Problems when adding lidar and camera sensors to the same robot on Ignition

[lucaslbmp]

Environment

• OS Version:
• Source or binary build?: Binary, igntion-gazebo-6.8.0

Description

Trying to spawn a simple 2-wheeled robot model (named "r2d2" here) in Ignition containing both lidar and camera sensor.

• Expected behavior: The model is spawned and their respective topics are available, just what happens if the model is spawned with only one of the sensors.
• Actual behavior: The simulator crashes and an error message is displayed.

Steps to reproduce

1. In the main xacro of a mode (in this case teste_bot), add tags for each sensor

<gazebo reference="cam_front">
        <sensor name='${name}' type='camera'>
            <pose>${body_dim_x/2} 0 ${body_dim_z/2} 0 0 0</pose>
            <visualize>true</visualize>
            <update_rate>5</update_rate>
            <topic>${name}/camera_image</topic>
            <camera>
                <!-- <horizontal_fov>1.047</horizontal_fov> -->
                <image>
                    <!-- <width>320</width>
                    <height>240</height> -->
                    <width>640</width>
                    <height>420</height>
                    <!-- <format>B8G8R8</format> -->
                </image>
                <!-- <clip>
                    <near>0.1</near>
                    <far>100</far>
                </clip> -->
            </camera>


               <plugin filename="libignition-gazebo-sensors-system.so" name="ignition::gazebo::systems::Sensors">
          <render_engine>ogre</render_engine>
            </plugin>
        </sensor>
    </gazebo>

<gazebo reference="base_lidar">
        <sensor name="${name}" type='gpu_lidar'>
            <pose>0 0 ${body_height*0.6} 0 0 0</pose>
            <!-- <pose>0 0 1.0 0 0 0</pose> -->
            <topic>${name}/lidar</topic>
            <update_rate>10</update_rate>
            <ray>
                <scan>
                    <horizontal>
                        <!-- <samples>90</samples> -->
                        <samples>10</samples>
                        <resolution>1</resolution>
                        <min_angle>${-radians(20)}</min_angle>
                        <max_angle>${radians(20)}</max_angle>
                    </horizontal>
                    <vertical>
                        <samples>10</samples>
                        <resolution>1</resolution>
                        <min_angle>${-radians(10)}</min_angle>
                        <max_angle>${radians(10)}</max_angle>
                    </vertical>
                </scan>
                <range>
                    <!-- <min>0.08</min> -->
                    <min>0.1</min>
                    <max>2.0</max>
                    <resolution>0.01</resolution>
                </range>
            </ray>
            <always_on>1</always_on>
            <visualize>true</visualize>

            <plugin filename="libignition-gazebo-sensors-system.so" name="ignition::gazebo::systems::Sensors">
                <render_engine>ogre</render_engine>
            </plugin>
        </sensor>
    </gazebo>

2. Build the workspace: colcon build
3. Launch the simulator: ign gazebo empty.sdf --render-engine ogre
4. Spawn the robot: ign service -s /world/empty/create --reqtype ignition.msgs.EntityFactory --reptype ignition.msgs.Boolean --timeout 300 --req 'sdf_filename: "/home/lucas/ros2_ntu_ws/src/ntu_gazebo/models/teste_bot/urdf/teste_bot.urdf" '

Output

The simulator crashes and the following message is displayed:

[lucaslbmp]

I found out the problem: the plugin "ignition::gazebo::systems::Sensors" should be called only once, even though it is used by both sensors.

[chapulina]

I found out the problem: the plugin "ignition::gazebo::systems::Sensors" should be called only once, even though it is used by both sensors.

Glad to hear it! It would be interesting to add some safety check to that plugin that prevents 2 instantiations.

[msminirobot]

This is actually also very important for multi-robot simulations.