Proposal for refactored steering and 6 wheeler steering.

[silanus23]

I would like to contribute on #1243 and have moved forward with the first step: documentation and a rough implementation roadmap.

Kinematics: Adapted from NASA’s jpl-osr-rover-code, matching the 6×4 rocker-bogie configuration (steerable front/rear pairs, fixed center).

Testing: Planning to use that repo as a simulation testbed. It targets Jazzy but can be updated for Rolling easily.

Docs: Added a section explaining the kinematic model and its relevance. Intended as groundwork for the proposed steering_controllers_library refactor.

Issue thread has been inactive, so this PR follows the direction mentioned earlier—starting with documentation. Feedback is welcome to move this forward efficiently.

@christophfroehlich

[Copilot]

Pull Request Overview

This PR proposes a refactored, plugin-based architecture for steering controllers in ROS 2 control, specifically targeting support for six-wheel rovers with four-wheel steering. The proposal aims to address extensibility limitations in the current monolithic steering controller design by introducing a kinematics-agnostic controller that uses pluginlib for different vehicle models.

• Plugin-based architecture separating generic control logic from kinematic models
• Documentation for six-wheel steering kinematics based on Ackermann principles
• Additive implementation approach to avoid disrupting existing controllers

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

File	Description
steering_controllers_library/doc/refactored_steering_library.rst	Proposes new GenericSteeringController with pluginlib-based kinematic models
doc/six_wheeler_steering_controller.rst	Documents six-wheel steering kinematics, parameters, and configuration
doc/images/six_wheeler_steering.drawio	Provides kinematic diagram for six-wheel rover visualization

[christophfroehlich]

I would like to contribute on #1243 and have moved forward with the first step: documentation and a rough implementation roadmap.

Kinematics: Adapted from NASA’s jpl-osr-rover-code, matching the 6×4 rocker-bogie configuration (steerable front/rear pairs, fixed center).

Testing: Planning to use that repo as a simulation testbed. It targets Jazzy but can be updated for Rolling easily.

Docs: Added a section explaining the kinematic model and its relevance. Intended as groundwork for the proposed steering_controllers_library refactor.

Issue thread has been inactive, so this PR follows the direction mentioned earlier—starting with documentation. Feedback is welcome to move this forward efficiently.

@christophfroehlich

Thanks for picking this topic.

Please post your proposal in the issue or open an issue in the roadmap repository instead of adding a new file to the repo.

About the naming: From six_wheel_steering_controller I would expect that all 6 wheels are steerable. Do you have another naming suggestion?

[silanus23]

Thanks for the clarification.
I assumed the proposal docs belonged here, but I’ll move the design part to the roadmap repo and link it from here.
For the name: I agree, six_wheel_steering_controller could be misleading. Would four_wheel_steering_rover_controller or six_wheel_rover_controller or 6x4_wheeler_controller work better in your view?

Let me know if you'd prefer this PR to be closed, or kept as a draft reference until implementation starts.

[christophfroehlich]

I agree, six_wheel_steering_controller could be misleading. Would four_wheel_steering_rover_controller or six_wheel_rover_controller or 6x4_wheeler_controller work better in your view?

6x4 is not working as ROS package name: https://ros.org/reps/rep-0144.html

only consist of lowercase alphanumerics and _ separators and start with an alphabetic character.

better using something that will work. six_times_four_wheeler also does not seem to be very nice, so maybe six_wheel_rover would be the best option.

Let me know if you'd prefer this PR to be closed, or kept as a draft reference until implementation starts.

keep it, remove the design draft and just update the kinematics documentation here.

[silanus23]

Sorry for giving a too late update. Things are not the same as my proposal but I tried to stick with the #692 @christophfroehlich 's suggestions. I will provide 6 wheeler controller with this.
The package derives many of it's functions from steering_controller_library so maybe I may need to add signature of the writers of steering_controller.
My main motive here is instead restricting user with some pre added steering models one can add simply any robot model by just entering couple of equations and updating an unordered_map (not vector to make sure the ease of use).
I provided an example use of this package in https://github.com/silanus23/generic_steering_controller_demo in here. I am looking forward for your guidance. Thanks for your time.

[Zarqu0n]

I think this is so usefull development. I am waiting for improvements. Did you try the both steering and traction in the same joint in your example bot?

[silanus23]

@Zarqu0n That's an important question. Thanks for pointing that out. I guess current implementation can handle both scenarios but this thing surely needs a testing. My current demo doesn't test this. I will put this on a test asap with a 4 wheeler demo.