Convergence criteria of "Conveyor tracking".

Hi all.

Anyone know the convergence criteria of "Conveyor tracking"? I mean how Robot decides that it reaches the programmed position (object moving on conveyor).

My machine uses IrB1200 with option "Conveyor tracking" to pick products on conveyor.

-Normal case: Robot runs after product for a short distance-> catches up with product -> moves down -> turns vacuum On -> complete

- Abnormal case: Sometimes Robot runs after product for a very long distance although visually I see Robot absolutely CATCHES UP WITH product (Robot is right above the product). Then robot moves beyond the limited area and raises machine error.

The vacuum sensor works well.

Please give me some advices, thank you.