Add footprint clearing for static layer

[tonynajjar]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#4277
Primary OS tested on	Ubuntu
Robotic platform tested on	custom gazebo simulation
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

• I added footprint clearing to static layer similarly to obstacle_layer

Description of documentation updates required from your changes

• Document new parameter

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Future work that may be required in bullet points

• Adding parameter to more layers

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 89.84%. Comparing base (9f6b0dd) to head (c9ff549).

Files	Patch %	Lines
nav2_costmap_2d/plugins/static_layer.cpp	60.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4282      +/-   ##
==========================================
+ Coverage   89.64%   89.84%   +0.20%     
==========================================
  Files         433      433              
  Lines       19728    19738      +10     
==========================================
+ Hits        17685    17734      +49     
+ Misses       2043     2004      -39     

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[tonynajjar]

I have the problem in the first picture in the description that SMAC complains when I send a goal straight ahead to try and get out: GridBased plugin failed to plan from (-3.86, -4.61) to (-3.59, -4.57): "Start occupied" although it's visually not

However when I add some clearing padding it works

This is pretty much independent from this PR though as it happens when close enough to any lethal obstacle. I do think that a default mini-padding to the clearing footprint would be useful to get unblocked, what do you think?

[tonynajjar]

Okay, what do you think about adding a small padding to the footprint clearing? Maybe as a parameter as well?

[SteveMacenski]

However when I add some clearing padding it works

I think its wise to understand why that's happening and if that's the right solution. But if we know why and this is the right solution, I don't have a problem with it. If the check for start in collision is returning "yes" when its not, that's eye brow raising

[tonynajjar]

I found another small bug but I can't really find the cause, maybe you have an idea. I found that the static layer occasionally flickers, i.e. without moving the footprint, the static layer sometimes "unclears". It happens about once every 10-20 seconds and lasts less than a second, if that tells you anything.

I have a small hunch that this flickering is happening more often than is being visible in rviz and that is actually causing the issue: GridBased plugin failed to plan from (-3.86, -4.61) to (-3.59, -4.57): "Start occupied" because sometimes it's also the controller that complains of collision. (the static layer is in both local and global planner)

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[tonynajjar]

Update: I figured out where the flickering came from. It was because of the conversation we had here. Turns out it has to be before the chunk where the costs are updated. I don't know why for sure but it's like that in obstacle, voxel and stvl layers.

However, this was not the cause of "Start occupied", this still occurs and I'm not sure why. It seems to be related to how tight it is thought because adding some padding fixes it. Since it's a SMAC issue, I would not block this PR for it. Are we okay to merge this and write an issue for SMAC?