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 dependencies required to run simulations:

sudo apt install ros-jazzy-turtlebot3-gazebo

sudo apt install ros-humble-turtlebot3-gazebo

Install the ITS Path 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
export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:/opt/ros/jazzy/share/turtlebot3_gazebo/models

source /opt/ros/humble/setup.bash
export TURTLEBOT3_MODEL=waffle
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 its_planner its_differential_launch.py use_sim_time:=true

ros2 launch its_planner its_differential_launch.py use_sim_time:=true

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

ros2 launch its_planner its_ackermann_launch.py use_sim_time:=true

ros2 launch its_planner its_ackermann_launch.py use_sim_time:=true

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 nav2_params_jazzy.yaml.

To use the ITS path planner plugin, the following parameters are added in nav2_params_jazzy.yaml:

planner_server:
  ros__parameters:
    expected_planner_frequency: 20.0
    use_sim_time: True
    planner_plugins: ["GridBased"]
    costmap_update_timeout: 1.0
    GridBased:
      plugin: "its_planner/ITSPlanner"
      interpolation_resolution: 0.05
      catmull_spline: False
      smoothing_window: 15
      buffer_size: 10
      build_road_map_once: True
      enable_k: False
      min_samples: 250
      roadmap: "PROBABLISTIC"
      w: 32
      h: 32
      n: 2

The ROS 2 navigation bring-up application is started using the TurtleBot 3 Gazebo simulation and it receives as input parameter nav2_params_humble.yaml.

To use the ITS path planner plugin, the following parameters are added in nav2_params_humble.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
      enable_k: False
      min_samples: 250
      roadmap: "PROBABLISTIC"
      w: 32
      h: 32
      n: 2

ITS Path Planner Plugin Parameters#

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.

smoothing_window:

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

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.

build_road_map_once:

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

min_samples:

The minimum number of samples required to generate the roadmap

roadmap:

Either PROBABILISTIC or DETERMINISTIC

w:

The width of the window for intelligent sampling

h:

The height of the window for intelligent sampling

n:

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

ITS Path Planner Plugin Parameters modification#

Default ITS Planner#

You can modify plugin parameters by editing the planner_server section in the configuration file below for the default ITS planner:

/opt/ros/jazzy/share/its_planner/nav2_params_jazzy.yaml

/opt/ros/humble/share/its_planner/nav2_params_humble.yaml

Ackermann ITS Planner#

You can modify plugin parameters by editing the planner_server section in the configuration file below for the Ackermann ITS planner:

/opt/ros/jazzy/share/its_planner/nav2_params_dubins_jazzy.yaml

/opt/ros/humble/share/its_planner/nav2_params_dubins_humble.yaml

Troubleshooting

For general robot issues, refer to Troubleshooting.