Which products are concerned?
Library module L_MCProfileGenerator, included in the Software Package as of V3.3
Problem description:
The drive reverses after a profile change although the target position can be reached with the set profile parameters without reversing. First, the drive continues travelling and constantly decelerates until reaching the speed zero, then it reverses to approach the target position with the new profile parameters.
When does the problem occur?
The behaviour occurs when using jerk-reduced profiles in the S-profile optimised mode (wSProfileMode=1).
In addition, a profile change has to occur in the deceleration phase of a profile. The distance thus to be travelled, resulting from the current position and the new target position, has to be slightly smaller or greater than the braking distance to the original target position. This can already be the case when the same profile is restarted in the deceleration phase.
When the acceleration and the jerk time of the new profile are very great, the behaviour can also occur for greater deviations between the distance and the braking distance.
Possible diagnostics?
The behaviour can be produced by changing to the same profile in the deceleration phase. The speed setpoint oscillograph of the profile generator shows that deceleration is not reduced as expected, but that the drive continues travelling with constant deceleration until reaching speed zero. Then it reverses. Without the restriction, the motion would be the same as without a profile change.
Short-term measures/recommendations?
None
Evaluation
Normally, the profile parameters are considerably changed at a profile change. Therewith, the behaviour doesn't occur. The target is reached in any case, the motion remains controlled. The drive covers slightly more distance than required.
