Groups > sci.electronics.design > #518457

Re: PID loop frequency

From	DJ Delorie <dj@delorie.com>
Newsgroups	sci.electronics.design
Subject	Re: PID loop frequency
References	<pp7r7e$8p0$1@dont-email.me>
Date	2018-10-05 16:19 -0400
Message-ID	<xnpnwocfiw.fsf@delorie.com> (permalink)

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Fitzgerald <john.smith@mailinator.com> writes:
> I'm working on a digital PID motion controller.

Isn't everyone?  ;-)

> - Is there a method to determine optimal servo frequency?

In my case, the pid loops ran at the PWM 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?

I ended up with three PID loops:

* the innermost one managed the current through each phase of the
  motor.  I.e. this is a torque loop.

* the next one is the RPM loop

* the outermost one is the position loop.

For high RPM, you can drive the RPM loop directly.  For low RPM, you can
calculate the desired position vs time and drive the position loop
instead.  It will lag a bit according to the holding torque, but follow
the desired RPM.

I can usually keep the motors within a few counts of the desired
position, at 4000 counts/rot.

Thread

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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