Cool! Will look at it in more detail in the next week or so. Three glasses of
wine at the Puerto Vallarta Yacht club New Years party means my head isn't
working as well as it usually does.Although to be truthful I went the Andy Pugh
way with a harmonic drive AC servo. One day I might even cast the pattern for
the frame.One of my 42 projects...Sent from my Samsung S10
-------- Original message --------From: andrew beck <[email protected]>
Date: 2025-12-31 8:51 p.m. (GMT-06:00) To: "Enhanced Machine Controller
(EMC)" <[email protected]> Subject: Re: [Emc-users] setting up
dual PID loops for servo encoders and
scales thanks johni found this which might be enough to make it work for mei
just need to sit down and get my head around the cascading PID
loopshttps://forum.linuxcnc.org/10-advanced-configuration/29851-combining-two-feedback-devices-rotary-axisOn
Thu, Jan 1, 2026 at 11:58 AM johnd <[email protected]> wrote:> Sounds
interesting. Do report on what you find out.JohnSent from my> Samsung S10>
-------- Original message --------From: andrew beck <>
[email protected]> Date: 2025-12-31 4:12 p.m. (GMT-06:00) To:>
"Enhanced Machine Controller (EMC)" <[email protected]>> Subject:
[Emc-users] setting up dual PID loops for servo encoders and> scales hey
guysjust looking for a config example if possible for a mesa> card from
someonethat has this nested PID loop setup.internal PID loop uses> servo motor
encoder and the outer Pid loop only usesthe Intergral value> with the scale and
then they get summed together todrive the motorI found> this link here on the
forum and want to try set it uphttp://>
wiki.linuxcnc.org/cgi-bin/wiki.pl?Combining_Two_Feedback_Devices_On_One_AxisThis>
page shows how to combine two position feedback devices into two PID'sfor> the
tuning and positioning of one axis. 1. This example has one high> resolution
linear scale on the axis table and one rotary encoder on the> axis drive
motor. 2. This could also be a rotary encoder on the ballscrew> and a rotary
encoder on the motor 3. This assumes the PID's are loaded> and connected to
the servo thread 4. linear scale position feedback> connects to the input of
the pid.4 PID 1. net X-linear-pos-fb 'linear> position feedback'
pid.4.feedback 5. motor encoder position feedback> connects to the feedback
input of the pid.0 PID 1. net> X-motor-pos-fb 'axis motor position
feedback' pid.0.feedback 6. position> command signal from LinuxCNC axis
connects to both PID command> inputs 1. net Xpos-cmd
axis.0.motor-pos-cmd pid.0.command> pid.4.command 7. bit signals from
LinuxCNC axis connnects to> enable/disable both PID loops 1. net Xenable
axis.0.amp-enable-out> pid.0.enable pid.4.enable 8. set PID loop output
limits as specified in> ini file 1. setp pid.0.maxoutput
[AXIS_0]PID_MAX_VEL 2. setp> pid.4.maxoutput [AXIS_0]PID_MAX_VEL 9. set
the motor encoder PID loop> gains 10. NOTE - I gain is set to zero - it would
fight the other> PID 1. setp pid.0.Pgain [AXIS_0]P 2. setp
pid.0.Igain 0 3.> setp pid.0.Dgain [AXIS_0]D 4. setp pid.0.bias
[AXIS_0]BIAS 5.> setp pid.0.FF0 [AXIS_0]FF0 6. setp pid.0.FF1
[AXIS_0]FF1 7. setp> pid.0.FF2 [AXIS_0]FF2 8. setp pid.0.deadband
[AXIS_0]DEADBAND 9.> setp ppmc.0.DAC.00.scale [AXIS_0]OUTPUT_SCALE 11.
set the linear scale> PID loop gains 12. NOTE - it has only I gain - all
other gains are set to> zero 1. setp pid.4.Pgain 0 2. setp
pid.4.Igain [AXIS_0]I 3.> setp pid.4.Dgain 0 4. setp pid.4.bias 0
5. setp pid.4.FF0 0> 6. setp pid.4.FF1 0 7. setp pid.4.FF2 0 8. setp
pid.4.deadband> [AXIS_0]DEADBAND 13. connect both PID output signals to
sum2.4 inputs> 14. sum the outputs of pid.0 and pid.4 15. pid.0 is using
motor encoder> feedback 16. pid.4 is using linear scale feedback 1. net>
Xoutput-motor pid.0.output sum2.4.in0 2. net Xoutput-linear> pid.4.output
sum2.4.in1 17. the summed PID output is connnected to the> DAC input signal
1. net Xoutput sum2.4.out 'DAC input' 18. repeat as> necessary for more>
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