RPM approximation-prediction
Chaxel Frederic (QUALITE)
chaxel at cran.u-nancy.fr
Mon Oct 7 08:40:51 GMT 1996
Hi DIY_EFI members.
I'm start to design and program an Injection-Ignition ECU for
a simple engine (30 cm^3 mono-cylinder) which is used
for the Eco-Marathon Shell :
a competition with the less fuel consommation objective
(1200 Km with one litre at Le Castelet in France)
I'm a beginner in Injection-Ignition ECU, and I have one
question by now :
I get some TOP signals from a captor. This information
is used to calculate the engine RPM and to calculate the
Ignition time (by the way of a table).
But of course I get the RPM at T time and used it for
ignition at T+DT time (1 engine round after).
Of course RPM is not the same at T+DT than at T (if the
RPM change, which is often the case).
So if I want to be exact I must approximate (predict) the RPM.
My solution is actually to use RPM(T-1) and RPM(T) to calculate
RPM(T+1) :
RPM(T+1)=RPM(T)-RPM(T-1)+RMP(T)=2*RMP(T)-RPM(T-1)
It's a simple linear approximation (and simple to program
in assembly language).
This give good results (much more better than using RPM(T+1)=
RPM(T))
Maybe somebody know a better solution (Kalman Filter
for instance, or ...) ?
Sorry for my dirty English !
(o o)
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+ CHAXEL Frederic Email : Chaxel at cran.u-nancy.fr +
+ CRAN/GGP +
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+ Research center Faculte des sciences +
+ for automatic control BP 239 +
+ of Nancy 54506 Vandoeuvre les Nancy +
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