Modal and Experimental Analysis of Satellites used for Side-Airbag System

Satellites are important mechanical components for the airbag system that connects the external environment to the Electronic Central Unit (ECU). They can contain two types of sensors: a piezoresistive or capacitive type sensor, which response to instantaneous variations in the acceleration due to an accident, called G satellites, or a sensor that responds to pressure variations after the side accident, called P satellites. The signals given by these sensors are sent to the ECU where they are evaluated and a decision is made whether their value exceeds a critical limit. The signals of the capacitive accelerometer are proportional to the variation of the capacitance of a capacitor consisting of several parallel elements. The micromechanical system thus formed has a natural frequency. For the correct transmission of the signal, the satellite must be mounted on a rigid part of the vehicle through a rigid bushing. At the same time, the resonance reached by the sensitive element of the accelerometer should be avoided. For these reasons in the paper, the satellite modeling is performed applying the Finite Element Method (FEM) followed by the analysis of dynamic behavior using Modal Analysis (MA). The satellite is designed in the Solid Works graphics environment. The numerical formulation from the ANSYS 13 software, was used to determine the modal shapes and natural frequencies corresponding to the satellite, including the Lanczos block method. For this purpose, boundary conditions are imposed, blocking the movements of the satellite to the fixing bush on the car. Experimentally, natural frequencies are determined by measuring vibrations using a Doppler Laser Velocimeter (DL V). The experimental results obtained in the paper validate the results obtained by MA.