Last year, quite a number of our articles were in relation to brakes. It is important to understand the workings of the brakes if we are to reduce on accidents. In over 50% of fatalities, brake failure is cited. Most modern cars are fitted with ABS (Anti-lock Braking System) as a safety improvement. However, most of us that have been driving for several years started with the old system where wheel lock under braking was a common scene. Then roads could be seen with black lines called skid marks. Depending on the adjustments of the brakes, the most well adjusted wheel would be the best braking wheel, and this used to cause vehicles to swerve towards the side that was locking the wheel. Traffic police could even measure the length of the skid marks at an accident scene to estimate the speed at which you were travelling before the accident occurred.
ABS has evolved considerably. Versions of ABS coming on cars now not only prevent wheel lock under braking, but also electronically the front to rear brake bias. In simple speak, the nodding we used to experience and forward movement under sudden braking is not as noticeable now as it was then. This function in the ABS is referred to as the Electronic Brake force Distribution, traction control system, or electronic stability control depending on specific capability and implementation.
Most drivers who are used to the brake type that was locking the wheels now are saying that vehicles nowadays have poor braking. While ABS offers improved vehicle control, and may decrease stopping distances on dry and especially slippery surfaces, it can also increase braking distance on loose surfaces especially gravel. Anyone used to driving on gravel may experience poor braking effect with ABS. A rotating wheel allows the driver to maintain steering control under heavy braking by preventing a skid and allowing the wheel to interact with the road in relation to the steering input.ABS is typically composed of a central electronic control unit (ECU), wheel speed sensors, and hydraulic valves within the brake system. The ECU will constantly monitor the rotational speed of each wheel and when it detects a wheel moving slower than the others a condition indicating an impending wheel lock it will actuate the valve to reduce on hydraulic pressure to the brake that is affected, thus increasing on the speed at the affected wheel. The wheel then turns faster. When the ECU detects that the wheel is turning significantly faster, hydraulic pressure is increased, so braking force is reapplied and the wheel slows.
This process is repeated continuously and can be detected by the driver via brake pedal pulsations. A typical anti-lock system can apply and release pressure up to 20 times a second. The ECU disregards rotative speed below a certain threshold because when a car is moving, the two wheels towards the centre of the curve turn slower than the outer two. It is for this reason that a differential is used in road going vehicles..
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