SAR-EMT40 said:
Not really comparing apples to apples here Doug. Those cars are typically 5 to 10 years ahead of what the industry is providing us.
I think you missed my point. My point was that some ABS systems can outperform some of the best drivers in the world some of the time.
In situations where the traction is predictable, it is not particularly hard for a skilled driver to out-brake an ABS system. Maximum wheel traction occurs with some wheel slippage (5-10% IIRC). (Consumer ABS systems sense the start of the slippage as the cue for pulsing the brakes.) A skilled human can detect and brake in this small-amount-of-slippage zone, current consumer ABS pulse the brakes for a more reliable but less than maximum amount of braking.
In situations where the traction is unpredictable or changing rapidly, I expect that an ABS system could outperform many (or most) humans because it has a faster reaction time and directly detects what is happening with the wheels rather than seeing a different-looking patch of road and trying to guess how hard to brake. A human reaction time can easily be 1/2 second or longer and a car can easily travel 50 or more feet (at highway speeds) in this time.
The brakes are the start of the mechanical system that also involves the shifting of the CG of the car that makes the car slide or not slide.
I think your physics is a bit off here. Hitting the brakes does not change the CG of the car. It changes the applied forces. It adds drag (retarding forces) at the contact points of the wheels with the road. Since these contact points are below the CG of the car the forces are equivalent to a drag at the CG and a rotational force pushing the front downward which rocks the car body forward and places more weight on the front wheels and less on the back. (Increased (decreased) weight on the contact point increases (decreases) the available friction.) If the horizontal force at the contact points of any of the wheels is greater than the available friction, the wheel slides and the car skids.
This sets up the attitude of the car. The only reason for a skid on any surface is panic. Learning to lift your foot off of the brake when you desperately want to stop because you perceive an immediate emergency is a learned skill. It is not normal.
Retraining your brain to lift your foot off of the brake and re-apply it not hard enough to skid again and try to steer around is the skill that needs to be practiced.
I use a different logic chain, which I think works better for me. If I need to stop or slow down, I hit the brakes, and of course, with practice one learns how approximately hard one needs to brake. If I feel the car begin to skid, then I lighten the brakes to control the skid. My goal is to be able to apply the maximum brake force before skidding rather than taking my foot off the brake before any skidding occurs.
Doug
