# Some errors when using GlobalPlanner

I used navfn / NavfnROS as a global planner, it can correctly plan the path from the starting point to the target. But it seems that it does not support the A * algorithm.

So I used global_planner / GlobalPlanner instead. When I use the default parameters, it can complete the path planning correctly as navfn / NavfnROS; when I set use_dijkstra: false, although the robot can finally reach the target point, the following error will be displayed during this process:

[ERROR] [1587748810.128568179]: NO PATH!
[ERROR] [1587748810.128656787]: Failed to get a plan from potential when a legal potential was found. This shouldn't happen.


It seems that these errors did not affect the path planning, but I want to know why these errors occur.

Has anyone else encountered the same problem?

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I had the same issue with A* making NO PATH, but after tuning global costmap inflation radius and cost scaling factor (decreased the inflation radius and increased scaling factor so that global costmap doesn't show too wide cost around obstacle), the error seems to be gone. Compared to the potential map I was getting when the error was there, I can see the potential map is generated in a more reasonable way. (connecting the start and goal position and not covering the whole map!) This is just another option you can try if you are having the same error.

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I believe there are bugs with the "precise start" mechanism. Try setting old_navfn_behavior to true

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