Este trabalho aborda o problema de controle baseado em eventos para sistemas em tempo discreto, considerando que o sistema possui os dispositivos atuadores e sensores em nós diferentes e separados por uma rede de comunicação. A estratégia baseada em eventos consiste em reduzir a utilização da rede ao transmitir as informações do sensor para o atuador apenas quando um evento é gerado pela violação de um determinado limiar pela função de disparo. Primeiramente, são formuladas condições para a estabilidade de um sistema linear com realimentação estática de estados sob a estratégia proposta, com base na teoria de Lyapunov. Como as condições são postas na forma de desigualdades matriciais lineares (LMIs, do inglês linear matrix inequalities), problemas de otimização convexos podem ser utilizados na determinação dos parâmetros da função de disparo, bem como na resolução do problema de co-design, ou seja, do projeto simultâneo do controlador e da função de disparo, os quais são providos na sequência. A partir deste resultado básico, a metodologia é estendida para o caso em que ocorre a saturação do atuador. A seguir, é apresentada a extensão da metodologia para o caso em que o estado da planta não está disponível para o sensor, sendo então utlizado um observador de estados, considerando-se tanto o caso em que o modelo da planta utilizado no observador corresponde exatamente à dinâmica real da planta quanto o caso em que este modelo apresenta incertezas. Exemplos numéricos são apresentados para ilustrar todas as classes de sistemas consideradas, com os quais constata-se que a estratégia proposta é eficiente na redução da utilização dos recursos da rede de comunicação. / This work approaches the problem of event-triggered control for discrete time systems, considering that the system has the actuator and sensor devices in different nodes, separated by a communication network. The event-triggered strategy consists in reducing the utilization of the network by only transmitting the information from the sensor to the actuator when an event is generated by the violation of a determined threshold by the trigger function. Firstly, conditions for the stability of a linear system with a static state feedback under the proposed strategy are formulated based on the Lyapunov theory. Since the conditions are given in the form of linear matrix inequalities (LMIs), convex optimization problems can be used for the determination of the trigger function parameters, as well as the co-design of the feedback gain and the trigger function, which are given next. From this basic result, the methodology is extended to the case where occurs the saturation of the actuator. Following, the extension of the methodlogy to the case in which the plant states are not available for measure is presented, and a state-observer is used, considering both the case that the plant model corresponds exactly to the real plant dynamics and the case where this model has uncertainties. Numeric examples are shown to illustrate all the system classes considered, with which it is found that the proposed strategy is efficient in the reduction of the network resources utilization.

Este trabalho apresenta uma proposta de solução para compensar o atraso variável, característico de redes IP. O preditor de Smith é tradicionalmente usado para compensar atrasos, mas no caso deste tipo de rede um fator importante que pode degradar o controle do sistema são as grandes variações nos atrasos sofridos pelas mensagens. Para tratar este problema, este trabalho baseia-se na criação de uma estrutura de dados de armazenamento para a saída do preditor de Smith, possibilitando a comparação do valor de saída da planta com o valor adequado guardado na estrutura. Para determinação do valor correspondente, este está associado a um índice calculado com o tempo de roundtrip obtido de informações dos pacotes de dados proveniente da planta. Para se chegar a tal solução, foi analisada nas primeiras seções a influência do atraso em malhas de controle e posteriormente um estudo do estado da arte para tipos de controle sobre redes IP. Ao final é apresentada uma análise experimental, demonstrando resultados promissores da aplicação desta proposta. / This work presents a solution to compensate the varying delay, characteristic of IP networks. The Smith predictor is traditionally used to compensate delays but in this type of networks an other important factor that can destabilize the system is the large jitter of the delay. In order to solve this problem, the solution presented here is based on a data structure to save the output from the model of the plant used by the Smith predictor, that make possible to compare the output from the plant with the corresponding value in the structure. In order to take the correspondent value, it is associated to an index which is calculated with the roundtrip obtained from the informations in the packet arrived from the plant. In order to formulate this solution, it was analised in the first sections the influence of the delay in control systems and then a study of the state of art of the control systems over IP networks. At the end, an experimental analise to demonstrate the good result of the application of this solution is presented.

A importância das redes de comunicação industriais em modernos sistemas de automação e controle industriais tem aumentado significativamente nos últimos anos, devido aos avanços nas áreas de processadores e softwares embarcados, que permitem o desenvolvimento de dispositivos com elevada capacidade de processamento a custos reduzidos. Estas características também são muito importantes em sistemas automotivos, visto que existe uma tendência para a substituição de sistemas mecânicos e hidráulicos em veículos e o espaço disponível para implementação é bastante reduzido. Esta substituição passa pela elaboração de complexos algoritmos de controle, os quais, quando operam sobre uma rede de comunicação, precisam considerar explicitamente os efeitos do canal de comunicação compartilhado na dinâmica do sistema em malha fechada. Este trabalho apresenta uma análise do impacto da comunicação em rede sobre sistemas de controle. Mais especificamente, analisa-se o comportamento do protocolo Flexray, recentemente desenvolvido por um consórcio de importantes empresas e que incorpora interessantes conceitos para escalonamento de mensagens síncronas e assíncronas. No trabalho foram realizados experimentos com três diferentes tipos de controladores aplicados ao estudo de caso de uma suspensão ativa, onde o sistema tem sua malha fechada sobre a rede FlexRay. / The importance of communication networks on modern automation systems has increased significantly over the last years, mostly due to advances in embedded microprocessor and software technologies, which enable the development of devices with high processing power at reduced costs. These characteristics are very important for vehicle systems, since there is nowadays a trend to replace mechanical and hydraulic systems, and the space available for implementation is limited. This replacement requires very complex control algorithms, which, when operating on a communication network, have to consider explicitly the effects introduced by the shared communication channel on the closed loop system dynamics. This work presents an analysis of the network communication impact over control systems. More specifically, it is of interest to analyse the behavior of the FlexRay protocol, which has been recently developed by a Consortium of important companies and incorporates interesting concepts of synchronous and asynchronous message scheduling. In this work, some experiments were performed with three controllers, which were developed using different methodologies, applied to the case study of an active suspension system, where the loop is closed over the FlexRay protocol.

Control systems utilizing wireless sensor and actuator networks can be severely affectedby the properties of the communication links. Radio fading and interferencemay cause communication losses and outages in situations when the radio environmentis noisy and low transmission power is desirable. This thesis proposes amethod to compensate for such unpredictable losses of data in the feedback controlloop by introducing a predictive outage compensator (POC). The POC is a filter tobe implemented at the receiver sides of networked control systems where it generatesartificial samples when data are lost. If the receiver node does not receive thedata, the POC suggests a command based on the history of past data. It is shownhow to design, tune and implement a POC. Theoretical bounds and simulationresults show that a POC can improve the closed-loop control performance undercommunication losses considerably. We provide a deterministic and a stochasticmethod to synthesize POCs. Worst-case performance bounds are given that relatethe closed-loop performance with the complexity of the compensator. We also showthat it is possible to achieve good performance with a low-order implementationbased on Hankel norm approximation. Tradeoffs between achievable performance,communication loss length, and POC order are discussed. The results are illustratedon a simulated example of a multiple-tank process. The thesis is concludedby an experimental validation of wireless control of a physical lab process. Herethe controller and the physical system are separated geographically and interfacedthrough a wireless medium. For the remote control we use a hybrid model predictivecontroller. The results reflect the difficulties in wireless control as well as theyhighlight the flexibility and possibilities one obtains by using wireless instead of awired communication medium. / VR, SSF, VINNOVA via Networked Embedded Control Systems, EU Sixt Framework Program via HYCON and SOCRADES

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第19124号 / 情博第570号 / 新制||情||100(附属図書館) / 32075 / 京都大学大学院情報学研究科システム科学専攻 / (主査)教授 杉江 俊治, 教授 太田 快人, 教授 大塚 敏之, 准教授 東 俊一 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

Wireless, Edge-based control and 5G networks are all examples of technologies of the emerging Industry 4.0. Understanding and evaluating these technologies is important to the development of future manufacturing and factories. However, moving from classical, wired control systems to wireless and Edge-based systems comes with new challenges such as communication delays and packet losses. The purpose of this thesis is to develop and evaluate the performance of a wireless 5G and Edge-based control system. Firstly, we aim to find the achievable end-to-end latency of three different network architectures: local control, control over wired Ethernet and control over wireless 5G. Secondly, we propose and test a conservative tuning approach on a Ball and Beam process which represents a time-sensitive and mission-critical process. The proposed conservative tuning approach is based on an Internal Model Control framework which enables an adjustment of the controller parameters based onthe worst-case measured latency. The results show that the measured latency increases as the Task interval time is increasing and as the controller is moving further away from a local level. The results also show that the introduced latency over 5G is making the system unstable if the latency is not taken into account in the design. The proposed conservative tuning approach successfully adjusts the parameters to remove this unstable behavior but degrades the control performance and shows signs of an overly conservative tuning compared to a local controller. The thesis concludes that the proposed conservative tuning approach shows promising results but would benefit from being further developed towards a latency-aware controller. This could be achieved by firstly improving the way latency is measured to enable extensive data collection. The data could then be utilized by using machine learning or time-series to predict the latency and adjust the parameters in real-time, using the proposed tuning approach.

No description available.

Control over wireless sensor and actuator networks is of growing interest in process industry since it enables flexible design, deployment, operation, and maintenance. An important problem in industrial wireless control is how to limit the amount of information that needs to be exchanged over the network. In this thesis, network scheduling and remote control co-design is considered to address this problem. In the first part, we propose a design of an optimal network schedule for state estimation over a multi-hop wireless sensor network. We formulate an optimization problem, minimizing a linear combination of the averaged estimation error and transmission energy. A periodic network schedule is obtained, which specifies when and through which routes each sensor in the network should transmit its measurement, so that an optimal remote estimate under sensor energy consideration is achieved. We also propose some suboptimal schedules to reduce the computational load. The effectiveness of the suboptimal schedules is evaluated in numerical examples. In the second part, we propose a co-design framework for sensor scheduling, routing, and control over a multi-hop wireless sensor and actuator network. For a decoupled plant and LQG control performance, we formulate an optimization problem and show that the optimal schedule, routing, and control can be obtained locally for each control loop. In this part, we also introduce algorithms to reconfigure the schedules and routes when a link in the network is disconnected. The results are illustrated in a numerical example. In the third part, we consider event-based feedforward control from a wireless disturbance sensor. We derive stability conditions when the closed-loop system is subject to actuator saturation. Feedforward control with anti-windup compensation is introduced to reduce the effect of actuator saturation. The effectiveness of the approach is illustrated in some numerical examples. / <p>QC 20181029</p>

<p dir="ltr">Safety and explainability are a top priority across many real-world applications of control in safety-critical systems. Networked dynamic systems are one sub-class of models that encompass many of the safety-critical systems in need of such safety guarantees. In this dissertation, we present our work in the safety-critical control of general non-networked epidemic processes, as well as our work on the modeling and analysis of networked epidemic-spreading processes. We then present a framework for the safety-critical control of networked dynamic systems including individual node vulnerability analysis and a CBF-based collaborative-safety condition. We develop a collaborative-safety framework that leverages high-order barrier functions to encode the effect of neighbors on individual safety requirements and demonstrate how this framework can be used in both epidemic models and in formation control problems. We provide an analysis on the finite-time convergence rate of our collaborative-safety algorithm in the special case of a tree structure network for a formation control application. Finally, we provide some concluding remarks and discussion on important directions for future work in the field of collaborative control for multi-agent autonomous systems.</p>

We present a motion control framework which allows a group of robots to work together to decide upon their motions by minimizing a collective cost without any central computing component or any one agent performing a large portion of the computation. When developing distributed control algorithms, care must be taken to respect the limited computational capacity of each agent as well as respect the information and communication constraints of the network. To address these issues, we develop a distributed, behavior-based model predictive control (MPC) framework which alleviates the computational difficulties present in many distributed MPC frameworks, while respecting the communication and information constraints of the network. In developing the multi-agent control framework, we make three contributions. First, we develop a distributed optimization technique which respects the dynamic communication restraints of the network, converges to a collective minimum of the cost, and has transients suitable for robot motion control. Second, we develop a behavior-based MPC framework to control the motion of a single-agent and apply the framework to robot navigation. The third contribution is to combine the concepts of distributed optimization and behavior-based MPC to develop the mentioned multi-agent behavior-based MPC algorithm suitable for multi-robot motion control.