DIY Traction Control

[Brian Sidebotham]

Hi there all,

 I'm new so be gentle! I expect you've been asked it all before, but 
here goes anyway...

 I'm currently developing a traction control system for 2WD cars. I 
have gone on the basis that I need to know the rotational speed of 
each wheel, detect the rotational differences between the driven, 
and non-driven wheels, and vary engine output accordingly.. (Put 
simply anyway! ;) )

For the rotational speed, I've chosen to use ABS sensors. My car 
was never available with ABS, but it is possible to fit ABS from 
different cars to my car.

For modifying the engine speed, I was originally going to use a fly-
by-wire accelerator system, but for two reasons I have chosen to 
go a different route:

(a) complexity of design in the fly-by-wire system
(b) engine response is a bit slow, and may not be able to work 
effectively as a launch control system aswell.

So I have decided to modify the injector pulses. Effectively not 
injecting fuel for a predetermined  number of fires in a time window. 
I have worked a time window, which will mean I have a resolution of 
2% of the engine power. I feel this is more than adequate for my 
application.

It's not really a road-going car, although it is fully road legal, and 
will be used on the road quite a bit. I'm not concerned about the 
engine popping away, and a slightly rougher ride, rather than the 
smoothenss of traction control that I would recieve through the fly-
by-wire system.

So my questions are, am I heading in the right direction? I reckon 
an AVR will suit it, I have all the dev kit at work for the AVR's so 
theres no problem there. Are there any thoughts between the two 
systems, fly-by-wire, and injector suppression? 
advantages/disadvantages?

Should I be monitoring anything else? or anything I should be 
taking into account.

The algorythms for Traction Control, and Launch control will be 
different won't they? At the moment, the changes in the program for 
traction, or launch control seem very subtle, and not too well 
defined in my head, so any pointers on the alogorythms used 
would be really useful.

Sorry for the long post. For further information on my thinking, etc. 
See the Traction Control Project section of http://www.valvers.com

BTW, it's for an injection car, motronic 2.5 based ECU system, 
4cyl, Driven wheels have an Auto Torque Biasing LSD in the box, 
so theres no fear of single-wheel spinning holding things up. Can't 
think of anything else that's of use...

Thanks in Advance,
Brian Sidebotham.

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