29 October 2004 Structural Health Monitoring for Aerospace Vehicles CENS Seminar Structural Health Monitoring Structural Health Monitoring for Aerospace Vehicles for Aerospace Vehicles Mark Hedley Mark Hedley CSIRO ICT Centre CSIRO ICT Centre Australia Australia Research Partners: CSIRO Industrial Physics CSIRO Manufacturing & Infrastructure Technology NASA Langley Research Center Boeing Phantom Works Defence Science & Technology Organisation (DSTO)
Transcript
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Structural Health Monitoring for Structural Health Monitoring for Aerospace VehiclesAerospace Vehicles
Mark HedleyMark HedleyCSIRO ICT CentreCSIRO ICT Centre
AustraliaAustralia
Research Partners:CSIRO Industrial PhysicsCSIRO Manufacturing & Infrastructure TechnologyNASA Langley Research CenterBoeing Phantom WorksDefence Science & Technology Organisation (DSTO)
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Commonwealth Scientific and Industrial Commonwealth Scientific and Industrial Research Organisation (CSIRO)Research Organisation (CSIRO)
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Where have we come from in the last 100 Where have we come from in the last 100 years?years?
Wright Bros., Kitty Hawk, 17 December 1903
Boeing 7E7 2008
Where will we be in 50-100 years?Where will we be in 50-100 years?
Boeing 7471970s
Where are we now?Where are we now?
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Structural Health Monitoring for Aerospace Vehicles
This requires multi-functional material and This requires multi-functional material and structuresstructures
Active/sensory/structural Embedded intelligence
Biomimetic functionality is being explored for Biomimetic functionality is being explored for ways to achieve thisways to achieve this
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
What is structural health monitoring?What is structural health monitoring?The ability to monitor damage, assess structural health and
diagnose damage conditions
What is structural health management?What is structural health management?Taking action is response to damage, form a prognosis, make a
decision and take remedial action
How do they differ from current practice?How do they differ from current practice?Currently based on periodic inspection
First Step - Conditioned Based Maintenance
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Outline of talk:Outline of talk:
1.1. MotivationMotivation
2.2. General requirements and principles of future SHM systemsGeneral requirements and principles of future SHM systems• Requirements for a SHM system• Proposed Architectures• Agents and Sensing
3.3. Example: the CSIRO multi-agent test-bedExample: the CSIRO multi-agent test-bed• Objectives and simple damage scenario• Architecture and hardware• Multi-agent algorithms• Current system status
4.4. Summary and conclusionsSummary and conclusions
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Acknowledgements:Acknowledgements:
A team of ~ 20 people at CSIRO (CIP and the ICT Centre) has contributed the ideas and done all the work I will describe here. The major contributors have been:
Tony FarmerAndy ScottGraeme EdwardsMark HedleyMark JohnsonChris LewisPhil ValenciaNigel HoschkeMikhail ProkopenkoPeter WangVadim GerasimovGeoff PoultonGeoff James
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
A few bonded sensors connected to a processor or
data logger
Where do we want to go with SHM?Where do we want to go with SHM?
• Integrated / embedded sensors • Mobile sensors• Large numbers of sensors (10ⁿ) • Autonomous diagnostics & prognostics • Intelligent decision-making• Remediation strategies / self-repair • Sensory / active materials• Robust, adaptive, reconfigurable.
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General requirements and principles of future SHM systems.General requirements and principles of future SHM systems.
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Functional Requirements for a SHM System:Functional Requirements for a SHM System:
Detection (or deduction) of damage Evaluation of damage Diagnosis of damage
Sensing, interpretation, learning
Monitoring
Damage models, prior knowledge, learningOptions for action: repair or remediation.
Prognosis for structure Remediation decision
Decision-making
Identification of threats What is the operational nature and environment of the structure? What are the potential sources of damage? Where might they occur? Can the threat be detected and avoided before damage occurs?
Actions What responses are appropriate, achievable? Nothing, report only, modify operational conditions, repair, abandon ship!!
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Application Requirements for a SHM System:Application Requirements for a SHM System:
Robustness: Must be able to operate effectively in the presence of damage Scalability: System may contain a very large number of sensors, processors, structural elements, etc. Reliability: Must be more reliable than the vehicle structure
Validation/certification is a major issue as systems become more complexThis is a problem for all types of control and safety systems
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Specific Characteristics Needed for a SHM System:Specific Characteristics Needed for a SHM System:
1. Wide range of reaction/response times: Milliseconds – impact damage, pressure leaks, … Seconds – cracks, disbonds, composite degradation, … Hours (or longer) – fatigue, corrosion, creep, wear, …In many cases, the required reaction time depends on how early thedamage (or threat) was detected.
2. Range of decision-making processes and response types: “Panic” or reflex response (no reasoning) Considered, reasoned (intelligent) response
3. Broad spectrum of environments, risks
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Robust network topology Scalable Distributed Processing Wired or Wireless Limited Network Power
The ideal network architecture is a
Sensor Network:Sensor Network:
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
autonomous agents that interact with each other and with their environment each agent is incapable of solving a problem alone can display self-organization, or complex emergent behaviour inherent redundancy, no single point of failure well suited for handling evolving, dynamic problems
The ideal distributed processing architecture is a
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Features Complex vs Complicated Characterised by Emergent Behaviour No processor has global view
Issue Design agent properties to obtain desired emergent
behaviour using only local knowledge
We design complexity out of engineering We design complexity out of engineering structures because we don’t yet know structures because we don’t yet know how to control it!how to control it!
Complex SystemsComplex Systems
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Agents in a Multi-agent-based SHM system:Agents in a Multi-agent-based SHM system:
Agents are autonomous, but are only aware of their local environment – an agent can’t see the “big picture”, can’t solve the “big problem”.
Agent functions: Controls a suite of sensors and/or active elements Processes sensor data to infer local damage information Communicates with other agents (neighbours only) Contributes to emergent response
Agents may be static (embedded) or mobile (robotic)
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Sensing in a Multi-agent-based SHM system:Sensing in a Multi-agent-based SHM system:
Sensing strategies in a SHM system may be very different from “traditional” periodic inspection-based NDE
Continuous monitoring vs. periodic inspection– Aim to detect damage at early stage
Primary vs. secondary sensing Dense vs. representative sensing Use of network as a sensor
Sensor characteristics: Direct vs. indirect (damage inference/likelihood) Passive vs. active Local vs. remote Embedded vs. mobile
The only certainty is that a multi-sensor strategy will be needed!!
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Outline of talk:Outline of talk:
1.1. MotivationMotivation
2.2. General requirements and principles of future SHM systemsGeneral requirements and principles of future SHM systems• Requirements for a SHM system• Proposed Architecture• Agents and Sensing
3.3. Example: the CSIRO multi-agent test-bedExample: the CSIRO multi-agent test-bed• Objectives and simple damage scenario• Architecture and hardware• Multi-agent algorithms• Current system status
4.4. Summary and ConclusionsSummary and Conclusions
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Example: the CSIRO/NASA Multi-Agent Test-bedExample: the CSIRO/NASA Multi-Agent Test-bed
Objectives:Objectives:
• Purpose: to experiment with and demonstrate concepts for an intelligent vehicle health monitoring system within a relatively simple environment.
The prime focus, initially, is on systems issues (conversion of data to information, diagnosis, prognosis, intelligent decision-making, … ), rather than on particular sensing issues.
• Intended as a research tool and demonstrator for concepts and techniques – to explore the possibilities.
• NOT intended to be a prototype of a practical system. Constraints of weight, cost, power consumption, EMI, … not considered.
• High level of processing power for maximum flexibility.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Damage scenario:Damage scenario:
• Simple damage environment: impacts from fast particles, such as micrometeoroids or space debris.
• 1st stage of development: aim to detect, locate and evaluate the effects of particle impacts anywhere within the aluminium skin of a “vehicle”.
• Later stages will develop diagnosis, prognosis and remediation decision-making, incorporate other sensors & strategies, damage scenarios, etc.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Damage Simulation:Damage Simulation:
• As the hardware will not be flown in space, other sources of impacts are required:
• A light-gas gun was used to fire 1 mm diameter stainless steel ball bearings to speeds up to 1.5 km/s
• The focused pulse from a Nd:YAG laser (wavelength 1.06 nm) with duration 8 ns and energy up to 0.5 J provides a good simulation of a normally incident non-penetrating impact
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Architecture and Hardware:Architecture and Hardware:Vital statistics:• Hexagonal prism• 192 agents (cells)• 1 mm Al sheet skin• Cells ~100 x100 mm• Regular mesh• 4 x 2.5 mm dia.
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Cell Hardware:Cell Hardware:
++
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System Hardware:System Hardware:
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Impact Localisation:Impact Localisation:
• Lowest order extensional plate wave detected (about 5.3 km/s)
• Localisation within cell based on triangulation using time of arrival difference for the four sensors
• Table lookup for fast calculation
• Error few mm within rectangle, grows quickly outside
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Communication Communication Protocols:Protocols:
Workstation• Agent to Agent (only to neighbours)
• Between agent and workstation (asymmetric) – not required for operational network (network query)
• Agent to local neighbourhood
• Between static and mobile agents
• Don’t require communication between arbitrary agents!
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Communication Communication Protocols:Protocols:
Serial Port Device Driver
Data Link Layer
Link ControlProtocol
CD FloodProtocol
NodeControl
DataTransfer
Simple AgentProtocol
AgentSoftware
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Application Layer
UDP (Simulated Nodes)
Master Route Protocol &Master Flood Protocol
Nodeand
NetworkStatusMonitor
Re-programNodes
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Network discovery by the visualizer of the 188 physical cells. There are four cells missing as a small window was left in the demonstrator to allow observation of the inside.
Visualisation – Building the NetworkVisualisation – Building the Network
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Current flow in the demonstrator, showing flow into and out of cells, around absent cells, and the net current across cell edges
Visualisation - Current FlowVisualisation - Current Flow
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Visualisation – 3D and BoundariesVisualisation – 3D and Boundaries
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Multi-Agent Multi-Agent Algorithms:Algorithms: Aim to develop local agent algorithms that will result in desirable
emergent behaviour of the collective system of agents.
Simple algorithms developed so far:– Impact boundaries– Damage networks– Clusters based on damage severity– Self-replication of damage region
Entropy-based metrics developed to measure stability of emergent behaviour.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Impact Boundaries: Impact Boundaries: simple, involves single cells only.
White cells: direct impact damage
Red cells: indirect damage
Blue cells: form boundary between damaged and undamaged regions.
White lines: form continuous, connected damage boundary.
May be used to route messages around a damaged region.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Impact Networks: Impact Networks: involves groups of cells.White cells: direct impact damage.
Algorithm simulates ants foraging for food. Forms shortest path between “food sources” (and avoiding obstacles).
Green cells: pheromone levels.
May be useful for damage evaluation, e.g. guidance of a mobile sensor or repair agent.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Current System Status:Current System Status:
• We have built a platform for undertaking research in SHM
• Dense wired sensor network for impact detection
• 192 Nodes and 4 Sensors per Node
• We have undertaken initial research in the use of multi-agent systems for distributed processing for structural health diagnostics
Underlying research issue is to develop techniques for multi-Underlying research issue is to develop techniques for multi-agent-based knowledge management, learning and emergent agent-based knowledge management, learning and emergent decision-making.decision-making.
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Current Developments:Current Developments:• Mobile robot for
secondary inspection and repair
• Wireless communication using acoustics through skin and RF (802.15.4)
• Damage evaluation using active acoustic sensors
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Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Future Developments:Future Developments:
• Secondary Inspection
• Actions• Reflex response• Intelligent Response
• Detection of other damage modes
• Other materials (e.g. composites, metal foams)
29 October 2004
Structural Health Monitoring for Aerospace Vehicles
CENS Seminar
Conclusion:Conclusion:
We can expect to see large qualitative as We can expect to see large qualitative as well as quantitative changes in SHM in well as quantitative changes in SHM in coming yearscoming years
The extent and directions will depend on The extent and directions will depend on advances in:advances in:
― Intelligent systemsIntelligent systemsThis will be an enabling technology not This will be an enabling technology not
just for more efficient maintenance, but just for more efficient maintenance, but for radically different aerospace vehiclesfor radically different aerospace vehicles
