ROS 2 Migration: Harness

Overview

This pages describes the changes in the harness plugin in gazebo_plugins for ROS 2, including a migration guide.

Summary

• Instead of using std_msgs/msg/Bool for detach messages and checking for truth value, detach messages are now std_msgs/msg/Empty. On receiving the message, without any checks, the joint would be detached.
• Harness topics can now be changed using remapping arguments.
• By setting the <init_vel> in sdf, the initial velocity of harness on launching gazebo can be set.

SDF parameters

ROS 1	ROS 2
robotNamespace	❌

Example Migration

ROS1

    <plugin name="plugin_name" filename="libgazebo_ros_harness.so">
      <!-- Add a namespace -->
      <robotNamespace>demo</robotNamespace>

      <joint name="joint1" type="prismatic">
        <pose>0 0 0 0 0 0</pose>
        <parent>world</parent>
        <child>link</child>
        <axis>
          <xyz>0 0 1</xyz>
          <dynamics>
            <damping>10</damping>
          </dynamics>
          <limit>
            <lower>-1.5</lower>
            <upper>1.5</upper>
            <effort>10000</effort>
            <velocity>-1</velocity>
            <stiffness>0</stiffness>
            <dissipation>0</dissipation>
          </limit>
        </axis>
        <physics>
          <ode>
            <implicit_spring_damper>1</implicit_spring_damper>
            <limit>
              <cfm>0.0</cfm>
              <erp>0.0</erp>
            </limit>
          </ode>
        </physics>
      </joint>

      <!-- The joint that raises or lowers the harness -->
      <winch>
        <!-- This must be a joint specified within
             the body of this plugin. -->
        <joint>joint1</joint>

        <!-- PID value for velocity control of the winch -->
        <pos_pid>
          <p>1000000</p>
          <i>0</i>
          <d>0</d>
          <i_min>0</i_min>
          <i_max>0</i_max>
          <cmd_min>-10000</cmd_min>
          <cmd_max>10000</cmd_max>
        </pos_pid>
        <vel_pid>
          <p>10000</p>
          <i>0</i>
          <d>0</d>
          <i_min>0</i_min>
          <i_max>0</i_max>
          <cmd_min>0</cmd_min>
          <cmd_max>10000</cmd_max>
        </vel_pid>
      </winch>

      <!-- Joint to detach. Once the joint is detached, it cannot be
           reattached. This must be a joint specified within the
           body of this plugin. -->
      <detach>joint1</detach>
    </plugin>

ROS2

    <plugin name="plugin_name" filename="libgazebo_ros_harness.so">
      <ros>
        <!-- Add a namespace -->
        <namespace>demo</namespace>

        <!-- Default harness velocity topic `${MODEL_NAME}/harness/velocity` can be changed -->
        <!-- Here it is set to `/demo/velocity_demo` -->
        <remapping>box/harness/velocity:=velocity_demo</remapping>

        <!-- Default harness detach topic `${MODEL_NAME}/harness/detach` can be changed -->
        <!-- Here it is set to `/demo/detach_demo` -->
        <remapping>box/harness/detach:=detach_demo</remapping>
      </ros>
      <!-- set initial harness velocity -->
      <init_vel>-0.1</init_vel>

      <joint name="joint1" type="prismatic">
          <!-- The joint that raises or lowers the harness.
           This must be specified within the body of this plugin. -->
          <pose>0 0 0 0 0 0</pose>
          <parent>world</parent>
          <child>link</child>
          <axis>
            <xyz>0 0 1</xyz>
            <dynamics>
              <damping>10</damping>
            </dynamics>
            <limit>
              <lower>-1.5</lower>
              <upper>1.5</upper>
              <effort>10000</effort>
              <velocity>-1</velocity>
              <stiffness>0</stiffness>
              <dissipation>0</dissipation>
            </limit>
          </axis>
          <physics>
            <ode>
              <implicit_spring_damper>1</implicit_spring_damper>
              <limit>
                <cfm>0.0</cfm>
                <erp>0.0</erp>
              </limit>
            </ode>
          </physics>
        </joint>
        <winch>
          <joint>joint1</joint>
          <!-- PID value for velocity control of the winch. -->
          <pos_pid>
            <p>1000000</p>
            <i>0</i>
            <d>0</d>
            <i_min>0</i_min>
            <i_max>0</i_max>
            <cmd_min>-10000</cmd_min>
            <cmd_max>10000</cmd_max>
          </pos_pid>
          <vel_pid>
            <p>10000</p>
            <i>0</i>
            <d>0</d>
            <i_min>0</i_min>
            <i_max>0</i_max>
            <cmd_min>0</cmd_min>
            <cmd_max>10000</cmd_max>
          </vel_pid>
        </winch>
        <!-- Joint to detach. Once the joint is detached, it cannot be
          reattached. This must be a joint specified within the
          body of this plugin. -->
        <detach>joint1</detach>
    </plugin>