Simulation

The genbu_simulator package provides a Gazebo simulation environment for the Genbu robot.

Prerequisites

  • ROS 2 (Jazzy or later)
  • ros_gz_sim, ros_gz_bridge packages
  • genbu_description package
  • nav2_bringup, slam_toolbox packages (required for the navigation stack)

Launching the Simulation

Simulation Only

Use sim_bringup.launch.xml to start just the simulator without the navigation stack:

ros2 launch genbu_simulator sim_bringup.launch.xml

This launch file:

  1. Starts the Gazebo simulator with the selected world.
  2. Launches the robot state publisher (with use_sim_time:=true).
  3. Spawns the Genbu robot into the simulation.
  4. Bridges sensor and control topics between Gazebo and ROS 2.

Simulation with Navigation Stack

Use sim_navigation.launch.xml to start the full stack — Gazebo, SLAM Toolbox, Nav2, and RViz — in a single command:

ros2 launch genbu_simulator sim_navigation.launch.xml

This launch file:

  1. Starts the Gazebo simulator with the maze world (default).
  2. Launches the robot state publisher and joint state publisher.
  3. Spawns the Genbu robot into the simulation.
  4. Bridges sensor and control topics between Gazebo and ROS 2.
  5. Starts SLAM Toolbox in online async mode for simultaneous localization and mapping.
  6. Starts the Nav2 navigation stack (planner, controller, behavior trees, and lifecycle manager).
  7. Opens RViz with the navigation configuration.

Launch Arguments

sim_bringup.launch.xml

Argument Default Description
world default Name of the world file to load (see Available Worlds).
robot_name genbu Name assigned to the spawned robot entity in Gazebo.

sim_navigation.launch.xml

Argument Default Description
world maze Name of the world file to load. Defaults to the maze world for navigation testing.
use_sim_time true Use simulation clock for all nodes.

Selecting a World

Pass the world argument to choose a different simulation environment:

ros2 launch genbu_simulator sim_bringup.launch.xml world:=obstacle_course

ros2 launch genbu_simulator sim_navigation.launch.xml world:=obstacle_course

Available Worlds

World Description
default Empty flat plane with directional lighting. Good for basic bring-up testing.
maze 3×3 maze environment. Default world for navigation stack testing.
obstacle_course Flat plane populated with box pillars and cylinders placed around the robot's starting position to exercise obstacle detection and navigation.

Once sim_navigation.launch.xml is running, RViz opens automatically with the navigation configuration.

Sending a Navigation Goal

  1. In RViz, click the Nav2 Goal (or 2D Goal Pose) button in the toolbar.
  2. Click and drag in the map view to set the desired goal position and orientation.
  3. The robot will plan a path and drive to the goal autonomously.

TF Tree

The full TF tree when running with the navigation stack:

map            ← published by SLAM Toolbox
└── odom       ← bridged from Gazebo DiffDrive plugin
    └── base_footprint
        └── base_link
            ├── left_wheel_link
            ├── right_wheel_link
            ├── front_wheel_link
            ├── gyro_link
            └── rplidar_base_link
                └── rplidar_laser_link

/goal_pose  (RViz Nav2 Goal tool)
    → bt_navigator → /plan → controller_server
                           → /cmd_vel_nav → velocity_smoother
                                          → /cmd_vel → Gazebo DiffDrive

ROS 2 Topics

Simulation Topics (always available)

Topic Type Description
/scan sensor_msgs/msg/LaserScan Lidar scan data bridged from the Gazebo GPU lidar sensor.
/odom nav_msgs/msg/Odometry Odometry bridged from the Gazebo DiffDrive plugin.
/tf tf2_msgs/msg/TFMessage Transform frames bridged from Gazebo (odom → base_footprint).
/clock rosgraph_msgs/msg/Clock Simulation clock bridged from Gazebo.
/cmd_vel geometry_msgs/msg/Twist Velocity commands forwarded to the Gazebo DiffDrive plugin.
/robot_description std_msgs/msg/String URDF published by the robot state publisher.
Topic Type Description
/map nav_msgs/msg/OccupancyGrid Occupancy grid map built by SLAM Toolbox.
/goal_pose geometry_msgs/msg/PoseStamped Navigation goal set via RViz or published directly.
/plan nav_msgs/msg/Path Planned path from the current position to the goal.
/cmd_vel_nav geometry_msgs/msg/Twist Velocity commands from the Nav2 controller before smoothing.

Notes

WSL / Non-NVIDIA Environments

The sim_bringup.launch.xml file automatically sets the following environment variables to enable Mesa software rendering when a hardware GPU is not available (e.g. WSL or CI environments):

Variable Value
LIBGL_ALWAYS_SOFTWARE 1
GALLIUM_DRIVER llvmpipe

No extra configuration is required; the launch file handles this automatically.