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Proceedings Paper

Shape memory alloy resetable spring lift for pedestrian protection
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Paper Abstract

Pedestrian protection has become an increasingly important aspect of automotive safety with new regulations taking effect around the world. Because it is increasingly difficult to meet these new regulations with traditional passive approaches, active lifts are being explored that increase the "crush zone" between the hood and rigid under-hood components as a means of mitigating the consequences of an impact with a non-occupant. Active lifts, however, are technically challenging because of the simultaneously high forces, stroke and quick timing resulting in most of the current devices being single use. This paper introduces the SMArt (Shape Memory Alloy ReseTable) Spring Lift, an automatically resetable and fully reusable device, which couples conventional standard compression springs to store the energy required for a hood lift, with Shape Memory Alloys actuators to achieve both an ultra high speed release of the spring and automatic reset of the system for multiple uses. Each of the four SMArt Device subsystems, lift, release, lower and reset/dissipate, are individually described. Two identical complete prototypes were fabricated and mounted at the rear corners of the hood, incorporated within a full-scale vehicle testbed at the SMARTT (Smart Material Advanced Research and Technology Transfer) lab at University of Michigan. Full operational cycle testing of a stationary vehicle in a laboratory setting confirms the ultrafast latch release, controlled lift profile, gravity lower to reposition the hood, and spring recompression via the ratchet engine successfully rearming the device for repeat cycles. While this is only a laboratory demonstration and extensive testing and development would be required for transition to a fielded product, this study does indicate that the SMArt Lift has promise as an alternative approach to pedestrian protection.

Paper Details

Date Published: 19 March 2008
PDF: 13 pages
Proc. SPIE 6930, Industrial and Commercial Applications of Smart Structures Technologies 2008, 693005 (19 March 2008); doi: 10.1117/12.775994
Show Author Affiliations
Brian M. Barnes, Univ. of Michigan (United States)
Diann E. Brei, Univ. of Michigan (United States)
Jonathan E. Luntz, Univ. of Michigan (United States)
Kenneth Strom, General Motors R&D (United States)
Alan L. Browne, General Motors R&D (United States)
Nancy Johnson, General Motors R&D (United States)


Published in SPIE Proceedings Vol. 6930:
Industrial and Commercial Applications of Smart Structures Technologies 2008
L. Porter Davis; Benjamin Kyle Henderson; M. Brett McMickell, Editor(s)

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