Yaskawa MP930 - Manual (Page 245)

Absolute Position Detection
7.3.2 Infinite Length Mode Axis
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7.3.2 Infinite Length Mode Axis
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Description
Infinite Length Positioning is a function that automatically updates machine position, program
position (absolute values in a program coordinate system), and current values at regular inter-
vals according to fixed parameter settings. The function can be used for repeated positioning
in one direction.
POSMAX
0
Unfortunately, the maximum number of rotations from the encoder zero point is ¦99999 rota-
tions at which point it is reset to 0. When system power is turned ON therefore, the MP930
position may not be the same before and after power is turned ON.
This problem can be resolved using the following method.
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Position Control for an Infinite Length Mode Axis
Determine the MP930 position when power is turned ON and use the following equation to
determine the pulse unit position from the relative encoder position.
Always save the pulse position and encoder position as paired data in memory backed up by
battery power. This data is used as pulse position and encoder position at power ON settings
the next time power is turned ON in order to determine number of pulses from the relative en-
coder position using the following equation.
Pulse position = pulse position at power OFF + (encoder position − encoder position at power OFF)
*
* Indicates the distance traveled while power is OFF (relative encoder position).
The following explains the terminology used here.
S Encoder position: Position data for an absolute encoder
(Multi-turn data × the number of encoder pulses + initial increment)
S Pulse position: MP930 position data converted to pulses.
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