Adjusting commanded RPM to real RPM

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13 Feb 2018 13:10 #105819 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
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
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
In that case can you post all your config files?

Chris M

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19 Feb 2018 13:07 #106168 by timmert

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
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

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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