Reading The Absolute Position With Communication - Delta ASDA-A3 Series User Manual

Absolute System

10.3.5.2 Reading the absolute position with communication

You can access the data of the absolute encoder through two communication methods:
instant access or parameter access. Instant access refers to reading the motor's feedback
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position as soon as power is supplied to the servo. When you set the status monitoring register 1
to the motor's feedback pulse number (P0.017 = 0), you can access the motor's current position
by reading P0.009. Parameter access means the motor's position is temporarily stored in
parameters. Once you set P0.049 with communication, the encoder status and motor absolute
position (cycle number), and pulse number (or PUU) are stored in P0.050, P0.051, and P0.052
respectively. You can choose to read the pulse number or PUU through P2.070 Bit 1. When P0.049
is set to 1, the drive does not clear the error when reading the position value. If P0.049 is set to 2,
the drive clears the error at the same time when reading the position value. Even when the motor is
stopped, it still moves slightly forward and backward for position correction which is normal for the
servo system. To avoid difference between the read coordinates and the actual positioning of the
motor, set to clear the position error at the same time when reading the coordinates, so the motor's
actual positioning is changed to the read coordinates, which clears the position error. For example,
the motor's current position is 20000, but it varies between 19999 and 20001. If you send the
command to read the motor's position when it stops at 20001, then the motor's position is updated
to 20001. After all positions are updated in P0.050 - P0.052, P0.049 is automatically reset to 0.
At that point, the controller can access the values of P0.050 - P0.052. P0.050 shows the status of
the absolute encoder. When it shows absolute position lost or cycle number overflow, that indicates
the read absolute position is invalid. You must re-establish the absolute origin coordinates.
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Start
Set P0.049 to 1 or 2
No
Set P0.049
to 0
Yes
Read
P0.050 - P0.052
Stop
ASDA-A3