Yaskawa MP940 - Manual (Page 328)

Absolute Position Detection
7.3.1 Finite Length Mode Axis
7-14
7.3 Using an Absolute Encoder
This section describes precautions regarding use as well as the procedure for setting the zero
point when using an absolute encoder.
7.3.1 Finite Length Mode Axis
„ Overview
An absolute encoder stores the number of rotations from the encoder zero point in internal
memory backed up by battery. Therefore, the zero point of the coordinate system can be
determined without returning to the zero point when the system is started up. Once the sys-
tem is started, the encoder functions just like an incremental encoder.
Unfortunately, if the number of rotations from the encoder zero point goes out of the range
from –32768 to +32767 rotations, it is reset to 0. When system power is turned ON there-
fore, the MP940 position may not be the same before and after power is turned ON.
A Finite Length Mode Axis has only limited movement that falls within the range of –32768
to +32767 absolute encoder rotations.
Therefore be sure to note the following precautions when using an absolute encoder as a
Finite Length Mode Axis.
• Be sure to initialize the encoder prior to setting the zero point.
• Use an absolute encoder only within the range of –32768 to +32767 rotations.
Note: The actual machine operating range may vary depending on parame-
ters like the gear ratio.
• Do not change the Zero Point Position Offset (OLC006) while operating in Finite Length Mode.
Otherwise this may cause machine damage or an accident.
Caution
0
Reverse limit Forward limit
Reverse
direction Zero
point
Forward
direction
(-32768 rotations) (+32768 rotations)