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Appendix - 74
MELSEC-Q
APPENDICES
DECELERATION TIME
The parameter deceleration time is the same
value as the acceleration time. Deceleration
time refers to the time from the speed limit
value to a stopped state, so it becomes
proportionally shorter as the setting speed
decreases.
Speed limit value
Setting speed
Speed 0
Deceleration time
Time
DEVIATION COUNTER
Deviation counters have the following two
functions.
1) To count the command pulses issued from
the QD75, 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
DIFFERENTIAL OUTPUT TYPE
This is one type of encoder feedback pulse
output. When one signal is output with this
method, a companion signal having the
reverse polarity is simultaneously output. This
method enables high-frequency transfer, and
is resistant to noise, etc., so it is also used in
high-speed signal transfer such as inputting
and outputting of pulse trains. In general, the
transmission side is called the driver, the
reception side is called the receiver, and a
dedicated IC is used.
Command
device
Servo amplifier
Driver Receiver
DIGITAL BUS CONNECTION
Commands are generally output from the
positioning module to the servo amplifier as a
pulse train. Recently, however, devices are
being digitalized. Accompanying that, a
connection method has appeared in which the
bus lines of both the positioning module and
the servo amplifier CPUs are connected. This
has enabled the construction of higher-
accuracy, higher-speed systems.
The MELSEC A70D, AD774M, A171SCPU,
A273UCPU etc., models employ this digital
bus connection.
DOG SIGNAL
The near-point dog of the OPR.
DRIVE UNIT
The commands output from the positioning
module are low-voltage, low-current
commands with insufficient energy to run the
motor.
The drive unit increases the width of these
commands so the motor can be run. It is an
accessory on servomotors and stepping
motors. Also called a servo amplifier.
Positioning
module
Drive
unit
Motor
Power supply
DRIVE UNIT READY
This signal is output when the drive unit for the
motor is in a READY state.
This signal remains OFF when the drive unit
power is OFF, or during faults, etc.