S253809: /* Typical Usage */

2026-05-28T09:04:54Z

Typical Usage

← Older revision		Revision as of 11:04, 28 May 2026
Line 110:		Line 110:

	Start robot description publisher:		Start robot description publisher:
			ros2 launch fejemis_description model.launch.py
	~~```bash~~
	ros2 launch fejemis_description model.launch.py
	~~```~~

	Start with simulation time:		Start with simulation time:
			ros2 launch fejemis_description model.launch.py use_sim_time:=true
	~~```bash~~
	ros2 launch fejemis_description model.launch.py use_sim_time:=true
	~~```~~

	In most full-system runs, this launch file is included by top-level bringup (for example in simulation launch stacks).		In most full-system runs, this launch file is included by top-level bringup (for example in simulation launch stacks).

S253809: Created page with "Back to Fejemis ROS2 Software == Purpose == ''fejemis_description'' is the robot description package for Fejemis. It defines the robot model using URDF/Xacro and publishes the TF model state so the rest of the ROS 2 stack can use a consistent robot geometry. The package is responsible for: * Building the Fejemis robot model from modular xacro files. * Publishing ''robot_description'' and TF through ''robot_state_publisher''. * Providing a simulation-friendly whee..."

2026-05-28T09:03:59Z

Created page with "Back to Fejemis ROS2 Software == Purpose == ''fejemis_description'' is the robot description package for Fejemis. It defines the robot model using URDF/Xacro and publishes the TF model state so the rest of the ROS 2 stack can use a consistent robot geometry. The package is responsible for: * Building the Fejemis robot model from modular xacro files. * Publishing ''robot_description'' and TF through ''robot_state_publisher''. * Providing a simulation-friendly whee..."

New page

Back to [[Fejemis ROS2 Software]]

== Purpose ==

''fejemis_description'' is the robot description package for Fejemis. It defines the robot model using URDF/Xacro and publishes the TF model state so the rest of the ROS 2 stack can use a consistent robot geometry.

The package is responsible for:

* Building the Fejemis robot model from modular xacro files.
* Publishing ''robot_description'' and TF through ''robot_state_publisher''.
* Providing a simulation-friendly wheel configuration through launch arguments.
* Keeping a shared frame and link structure used by simulation, mapping, and navigation.

== Package Layout ==

Important folders:

* ''launch'' - launch files for model generation and state publishing.
* ''xacro'' - modular robot model definition files.
* ''config'' - controller/simulation-related configuration.

Main xacro files:

* ''xacro/robot.urdf.xacro'' - top-level robot assembly file.
* ''xacro/robot_core.xacro'' - chassis and base links.
* ''xacro/robot_wheels.xacro'' - drive wheels and Gazebo diff-drive plugin.
* ''xacro/robot_castor.xacro'' - castor wheel definition.
* ''xacro/sensor_imu.xacro'' - IMU and magnetometer links/sensors.
* ''xacro/sensor_lidar.xacro'' - LiDAR link and simulated scan sensor.
* ''xacro/sensor_depth_camera.xacro'' - depth camera and optical frame.
* ''xacro/utils_inertial.xacro'' and ''xacro/utils_colors.xacro'' - reusable inertial and visual macros.

== Launch File ==

=== launch/model.launch.py ===

This launch file generates the URDF from xacro and starts ''robot_state_publisher''.

Launch arguments:

* ''use_sim_time'' - enables simulation clock when ''true''. Default: ''false''.

Behavior:

* Processes ''fejemis_description::xacro/robot.urdf.xacro'' with xacro.
* Passes ''fixed_wheels:=<use_sim_time>'' into xacro.
* Publishes ''robot_description'' parameter to ''robot_state_publisher''.
* Publishes the model TF tree for downstream packages.

== Model Composition ==

The top-level model in ''robot.urdf.xacro'' assembles the robot in this order:

* Core chassis: ''xacro:core''
* Drive wheels: ''xacro:wheels''
* Castor wheel: ''xacro:castor''
* IMU and magnetometer: ''xacro:imu_sensor''
* LiDAR: ''xacro:lidar''
* Depth camera: ''xacro:depth''

There is also an optional camera macro (currently commented in the top-level xacro).

== Main Links and Frames ==

Common links/frames provided by the description:

* ''base_link'' - primary base frame for navigation and odometry integration.
* ''chassis'' - main physical body link.
* ''left_wheel'' and ''right_wheel'' - drive wheel links.
* ''laser_frame'' - LiDAR mounting and scan frame in simulation.
* ''imu_link'' - IMU and magnetometer frame.
* ''depth_link'' and ''depth_link_optical'' - depth camera body and optical frame.

These frames are consumed by mapping/localisation and simulation bridge layers.

== Simulation-Specific Behavior ==

The wheel macro supports both fixed and rotating wheel joints:

* Real robot path: wheel joints are fixed in the model launch context.
* Simulation path: wheels are set to continuous joints when simulation mode is enabled.

Gazebo systems configured in ''robot_wheels.xacro'':

* ''gz::sim::systems::DiffDrive''
* ''gz::sim::systems::JointStatePublisher''

Diff-drive plugin settings include:

* Wheel separation: ''0.3847''
* Wheel diameter: ''0.2''
* Command topic: ''/model/fejemis/cmd_vel''
* Odometry topic: ''/model/fejemis/odom''
* Frame IDs: ''odom'' and ''base_link''

Drive wheel friction is increased in simulation to reduce slip, while castor behavior is defined separately in the castor xacro.

== Sensor Simulation Topics ==

The description also defines simulated sensor outputs used by the bridge layer:

* LiDAR: ''/model/fejemis/scan''
* IMU: ''/model/fejemis/imu''
* Magnetometer: ''/model/fejemis/mag''
* Depth camera: ''/model/fejemis/depth_camera''

These topics are later bridged into ROS topics by ''fejemis_sim''.

== Typical Usage ==

Start robot description publisher:

```bash
ros2 launch fejemis_description model.launch.py
```

Start with simulation time:

```bash
ros2 launch fejemis_description model.launch.py use_sim_time:=true
```

In most full-system runs, this launch file is included by top-level bringup (for example in simulation launch stacks).

== Relationship To Other Packages ==

* ''fejemis_sim'' uses this package to spawn the robot from ''/robot_description''.
* ''fejemis_maploc'' and Nav2 depend on the frame structure defined here.
* Sensor and odometry pipelines assume the link names and frame conventions from this model.

Fejemis Description ROS2 - Revision history

S253809: /* Typical Usage */