User Manual Of EL7-EC** AC Servo
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6.4 Manual gain adjustment
Due to limitation of load conditions, automatic gain adjustment might not achieve
expected performance. Control can be improved through manual gain adjustment
The servo system is made up of 3 control loops. From outer to inner: position loop,
velocity loop, current loop as shown in the diagram below.
Position
control
Velocity
control
Velocity
feedforward
Torque
feedforward
Current
control
Motor
Encoder
Position
feedback
Current
feedback
Command
input
Command
filter
+
-
+
-
+
+
-
Velocity
feedback
-
Inner control loop demands higher responsiveness. In order to avoid system instability,
please tune in accordance to this principle. Current loop gain usually satisfies the
responsiveness demand without tuning. When gain adjustment is done under position
control mode, in order to keep the system stabile, position and velocity loop gain have to
be increased at the same time to make sure the responsiveness of the position loop is
lower than velocity loop.
Steps to tuning (Position and velocity control)
For servo gain, if any one of the parameters is changed, please modify other gain related
parameters accordingly. Make sure to the change at around 5% and follow the rules as
below.
1)
Increase responsiveness
a)
Reduce torque command filter time
b)
Increase velocity loop gain
c)
Decrease velocity loop integral time
d)
Increase position loop gain
2)
Decrease responsiveness, prevent vibration and over shoot
a)
Reduce position loop gain
b)
Increase velocity loop integral time
c)
Reduce velocity loop gain
