On Wed, 3 Mar 2021, John Dammeyer wrote:
Date: Wed, 3 Mar 2021 16:42:25 -0800
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: [Emc-users] Following Error Joint 2
I made another video with the new 3D printed pulley. Much better balanced as
I made the inner hole and outside hub thicker and then bored and turned it to
the correct diameter and concentric with each other. Now just shows the Z axis
jogging up and down after homing. I still get the occasional following error
but it seems that's a LinuxCNC issue and not the motor. Or it's electrical
noise because the table is loaded down with two vices and a rotary table. I
think close to 200 lbs extra. I'll have to weigh it.
https://youtu.be/AJWI09C6h7U
I've read through this thread. I'm using the MESA 7i92H which is Ethernet
based and it's only the PC and the MESA on the network.
https://forum.linuxcnc.org/10-advanced-configuration/27171-joint-2-following-error?start=10
Without all the extra weight on the table there is no following error. If I
remove BACKLASH compensation there is no following error. It appears to go
away if I make sure that the STEPGEN_MAXACCEL is set to double the
MAX_ACCELERATION.
My parameters are
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
PCW on that forum stated that "For PID control of the stepgen, the stepgen is
put into velocity mode and a basic velocity mode PID setting is used (FF1 =
1.000, FF2 = .001 (servo period) P= ~150)"
My SERVO_PERIOD = 1000000 So should FF2 be set to that? Or is the stepgen
even in velocity mode and does it matter?
You need to double the stepgen acceleration settings if backlash
is enabled. That alone may be the reason for your following errors.
Normally FF2=0 is ok unless you are worried about following errors in the u
region (FF2 should be set for the number of seconds between reading the stepgen
position and writing the new velocity so normally a very small number)
What I don't understand is why extra weight made it show up. The AC Servo
Drive is not showing an error and motor current rarely goes above 3.5A at
220VAC or about 770W.
John
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Peter Wallace
Mesa Electronics
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