Is it possible to control specific nodes in A star navigator?

[rhramac]

[ FlexSim 21.2.4 ]

I am modeling a bot takes 90 degree turns. I am exploring A star implementation but the bot has an overhang and which means I will need block of adjacent nodes in the Astar network. Is that possible in flexsim A star implementation or am I better doing this with AGV or travel network nodes?

[moehlmann_fe · Accepted solution]

I think in theory you could add dynamic barriers for each node and toggle them depending on traveller vicinity. Though every traveller would have to constantly recalculate their route to account for the changing barriers which would make the model run slow.

Another option would be to change the grid spacing to match the robot size, though this might not be possible if the spacing needs to the finer to reach all locations.

I remember that this topic (travellers blocking more than one node) was brought up before and the developer's response was that they are considering it.

For now, if resizing the grid spacing is not an option, using another travel method is probably the better choice.

[rhramac]

Thanks for the response. What are the other viable travel methods? I am trying to navigate on a grid like floor storage from one cell to another.

[moehlmann_fe]

It sounds like you want to model something like this:

https://www.autostoresystem.com/

One idea could be to use A* with mandatory paths that are spaced out so the robots can pass each other when travelling to the target cell. They would then only 'step out' to arrive at the final target for a short time minimizing the time where collisions could occur. This wouldn't exactly replicate the system but might be 'close enough'.

Other than that, I think building a custom path finding logic is your best bet. I actually built a prototype model for this purpose some time ago, that used a separate implementation of the A* algorithm to allow for different x- and y-dimensions of the grid cells (which wasn't possible at the time).

There are lots of resources about the algorithm online, since it's a popular example in IT studies.

[rhramac]

Thank you for the response, is there any examples of custom path logic implementation in Flexsim using A star in this forum? I am looking for a starting point.

[moehlmann_fe]

Here's a long discussion about improving FlexSim's capabilites to model autonomous transport robots. Joerg Vogel's comment under the main post and the linked answer/model might be of interest to you.

https://answers.flexsim.com/questions/116755/modeling-amrs-using-agv-paths-or-using-a-can-you-f.html

Anthony Johnson also built a KIVA model last year. It doesn't really help with the blocking of A* nodes, but maybe you find some useful approach in there.

https://answers.flexsim.com/articles/107103/example-kiva-system-model.html

I'll have to talk to my boss about whether I can send you the prototype model I mentioned above. That'll have to wait until next monday though.

[rhramac]

super helpful! Much appreciated!