TB234 Rev4 CNC11 Velocity Mode Drive Tuning
This document is a quick start visual walk through of tuning Velocity Mode drives in CNC11 3 03 rev61
and above
Tuning is done in the PID Config menu This menu is located from the main screen at F1 Setup
F3
Config
F4 PID
F1 PID Config
Kv1 is fine tuned first followed by Kp and lastly Ki In some cases Kd is required as well This is typical on
for example very old Fanuc Velocity Control Units To begin tuning the drives enter the recommended
PID values of Kp = 0 04* Ki = 0 0005* Kd = 0* Limit = 2560000 Kg = 0 Kv1 = 80** Ka = 0
*These numbers reflect 10mm 12mm pitch ballscrew and 160000 counts/rev of the motor To figure out an
appropriate Kp and Ki value divide 160000 by your counts/rev of the motor and multiply by Kp and Ki
values above to get ballpark values Â
**This value assumes that the Max Rate that you want to use is 80% 90% of the 3rd party drive setting for
Max Rate Otherwise use the ratio of CNC11 Max Rate to 3rd party drive Max Rate
If there is a Tech Bulletin that describes the setup and wiring for the specific drive you are using refer to it
for more accurate PID values In velocity mode Kp and Ki are for maintaining positional accuracy during
and after motor movement while Kv1 is for Feed Forward command to the drive and controls most of the
movement The goal of tuning is to find the settings that produce the least error when the motor is moving
or holding
The following Tech Bulletins already exist with more on the way
Drive Tech Bulletin Number
Delta AB and A2 231
Glentek Alpha 232
Sanyo Denki forthcoming 239
Maxsine EP100 forthcoming 240
Fanuc Black and Yellow cap 233
Please note that all machine setup should already be done specifically limit switches and E Stop wiring
and configuration before tuning the drives You should tune the motors un coupled to the machine then
couple them and fine tune the settings if required
Kv1 Tuning
Kv1 is tuned first because it is the main controlling parameter in Velocity Mode The goal is to get the error
at the start and stop of the move as close to zero as possible Start tuning and compare to Figures A and
B below and Figures 1 5 following the PID Setup Menu For plots that look like Figure A increase Kv1 until
the error at the start of the move is as close to zero as possible without going across zero to the negative
For plots that look like Figure B decrease Kv1 until the error goes positive then bring it back so it is as
close to zero as possible
Kp Tuning
Once Kv1 is tuned start adjusting Kp Compare plots to Figures C D and 6 10 Increase Kp until
oscillations start to look like Figure C Note this value then decrease Kp until oscillations start to look like
Figure D Note this value Find the average of the two values by adding them together and dividing by 2
then type that value in for Kp
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Ki Tuning
Now that Kv1 and Kp are tuned start tuning Ki and compare to Figures E F and 11 15 Reduce Ki until
there is an obvious offset in error away from zero like Figure E Increase Ki until the offset just goes away
and use that value Compare to Figure F below Set the Limit value to 50/Ki This will prevent the Ki term
from growing too large in extenuating circumstances
PID Setup Menu
The PID Setup Menu has changed and now contains an oscilloscope like tuning screen with the PID
parameters This allows for fast and accurate tuning of PID values Go to the PID Setup screen by hitting
F1
F3 F4 F1 This is the main screen where the tuning occurs
Button Overview
F1 brings up the program that will be executed It is called
PID_collection_moves txt This is a standard G Code program The default program moves the
X axis 0 5? back and forth at 100 inches/minute
F2 goes to a screen that prompts for Cycle Start to be pressed Once that is
done the program will start running and come back to the view above
F3 allows manual changing of the horizontal and vertical axes on the screen This
allows you to refocus what is displayed
The Zoom In/Out/All buttons F5 F6 and F7 respectively change the viewable range on the
screen in both horizontal and vertical directions
F8 changes the axis from which data is gathered Only one axis can be shown
at a time If you can see that the motor is moving but nothing shows up on screen push this
button to see if the wave form shows up Only axes labeled X Y Z U V W A B Â or C can be
shown on this screen
F9 should be used after running a job if you want to stay on this screen
F10 goes back a screen to the PID menu
Esc If you wish to discard changes
General Tuning Procedure
Make sure you are in the middle of travel and there are no faults
Open the tuning program by pushing F1 from the PID Config screen as seen
above Change the axis labels to match with what axis you are tuning
Change the feedrate to a typical cutting speed for best results Any speed may be used
however the speed you are tuning at will be most accurate in positioning
Change the move distance in the program to be something that will allow the motor to get up
to speed and be at speed for a few hundred milliseconds This is observed by noting a flat in the
RED ExpV line The faster the move speed the longer the distance must be to get up to speed
A bi directional move is recommended to prevent running out of travel as the program
continues to cycle
Save and close the program
Hit F2 and then Cycle Start to begin running the program
Move the cursor over to Kv1 for the axis that is moving and using the PageUp or PageDown
for a 1% change and Shift+PageUp or Shift+PageDown key for a 10% change modify Kv1
according to the Kv1 tuning page
Next modify Kp according to the Kp tuning page
Lastly Modify Ki according to the Ki tuning page
Move on to each axis in turn and tune each one as specified above
When tuning is complete save a report and email it to Tech Support
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Document History
Rev4 Created on 2011 02 04
by #297
Rev3 Created on 2010 07 19
by #297
Rev2 Created on 2010 06 25
by #297
Rev1 Created on 2010 03 23
by #297