Multi-point PID calibration

Developers
21

Timofey Titavets писал(а) 2026-04-01 03:19:

Someone mentioned you in a post.

| nefelim4ag
April 1 |

  • | - |

@minicx, sorry to bother
Can you give it a try?

github.com/Klipper3d/klipper

RFC: Pid calibration use First Order Plus Dead Time model for PID estimation (#7243)master ← nefelim4ag:pid-calibration-imc

opened 06:41PM - 28 Mar 26 UTC
nefelim4ag
+145 -23

TLDR: This is an attempt to make one PID calibrator to rule them all. The ba…

  1. PID_CALIBRATE .. MAX_POWER=1 - it should be sane
  2. Check how it is holding temperature, for example, 250 °C
  3. Remember the average power from 2
  4. PID_CALIBRATE .. MAX_POWER=<average power +5% or so> - ideal case for calibration, where we have many samples, it is asymptote & etc
  5. Same test, how does it go

Thanks,
-Timofey

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yea, sure!

1 Like
22

Sorry I’m late to this but I wonder why absolute temperature is not used in the calculation?

https://en.wikipedia.org/wiki/Charles%27s_law

23

Sorry, can you elaborate and explain how this is related?

As far as I understand, we have a PID value for temperature (regardless of Celsius or Kelvin)
And we transition from one value to another, depending on the target temperature.

In other words, regardless of adding or removing the 273.15 conversion value, the behaviour would be exactly the same.

-Timofey

1 Like
24

In Charles Law, wikipedia entry linked above, Volume of an ideal gas is linearly related to absolute temperature in Kelvin. I suspect that PID varying as a function of temperature is more likely to be linear using Kelvin rather than centigrade. I have not done actual PID calculations as a function of temperature but it would be consistent with how temperature impacts pressures and volumes.

25

PID tuning uses temperature DELTA from setpoint.

in that context °C = °K

A comprehensive model would care about ambient temp and airflow etc. All the external factors are assumed to be constant when PID tuning.

P (proportional) is delta T
I (integral) is (delta T)*t
D (derivative) dT/dt

2 Likes