Appendix 8 Melsec Explanation Of Positioning Terms - Mitsubishi Electric MELSEC-L LD75P User Manual

Positioning module
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Appendix 8
Term
1-2 PHASE EXCITATION SYSTEM
MOVEMENT AMOUNT PER PULSE
2-PHASE PULSE
MELSEC Explanation of Positioning Terms
This is one system for exciting each stepping motor coil in a determined order. In this system, one phase and two
phases are alternately excited.
Pulse input
A phase
B phase
A phase
B phase
When using mm, inch, or degree units, the movement amount is calculated and output from the machine side
showing how much the motor shaft moves per pulse. Positioning accuracy in smaller units is not possible.
On the motor side, the movement amount per axis rotation is normally designed as a reference, so it is calculated
as follows.
Movement amount per pulse =
P rate
No. of pulses per
×
encoder rotation
Amount the motor moves (travel) per pulse.
An A phase and B phase double pulse. There is a phase difference between the two phases, so that difference
can be automatically added and subtracted in the pulse count. The standard phase difference is a 90 electrical
angle.
If the B phase were to lag behind the A phase in a forward run (B phase turns ON after the A phase), the A phase
would lag behind the B phase in a reverse run (A phase turns ON after the B phase). In this way the forward and
reverse run (addition and subtraction) can be automatically carried out.
90°
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Forward run
(addition)
Description
Movement amount
per rotation
A phase
B phase
Reverse run
Pulse count
(subtraction)
APPENDICES
A
769

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