Robust stabilization of uncertain systems with persistent disturbance and a class of non-linear actuators

Linear uncertain systems perturbed by persistent disturbances and driven by actuators subject to band-bounded nonlinearities are considered. A set of linear matrix inequality based sufficient conditions are derived for designing state feedback controllers which assure ultimate boundedness of closed-loop state trajectories. The effect of the non-linear actuators is identified to that of the considered persistent disturbances. The control purpose is to minimize the ultimate boundedness region to which the state trajectories are eventually confined, while tolerating disturbances of given or the largest magnitudes. Finally, an experimental system, an inverted pendulum on a Stewart platform making translational movement, is arranged to demonstrate the feasibility and effectiveness of the derived results.     

Dynamic quantised feedback stabilisation of discrete-time linear system with white noise input

In this paper, we mainly focus on the problem of quantised feedback stabilisation of a stochastic discrete-time linear system with white noise input. The dynamic quantiser is used here. The stability of the system under state quantisation and input quantisation is analysed in detail, respectively. Both the convergence of the state's mean and the boundedness of the state's covariance matrix norm should be considered when analysing its stability. It is shown that for the two situations of the state quantisation and the input quantisation, if the system without noise input can be stabilised by a linear feedback law, it must be stabilised by the dynamic quantised feedback control policy. The sufficient conditions that the dynamic quantiser should satisfy are given. Using the results obtained in this paper, one can test whether the stochastic system is stabilisable or not. Numerical examples are given to show the effectiveness of the results.     

具有传感器故障的非线性关联大系统的可靠控制

考虑一类非线性关联大系统的可靠控制器设计问题,该系统具有常时滞、参数不确定性、非线性扰动和传感器故障.其中参数不确定性满足匹配条件,非线性扰动满足范数有界条件,传感器具有部分失效的模型.本文的目的是设计无记忆分散控制器来镇定该系统.通过解线性矩阵不等式获得此控制器,使得当传感器器发生故障时被控系统能够保持渐近稳定.最后通过仿真的例子,验证该状态反馈控制器的可行性.     

Robust finite-time guaranteed cost control for impulsive switched systems with time-varying delay

This paper is concerned with the problem of robust finite-time guaranteed cost control for a class of impulsive switched systems with time-varying delay. Firstly, the definitions of finite-time boundedness, finite-time stabilization, and robust finite-time guaranteed cost control are presented. Next, based on the average dwell-time approach, sufficient conditions on robust finite-time guaranteed cost control are obtained for the uncertain impulsive switched systems. Then, by using multiple Lyapunov-like functional method and linear matrix equality (LMI) technique, the state feedback controller is designed to guarantee that the uncertain impulsive switched system is finite-time stabilized. Furthermore, a finite-time guaranteed cost bound is given. Finally, a numerical example is shown to illustrate the effectiveness of the proposed results.     

一类线性离散时间系统有限时间控制问题

讨论一类具有时变、有限能量外部扰动的线性离散时间系统的有限时间控制问题.首先研究问题可解的充分条件,并讨论了状态反馈控制器存在的条件,这些条件可归结为基于线性矩阵不等式(LMI)的可解性问题;然后给出状态反馈控制器和输出反馈控制器的具体设计;最后通过仿真验证了该方案的有效性.     

利用状态反馈增益变化设计广义系统H∞可靠控制器

通过对状态反馈两种增益变化形式的分析,研究广义系统H∞可靠控制器的设计问题.给出基于状态反馈增益变化的广义系统H∞可靠控制器的定义,得到了执行器故障模型.用线性矩阵不等式(LMI)方法,研究两种状态反馈增益变化的广义系统H∞控制器存在的充分条件和设计方法.进而,针对执行器的不同故障情形,用LMI方法给出广义系统存在基于状态反馈增益变化的H∞可靠控制器的充分条件.最后,给出了优化广义系统H∞可靠控制器的设计算法.     

线性时滞系统的耗散控制

从全新的二次型供给率的耗散角度，研究了线性时滞系统的二次稳定性和耗散控制问题，给出了线性矩阵不等式(LMI)形式的充分条件。而且，考虑了时滞系统在状态反馈控制器和动态输出反馈控制器作用下的闭环系统的二次稳定和耗散性问题，同样给出了LMI形式的充分条件，并通过线性矩阵不等式的可行解构造出耗散状态反馈控制律和动态输出反馈控制律。     

Decentralized adaptive robust control for a class of large scale systems with uncertainties in the interconnections

The problem of decentralized control is considered for a class of time-varying large scale systems with uncertainties and external disturbances in the interconnections. In this paper, the upper bounds of the uncertainties and external disturbances are assumed to be unknown. The adaptation laws are proposed to estimate such unknown bounds, and by making use of the updated values of these unknown bounds, a class of decentralized linear and non-linear state feedback controllers are constructed. It is shown that by employing the proposed decentralized non-linear state feedback controllers, the solutions of the resulting adaptive closed-loop large scale system can be guaranteed to be uniformly bounded, and the states are uniformly asymptotically stable. By using the decentralized linear state feedback controllers, one can guarantee the uniform ultimate boundedness of the resulting adaptive closed-loop large scale system. Finally, a numerical example is given to demonstrate the validity of the results.     

Robust control of robots via linear estimated state feedback

In this note we propose a robust tracking controller for robots that requires only position measurements. The controller consists of two parts: a linear observer part that generates an estimated error state from the error on the joint position and a linear feedback part that utilizes this estimated state. It is shown that this computationally efficient controller yields semi-global uniform ultimate boundedness of the tracking error. An interesting feature of the controller is that it straightforwardly extends results on robust control of robots by linear state feedback to linear estimated-state feedback     

H∞ and positive-real control for linear neutraldelay systems

This note is concerned with the H_∞ and positive-real control problems for linear neutral delay systems. The purpose of H_∞ control is the design of a memoryless state feedback controller which stabilizes the neutral delay system and reduces the H_∞ norm of the closed-loop transfer function from the disturbance to the controlled output to a prescribed level, while the purpose of positive-real control is to design a memoryless state feedback controller such that the resulting closed-loop system is stable and the closed-loop transfer function is extended strictly positive real. Sufficient conditions for the existence of the desired controllers are given in terms of a linear matrix inequality (LMI). When this LMI is feasible, the expected memoryless state feedback controllers can be easily constructed via convex optimization     

Robust stability and H-infinity control for uncertain discrete-time Markovian jump singular systems

The robust stability and stabilization, and H-infinity control problems for discrete-time Markovian jump singular systems with parameter uncertainties are discussed. Based on the restricted system equivalent （r.s.e.） transformation and by introducing new state vectors, the singular system is transformed into a discrete-time Markovian jump standard linear system, and the linear matrix inequality （LMI） conditions for the discrete-time Markovian jump singular systems to be regular, causal, stochastically stable, and stochastically stable with 7- disturbance attenuation are obtained, respectively. With these conditions, the robust state feedback stochastic stabilization problem and H-infinity control problem are solved, and the LMI conditions are obtained. A numerical example illustrates the effectiveness of the method given in the oaoer.     

High-gain observers in the presence of measurement noise: A switched-gain approach

This paper considers output feedback control using high-gain observers in the presence of measurement noise for a class of nonlinear systems. We study stability in the presence of measurement noise and illustrate the tradeoff when selecting the observer gain between state reconstruction speed and robustness to model uncertainty on the one hand versus amplification of noise on the other. Based on this tradeoff we propose a high-gain observer that switches between two gain values. This scheme is able to quickly recover the system states during large estimation error and reduce the effect of measurement noise in a neighborhood of the origin of the estimation error. We argue boundedness and ultimate boundedness of the closed-loop system under switched-gain output feedback.     

Observer‐based model reference control of Takagi–Sugeno–Lipschitz systems affected by disturbances using quadratic boundedness

In this paper, a model reference control strategy is proposed in order to perform trajectory tracking in Takagi–Sugeno–Lipschitz (TSL) systems. Since the state vector is assumed not to be completely available for measurement, a proportional observer is added to the control scheme in order to apply an estimate‐feedback control action instead of a state‐feedback one. The overall design of both the controller and the observer gains are performed using a Lyapunov‐based quadratic boundedness specification, in order to improve the robustness against unknown exogenous disturbances. It is shown that the conditions that ensure convergence within ellipsoidal regions of the tracking and estimation errors can be expressed in the form of a linear matrix inequality (LMI) formulation. The effectiveness of the developed control strategy is demonstrated by means of simulation results.     

离散随机Markov跳跃系统有限时间有界控制

研究一类带乘性噪声的离散时间随机Markov跳跃系统的有限时间控制问题.首先,定义系统的有限时间稳定和有限时间有界,通过逐次迭代和条件期望给出系统有限时间稳定的充分必要条件;其次,针对含干扰的系统,利用Lyapunov方法和线性矩阵不等式技术得到系统有限时间有界的充分条件并设计状态反馈镇定控制器;然后,进一步考虑转移概率信息不完全下的有限时间有界问题;最后,通过数值例子验证了所提出方法的有效性.     

不确定时滞系统的鲁棒耗散控制

耗散不确定性是已经被广泛讨论的范数有界的不确定性和正实不确定性的广义化，因此，从二次型供给率的角度，将耗散不确定性引入线性时变时滞系统，研究了含有此类不确定性的线性时滞系统的鲁棒耗散控制问题，给出了线性矩阵不等式（LMI）形式的充分条件。而且，考虑了不确定时滞系统在状态反馈控制器作用下的闭环系统的耗散控制问题，同样给出了LMI形式的充分条件，并通过线性矩阵不等式的可行解构造出鲁棒耗散的状态反馈控制器。最后。通过实例证明了定理的可行性。     

一类线性不确定时滞混杂系统的稳定性

研究了一类具有不确定的线性参数及时滞的混杂系统，利用线性矩阵不等式策略和Riccati方法，给出了系统鲁棒稳定性和可稳定性的充分条件，并运用混杂状态反馈控制策略设计了控制器切换方案．最后的仿真实例表明了控制策略的有效性．     

Multimodel Robust Control by Fast Output Sampling-An LMI Approach

An LMI approach to robust multimodel controller design is proposed. The fast output sampling control law considered here allows in theory to realize the effect of a robust state feedback gain simultaneously for a family of linear models. In practice, there are two reasons why exact realization of state feedback may not be desirable or even impossible: poor error dynamics, and noise sensitivity due to large output feedback gains. An LMI formulation of the design problem allows to approximate a robust state feedback design by fast output sampling, in a way that closeness to the original design can be traded against reducing these deteriorating effects. The proposed method is illustrated by a multivariable design example and experimental results.