Conection between SITL and MulticopterMotorModel

ArduCopter
,
1

Hello,
I’m trying to replace the LiftDrag plugin with the MulticopterMotorModel plugin.
To do this, I switched to Gazebo Garden, ardupilot_gazebo ( 0753b06 ), Arducopter 4.5.7.

My SDF model:

<?xml version='1.0'?>
<sdf version="1.6">
  <model name="iris_with_ardupilot">
    <include>
      <uri>model://iris_with_standoffs</uri>
    </include>

    <!-- plugins -->
    <plugin filename="gz-sim-joint-state-publisher-system"
      name="gz::sim::systems::JointStatePublisher">
    </plugin>

    <plugin
      filename="gz-sim-multicopter-motor-model-system"
      name="gz::sim::systems::MulticopterMotorModel">
      <robotNamespace></robotNamespace>
      <jointName>iris_with_standoffs::rotor_0_joint</jointName>
      <linkName>iris_with_standoffs::rotor_0</linkName>
      <turningDirection>ccw</turningDirection>
      <timeConstantUp>0.0125</timeConstantUp>
      <timeConstantDown>0.025</timeConstantDown>
      <maxRotVelocity>1381</maxRotVelocity>
      <motorConstant>8.54858e-06</motorConstant>
      <momentConstant>0.016</momentConstant>
      <commandSubTopic>/model/iris_with_standoffs/rotors/cmd_vel</commandSubTopic>
      <motorNumber>0</motorNumber>
      <rotorDragCoefficient>8.06428e-05</rotorDragCoefficient>
      <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
      <motorSpeedPubTopic>/model/iris_with_standoffs/rotors/speed/0</motorSpeedPubTopic>
      <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
      <motorType>velocity</motorType>
    </plugin>
    <plugin
      filename="gz-sim-multicopter-motor-model-system"
      name="gz::sim::systems::MulticopterMotorModel">
      <robotNamespace></robotNamespace>
      <jointName>iris_with_standoffs::rotor_1_joint</jointName>
      <linkName>iris_with_standoffs::rotor_1</linkName>
      <turningDirection>ccw</turningDirection>
      <timeConstantUp>0.0125</timeConstantUp>
      <timeConstantDown>0.025</timeConstantDown>
      <maxRotVelocity>1381</maxRotVelocity>
      <motorConstant>8.54858e-06</motorConstant>
      <momentConstant>0.016</momentConstant>
      <commandSubTopic>/model/iris_with_standoffs/rotors/cmd_vel</commandSubTopic>
      <motorNumber>1</motorNumber>
      <rotorDragCoefficient>8.06428e-05</rotorDragCoefficient>
      <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
      <motorSpeedPubTopic>/model/iris_with_standoffs/rotors/speed/1</motorSpeedPubTopic>
      <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
      <motorType>velocity</motorType>
    </plugin>
    <plugin
      filename="gz-sim-multicopter-motor-model-system"
      name="gz::sim::systems::MulticopterMotorModel">
      <robotNamespace></robotNamespace>
      <jointName>iris_with_standoffs::rotor_2_joint</jointName>
      <linkName>iris_with_standoffs::rotor_2</linkName>
      <turningDirection>cw</turningDirection>
      <timeConstantUp>0.0125</timeConstantUp>
      <timeConstantDown>0.025</timeConstantDown>
      <maxRotVelocity>1381</maxRotVelocity>
      <motorConstant>8.54858e-06</motorConstant>
      <momentConstant>0.016</momentConstant>
      <commandSubTopic>/model/iris_with_standoffs/rotors/cmd_vel</commandSubTopic>
      <motorNumber>2</motorNumber>
      <rotorDragCoefficient>8.06428e-05</rotorDragCoefficient>
      <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
      <motorSpeedPubTopic>/model/iris_with_standoffs/rotors/speed/2</motorSpeedPubTopic>
      <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
      <motorType>velocity</motorType>
    </plugin>
    <plugin
      filename="gz-sim-multicopter-motor-model-system"
      name="gz::sim::systems::MulticopterMotorModel">
      <robotNamespace></robotNamespace>
      <jointName>iris_with_standoffs::rotor_3_joint</jointName>
      <linkName>iris_with_standoffs::rotor_3</linkName>
      <turningDirection>cw</turningDirection>
      <timeConstantUp>0.0125</timeConstantUp>
      <timeConstantDown>0.025</timeConstantDown>
      <maxRotVelocity>1381</maxRotVelocity>
      <motorConstant>8.54858e-06</motorConstant>
      <momentConstant>0.016</momentConstant>
      <commandSubTopic>/model/iris_with_standoffs/rotors/cmd_vel</commandSubTopic>
      <motorNumber>3</motorNumber>
      <rotorDragCoefficient>8.06428e-05</rotorDragCoefficient>
      <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
      <motorSpeedPubTopic>/model/iris_with_standoffs/rotors/speed/3</motorSpeedPubTopic>
      <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
      <motorType>velocity</motorType>
    </plugin>


    <plugin name="ArduPilotPlugin"
      filename="libArduPilotPlugin">
      <!-- Port settings -->
      <fdm_addr>127.0.0.1</fdm_addr>
      <fdm_port_in>9002</fdm_port_in>
      <connectionTimeoutMaxCount>5</connectionTimeoutMaxCount>
      <lock_step>1</lock_step>
      <have_32_channels>0</have_32_channels>

      <!-- Frame conventions
        Require by ArduPilot: change model and gazebo from XYZ to XY-Z coordinates
      -->
      <modelXYZToAirplaneXForwardZDown>0 0 0 3.141593 0 0</modelXYZToAirplaneXForwardZDown>
      <gazeboXYZToNED>0 0 0 3.141593 0 0</gazeboXYZToNED>

      <!-- Sensors -->
      <imuName>iris_with_standoffs::imu_link::imu_sensor</imuName>

      <!--
          incoming control command [0, 1]
          so offset it by 0 to get [0, 1]
          and divide max target by 1.
          offset = 0
          multiplier = 838 max rpm / 1 = 838
        -->
      <control channel="0">
        <jointName>iris_with_standoffs::rotor_0_joint</jointName>
        <useForce>1</useForce>
        <multiplier>838</multiplier>
        <offset>0</offset>
        <servo_min>1100</servo_min>
        <servo_max>1900</servo_max>
        <type>COMMAND</type>
        <cmd_topic>/model/iris_with_standoffs/joint/rotor_0_joint/cmd_vel</cmd_topic>
        <!-- <type>VELOCITY</type>
        <p_gain>0.20</p_gain>
        <i_gain>0</i_gain>
        <d_gain>0</d_gain>
        <i_max>0</i_max>
        <i_min>0</i_min>
        <cmd_max>2.5</cmd_max>
        <cmd_min>-2.5</cmd_min>
        <controlVelocitySlowdownSim>1</controlVelocitySlowdownSim> -->
      </control>

      <control channel="1">
        <jointName>iris_with_standoffs::rotor_1_joint</jointName>
        <useForce>1</useForce>
        <multiplier>838</multiplier>
        <offset>0</offset>
        <servo_min>1100</servo_min>
        <servo_max>1900</servo_max>
        <type>COMMAND</type>
        <cmd_topic>/model/iris_with_standoffs/joint/rotor_1_joint/cmd_vel</cmd_topic>
        <!-- <type>VELOCITY</type>
        <p_gain>0.20</p_gain>
        <i_gain>0</i_gain>
        <d_gain>0</d_gain>
        <i_max>0</i_max>
        <i_min>0</i_min>
        <cmd_max>2.5</cmd_max>
        <cmd_min>-2.5</cmd_min>
        <controlVelocitySlowdownSim>1</controlVelocitySlowdownSim> -->
      </control>

      <control channel="2">
        <jointName>iris_with_standoffs::rotor_2_joint</jointName>
        <useForce>1</useForce>
        <multiplier>-838</multiplier>
        <offset>0</offset>
        <servo_min>1100</servo_min>
        <servo_max>1900</servo_max>
        <type>COMMAND</type>
        <cmd_topic>/model/iris_with_standoffs/joint/rotor_2_joint/cmd_vel</cmd_topic>
        <!-- <type>VELOCITY</type>
        <p_gain>0.20</p_gain>
        <i_gain>0</i_gain>
        <d_gain>0</d_gain>
        <i_max>0</i_max>
        <i_min>0</i_min>
        <cmd_max>2.5</cmd_max>
        <cmd_min>-2.5</cmd_min>
        <controlVelocitySlowdownSim>1</controlVelocitySlowdownSim> -->
      </control>

      <control channel="3">
        <jointName>iris_with_standoffs::rotor_3_joint</jointName>
        <useForce>1</useForce>
        <multiplier>-838</multiplier>
        <offset>0</offset>
        <servo_min>1100</servo_min>
        <servo_max>1900</servo_max>
        <type>COMMAND</type>
        <cmd_topic>/model/iris_with_standoffs/joint/rotor_3_joint/cmd_vel</cmd_topic>
        <!-- <type>VELOCITY</type>
        <p_gain>0.20</p_gain>
        <i_gain>0</i_gain>
        <d_gain>0</d_gain>
        <i_max>0</i_max>
        <i_min>0</i_min>
        <cmd_max>2.5</cmd_max>
        <cmd_min>-2.5</cmd_min>
        <controlVelocitySlowdownSim>1</controlVelocitySlowdownSim> -->
      </control>

    </plugin>

  </model>
</sdf>

I created it based on the omnicopter model that I found on the web.

The video shows that the connection appears ( MulticopterMotorModel connection problem - Google Drive ), but the motors are not working, what could be the reason for this? And how to fix it?

2

The MultiCopterMotorModel plugin expects an gz::msgs::Actuator message to be published by the plugin bridging SITL and Gazebo. The version of ArduPilotPlugin available in master does not do this. The model you are using is not released and relies on an unreleased branch of ardupilot_gazebo, so it’s not going to work unless that is also built and configured.

3

Thank you, I remember from previous topics that this gz::msgs::Actuator message should be configured. But I am not very familiar with the structure of ArduPilotPlugin, if you could tell me more about it and where exactly it is possible to set it up in theory, I would be glad.

It should also be noted that I also tried out the version made by @Bhajneet_Singh_Bedi and described in this topic (GSoC’25 Gazebo Plugin Model of a Motor). The problem with yaw axis rotation is also present there.

4

Thank you, I implemented the connection with this plugin, it got a little better, but you can still catch a similar effect, I’ll keep looking. But for now I’ve settled on this solution.