Mitsubishi Electric M700V Series Manual page 302

MITSUBISHI CNC
III Functional Specifications
13.2.2 Dual Feedback
M720VW
M system ○
L system ○
If the motor and machine coupling or machine system's rigidity is low (ex. large machine, etc.) when using a
closed loop system, the response during acceleration/deceleration will vibrate and cause overshooting. This
can cause the position loop gain from increasing. The dual feedback function is effective in this case.
To validate the dual feedback function, use position feedback with a motor side detector in ranges with high
acceleration to enable stable control. In ranges with low acceleration, use position feedback with the
machine side detector (scale). This will make it possible to increase the position loop gain.
The machine side detector (scale) is required separately.
(b)
+
-
(l)
-
(a) Dual feedback control
(b) Position command
(c) Position control
(d) Position droop
(e) Servo motor
(f) Linear scale
(g) Table
(h) Speed command
(i) Position FB
(j) Primary delay filter
(k) High frequency FB element
(l) Low frequency FB element
(m) dead band
The state will approach the semi-closed loop system as the primary delay filter's time constant increases, so
the position loop gain limit will increase. Note that the limit of the position loop gain increased with the dual
feedback function is the same as the position loop gain limit for a semi-closed system that does not use a
machine side detector (scale, etc.). In addition, the positioning time will increase as the primary delay filter
time constant increases.
III - 300
M730VW M750VW
○ ○
○ ○
(d)
(c)
(k)
+
(j)
(a)
M720VS M730VS
○ ○
○ ○
(h)
(e)
ENC
(i)
(m)
+
-
(i)
M750VS
○
○
(g)
(e)