Strain-based collision monitoring for protection plates of vulnerable structures by means of elasto-resistive wires

This article presents a novel, simple, low-cost, and fast method for strain-based collision monitoring of plate-like mechanical structures using line-type strain sensors – particularly, elasto-resistive wires. These properties make the method valuable for application to vulnerable structures in automotive industry, where economic requirements are high. As case example the composite sandwich under-body protection plate of the battery box of an electric car is considered. The article shows that elasto-resistive wires provide balanced sensitivity along their longitudinal extent and can thus monitor larger areas than a conventional strain gauge with comparable sensitivity. The presented monitoring method for plate-like structures requires at least three wires attached on the surface. Determined transfer functions relate the measurement signal with the location and magnitude of the quasi-static assumed collision load. Position, geometric extension, and orientation of the wires are optimized. Coordinates and magnitude of unknown collision loads are determined by minimizing the error between the evaluation database (represented by predetermined transfer functions) and the strain measurement values. The proposed strain-based collision monitoring method is verified and validated by both, numerically simulated and experimentally measured data. The results show that the method can be efficiently realized by determining the required transfer functions with finite element models.