Networked and event-triggered control systems
Networked and event-triggered control systems
复制标题
网络化和事件触发的控制系统
DOI：
10.6100/ir716705
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M. Donkers
中科院分区：
文献类型：
--
作者：
M. Donkers
在本论文中，研究了针对计算和通信资源有限的平台定制的控制算法。人们对此类控制算法的兴趣源于以下事实：如今控制算法是在小型且廉价的嵌入式微处理器上实现的，并且传感器、执行器和控制器通过多用途通信网络连接。为了解决计算能力不再充裕以及通信网络带宽不再有限的问题，控制算法要么必须对这些约束引起的缺陷具有鲁棒性，要么需要最佳地利用可用的计算和通信资源。在本论文中，开发了具有此类特性的控制算法的设计和分析方法。网络控制系统：在本文的第一部分中，研究了所谓的网络控制系统（NCS）。论文这一部分研究的控制算法可以看作是传统的采样数据控制器，需要对使用有限带宽通信通道引入的伪影具有鲁棒性。本文考虑的网络引起的现象包括时变传输间隔、时变延迟、数据包丢失和通信约束。后一种现象导致并非所有传感器和执行器数据都可以同时传输，因此需要调度协议来协调何时通过网络传输什么数据。为了分析NCS的稳定性，提出了离散时间建模框架，特别考虑两种情况：在第一种情况下，传输间隔和延迟被假设为上限和下限，在第二种情况下，它们由随机过程描述，满足连续联合概率分布。两种情况都是相关的。与后一种情况相比，前一种情况需要的网络行为描述不太详细，而后一种情况则导致稳定性分析比前者不太保守。这允许在建模准确性（网络引起的效应）和稳定性分析的保守性之间进行权衡。在这两种情况下，都考虑线性设备和控制器，并将 NCS 建模为离散时间切换线性参数变化系统。为了评估该系统的稳定性，开发了新的多面体过近似，这允许使用有限数量的线性矩阵不等式来研究 NCS 的稳定性。将表明，相对于文献中的现有结果，这种方法显着降低了保守性，并且允许研究更大类别的控制器，包括基于离散时间动态输出的控制器。因此，论文这一部分的主要贡献是开发了一个新的通用框架，以一种几乎保守的方式分析受四种网络引起的现象影响的 NCS 的稳定性。事件触发控制系统：在本文的第二部分中，研究了所谓的事件触发控制（ETC）系统。 ETC是一种在外部事件发生后执行控制任务的控制策略，而不是像传统周期控制那样经过一定时间后执行。通过这种方式，ETC 可以被设计为仅在需要时提供控制更新，从而最佳地利用可用的计算和通信资源。论文的这一部分由这个有吸引力的研究领域的三个主要贡献组成。第一个贡献是将 ETC 的现有结果扩展到基于动态输出的反馈控制器，而不是大多数 ETC 文献中常见的状态反馈控制。此外，还提出了去中心化事件触发的扩展。这些扩展对于 ETC 的实际实现非常重要，因为在许多控制应用中，几乎无法提供完整的状态反馈，并且传感器和执行器通常是物理分布的，这禁止使用集中式事件触发条件。为了研究该 ETC 系统的稳定性和 L1 性能，开发了基于脉冲系统的建模框架。此外，对于所提出的新颖的基于输出的分散事件触发条件，显示了如何保证最小事件间时间的非零下限以及如何计算它们。第二个贡献是提出了新型周期性事件触发控制 (PETC) 算法，其目标是将周期性控制和 ETC 所提供的优势结合起来。在PETC中，事件触发条件被周期性地监控，并且在每个采样时刻决定是否传输数据以及是否使用计算资源来执行控制任务。这种事件触发条件有几个好处，包括固有的最小事件间时间，可以直接调整。此外，事件触发条件仅在周期性采样时间验证，而不是连续验证，这一事实使得在标准时间切片嵌入式软件架构中实现该策略成为可能。为了分析这些 PETC 系统的稳定性和 L2 性能，将提供基于分段线性系统模型和脉冲系统模型的方法，从而形成有效的 PETC 分析框架。最后，提出了一种解决反馈控制算法和事件触发条件协同设计问题的新方法。特别是，提出了一种解决最小注意力和随时注意力控制问题的新方法。在最小注意力控制中，控制任务所需的“注意力”被最小化，而在任何时间注意力控制中，调度器给出的“注意力”下的性能被最大化。在这种情况下，“注意力”被解释为控制任务的两次连续执行之间经过的时间的倒数。这两个控制问题通过将它们表示为线性程序来解决，可以以在线方式有效地解决。这提供了一种新的、优雅的方法来在一个统一的框架中解决最小注意力控制问题和随时注意力控制问题。本文提出的贡献可以为未来的研究探索奠定基础，最终为 NCS 和 ETC 系统形成成熟的系统理论，这对于在各种实际控制应用中部署 NCS 和 ETC 系统是不可或缺的。
In this thesis, control algorithms are studied that are tailored for platforms with limited computation and communication resources. The interest in such control algorithms is motivated by the fact that nowadays control algorithms are implemented on small and inexpensive embedded microprocessors and that the sensors, actuators and controllers are connected through multipurpose communication networks. To handle the fact that computation power is no longer abundant and that communication networks do not have in finite bandwidth, the control algorithms need to be either robust for the deficiencies induced by these constraints, or they need to optimally utilise the available computation and communication resources. In this thesis, methodologies for the design and analysis of control algorithms with such properties are developed. Networked Control Systems: In the first part of the thesis, so-called networked control systems (NCSs) are studied. The control algorithms studied in this part of the thesis can be seen as conventional sampled-data controllers that need to be robust against the artefacts introduced by using a finite bandwidth communication channel. The network-induced phenomena that are considered in this thesis are time-varying transmission intervals, time-varying delays, packet dropouts and communication constraints. The latter phenomenon causes that not all sensor and actuator data can be transmitted simultaneously and, therefore, a scheduling protocol is needed to orchestrate when to transmit what data over the network. To analyse the stability of the NCSs, a discrete-time modelling framework is presented and, in particular, two cases are considered: in the first case, the transmission intervals and delays are assumed to be upper and lower bounded, and in the second case, they are described by a random process, satisfying a continuous joint probability distribution. Both cases are relevant. The former case requires a less detailed description of the network behaviour than the latter case, while the latter results in a less conservative stability analysis than the former. This allows to make a tradeoff between modelling accuracy (of network-induced effects) and conservatism in the stability analysis. In both cases, linear plants and controllers are considered and the NCS is modelled as a discrete-time switched linear parameter-varying system. To assess the stability of this system, novel polytopic overapproximations are developed, which allows the stability of the NCS to be studied using a finite number of linear matrix inequalities. It will be shown that this approach reduces conservatism significantly with respect to existing results in the literature and allows for studying larger classes of controllers, including discrete-time dynamical output-based controllers. Hence, the main contribution of this part of the thesis is the development of a new and general framework to analyse the stability of NCSs subject to four network-induced phenomena in a hardly conservative manner. Event-Triggered Control Systems: In the second part of the thesis, socalled event-triggered control (ETC) systems are studied. ETC is a control strategy in which the control task is executed after the occurrence of an external event, rather than the elapse of a certain period of time as in conventional periodic control. In this way, ETC can be designed to only provide control updates when needed and, thereby, to optimally utilise the available computation and communication resources. This part of the thesis consists of three main contributions in this appealing area of research. The first contribution is the extension of the existing results on ETC towards dynamical output-based feedback controllers, instead of state-feedback control, as is common in the majority of the literature on ETC. Furthermore, extensions towards decentralised event triggering are presented. These extensions are important for practical implementations of ETC, as in many control applications the full state is hardly ever available for feedback, and sensors and actuators are often physically distributed, which prohibits the use of centralised event-triggering conditions. To study the stability and the L1-performance of this ETC system, a modelling framework based on impulsive systems is developed. Furthermore, for the novel output-based decentralised event-triggering conditions that are proposed, it is shown how nonzero lower bounds on the minimum inter-event times can be guaranteed and how they can be computed. The second contribution is the proposition of the new class of periodic event-triggered control (PETC) algorithms, where the objective is to combine the benefits that, on the one hand, periodic control and, on the other hand, ETC offer. In PETC, the event-triggering condition is monitored periodically and at each sampling instant it is decided whether or not to transmit the data and to use computation resources for the control task. Such an event-triggering condition has several benefits, including the inherent existence of a minimum inter-event time, which can be tuned directly. Furthermore, the fact that the event-triggering condition is only verified at the periodic sampling times, instead of continuously, makes it possible to implement this strategy in standard time-sliced embedded software architectures. To analyse the stability and the L2-performance for these PETC systems, methodologies based on piecewiselinear systems models and impulsive system models will be provided, leading to an effective analysis framework for PETC. Finally, a novel approach to solving the codesign problem of both the feedback control algorithm and the event-triggering condition is presented. In particular, a novel way to solve the minimum attention and anytime attention control problems is proposed. In minimum attention control, the `attention' that a control task requires is minimised, and in anytime attention control, the performance under the `attention' given by a scheduler is maximised. In this context, `attention' is interpreted as the inverse of the time elapsed between two consecutive executions of a control task. The two control problems are solved by formulating them as linear programs, which can be solved efficiently in an online fashion. This offers a new and elegant way to solve both the minimum attention control problem and the anytime attention control problem in one unifying framework. The contributions presented in this thesis can form a basis for future research explorations that can eventually lead to a mature system theory for both NCSs and ETC systems, which are indispensable for the deployment of NCSs and ETC systems in a large variety of practical control applications.
影响因子：
2.1
作者：
Gawthrop, Peter J.;Wang, Liuping
通讯作者：
Wang, Liuping