PID creation Non-Linear

[Naf]

Ok, i am so lost here...

I have an AEM wideband twin channel, i followed the non-linear instructins, and its still not working right...I had a very accurate equation, but the AFR wouldnt pass 9A/F although i was actually at 15A/F

Here is a copy of my PID CALC

*UNITS

#Code System Abbr Description
#-------- ---------- -------- -------------------------------------------------------------
A/F AEM 1 None AFR "Air Fuel Ratio"
B/F AEM 2 None AFR "Air Fuel Ratio"

# ================================================== ============================
# Add slot definitions here
# --------------------------------
# See sae_generic.txt for more information on "SLOT" formats
#
#Units Low High Fmt Expression
#------------ ------------- ------------- ---- --------------------------------------------------------------
*CLC-00-001
A/F 8.41 19.44 .1 "(0.0129*{EXT.AD1}*{EXT.AD1})-(0.0362*{EXT.AD1})+9.5366"
*CLC-00-002
A/F 8.41 19.44 .1 "(0.0129*{EXT.AD2}*{EXT.AD2})-(0.0362*{EXT.AD2})+9.5366"
# ================================================== ============================
*PRN - Parameter Reference Numbers
# --------------------------------
# See sae_generic.txt for more information on the *PRN section
#
#Code PRN SLOT Units System Description
#------------------------- ---- ------------ ---------------- ---------------- ------------------------------------------
CALC.AEM_AFR1 F002 CLC-00-001 "AFR,V" O2-Wide "AEM Wideband"
CALC.AEM_AFR2 F002 CLC-00-002 "AFR,V" O2-Wide "AEM Wideband 2"

Please help...I need to get the widebands to work so i may finish off my tuning...

Thank you all for you time

Manaf

[joecar]

So your equation is: AFR = 0.0129*V^2 - 0.0362*V + 9.5366

This gives:
V=0 --> AFR=9.5366
V=5 --> AFR=9.6781

Your equation is incorrect...

[Naf]

This is the equation that Excel gave me...

i have even a 3 order polynominal and 4 order...

What other means do i have to get the proper equation

[joecar]

Naf,

Welcome to the forum...

What are your sample data points...?
What are your 3rd/4th order polynomials...?

Cheers
Joe

[Alvin]

This is the equation that Excel gave me...

i have even a 3 order polynominal and 4 order...

What other means do i have to get the proper equation

You'd probally be better setting it up as a piecewise

[redhardsupra]

yea, just give us the data and we'll give you an equation, i've done this for the zeitronix's wb nonlinear output over 2yrs ago, it's not hard

[Naf]

Thanx so much

The points are as follows

Volts AFR Gas 0-5V
0.000 8.41
0.156 8.52
0.312 8.64
0.468 8.81
0.624 8.98
0.780 9.09
0.936 9.26
1.092 9.44
1.248 9.61
1.404 9.78
1.560 9.95
1.716 10.12
1.872 10.29
2.028 10.47
2.184 10.69
2.340 10.92
2.496 11.15
2.652 11.38
2.808 11.67
2.964 11.95
3.120 12.24
3.276 12.58
3.432 12.92
3.588 13.27
3.744 13.67
3.900 14.13
4.056 14.64
4.212 15.21
4.368 15.84
4.524 16.53
4.680 17.27
4.836 18.19
4.992 19.44

[Blacky]

Or you can set up a lookup function in a calculated PID.

lookup()

Syntax:

• lookup(x,a1,a2,b1,b2,…,c1,c2)

Arguments:

• x: a numeric expression
• a1,a2,b1,b2,...,c1,c2 is a list of pairs of values.

Return value:

• The value of the second value of the pair whose first value is less than or equal to x. The list of value pairs must be sorted on the first value of each pair.

So in your case:

Lookup({EXT.AD1},0.000,8.41,0.156,8.520.312,8.64,0.468,8.81,0.624,8.98,0.780,9.09,0.936,9.26,1.092,9.44,1.248,9.61,1.404,9.78,1.560,9.95,1.716,10.12,1.872,10.29,2.028,10.47,2.184,10.69,2.340,10.92,2.496,11.15,2.652,11.38,2.808,11.67,2.964,11.95,3.120,12.24,3.276,12.58,3.432,12.92,3.588,13.27,3.744,13.67,3.900,14.13,4.056,14.64,4.212,15.21,4.368,15.84,4.524,16.53,4.680,17.27,4.836,18.19,4.992,19.44)

EFILive will interpolate between data points.

Regards
Paul

[redhardsupra]

y = 0.1153x^3 - 0.4494x^2 + 1.5386x + 8.2255 seems to work with R^2=0.9986 so it's very close for the data given

[Naf]

I got the y= part, but where does the R^2=0.9986 come in?