Specifications

App - 37
D
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.
Command
pulses
Motor
PLG Encode
r
Feedback pulses
Deviation
counter
D/A
converter
DIFFERENTIAL OUTPUT TYPE
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 transfe
r
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
Driver
Servo amplifier
Receiver
DRIVE UNIT
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.
Power supply
Motor
Positioning
module
Drive unit
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 powe
r
is OFF, or during faults, etc.
DROOP PULSE
Because of inertia (GD
2
) on machines, if a speed
command is simply issued without an
y
time-consideration, a positioning module will fail to
follow the command in time.
To solve this, servomotors employ a method in
which the speed command pulses are first
accumulated in a deviation counter before sent.
This way, the pulses are successfully delayed.
These accumulated pulses are called the droop
pulse.
The deviation counter emits all pulses and returns
to 0 when the machine stops.
Voltage
200 pulses
accumulate
in the counter
D/A
1,000
pulses
800
pulses
DYNAMIC
BRAKE
When protection circuits operate due to powe
r
failures, emergency stops (EMG signal), etc., this
brake is used to short-circuit between servomoto
r
terminals via a resistor, make the motor consume
rotation energy, and stop the motor suddenl
y
without allowing coasting of the motor.
Braking torque is provided 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.
E
ELECTRONIC GEAR
This function electrically increases/decreases the
command pulses from the pulse command module
by 1/50 to 50-fold. Thus, the positioning speed and
movement amount can be controlled by the
electronic gear ratio magnification.