Throttle-by-Wire

[Igor Dorrestijn]

> Never mind the control loop problems.  The FAILURE modes
> are so difficult to define, and the consequences are so scary,
> I wouldn't own any kind of vehicle using throttle-by-wire.
> The only way to come close to practical is with multiple
> redundant systems, and that is another whole science.
>
> Bruce (redundant phone systems) Roe

I don't like to be the negative "me too" sayer, but I too would suggest not
to try this yourself unless you know you RULE at implementing fail safe and
multiple redundant systems.
I have worked at Hitachi for a short while and played with the electronic
controlled throttles. I can assure you the problem doesn't lie in the
control algorithm. The code for the control algorithm was only 600 bytes,
the fail safe code was at least ten times bigger.

On the speed of ECT, time to setpoint is under 0.1s so you shouldn't notice
that. If the throttle seems very slow to close they might have patched some
decelleration enrichment problem this way.

Hitachi did make an ECT that had the complete control module in the pedal
assembly. I'm not sure what is was used in, maybe Ford trucks. That would
probably be the safest way to use one if you REALLY have to. (standard
disclaimers apply)
You should ask yourself though why you want one. Your reasons are not the
same as the OEMs.

I once had a mechanical throttle stick and it was very scary indeed. Turning
off the engine doesn't solve all your problems as that turns off the power
steering and brake boosting as well.

Igor

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