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

Er yeh, that's what I meant by wheel-spin.  OOC I looked up the instructions 
for how a dealer fits the "USB Audio" upgrade to my car (I was just 
wondering if the cables were already there and I simply needed to fit a 
suitable plug - sadly not).  Anyway, it appears my car has a network of 
fibre optic cables o_O.  To fit the upgrade, apparently involves ripping out 
half the car, making some connection to a box of opto-electronics in the 
boot, then fitting a "USB hub" under the drivers seat and fitting the USB 
socket in the centre console, and of course fitting cables between all of 
them.  The 250 pound price tag doesn't sound so bad now!

> 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...

If you simply program the motor to apply the same torque you are applying 
with your hands to the wheel, then there is no feedback, it will just feel 
like it takes half the force to turn it.  Of course in reality it is more 
complex, the multiplier is probably dependant on speed, and maybe other 
factors like how sharp you are turning.  And maybe there is some limit the 
torque you apply needs to go above before the motor kicks in?

Something like:

If AppliedTorque > 10 Then
 MotorTorque = (AppliedTorque - 10) * CalculateAssistFactor( VehicleSpeed , 
SteerAngle )
Else
 MotorTorque = 0

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