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Research Papers

Efficient Identification of Naval High-Speed Craft Shock Mitigation Seat Modal Parameters From Drop-Test Data

[+] Author and Article Information
Zuneid Alam

FCA Canada Inc.,
Brampton, ON L6S 5R7, Canada
e-mail: zuneid.alam@fcagroup.com

Fred Afagh

Professor
Mechanical and Aerospace
Engineering Department,
Carleton University,
Ottawa, ON K1S 5B6, Canada
e-mail: Fred.Afagh@carleton.ca

Robert Langlois

Professor
Mechanical and Aerospace
Engineering Department,
Carleton University,
Ottawa, ON K1S 5B6, Canada
e-mail: Robert.Langlois@carleton.ca

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received February 6, 2015; final manuscript received October 13, 2016; published online January 23, 2017. Assoc. Editor: Hashem Ashrafiuon.

J. Dyn. Sys., Meas., Control 139(3), 031009 (Jan 23, 2017) (10 pages) Paper No: DS-15-1060; doi: 10.1115/1.4035018 History: Received February 06, 2015; Revised October 13, 2016

Naval high-speed craft (HSC) operating in moderate to high seas experiences high-g and repeated shock loading at the seat–deck interface. These conditions are known to pose a serious potential for injury to the occupants. While various shock-mitigating seats are commercially available; their designs are in many cases quite different, and quantifying their shock attenuation characteristics can be challenging. The need for a standard test platform and experimental analysis methodology to investigate HSC seat effectiveness is a major objective of research being conducted by Carleton University's Applied Dynamics Laboratory (ADL) in partnership with Defence Research and Development Canada-Atlantic (DRDC Atlantic). A drop tower was designed and manufactured for testing HSC seats in order to characterize their shock-mitigating effectiveness by simulating the severe conditions of a slam impact at sea. Further, in order to identify seat dynamic parameters from drop-test data, the eigensystem realization algorithm (ERA), a modal-analysis-based system identification method, was applied to efficiently extract the modal parameters. The technique was shown to successfully extract the damping ratio as well as the damped and undamped natural frequencies of the seats from impact test data. The evaluated dynamic properties of the seats can subsequently inform decisions related to the design and/or procurement of commercially available seats.

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Figures

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Fig. 1

Carleton University drop tower

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Fig. 2

Acceleration signals acquisition: acceleration signals

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Fig. 3

A set of photos showing (a) accelerometer on dummy mass located above the seat-pan, (b) accelerometer on underside of the seat-pan, (c) accelerometer on underside of the carriage, and (d) labview DAQ

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Fig. 4

Two DOFs model of the suspension seat

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Fig. 5

Sample absolute acceleration profiles

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Fig. 6

Sample relative displacement profiles

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Fig. 9

A set of plots showing stabilization diagram, and mode singular values to determine the dominant resonant mode of the seat's shock absorber

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Fig. 10

Acceleration versus displacement plot for a 0.15 m drop of the tested seat showing nonlinear behavior

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Fig. 11

Analytical and measured responses of the seat-pan for a 0.45 m drop

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