
B--65245EN/02
E. SERVO CHECK BOARDAPPENDIXES
235
(5) VCMD signal
The VCMD signal is used to output a velocity command. This signal
can also be used to measure the minute vibrations of the motor and
any uneven feed.
Befor e obser ving this signal, che ck that bit 0 of para me ter No. 14 is 0.
The amplitude of the VCMD signal can be switched using bits 0 and
1 of parameter No. 13.
The VCMD signal switches between +5 V and --5 V. Switch the
amplitude using this parameter if it is difficult to observe the
waveform.
#7 #6 #5 #4 #3 #2 #1 #0
13 VCM2 VCM1
VCM2 VCM1 Number of specified revolutions/5 V
1 1 0.9155 rpm
1 0 14 rpm
0 1 234 rpm
0 0 3750 rpm
First, observe the entire waveform of the signal using the DC mode
of the oscilloscope, then switch to AC mode and enlarge the range.
Minute vibration and uneven positional shifts can be checked.
VCMD
GND
GND
E
1/f
DC mode
AC mode
Enlarged
Letting W (rpm/5 V) be the signal conversion ratio of the VCMD
waveform, the voltage per positional deviation amount pulse is:
Voltage (V) per positional
deviation amount pulse
300 x position gain (s
-- 1
)
Number of position feedback pulses/motor
revolution x W
=
(Example)
Supposing position gain = 30 (s
-- 1
), number of position feedback
pulses/motor revolution = 10,000, E = 300 mV, 1/f = 20 ms, VCM1
= 0, and VCM2 = 1, the voltage per positional deviation pulse is: 64
mV/pulse
Thus:
Table vibration = 300 × 1/64 = 4.6 ←m
Vibration cycle = 50 Hz