Remove members to pid state message

[ViktorCVS]

Remove members from the pid state message to make it cleaner, without affecting users.

These changes support modifications made to the PID controller in the control_toolbox package. For more details, see ros-controls/control_toolbox#298.

If this PR is approved, it should be merged together with the main PR in the control_toolbox package referenced above.

[christophfroehlich]

I also question the original design: Do we really need to add these variables to the message? For what purpose? I see that it might be beneficial to add the gains for the case when any auto-gain-scheduling is used. But the clamp values and anti-windup methods won't change for a controller, right?

[ViktorCVS]

I also question the original design: Do we really need to add these variables to the message? For what purpose? I see that it might be beneficial to add the gains for the case when any auto-gain-scheduling is used. But the clamp values and anti-windup methods won't change for a controller, right?

Well, I agree with you. Changing those variables at runtime might be appropriate in some situations, but I think a simpler message is more reasonable. I don’t see this as a common strategy, so it likely won’t affect most users. I’ll make this change and update the message access in the control_toolbox PR.

[christophfroehlich]

LGTM

[christophfroehlich]

@bmagyar this will now break the semi-binary builds, until we can merge ros-controls/control_toolbox#298 (I hadn't had time for a review yet) 🙈