YASKAWA MOTIONPACK-110 Descriptive Information page 247

12.1.2 SELECTION OF SERVOMOTORS (Cont'd)
1
SPEED N ACCEL DECEI.
[rpm] /CONSTANT_
/ SPEED STOP
_ t= == t4 _ TIME t [s]
TA
TORQUE T [
[kg.m] TI.
J TIME t Is]
Fig. 12.2 Operation Pattern
I
12.1.3 EXAMINATION OF SERVO PERFORMANCES
For the servo system having a position feedback loop, as in the case of Motionpack-110, the
position loop gain (sensitivity) must be set to the optimum value. If the gain is too high,
the machine tends to operate roughly but, if the gain to too low, a longer time is needed for
positioning. The position loop gain is called the Kp value and expressed by the ratio between I
positional deviation pulse _ and maximum command pulse f i,
Kp= f'" [pulse/s] [i/s] ...................................................... (7)
[pulse]
i
Servo performance is enhanced as the Kp value increases. The largest possible Kp value
(largest possible Kp value) can be calculated from the following formulas:
KpL 1.46 [l/s): .................................................................. (8) a
t
I
GD2L + GD2M +Nt_
t = Is] (9)
375 ( TA + Tt )
where, t: Acceleration time of motor.
For example, if V = 30 Ira/mini, _ o = 0.01 [mm_ and t = 0.05 [sl, then Kp value is
approximately 1.46/0.05 = 29.2 [1/sl.
Also, from equation (7), _ = 50,000/29.2 - 1712 pulses. That is, deceleration begins
at 1712 pulses or 17.12 mm behind and then the system stops. (However, deceleration
constant is zero.)
30,000/60
Note: fi, - 0.01 - 50,000 [PPs_ I
More accurate values of Kp can be obtained if Kp is calculated using equations (8)
and (9)when setting the parameters for position loop gain adjustment.
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