based event-triggered fault tolerant control for VTOL with actuator failure and parameter uncertainties

This paper investigates passivity based fault tolerant control (FTC) for Vertical Take-off and Landing aircraft system subject to actuator failure under event-driven transmission mechanism. Firstly, a polytopic model is proposed to describe the aircraft dynamics with parameter uncertainties, which is more general in practice. In order to process the lose efficacy of actuator, the failure of actuator is modelled as multiplicative fault model. In addition, the hybrid event trigger transmission mechanism is introduced in FTC to save communication resource. The proposed design method not only ensures the closed-loop system is strictly passive with a prescribed passivity performance index, but also gets rid of Zeno phenomenon fundamentally, which may exist in continuous event trigger scheme. Finally, simulation results are presented to show the validity and application of the proposed method.     

Passive actuator fault tolerant control for a class of MIMO nonlinear systems with uncertainties

Fault tolerant control of affine class of multi-input multi-output (MIMO) nonlinear systems has not received considerable attention of researchers compared to other class of nonlinear systems. Therefore, this paper proposes an adaptive passive fault tolerant control method for actuator faults of affine class of MIMO nonlinear systems with uncertainties using sliding mode control . The actuator fault is represented by a multiplicative factor of the control signal which reflects the loss of actuator effectiveness. The design of the controller is based on the assumption that the maximum loss level of the actuator effectiveness is known. Furthermore, since the proposed controller is adaptive, it does not require any a-priori knowledge of the uncertainty bounds. The closed-loop stability conditions of the controller are derived based on Lyapunov theory. The effectiveness of the proposed controller is demonstrated considering two examples: a two degree of freedom helicopter and a two-link robot manipulator and has been found to be satisfactory.     

Robust adaptive fault tolerant control for a process with actuator faults

This paper studies design and implementation of an enhanced multivariable adaptive control scheme for an uncertain nonlinear process exposed to actuator faults. For adaptive fault compensation, a model reference adaptive control (MRAC) strategy is utilized as main controller. A new adaptation algorithm making possible to improve transient performance of adaptive control is integrated to the controller. With the help of further modifications, some restrictive conditions on multivariable adaptive design are relaxed so that the system requires less plant information. The resulting controller has a simpler structure than the other matrix factorization based controllers. At the final stage of design, a robust adaptive control scheme is obtained with consideration of practical implementation problems such as sensor noises, external disturbances and unmodeled​ system dynamics. It is proved that the controller guarantees closed-loop signal boundedness and asymptotic output tracking. Real-time experiment results acquired from quadruple tank benchmark system are presented in order to exhibit the effectiveness of the proposed scheme.     

Differential geometry based active fault tolerant control for aircraft

This work shows how to use a differential geometry tool to design a novel nonlinear active fault tolerant flight control system for aircraft. The proposed control scheme consists of two main subsystems: a controller, which is designed for the nominal plant, and a fault detection and diagnosis module, which provides fault estimation. A further feedback loop exploits the fault estimation to accommodate faults affecting the system. The estimate convergence and the stability of the active fault tolerant flight controller are theoretically proved. Finally, high fidelity simulations show the effectiveness of the scheme.     

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.     

Active fault tolerant control for nonlinear systems with simultaneous actuator and sensor faults

The goal of this paper is to describe a novel fault tolerant tracking control (FTTC) strategy based on robust fault estimation and compensation of simultaneous actuator and sensor faults. Within the framework of fault tolerant control (FTC) the challenge is to develop an FTTC design strategy for nonlinear systems to tolerate simultaneous actuator and sensor faults that have bounded first time derivatives. The main contribution of this paper is the proposal of a new architecture based on a combination of actuator and sensor Takagi-Sugeno (T-S) proportional state estimators augmented with proportional and integral feedback (PPI) fault estimators together with a T-S dynamic output feedback control (TSDOFC) capable of time-varying reference tracking. Within this architecture the design freedom for each of the T-S estimators and the control system are available separately with an important consequence on robust L ₂ norm fault estimation and robust L ₂ norm closed-loop tracking performance. The FTTC strategy is illustrated using a nonlinear inverted pendulum example with time-varying tracking of a moving linear position reference.     

Dynamic surface active fault tolerant control design for the attitude control systems of UAV with actuator fault

In this paper, an active fault tolerant control (FTC) approach based on transient performance index is proposed for the attitude control systems of unmanned aerial vehicle (UAV) with actuator fault. The nonlinear attitude control system model for UAV with actuator faults is given, which represents the dynamic characteristics of UAV. A fault diagnosis component is used for fault detection and estimation. According to the fault estimation information obtained during the fault diagnosis, the fault tolerant control scheme is developed by adopting the adaptive dynamic surface control technique, which guarantees the asymptotic output tracking and ultimate uniform boundedness of the closed-loop attitude control systems of UAV in actuator faulty case. Further, a prescribed transient performance of the FTC attitude control systems is considered which characterizes the convergence rate and maximum overshoot of the attitude tracking error. Finally, simulation results are shown that the attitude control system states remain bounded and the output tracking errors converge to a neighborhood of zero.     

Reduction of matched and unmatched uncertainties for a class of nonlinear perturbed systems via robust control

The aim of this paper is to design a robust control for stabilization of a class of nonlinear perturbed system subject to matched and unmatched disturbances. Here, the concept of dynamic sliding mode control and the attractive ellipsoid method advantages are used to design a robust nonlinear control algorithm, which reduces considerably the perturbation effects. Hence, in finite time, the dynamic sliding mode control brings the system trajectory to a specific configuration. After this time, the controller reduces the perturbation effects by using the high‐gain control obtained in the attractive ellipsoid method. Thus, based on the solution of a specific matrix inequality, the feedback control of the system guarantees that the trajectory will be stabilized in the ultimate uniform bounded sense. To illustrate the theoretical results, a numerical example with a comparative study is introduced. Finally, the performance of the controller designed in this paper is tested on an electromechanical real‐time system.     

Generation of stable oscillations in uncertain nonlinear systems with matched and unmatched uncertainties

ABSTRACT

In this paper, a robust limit cycle control technique is proposed for generation of stable oscillations in a class of uncertain nonlinear systems with both matched and unmatched uncertainties. For this purpose, first, the modified Lyapunov function is introduced which is appropriate for stability analysis of invariant sets (instead of equilibrium points). The structure of the proposed Lyapunov function is related to the shape of the desirable limit cycle. Next, in order to design the robust limit cycle control input, the backstepping and Lyapunov redesign methods are employed, simultaneously. The The classical Lyapunov redesign controller is discontinuous and robust with respect to matched uncertainties. To overcome unmatched uncertainties, a modified version of the Lyapunov redesign controller is suggested in each step of backstepping which results in a continuous robust control law. Furthermore, the convergence of the phase trajectories of the uncertain closed-loop system to the target limit cycle is proved using the extended Lyapunov stability theorem. Finally, computer simulations are performed to show the applicability of the given approach. In this regard, two uncertain nonlinear practical systems are considered and robust stable oscillations are generated in these systems via the proposed controller. Simulation results confirm the effectiveness of the proposed technique.     

A virtual actuator and sensor approach for fault tolerant control of LPV systems

In this paper, a fault tolerant control (FTC) strategy using virtual actuators and sensors for linear parameter varying (LPV) systems is proposed. The main idea of this FTC method, initially developed for LTI systems, is to reconfigure the control loop such that the nominal controller could still be used without need of retuning it. The plant with the faulty actuator/sensor is modified adding the virtual actuator/sensor block that masks the actuator/sensor fault. The suggested technique is an active FTC strategy that reconfigures the virtual actuator/sensor on-line taking into account faults and operating point changes. The stability of the reconfigured control loop is guaranteed if the faulty plant is stabilizable/detectable. The LPV virtual actuator/sensor is designed using polytopic LPV techniques and linear matrix inequalities (LMIs). A two-tank system simulator is used to assess the performance of the proposed method. In particular, it is shown that the application of the proposed technique results in an improvement, in terms of performance, with respect to the LTI counterpart.