The advantages of this additional
for position reconstruction after mains switching, especially when operating the i750 or i950 servo inverters under control systems from other manufacturers, such as Beck, for example.
manufacturers, such as Beckhoff.
For the Lenze system
itself, the reconstruction function within the inverter is not absolutely
is not absolutely necessary, as this functionality is already included in the higher-level motion axis in the Lenze Controller.
Background info:
IIn contrast to the i700 servo inverter, a function for position reconstruction is already implemented in the firmware of the i750 and i950.
span style="color:rgb(50, 49, 48);background-color:rgb(255, 255, 255);">When switched on, these device series behave differently in terms of the actual position displayed, which must be taken into account when evaluating them under control systems from other manufacturers.
It makes sense to re-reference the machine, especially after replacing the inverter, because the retain data required for reconstruction is different in the devices, see the following description.
For the position reconstruction in the i750, as well as in the i950 zat the time of switching off the
information required for reconstruction is stored in the device (retain data).
stored in the device (retain data). Saved:
- span style="font-size:11pt;font-family:calibri;">the actual position and
- an internal offset value (not
displayable).
Based on these two values, the corresponding old raw encoder value (modulo value in relation to the encoder display range)
can be calculated back.
When switched on, this old raw value is compared
is compared with the new raw value supplied by the encoder and it is determined whether and in
direction the encoder has been moved.
The actual position is adjusted (reconstructed) accordingly.
adjusted (reconstructed) accordingly.
Principle of the reconstruction in the
device:
- Saved old actual position
Convert to encoder system (remove offset)
- Reduction of the actual position to the
encoder display area (modulo)
- Position difference (new -
old), each within the encoder display area.
- interception of a possibly occurred occurred
overflow in the encoder.
Condition for overflow: amount of difference > half display area
Yes
(with overflow): New
Actual position = old actual position + position difference + display range
No (without overflow): New actual position = old
Actual position + position difference
- Calculate saved offset value
back into the actual position.
By applying this procedure, dthe condition (+/- half the display range) always refers to the encoder position at the switch-off time. It istherefore irrelevant at which position the overflow occurs in the encoder.
overflow takes place in the encoder.
Note:
if a movement of more than +/- half the display range has taken place in the switched-off state, the device cannot detect this!
detectable by the device!
