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1. ABS System
An anti-lock braking system is an automobile safety system that allowsthe wheels on a motor vehicle to maintain tractive contact with the roadsurface according to driver inputs while braking, preventing the wheels fromlocking up (ceasing rotation) and avoiding uncontrolled skidding. It is anautomated system that uses the principles of threshold braking and cadencebraking which were practiced by skillful drivers with previous generationbraking systems. It does this at a much faster rate and with better controlthan many drivers could manage.
There are four main components of ABS: wheel speed sensors, valves, apump, and a controller.
A speed sensor is used to determine the acceleration or deceleration ofthe wheel. These sensors use a magnet and a Hall effect sensor, or a toothedwheel and an electromagnetic coil to generate a signal. The rotation of thewheel or differential induces a magnetic field around the sensor. Thefluctuations of this magnetic field generate a voltage in the sensor. Since thevoltage induced in the sensor is a result of the rotating wheel, this sensorcan become inaccurate at slow speeds. The slower rotation of the wheel cancause inaccurate fluctuations in the magnetic field and thus cause inaccuratereadings to the controller.
There is a valve in the brake line of each brake controlled by the ABS.On some systems, the valve has three positions:
In position one, the valve is open; pressure from the master cylinder ispassed right through to the brake.
In position two, the valve blocks the line, isolating that brake fromthe master cylinder. This prevents the pressure from rising further should thedriver push the brake pedal harder.
In position three, the valve releases some of the pressure from thebrake.
The majority of problems with the valve system occur due to cloggedvalves. When a valve is clogged it is unable to open, close, or changeposition. An inoperable valve will prevent the system from modulating thevalves and controlling pressure supplied to the brakes.
The pump in the ABS is used to restore the pressure to the hydraulicbrakes after the valves have released it. A signal from the controller willrelease the valve at the detection of wheel slip. After a valve release the pressuresupplied from the user, the pump is used to restore a desired amount ofpressure to the braking system. The controller will modulate the pumps statusin order to provide the desired amount of pressure and reduce slipping.
The controller is an ECU type unit in the car which receives informationfrom each individual wheel speed sensor, in turn if a wheel loses traction thesignal is sent to the controller, the controller will then limit the brakeforce (EBD) and activate the ABS modulator which actuates the braking valves onand off.
Wheel slip: In vehicle dynamics, slip is therelative motion between a tire and the road surface it is moving on. This slipcan be generated either by the tire's rotational speed being greater or lessthan the free-rolling speed (usually described as percent slip), or by thetire's plane of rotation being at an angle to its direction of motion.
The longitudinal slip is generally given as a percentage of thedifference between the surface speed of the wheel compared to the speed betweenaxis and road surface, as:
where ω is thelateral component of the rotational speed of the wheel, r is wheel radius at the point of contact and v is vehicle speed. A positive slip indicates that the wheels arespinning; negative slip indicates that they are skidding.
2. Ignition System
An ignition system generates a spark or heats an electrode to a hightemperature to ignite a fuel-air mixture in spark ignition internal combustionengines oil-fired and gas-fired boilers, rocket engines, etc.
Modern Electronic Ignition Modules: For the most part, there are 2 typesof ignition systems in use today (or variations of them): TCI (Inductionignition) or CDI (Capacitive Discharge Ignition). Both systems use a sensor totrigger a transistor switch (which has replaced the points).
Induction ignition: This is called an induction systembecause the coil is used as a power storage (an "inductor") devicefor the spark. Remember, the coil is powered up, stores near 30,000 volts, andunleashes it when the coil collapses (power supply cutoff). A feature ofinduction ignition is the slightly longer spark duration while the coilcollapses. This is an advantage when starting and for igniting lean/highcompression mixtures at high RPM. These type of systems require coils
meant for "induction" ignitions (they have a higher resistancetypically than CDI coils). Induction ignitions are simpler in design (cheaper)and used often on less sophisticated motors (lawn, motorcycle, etc...)
Capacitive Discharge Ignition: CDI ignition is most widely used today on automotiveand marine engines. A CDI module has "capacitor" storage of its ownand sends a short high voltage (about 250+ volts) pulse through the coil. Thecoil now acts more like a transformer (instead of a storage inductor) andmultiplies this voltage even higher. Modern CDI coils step up the voltage about100:1. So, a typical 250v
CDI module output is stepped up to over 25,000v output from the coil.The CDI output voltage of course can be higher. So you'll see CDI systemsclaiming coil output capability over 40,000- 60,000 volts!!? As you will seethis is not exactly what happens at the plug but for math purposes it worksout. The huge advantage of CDI is the higher coil output and "hotter"spark. The spark duration is much shorter (about 10-12 microseconds) andaccurate. This is better at high RPM but can be a problem for both startingand/or lean mixture/high compression situations. CDI systems can and do use"low" resistance coils.
Advantages of CDI:
i. Improved cooling and heat sinks;
ii. Epoxy-rubber encasing componentsso they can't get wet;
iii. Heavier duty components that canwithstand the heat, vibration, and "duty cycles".
An airbag is a type of vehicle safety device and is an occupantrestraint system. The airbag module is designed to inflate extremely rapidlythen quickly deflate during a collision or impact with a surface or a rapidsudden deceleration. It consists of the airbag cushion, a flexible fabric bag,inflation module and impact sensor. The purpose of the airbag is to provide theoccupants a soft cushioning and restraint during a crash event to prevent anyimpact or impact-caused injuries between the flailing occupant and the interiorof the vehicle.
During a crash event, the vehicle's crash sensor(s) provide crucialinformation to the airbag electronic controller unit (ECU), including collisiontype, angle and severity of impact. Using this information, the airbagelectronic controller unit's crash algorithm determines if the crash eventmeets the criteria for deployment and triggers various firing circuits todeploy one or more airbag modules within the vehicle. Working as a supplementalrestraint system to the vehicle's seat-belt systems, airbag module deploymentsare triggered through a pyrotechnic process that is designed to be used once.Newer side-impact airbag modules consist of compressed air cylinders that aretriggered in the event of a side impact vehicle impact.