PID Question

[mgouldstone]

Novice PID questions...

In my map I have a 'Proportional - Gain'' set to 0.4 for Fuel pressure control. The description of PID (F1) says 'Proportional - Gain'' = %/Kpa and my Kpa is set to an aim of 400. I have watched the videos and it shows a 'Proportional - Gain'' value of 0.5 in a lot of examples but a lot of other parts of my map has a 'Proportional - Gain'' of 1000+ which is then subsequently divided by 1000. My question is can the 0.4 value be correct as it seems so small and what value should I start with?

My other question is that I have 'Integral - Gain' set to 50 and 'Integral Min / Max' set to 0. The integral isn't doing anything am I correct it's because the min / max are both set to '0'.

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[David Ferguson]

The number are just numbers, the real question is how is your fuel pressure control?

What happens if you change the value of "Fuel Pressure Control Aim". Does the Fuel Pressure track that change, or does it oscillate (too much Proportional), too much overshoot/undershoot (too much Derivative), or never reach the target (not enough Integral).

I suggest making step changes of 10 psi and tuning the PID to get that to track.

[Stephen Dean]

As David said, they are just numbers, and one system may need to have large values in it, whilst another needs only very small values. This is why a PID system needs to be tuned to suit the device under control.

I have attached the PID tech-notes so that you can have a look at them, whilst this was done for the Mx00 series ECU's, the principles are the same for the M1 Series ECU's.

DTN0003_Introduction_to_PID_Control.pdf

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