high-rate structural health monitoring and prognostics: an

1Distribution A. Approved for public release; distribution unlimited. (96TW-2021-0019)

High-Rate Structural Health Monitoring and Prognostics: An Overview

J a c o b D o d s o nM u n i t i o n s D i r e c t o r a t e

A i r F o r c e R e s e a r c h L a b o r a t o r y

A u s t i n D o w n e yD e p a r t m e n t o f M e c h a n i c a l E n g i n e e r i n g

U n i v e r s i t y o f S o u t h C a r o l i n a

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M i c h a e l T o d dD e p a r t m e n t o f S t r u c t u r a l E n g i n e e r i n g ,

U n i v e r s i t y o f C a l i f o r n i a , S a n D i e g o

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V i r t u a l P r e s e n t a t i o n


Motivation – Air Force

Air Force Weapon Components – Extreme Mechanical Environments

Input Characteristics• Repeated shocks• Multiaxial• Short rise time/high

frequency• Short & Long duration


Blast against civil structures Automotive impact and crashes

High Speed aircraft and airframes Lightning Strikes on aircraft

Definition – High Rate Dynamics

Hong, J. et.al. Introduction to state estimation of high-rate system dynamics. Sensors, 18(2):217, Jan 2018.

A dynamic response from:

• high-rate ( < 100 ms) and• high-amplitude (acceleration > 100 gn)

event such as a blast or impact.

High-rate dynamics contains:

1. Large uncertainties in the external loads;2. High levels of non-stationarities [in the

structure] and heavy disturbances;3. Unmodeled dynamics from changes in

system configuration.


Definition – “High Rate” TimescalesThe high-rate structural health monitoring problem has multiple time-scales to address:

Time scales of… Time Scales Examplesduration of the event 30 µs – 100 ms Structural loading - blast, high-speed impact, automotive crashsensor response 3 µs – 10 µs Accelerometer, strain gage, etc.different physical behavior regimes 250 µs – 1 sec Energy propagation, structural resonancealgorithm execution and decision-making

100 µs – 1 ms Damage detection, uncertainty quantification, state awareness, decision making

1. High-Rate – 1 ms2. Very High-Rate – 100 µs3. Ultra High-Rate – 1 µs

We have defined 3 timescale regimes for the time elapsed between event detection and decision-making (i.e. latency):

Current Goal


Technical Challenges of HR-SHMGoal: Determine the condition of a structural system and make system decisions in less than a millisecond, while the structure sustains unknown/unmeasured, high-magnitude, and short-duration impacts

Lack of System KnowledgeNeed to [partially] understand physics and approximate dynamics for structural awareness

Technical Challenges:Adequate SensingNeed to achieve multiresolution (time, space, and frequency) sensing awareness

High Variability and Uncertainty in LoadingDue to unmodeled dynamics occurring during high-rate dynamics; Need to be able to establish environmental awareness

Limited resources for algorithm implementationNeed to identify algorithms and hardware for 1 ms timescales while maintaining energy awareness


Technical Objectives and Approaches to enable HR-SHMTo achieve…

Sensing Awareness:• Non-inertial and non-contact sensing methods• Full field sensing algorithms and data fusion, contextual-artificial intelligence approaches

Structural & Environment Awareness:• Physics-enhanced machine learning (PEML) models• Real-time fusion of high-speed dynamic data augmented by model-based data

• Model reduction and model-updating (offline and real-time) approaches• Uncertainty quantification (UQ) methods to enable decisions connected to confidences

Energy Awareness:• Cognitive sensing – configuring sensors and hardware to measure at various timescales

• Combining both hardware and software to enable high-rate executions

System Development• Experimental Validation for high-rate algorithms

• Suite of experimental data sets and apparatus for different aspects of the dynamics


SummaryThere is a need for High-Rate Structural Health monitoring (HR-SHM), structural prognostics, and real-time decision making for both military and commercial applications.

Technical Objectives Technical Challenges/NeedsSensing Awareness Adequate SensingStructural Awareness System Knowledge UnderstandingEnvironment Awareness High Variability in LoadingEnergy Awareness Limited Resources for Algorithm ImplementationSystem Development Experimental Validation

Risk-based Decision Making High-Rate Uncertainty Quantification

During the Virtual IMAC XXXIX, join the panel discussion on “High-Rate Structural Health Monitoring and Prognostics”

HR-SHM should target 1 ms timescales from event detection to decision-making (current goal)

Summary of Technical Objectives and Needs are:


High-rate Structural Monitoring, Damage Detection, Prognostics, and Reactions Working Group

Novel Variable Input Observer for High-Rate State EstimationPI: Dr. Simon Laflamme, Iowa State Univ.

Nonlinear Force Identification and Localization for External ForcesPI: Dr. Peter Avitabile, Univ. of Massachusetts at Lowell

Real-time Impact Load Identification for Nonlinear Dynamical SystemsPI: Dr. Yang Wang, Georgia Institute of Technology

Dr. Alain Beliveau Dr. Adriane MouraMr. James Scheppegrell

Prognosis of Damage Using Uncertainty-Quantified Failure Forecast MethodPI: Dr. Michael Todd, Univ. of California, San Diego

Real-Time State Monitoring for Air Force Structures PI: Dr. Austin Downey South Carolina University.

Multiscale SHM using Data-Driven MethodsPI: Dr. Zhu Mao, Univ. of Massachusetts at Lowell.

http://www.me.sc.edu/Research/Downey/high_rate_working_group.html

http://www.me.sc.edu/Research/Downey/high_rate_working_group.html

Distribution A. Approved for public release; distribution unlimited. (96TW-2021-0019) . 9


Research Opportunities at AFRL/RWAFRL ScholarUndergraduate/Graduate Students• Summer Internship Program• 8-10 weekshttps://afrlscholars.usra.edu/students

SMART Scholarship for ServiceUndergraduate/Graduate Students

• DoD sponsored scholarship (1-5 years)

• Summer Internships at Gov. Research facility

• Employment Obligation afterward

https://www.smartscholarship.org/smart

AF S&T Fellowship Post-DocRecently finished Ph.D.• Work onsite at DoD Research Labs w/ government

advisor• 1-2 YearsStructural Dynamics and Instrumentation of Electronic Systemshttp://nrc58.nas.edu/RAPLab10/Opportunity/Opportunity.aspx?LabCode=13&ROPCD=134502&RONum=C0147

Summer Faculty Fellowship ProgramProfessors• AFRL/AFOSR Sponsored• Work with hosting research lab • On site for 8-10 weekshttps://afsffp.sysplus.com/

https://afrlscholars.usra.edu/students

https://www.smartscholarship.org/smart

http://nrc58.nas.edu/RAPLab10/Opportunity/Opportunity.aspx?LabCode=13&ROPCD=134502&RONum=C0147

https://afsffp.sysplus.com/

high-rate structural health monitoring and prognostics: an

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