Super confused about this! Any explanation would be greatly appreciated.
In: Engineering
Simply put, each wheel’s rotation speed is measured separately. If a wheel begins to skid on the ground, the brakes on that wheel suddenly aren’t dealing with nearly as much weight any more and rather than stopping the car, they only stop the single wheel, and do so pretty suddenly. This sudden loss of speed is detected. Due to variance in vehicle weight distribution and stuff, not all tires lose grip at once so the difference will be very noticeable to a computer.
The response is simple: release brake pressure on that one wheel. Now what would be skidding starts to turn the wheel and it picks up speed again. Once it gets its grip again, the brakes can be applied again. Done just right, your wheels ride the edge of skidding and the driver can still steer while getting (almost) maximum stopping power out of the brakes simply by slamming the pedal.
Traction control is similar, catching more variations. If you apply too much gas in a slippery situation, you can also spin wheels again snow or ice, and that’s detected and countered. But don’t rely on it to save you. It can’t prevent all kinds of skidding and on very slippery surfaces like ice it can’t give you more grip than is available.
ABS has sensors in the wheels that detect if the tires are rotating.
If the sensor notices the wheel has stopped/locked but the car is still moving it will engage the ABS system.
These sensors can also be used to detect a flat tire. If you are moving at speed and one wheel is spinning faster than the one on the other side for a set period then it’s likely a flat.
These days though most cars have TPMS sensors instead for that.
Each wheel have an ABS sensor that measures the speed of the wheel. When one wheel suddenly slows down and not the others it reduces the pressure in the brake line for that wheel to avoid it locking up.
Traction control is indeed a further development from ABS. When ABS first came out it was made as more of a bolt on solution to existing car designs. So it would be a simple separate unit which only solved brake locking. That makes it a very important safety device. In order to do anti-skid you need more sensors for the throttle position and steering wheel. The ABS pump also needed to be double action, not only releasing pressure but also applying pressure. So this became a more advanced and more integrated system. It is also not considered a safety device as it is mostly used to allow for higher speed over slippery surfaces. The crashes it can prevent are quite rare compared to the crashes that ABS is preventing.
Sensors on all four wheels. If one of the wheels spins significantly slower than the others the system reduces the breaking pressure on that wheel.
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