Which products are affected?
Software Package Positioner V3.1
Positioner template
What happens?
After a program download the g_bHomePositionAvailable variable signals that the home position is known. However, the current position g_dnActualPositionReal differs from the position before the program download although the axis has not moved.
When does the problem occur?
The problem occurs if C3002 = 1 and if another program has been downloaded to the PLC.
The current position is only saved in retain mode (protected against mains failure) and not persistently (protected against mains failure + resistant if another program is downloaded).
However, g_bHomePositionAvailable signal is saved persistently.
If C3002 = 1 (NoChangeOfPos) is set it is specified that the machine position does not change at all or only slightly while the control board is not supplied. Due to this precondition a resolver can be evaluated as absolute feedback system.
Possible diagnostics?
If the current position g_dnActualPositionReal is remembered under the condition that the home position is known and C3002=1 and if a new program is downloaded now the position display has changed considerably afterwards. Compared to e. g. 3.25 revolutions the value indicated after the download amounts to 0.25 revolutions only. This means that only the current position information of the resolver is always indicated. There is no set-off with a saved value. The resolver can only indicate one revolution absolutely.
Short-term measures/recommendations?
The axis must be referenced again after a program download.
Evaluation:
The main function to evaluate a resolver as absolute feedback system after mains connection is given. The restriction only occurs when a program is downloaded, i.e. during commissioning or servicing but not while the system is running. Damages to the machine can rather be excluded.
