具有结构不确定性的输出反馈线性系统的鲁棒稳定性分析

基于向量的幂变换方法，对具有结构不确定性的输出反馈线性系统的鲁棒稳定性问题作了分析。单参数摄动时给出了闭环系统鲁棒稳定的充要条件，多参数摄动时得到了保证系统鲁棒稳定的充分条件，导出了闭环系统鲁棒稳定区域的一种代数表达形式。最后给出了实例。     

不确定性负虚系统的绝对稳定性研究

负虚性质广泛存在于各种工程应用中,受到了广大控制领域学者的关注,但是目前对于负虚系统理论的研究局限于负虚系统定义、性质的延伸和线性系统理论部分,忽略了实际场景中存在的不确定性.为此,针对斜率有界、无记忆的不确定性和负虚被控对象以及严格负虚控制器的互连系统,利用环变换、卡尔曼分解等方法将系统变为线性部分和非线性部分的并联,进而利用Lur'e-Postnikov型李亚普诺夫函数提出了互连系统的绝对稳定性条件.并且,在负虚系统和不确定性部分已知时,给出了使整个系统绝对稳定的严格负虚控制器的DC增益条件,并通过两个数值仿真实例验证了所提理论的正确性和有效性.     

Dynamical Output Feedback Stabilization Of Mimo Bilinear Systems With Undamped Natural Response

This paper considers the globally asymptotic stabilization problem of multi‐input multi‐output bilinear systems with undamped natural response. Under the conditions for asymptotic stabilization by static state feedback control and system detectability, two output dynamic feedback controllers with saturation bounded control are constructed. The global asymptotic stability of the closed‐loop system is verified by Lyapunov stability theory and LaSalle's Lemma. An example is given to demonstrate the obtained results.     

Lyapunov-Based Approach to Multiagent Systems With Switching Jointly Connected Interconnection

This note addresses a coordination problem of a multiagent system with jointly connected interconnection topologies. Neighbor-based rules are adopted to realize local control strategies for these continuous-time autonomous agents described by double integrators. Although the interagent connection structures vary over time and related graphs may not be connected, a sufficient condition to make all the agents converge to a common value is given for the problem by a proposed Lyapunov-based approach and related space decomposition technique     

一般线性滞后系统的稳定性及反馈镇定

本文建立一般线性滞后微分系统的简洁稳定性定理，给出一般时不变线性系统的一种反馈镇定方法，这种方法以线性时不变系统的LQ反馈为特例，取得了以往文献难以达到的结果．     

State-Estimator-Based Feedback Control for a Class of Piezoelectric Systems With Hysteretic Nonlinearity

Because the piezoceramic materials were ferroelectric, the inherent hysteretic nonlinearity always existed in the piezoelectric system (PES). Due to the existence of hysteresis and modeling error, the system performance by only PID control often deteriorated. Because not all of the states of the PES were measurable, a state estimator was required to obtain the unavailable state. To begin with, a feedback linearization using estimated state was employed to transform the PES to a new coordinate system. To track the trajectory with a primary frequency, the reference model with desired amplitude and phase features was also designed. In the mean while, a tracking error model was achieved for the system analysis. Then the feedback linearization with a sliding-mode control including equivalent control and switching control was established to enhance system performance. The equivalent control using the signals from state estimator and reference model was designed to gain the desired control behavior. The switching control was applied to ameliorate the robust performance. Finally, the stability of the overall system was verified by Lyapunov stability theory. The tracking result converged to a set in terms of system and control parameters. In summary, the state-estimator-based feedback control contained state estimator, feedback linearization, reference model, and sliding-model control. Experiments of the PES were also presented to verify the usefulness of the proposed control.     

Robustness With Respect to Sampling for Stabilization of Riesz Spectral Systems

We suppose that a continuous-time feedback is input–output stabilizing for an infinite-dimensional system. We address the question of whether the sampled-data controller obtained by applying idealized sample-and-hold to this continuous-time feedback is also input–output stabilizing if the sampling time is small enough. This question has been previously addressed for fairly general systems under various conditions. In this note, we restrict our attention to Riesz spectral systems, for which we generalize the existing results. Specifically, we give two relatively simple conditions which, combined, are sufficient for the sampled-data controller to be stabilizing. The first condition is a spectrum decomposition for the open-loop system generator, which by itself is necessary, but not sufficient, for the system to be stabilizable by sampled-data control. The second is a summability condition relating the real part of the spectrum of the generator and the expansion coefficients for the input and feedback operators.     

Output Feedback Stabilization of Linear Systems With Actuator Saturation

The note presents a method for designing an output feedback law that stabilizes a linear system subject to actuator saturation with a large domain of attraction. This method applies to general linear systems including strictly unstable ones. A nonlinear output feedback controller is first expressed in the form of a quasi-LPV system. Conditions under which the closed-loop system is locally asymptotically stable are then established in terms of the coefficient matrices of the controller. The design of the controller (coefficient matrices) that maximizes an estimate of the domain of attraction is then formulated and solved as an optimization problem with LMI constraints     

一类MIMO继电反馈系统极限环的全局稳定性

研究了分散继电反馈系统极限环的全局稳定性问题.主要思想是将所研究的极限环的全局稳定性问题转化为不确定离散系统的渐近稳定性问题.并给出了判定稳定性的充分条件.结果表明,在某些约束条件下,所有系统轨迹最终进入并停留在某一特定区域,而且趋于极限环.数值例子仿真验证了提出的方法的有效性.     

An Internal-Model Controller for a Class of Single-Input Single-Output Nonlinear Systems: Stability and Robustness

A controller design procedure for a class of nonlinear systems is presented. The structure of the control system corresponds to the so-called internal-model controller that, for linear systems, has exhibited good performance and stability robustness with respect to disturbances and to uncertainty in the plant parameters. The systems involved are single-input single-output and fully linearizable by coordinates transformation and state feedback. It is shown that the plant output converges to a constant reference, even under the presence of constant disturbances and parameter uncertainties, provided the closed-loop system has an asymptotically stable equilibrium point placed anywhere. This scheme does not need an explicit design of a nonlinear observer; instead, it uses the state of a plant model. A conservative stability robustness margin is estimated by applying standard results of Lyapunov theory.     

A Trajectory-Based Approach for the Stability Robustness of Nonlinear Systems with Inputs

 We show, for two different definitions of semiglobal practical external stability, that the stability property holds on semi-infinite time intervals if and only if it holds on arbitrarily long but finite time intervals. These results have immediate applications in the analysis of the stability properties of highly oscillatory systems with inputs using averaging or for systems with inputs that are slowly varying. Results are stated for general flows and the stability is given with respect to arbitrary (not necessarily compact) sets. Date received: May 11, 2001. Date revised: March 14, 2002.     

基于动态反馈控制器的网络控制系统的稳定性分析

考虑实际模型的不确定性,针对一类具有不确定线性参数的网络控制系统,给出具有网络诱导时延及不确定线性参数的被控对象模型,设计其动态反馈控制器,建立基于动态反馈控制器的网络控制系统闭环模型.采用Lyapunov方法,给出保证该系统稳定的最大允许时延上界.仿真结果表明系统模型及控制器设计的合理性,所得最大允许时延上界保守性更弱.     

Output Feedback Stabilization of Networked Control Systems With Packet Dropouts

In this paper, we discuss the modeling and control of a class of networked control systems (NCSs) with packet dropouts. For the cases that there may be packet dropouts in both the backward and the forward channels in the communication network, and that the network-induced delays are shorter than one sampling period, the closed-loop NCS is modeled as a discrete-time switched system with four subsystems. By using the asynchronous dynamical systems approach and the average dwell-time method, sufficient conditions for the exponential stability of the closed-loop NCS are presented in terms of nonlinear matrix inequalities, and the relation between the packet dropout rate and the stability of the closed-loop NCS is explicitly established. A procedure involving an iterative algorithm is proposed to design the observer-based output feedback controllers. Lastly, an illustrative example is given to demonstrate the effectiveness of the proposed results.     

时延网络控制系统的稳定性分析

为保证闭环系统的全局渐进稳定性,系统的时延必须是有界的。本文中讨论了具有网络诱导时延的网络控制系统的模型,同时给出了最大允许传输间隔以及一个实际例子。实践证明本文中给出的方法在简单的系统中是十分有效的。接着提出了一个减小网络诱导时延的算法,仿真结果表明了该方法的有效性。     

Input-to-State Stability of Time-Delay Systems: A Link With Exponential Stability

The main contribution of this technical note is to establish a link between the exponential stability of an unforced system and the input-to-state stability (ISS) via the Liapunov–Krasovskii methodology. It is proved that a system which is (globally, locally) exponentially stable in the unforced case is (globally, locally) input-to-state stable when it is forced by a measurable and locally essentially bounded input, provided that the functional describing the dynamics in the unforced case is (globally, on bounded sets) Lipschitz and the functional describing the dynamics in the forced case satisfies a Lipschitz-like hypothesis with respect to the input. Moreover, a new feedback control law is provided for delay-free linearizable and stabilizable time-delay systems, whose dynamics is described by locally Lipschitz functionals, by which the closed-loop system is ISS with respect to disturbances adding to the control law, a typical problem due to actuator errors.      

Frequency Regulation of Power Systems With a Wind Farm by Sliding-Mode-Based Design

Load frequency regulation is an essential auxiliary service used in dealing with the challenge of frequency stability in power systems that utilize an increasing proportion of wind power. We investigate a load frequency control method for multi-area interconnected power systems integrated with wind farms, aimed to eliminate the frequency deviation in each area and the tie-line power deviation between different areas. The method explores the derivative and integral terminal sliding mode control technology to solve the problem of load frequency regulation. Such technology employs the concept of relative degrees. However, the subsystems of wind-integrated interconnected power systems have different relative degrees, complicating the control design. This study develops the derivative and integral terminal sliding-mode-based controllers for these subsystems, realizing the load frequency regulation. Meanwhile, closed-loop stability is guaranteed with the theory of Lyapunov stability. Moreover, both a thermal power system and a wind power system are applied to provide frequency support in this study. Considering both constant and variable external disturbances, several numerical simulations were carried out in a two-area thermal power system with a wind farm. The results demonstrate the validity and feasibility of the developed method.      

实例讲解七层协议参考模型

对OSI七层协议参考模型的概念,通过用寄信收信的过程,形象的说明了每一层的功能,以QQ信息的发送过程为例,深入探讨了通过七层进行网络互联.     

基于CPLD的热电阻动态补偿滤波器

有些传感器因其不理想的动态特性而不能被高性能的测量或控制系统采用，热电阻就是一个典型的例子。而这种不理想的动态特性可用一个后继的滤波器来补偿。通过对热电阻时间常数的测定，我们可以建立其系统模型，进而确定其动态补偿滤波器的参数。本文用VHDL对基于CPLD的补偿滤波器进行了描述，并在Altera的Max PluslI中仿真．结果证明这一方案是非常有效可行的。