Yaskawa MP940 Reference Manual - Manual (Page 314)

Absolute Encoder Usage Method MotionSuite™ MP940 Machine Controller Reference Manual
7-20
“Save” operation. Upon turning power ON again, the value of the zero-
point position offset (OLxx06) at “Save” is automatically stored.
When Used as a Rotary Axis
Outline
Rotary positioning is a function in which the current values of the machine
position and program position (absolute value occurring in the program
coordinate system) are periodically and automatically updated according to
the settings in the fixed parameters. Repeated positioning in the same
direction can be executed by the rotary axis positioning function.
Because the rotations from encoder zero-point can only be managed within a
range of rotations of 0 ~ Pn205 (multi-turn limit setting), the number of
rotations can be reset to “0” if the number of rotations exceeds Pn205 (multi-
turn limit setting). The positions managed by the MP940 before and after
power ON differ if the system power is cycled in this state. This problem can
be resolved by the following method.
Position Management when Using a Rotary Axis
At system power ON, the position managed by the MP940 derives the pulse
unit position from the encoder phase position by the following formula.
The pulse position and encoder position are always saved as paired data to
the battery backup memory. At the next power ON, this data is used as the
“Pulse Position at Power OFF” and “Encoder Position at Power OFF”,
respectively, and the pulse unit is derived from the encoder phase position by
the following formula.
Pulse Position = Pulse Position at Power OFF + (Encoder Position - Encoder Position at Power OFF)*
POSMAX
0