Duet3D Logo Duet3D
    • Tags
    • Documentation
    • Order
    • Register
    • Login

    RRF 3.5beta2/closed-loop encoder config-problems

    Scheduled Pinned Locked Moved
    Duet Hardware and wiring
    4
    7
    376
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • CMPundefined
      CMP
      last edited by

      Hi,

      I have problems getting my encoder to work.

      The relevant config.g line looks like this:

      M569.1 P50.0 T2 C400.0 S200.0 R100.0 I0.0 D0.0
      M569 P50.0 D4 S0

      This doesn't seemed to be supported by the firmware, because I get this error:

      "Error in start-up file macro line 26: Encoder counts/rev must be at least four times steps/rev"

      The encoder is an RLS LM10IA Linear encoder that outputs an quadrature signal. The encoder and the steps/revolution is fixed. Is there someway I can ignore the error meassage?

      The purpose of the encoder is to counteract a bad/inconsistent Linear Motion System.

      I know that linear encoders should be combined with a magnetic shaft encoder but why shouldn't it work standalone?

      Thanks!

      droftartsundefined dc42undefined 2 Replies Last reply Reply Quote 0
      • droftartsundefined
        droftarts administrators @CMP
        last edited by

        @CMP As you say, the documentation says that linear encoders should be combined with a magnetic shaft encoder on the motor. The last sentence explains the reasoning behind this.

        A linear composite encoder comprises a linear quadrature encoder that tracks position on a linear axis (for example the Renishaw LM10IA or LM10IB) and a Duet3D magnetic shaft encoder. The shaft encoder handles motor commutation, the linear encoder is used to close the loop.

        I have asked @dc42 to comment on how it is expected to be set up.

        Ian

        Bed-slinger - Mini5+ WiFi/1LC | RRP Fisher v1 - D2 WiFi | Polargraph - D2 WiFi | TronXY X5S - 6HC/Roto | CNC router - 6HC | Tractus3D T1250 - D2 Eth

        jjemundefined 1 Reply Last reply Reply Quote 0
        • dc42undefined
          dc42 administrators @CMP
          last edited by dc42

          @CMP to use a linear axis encoder you also need a magnetic encoder on the stepper motor. The magnetic encoder is connected to the EXP1HCL via the ribbon cable connector and he linear quadrature cable is connected to the Molex KK connector. Our magnetic encoders will be in production shortly.

          Note, although we demonstrated this configuration at Formnext last November, it is still experimental. We have not tested it in a real printer or CNC machine yet.

          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 0
          • CMPundefined
            CMP
            last edited by

            @dc42 thanks for the quick reply!

            I will test it as soon as it becomes available.

            Is there a reason the ratio 'Encoder counts/rev' vs 'steps/rev' has to be that high? With my current encoder I'll only get a ratio of 2:1.

            dc42undefined 1 Reply Last reply Reply Quote 0
            • dc42undefined
              dc42 administrators @CMP
              last edited by dc42

              @CMP said in RRF 3.5beta2/closed-loop encoder config-problems:

              Is there a reason the ratio 'Encoder counts/rev' vs 'steps/rev' has to be that high? With my current encoder I'll only get a ratio of 2:1.

              For the shaft encoders we need a resolution high enough to perform commutation. When using both a linear axis encoder and a shaft encoder, the resolution of the linear encoder should not be as important.

              Btw I've updated the EXP1HCL wiki page and the M569.1 entry on the GCodes wiki page.

              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
              • jjemundefined
                jjem @droftarts
                last edited by

                @droftarts Is there scope for doing linear encoding (with the Renishaw LM10, for example) without also having the magnetic shaft encoder? I'm very space constrained so adding a magnetic encoder is very challenging, and feels superfluous as I would have thought we can do closed loop with just the linear encoder.

                dc42undefined 1 Reply Last reply Reply Quote 0
                • dc42undefined
                  dc42 administrators @jjem
                  last edited by dc42

                  @jjem said in RRF 3.5beta2/closed-loop encoder config-problems:

                  Is there scope for doing linear encoding (with the Renishaw LM10, for example) without also having the magnetic shaft encoder?

                  No. We need the magnetic encoder so that we can set the coil currents the desired angle ahead or behind the current step phase position to reasonable accuracy. In effect we are treating the stepper motor like a BLDC motor with a very high number of poles. BLDC motors that can operate over a wide range of speeds in either direction have built-in sensors for commutation.

                  OTOH it may in future be possible to run the stepper motor in open loop mode and use the linear encoder to monitor deviation between commanded and actual position.

                  Our magnetic encoder board takes up about 15mm of depth on the back of the stepper motor, including the connector.

                  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 0
                  • First post
                    Last post
                  Unless otherwise noted, all forum content is licensed under CC-BY-SA