On Tue, 15 Jun 2021, John Dammeyer wrote:
Date: Tue, 15 Jun 2021 16:14:00 -0700
From: John Dammeyer <jo...@autoartisans.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "'Enhanced Machine Controller (EMC)'" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] Spindle Control
Kind of cool to do an M3 S10 and see the what would be the spindle turning at
10 RPM with STEP/DIR control. (all on my test bench with a smaller motor at
the moment and Pi4/7i92H instead of PC/7i92H.
Been working on that all afternoon. Moved controllers around. Moved motors.
Nothing. And yet the motor worked fine on the machine and under the Pi4 and
7i92 also ran correctly with PWM/DIR. But not STEP/DIR. Didn't seem to
matter what parameters I changed in the servo motor. I'd switch back and
forth between the two different .BIT files in the 7i92H.
I took a step backward and started cloning the Z axis parameters into the
spindle parameter in the INI file. The P parameter was 0.0 Once I set it to
1000.0 spindle stepping worked. Which makes sense. No Proportional Gain, no
velocity.
MAX_VELOCITY = 50.0
MAX_ACCELERATION = 300.0
P = 1000.0
I = 0.0
D = 0.0
FF0 = 1.0
FF1 = 0.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 3000.0
So when controlling an intelligent AC Servo Drive what is an ideal value for
P? It's open loop at the moment, until I add an encoder to the spindle.
Anything else required to make open loop reliable? Once there's an encoder on
the spindle how much tuning is needed given that it's step/dir and not PWM
with encoder feedback?
Thanks
John
If you are outputing a velocity command (either a stepgen rate or a PWM
value), P=0 should be fine, because FF0=1 meaning the PID output that drives the
stepgen or PWMgen will equal the input command. Basically the PID compoment is
just passing the commanded spindle RPM to its output so when P=0 (and I=0) you
are running open loop, but it should work in this configuration. If you are
using a stepgen, there should be no need for P (or PID) at all, since the stegen
rate accuracy will be better than .01% or so.
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Mesa Electronics
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