seminar nima yousefi 2015 engineering university of alberta
TRANSCRIPT
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System Level Monitoring for
Time-Varying Conditions
with Applications to Shovels
Nima Yousefi
Supervisor: Prof. Mike Lipsett
August 18, 2015
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Outline
• Introduction
• Problem overview - Motivations
• Tools and Methods
• Design of the test equipment: Shovel rig
• Soil Property Estimation
• Condition Monitoring and Fault detection
• Conclusion
• Future work
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Introduction
• Situational AwarenessIdentify, process, and analyze the critical information about the mission
• Equipment that interact with their environment
Loading units, Wind turbine, etc.
• Using sensory data for the assessment of the operating
environment, and equipment condition
Examples: Interaction Force, Energy balance (In/Out)
Introduction
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Monitoring environment/equipment
• Operating modes (one or multiple states),
• What can change in the equipment or the environment
• What are the critical parameters
• Normal operating envelope for the monitored parameters
• How Internal/external change affects the monitored parameter
• There is a desire to be able to detect the change
• Once change is detected, what corrective course of action
Repair/maintenance Vs. Change of operating mode
Introduction
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Limitations of current systems
• Condition monitoring in mining equipment have only been
implemented for a limited number of subsystems
- OEM systems for Engine, Lubrication system, electrical, etc.
• Very few studies have investigated structural damage monitoring
- Difficult to monitor
- Some studies on the drive train monitoring – Still in progress
• ‘Time-varying behavior’ and ‘Active ground movements’ limits the
application of conventional vibration monitoring
- Alternative parameters need to be investigated
- Application of advanced data processing methods needs to be studied
Motivation
Motivation
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Motivation
Main Contributions
• Development of a test rig for the study of the structural
integrity in time-varying systems
- Simulates the behavior of a loading unit: non-stationary behavior, Soil-tool interaction
- Allows multiple structural damage
- Can be used for characterizing the loading area condition
• Using an energy based method (i.e. acceleration signal) for
monitoring the condition of the equipment
- It works on the energy principals: Minimized negative effect of environmental Vib.
- Applicable to equipment with rotating or reciprocal mechanisms
• Development of a property estimation algorithm for characterizing
mechanical properties of the environment
- Improved prediction of the cutting force: better dig planning
- Increased load area situational awareness
Motivation
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Tools and Methods
Methodology
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I. Shovel Rig Designo Mechanical design
o Instrumentation and DAQ
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Test rig design
Test rig design
• Shovel assembly is based on off-set crank-slider
• It is coupled with a gearbox system (drive train)
• Rotating - Reciprocal
• Task-Specific considerations
Offers soil-tool interaction via a slow cutting/pushing action
Allows variable attack angles α, and depth of penetration H
Accommodates a few structural defects
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Commissioned test rig
Test rig design
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II. Environmental Monitoringo Soil-Tool Interaction Model
o Medium Property estimation
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The interaction force applied by the ground engaging
tool can be modeled
Machine-Ground Interaction
Property Estimation
Coulomb’s Earth Pressure Model
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Soil property estimation
Property Estimation
• One way to estimate soil properties from the
interaction force is using the inverse model
Models are too complex to be analytically inversed
Minimize the error between the predicted and the actual
measured force
Non-unique estimates
• An alternative method is to use force readings and
solve the non-linear interaction model iteratively
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Cutting force measurements
• Experimental set up 3 Medium types were studied: Glass beads, Play sand, Oil sand
Lab measurement of the friction angles
Soil cutting trials at 70o and 80o attack angle
Cutting forces are measured
- Force pairs are fed into the estimation algorithm
Produce estimates for friction angles and Cohesion
Property Estimation
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• Used Newton-Raphson for solving the system of
non-linear equations
Estimation results
Property Estimation
70
80
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III. Condition Monitoringo Energy dissipation and vibration
o Feasibility study for monitoring
o Advanced methods for processing
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• As the energy flows into mechanical
subsystems, parts of it turns into
energy losses: i.e. heat, vibration
• In rotating and reciprocal systems,
vibration can exist even under normal
conditions
• Geometrical defects influence the transmitted vibration
• Structural faults can cause energy losses too, which can
be traceable applying principles of energy conservation
Energy flow in/out of the system can be monitored by
monitoring the acceleration signal of the slider
Energy dissipation and Vibration
Condition Monitoring
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Proof of concept
• Numerical model in CAD
Fault free system
Faulty element
• Analyzed in MATLAB: Evaluated the residue
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Structural Faults
Condition Monitoring
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Time series
Condition Monitoring
• Slider’s displacement
• Slider’s Acceleration,
• Crank’s rotational speed,
• Total shaking force
Displacement
Acceleration
Angular Velocity
Shaking Force
Normal Fault A Fault B Fault C
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• Statistical feature extraction
• Dimension reduction using Principal Components Analysis
• Four classes can be separated using a linear classifier
• Acceleration signal carries fault signatures
• How and when does each fault manifest itself?
Time domain Analysis
Condition Monitoring
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Frequency domain analysis
• Operating data Motor nominal speed constant at 126 rpm (2.1 Hz)
Output shaft rotated at 37.8 rpm (0.63 Hz) [reducer GB: 0.3]
• Non-stationary condition Variable Speed & Variable Loading
Fourier transform is not the proper tool
Condition Monitoring
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Time-Frequency analysis
• Hilbert-Huang Transform
Empirical Mode Decomposition
Hilbert-Huang Spectrum 𝐻(𝜔, 𝑡) (HHS)
Marginal Hilbert Spectrum ℎ(𝜔) (MHS)
Condition Monitoring
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Intrinsic Mode Functions (IMF)
Condition Monitoring
Normal Fault in Joint Housing Fault in Connecting rod Fault in Rolling Element
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Hilbert Spectrum 𝐻(𝜔, 𝑡)
Condition Monitoring
Normal Fault A
Fault B Fault C
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Marginal Hilbert Spectrum ℎ(𝜔)
2x
5x
8x
1x
1x
2x
4x
5x
3x
𝟓
𝟐x
𝟕
𝟐x
𝟑
𝟐x
Condition Monitoring
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T-F Analysis Summary
• IMFs allow to locate the exact moments when the fault is
present, and its magnitude
• Fault type affects the time window required for detection
Looking only at the first 10 seconds, Fault A would have been
hidden to both analysis methods
Some faults are present in the entire dataset, while some only
activate under certain conditions
• Some hidden features of the signal can be unveiled
investigating the IMFs of interest with MHS
• T-F methods such as HHT can provide useful information
about the non-stationary systems that complements the
time-domain analysis
TF Summary
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Conclusions
• Acceleration signal carries enough information for monitoring
the structural integrity of the equipment
• Hilbert-Huang Transform is an effective tool for monitoring
the condition of the non-stationary system of interest
exposed to structural defects
• Ground-tool interaction force can be used for characterizing
the condition of the environment
• System level monitoring studied in this work, presents an
opportunity to expand the application of situational
awareness
Conclusions
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Future work
• Higher fidelity soil-tool interaction models
• Nonlinear solvers that can handle more parameters
• Perform condition monitoring
Under variable speed
In presence of external loading
Using angular velocity as a monitored parameter
• Use improved decomposition method, i.e. EEMD
• Use additional features
Statistical analysis of the T-F data
Fusion of the features from both T and T-F
• Develop tools and methods for applying the learnings of
this research in industrial application
Future work
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Acknowledgment
• Dr. Mike Lipsett
• MECE machine shop: Roger Marchand, Bernie
Faulkner, Albert Lee
• Contributions from
James Hendry ………… Design and drawings
Paul Pineda ……………. Material requisition
Amanda Kotchon ……… Geomechanics testing
• Dr. Bob Koch
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Thank you.