Eliminated from:
9400 HighLine SW V7.0
Behaviour of the new version?
If the maximum permissible angle of rotation set in C2653 exceeds the display limit of 2^31 – 1 during the internal conversion into increments, the angle of rotation is limited internally to 2^31– 1 [incr.].
If the drive now rotates within the range that can be displayed internally whilst the mains power is switched off, the homing information (HM_bHomePosAvailable = TRUE) is no longer lost following mains switching.
If the drive is rotated outside of the range that can be displayed internally, the homing information is still lost.
Description of the problem
Homing information (HM_bHomePosAvailable = TRUE) is lost following mains switching, although the maximum permissible angle of rotation set in parameter C2653 has been observed.
When does the problem occur?
The behaviour occurs if absolute value encoders are being used and the home position is to be retained after the mains power has been switched off (C2652 = 'Retain'). The maximum permissible angle of rotation when the mains power is switched off (C2653) is set in angular degrees, related to the encoder shaft. This parameter is converted inside the controller into increments in accordance with the 'Resolution of an encoder revolution' (shift factor C0100).
The behaviour arises if a counter overflow (> 2^31 - 1) of the internal display of the angle of rotation occurs when C2653 is being converted from angular degrees into increments.
Which products are affected?
9400 HighLine SW ≤ V5.1
Example calculation:
With a shift factor of C0100 = 24[bits/rev.] and a maximum permissible angle of rotation when the mains power is switched off of C2653 (degrees) = 46,081[°], the incremental value is calculated as follows:
C2653 (incr) = C2653 (degrees) / 360[°] * 2^C0100 = 46,081[°] / 360[°] * 2^24 = 2,147,530,251[incr.]
Since this value is greater than 2^31 – 1[incr.], in this example the home position would be lost.
Diagnostics options?
Following a switch-off of the mains power, calculate the incremental angle of rotation according to the formula below:
C2653 (incr) = C2653 (degrees) / 360[°] * 2^C0100
If this value is greater than 2^31 – 1[incr.], the behaviour may arise.
Short-term measures/recommendations?
Do not set the maximum permissible angle of rotation when mains power is switched off in C2653 to a value any greater than:
C2653(max) = 360 [°] * 2^(31 - C0100) - 1 [°]
Evaluation:
This behaviour can cause homing information to be lost each time mains switching is performed if very high values are set in C2653. You can prevent this from happening by adjusting the maximum permissible angle of rotation in C2653.
In practice, high angles of rotation such as those used in the example calculation above do not occur in a de-energised state, so the action described under Short-term measures/recommendations can be relied upon to eliminate the problem.
Published with Service Message No. 38/2009
