Groups > sci.electronics.design > #518413

PID loop frequency

From	Fitzgerald <john.smith@mailinator.com>
Newsgroups	sci.electronics.design
Subject	PID loop frequency
Date	2018-10-05 16:07 +0200
Organization	A noiseless patient Spider
Message-ID	<pp7r7e$8p0$1@dont-email.me> (permalink)

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I'm working on a digital PID motion controller. The target/goal is to 
move at (very) constant velocity. Position feedback is from a linear 
encoder with quadrature output. The input to the controller is a linear 
ramp (i.e. constant velocity) and the PID changes the motor output to 
minimize the error. The system works, but I'm looking to improve its 
performance at low velocities.

At low velocities there are only a few pulses from the encoder per servo 
cycle. In the error signal I can clearly see this quantization. If I 
lower the frequency of the servo cycle; the controller performance 
increases (i.e. smaller velocity variations).

Two questions:
- Is there a method to determine optimal servo frequency?
- Would it be beneficial to separate the controller in two control 
loops; an inner velocity loop and an outer position loop. Perhaps with 
both running at different frequencies?

Any pointers to good documentation are appreciated.

Thanks,
Fitzgerald

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PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-05 16:07 +0200
  Re: PID loop frequency bill.sloman@ieee.org - 2018-10-05 07:53 -0700
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:08 +0200
      Re: PID loop frequency bill.sloman@ieee.org - 2018-10-09 00:11 -0700
  Re: PID loop frequency Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-05 10:58 -0400
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:12 +0200
  Re: PID loop frequency bitrex <user@example.net> - 2018-10-05 10:58 -0400
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:18 +0200
  Re: PID loop frequency Chris Jones <lugnut808@spam.yahoo.com> - 2018-10-06 01:04 +1000
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:30 +0200
      Re: PID loop frequency bill.sloman@ieee.org - 2018-10-09 00:21 -0700
      Re: PID loop frequency Chris Jones <lugnut808@spam.yahoo.com> - 2018-10-09 23:03 +1100
        Re: PID loop frequency bill.sloman@ieee.org - 2018-10-09 05:44 -0700
          Re: PID loop frequency Chris Jones <lugnut808@spam.yahoo.com> - 2018-10-10 00:01 +1100
            Re: PID loop frequency bill.sloman@ieee.org - 2018-10-09 07:33 -0700
  Re: PID loop frequency Lasse Langwadt Christensen <langwadt@fonz.dk> - 2018-10-05 08:49 -0700
  Re: PID loop frequency Jon Elson <elson@pico-systems.com> - 2018-10-05 13:59 -0500
  Re: PID loop frequency Hul Tytus <ht@panix.com> - 2018-10-05 19:52 +0000
    Re: PID loop frequency Jon Elson <elson@pico-systems.com> - 2018-10-05 15:46 -0500
      Re: PID loop frequency George Herold <gherold@teachspin.com> - 2018-10-05 18:05 -0700
      Re: PID loop frequency Hul Tytus <ht@panix.com> - 2018-10-06 18:49 +0000
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:38 +0200
  Re: PID loop frequency DJ Delorie <dj@delorie.com> - 2018-10-05 16:19 -0400
    Re: PID loop frequency Fitzgerald <john.smith@mailinator.com> - 2018-10-09 08:48 +0200
  Re: PID loop frequency tabbypurr@gmail.com - 2018-10-05 14:33 -0700
    Re: PID loop frequency Jasen Betts <jasen@xnet.co.nz> - 2018-10-06 02:14 +0000
      Re: PID loop frequency bill.sloman@ieee.org - 2018-10-05 19:49 -0700
        Re: PID loop frequency Klaus Kragelund <klauskvik@hotmail.com> - 2018-10-06 01:19 -0700
          Re: PID loop frequency bill.sloman@ieee.org - 2018-10-06 03:26 -0700
            Re: PID loop frequency George Herold <gherold@teachspin.com> - 2018-10-06 11:56 -0700
            Re: PID loop frequency Klaus Kragelund <klauskvik@hotmail.com> - 2018-10-08 06:27 -0700
              Re: PID loop frequency Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-08 10:22 -0400
                Re: PID loop frequency Klaus Kragelund <klauskvik@hotmail.com> - 2018-10-09 14:46 -0700

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