[Diy_efi] Traction Control System (update 2)

[Nic van der Walt]

>A MCU with an internal AD converter could then read the analog voltage
from
>the four 2907's.

>In this case I would use ....

The 2907 is designed for cruise control etc... Where you have an high
frequency to
convert.

For the very low frequencies you see when doing traction control it
won't work. The
wheels will have started spinning seriously by the time the output rises
to the point where
the an 8 bit ADC will start giving you a reading.

The signals from the four wheels will also differ significantly. Just
the storage caps
on the different 2907's will introduce a typical -10% to +20% tolerance.
Sure you *could*
tune it out, but how often do you want to fiddle with it?

Using 2907's will allow the wheel to break loose and start spinning
before the controller
reacts. Then you reduce torque somehow, and the wheel needs to shed
momentum before gripping again.
Your control loop has a huge delay and osscilates easily. It will work
somewhat, but you'll be ripping
the drivetrain apart until you have a well tuned PID. Then the
temperature changes or the caps age and you
start over.

If you use the sensor properly, by doing a per tooth wheel speed
calculation, you detect the start
of wheel spin before it has started smoking rubber. If you then back of
torque slightly you can
conceivably keep the wheel right at the traction limit, instead of
swinging wildly around it.

N.



_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi