Airbag Deployment Logic and Polyhedral Method for Simulations

Airbag Deployment Logic and Side-Impact sensing simulationInstructor: Presented by:Dr. Sridhar Lakshmanan Manu Prateek Pavuluri siddartha ragala sainath reddy narayanagari

ECE-533: ACTIVE AUTOMOTIVE SAFETY SYSTEMSOccupant SafetyHow to help people?Protecting people is the primal objective of occupant safety innovation.Depending on vehicle, safety aspects differ.Sensors in a versatile way.These days vehicles come with passive methods in addition to active methods.

AIRBAGSOccupant Restraint SystemInflates Rapidly during a collisionProvides energy absorbing surface between vehicles occupant and its mounting locationPresent in multiple positions and around the vehicleDeployed based upon the impact level

The inflation processAir bags inflate after an electric current from the air bag control module is sent to a detonator.This ignition starts a chemical reaction producing nitrogen gas which rapidly inflates the nylon fabric air bag. After full deployment, as the occupant impacts and compresses the air bag, the nitrogen gas is released through small vent holes. The holes are specifically sized and spaced to reduce the volume of the bag at different rates, depending on the type of vehicle. The gas is released along with dust particles from material used to lubricate the bagAirbag Deployment logic - previous

Deployment logic - new

The parametersDeployment systems generally use electronic sensors that continuously report a vehicles acceleration to an air bag control module. The modules utilize complex algorithms to make air bag deployment decisions based on one or more kinematic variables. Due to the proprietary nature of air bag deployment algorithms, the velocity, acceleration, or displacement thresholds for air bag deployment during a collision are not easily obtained.Instead, a range of impact velocity, deceleration, or displacement threshold values can be calculated (based on vehicle stiffness-to-weight ratios) and used to estimate when an air bag should or should not deploy in a collision.

Airbag SimulationsAn approach by considering the structural equations of motion for airbag fabric dynamicsEuler equations of fluid motion for fluid inside the airbag and a coupling algorithm that defines the dependence between two systems of equationsSimulation carried out using Finite Element analysis and volumetric geometry

Side-Impact sensing

Vehicle ModelVelocity correlations at the SDM (Sensing and Diagnostic Module) and SIS (Side Impact Sensors) locations of the original model were not conducted as it was specifically built to evaluate occupant and structural performances only.Intruding velocity at mid-section and B-pillar were correlated and were reasonably good.The intruding velocity at these locations has significant effects on occupant injury as since the impact is directly imposed on the occupant.Co-relation factor at 25 MPH

Side impact simulationsThe original vehicle model was built to evaluate occupant performance and structural integrity in a side impact and we modified it for side impact sensing simulations.The model was subject to various collisions such as 90 degree car-to-car collision at low speed, mid-range speed and high speed. Rear lateral pole, side pole and also car-to-car (150 degrees and 30 degrees) test results have been capturedSimulation parameters and output

FEA Model-Final vs Baseline

ConclusionThe modelling techniques for building a high fidelity side sensing vehicle FE model were presented to simulate a suite of side impact tests and corresponding results.With the development of such modelling capability, calibration can be conducted much earlier than the integration phase.Also, deployment of side impact sensors as indicated in the Finite Element model can be very useful and can bring down the fatality and injury rate corresponding from side-impact vehicle accidents by many folds.

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