Ackermann Steering Plugin

[knoedler]

Summary

This adds an Ackermann Steering Plugin based on the differential drive plugin.

The plugin accepts a linear velocity (x) and a rotational velocity (z) the same as the differential drive plugin and sets the vehicle drive and steering joints to achieve the requested inputs. The plugin and integration tests are largely based on the differential drive plugin.

Items to consider:
SpeedLimiter.cc and SpeedLimiter.hh are identical copies from the diff_drive plugin
Odometry is not as accurate as a pure diff_drive robot. I had to open the integration tests limit up from 1cm to 25cm when comparing odometry to ground truth in the integration tests. I tried various ground friction coefficients and using the wheel
slip plugin, but I did not achieve 1cm accuracy for the odometry.
There is a lot of commonality between the differential and Ackermann plugins. It might make sense to merge them at some point in the future when the Ackermann plugin has aged a bit and is stable (to minimize risk to the heavily used diff drive plugin).
I was not able to generate a coverage report.

Test it

The plugin can be tested using examples/worlds/ackermann_steering.sdf

Checklist

• Signed all commits for DCO
• Added tests
• Added example world and/or tutorial
• Updated documentation (as needed)
• [NA] Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• [?] While waiting for a review on your PR, please help review

[ahcorde]

@osrf-jenkins retest this please

[chapulina]

This is looking good to me! I didn't check the math too closely though. I took a quick look at the implementation on gazebo_ros_pkgs but the approach looks a bit different.

[chapulina]

I think this can be moved to a common place so multiple plugins reuse it, see gazebosim/gz-math#194. We shouldn't block this PR for this, we can come back later and update this plugin and diff drive once the version on ign-math is released.

[ahcorde]

Remember to sign all your commits. DCO is failing

[knoedler]

Remember to sign all your commits. DCO is failing

That particular commit was from clicking on "commit suggestion". I would have expected github to handle signoffs. I have made a couple of attempts to resolve it, but my googling has not found a successful way to resolve it.

I believe I have addressed the issues from the two reviews.

[chapulina]

I would have expected github to handle signoffs.

Yeah unfortunately GitHub doesn't make it easy to sign commits from the web UI. We've been manually adding the signature for those cases.

One way of solving this would be by adding the signature locally while rebasing and then force-pushing. If this is too much trouble, we can manually accept the DCO check since all other commits are properly signed.

[knoedler]

One way of solving this would be by adding the signature locally while rebasing and then force-pushing. If this is too much trouble, we can manually accept the DCO check since all other commits are properly signed.

If you could, please manually accept the DCO check.

Adding the signature locally/rebasing/force-pushing was one of the approaches I tried a couple of different ways, but it didn't work for me in this case.

[chapulina]

Thank you for the new plugin!