Feedback control of bilinear distributed parameter system by input-output linearization

International audienceIn this paper, a control law that enforces the tracking of a boundary controlled output for a bilinear distributed parameter system is developed in the framework of geometric control. The dynamic behavior of the system is described by two weakly coupled linear hyperbolic partial differential equations. The stability of the resulting closed-loop system is investigated based on eigenvalues of the spatial operator of a weakly coupled system of balance equations. It is shown that, under some reasonable assumptions, the stability condition is related to the choice of the tuning parameter of the control law. The performance of the developed control law is demonstrated, through numerical simulation, in the case of a co-current heat exchanger. The control objective is to control the outlet cold fluid temperature by manipulating its velocity. Both tracking and disturbance rejection problems are considered

Controllability and Observability of a Large Scale Thermodynamical System via Connectability Approach

This study presents a new approach to determine the controllability and observability of a large scale nonlinear dynamic thermal system using graph-theory. The novelty of this method is in adapting graph theory for nonlinear class and establishing a graphic condition that describes the necessary and sufficient terms for a nonlinear class system to be controllable and observable, which equivalents to the analytical method of Lie algebra rank condition. The graph theory of a directed graph (digraph) is utilized to model the system, and the rule of its adaptation in nonlinear class is defined. Subsequently, necessary and sufficient terms to achieve controllability and observability condition are investigated through the structural property of a digraph called connectability. It will be shown that the connectability condition between input and states, as well as output and states of a nonlinear system are equivalent to Lie-algebra rank condition. This approach has been proven to be easier from a computational point of view and is thus found to be useful when dealing with a large system

Integrated design and control of chemical processes : part I : revision and clasification

[EN] This work presents a comprehensive classification of the different methods and procedures for integrated synthesis, design and control of chemical processes, based on a wide revision of recent literature. This classification fundamentally differentiates between “projecting methods”, where controllability is monitored during the process design to predict the trade-offs between design and control, and the “integrated-optimization methods” which solve the process design and the control-systems design at once within an optimization framework. The latter are revised categorizing them according to the methods to evaluate controllability and other related properties, the scope of the design problem, the treatment of uncertainties and perturbations, and finally, the type the optimization problem formulation and the methods for its resolution.[ES] Este trabajo presenta una clasificación integral de los diferentes métodos y procedimientos para la síntesis integrada, diseño y control de procesos químicos. Esta clasificación distingue fundamentalmente entre los "métodos de proyección", donde se controla la controlabilidad durante el diseño del proceso para predecir los compromisos entre diseño y control, y los "métodos de optimización integrada" que resuelven el diseño del proceso y el diseño de los sistemas de control a la vez dentro de un marco de optimización. Estos últimos se revisan clasificándolos según los métodos para evaluar la controlabilidad y otras propiedades relacionadas, el alcance del problema de diseño, el tratamiento de las incertidumbres y las perturbaciones y, finalmente, el tipo de la formulación del problema de optimización y los métodos para su resolución

Process and systems based methodologies related to control structure selection

This thesis is concerned with an important aspect of process control design, that is, the synthesis of the control structures. A review of the rapidly growing process methodologies' literature is presented and this leads to the identification of wider issues and new problems which are referred to as global instrumentation and forms the main subject of this thesis. The main objective has been the integration of existing process based tools and methodologies with a much more general approach of a systems and control theory character. The problem of Global Process Instrumentation concerns the selection of systems of measurement and actuation variables, found during the synthesis/design and operation of large-scale industrial processes/systems. The role of traditional instrumentation was considered but the emphasis has been on the systems aspects. In fact, instrumentation leads to the shaping of the final system and thus, is crucial in defining the control quality properties and operability characteristics of the final design. The development of these system aspects led to the emergence of an integrated framework for Global Instrumentation. An attempt was also made to abstract some results and formulate generic issues and problems, that would provide a wider scenario for activities in the future. Development of CAD to support the selection of control structures has been a major task undertaken here. The system aspects of Global Instrumentation are demonstrated by studying two specific problems that involve the study of the structural properties of interconnected systems as a function of local selection of sensors and actuators and the problem of well-conditioning badly structured transfer functions. The role of selection of inputs and outputs, on the overall shaping of composite structure properties, at the subsystem level, was examined, and the significance of an assumption related to interconnections, referred to as the completeness assumption, was investigated. Specifically, the significance of the deviations from the completeness, was the subject of the investigation. Matrix Pencil Theory was used to examine the controllability, observability and zero structure related properties of composite systems under partial or total loss of inputs/outputs at the subsystem level. Selecting subsets of the original sets of inputs, outputs to guarantee full rank transfer function, was also an issue that was examined. The above problems were presented as part of an integrated design philosophy that aims to explore the system structure. An integrated approach to the overall problem of control structure selection was formulated and open issues and problems were identified. It was based on the assumption that there exists a progenitor model of the linear type for the process, which, however, may not be well defined. Structural analysis of the system theoretic framework, the interaction measures and the results for evaluation of alternative decentralisation schemes were then used, to specify a step by step approach to the control structure selection. The problem of handling alternative criteria was also considered and basic elements of a system procedure were given. There are many open issues, which were identified and are still open and thus the proposed structural approach should be considered as the first step to the development of an integrated methodology that involves the following major steps: (a) Classification of system model variables and definition of well structured progenitor model. (b) Definition of effective input, output structure based on operability, controllability criteria. (c) Determining the structure of the control scheme by evaluation of alternative decentralised structures. An important part of the integrated methodology for control structure selection is the - so called - interaction analysis. It consists of a number of diagnostics and structural tests that help to restrict the choice of the best scheme. Several of these tests/methodologies were reviewed and some of them were further expanded. The outcomes obtained by these methodologies provided promising results. These results gave the motivation for the construction of a complete CAD package, the "Interaction Analysis Toolbox", written in MATLAB®t. This Toolbox provides many tools and diagnostics that can be applied during the design stages, for the evaluation of the various alternative control structures

Stochastic Bayesian Games for the Cybersecurity of Nuclear Power Plants

The goal of this research is to reduce the likelihood of successful attacks on nuclear power plants. Cyber-physical systems such as nuclear power plants consist of interconnected physical processes and computational resources. Because the cyber and physical worlds are integrated, vulnerabilities in both the cyber and physical domains can result in physical damage to the system. Nuclear power plants can be targeted by a variety of adversaries — each with a unique motivation and set of resources. To secure nuclear power plants and other cyber-physical systems, we require an approach to security that also accounts for the interactions of human decision-makers. This research uses a game-theoretic approach to nuclear cybersecurity. The cybersecurity of the plant can be viewed as a non-cooperative game between a defender and an attacker. The field of game theory provides a mathematical framework to analyze the interactions of the defender and attacker as both players seek to accomplish their objectives. In this research, a stochastic Bayesian game is used to optimize cybersecurity decision-making. A stochastic Bayesian game is a combination of a stochastic game and a Bayesian game. The stochastic elements of the game enable the consideration of uncertainty in the interactions of the attacker and defender. The Bayesian elements of the game enable the consideration of the uncertainty regarding the attacker's characteristics. This combination is useful for the analysis of nuclear power plant cybersecurity because it enables plant defenders to optimize their security decisions in the presence of uncertainty

NuScalen pienen modulaarisen reaktorin simulointi ja turvallisuustoiminnot

Small modular reactor (SMR) is a relatively recent concept in the nuclear power industry. Whereas the traditional large scale reactors are facing challenges due to their size, the small modular reactors intend to bypass the problems by utilizing aspects that their small size and modularity enables. However, the transition to SMRs includes many open questions. The energy industry and nuclear safety authorities are accustomed to large scale power plants, whereas experience with SMRs are shallow. This effectively creates a need for SMR studies, some of which this thesis aims to answer to. NuScale SMR was chosen as a focus of this thesis due to the concept’s reasonable level of maturity and its interesting utilization of passive safety systems. In the framework of this thesis, a NuScale SMR simulation model is built using the Apros program. The model is used to validate Apros calculation required for SMR simulation.The second objective of this thesis is to present the specific safety features of NuScale SMR that differ from current nuclear power plants. They are presented from a technical point of view and are briefly projected on Finnish regulatory guides. Feature projection reveals that many of the design features are fundamentally compatible with current guides with a few exceptions. In this thesis we perceive that among others the modular reactor mass production and passive functions could face challenges. The simulation results show that Apros code is capable of SMR and passive safety system modelling. However, the results also show that precise simulation of passive safety systems would benefit from further code development on those fields. The thesis also presents modelling guidelines that are beneficial when Apros is used for SMR modelling.Pienet modulaariset ydinreaktorit (SMR) ovat verrattain uusi konsepti ydinenergiateollisuudessa. Siinä missä tavalliset reaktorit kohtaavat huomattavia haasteita suuren kokonsa vuoksi, pienet modulaariset reaktorit pyrkivät kiertämään ne hyödyntämällä pienen kokonsa ja modulaarisuutensa mahdollistamia ominaisuuksia. Siirtyminen SMR:iin sisältää tosin myös avoimia kysymyksiä. Energiateollisuus ja ydinturvallisuusviranomaiset ovat tottuneet käsittelemään suuren kokoluokan laitoksia ja niihin liittyviä ilmiöitä, kun taas kokemukset SMR:istä ja niiden ilmiöistä ovat vähäisiä. Käytännössä tämä luo tarpeen SMR:iin kohdistuvalle tutkimukselle, jota tämäkin opinnäytetyö pyrkii tukemaan. NuScale SMR valittiin tämän työn tutkimuksen kohteeksi kyseisen konseptin kohtuullisen korkean valmiusasteen ja siinä hyödynnettävien mielenkiintoisten passiivisten ilmiöiden takia. Työssä rakennetaan Apros-ohjelmalla simulointimalli NuScalen konseptin mukaisesta SMR -koelaitteistosta. Mallin avulla validoidaan Aprosin SMR:ien simuloimiseen tarvittavaa laskentaa. Työn toinen tavoite on esittää NuScalen konseptille suunniteltuja erityisesti nykyisistä ydinvoimalaitoksista eriäviä ominaisuuksia teknisestä näkökulmasta, ja verrata niitä Suomen ydinvoimalain ja ydinturvallisuusohjeiden (YVL-ohjeet) turvallisuusvaatimuksiin. Ominaisuuksien projisointi paljastaa, että osa suunnitteluominaisuuksista sopii perustavanlaatuisella tasolla nykyisiin määräyksiin muutamin poikkeuksien. Työssä huomataan, että haasteita on muun muassa modulaaristen reaktoreiden massatuotannon ja passiivisten ominaisuuksien osalta. Simulointitulokset osoittavat Aprosin nykytilassaan kykenevän SMR:ien ja passiivisten turvallisuustoimintojen mallinnukseen. Tulokset kuitenkin osoittavat, että passiivisten systeemien tarkka simulointi hyötyisi kyseisien alueiden koodien jatkokehityksestä.Työssä myös esitetään mallinnusperiaatteita, joita olisi hyvä noudattaa, kun Aprosilla mallinnetaan SMR:iä

Mini-Workshop: Mathematics of Dissipation – Dynamics, Data and Control (hybrid meeting)

Dissipation of energy --- as well as its sibling the increase of entropy --- are fundamental facts inherent to any physical system. The concept of dissipativity has been extended to a more general system theoretic setting via port-Hamiltonian systems and this framework is a driver of innovations in many of areas of science and technology. The particular strength of the approach lies in the modularity of modeling, the strong geometric, analytic and algebraic properties and the very good approximation properties

A design procedure for a supervisory control structure in plantwide control

Abstract: This work presents a methodology for designing a supervisory control structure in Plant-wide Control (PWC). First, available PWC structures are discussed focusing on their drawbacks originated from the scarce flexibility and simplicity when implementing them in industrial environments. Additionally, the available control strategies involve decoupling of the process, losing all interactions information and therefore requiring more complex models inside the control structure to account for interactions among units. To overcome this, a hierarchical approach to PWC is proposed, introducing a two–layer control structure where dynamics on the regulatory layer are classified by hierarchical association considering that process dynamics and their set–points are optimized on the supervisory layer to achieve collaboration among Proportional–Integral–Derivative (PID) controllers in the regulatory layer. A dynamics hierarchy is established by means of the process Hankel matrix that quantifies the effect of all input variables over each state variable of the plant. Finally, the proposed methodology is applied to a Reactor–Separator–Recycle system for propylene glycol production, where a better process performance is reached using the hierarchical approach in comparison with the decentralized proposal.Resumen: Este trabajo presenta una metodología de diseño para estructuras de control supervisorio en control total de planta (CTP). Primero se discuten las estructuras de CTP resaltando sus limitaciones, como baja flexibilidad y simplicidad para su implementación industrial. Adicionalmente, estas estructuras involucran el desacople de las dinámicas del proceso, perdiendo la información sobre las interacciones del mismo y por ende, requiriendo modelos más complejos dentro de la estructura para dar cuenta de estas interacciones. Para superar estas limitaciones, se propone una estructura de control jerárquica, introduciendo una estructura de control con dos niveles, en la que las dinámicas en el nivel regulatorio son clasificadas jerárquicamente considerando el comportamiento dinámico del proceso y sus puntos de ajuste son optimizados en el nivel supervisorio alcanzando un esquema colaborativo entre los controladores Proporcional–Integral–Derivativo (PID) del nivel regulatorio. La jerarquía de dinámicas en el nivel regulatorio se establece por medio de la matriz de Hankel del proceso, que cuantifica el efecto de toda las variables de entrada sobre cada estado del proceso. Finalmente, la metodología propuesta se aplica para controlar un sistema Reactor– Separador–Reciclo para producción de propilenglicol, logrando unmejor desempeño usando la estructura jerárquica comparado con una estructura decentralizada.Maestrí