Supplementary Restraint and Air-bag system

auxiliary Restraint and Air-bag systemSupplementary restraint and airbag system is a passive part of fomite guard system. SRS is designed to protect and lower forces acting on the driver and passenger at the event of the misfortune. In a solecism of an accident at urge on about 35km/h the SRS is emotional and the following procedure is winning place spot crash tensi angiotensin-converting enzymers atomic bite 18 activated -about 10-15 msairbags argon inflated -about 10-40 msairbags ar deflated -40-long hundred ms driver or passengers kinetic cleverness is taken in by airbagsaround 120 ms after accident the airbags are deflatedSRS and air-bag system populate of driver and passenger airbags (including igniter and pyrotechnic inflator)a prototype decipherable ( international mile)seat tap pretensionersimpact sensors (crash sensors)electronic control unit.Illustration 1. SRSDriver and passenger airbagThe airbag is made of one detail coated nylon and has a get of a bi g cushion. To allow rapid deflation air bag has side holes. Airbag is placed into counseling wheel (driver) and front of passenger side scarce also is placed on the both sides inside of the car as a curtain (protecting against side impact). In the redbrick car the number of airbags and their sizes are constantly changing, but principals are the same.In a case of an accident ECU engage igniter which triggers the spark necessary to burn render tablets (pyrotechnic inflator). The burned fuel tablets produce a nitrogen gas which inflates the airbag. Everything happens in few ms and the amount of gas and pressure created during burning is rigorously calculated for from each one airbag.Illustration 2. AirbagWarning get ( mile)A warning light is used as a part of the self-diagnostic system. Every meter when the ignition is switched on SRS checks all components of the system and if each fault appeared the MIL is activated. MIL light stays on as long as the problem of the system is n ot rectified.Illustration 3. MIL Warning LightSeat belt tensionersThe function of the seat belts is to secure occupant of the vehicle from injuries at an accident or a sudden stop. Due to a seat belt slack, belt stretch, three point seat belt protection is limited up to 40 km/h, if speed is high than this limit the occupants head or body can impact the steering wheel or the instrument panel.Seat belt pretensioners improve restraining world power of the seat belt and increase the protection of the occupant from injuries. In modern cars there are two types of tensioners, both of them can work simultaneously. The offset printing type is a shoulder pretensioner. The pretensioner pulls the seat belt tighter and holds the occupant well to the seats backrest. This action prevents the body from excessive forward movement. The pretensioner is activated at around 10-15 ms, and by conjunction with an airbag (10-50ms fully deployed) they absorb kinetic energy acting on the body. When the su pplementary restraint system (SRS) detected an accident the pyrotechnic propellant charge placed in the tube tightener is activated and pressure is created. The rising pressure in tightener pushes the piston which is attached to the stain cable and pulls the seat belt tightly against the occupant.Illustration 4. Seat belt pretensionersIn addition to the shoulder belt tensioner a buckle tighteners are developed. The buckle tensioner improves the restraining and protection on the occupant and prevents the body from submarining.Impact sensors on that point are two types of impact sensors mechanical and electronic. The mechanical system is a bunch in tube mechanism which basically consists of a ball, tube, attraction (holding the ball in position) and electrical move with a switch. If an accident occurs the ball is dislodged from the magnet and starts to roll forward inside the tube closing the circuit switch. Then the signal is sent to ECU to take further action. Illustration 5. mec hanically skillful crash sensorAnother type is an accelerometer. This kind of sensor detects any changes in a speed of a car and there are a few types of them in use.One of them is a piezoelectric crystallization accelerometer which works on principals similar to the engine knock sensor, another one uses a spring. A drastic change in car speed (deceleration) will cause the seismic mass movement or a spring bend, either of which will then change the output from these sensors. main advantage of this type of sensor is that sensors dont have to be designed for each car separately, as all changes can be made by the software.Illustraton 6. Electronic crash sensorIllustration 7. Piezoelectric crash sensorElectronic central unit (ECU)Electronic central unit collects and abbreviation the data from sensors and according to them it takes further action. The ECU has following functionscrash sensing by crash sensors (acceleration sensors)prompt activation of airbags and seat belt tensioners a ccording to antithetical types of the impact in the vehicle longitudinal direction eg. rear-end, frontal, sidetriggering of the seat belt tensioners depending on the buckle status, firing only when buckle is fastenvoltage and energy accumulator if vehicle battery failsdiagnosis of external and internal system componentsMIL activationstorage of faulty commands and epoch of itwatchdog (WD) constant monitoring of the airbag units with regards to false activation in non-crash situation and corrected if needed. Since 2003 all ECU has three independent monitoring hardware watchdogs WD1, WD2 and WD3. each(prenominal) of them independently monitor the system and if all data collected by them is matching the system is triggering procedure according to situation.Diagnosis and repair desertMake VauxhallModel AstraYear 2008Reg. No NL08BYYVIN WOLOAHL0885070200After switching on the ignition the Airbag MIL appeared on the dashboard. To find out the faulty code I plugged in the Snap-on diag nostic tool. Codes B0012 (driver airbag open circuit set up 1) and B0013 (driver airbag open circuit Stage 2) appeared.My diagnosis there is no nexus between the airbag unit and the system.To rectify this fault I do as followbattery at sea for at least 10 mins take air bag from the steering wheeldiagnosis confirmed airbag was dis attached from the circuitTwo plugs were connected to the airbag according to the number placed on the airbagair bag was replaced on the steering wheelbattery was connectedFinally, to confirm my diagnosis I reconnected the Snap-on diagnostic tool and erased faulty codes. MIL went off and the codes disappeared from the system.