mo-ah / keepout_zones_ros2

SOFAR course's assignment (UniGE) - NAV2: Keepout Zones in a simulation environment using ROS2

Ros2 + Nav2: Keepout zones in a simulated environment

Introduction

Navigation in ROS2 with Nav2 introduced a lot of new features and possibilities. The goal of this ros2 package is to test the feature of navigating in a known environment where the robot cannot pass by some dangerous areas (keepout zones). The goal of this assignment is to apply Nav2, in particular to understand how to use the costmap filter to set up keepout zones. We implemented a 3D model of the mobile robot TIAGo in order to run in a personalized 3D world, built using Webots simulator. Furthemore, a 2D map is passed to Nav2 through the use of the Map Server node.

Installation

This package requires a distribution of Ros2 installed, together with the Navigation2 stack and the Webots simulator.

Install the Nav2 stack:

sudo apt install ros-<ros2-distro>-navigation2

Install Webots:

sudo snap install webots

sudo apt update

sudo apt install ros-<ros2-distro>-webots-ros2

In order to get and build the package, the following commands can be used:

mkdir -p ~/keepout_ws/src

cd ~/keepout_ws/src

git clone https://github.com/Mo-AH/keepout_zones

cd ~/keepout_ws

colcon build --symlink-install 

Source the workspace by adding the following line to the .bashrc script.

source ~/keepout_ws/install/local_setup.bash

Run

Once the package has been built and sourced, the simulation can be runned with the following command, that runs the main launch:

ros2 launch keepout_zones robot_launch.py

This will start the simulation with a default mask for the keepout zones. The package provides three additional masks in the maps folder, that can be tested with a line like this:

ros2 launch keepout_zones robot_launch.py mask:=src/keepout_zones/maps/mask1.yaml

The robot initial pose is already set by a script (inital_pose.py) launched by robot_launch.py and to test the robot navigation with the keepout zones, a goal can be set in Rviz with the Nav2 Goal button.

Nodes

1. Navagation_launch_file_nodes:

• Nav2_Controller: This is a Task Server in Nav2 that implements the nav2_msgs::action::FollowPath action server which is responsible for generating command velocities for the robot ,given the computed path from the planner module in nav2_planner.
• Nav2_recoveries: Package that implements a module for executing simple controlled robot movements such as rotating on its own axis or moving linearly.
• BT_navigator(Behavior Tree Navigator): This module implements the NavigateToPose task interface. It is a Behavior Tree-based implementation of navigation that is intended to allow for flexibility in the navigation task and provide a way to easily specify complex robot behaviors.
• Nav2_Waypoint_Follower: It is a waypoint following program used if you need to go to a given location and complete a specific task, that is to take a given set of waypoints and navigate to a set of positions in the order provided in the action request. The last waypoint in the waypoint array is the final position.
• Nav2_Planner: This is a planning module which implements the nav2_behavior_tree::ComputePathToPose interface which is responsible for generating a feasible path, given start and end robot poses.

2. slam_launch and localization files

• Map_Server: The Map Server provides maps to the rest of the Nav2 system using both topic and service interfaces.
• nav2_amcl: Adaptive Monte Carlo Localization (AMCL) is a probabilistic localization module which estimates the position and orientation (i.e. Pose) of a robot in a given known map.

3. bringup_lanuch (file used for control the whole navigation and localization codes)

• costmap_filter_info_server: This is used for filter map which is drawn to be kept out when the robot moves ub the map.
• nav2_lifecycle_manager: This is used to allows the system startup to ensure that all required nodes have been instantiated correctly before they begin their execution. Using lifecycle nodes also allows nodes to be restarted or replaced on-line and this is used in all nodes.

4. robot_launch_file

• This file is used for launching the Rviz, tiago robot, the map without keepoutzones, webots environment and bringup file which is responsible for the navigation and keepout zones

rqt_graph

UML model