No idea why the phone strips out theCRLFSent from my Samsung S10
-------- Original message --------From: gene heskett <[email protected]>
Date: 2026-01-01 3:39 a.m. (GMT-06:00) To: [email protected]
Subject: Re: [Emc-users] setting up dual PID loops for servo encoders
andscales On 12/31/25 23:44, johnd wrote:> 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 S10This is hard to read without any LF's or
CR/s.> -------- 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>
axes_______________________________________________Emc-users mailing>
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https://lists.sourceforge.net/lists/listinfo/emc-users>_______________________________________________Emc-users
mailing
[email protected]https://lists.sourceforge.net/lists/listinfo/emc-usersLet
me suggest a different solution. On that I have found quite useful as so far
8 axises on various machines have been converted. Toss the conventional PID's,
drivers and motors in the bin and replace them with closed loop
stepper/servo's. Feed the drivers directly from the TP, no PID's to allow any
error in what is sent. I am doing exactly that, converting both my linuxcnc
machines and my 3d printers. The motors contain an encoder that feeds back ONLY
to the drivers, LinuxCNC is not aware of these encoders, which in turn controls
the motors much more precisely.3 Huge advantages ensue.1. The motors are fed
only as much power as it takes to do the job, so they run 60C cooler in most
cases.2. the control is much faster in that if a motor overshoots getting
stopped, its reversed and backed up to the correct position, or if it falls
behind, the driver turns up the current until the motor has caught up. This is
full time active by the microsecond control, does not depend on low latency in
the OS.3. Speeds are multiplied, bringing steppers into servo speed responses
if the supply voltage is turned up to overcome motor inductance faster.On 72
volts, 3000 or more rpms can be had with total control. No loss of "home" has
occurred.All this is at a cost increase of maybe $25 per axis. This translates
to 3d printers that can move 10x faster than OOTB, can engrave text on the
sides of half nuts w/o any Input Shaper tomfoolery. Currently the Hanpose LC42
and LC57 drivers are the only problem, in 3d printers the 5 volt logic
overdrives the step/dir opto couplers (6N137's) leading to their early failure,
so I've added 150 to 190 ohm current limiters in those 2 inputs using the
signals delivered to the stepstick sockets on the BTT octopus-pro V1.1
controller cards I use for all my printer rebuilds. My power supply's are 72
volts. Hanpose has been advised of the problem. Where the logic signals are
3.3 volts, like much of the mesa stuff, no problem.>
_______________________________________________> Emc-users mailing list>
[email protected]>
https://lists.sourceforge.net/lists/listinfo/emc-usersCheers, Gene Heskett,
CET.-- "There are four boxes to be used in defense of liberty: soap, ballot,
jury, and ammo. Please use in that order."-Ed Howdershelt (Author, 1940)If we
desire respect for the law, we must first make the law respectable. - Louis D.
BrandeisDon't poison our oceans, interdict drugs at the
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