> ABS turns the brakes off if you brake too hard, traction control turns the 
> drive off if you accelerate too hard. At least, as far as I know... ;-)

Newer cars can apply the brakes too programmably, it's much faster than 
cutting the fuel and more accuracte, and when you are about to skid out 
sideways on a slippery road fast reactions are what you need.

> Well... less suseptable to EMI and corrosion?

Yeh the EMI issue is probably the biggest reason, especially now that they 
seem to be wanting to put more stuff in the back of the car to keep the 
weight distribution 50/50, it means you have long wires which are always bad 
from an EMI point of view.

> Seriously though, you'd think they'd just put lots of spare cable in there 
> so you can add new connections without rearranging half the car...

Guess it's cheaper not to, and then charge more for people who want to do 
stuff afterwards.

> Oh, it's programmable? I thought it was a purely mechanical system...

Older cars it was mechanical, yes, programmable (once!) by the positioning 
of the hydraulic valves :-)  Newer cars it's all electronic controlling a 
motor in software.

> Even so, how can you "sense" the amount of force the user it putting into 
> the system seperately from the amount of force the power assist is putting 
> into it? I can't think of a way of doing that.

Measure how much the steering column is twisted (ie rotation at one end 
minus rotation at the other end) between the steering wheel and where it 
connects to the rack/motor/hydraulics.  This will be directly proportional 
to the torque the driver is applying to the wheel, no matter what the motor 
or the wheels are doing.

In mechanical systems, this twist would cause hydraulic valves to open and 
assist the rack moving, in electronic systems there is probably just a 
strain gauge on the steering column that goes through an ATD to the 
software.

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