Mitsubishi Electric MELSEC-L LD75D, User Manual

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APPENDICES
A
Appendix
8
ME
LSE
C
E
xplanat
ion
of
Pos
itioning T
e
rm
s
Appendix 8
MELSEC Explanation of Positioning Terms
Term Description
1-2 PHASE EXCITATION SYSTEM
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.
MOVEMENT AMOUNT PER PULSE
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.
2-PHASE 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.
Pulse input
A phase
A phase
B phase
B phase
Movement amount per pulse =
P rate
×
Movement amount
per rotation
No. of pulses per
encoder rotation
Amount the motor moves (travel) per pulse.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
90
°
A phase
B phase
Pulse count Forward run
(addition)
Reverse run
(subtraction)