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_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 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

## Default ITS planner parameters ::::{tab-set} :::{tab-item} Jazzy :sync: jazzy

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

`bash /opt/ros/jazzy/share/its_planner/nav2_params_jazzy.yaml ` You can modify plugin parameters by editing the planner_server section in nav2_params_jazzy.yaml

> `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 > `

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

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.

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

You can modify plugin parameters by editing the planner_server section in nav2_params_humble.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 >       enable_k: False >       min_samples: 250 >       roadmap: "PROBABLISTIC" >       w: 32 >       h: 32 >       n: 2 > `

:::#

Parameter Descriptions

  • catmull_spline: if true, the generated path from the ITS will be interpolated with catmull spline method; otherwise smoothing filter will be used to smooth the path

  • smoothing_window: window size for the smoothing filter; unit is grid size

  • buffer_size: during the roadmap generation, the samples are generated away from obstacles. The buffer size dictates how far the roadmap samples should be away from obstacles

  • build_road_map_once: If true, the roadmap will be loaded from the saved file, otherwise a new roadmap will be generated

  • min_samples: minimum number of samples required to generate the roadmap

  • roadmap: can be either PROBABLISTIC 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

## Ackermann ITS Planner

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

The ROS 2 navigation bring-up application is started using the TurtleBot 3 Gazebo simulation and it receives as input parameter nav2_params_dubins_jazzy.yaml

`bash /opt/ros/jazzy/share/its_planner/nav2_params_dubins_jazzy.yaml ` You can modify plugin parameters by editing the planner_server section in nav2_params_dubins_jazzy.yaml

> `yaml > planner_server: >   ros__parameters: >     use_sim_time: True >     expected_planner_frequency: 20.0 >     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: 1 >       build_road_map_once: True >       enable_k: False >       min_samples: 250 >       roadmap: "PROBABLISTIC" >       w: 20 >       h: 20 >       n: 2 >       dubins_path: True >       turn_radius: 0.22 >       robot_radius: 0.25 >       yaw_tolerance: 0.125 >       use_final_heading: True > `

::::{tab-set} :::{tab-item} Humble :sync: humble

The ROS 2 navigation bring-up application is started using the TurtleBot 3 Gazebo simulation and it receives as input parameter nav2_params_dubins_humble.yaml.

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

You can modify plugin parameters by editing the planner_server section in nav2_params_dubins_humble.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: 1 >       build_road_map_once: True >       enable_k: False >       min_samples: 250 >       roadmap: "PROBABLISTIC" >       w: 40 >       h: 40 >       n: 2 >       dubins_path: True >       turn_radius: .22 >       robot_radius: .25 >       yaw_tolerance: .125 >       use_final_heading: True > `

Dubins-Specific Parameters - Ackermann ITS planner:

  • dubins_path: If true, the ITS algorithm will utilize Dubins Paths to form a global path that can be followed by an Ackermann steering vehicle.

  • turn_radius: The minimum turning radius of the robot, in world scale.

  • robot_radius: The radius of the robot, in world scale.

  • yaw_tolerance: The amount (+/-) by which the heading angles of the end positions of the intermediate Dubins curves may vary, in radians. Does not apply to the final Goal heading.

  • use_final_heading: Whether to use the goal heading specified by the geometry_msgs::msg::PoseStamped message or not.

Troubleshooting#

For general robot issues, refer to Troubleshooting.