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Phase Compensation Function - Mitsubishi Electric RD77MS2 User Manual

Melsec iq-r simple motion module.
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4.8

Phase Compensation Function

In synchronous control, delays in progresses, etc. cause the phase to deviate at the output axis motor shaft end with respect
to the input axis (servo input axis or synchronous encoder axis). The phase compensation function compensates in this case
so that the phase does not deviate.
Phase compensation can be set for the input and the output axis. It is possible to compensate using the delay time inherent to
the system based on the servo input axis or the synchronous encoder axis on the input axis side. It is also possible to use a
compensation delay time equivalent to the position deviation for each servo amplifier on the output axis side.
Phase compensation on delay time of the input axis
Set delay time inherent to the system in the phase compensation advance time of the input axis ("[Pr.302] Servo input axis
phase compensation advance time", "[Pr.326] Synchronous encoder axis phase compensation advance time").
The delay time inherent to the system is shown below.
■Delay time inherent to the system for a servo input axis
Operation cycle [ms]
0.444
0.888
1.777
3.555
■Delay time inherent to the system for a synchronous encoder axis
Operation cycle [ms]
0.444
0.888
1.777
3.555
Phase compensation of delay time of the output axis
Set delay time equivalent to the position deviation on the servo amplifier in "[Pr.444] Cam axis phase compensation advance
time" for the output axis. The delay time equivalent to position deviation of the servo amplifier is calculated using the following
formula. (When using MR-J3-B, MR-J4-B, and MR-JE-B)
Delay time [s] = 1000000 / Servo parameter "Model loop gain (PB07)"
When the feed forward gain is set, the delay time is set to a smaller value than the value listed above.
The model loop gain will change when the gain adjustment method is auto tuning mode 1 or 2. The model loop gain must not
be changed on the axis executing phase compensation through preventing change with the manual mode or interpolation
mode setting.
Setting example
When axis 1 is synchronized with an incremental synchronous encoder axis, the phase compensation advance time is set as
follows.
(If the operation cycle is as 1.77 [ms] and model loop gain of axis 1 is as 80.)
Setting item
[Pr.326] Synchronous encoder axis phase compensation advance time
[Pr.444] Cam axis phase compensation advance time
When overshoot or undershoot occurs during acceleration/deceleration, set a longer time for the phase compensation time
constant.
4 SYNCHRONOUS CONTROL
4.8 Phase Compensation Function
[Pr.300] Servo input axis type
Feed current value
Real current value
0 [s]
943 [s]
0 [s]
1834 [s]
0 [s]
1833 [s]
0 [s]
1833 [s]
[Pr.320] Synchronous encoder axis type
Incremental synchronous
encoder
1164 [s]
2433 [s]
4124 [s]
7676 [s]
Command to servo
amplifier
0 [s]
0 [s]
0 [s]
0 [s]
Synchronous encoder via servo
amplifier
1875 [s]
3655 [s]
5432 [s]
8986 [s]
Setting value
4124 [s]
(Reference: Delay time inherent to system for a synchronous encoder axis)
1000000 / 80 = 12500 [s]
Feedback value
1833 [s]
3612 [s]
5389 [s]
8944 [s]
Synchronous encoder via CPU
1164 + Scan time [s]
2433 + Scan time [s]
4124 + Scan time [s]
7676 + Scan time [s]

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