ITS Path Planner ROS 2 Navigation Plugin#

Intelligent Sampling and Two-Way Search (ITS) global path planner is an Intel® patented algorithm.

The ITS Plugin for the ROS 2 Navigation 2 application plugin is a global path planner module that is based on Intelligent sampling and Two-way Search (ITS).

ITS is a new search approach based on two-way path planning and intelligent sampling, which reduces the compute time by about 20x-30x on a 1000 nodes map comparing with the A* search algorithm. The inputs are the 2D occupancy grid map, the robot position, and the goal position.

It does not support continuous replanning.

Prerequisites: Use a simple behavior tree with a compute path to pose and a follow path.

ITS planner inputs:

  • global 2D costmap (nav2_costmap_2d::Costmap2D)

  • start and goal pose (geometry_msgs::msg::PoseStamped)

ITS planner outputs: 2D waypoints of the path

Path planning steps summary:

  1. The ITS planner converts the 2D costmap to either a Probabilistic Road Map (PRM) or a Deterministic Road Map (DRM).

  2. The generated roadmap is saved as a txt file which can be reused for multiple inquiries.

  3. The ITS planner conducts a two-way search to find a path from the source to the destination. Either the smoothing filter or a catmull spline interpolation can be used to create a smooth and continuous path. The generated smooth path is in the form of a ROS 2 navigation message type (nav_msgs::msg).

For customization options, see ITS Path Planner Plugin Customization.

Source Code#

The source code of this component can be found here: ITS-Planner

Getting Started#

Autonomous Mobile Robot provides a ROS 2 Deb package for the application, supported by the following platform:

  • ROS version: Jazzy, Humble

Prerequisites#

Complete the get started guide before continuing.

Install Deb package#

Install the ros-jazzy-its-planner Deb package from the Intel® Autonomous Mobile Robot APT repository

sudo apt install ros-jazzy-its-planner

sudo apt install ros-humble-its-planner

Run the following script to set environment variables:

source /opt/ros/jazzy/setup.bash
export TURTLEBOT3_MODEL=waffle_pi
export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:/opt/ros/jazzy/share/turtlebot3_gazebo/models

source /opt/ros/humble/setup.bash
export TURTLEBOT3_MODEL=waffle_pi
export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:/opt/ros/humble/share/turtlebot3_gazebo/models

To launch the default ITS planner which is based on differential drive robot, run:

ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False params_file:=/opt/ros/jazzy/share/its_planner/nav2_params.yaml default_bt_xml_filename:=/opt/ros/jazzy/share/its_planner/navigate_w_recovery.xml

ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False params_file:=/opt/ros/humble/share/its_planner/nav2_params.yaml default_bt_xml_filename:=/opt/ros/humble/share/its_planner/navigate_w_recovery.xml

ITS Planner also supports Ackermann steering; to launch the Ackermann ITS planner run:

ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False params_file:=/opt/ros/jazzy/share/its_planner/nav2_params_dubins.yaml default_bt_xml_filename:=/opt/ros/jazzy/share/its_planner/navigate_w_recovery.xml

ros2 launch nav2_bringup tb3_simulation_launch.py headless:=False params_file:=/opt/ros/humble/share/its_planner/nav2_params_dubins.yaml default_bt_xml_filename:=/opt/ros/humble/share/its_planner/navigate_w_recovery.xml

Note:

The above command opens Gazebo* and rviz2 applications. Gazebo* takes a longer time to open (up to a minute) depending on the host’s capabilities. Both applications contain the simulated waffle map, and a simulated robot. Initially, the applications are opened in the background, but you can bring them into the foreground, side-by-side, for a better visual.

  1. Set the robot 2D Pose Estimate in rviz2:

    1. Set the initial robot pose by pressing 2D Pose Estimate in rviz2.

    2. At the robot estimated location, down-click inside the 2D map. For reference, use the robot pose as it appears in Gazebo*.

    3. Set the orientation by dragging forward from the down-click. This also enables ROS 2 navigation.

    2d_pose_estimate

  2. In rviz2, press Navigation2 Goal, and choose a destination for the robot. This calls the behavioral tree navigator to go to that goal through an action server.

    set_navigation_goal

    path_created

    Expected result: The robot moves along the path generated to its new destination.

  3. Set new destinations for the robot, one at a time.

    goal_achived_gazebo_rviz

  4. To close this, do the following:

    • Type Ctrl-c in the terminal where you did the up command.

# ITS Path Planner Plugin Customization

The ROS 2 navigation bring-up application is started using the TurtleBot 3 Gazebo simulation, and it receives as input parameter its_nav2_params.yaml.

To use the ITS path planner plugin, the following parameters are added in its_nav2_params.yaml:

> `yaml > planner_server: >   ros__parameters: >     expected_planner_frequency: 0.01 >     use_sim_time: True >     planner_plugins: ["GridBased"] >     GridBased: >       plugin: "its_planner/ITSPlanner" >       interpolation_resolution: 0.05 >       catmull_spline: False >       smoothing_window: 15 >       buffer_size: 10 >       build_road_map_once: True >       min_samples: 250 >       roadmap: "PROBABLISTIC" >       w: 32 >       h: 32 >       n: 2 > `

## ITS Path Planner Plugin Parameters

`bash catmull_spline: `

If true, the generated path from the ITS is interpolated with the catmull spline method; otherwise, a smoothing filter is used to smooth the path.

`bash smoothing_window: `

The window size for the smoothing filter (The unit is the grid size.)

`bash buffer_size: `

During roadmap generation, the samples are generated away from obstacles. The buffer size dictates how far away from obstacles the roadmap samples should be.

`bash build_road_map_once: `

If true, the roadmap is loaded from the saved file; otherwise, a new roadmap is generated.

`bash min_samples: `

The minimum number of samples required to generate the roadmap

`bash roadmap: `

Either PROBABILISTIC or DETERMINISTIC

`bash w: `

The width of the window for intelligent sampling

`bash h: `

The height of the window for intelligent sampling

`bash n: `

The minimum number of samples that is required in an area defined by w and h

You can modify these values by editing the file below for the default ITS planner, at lines 274-291:

::::{tab-set} :::{tab-item} Jazzy :sync: tab1

`bash /opt/ros/jazzy/share/its_planner/nav2_params.yaml `

::: :::{tab-item} Humble :sync: tab2

`bash /opt/ros/humble/share/its_planner/nav2_params.yaml `

:::#

You can modify these values by editing the file below for the Ackermann ITS planner, at lines 274-296:

::::{tab-set} :::{tab-item} Jazzy :sync: tab1

`bash /opt/ros/jazzy/share/its_planner/nav2_params_dubins.yaml `

::: :::{tab-item} Humble :sync: tab2

`bash /opt/ros/humble/share/its_planner/nav2_params_dubins.yaml `

:::#

Troubleshooting#

For general robot issues, refer to Troubleshooting.