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JointController plugin

gazebo source demo world

  • Velocity mode: This mode lets the user control the desired joint velocity directly.
  • Force mode: A user who wants to control joint velocity using a PID controller .
velocity mode
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<plugin
 filename="gz-sim-joint-controller-system"
 name="gz::sim::systems::JointController">
 <joint_name>j1</joint_name>
</plugin>

create topic named

default topic name
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/model/<model_name>/joint/<joint_name>/cmd_vel

force mode

Still ask for velocity but now the velocity control by apply force

Joint controllers PID settings

PID settings

If the pid not config properly the joint controller failed to reach the desired velocity and behaved absurdly due to improper gains

force mode
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<plugin
 filename="gz-sim-joint-controller-system"
 name="gz::sim::systems::JointController">
 <joint_name>j1</joint_name>
 <use_force_commands>true</use_force_commands>
 <p_gain>0.2</p_gain>
 <i_gain>0.01</i_gain>
</plugin>

Demo: Velocity control

Velocity 
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<?xml version="1.0" ?>
<sdf version="1.6">
  <world name="default">
    <light type="directional" name="sun">
      <cast_shadows>true</cast_shadows>
      <pose>0 0 10 0 0 0</pose>
      <diffuse>1 1 1 1</diffuse>
      <specular>0.5 0.5 0.5 1</specular>
      <attenuation>
        <range>1000</range>
        <constant>0.9</constant>
        <linear>0.01</linear>
        <quadratic>0.001</quadratic>
      </attenuation>
      <direction>-0.5 0.1 -0.9</direction>
    </light>
    <model name="joint_controller_demo">
      <pose>0 0 0 0 0 0</pose>
      <link name="base_link">
        <pose>0.0 0.0 0.0 0 0 0</pose>
        <inertial>
          <inertia>
            <ixx>2.501</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>2.501</iyy>
            <iyz>0</iyz>
            <izz>5</izz>
          </inertia>
          <mass>120.0</mass>
        </inertial>
        <visual name="base_visual">
          <pose>0.0 0.0 0.0 0 0 0</pose>
          <geometry>
            <box>
              <size>0.5 0.5 0.01</size>
            </box>
          </geometry>
        </visual>
        <collision name="base_collision">
          <pose>0.0 0.0 0.0 0 0 0</pose>
          <geometry>
            <box>
              <size>0.5 0.5 0.01</size>
            </box>
          </geometry>
        </collision>
      </link>
      <link name="rotor">
        <pose>0.0 0.0 0.1 0 0 0</pose>
        <inertial>
          <inertia>
            <ixx>0.032</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.032</iyy>
            <iyz>0</iyz>
            <izz>0.00012</izz>
          </inertia>
          <mass>0.6</mass>
        </inertial>
        <visual name="visual">
          <geometry>
            <box>
              <size>0.25 0.1 0.05</size>
            </box>
          </geometry>
          <material>
            <ambient>0.2 0.8 0.2 1</ambient>
            <diffuse>0.8 0 0 1</diffuse>
          </material>
        </visual>
        <collision name="collision">
          <geometry>
            <box>
              <size>0.25 0.1 0.05</size>
            </box>
          </geometry>
        </collision>
      </link>

      <joint name="world_fixed" type="fixed">
        <parent>world</parent>
        <child>base_link</child>
      </joint>

      <joint name="j1" type="revolute">
        <pose>0 0 -0.5 0 0 0</pose>
        <parent>base_link</parent>
        <child>rotor</child>
        <axis>
          <xyz>0 0 1</xyz>
        </axis>
      </joint>
      <plugin
 filename="gz-sim-joint-controller-system"
 name="gz::sim::systems::JointController">
 <joint_name>j1</joint_name>
 <initial_velocity>1.0</initial_velocity>
</plugin>
    </model>
  </world>
</sdf>

Reference