1091130682_2004_Physics_Notes_Arum - ABS Brakes The idea of ABS brakes Anti locking braking system or ABS brakes are designed to prevent accidents not

1091130682_2004_Physics_Notes_Arum - ABS Brakes The idea of...

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ABS BrakesThe idea of ABS brakesAnti- locking braking system or ABS brakes are designed to prevent accidents not help you when your in an accident. The purpose of ABS, is to avoid crashes in the first place. ABS help do this by reducing the stopping distance of the car, ABS brakes will stop you faster than conventional brakes will. The name is pretty self explanatory ABS brakes stop the tyres from locking up- which is when cars begin to side on the road. By preventing the locking of the wheels you can over come the loss of traction which is quite dangerous in an accident because if you don’t have traction on the road you cannot steer your car. So with ABS brakes you can brake and turn at the same time which reduces the chances of a crash.Components of ABS brakes There are four main components to an ABS system: Speed sensors Pump Valves Controller Speed Sensors- The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information. Valves- 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 is passed right through to the brake. In position two, the valve blocksthe line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releasessome of the pressure from the brake. Pump- Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up. Controller- The controller is a computer in the car. It watches the speed sensors and controls the valves.
How ABS brakes workThe controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 97 km/h under ideal conditions, but a wheel that locks up could stop spinning in less than a second. The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tyre can actually significantly change speed. The result is that the tyre slows down at the same rate as the car, with the brakes keeping the tyres very near the point at which they willstart to lock up. This gives the system maximum braking power.

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