Add Support for SDF

[Amronos]

Fixes #632
I have modified hardware_interface/src/component_parser.cpp to add support for SDF models.

To test this out, something like the following SDF file can be passed to robot_state_publisher instead of a URDF file alongside using it to spawn the robot into the gazebo world. I do plan to make a PR into gz_ros2_control_demos to add a demo for this.

<?xml version="1.0" ?>
<sdf version="1.8">
  <model canonical_link="base_link" name="my_robot">
    <!-- BASE -->
    <link name="base_link">
      <must_be_base_link>true</must_be_base_link>
    </link>
    <!-- CHASSIS -->
    <joint name="chassis_joint" type="fixed">
      <parent>base_link</parent>
      <child>chassis_link</child>
      <pose relative_to="base_link">0 0 0.075 0 0 0</pose>
    </joint>
    <link name="chassis_link">
      <pose relative_to="chassis_joint"/>
      <visual name="chassis_link_visual">
        <geometry>
          <box>
            <size>
                0.3 0.3 0.15
              </size>
          </box>
        </geometry>
        <material>
          <ambient>1 1 1 1</ambient>
          <diffuse>1 1 1 1</diffuse>
        </material>
      </visual>
      <collision name="chassis_link_collision">
        <geometry>
          <box>
            <size>
                0.3 0.3 0.15
              </size>
          </box>
        </geometry>
      </collision>
      <inertial>
        <mass>0.5</mass>
        <inertia>
          <ixx>0.0046875</ixx>
          <ixy>0.0</ixy>
          <ixz>0.0</ixz>
          <iyy>0.0046875</iyy>
          <iyz>0.0</iyz>
          <izz>0.0075</izz>
        </inertia>
      </inertial>
    </link>
    <!-- lEFT WHEEL -->
    <joint name="left_wheel_joint" type="revolute">
      <parent>chassis_link</parent>
      <child>left_wheel_link</child>
      <pose relative_to="chassis_link">0.09 0.16999999999999998 -0.075 -1.5707963267948966 0 0</pose>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-inf</lower>
          <upper>inf</upper>
        </limit>
      </axis>
    </joint>
    <link name="left_wheel_link">
      <pose relative_to="left_wheel_joint"/>
      <visual name="left_wheel_link_visual">
        <geometry>
          <cylinder>
            <radius>0.05</radius>
            <length>0.04</length>
          </cylinder>
        </geometry>
        <material>
          <ambient>0 0 1</ambient>
          <diffuse>0 0 1</diffuse>
        </material>
      </visual>
      <collision name="left_wheel_link_collision">
        <geometry>
          <cylinder>
            <radius>0.05</radius>
            <length>0.04</length>
          </cylinder>
        </geometry>
      </collision>
      <inertial>
        <mass>0.1</mass>
        <inertia>
          <ixx>7.583333333333335e-05</ixx>
          <ixy>0.0</ixy>
          <ixz>0.0</ixz>
          <iyy>7.583333333333335e-05</iyy>
          <iyz>0.0</iyz>
          <izz>0.00012500000000000003</izz>
        </inertia>
      </inertial>
    </link>
    <!-- RIGHT WHEEL -->
    <joint name="right_wheel_joint" type="revolute">
      <parent>chassis_link</parent>
      <child>right_wheel_link</child>
      <pose relative_to="chassis_link">0.09 -0.16999999999999998 -0.075 -1.5707963267948966 0 0</pose>
      <axis>
        <xyz>0 0 1</xyz>
        <!-- limit would not be specified because if the type was continuous -->
        <limit>
          <lower>-inf</lower>
          <upper>inf</upper>
        </limit>
      </axis>
    </joint>
    <link name="right_wheel_link">
      <pose relative_to="right_wheel_joint"/>
      <visual name="right_wheel_link_visual">
        <geometry>
          <cylinder>
            <radius>0.05</radius>
            <length>0.04</length>
          </cylinder>
        </geometry>
        <material>
          <ambient>0 0 1</ambient>
          <diffuse>0 0 1</diffuse>
        </material>
      </visual>
      <collision name="right_wheel_link_collision">
        <geometry>
          <cylinder>
            <radius>0.05</radius>
            <length>0.04</length>
          </cylinder>
        </geometry>
      </collision>
      <inertial>
        <mass>0.1</mass>
        <inertia>
          <ixx>7.583333333333335e-05</ixx>
          <ixy>0.0</ixy>
          <ixz>0.0</ixz>
          <iyy>7.583333333333335e-05</iyy>
          <iyz>0.0</iyz>
          <izz>0.00012500000000000003</izz>
        </inertia>
      </inertial>
    </link>
    <!-- CASTER -->
    <joint name="caster_joint" type="revolute">
      <parent>chassis_link</parent>
      <child>caster_link</child>
      <pose relative_to="chassis_link">-0.09 0 -0.075 0 0 0</pose>
      <axis>
        <xyz>1 1 1</xyz>
        <limit>
          <lower>-inf</lower>
          <upper>inf</upper>
        </limit>
      </axis>
    </joint>
    <link name="caster_link">
      <pose relative_to="caster_joint"/>
      <visual name="caster_link_visual">
        <geometry>
          <sphere>
            <radius>0.05</radius>
          </sphere>
        </geometry>
        <material>
          <ambient>0 0 1</ambient>
          <diffuse>0 0 1</diffuse>
        </material>
      </visual>
      <collision name="caster_link_collision">
        <geometry>
          <sphere>
            <radius>0.05</radius>
          </sphere>
        </geometry>
      </collision>
      <inertial>
        <mass>0.1</mass>
        <inertia>
          <ixx>0.00010000000000000002</ixx>
          <ixy>0.0</ixy>
          <ixz>0.0</ixz>
          <iyy>0.00010000000000000002</iyy>
          <iyz>0.0</iyz>
          <izz>0.00010000000000000002</izz>
        </inertia>
      </inertial>
    </link>
    <ros2_control name="GazeboSimSystem" type="system">
      <hardware>
        <plugin>gz_ros2_control/GazeboSimSystem</plugin>
      </hardware>
      <joint name="left_wheel_joint">
        <command_interface name="velocity">
          <param name="min">-10</param>
          <param name="max">10</param>
        </command_interface>
        <state_interface name="velocity"/>
        <state_interface name="position"/>
      </joint>
      <joint name="right_wheel_joint">
        <command_interface name="velocity">
          <param name="min">-10</param>
          <param name="max">10</param>
        </command_interface>
        <state_interface name="velocity"/>
        <state_interface name="position"/>
      </joint>
    </ros2_control>
    <plugin filename="libgz_ros2_control-system.so" name="gz_ros2_control::GazeboSimROS2ControlPlugin">
      <parameters>/home/amronos/ros2_ws/install/my_robot/share/my_robot/config/my_controllers.yaml</parameters>
    </plugin>
  </model>
</sdf>

[saikishor]

Can you please add a test with an example SDF here: https://github.com/ros-controls/ros2_control/blob/master/hardware_interface/test/test_component_parser.cpp?

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 86.74%. Comparing base (84e85f9) to head (424228b).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
hardware_interface/src/component_parser.cpp	16.66%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1763      +/-   ##
==========================================
- Coverage   86.79%   86.74%   -0.06%     
==========================================
  Files         116      116              
  Lines       10715    10719       +4     
  Branches      981      982       +1     
==========================================
- Hits         9300     9298       -2     
- Misses       1062     1067       +5     
- Partials      353      354       +1     

Flag	Coverage Δ
unittests	86.74% <16.66%> (-0.06%)	⬇️

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Files with missing lines	Coverage Δ
hardware_interface/src/component_parser.cpp	93.68% <16.66%> (-0.75%)	⬇️

... and 1 file with indirect coverage changes

[saikishor]

@Amronos The changes look good to me. Can you add that SDF parsing is also supported through robot_description topic in the release_notes.rst?.

Sorry for not pointing out earlier

[saikishor]

LGTM

[azeey]

This is great! Thanks @Amronos