Experimental Investigation of Active Adaptability of the SMArt (SMAReseTtable) Dual-Chamber Pneumatic Lift Device for PedestrianProtection

摘要

The rapid urbanization of the world has led to an increase in pedestrian involvement in automotive crashes,prompting some countries to establish pedestrian regulations. A promising approach to address pedestrian safety is theuse of active lift devices to raise the hood upon detection of a pedestrian impact, thereby increasing the crush distancebetween the hood and vehicle hard points (i.e. engine). Current systems are generally not reusable or resettable and lackextrinsic effect compensation. The dual chamber SMArt (SMA ReseTtable) lift system presented in this paper is a fullyautomatically resettable system utilizing a stored energy approach with a pneumatic cylinder and a two stage ultrafastshape memory alloy (SMA) actuated valve. This active lift possesses the unique functionality to tailor lift performanceand compensate for extrinsic effects such as changes in temperature, mass, and platform using cylinder pressure andexhaust valve opening timing profile as operating parameters. As a proof of concept, a dual chamber SMArt lift systemwas designed, fabricated, and installed in a vehicle hood bay testbed. Full cycle tests demonstrated the functions of lift,lower and reset within the proper timing. The effect of additional mass, was experimentally characterized and two in-situ device parameters, pressure and valve profile, were investigated as means to mitigate these extrinsic effects. Thisexperimental study indicates that the dual chamber SMArt lift device may be a feasible alternative for pedestrianprotection with automatic reset/reusability along with capability to adapt in-situ to maintain performance within a narrowtiming window by compensating for extrinsic effects.