>> I must admit, I've always wondered how the hell ABS actually works.
> 
> A speed sensor on each wheel, if one drops too quickly compared to the 
> others, or they all drop too quickly than what is "usually possible" a 
> solenoid is opened that releases the brake pressure until the wheels 
> speeds are back to normal, then the solenoid is closed.  The process 
> might then repeat if the driver is still pressing the brake pedal hard - 
> this is the "pulsing" sensation you feel.
> 
> Note that modern cars are much more complex, with ABS being part of a 
> much larger control system, capable of regulating the braking force to 
> each individual wheel (to allow each wheel to be giving the maximum 
> stopping power, and to prevent skids, wheel-spin etc).

...not to mention traction control... ;-)

>> But not as much as power steering. This, as far as I can tell, should 
>> be logically impossible. And yet it apparently works. How baffling!
> 
> There's a part in the steering system that twists or bends by a specific 
> amount depending on how hard you tug at the wheel.  A set of valves then 
> controls some pressurised hydraulics based on how much force you are 
> putting into the wheel, which helps you steer.
> 
> Newer cars have a torque transducer and an electric motor with some 
> clever software.  This saves on fuel as there is no hydraulic compressor 
> having to be run the whole time (usually you only need power assist at 
> low speeds).

The part I can't figure out is that, as far as I can tell, hooking up a 
motor that turns the steering wheel in the same direction as you're 
trying to turn it should generate a positive feedback loop. I can't 
figure out how turning the wheel doesn't cause the powerful motors to 
rip the wheel out of your hands and put the car into full lock before 
snapping the steering column in half...

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