Remove front_steering from steering library

[qinqon]

To Accommodate controllers that are not only steering at front or rear
this change remove the front_steering variable from
steering_controller_library, as a byproduct of that the notion of
front or rear wheel radius is also removed from dependant controllers
and the library has know "traction_joints_names" and
"steering_joints_names" instead of "front_wheels_names" and
"rear_wheels_names".

Depends on:

• Fix steering controllers library kinematics #1150

[christophfroehlich]

I support the idea, thanks!

Please deprecate the old parameters and add the new ones to support both temporarily. Then we can also backport such changes.

Additionally, please add migration notes here.

[christophfroehlich]

Have you read and considered #692? Ideally, we should solve it with this PR.
I'm not sure if your proposal works for 4WD + 4x steering?

[qinqon]

Have you read and considered #692? Ideally, we should solve it with this PR.

The idea is the same, is all about generalize the steering library a little more.

I'm not sure if your proposal works for 4WD + 4x steering?

Next PR will allow that, I am thinking about extending the current ackermann instead of new controller, if you add a pair of traction and steering joints and define the instantaneus center of robot you can have this by modifyting a little the IK and odometry. Also you can keep the current ackermann by configuring the instantaneus centor or robot at the traction joints and using the same IK and odometry.

[mergify]

This pull request is in conflict. Could you fix it @qinqon?

[qinqon]

Tests working

$ colcon test 
Starting >>> steering_controllers_library
Finished <<< steering_controllers_library [0.44s]          
Starting >>> ackermann_steering_controller
Starting >>> bicycle_steering_controller
Starting >>> tricycle_steering_controller                                                                    
Finished <<< bicycle_steering_controller [1.50s]                                                                                                   
Finished <<< ackermann_steering_controller [1.58s]                                                            
Finished <<< tricycle_steering_controller [1.52s]

Summary: 4 packages finished [3.01s]

[Juliaj]

Typo, wheels_preceeding -> wheels_preceding. There are more instances of this typo in the current file ...

Shall we just use joints_preceding_names_ for consistency ?

[christophfroehlich]

Good catch, fixed that in a separate PR and will merge that in here later. But we have wheels_preceeding_names_ and steers_preceeding_names_, joints do not work then?

[Juliaj]

One option is to rename wheels_preceding_names_ to traction_joints_preceding_names_, and steers_preceding_names_ to steering_joints_preceding_names_. There is a variable named preceding_joint_names_ which doesn't seem to be used anywhere.

[christophfroehlich]

done. please have a look

[christophfroehlich]

I just had a hard time updating ros-controls/gz_ros2_control#566, because I misspelled a parameter.
traction_wheels_track instead of traction_wheel_track (due to the similarity to traction_wheels_radius). I propose renaming it to track_width instead.

[mergify]

This pull request is in conflict. Could you fix it @qinqon?

[Juliaj]

LGTM. Thanks for all the work and efforts to get this in.