Recently I read an article about ABS brakes. In that, they repeated several times the term that traditional hydraulic brake replaced with ABS brakes. Why it so? The reason for choosing ABS is mentioned in that article. Is anybody knows about it?
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2 Answers
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The static friction coefficient of tires on dry road is approximately 0.7 up to 0.9 and on a wet road around 0.4. Remember as long as the tire is rolling even while the driver is pushing the brakes and the car is stopping with no slip this static coefficient applies and brings the car to a quick stop.
But if you kick hard on your brakes and they lock, the tire skids and the steering becomes uncontrollable and the traction drops to very low kinetic levels in the range of 0.05 depending on the tire and road condition.
ABS system controls the hydraulic brakes, stopping them just short of locking up and skidding, while permitting maximum brake force and maintaining control and steering.
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From my limited understanding, it can be understood as follow:
"Traditional" hydraulic brake: It is a simple mechanical system, the harder you slam or step on the brake pedal, the harder the brake clamp will stuck on the brake plate. It is a basic system, but it comes with a risk: In certain scenario, your wheel may be locked (ie stop rotating), but the moment of inertia of your car is too great, therefore, it keeps going forward. Needless to say, this is a "problem".
To solve the aforementioned problem, ABS (Anti-lock braking system) is built. For the ultra-simplified version (which is probably wrong), think the brake plate at the wheel is not constantly applying the maximum brake force, but using in a certain rhythm and/or progress.
The "end-effect" can be seen as follow
