
B-65232EN/03 DESCRIPTIONS FOR FANUC AC SERVO MOTOR β series 4.SELECTING A MOTOR
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(b) Position loop gain
Fill in this blank with a value which is considered to be
settable judging it from the inertia value based on
experiences. Since this value is not always applicable due
to rigidity, damping constant, and other factors of the
machine tool, it is usually determined on the actual machine
tool. If the position detector is mounted outside the motor,
this value is affected by the machine tool rigidity, backlash
amount, and friction torque value. Enter these values
without fail.
(c) Deceleration stop distance and dynamic brake stop distance
In these items, the coasting distance of the machine tool at
the machine tool stroke end is entered. Usually, a stroke
end consists of two limit stages. The stage-1 limit triggers a
deceleration stop, while the stage-2 limit triggers a dynamic
brake stop. When the stage-1 limit is tripped, the displayed
position exactly matches the stop position of the machine
tool. When the stage-2 limit is tripped, the position data is
lost. The stage-2 limit is designed to stop the machine tool
if the machine tool becomes uncontrollable and runs away.
Therefore, always install a stage-2 limit to protect the
machine tool from damage.
• Deceleration stop distance
Enter the coasting distance when the machine tool is
decelerated and stopped at the stroke end.
V
m
: Rapid traverse rate, mm/min or rev/min
l
1
: Coasting distance due to delay time t
1
of
receiver
l
2
: Coasting distance due to deceleration time t
2
l
3
: Servo deflection amount
t
1
: Usually about 0.02 seconds
Coasting distance = Vm/60×(t
1
+t
2
/2+1/ks)(mm or deg)
ks : Position loop gain (sec
-1
)