6995

6537

كارشناسي ارشد

طراحي كاربردي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1390

نه، 100ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

سعيد بهبهاني

مهدي كشميري، محمدرضا فروزان

27/6/91

محمد دانش، مهدي مقيمي زند

1396/09/18

كتابنامه

مكانيك

مهندسي مكانيك

ID6537

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Fault Detection and Diagnosis of a Hydraulic System Controlled by Servo Valve Ali Rostami Ali rostami iut@gmail com Date of Submission 2012 02 19 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Saeed Behbahani behbahani@cc iut ac irAbstract Nowadays electro hydraulic servo systems are utilized as one of the most popularsystems in high technology industries such as aerospace and underwater applications Because of their application sensitivity significant attentions have been attracted towardresearches about the fault detection and diagnosis of these systems Obviously faultdetection and diagnosis results in preventing costly failures increasing safety andreliability decreasing the shutdown times of the system avoiding redundant componentreplacements and in general raising the performance of the system The case study of thisresearch is an electro hydraulic servo system containing a double acting cylinder adouble stage flapper nozzle servo valve and the associated controller The objective ofthis research is to provide a software redundant model based fault detection and diagnosissystem for two main common failures of this system including dropping the bulkmodulus due to aeration and internal leakage The nonlinear state space equations of thesystem are linearized using Taylor series Because of the nonlinearity of the state spaceequations the extended Kalman filter EKF algorithm is employed to estimate thesystem states Condition monitoring of the system is performed in two steps includingfault detection and fault diagnosis In the first step the residual between the measured andexpected healthy responses of the system is computed by summing the absolute errorsbetween estimated variables and measured values It is expected that the residual behaviordeviates from the natural behavior of the system in the presence of a fault Residualevaluation and fault detection is accomplished by means of Wald s sequential test Whenbulk modulus dropping and or internal leakage happen in the system it is observed thatthe accumulated values of the residual exceed the threshold value of Wald s sequentialtest while these values remain under threshold in natural healthy operation In the second step bulk modulus dropping is diagnosed by online estimation of bulkmodulus To achieve this objective the bulk modulus estimation is accomplished byadding it as a redundant variable to the state space variables and observing all the statesby means of another EKF By considering the piston position as the measured output ofthe system it is revealed that the bulk modulus is not correctly estimated because therank of the observability matrix is not equal to the number of state space variables hencethe system is not observable To overcome this problem the piston velocity and thepressures at two chambers of the cylinder are also measured as outputs In this case the

سعيد بهبهاني

مهدي كشميري، محمدرضا فروزان

محمد دانش، مهدي مقيمي زند