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BRX motion control with PID of VFD via analog or MODBUS?

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  • BRX motion control with PID of VFD via analog or MODBUS?

    Before I actually purchase a BX-DM1E-18ED23-D I just wanted to check that it can do what we need. Not too worried about _how_ to do it at this stage, just if the BRX _can_.

    The idea is to generate a trapezoidal motion profile, apply PID control with an encoder on the motor, then comand a generic VFD via MODBUS or analog. From reading the manual and playing with the Do More software I've found very similar functions but nothing exactly like what I'm after.

    I haven't touched a PLC since university but I'm looking forward to getting stuck in - if our desired application is feasible with the BRX.

    Cheers,

    Scott.


  • #2
    BRX will do all of the things you are describing, and it shouldn't be too hard to put it all together. Is driving the motor more directly not an option?

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    • #3
      Thanks very much for that.

      Do you mean why not talk to the VFD via a network protocol?

      The initial setup will be a proof-of-concept using motors and (cheap) VFDs that we already have.

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      • #4
        I think BobO means why do you think you need PID? There are feedback mechanisms in place for a variety of ways to do motion with an encoder. Any of these can work in a virtual environment with no physical motor directly attached while using your physical encoder.

        Taking the motion out to an analog or Modbus signal is the easy part. Take CurrentPosition and scale it appropriately and send it to a register that you push out.
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        • #5
          I just assumed that PID would be needed to correct any deviation from the desired motion profile. If there's a better way I'm all for it!

          I will probably still use PID at some stage just for the experience of setting it up & tuning etc.

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          • #6
            Originally posted by congoflood View Post
            I just assumed that PID would be needed to correct any deviation from the desired motion profile. If there's a better way I'm all for it!

            I will probably still use PID at some stage just for the experience of setting it up & tuning etc.
            It'll work fine. BRX can easily generate the profile, and PID can easily apply it to the output. Something less complicated would be output = sqrt(error) * gain. Works well and only requires tuning the gain.

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            • #7
              That's great, thanks so much for your help - really appreciate it.

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