find path possible

slyderkiller · Oct 29, 2013

Hello,

I have to develop a program to automatically select the best possible path

To go from one place A to B, I have several solutions, I'd like to select the quickest path but also have the opportunity to select a different path.

Know a Algorithm which allows to find the path possible in a table?

The PLC is not determined.

My project is in the transport of grain so I can be several paths according elevators, chain transporters, two-way box ect ...

Thank you for your help

shooter · Oct 29, 2013

it is not the quickest path you need, but the best path, if using more types of grain.
same as trainswitches

PeterW · Oct 29, 2013

I've seen this at airports where paths are created and changed mid-route if conditions warrant it.

The way it was done there was at every decision point before a divert mechanism every destination was given a weighting which governed the decision. If a section of conveyor was in fault, this would effect the weighting at every decision point to route bags away from the faulted area.

All this decision making was actually done in a PC, the PLC just passed destination information and the PC sent back the direction to take.

chud · Oct 30, 2013

Sounds like a job for SFC programming

slyderkiller · Oct 30, 2013

Yes indeed the best way because depending on the type of grain storage is unlike.
Do you think it is better record every path possible in the PLC or path possible of each conveyor and calculate the path with Algorithm as "Dijkstra" or "A *" if possible.
I think doing the processing in the PC only if I am forced.

jamesau · Oct 30, 2013

slyderkiller said:
Do you think it is better record every path possible in the PLC or path possible of each conveyor and calculate the path with Algorithm as "Dijkstra" or "A *" if possible.

It depends on the scale and complexity of your network (you haven't provided details in this regard). Are multiple, concurrent transfers allowable? Is it typical for there to be multiple paths allowable between any two source/destination pairs?

Also, what's "A *"?

slyderkiller · Oct 30, 2013

yes there are more eligible between two pairs of source / destination paths.
There are about 3 to 5 possible paths to the same Local resort and interactions between the paths.

For A*
http://en.wikipedia.org/wiki/A*_search_algorithm

excuse me for my bad English

shooter · Oct 31, 2013

yes the dijkstra is a simple to do algorithm in a PLC, however you will have to take care of flows already running. dijkstra only has one flow and no busy knots.
i would keep it simple and use the lowest in rang available. so follow dijkstra but have the knots a dimension, and yes give us a drawing.

Peter Nachtwey · Oct 31, 2013

I wouldn't do this in a PLC. I think you can see it would consume a lot of computing time. I would use a PC and down load the solution to the PLC.
The must be a lot of code written to do this for games.
If there are a lot of common nodes in the search path then use a hash table to save the results of the search that was done before.

slyderkiller · Nov 1, 2013

In fact I have to pay attention to circuits used. there are several common equipment circuits.
I will continue my search for an Algorithm that takes into account my constraints.

I think indeed that I'll do the monitoring PC to facilitate the work.

I will hold you in my current research and results.

Thank you to you

jamesau · Nov 1, 2013

Long ago I had an interest in this subject. The paper, http://www.sciencedirect.com/science/article/pii/0098135495002243, outlines an approach that might interest you. To summarize, one represents their process flowsheet as a directed graph (with nodes as valves and arcs as pipe sections, for example). A label-setting shortest path algorithm is used to identify desired flow paths. By presetting inadmissible nodes of the digraph as labeled prior to the search, those nodes are not included in the search space for flow path determination. Additionally, once the flow path is identified, neighboring nodes are then identified to isolate the path to prevent disruption / cross-contamination of the desired material transfer. By presetting labels of these nodes, other non-interfering concurrent transfers can be identified.
Slyderkiller, if you review the above paper and believe its approach suits your application, I can make the code available that demonstrates the important features of the paper. First however, you would have to paraphrase the general structure of the algorithm as given on page 1084 of the Problem Specification section; do this in a Private Message to me. Know also that it would be no small task to integrate this approach into a ruggedized, real-world application.

Peter Nachtwey · Nov 2, 2013

I hate pulling teeth

I broke my wrist and don't feel like typing much.

How many combinations of paths do you think there are?

If there are less than 100 it would probably be fastest to work them out in your head and put the data in a table that is indexed by source and destination. If there are multiple paths I would list the the paths for each source and destination in order of how good they are.

I have a shortest path program I saved from the 1990s when I programmed in turbo C it is more of a program for games than a series of nodes where there are terrain costs etc. The program isn't that big.

shawn_75 · Nov 4, 2013

Watch this video. Specifically the part about UPS deliveries.

http://video.pbs.org/video/2365099550/

find path possible

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