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jfoster avatar image
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jfoster asked Felix Möhlmann answered

AMR: astar vs agv

Hello,

I've been familiarizing myself with the model presented in the dev talk by @anthony.johnson, and I understand this ok. I also downloaded the Kiva System Demo Model uploaded by @Markus Cueva. I am wondering what the pros and cons are of using AStar vs AGV for AMR modeling. Here is a list of things that I need to do:

  • Routing:
    • Modify how often a route is calculated, once at beginning or after every move or somewhere in between
    • Add costs to each and every edge on the navigation grid: example cost 10 to go down, 1 to go up, thus preferred path is up.
    • Allow routing certain paths/node types depending on whether a vehicle has a load or not
    • Add extra costs for certain vehicle activities for example: turning
    • Zones for different vehicles, with some shared nodes. Vehicle 1 can traverse node 1 and 2 but not node 3, vehicle 2 can traverse 2 and 3 but not node 1.
    • Add waypoints that the vehicle must traverse through or stop to do something when going to certain destinations
    • Gridlock resolution, detect gridlocks and allow user to resolve by rerouting or modifying grid
  • Vehicle control:
    • Modify speed of vehicle when reversing vs driving forward
    • For pallet to picker applications, force the vehicle to reverse into specific locations and drive forward after leaving
    • For shelf to picker applications, force the vehicle to drive forward into location and then do a 180 underneath the shelf to drive forward out of the pick location
    • Charging and charging strategies such as opportunity charging, or charge after reaching x threshold
    • Bin to picker applications that support crane type vehicles and their interactions with tote moving vehicles
  • Grid:
    • Allow non-uniform grid spacing
    • Collision avoidance
    • If two nodes on a grid are close together such that one vehicle would block two nodes, then do not allow another vehicle on either node

FlexSim 25.0.0
agvastarroutingamr
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1 Answer

Felix Möhlmann avatar image
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Felix Möhlmann answered

I see a couple of things that are definitely not possible with the A* system in your requirements:

- Different costs per edge
- Different speed when reversing (there isn't really a "reverse" in the A* system. Either the traveller rotates to the travel direction or it does not)
- Non-uniform grid-spacing
- Customized blocking of additional nodes based on vehicle size.

The AGV-system also has multiple bullet points that it can't do by default. But the Customization Delegate can be used to intregate requirements such as cost dependend on travel direction.

Gridlock resolution can be quite complicated though and for allocating multiple nodes based on vehicle size it will be tricky to find which nodes those are and the allocation timing (if the grid is non-uniform).

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