الفهرس 
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Abstract
Abstract
Electromechanical and Electrohydraulic systems and equipment are often
faced with unexpected changes, such as component fault and variation of
operating conditions. Fault diagnosis is an area that has seen substantial
growth in the last few decades. The purpose for implementing Fault
diagnosis in industry is to increase productivity, decrease maintenance cost
and increase safety. Therefore, fault diagnosis can be used not only for
planning maintenance but also for allowing the selection of the most
efficient equipment to minimize operating cost. The main scope of the
present research work deals with fault diagnosis in hydraulic systems. The
present research work considers a Hydrostatic Transmission as a base for
analysis and diagnosis. For simulation purpose, a mathematical model has
been developed. The dynamic behavior of the hydrostatic transmission is
studied.
Changing some system parameters causes abnormal behavior in the
performance of each component. The overall system is studied
experimentally and theoretically. The experimental results displayed are in
a good agreement with the simulation results obtained from the present
mathematical model. The results from experiments on a system with
artificial fault and another system with no fault are presented. The pressure,
flow and temperature ripple waveforms are compared for the two systems.
A comparison of these three characteristics for a system with real fault and
one with the artificial fault showed very good correlation. Accurate
detection of fault in a hydraulic system is a crucial and equally challenging
task. A fuzzy logic approach is developed for the diagnosis of simulated
faults in hydraulic power systems. The fault severity of the system is
evaluated based on the membership functions and rule base developed by
the fuzzy logic system. The decision of whether a fault has occurred or not
is upgraded to ‘what is the severity of that fault on the output. Simulation
results showed that fuzzy logic approach is more sensitive and informative
regarding the fault condition.