Performance analysis of a bumper-pedestrian contact sensor system by using finite element models

A pedestrian contact sensor in the car bumper is a potential solution to trigger an active hood system. Because of the high level of temperature dependency for the bumper foam stiffness, the sensor output can be unstable at varying temperatures. A new contact sensor was, therefore, developed to provide a temperature-independent measurement for pedestrian impacts. This study analysed the performance of the bumper-pedestrian contact sensor system. First, a baseline finite element (FE) bumper model of a production car was developed and validated. On the basis of the baseline model, an improved bumper model was subsequently developed to meet the requirements of the lower leg form impact tests proposed by Working Group 17 of the European Enhanced Vehicle-safety Committee. Second, an FE human lower extremity model was developed. Using this model, the baseline and improved bumper models were further evaluated in terms of the predicted knee ligament raptures and long bone fractures. Finally, the new contact sensor was built into the improved bumper model. A performance study was then conducted to evaluate the sensor effectiveness. Consequently, a better diameter for the sensor tube was identified in terms of the temperature stability and mass sensitivity of the sensor output.