Appendix - 36
MELSEC-A
APPENDICES
DEVIATION COUNTER
Deviation counters have the following two
functions.
1) To count the command pulses issued from
the AD75, and transmit the count value to
the D/A converter.
2) To subtract the feedback pulses from the
command pulses, and run the motor by the
deviation value (droop pulse) of the
command pulses and feedback pulses until
the command pulses reaches 0.
PLG Encoder
Command
pulses
Deviation
counter
D/A
convertor
Motor
Feedback pulses
DOG SIGNAL
The near-point dog of the machine zero point
return.
DROOP PULSE
Because of inertia (GD
2
) in the machine, it will
lag behind and not be able to track if the
positioning module speed commands are
issued in their normal state.
Thus, for a servomotor, a method is used in
which the speed command pulses are delayed
by accumulation in a deviation counter. These
accumulated pulses are called the droop
pulse.
The deviation counter emits all pulses and
returns to 0 when the machine stops.
1,000
pulses
200 pulses
accumulate
in the
counter
800
pulses
Voltage
D/A
DWELL TIME
This is the time taken immediately after the
positioning is completed to adjust for the droop
pulses in the deviation counter. The
positioning will not be accurate if this time is
too short.
DYNAMIC BRAKE
When protection circuits operate due to power
failures, emergency stops (EMG signal) etc.,
this function is used to short-circuit between
servomotor terminals via a resistor, thermally
consume the rotation energy, and cause a
sudden stop without allowing free run status of
the motor.
Braking power is generated by
electromagnetic brakes only when running
motors with which a large brake torque can be
obtained. Because electromagnetic brakes
have no holding power, they are used in
combination with mechanical brakes to prevent
dropping of the vertical axis.
ELECTROMAGNETIC BRAKE
This function is supplied on motors with
electromagnetic brakes. Electromagnetic
brakes are used to prevent slipping during
power failures and faults when driving a
vertical axis, or as a protective function when
the machine is stopped.
These brakes are activated when not excited.
EMERGENCY STOP
Emergency stops cannot be carried out by the
AD75, so a method of shutting OFF the servo
side power supply from outside the PLC, etc.,
must be considered.
Summary of Contents for A1SD75M1
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Page 27: ...1 5 MELSEC A 1 PRODUCT OUTLINE MEMO...
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Page 52: ...2 10 MELSEC A 2 SYSTEM CONFIGURATION MEMO...
Page 111: ...5 21 MELSEC A 5 DATA USED FOR POSITIONING CONTROL MEMO...
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Page 332: ...7 18 MELSEC A 7 MEMORY CONFIGURATION AND DATA PROCESS MEMO...
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Page 422: ...9 64 MELSEC A 9 MAIN POSITIONING CONTROL MEMO...
Page 446: ...10 24 MELSEC A 10 ADVANCED POSITIONING CONTROL MEMO...
Page 472: ...11 26 MELSEC A 11 MANUAL CONTROL MEMO...
Page 576: ...12 104 MELSEC A 12 CONTROL AUXILIARY FUNCTIONS MEMO...
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