Deep Learning for Fault Detection and Isolation...Prognostics and Health Management Data Acquisition...

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Deep Learning for Fault Detection and Isolation

Hierarchical Networks for PHM

04.09.2018 SMC 2018 – © ZHAW – Gabriel Michau 1

Gabriel Michau1, Thomas Palmé2, Olga Fink1

1 - Zurich University of Applied Science, Switzerland2 - General Electric (GE) Switzerland

Smart Maintenance Conference 2018

Zürich

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04.09.2018 SMC 2018 – © ZHAW – Gabriel Michau 2

Prognostics and Health Management

Data Acquisition

Data Processing

Condition assessment(detection)

Diagnostics(identification)

Prognostics

Decision

• Features

• Raise early alarm

• Provide clear indication on the cause

Automatic process in a single approach

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Prognostics and Health Management

Data Acquisition

Data Processing

Condition assessment(detection)

Diagnostics(identification)

Prognostics

Decision

zhawChallenges of Critial Systems

PHM for critical (and complex) systems• Faults:

• Faults are rare • Faults cannot be afforded → preventive maintenance• Possible faults are numerous (possibly hitherto unknown)• Consequences of faults can be diverse

• System:• Heterogeneous data• Varied operating condition over long time scale• Unit Specificity

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zhawHierarchical Neural Networks

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“Health Indicator”

Trained with healthy condition monitoring data only

zhawTest in real case studies

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Healthy

Abnormal behavior 100 days before!

Generator with inter-turn failure

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Water Temperature Shaft Voltage Rotor Flux Rotor Flux

In agreement with • other models (AAKR, PCA) • with expert knowledge.

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At no additional cost!

Generator Diagnostics

zhawNew Challenges

What if, I don’t have enough training data?• What if my system is new (or has been refurbished)?• What if I am expecting operating conditions to change?

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⇒Use data from other similar systems

Fleet approach to PHM (from manufacturer perspective)

zhawExample with a stator (vane failure)

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Long training Short training

Winter

zhawHealthy Stator

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Summer

Long training Short training

zhawSubfleet selection

• What data do I need?• Not everything at once because

1. It is too much2. It will contains operating points that are not relevant to my unit3. Completely different operating conditions might hide faults

⇒I need data relevant for my unit.

• Within a (manufacturer) fleet, all units are similar. ⇒Need to identify other units with similar operating conditions

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zhawSubfleet selection

• Multi-dimensional datasets comparison• Resource and time consuming (multi-dimensional distance and distributions)• Difficult (number of nearest neighbors evolves as n.D)

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zhawSubfleet selection

• Solution: The Hierarchical Network has proven to be efficient in measuring how well the test data correspond to the training data.

⇒Idea: 1. Train HELM on one unit, test with data from other units2. select those that are detected as similar.

⇒Computationally efficient: • HELM takes all dimensions and output a single indicator• 1 HELM to train per unit (instead of N2 dataset comparisons)

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zhawProposed Methodology

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HELMNew Stator “Healthy”

Training

1 – Train HELM on “new” stator

zhawProposed Methodology

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TrainedHELM

New Stator

Test

Healthy Stator

1 – Train HELM on “new” stator2 – Test all other Stator

zhawProposed Methodology

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HELMHealthy Stator “Healthy”

Training

1 – Train HELM on “new” stator2 – Test all other Stator

3 – Train HELM with other stator

zhawProposed Methodology

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TrainedHELM

Healthy Stator

Test

New Stator

1 – Train HELM on “new” stator2 – Test all other Stator

3 – Train HELM with other stator4 – Test with “new” stator

zhawProposed Methodology

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1 – Train HELM on “new” stator2 – Test all other Stator

3 – Train HELM with other stator4 – Test with “new” stator

5 – Dissimilarity measure:

Healthy StatorNew Stator

HELM

zhawSimilar datasets

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Similar dataset if d below a threshold

Need to allow for more than 20% of dissimilar point to find onesimilar dataset for half of the dataset

This fleet has very dissimilar unitsDifficulty to find subfleets

zhawIndividual Asset Monitoring

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HELMHealthy Stator

Subfleet “Healthy”

Training

New Stator

1 – Train HELM on “new” stator subfleet

zhawIndividual Asset Monitoring

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trainedHELM

1 – Train HELM on “new” stator subfleet

2 – Monitor new data from individual asset

Test

New StatorNew data Health

Healthy StatorSubfleet

New Stator

zhawExamples

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zhawExamples

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zhawExamples

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zhawExamples

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zhawWhat is coming next?

• Fleet Feature analysis: What can be learned on the fleet?

• Transfer learning: What if my fleet have several versions of my system? (eg., not exactly the same data recorded)

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Thanks for your attention

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Acknowledgements