1. Airbags

2. Supplementary Restraint System for driver and/or passenger safety in case of a crash. Basic Mechanism: A thin nylon bag in the steering wheel / above glove compartment inflates in the event of an impact and prevents the driver/passenger from hitting the steering wheel/dashboard. 3 Main Components: 1) Airbag module 2) Diagnostic Unit 3) Crash sensors What are Airbags?

3. Airbag Module Contains both inflator unit and light-weight fabric airbag and is located either inside: 1) Steering wheel hub 2) Above glove compartment 3) Near side compartment (as separate/combined head/side/window-curtain airbag) Airbag: Thin nylon fabric bag folded neatly into steering wheel that inflates to the size of a large beach ball on impact. Inflator unit: Contains a number of sodium azide pellets which are electrically ignited to produce N 2 that then fills the airbag. This is preferred to storing compressed gas in the unit (space, durability) Both airbag and inflator unit are for single deployment only – ie have to be replaced after a crash

4. Diagnostic Unit Enables inflator unit and sensors when vehicle is turned on, performs self check. Constantly monitors airbag readiness and indicates malfunctioning through an indicator on dashboard Usually stores electricity to activate airbag in the event that a crash damages the battery / link to battery Sensors Several crash sensors located in the front of vehicle and in the passenger compartment Each senses the sudden deceleration or impact in the event of a crash and flips a mechanical switch to indicate a crash.

5. Frontal crash scenario: Car crashes into an obstacle (wall) at 20+ mph Sensors detect the deceleration and inflator unit activated Deployment sensitivity: To guard against accidental inflation on hard braking, sensors detect collisions into a solid barrier at speeds greater than 8-14 mph only as impacts An electric current is used to heat a filament wire that ignites the NaN 3 capsules, producing N 2 : 2NaN 3  2Na + 3N 2 10Na + 2KNO 3  K 2 O + 5Na 2 O+ N 2 K 2 O + Na 2 O SiO 2  alkaline glass (safe, unignitable) 130 g of NaN 3 produces 67 ltrs of Na Airbag Deployment

6. The airbag then inflates fully at speeds > 320mph within 0.05s of crash. For maximum safety, occupant must have seat belt on and sit with chest 10” from steering wheel Immediately after full inflation, the airbag deflates through tiny pores on the surface within 0.3s Accelerometer

7. An on/off switch Combination with seat-belt pre-tensioners and other safety systems Inflation in the event of fire (high temp.) to prevent explosion of solid compound Depowering and differential powering Small rapid deployment airbags for side impact at roof-rail or door or seat back. eg: 1) Beltline Head/Torso Side Airbag 2) Inflatable Tubular Structure Additional Features

8. Electromechanical Crash Sensors

9. Fluid pressure based weight sensors

10. Smart Restraint System Is one that adapts its geometry, performance or behavior to suit varying impact types and/or occupants & occ. posns. Must be able to distinguish between: –RFIS & child seat –Child –Adult –Empty –Subsets of possible seating posns. for above ( 10”) –Belted / non-belted –Crash severity –Crash direction ie, a smart restraint system must be able to update itself on the following: –Occ. characterisation –Occ. location Accordingly decides: –Which airbags to deploy when –Full blown / supressed –Seat belt pre-tensioning, retraction/collapse of parts –Direction of deployment –Sequencing & Timing –Post deployment action

11. Smart Restraints Detection types: –mechanical –spatial –other Means of detection: –Weight & distribution (3) –Seat belt (webbing, rotation ctr & buckle) –Active Infra-red (OOP sense) –Ultrasonic –Radar/Microwave –Capacitive –tags for RFIS & smart keys –Height sensors in seat / belt Advance meth. (complex, high computing power reqd.) –Passive Infra-red –Video systems –Biometric sensing Systems must: –Sequence & time appropriately –Extremely reliable –Work within varying auto interior atmosphere and lighting –Differentiate camouflage –Low cost

12. Smart Restraints Components –Side/Variable/dual-stage airbags –Seat-belt pre-tensioners –Side/Central/Satellite/Safing crash sensors –Occupant sensors –Central ECU –Pre-crash sensors Driving states: –Normal –Collision avoidable –Collision imminent –Post-crash Sensor types: –Electromechanical –Accelerometers –Pressure –Stress-wave –Pre-crash Pre-crash sensing –More details reqd from sensors –Advantage: Enables early decision and pre-tensioning –Disadv: imprecise object classification & cost –Same sensors as those for ACC, CW/CA