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Productivity feature request - Closed loop feedback for move commands

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  • Productivity feature request - Closed loop feedback for move commands

    I would really like there to be a way to more easily do closed loop positioning in the Productivity line. I realize that the HSO modules keep track of their position at all times, and I realize you can use a Simple Move instruction to tell the axis to move to a specific location. However, there should be a config option in the simple move command where you could check a box to enable closed loop control and then select the encoder the move will use. When using the closed loop option in the move command, the move would execute as programmed, and while it is executing the HSO could be running a feedback check on the encoder to make sure it is actually moving the way it should be, and correct for additional (or fewer) pulses to the move to ensure the command reaches the exact real world position the command was programmed for.

    The HSO modules have 6 GP inputs, so perhaps on the hardware config page for the input setup (where you type in the gp input tag names) there could be an option to configure the inputs as encoders. These encoders would be a part of the HSO module setup and just like when you drag a move instruction into the ladder you choose which channel the move will use, the same type of option could be given when selecting closed loop mode for the move. Based on which HSO channel the move is set to use, it gives the option of the first or second encoder wired to the HSO to be used for closed loop feedback data. Since there are already 6 inputs, that is perfect for 2 quadrature encoders already, which would give each HSO output channel the ability to use closed loop control if desired. Perhaps this option of closed loop feedback could be placed into the "registration" area of the move command, in the same way that you select which gp input to use as the registration mark, you could just check a closed loop box within the registration section and it changes from selecting between the 6 gp inputs to selecting between the first or second feedback encoder.

    I hope I was able to make my thoughts clear for the application and potential implementation. If anyone has questions or wants clarification let me know.
    It looks like bdehner is from the productivity team on these forums? Could you give me your thoughts on this?
    Last edited by MikeN; 03-31-2017, 11:11 AM.

  • #2
    Thanks MikeN for the post. I forwarded your request to the Product Engineer for consideration. Since we receive a lot of useful feedback on this forum, I act as more of a facilitator making sure comments/requests get to where they need to be. Not really part of any specific team and since I do not know all of the ins and outs of this particular module it is best I leave it to the experts. However, your post on how to improve the functionality of the HSO module is greatly appreciated and the team has been notified, thanks again.
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    • #3
      I would Second this feature request. I would prefer to use closed loop feedback on all of my motion applications. Especially for jam detection and load changes on moving equipment.


      • #4
        What are the chances of this happening? Closed loop feedback is very valuable to have in motion applications.


        • #5
          I wouldn't try and close the loop in the PLC as modern closed loop steppers and servos do a fine job on their own. A standard stepper isn't going to do well if you start missing steps due to jams or misapplication. There are other brands that have closed loop stepper systems that work very well have adjustable position bands that can indicate if they deviate from their target position.

          Most PLC motion cards are lacking when it comes to anything other than standard velocity or position moves.