2.6Minimizing Positioning Time
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2.6.6 Mode Switch
Use the mode switch for the following purposes:
•
To prevent overshoot during acceleration or deceleration (for speed control).
•
To prevent undershoot during positioning in order to reduce settling time (for position con-
trol).
Speed
Overshoot
Actual motor
operation
Reference
Time
Undershoot
Settling time
In other words, the mode switch is a function that automatically switches the speed control
mode inside the Servopack
from PI control to P control
while certain conditions are being
established.
Note
(1) The mode switch is used to fully utilize performance of a Servo Drive to achieve very
high-speed positioning. The speed response waveform must be observed to adjust
the mode switch.
(2) For normal use, the speed loop gain and position loop gain set by autotuning provide
sufficient speed/position control.
Even if overshoot or undershoot occurs, they can be suppressed by setting the accel-
eration/deceleration time constant for the host controller, the soft start time constants
(Cn-07, Cn-23), or smoothing time constant (Cn-26) for the Servopack.
Mode Switch Selection
Servopacks can use four types of mode switches (1 to 4). To select a mode switch, use the
following memory switch. The mode switch setting methods for speed/torque control and
position control are slightly different.
TERMS
From PI control to P control
PI control means proportional/integral control and P control means proportional control. In
short, switching “from PI control to P control” reduces effective servo gain, making the servo
system more stable.
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