HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Artificial Intelligence, Fuzzy Logic and Controlexpert system is that it can be reproduced, distributed and the expertisebecomes easily available.The expert system can be looked at as a way of capturing the expertknowledge in specialized areas. However, the knowledge containedin an expert system is never complete and the output of an expert systemmust be validated.The expert system can capture diagnostic knowledge and code it ina software package that could then be used by operators to diagnoseroutine problems. A convenient way to represent the knowledge is in theform of a decision tree with each node in the tree representing a decisionto be made regarding the possible cause of the problem.Expert systems can serve as an additional tool for the inexperiencedoperator in diagnosis of faults. The expert system can diagnosethe cause of the fault and suggest actions to correct the situation.The user interface is critical as well as the type of queries made bythe expert system during the diagnostic session. Other critical parts includethe language and terminology used, the use of graphics and theresponse time of the system to entries made by the user.Statistical ControlOn-line statistical control is a good tool for monitoring if a processis operating normally. Many DCS systems generate quality controlcharts automatically but the operator has to decide the action to take ifsome abnormality is detected. This can be done using some type ofPareto analysis.On-line expert systems are sometimes called DCS-embedded expertsystems and they can do this diagnosis automatically. The DCS canfeed the current state of the process to the expert system at pre-specifiedintervals of time. Messages on the operator console provide alarms thatnot only point to the problem but also provide advice on possible causesand solutions.On-line expert systems may acquire their knowledge base automatically.This falls under the domain of machine learning. In a largeHVAC system there may be a large amount of data that is generatedfrom sensors. This data must be reduced to a form that can be used byan expert system.©2001 by The Fairmont Press, Inc. All rights reserved.