question

Het avatar image
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Het asked Jeanette F commented

Time based Forklift Transportation to Assign Station

I'm seeking your advice on a couple of issues we're facing in our Flexsim forklift simulation project. Felix M. has advised/assisted us establish Phase 1, to operate timetables and control areas. To Moving into next phase we're facing following challenges.

  1. Inbound Forklift Collisions:
    • When an inbound forklift stops to let another pass, the following forklifts collide with stopped forklift.
    • Can we adjust the speed of the following forklifts or implement a logic to make them stop if another forklift is in their path?
  2. Outbound Forklift Congestion:

    • At 13:45, forklifts returning to their origin locations collide in the corridor, with some turning on the spot if blocked.
    • Can we use any strategies to prevent these collisions and ensure smooth movement?

I have attached the previous question chat history, model, and videos for your reference.

https://answers.flexsim.com/questions/171210/transporter-timetable-based-travel-to-assign-stati.html

Forklift V11 - Control Area Test- New Forklifts.fsm

Inbound:


Outbound:


FlexSim 24.2.2
timetablecontrolareaforklift movement
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1 Answer

Felix Möhlmann avatar image
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Felix Möhlmann answered Felix Möhlmann commented

The weird behaviour when leaving the parking positions stems from the allocation logic I suggested only being designed with the transporters travelling to the parking positions. It simply doesn't work properly for the other case.

Idle TEs only occupying a single A* cell and moving ones also only allocating a single 'line' of cells is a fundamental principle in how the A* navigator works. As long as the grid spacing is smaller than the shape, overlaps will always be possible.

You could try to use a proximity agent system to stop one transporter when two get close to each other. With the free form movement it will be difficult to determine which one should wait though (or if stopping is even necessary at all, maybe they just pass each other).

I don't know if I suggested this previously, but if controlling the distance between TEs is important, an AGV network offers far more options than the A* navigator. It doesn't need to span the entire layout. You can build a network in the charging area and change the navigator when the transporters arrive and leave.

forklift-v11-control-area-test-new-forklifts_2.fsm

Though that would still leave the issue of transporters piling up at the entry points of the network, if many of them arrive in quick succession. An idea for that would to implement a "waiting line". (I tested the Waiting Line object from the people module. It doesn't seem to work with non-person task executers.) That would consist of a list with ordered waiting positions. Every transporter would pull the farthest along waiting point and travel there. While it hasn't arrived at the last point, it continues to try to pull 'better' points.


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