Mitsubishi Electric MR-J4-10A(-RJ) Instruction Manual page 760

18. MR-J4-03A6(-RJ) SERVO AMPLIFIER
(1) Dynamic brake operation
(a) Calculation of coasting distance
Fig. 18.2 shows the pattern in which the servo motor comes to a stop when the dynamic brake is
operated. Use equation 18.1 to calculate an approximate coasting distance to a stop. The dynamic
brake time constant τ varies with the servo motor and machine operation speeds. (Refer to (1) (b) in
this section.)
A working part generally has a friction force. Therefore, actual coasting distance will be shorter than
a maximum coasting distance calculated with the following equation.
V
0
t +
L = •
max
e
60
L : Maximum coasting distance ······················································································ [mm]
max
V : Machine's fast feed speed ····················································································· [mm/min]
0
J : Moment of inertia of the servo motor ································································· [× 10
M
J : Load moment of inertia converted into equivalent value on servo motor shaft ············· [× 10
L
τ: Dynamic brake time constant [s]
t : Delay time of control section ···························································································· [s]
e
The processing delay time about 3.5 ms.
(b) Dynamic brake time constant
The following shows necessary dynamic brake time constant τ for equation 18.1.
EM1 (Forced stop 1)
Fig. 18.2 Dynamic brake operation diagram
J
1 + L
··························································································· (18.1)
J
M
0.0025
0.0020
0.0015
0.0010
0.0005
0
ON
OFF
V
0
Machine speed
0136
0336
0 1000 2000 3000 4000 5000 6000
Speed [r/min]
HG-AK series
18 - 77
Dynamic brake
time constant τ
t
e
0236
Time
-4 2
kg•m ]
-4 kg•m 2 ]