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4 Servo Adjustment
MITSUBISHI CNC
4-3-3 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)
Always set the same value for the position loop gain between the interpolation axes.
CAUTION