Positioning method type The Basics of Positioning Control
FX Positioning Control Systems 1 - 9
1.3.2 Position control
Pulse command method
An AC servo motor which rotates in proportion to the input pulse number is used as the drive motor.
When the pulse number corresponding to the movement distance is input to the servo amplifier of
the AC servo motor, positioning can be performed at high speed in proportion to the pulse frequency.
– Guideline of stopping precision: Approximately ±0.01 to 0.05 mm
(The stop precision shows a value in a case where the low speed is 10 to 100 mm/s.)
Using the pulse command method with a servo amplifier, the weak points described above for speed
control are improved. A pulse encoder is attached to the servo motor to detect the motor rotation
quantity (workpiece movement distance) and feed the information directly to the servo amplifier in
order to continuously and directly control the high-speed positioning operation to the target
position. This method allows the workpiece to stop with better precision and eliminates the coasting
and dispersion distance at stop. Furthermore, limit switches to stop normal positioning operations,
along with counting methods from the PLC are not needed.
1200a0da.eps
Fig. 1-13:
Schematic drawing – Pulse command method
PLG SM
Moving part
Ball screw
Pulse generator
Servo motor
Position controller
Pulses are fed
back
PLC
Programmable
controller
Movement distance
Servo
amplifier
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