Shape memory alloy (SMA) wire actuators are quickly becoming technologically ready for a wider range of
commercial applications due both to their exceptional actuation performance and to recent advances in the
manufacture of drawn SMA wire. Shape memory alloys are complex materials requiring a breadth and depth
of knowledge to successfully implement in more demanding industrial applications, knowledge to which most
engineers may not have been exposed. This paper proposes a modular design framework to aid engineers at
any level of expertise to synthesize and analyze SMA wire actuators. The modularity of the framework allows
for changes in design, architecture, and system topology and allows for easy adaptation to the rapid research
advances in the knowledge and understanding of the response and robust use of SMA. The layered structure of
the framework is detailed; differentiating the design tasks by function: modeling, evaluation, optimization, and
design guidance. Each layer is modular within itself, and in particular, the modeling layer allows for a variety of
views to suit the expertise of individual designers. A sample design tool built within the framework is presented
for the synthesis of actuators composed of multiple straight SMA wires acting against linear loads, accompanied
by a physical system demonstration. This example, while basic, demonstrates the general applicability and
flexibility of the framework for aiding many types of users in a large variety of SMA wire actuation design
problems.
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.
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