TRW develops multi-axis sensors for better crash safety

October 27, 2011 // By Christoph Hammerschmidt
Engineers from automotive supplier TRW Holdings have launched a new approach to improve crash sensing performance — they are developing remote acceleration sensors (RAS) which detect impacts from more than one direction simultaneously.

Traditional accelerometers used in crash sensing measure acceleration data in one dimension, either longitudinal acceleration (X axis) for front impact detection or lateral acceleration (Y-axis) for side impact detection. Multi-axis sensors add additional single axis sensors in the same housing or use multi-axis sensors to measure acceleration in more than one dimension simultaneously. 

This can significantly improve crash sensing performance in newly required FMVSS214 regulatory oblique side pole impact, and upcoming/proposed NCAP and IIHS rating tests such as the front small overlap impacts and front pole impact. Dual-axis sensors mounted in the B-Pillar can potentially offer this enhanced sensing capability without the necessity of additional pressure or acceleration satellite sensor in the door cavities for FMVSS214, and for the upcoming/proposed front small overlap impacts.

“Some frontal accident scenarios - such as pole impacts near the center of the vehicle - do not result in sufficient X-axis deceleration for traditional chassis-rail-mounted RAS single-axis sensors to detect the impact due to the relative lack of rigidity in this area of the vehicle,” said Martin Thoone, vice president, Global Electronics Engineering. “Front dual-axis RAS with Y-axis sensing can detect the lateral deformation of the vehicle sheet-metal around the pole and more quickly sense that an impact has taken place.” In addition, front dual-axis RAS may also offer enhanced sensing capability to deploy side curtain-bags in front oblique and offset deformable barrier impacts; resulting in improved occupant protection.

Another potential application for B-Pillar dual-axis RAS sensors is for frontal crash detection in Europe, where front crash sensors are not compulsory to meet the regulation. Depending on the design of the vehicle front crash structure, in some cases longitudinal acceleration sensors in the airbag control unit are sufficient to meet the regulation requirements. However some vehicles require a higher level of sensing performance and may need dedicated front crash sensors and associated wiring to meet the regulation requirements, adding significant cost and weight. Dual-axis side-impact sensors mounted