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M307: bad model parameters with Beta3.2 LPC

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  • undefined
    MarMed
    last edited by Phaedrux 19 Nov 2020, 16:44

    With beta3.2 I am getting the following error from setting the model parameters for my chamber heater

    M307 H2 B1 A29.9 C1151.3 D55
    Error: M307: bad model parameters
    

    on previous versions the parameters would set correctly.

    11/19/2020, 11:37:31 AM	M307 H2
    Heater 2 model: gain 29.9, time constant 1151.3, dead time 55.0, max PWM 1.00, calibration voltage 0.0, mode bang-bang
    11/19/2020, 11:37:28 AM	M307 H2 B1 A29.9 C1151.3 D55
    

    just to note, the parameters used is from previous RRF3.2 betas, but with the bad curve error, due to dead time being negative I used the recommendation here to measure and set the dead time manually.

    Additionally I receive a bad curve fit using the new tuning algorithm, is there a similar workaround using the new tuning?

    RRF3.2 Beta3.2 on LPC

    Thanks

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    • undefined
      Veti
      last edited by 19 Nov 2020, 18:20

      thin post needs to be moved to the lpc sub forum

      1 Reply Last reply Reply Quote 0
      • undefined
        dc42 administrators
        last edited by dc42 19 Nov 2020, 21:09

        @MarMed, when you ran heater tuning under 3.2beta3.2, what parameters did it report when it gave the bad curve fit message?

        The gain of your heater looks very low and the dead time very high.

        Duet WiFi hardware designer and firmware engineer
        Please do not ask me for Duet support via PM or email, use the forum
        http://www.escher3d.com, https://miscsolutions.wordpress.com

        undefined 1 Reply Last reply 19 Dec 2020, 01:26 Reply Quote 0
        • undefined
          MarMed @dc42
          last edited by 19 Dec 2020, 01:26

          @dc42
          This is on beta4.1

          Warning: Auto tune of heater 2 failed due to bad curve fit (R=0.030, C=0.001:0.000, D=2.3)
          

          I think the problem may be a combination of a very low power heater(250w), and the situation that the heated bed gets the chamber close to the target temperature already, around 50C and I then use the the chamber heater to reach a stable 60C.

          I've tried many combinations when tuning, with hotend and bed heater off, with hotend and bed heater on, and setting the ambient temperature. Each tuning takes 5h+ before it fails.

          Any idea why my old heater parameters is giving me an error now?

          M307 H2 B1 A29.9 C1151.3 D55
          Error: M307: bad model parameters
          

          is there manual parameters that might work with my setup in 3.2?

          Help is appreciated.

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          • undefined
            dc42 administrators
            last edited by 19 Dec 2020, 10:54

            I have identified the problem and implemented a fix in 3.2RC1.

            Duet WiFi hardware designer and firmware engineer
            Please do not ask me for Duet support via PM or email, use the forum
            http://www.escher3d.com, https://miscsolutions.wordpress.com

            1 Reply Last reply Reply Quote 1
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