cranfield university syed wakil ahmad intermittent fault diagnosis and health monitoring for ...

199 Pages·2017·3.93 MB·English

CRANFIELD UNIVERSITY

SYED WAKIL AHMAD

INTERMITTENT FAULT DIAGNOSIS AND HEALTH MONITORING
FOR ELECTRONIC INTERCONNECTS

THROUGH LIFE ENGINEERING SERVICES, SATM
DOCTOR OF PHILOSOPHY

THIS THESIS IS SUBMITTED TO FULFIL PhD
Academic Year: 2013 - 2015/2016

Supervisor: Dr Suresh Perinapanayagam,
March 2017
CRANFIELD UNIVERSITY

THROUGH LIFE ENGINEERING SERVICES, SCHOOL OF
AEROSPACE, TRANSPORT AND MANUFACTURING
Doctor Of Philosophy

PhD

Academic Year 2013 - 2015/2016

SYED WAKIL AHMAD

Intermittent Fault Detection and Health Monitoring for Electronic
Interconnections

Supervisor: Dr. Suresh Perinpanayagam
March 2017

This thesis is submitted in partial fulfilment of the requirements for
the degree of Doctor of Philosophy

© Cranfield University 2016. All rights reserved. No part of this
publication may be reproduced without the written permission of the
copyright owner.
ABSTRACT
Literature survey and correspondence with industrial sector shows that No-Fault-
Found (NFF) is a major concern in through life engineering services, especially
for defence, aerospace, and other transport industry. There are various
occurrences and root causes that result in NFF events but intermittent
interconnections are the most frustrating. This is because it disappears while
testing, and missed out by diagnostic equipment. This thesis describes the
challenging and most important area of intermittent fault detection and health
monitoring that focuses towards NFF situation in electronics interconnections.
After introduction, this thesis starts with literature survey and describes financial
impact on aerospace and other transport industry. It highlights NFF technologies
and discuss different facts and their impact on NFF. Then It goes into
experimental study that how repeatedly intermittent fault could be replicated. It
describes a novel fault replicator that can generate repeatedly IFs for further
experimental study on diagnosis techniques/algorithms. The novel IF replicator
provide for single and multipoint intermittent connection. The experimental work
focuses on mechanically induced intermittent conditions in connectors. This work
illustrates a test regime that can be used to repeatedly reproduce intermittency in
electronic connectors whilst subjected to vibration.
A novel ladder network algorithm is presented with an experimental setup that
detects IF in interconnection. It sends a sine wave and decodes the received
signal for intermittent information from interconnecting system. This novelty use
basic principle of amplitude modulation and could constructed with minimum cost.
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First, it describes the design and simulation to capture an intermittent fault
signature using a Pspice (electronic circuit simulation software). A simulated
circuit is practically verified by experimental setup. However, measurements are
presented using an oscilloscope for this circuit. The results of this experiment
provide an insight into the limitations of existing test equipment and requirements
for future intermittent connection detection technique. Aside from scheduled
maintenance, it considers the possibility for in-service intermittent detection to be
built into future systems, i.e. can intermittent faults be captured without external
test gear.
IFs are completely missed out by traditional monitoring and detection techniques
due to non-stationary nature of signals. These are the incipient events of a
precursor of permanent faults, manufacturing imperfections, or marginal/bad
design in electrical interconnection. Due to random and non-predictable nature,
the intermittent faults are the most frustrating, elusive, and expensive faults to
detect in interconnection systems. These are short duration which could be
detected by some specific techniques but these do not provide enough
information to understand the root cause of it. The novel approach that, extend
the previous ladder network, injects a fixed frequency sinusoidal signal to
electronics interconnection system that modulates intermittent fault if persist.
Intermittent faults and other channel affects are computed from received signal
by demodulation and spectrum analysis. It describes technology for intermittent
fault detection, and to find root cause of it. It also reports the functionally tests of
computational system of the proposed methods. The results demonstrate to
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detect and classify intermittent interconnection and noise variations due to
intermittency.
Non-stationary/Non linear nature of intermittent faults makes troubleshoot hard
with traditional equipment. Intermittent faults in electrical interconnection are
short duration, which could only be detected if test equipment has test coverage
both in time and frequency. The requirement of time and frequency coverage
window at particular instant makes them most frustrating, and expensive faults to
detect in interconnection system. One other novel advanced ladder network
approach described in preceding chapter. It injects a constant value signal and
spread it over a wideband using chirp signal, to electronics interconnection
system for diagnosing an intermittent fault, using channel sounding techniques.
This chapter describes a digital communication sounding techniques and its meth
prepared for detection and classification of intermittent fault, and channel
characterisation by its transfer function. This also reports the functionally tests of
the proto system of the proposed methods. The results demonstrate to detect
and classify intermittent interconnection and noise variations due to high
temperature or corrosion. This technique could be used in-situ with low amplitude,
a wideband signal over electronics interconnection. It provides the most effective
tool for continuously watching the wire system for the random, unpredictable
intermittent faults, the harbingers of disastrous electrical failure.
Keywords:
Transient spikes, Fault Diagnosis, No Fault Found (NFF), Signal processing
Algorithms for NFF, Communication approach for IF detection.
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ACKNOWLEDGEMENTS
First and foremost I am grateful to Almighty Allah who has given me a chance to
get the knowledge and philosophy of science and technology.
I would like to express my sincere gratitude to my advisors Dr Suresh, Dr
Mohammad, and Prof. Ian Jennions for the continuous support of my PhD study
and related research, for his patience, motivation, and immense knowledge. Their
guidance helped me in all the time of research and writing of papers and this
thesis. I could not have imagined having a better advisors and mentors for my
PhD study.
Besides my advisor, I would like to thank my thesis committee chairperson: Prof.
Elisa for her insightful comments and encouragement, but also for the hard
question, which canted me to widen my research from various perspectives.
My sincere thanks also goes to Chris Hockley, Andy Shaw, and Professor Raj
Kumar Roy who provided me an opportunity to join their team as researcher, and
who gave access to the laboratory and research facilities. Without their precious
support, it would not be possible to conduct this research.
I thank my elder brother Dr Jamil Ahmad for the stimulating discussions, for
intermittent signal detection using signal-processing techniques. I am also
grateful to other staff who enlightening me the first glance of research.
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Last but not the least, I would like to thank my family: specially my parents and to
my brothers for supporting me spiritually throughout writing this thesis and my life
in general.

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