Question:
How can an absolute-value encoder be evaluated for 'Table positioning' in the 8400 HighLine?
Answer:
For the 8400 HighLine with the 'Table positioning' application (C0005 = 2000), an HTL incremental encoder at DI1/DI2 or DI6/DI7 is used for the position feedback for the position control circuit. Position control via other feedback systems at the device terminals is not planned.
An absolute-value encoder connected via the CAN interface (
LP_CanInx) can be evaluated by means of the 'Set home position' function and a corresponding interconnection. For this, the actual position value which is cyclically generated via the HTL incremental encoder is overwritten or initialised at defined times with the position value read in from the absolute-value encoder. By adapting the actual position value, the absolute-value encoder becomes effective for the positioning process.
By setting
LA_TabPos.bHomeSetPosition, the 'Set home position' function and, accordingly, the update of the actual position value, can be executed once or cyclically. Thus, homing to the absolute-value encoder value can be started directly after mains switching (initialisation) or even during axis operation. Then, the absolute-value encoder is used for position correction during operation.
As soon as a positioning profile is started in the 'absolute' positioning mode (
LA_TabPos.bPosExecute) the position correction is accepted in the profile calculation. During a running positioning process, the corrected position can also be accepted by repeating the start command. The acceptance action is automatically executed when changing over to a following profile in the 'absolute' positining mode.
The correction does not affect positionings executed in the 'relative' positioning mode.
Below, you can see the most important configuration assignments for the cyclic correction of the actual position value and/or the initialisation of the actual position value via an absolute-value encoder on the machine. The configuration is based on the 'Table positioning' application (C0005 = 2000). The illustration shows the most important assignments at the function block 'LA_TabPos' in the I/O interconnection layer and in the application interconnection layer.
