15990

14281

كارشناسي ارشد

كنترل

اصفهان : دانشگاه صنعتي اصفهان

1399

يازده، 69ص. : مصور، جدول، نمودار

ايمان ايزدي

محسن مجيري، احسان يزديان

1399/08/19

كتابنامه

مهندسي برق

مهندسي برق و كامپيوتر

1399/08/24

2647878

Detection of changes in the distribution of a variable using generalized delay timer Mohammadreza Heidari mohammadreza heidari@ec iut ac ir August 15 2020 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Iman Izadi iman izadi@iut ac ir Abstract Industries require preparations to detect faults timely for optimal and proper performance Alarm systems have beenused for that purpose These systems function is to inform the operator of the occurrence of abnormal conditions in theprocess The most common approach in the industry to detect abnormal conditions is to compare a variable s value with apredetermined threshold When the value of a variable exceeds the threshold an alarm is activated and notifies the operatorof a fault On the other hand the operator should ideally receive only one alarm for each fault If the number of receivedalarms increases it will be impossible for the operator to detect the real alarms Therefore what is essential in alarm systemsis the timely detection of faults the management of alarms and the response to critical alarms False alarm rates missedalarm rates and detection delays are the most important indices for evaluating alarm systems Today there are many methodsto improve alarm systems performance and these methods are expanding Using these methods reduces the false alarm rateand the missed alarm rate but increases the detection delay Therefore in designing alarm systems a compromise betweenalarm system evaluation indices should be considered Delay timer filtering and deadband are some of the methods thatfall into the category of data processing methods In the conventional method the decision to activate and deactivate thealarm is made by examining one sample However when delay timer is used unlike the conventional method the decisionto activate and deactivate the alarm is made by examining a sequence of samples In this thesis the delay timer methodand its generalization are reviewed An idea to detect changes in the probability density function based on the area of theprobability density functions of fault free and faulty states and selection of the thresholds using generalized delay timer ispresented Finally an algorithm for designing the generalized delay timer based on the presented idea is proposed to betterdetermine the parameters of the timer Key Words Alarm systems False alarm rate Missed alarm rate Detection delay Generalized delaytimer

ايمان ايزدي

محسن مجيري، احسان يزديان