Yoshifumi Tsuge

A fault detection and diagnosis for the continuous process with load-fluctuations using orthogonal wavelets

Abstract Fault detection and diagnosis of a continuous process with input fluctuations such as load fluctuations can not be simply performed because of the difficulty of detecting the abnormality in the process, where normal values of state variables are uncertainly time-varying according to the input fluctuations. In this study, normal values of output variables are predicted by the use of the approximation function that is drawn from a family of orthogonal wavelets. Measured value of an output variable is classified to five-range signs (+, +?, 0, −?, −) by simultaneously performing two sequential probability ratio tests (SPRTs) based on the error residual between predicted and measured values: one test examines whether it is normal or higher than normal, the other examines whether it is normal or lower than normal. A combination of signs given to all the output variables is called a pattern, which is considered to represent an abnormal situation occurring in the process. Then, the fault diagnosis algorithm, based on signed directed graph (SDG), can deduce the fault origin that causes the pattern. The effectiveness of this approach is demonstrated through experiments by a tank—pipeline system.

Improvement in Strategy for Design of Heat Exchanger Networks using Multiagent Framework

Abstract In this study, a multiagent approach was applied into design of energy-saving chemical processes using pinch technology. We have introduced various strategies for simplification of heat exchanger network (HEN) to HEN design agents. Although large and complicated processes were optimized by the multiagent system, there were several cases where the HEN simplification had stopped at the insufficient and inadequate stages. Therefore we improved the strategy to make more preferable HENs. And we showed the effectiveness of improvement and our multiagent framework.

A multiagent approach for sustainable design of heat exchanger networks

Pinch technology is a familiar energy-saving technology in the chemical industries and has been incorporated in the process simulation software, however the skilled engineersf considerations are required to make preferable heat exchanger networks (HEN). We introduced a multiagent oriented simulation framework into the HEN design to save the energy usage and also reduce the CO2 emissions. In our framework, a number of gHEN design agentsh have their own strategies to optimize HEN respectively. In this paper, we show the effectiveness of our framework applying to two chemical processes.

Fault diagnosis method using a signed digraph for multiple origins of failures - evaluation of the diagnosis accuracy -

A fault diagnosis algorithm using a signed digraph as a model of a system is useful to real-time diagnosis of failures that occur in a chemical plant. It has been improved so much that it can find multiple origins of failures that occur in the plant at the same time. It is imperative that the diagnosis system be evaluated in the design phase of the system in advance for its practical use. In this paper, an accuracy of diagnostic results using the algorithm for multiple origins has been examined by its application to data obtained by the simulation of tank pipeline systems. The accuracy of diagnosis has been evaluated properly by the size of the greatest set of candidates

Application of strategy switching mechanism with improved strategy for heat exchanger network design

Abstract Heat exchanger network (HEN) is one of the major technique of energy saving. We have proposed a HEN design system using pinch technology and multiagent. In this system, the maximum heat recovery is derived from pinch technology. And then, an initial HEN can be obtained according to the AreaTargeting method in order to meet the maximum heat recovery. The initial HEN has complexity and a number of heat exchangers due to the AreaTargeting method. Therefore it is necessary to simplify the HEN without deterioration of the energy saving efficiency. In our system, simplification strategy is defined to prescribe the priority order of procedure and/or the part of HEN. The number and variety of resulted HENs increase along with the number of strategies. It is useful if a large number of HENs with wide variety is obtained because the preferable HEN must be different due to the process objectives or conditions. We implemented several HEN design agents (HENDAs) with different simplification strategies. In this study, we introduced several improvements in simplification strategy of HENDAs using strategy switching mechanism. Several HENDAs have their own strategy, and then they exchange the HENs on the way—that is “strategy switching” from the standpoint of a HEN. We investigated the effect of improvements in the simplification strategies and strategy switching mechanism.

Agent based fault detection using negative selection algorithm for chemical processes

In this study, a fault detection system for a chemical processes using agent and negative selection algorithm was proposed. The operational data using dynamic plant simulator were obtained to verify the effectiveness of our method. The simulations of fault detection were carried out. And also the results of simulation are presented in this paper.

Inter-process Heat Integration by Coordination among Agent Systems for Heat Exchanger Network Design

Abstract Pinch technology is one of the commonly used energy-saving technologies in chemical industries. We have proposed a simulation framework using multiagent into the design of heat exchanger network (HEN) to save the energy usage and to reduce the emissions of greenhouse gases. We set up several HEN Design Agents and each agent had different strategy to search candidate segments of HEN to modify. In our previous study, HENs for only a single process was optimized by the multiagent system at a time. However in general, there are some abutting chemical processes in a site. The interprocess heat integration, that is heat giving and heat receiving between a process and the others, is effective for energy saving in addition to the internal heat integration in a single process. In this study, we introduced Coordinator agent within the multiagent framework to achieve both inner-process and inter-process heat integration simultaneously.

Hierarchical Fault Diagnosis System Utilizing the Signed Directed Graph and the Extended Kalman Filter

Abstract The hierarchical fault diagnosis system containing a two- level strategy has been developed. This system involves the fault diagnosis method using signed directed graph as a qualitative model- based method and the fault diagnosis method using extended Kalman filter as a quantitative model-based method. In the upper-level strategy, a set of candidates for the cause of failure is obtained by use of the fault diagnosis method using signed directed graph. In the lower- level strategy, the most likely candidate to be the real cause of failure is selected out of the set of candidates by utilizing the extended Kalman filter. The efficiency of the present method is demonstrated by applying it to the tank-pipeline system.