Fix Ackermann plugin zero linVel turningRadius bug

[bperseghetti]

🦟 Bug fix

Fixes #1848

Summary

Fix for handling Ackermann wheel steering angle bug where wheel always points same direction when linVel is zero and abs(angVel) > 0.001. This results in an always positive evaluated turningRadius. This solution fixes it by handling linVel zero properly. Allowing it to get past the first conditional that it is otherwise stuck on.

Now the wheels can rotate both directions when the vehicle has no linVel:

FixedAckermannPluginBug.mp4

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #1849 (50ab0ab) into ign-gazebo6 (68008d2) will increase coverage by 0.00%.
The diff coverage is 71.42%.

❗ Current head 50ab0ab differs from pull request most recent head efb3b5a. Consider uploading reports for the commit efb3b5a to get more accurate results

@@             Coverage Diff              @@
##           ign-gazebo6    #1849   +/-   ##
============================================
  Coverage        64.80%   64.80%           
============================================
  Files              322      322           
  Lines            26389    26392    +3     
============================================
+ Hits             17101    17103    +2     
- Misses            9288     9289    +1     

Impacted Files	Coverage Δ
...rc/systems/ackermann_steering/AckermannSteering.cc	85.50% <71.42%> (-0.17%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[jennuine]

LGTM, left a minor comment

[bperseghetti]

@jennuine did a quick test and seems to work fine.

[jennuine]

We need to wait for CI before this can be merged and a new release made. If I can't get to it tonight, it will be finished tomorrow

[bperseghetti]

We need to wait for CI before this can be merged and a new release made. If I can't get to it tonight, it will be finished tomorrow

Thanks @jennuine! Really appreciate it!

[bperseghetti]

@ahcorde @jennuine @mjcarroll thank you all for the expediency on getting this bug fixed, does anyone know when the next forward port to gz-sim7? looks like the last was: #1832. Also I think that there has not been a new point release for garden in a while (39520a1), looks like the motor plugin update wasn't included as well in last point release: #1794.

[mjcarroll]

I'm going to try to get a forward port and point release out today for you.