Fix handles for following controllers of diff_drive_controller

[christophfroehlich]

As reported in ros-controls/ros2_control_demos#710, the pid_controller activation failed because it checked for prefix_name and interface_name separately, expecting prefix_name pid_controller_left_wheel_joint/left_wheel_joint with interface velocity, but actually it is prefix_name pid_controller_left_wheel_joint with interface_name left_wheel_joint/velocity.

Let's just check the full name.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 84.16%. Comparing base (50ff026) to head (0db2dec).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
...iff_drive_controller/src/diff_drive_controller.cpp	50.00%	5 Missing ⚠️

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@@            Coverage Diff             @@
##           master    #1513      +/-   ##
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- Coverage   84.19%   84.16%   -0.03%     
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Files with missing lines	Coverage Δ
...iff_drive_controller/src/diff_drive_controller.cpp	72.09% <50.00%> (-0.85%)	⬇️

[Juliaj]

I tested the fix above and it works with example_16. However, I wonder these debug message could lead to confusion if the developer is unaware about the chain created under the hood. For example_16, prefix: interface pair is pid_controller_left_wheel_joint : left_wheel_joint/velocity.

A naive alternative to the current fix could be:

• preserve the prefix and interface as in the current definition
• introduce a mode (e.g. chained_right) with additional params and logic to handle the use case.

[Juliaj]

Thought about this a bit more. Please ignore my comments on alternative fix above because I believe it is supported by default. This is illustrated by demo example_12 where the forward_position_controller controls "joints" exposed by the second level controller. These (virtual ?) joints are configured in a hierarchical pattern.

# Third-level controllers
forward_position_controller:
  ros__parameters:
    type: forward_command_controller/ForwardCommandController
    joints:
      - position_controller/joint1_position_controller/joint1
      - position_controller/joint2_position_controller/joint2
    interface_name: position

[Juliaj]

LGTM. This was tested as part of demo example_16.

[christophfroehlich]

I fixed the wrong part in the chain, superseded by #1528