Daniela Andone

Predictive control based on fuzzy model for steam generator

Poor control of the steam generator water level in the secondary circuit of a nuclear power plant can lead to frequent reactor shutdowns. Such shutdowns are caused by violation of safety limits on the water level and are common at low operating power where the plant exhibits strong nonminimum phase characteristics. This paper presents a framework for addressing this problem based on a new method of predictive control based on fuzzy model. It has been shown that in the case of nonlinear processes, the approach using fuzzy predictive control gives very promising results. The proposed approach is potentially interesting in the case of heat-exchangers and furnaces.

Advanced Control of a Steam Generator

Economic feasibility of a nuclear power plant requires smooth and uninterrupted plant operation in the face of varying electrical power demand. The feed-water system in a nuclear power plant is a major contributor to plant unavailability. The investigations about operation experiences of a power plant show that one of frequent causes of shutdowns is by violation of safety limits on the water level and is common at low operating power where the plant exhibits strong non-minimum phase characteristics. This paper presents a framework for addressing this problem based on a method of advanced control based on fuzzy model predictive control. Furthermore, fuzzy model based fault detection methods are elaborated envisaging fault tolerant control. Results from validation of the advanced control system are presented. A new concept of modular advanced control system designed for a seamless and gradual integration into the existing distributed control system is proposed

Potential and Application of Fuzzy Technology in Power Systems: A Survey

Abstract This paper presents practical applications of fuzzy sets methods to power systems control, design, operation and management. The paper includes an exposition of basic elements of fuzzy sets theory including basic properties, operations on fuzzy sets, fuzzy relations and their composition, linguistic variables, etc. Modern tools based on fuzzy sets theory to solve difficult power system problems such as: control applications, distribution system planning, load modeling and forecasting, in the case of unknown system structures and parameters or in the case of unknown process in absence of certain and reliable data are presented. The paper demonstrates that fuzzy methods can solve many difficult problems bringing new quality tor a more effective and reliable power supply.

Tandem Queueing Systems Maximum Throughput Problem.

In this paper we consider the problem of maximum throughput for tandem queueing system. We modeled this system as a Quasi-Birth-Death process. In order to do this we named level the number of customers waiting in the first buffer (including the customer in service) and we called phase the state of the remining servers. Using this model we studied the problem of maximum throughput of the system: the maximum arrival rate that a given system could support before becoming saturated, or unstable. We considered different particular cases of such systems, which were obtained by modifying the capacity of the intermediary buffers, the arrival rate and the service rates. The results of the simulations are presented in our paper and can be summed up in the following conclusions: 1. The analytic formula for the maximum throughput of the system tends to become rather complicated when the number of servers increase 2. The maximum throughput of the system converges as the number of servers increases 3. The homogeneous case reveals an interesting characteristic: if we reverse the order of the servers, maximum thruoughput of the system remains unchanged The QBD process used for the case of Poisson arrivals can be extended to model more general arrival processes.

A New Approach of Gray Images Binarization with Threshold Methods.

The paper presents some aspects of the (gray level) image binarization methods used in artificial vision systems. It is introduced a new approach of gray level image binarization for artificial vision systems dedicated to industrial automation – temporal thresholding. In the first part of the paper are extracted some limitations of using the global optimum thresholding in gray level image binarization. In the second part of this paper are presented some aspects of the dynamic optimum thresholding method for gray level image binarization. Starting from classic methods of global and dynamic optimal thresholding of the gray level images in the next section are introduced the concepts of temporal histogram and temporal thresholding. In the final section are presented some practical aspects of the temporal thresholding method in artificial vision applications form the moving scene in robotic automation class; pointing out the influence of the acquisition frequency on the methods results.

EVOLVED FUZZY CONTROL SYSTEM FOR A DRUM BOILER

Abstract Economic feasibility of a power plant requires smooth and uninterrupted plant operation in the face of varying electrical power demand. The feed-water system in a power plant is a major contributor to plant unavailability. The investigations about operation experiences of a power plant show that one of frequent causes of shutdowns is by violation of safety limits on the water level and is common at low operating power where the plant exhibits strong non-minimum phase characteristics. This paper presents a framework for addressing this problem based on a method of evolved control based on fuzzy model predictive control. Fuzzy model based fault detection methods are elaborated envisaging fault tolerant control. Results from validation of the evolved control system are presented. A new concept of modular evolved control system designed for a seamless and gradual integration into the existing distributed control system is proposed.

MODEL-BASED FAULT DETECTION AND ISOLATION OF THERMAL PROCESSES

Abstract The purpose of this model-based approach is the detection and isolation of sensors or other process components faults for a thermal process. One of the most powerful fault detection approaches is through parity equations. The applicability of the proposed method is illustrated on thermal plant in order to underline the advantages of this method. The model runs in parallel to the process, leading to symptoms with different sensitivities to a specific fault. After presenting the residual generator building method, a description of the thermal plant, the faults symptoms and FDI results are given.

Fuzzy rule base complexity reduction: a survey

The paper presents a survey of fuzzy rule base reduction techniques. The identification of fuzzy models from training data needs to consider both data fitness and complexity. The methodologies of model design can be mainly divided into two groups: the semantic-driven modelling and the data-driven modelling. The first model design type proposes models which are built based on expert knowledge. However, it is often the case that the model contains redundant rules and /or variables, so there is a need to reduce the redundancy of the model. The second model design type became more popular in the last decade partly due to the fact that fuzzy models were found to be able to approximate with arbitrary accuracy any continuous control function. These models usually use tremendously large number of rules and do not take into account the complexity of the model. This characteristic also emerged the issue of rule base reduction. The present paper summarizes the efforts done on the complexity reduction field.

Applications of QBD Process in the Study of Tandem Queueing Systems

Abstract This paper is considering the possibility of using the Quasi-Birth-and-Death process in studying a tandem queueing system, particularly on the problem of systems maximum throughput. The structure of this tandem queueing system consists of a serial link of buffers and servers. Naming phase the number of customers waiting in the first buffer and phase the state of the remaining servers, on obtain the equivalent QBD process. This model is then generalized for the MMPP case. The proposed model is used to study the problem of maximum throughput of the system. There are considered different particular systems, which were obtained by modifying the capacity of the intermediary buffers, the arrival rate and the service rates. The paper presents the results of the simulations and the obtained conclusions.

A New Process Control Strategy Based on Fieldbus

Abstract The paper offers details on the hardware and software architecture used in some industrial control applications based on Fieldbus Foundation specification. Three main results are presented: the configuration program placed on a Host Computer which can produce a control structure by selecting different function blocks defined as Fieldbus compatible Field Equipments, the specification of the necessary interconnections and by programming of their parameters; the software arhitecture that ensures the interface between the Host Computer and the Fieldbus Infrastructure and the facilities offered by the hardware support made with a dedicated Fieldbus Interface Board; the communication package programs ensuring the integration with the requirements of the ISO/OSI link layer specification and of the Fieldbus Message Specification. The description of the Graphic User Interface underlines the advantages in the necessary operations for the building of different control configurations and for their management. Finally, the paper does an analysis through simulation of real-time data transfer operations, offers a description of the proposed control strategy performances and discusses some ways for development.