Autonomous Navigation with Nav2

Learning Objectives

By the end of this lesson, you will be able to:

• Understand what Nav2 is and its role in robot navigation
• Know the main components of Nav2 and how they work together
• Set up and configure Nav2 for robot navigation
• Use Nav2 to enable autonomous robot movement

Nav2 Overview

Nav2 is a comprehensive navigation framework that provides:

• Software package for achieving autonomous robot movement
• Functions such as path planning, obstacle avoidance, and movement to target locations
• A widely used standard navigation system for ROS2
• Integration with various sensors and robot platforms

1. What is Nav2

Nav2 is a standard navigation system for ROS2. It provides the functions necessary for robots to move autonomously within an environment.

Main Features of Nav2

• Path Planning: Plans optimal paths from current position to target location
• Obstacle Avoidance: Detects and avoids obstacles using sensor data
• Position Estimation: Estimates the robot’s current position and orientation
• Movement to Target Location: Moves the robot along the planned path

Advantages of Nav2

• Open Source: Free to use
• Scalability: Compatible with various robot platforms
• Flexibility: Customizable parameter settings
• Active Community: Many developers use and improve it

2. Basic Structure of Nav2

Nav2 consists of the following main components:

Core Components

• Controller Server: Controls robot movement
• Planner Server: Handles path planning
• Behavior Server: Executes special behaviors (rotation, waiting, etc.)
• BT Navigator: Manages navigation behaviors
• Waypoint Follower: Visits multiple target locations in sequence
• Velocity Smoother: Smooths robot movement

Auxiliary Components

• Lifecycle Manager: Manages the state of each component
• Map Server: Provides environment maps
• Costmap: Manages costmaps containing obstacle information

3. How to Use Nav2

Prerequisites

• ROS2 Humble is installed
• Robot sensors (LiDAR, camera, etc.) are configured
• Environment map is created

Basic Usage Steps

1. Create Map: Create environment map using SLAM
2. Set Parameters: Adjust Nav2 parameters according to the robot
3. Launch Nav2: Launch Nav2 using launch files
4. Set Target Location: Set target location using tools like RViz
5. Start Navigation: Robot moves autonomously to target location

Important Parameters

• Robot Dimensions: Size and shape of the robot
• Sensor Settings: Parameters for LiDAR and camera
• Speed Limits: Maximum speed and acceleration limits
• Obstacle Avoidance Settings: Safe distance from obstacles, etc.

4. Applications of Nav2

Practical Applications

• Indoor Cleaning Robots: Autonomously clean rooms
• Logistics Robots: Transport items within warehouses
• Guide Robots: Guide and explain within facilities
• Surveillance Robots: Regular patrols and surveillance

Research and Development Applications

• Development of New Navigation Algorithms
• Realization of Multi-Robot Systems
• Cooperative Work Between Humans and Robots
• Autonomous Movement in Unknown Environments

5. Summary

Nav2 is a powerful tool for achieving autonomous robot movement as a standard navigation system for ROS2. It provides functions such as path planning, obstacle avoidance, and movement to target locations, and is used on various robot platforms.

This document explained the basic concepts and usage of Nav2. When using Nav2 with actual robots, it is important to adjust parameters according to the robot’s characteristics and environment to achieve optimal performance.

Exercises

• Launch Nav2

ros2 launch kachaka_nav2_bringup navigation_launch.py

navigation_launch.py

Basic Navigation

1. Use Nav2 in a simple environment to move the robot to a target location
2. Set different target locations and observe the robot’s behavior

Parameter Adjustment

1. Change the robot’s speed and observe the difference in behavior
2. Adjust obstacle avoidance parameters and observe changes in avoidance behavior

Content

Use Nav2 to make the robot follow your favorite path!