马尔可夫跳变系统基于观测器的有限时间容错控制

针对具有一般不确定转移速率的单边Lipschitz Markovian跳变系统,设计了有限时间故障估计观测器和容错控制器.首先,提出一种自适应的有限时间故障估计观测器,它对未知输入具有鲁棒性,能够同时估计出系统的状态、执行器故障和传感器故障,并确保了误差系统的H_∞有限时间有界.然后,基于所估计的状态和执行器故障,提出一种有限时间故障容错控制方法确保闭环系统H_∞有限时间有界.通过线性矩阵不等式的形式,给出了所设计的有限时间观测器和控制器存在的充分条件.最后,通过一个仿真实例,验证了所提方法的有效性.     

转移概率部分未知时滞跳变系统有限时间控制

时滞是许多工业系统的固有特性,会导致系统控制性能的下降,甚至影响系统稳定,而在实际系统中,有限时间系统的特性更值得关注。针对上述情况,对一类具有时滞的马尔可夫跳变系统有限时间控制器设计的问题进行了研究。把转移概率完全已知的条件放宽至部分未知的更一般情形,采用自由权重的方法,保证所得的线性矩阵不等式具有更小的保守性。首先,给出马尔科夫跳变系统有限时间有界性、有限时间 H无穷有界性的判定准则。然后,通过对线性矩阵不等式(LMIs)求解,获得状态观测器和状态反馈控制器的增益矩阵。最后,仿真实例验证所提算法的有效性。     

线性描述系统有限时间函数观测器设计及存在性讨论

本文针对线性描述系统研究了其有限时间函数观测器的设计方法和存在条件.首先,通过构造两个结构上完全相同的渐近收敛观测器得到了一个新的有限时间函数观测器,它可以在任意给定的时间内达到对目标函数的精确估计,且估计精度和收敛时间不依赖于原系统的初始条件.随后,对该函数观测器的存在条件进行了详细讨论,给出了函数观测器存在的充分必...     

Interval estimation for uncertain systems with time-varying delays

The estimation problem for uncertain time-delay systems is addressed. A design method of reduced-order interval observers is proposed. The observer estimates the set of admissible values (the interval) for the state at each instant of time. The cases of known fixed delays and uncertain time-varying delays are analysed. The proposed approach can be applied to linear delay systems and nonlinear time-delay systems in the output canonical form. It involves the properties of quasi-monotone/Metzler/cooperative systems. In this framework, it is shown that if under a suitable coordinate transformation the delay-free subsystem is cooperative, then the delayed estimation error dynamics inherits this property. The conditions to find the observer gains are formulated in the form of LMI. The framework efficiency is demonstrated on examples of nonlinear systems.     

Reset observer-based fault tolerant control for a class of fuzzy nonlinear time-delay systems

The problem of actuator fault estimation and observer-based fault tolerant control for a class of nonlinear time-delay systems using Takagi-Sugeno (T-S) fuzzy models is investigated. The introduction of the reset element in the observer can decrease the overshooting and settling time of the estimation process. The observer to be designed is assumed to have norm-bounded gain perturbations. Based on Lyapunov–Krasovskii approach, the existence of adaptive reset observer and the fault tolerant controller with guaranteed asymptotical stability are synthesized. All the obtained results are given in the form of linear matrix inequalities (LMIs). Finally, the proposed fuzzy reset observer is applied to Chua's chaotic system and a two-stage chemical reactor with delayed recycle streams. So, the effectiveness of the proposed method is tested by simulation.     

Smooth sliding-mode observers for specific growth rate and substrate from biomass measurement

This paper addresses the estimation of specific growth rate and substrate concentration from biomass measurements in fermentation processes. Specifically, sliding-mode observers are proposed, for which finite-time global convergence is demonstrated using Lyapunov stability theory and concepts of variable structure systems. Two observers are developed for specific growth rate estimation, one producing a discontinuous estimation which is used afterwards for substrate estimation, and the other one – based on high-gain observers – that generates a smooth estimation with first-order dynamics and finite-time bounded convergence error. In the case of substrate estimation, an observer that increases the convergence rate to a vicinity of the real substrate concentration while achieving asymptotic convergence despite kinetic model uncertainties in properly excited processes is designed. This observer also exhibits first-order dynamics.     

线性连续时间时滞系统的有限时间有界跟踪控制

研究一类线性连续时间时滞系统的有限时间有界跟踪控制问题.首先,采用预见控制理论中求导的方法构造带有时滞的误差系统,把误差信号的信息包含在误差系统的状态向量中,再将其作为误差系统的输出向量;其次,通过为误差系统设计一个有记忆的状态反馈控制器,把问题转化为研究带有时滞的误差系统的闭环系统输入-输出有限时间稳定问题;再次,借鉴输入-输出有限时间稳定的研究方法和线性矩阵不等式的方法, 通过构造Lyapunov-Krasovskii函数,给出由一组线性矩阵不等式表征的控制器增益矩阵的设计方法,由此得到原系统的一个有限时间有界跟踪控制器;最后,通过一个数值实例验证所设计的控制器的有效性和优越性.     

Robust Finite-time <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> Control of Linear Time-varying Delay Systems with Bounded Control via Riccati Equations

In this paper, we will present new results on robust finite-time H_∞ control for linear time-varying systems with both time-varying delay and bounded control. Delay-dependent sufficient conditions for robust finite-time stabilization and H_∞ control are first established to guarantee finite-time stability of the closed-loop system via solving Riccati differential equations. Applications to finite-time H_∞ control to a class of linear autonomous time-delay systems with bounded control are also discussed in this paper. Numerical examples are given to illustrate the effectiveness of the proposed method.     

A sliding mode observer design for uncertain fractional Ito stochastic systems with state delay

This paper addresses the robust observer design problem for uncertain time-delay fractional Ito stochastic systems. A sliding surface is proposed and it is shown that state estimates converge towards it and remain there for the subsequent time. Additionally, by constructing a novel Lyapunov functional, a sufficient condition for the stability of the sliding motion of the estimated states is given in the form of Linear Matrix Inequalities (LMIs). It is demonstrated that the state estimates are stabilizable in probability provided that the LMI is feasible. Moreover, a finite-time sliding mode control law based on the estimated states is proposed. Simulation examples are given to show the validity and effectiveness of the results.     

An output delay approach to fault estimation for sampled-data systems

The problem of fault estimation for a class of non-uniformly sampled-data systems is investigated from the time delay point of view in this paper.Firstly,the output delay approach is employed to model the sampled-data system as a continuous-time one with time-varying delay output.Then,based on the analysis of the inapplicability of the adaptive fault diagnosis observer in such class of time-delay systems,a novel augmented fault estimation observer design method is proposed to guarantee the exponential convergence of the estimation errors.Furthermore,an extension to the case of time varying fault estimation for the noisy sampled-data systems is studied.Finally,simulation results of a flight control system are presented to demonstrate the effectiveness of the proposed method.     

Finite-Time Observers: Application to Secure Communication

In this paper, control theory is used to formalize finite-time chaos synchronization as a nonlinear finite-time observer design issue. This paper introduces a finite-time observer for nonlinear systems that can be put into a linear canonical form up to an output injection. The finite-time convergence relies on the homogeneity properties of nonlinear systems. The observer is then applied to the problem of secure data transmission based on the finite-time chaos synchronization and the two-channel transmission method.      

基于有限时间观测器的混沌系统同步

根据有限时间稳定的定义,对混沌系统引入了有限时间观测器的概念,采用有限时间观测器实现混沌系统的同步,保证在给定的有限时间区间内,观测器状态与被观测系统的状态误差被限制在一个给定界内,从而达到观测系统状态的目的。利用线性矩阵不等式的方法,将观测器存在条件转化为求解系统的线性矩阵不等式。讨论了混沌系统同步的有限时间观测器的存在条件,并给出了观测器的具体设计。通过对Duffing-Holmes系统的同步仿真,验证了该方法的有效性。     

Comments on finite-time stability of time-delay systems

Recently proposed conditions on finite-time stability in time-delay systems are revisited and it is shown that they are incorrect. General comments on possibility of finite-time convergence in time-delay systems and a necessary condition are given.     

Adaptive parameter identification of linear SISO systems with unknown time-delay

An adaptive online parameter identification is proposed for linear single-input-single-output (SISO) time-delay systems to simultaneously estimate the unknown time-delay and other parameters. After representing the system as a parameterized form, a novel adaptive law is developed, which is driven by appropriate parameter estimation error information. Consequently, the identification error convergence can be proved under the conventional persistent excitation (PE) condition, which can be online tested in this paper. A finite-time (FT) identification scheme is further studied by incorporating the sliding mode scheme into the adaptation to achieve FT error convergence. The previously imposed constraint on the system relative degree is removed and the derivatives of the input and output are not required. Comparative simulation examples are provided to demonstrate the validity and efficacy of the proposed algorithms.     

Robust finite-time control for neutral systems with time-varying delays via sliding mode observer

This paper is concerned with the problem of robust finite-time sliding mode control (SMC) for a class of continuous-time uncertain neutral systems with time-varying delays. Firstly, based on the constructed sliding mode observer, an integral sliding surface is put forward on the estimation space. Secondly, the synthesized SMC law guarantees the finite-time reachability of the predefined sliding surface. Thirdly, through finite-time stability analysis, sufficient conditions are established to guarantee the required performance of the system during both reaching phase and sliding motion phase. Finally, a practical example is provided to verify the effectiveness of the proposed method.     

基于有限时间观测器的离散系统混沌同步

本文基于驱动–响应模型针对一类离散时间混沌系统提出了一种基于有限时间观测器的同步方法. 首先, 将混沌系统写成具有未知输入的线性系统形式. 随后, 给出了观测器匹配条件和强可观条件. 在观测器匹配条件的 假设下, 通过适当的状态变换, 给出了具有降维形式的有限时间观测器设计框架使得该观测器不再受到未知输入的 影响. 然后, 证明了强可观条件结合观测器匹配条件可以保证一个有限时间观测器的存在, 该观测器可以使得响应 系统达到对驱动系统的精确同步, 且达到同步所需要的时间可以任意设定, 不受观测器系统矩阵极点配置和初值条 件的影响. 最后, 给出了两个混沌系统的例子验证了所提方法的有效性.     

时滞依赖H_/H∞观测器的线性系统故障检测

本文研究了线性连续时滞系统的鲁棒故障检测问题.利用H_/H∞故障检测方法,设计了故障检测观测器,并给出了时滞依赖的故障检测观测器设计条件.本文直接给出刻画有限频故障检测性能的线性矩阵不等式条件,避免因引入加权函数而产生的不准确性.最后,仿真算例表明时滞依赖的有限频故障检测观测器可以取得比已有结果更好的故障检测性能.     

Fault tolerant sliding mode control for T-S fuzzy stochastic time-delay system via a novel sliding mode observer approach

In this paper, a fault estimation and fault-tolerant control problem for a class of T-S fuzzy stochastic time-delay systems with actuator and sensor faults is investigated. A novel sliding mode observer is proposed, which can simultaneously estimate the system states, actuator and sensor faults with good accuracy. Based on the state and actuator fault estimation, a new sliding mode control scheme is developed, which can effectively eliminate the influence of actuator fault. Sufficient conditions for the existence of the proposed observer and fault-tolerant sliding mode controller are provided in terms of linear matrix inequality, and moreover, the reachability of the sliding mode surface can be guaranteed under the proposed control scheme. The propose sliding mode observer and fault-tolerant sliding mode controller can overcome the restrictive assumption that the input matrix of all local modes is the same. Finally, a numerical example is provided to verify the effectiveness of the proposed sliding mode observer and fault-tolerant sliding mode control technique.     

Adaptive fuzzy dynamic surface control for uncertain discrete-time non-linear pure-feedback MIMO systems with network-induced time-delay based on state observer

In this paper, a state observer-based adaptive fuzzy dynamic surface control is developed for uncertain discrete-time non-linear pure-feedback multiple-input-multiple-output (MIMO) systems with network-induced time-delay. The uncertainties are approximated by a set of adaptive fuzzy logic systems, with the adjusted parameters updated by a simplified recursive least squares estimation algorithm, combined with a state observer. For a constant known network-induced time-delay, the proposed modified dynamic surface control utilising the predicted system states, expands the acceptable network-induced time-delay and stable operating range for a discrete-time non-linear pure-feedback MIMO system in the network. The simulation results indicate that the presented method is effective.