Analysis Gazebo model file : *.sdf for Tilt-model

 

Gazebo Model Configuration

Brief Configuration View

Gazebo Tiltrotor model is described below :

 

Model tree is shown below :

• model : tiltrotor
• link : base_link
• sensors (Airspeed sensor, IMU, GPS...)
• Links and Joints (for geometry. motor, rotor, wing, control surfaces)
• Plugins
  • LiftDrag (Aerodynamics)
  • gazebo_motor_model (Rotor model)
  • groundtruth
  • magnetometer
  • barometer
  • mavlink_interface

 

 

Next, Im gonna show How to describe links and joints.

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Link and Joint

Joints connect between Links. and It makes an link tree.

An object on the vehicle, made as a link and connect the link to parent link by using Joint

• Link
  • Pose
  • Inertia
  • Collision
    • Pose
    • Geometry
  • Visual (Usually, same as Collision)
    
    • Pose
    • Geometry
• Joint
  • Child : Child link
  • Parent : Parent link
  • Axis (Enabing to rotate)

Examples on Tiltrotor Model

 

Gazebo Motor Plugin

   <plugin name='front_right_motor_model' filename='libgazebo_motor_model.so'>
      <robotNamespace></robotNamespace>
      <jointName>rotor_0_joint</jointName>
      <linkName>rotor_0</linkName>
      <turningDirection>ccw</turningDirection>
      <timeConstantUp>0.0125</timeConstantUp>
      <timeConstantDown>0.025</timeConstantDown>
      <maxRotVelocity>1500</maxRotVelocity>
      <motorConstant>2e-05</motorConstant>
      <momentConstant>0.06</momentConstant>
      <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
      <motorNumber>0</motorNumber>
      <rotorDragCoefficient>0.0000806428</rotorDragCoefficient>
      <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
      <motorSpeedPubTopic>/motor_speed/0</motorSpeedPubTopic>
      <rotorVelocitySlowdownSim>20</rotorVelocitySlowdownSim>
    </plugin>

 

 

Mavlink Control Interface

    <plugin name='mavlink_interface' filename='libgazebo_mavlink_interface.so'>
      <robotNamespace></robotNamespace>
      ...
      <motorSpeedCommandPubTopic>/gazebo/command/motor_speed</motorSpeedCommandPubTopic>
      <control_channels>
        <channel name="rotor0">
          <input_index>0</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_0_joint</joint_name>
        </channel>
        ...
        <channel name="motor0_tilt">
          <input_index>4</input_index>
          <input_offset>0.785398</input_offset>
          <input_scaling>0.785398</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position</joint_control_type>
          <joint_name>motor_0_joint</joint_name>
           <joint_control_pid>
            <p>10</p>
            <i>0</i>
            <d>0</d>
            <iMax>0.0</iMax>
            <iMin>0.0</iMin>
            <cmdMax>2</cmdMax>
            <cmdMin>-2</cmdMin>
            <errMax>0.2</errMax>
          </joint_control_pid>
        </channel>
        ...
        <channel name="left_elevon">
          <input_index>6</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>0</zero_position_armed>
          <joint_control_type>position_kinematic</joint_control_type>
          <joint_name>left_elevon_joint</joint_name>
        </channel>
      </control_channels>
    </plugin>