The logic of the path planning is:
1) one AGV moving to pick a pallet on collect point1
2) the AGV placing the pallet on a goal queue for a while
3) the AGV picking the pallet again and put it back on collect point1
4) the AGV moving to pick a pallet on collect point 2,3,4,5....
(keep repeating)
I have tried to use 'source' and 'queue' for collect point, and 'queue' for the goal point. However, it didn't work because the pallet on collect point 1 kept increasing and the AGV never moved to collect point 2. Can someone give me some advice to do this?