----- Original Message -----
From: "Andy Meng" <AndyMeng@letu.edu>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Tuesday, October 19, 2004 7:06 AM
Subject: Re: [PIC] Traction Control / Wheelspeed sensing


> I like that idea. It could possibly be as simple as strain gauges on the
> diff mounts. It seems to me that the torque required to break the tires
free
> would be independent of speed.

Keep in mind weight transfer. Off the line, weight transfer to the rear
wheels will be greatest. As speed increases, weight transfer to the rear
wheels will lessen. Then there is chassis torque, the twisting of the
chassis and drive train.


On the other hand, I don't know that this
> would offer information much different from an accelerometer - the torque
is
> going to drop when the wheels start spinning since kinetic friction is
less
> than static friction. Once the wheels are broken free it's pretty easy to
> keep them spinning. An accelerometer would give similar data, a peak as
the
> tires were on the edge of traction (or in the optimal slip area), then
> falling off.
>
> One conclusion I have come to is that I should have posed this question a
> month ago.
>
> Andy
>
>
> > No, drive torque drops or becomes near constant instead of increasing
with
> > rpm. This causes the engine rpm to increase (fast). One can also measure
> > car acceleration vs. drive shaft torque using a horizontal
accelerometer.
> > Just measuring and limiting the drive shaft torque is probably
sufficient
> > as a first approach.
> >
> > Peter
>
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