[Diy_efi] Traction Control System (update 2)

[les]

How about this idea:

After conditioning the wheel sensors to a good square wave,
use counter with two inputs, count up and count down.
Have the front wheel be triggering count down, and the back
wheel count up. With no slip, the counter will bounce around
pretty much even, but as slip starts, the count will be going up.
No need to measure pulse frequency, just a count, after a reset.

Just an idea.

-Les



> -----Original Message-----
> From: diy_efi-admin at diy-efi.org=20
> [mailto:diy_efi-admin at diy-efi.org] On Behalf Of Nic van der Walt
> Sent: Monday, April 29, 2002 11:03 AM
> To: Diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Traction Control System (update 2)
>=20
>=20
> >A MCU with an internal AD converter could then read the=20
> analog voltage
> from
> >the four 2907's.
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> >In this case I would use ....
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> The 2907 is designed for cruise control etc... Where you have=20
> an high frequency to convert.
>=20
> For the very low frequencies you see when doing traction=20
> control it won't work. The wheels will have started spinning=20
> seriously by the time the output rises to the point where the=20
> an 8 bit ADC will start giving you a reading.
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> The signals from the four wheels will also differ=20
> significantly. Just the storage caps on the different 2907's=20
> will introduce a typical -10% to +20% tolerance. Sure you=20
> *could* tune it out, but how often do you want to fiddle with it?
>=20
> Using 2907's will allow the wheel to break loose and start=20
> spinning before the controller reacts. Then you reduce torque=20
> somehow, and the wheel needs to shed momentum before gripping=20
> again. Your control loop has a huge delay and osscilates=20
> easily. It will work somewhat, but you'll be ripping the=20
> drivetrain apart until you have a well tuned PID. Then the=20
> temperature changes or the caps age and you start over.
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> If you use the sensor properly, by doing a per tooth wheel=20
> speed calculation, you detect the start of wheel spin before=20
> it has started smoking rubber. If you then back of torque=20
> slightly you can conceivably keep the wheel right at the=20
> traction limit, instead of swinging wildly around it.
>=20
> N.
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>=20
>=20
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>=20


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