Adjusting commanded RPM to real RPM

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13 Feb 2018 13:10 #105819 by timmert
Adjusting commanded RPM to real RPM was created by timmert
Hello,

I have a question about my encoder setup
I just installed a new VFD and now my spindle RPM is different than the commanded RPM.
So for example: I enter a M3 S2000 and the spindle turns 2500rpm (rpm feedback is from my encoder).
How can I correct this? Spindle pulley and motor pulley are different sizes.

.ini information:
ENCODER_SCALE = -150.0
MAX_OUTPUT = 2990
OUTPUT_SCALE = 2990
OUTPUT_MIN_LIMIT = 0
OUTPUT_MAX_LIMIT = 2990

.hal information.
I used the near component for the spindle at speed.
# ---setup spindle control signals---
net spindle-cmd-rpm     <= motion.spindle-speed-out
net spindle-cmd-rpm-abs <= motion.spindle-speed-out-abs
net spindle-cmd-rps     <= motion.spindle-speed-out-rps
net spindle-cmd-rps-abs <= motion.spindle-speed-out-rps-abs
net spindle-at-speed    => motion.spindle-at-speed


# ---Setup spindle at speed signals---

net spindle-vel-cmd-rps-abs => near.0.in1
net spindle-vel-fb-rps => near.0.in2
net spindle-at-speed motion.spindle-at-speed <= near.0.out
setp near.0.scale 1.10

#  Use ACTUAL spindle velocity from spindle encoder
#  spindle-velocity bounces around so we filter it with lowpass
#  spindle-velocity is signed so we use absolute component to remove sign
#  ACTUAL velocity is in RPS not RPM so we scale it.

setp     scale.spindle.gain 60
setp     lowpass.spindle.gain 1.000000
net spindle-vel-fb-rps        =>     scale.spindle.in
net spindle-fb-rpm               scale.spindle.out       =>   abs.spindle.in
net spindle-fb-rpm-abs           abs.spindle.out         =>   lowpass.spindle.in
net spindle-fb-rpm-abs-filtered  lowpass.spindle.out 

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13 Feb 2018 23:41 #105845 by cmorley
Replied by cmorley on topic Adjusting commanded RPM to real RPM
You must adjust the scale of the command speed.
You can do this either at the vfd or by adjusting
OUTPUT_SCALE
OUTPUT_MIN_LIMIT
OUTPUT_MAX_LIMIT

It seems at the moment you have it set so that when the VFD get a 10 volt command, it i supposed to be turning the spindle 2900 RPM.
Is that right?

Chris M

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14 Feb 2018 16:41 #105931 by timmert
Replied by timmert on topic Adjusting commanded RPM to real RPM
Hello Chris,

Yes that's right. I did use 0-10v with my old VFD
With the new one I use modbus/serial connection

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14 Feb 2018 17:25 #105933 by cmorley
Replied by cmorley on topic Adjusting commanded RPM to real RPM
In that case can you post all your config files?

Chris M

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19 Feb 2018 13:07 #106168 by timmert
Replied by timmert on topic Adjusting commanded RPM to real RPM

File Attachment:

File Name: custom_postgui.hal
File Size:1 KB

File Attachment:

File Name: lathe_2018-02-19.hal
File Size:11 KB

File Attachment:

File Name: lathe_2018-02-19.ini
File Size:7 KB
Attachments:

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23 Feb 2018 14:31 #106385 by timmert
Replied by timmert on topic Adjusting commanded RPM to real RPM
I played with the OUTPUT_SCALE, OUTPUT_MIN_LIMIT, OUTPUT_MAX_LIMIT but there is 0 change in the RPM the encoder reads and the commanded spindle speed.

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01 Mar 2018 14:11 #106805 by andypugh
Replied by andypugh on topic Adjusting commanded RPM to real RPM

I played with the OUTPUT_SCALE, OUTPUT_MIN_LIMIT, OUTPUT_MAX_LIMIT but there is 0 change in the RPM the encoder reads and the commanded spindle speed.


If you are using Modbus then these won't have any effect.

There are two options: You can use a PID component to achieve closed-loop spindle control, or you can scale the spindle command sent on the serial link to suit the gear ratio.

The command sent on Modbus will always be interpreted as a motor speed rather than a spindle speed.

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