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5 Servo Adjustment
MITSUBISHI CNC
5.2.3 Position Loop Gain
(1) Setting the position loop gain
The position loop gain 1 (SV003: PGN1) is a parameter that determines the trackability to the command position. 33
is set as a standard. Set the same position loop gain value between interpolation axes.
When PGN1 is raised, the trackability will be raised and the settling time will be shortened, but a speed loop that
has a responsiveness that can track the position loop gain with increased response will be required. If the speed
loop responsiveness is insufficient, several Hz of vibration or overshooting will occur during acceleration/
deceleration. Vibration or overshooting will also occur when VGN1 is smaller than the standard value during VIA
adjustment, but the vibration in the position loop occurs generally 10Hz or less. (The VIA vibration occurs from 10 to
20Hz.) When the position control includes machine resonance points (Position control machine resonance points
occur at the tool end parts, etc.) because of insufficient machine rigidity, the machine will vibrate during positioning,
etc. In either case, lower PGN1 and adjust so that vibration does not occur.
If the machine also vibrates due to machine backlash when the motor stops, the vibration can be suppressed by
lowering the PGN1 and smoothly stopping.
If SHG control is used, an equivalently high position loop gain can be maintained while suppressing these
vibrations. Adjust SHG control by raising the gain gradually after setting PGN1 as 1/2 a value of PGN1 at which a
vibration does not occur under the normal control. If the PGN1 setting value is more than 1/2 of the normal control
PGN1 when SHG control is used, there is an improvement effect in position control. (Note that for the settling time
the improvement effect is at 1/ or more.)
【#2203】 SV003 PGN1 Position loop gain 1
Set the position loop gain. The standard setting is "33".
The higher the setting value is, the more accurately the command can be followed, and the shorter
the settling time in positioning gets, however, note that a bigger shock will be applied to the machine
during acceleration/deceleration.
When using the SHG control, also set SV004 (PGN2) and SV057 (SHGC).
---Setting range---
1 to 200 (rad/s)
【#2204】 SV004 PGN2 Position loop gain 2
When performing the SHG control, set the value of "SV003 x 8/3" to "SV004".
When not using the SHG control, set to "0".
---Setting range---
0 to 999 (rad/s)
【#2257】 SV057 SHGC SHG control gain
When performing the SHG control, set to SV003(PGN1)*6.
When not using the SHG control, set to "0".
---Setting range---
0 to 1200 (rad/s)
CAUTION
Always set the same value for the position loop gain between the interpolation axes.