Eliminated from:
9400 HighLine SW V7.0
Behaviour of the new version?
When the control type has been changed from C2570 = 2 (position control) to C2570 = 1 (angle control), the status 'Reference known' (system variable HM_bHomePosAvailable) is reset.
Description of the problem
After the position control structure has been changed from 'Position controller active' (C2570 = 2) to 'Angle controller active' (C2570 = 1), the status 'Reference known' (system variable HM_bHomePosAvailable) is retained. Because the position encoder source has altered as a result of the change-over, the internal actual position in the drive no longer matches the real machine position.
When does the problem occur?
The behaviour only occurs if the control type is changed from C2570 = 2 (position control) to C2570 = 1 (angle control) when the actual position is being read in from the application via the system input FDB_dnActPosIn_p (C0490 = 4).
Background:
As regards the position control structure, the 'Position controller active' function is to be set in addition so that the external actual position can be used for the position control. When switching to 'Angle controller active', the angle controller is using the actual position of the motor encoder again and ignores the external actual position. Since the motor encoder may take any position at the time of switching, the home position cannot be derived from the motor encoder position. The 'Reference known' status should be reset.
Which products are affectet:
9400 HighLine SW ≤ V5.1
Diagnostics options?
System variable HM_bHomePosAvailable retains its status, although the actual position at system input FDB_dnActPosIn_p has been rendered invalid due to C2570 being changed to 'angle control'.
Short-term measures/recommendations?
When the position control structure is changed from 'Position controller active' to 'Angle controller active', the home position must be reset manually (e.g. via HM_bResetHomePos = TRUE).
Evaluation:
Generally, only one position actual value is processed, either by the motor encoder or by the position encoder. A change-over between position control and angle control hardly ever takes place when the machine is being operated. At the exact time of switching, the drive does not perform any movements due to the behaviour because a controller inhibit is required. After the controller has been enabled again, a compensating movement is only possible if the positions of the motor encoder and the position encoder were not identical. Following error monitoring limits the movement.
However, since practical operation requires at least one further parameter change in C0490, and since such a change will reset the status 'Reference known', in reality the home position will always have to be recalculated following reparameterisation anyway.
Published with Service Message No. 38/2009
