ros2_diff_drive_demo

This repository will help you understand how to control a differential drive robot with ros2_control. There are two main packages used to view and control the robot.

ign_gazebo_robot_package

The package ign_gazebo_robot_package is used to visualize the robot in Gazebo and load the controllers to control the robot. The controller diff_drive_base_controller is used here to control the robot.

command_publisher_package

The package command_publisher_package is used to publish commands for the robot to move around. It uses the message type Twist to send commands. The differential drive robot takes two parameters, the linear position along x axis and angular position along z axis.

yaml

The command publishing package uses yaml file to load commands for the robot to move. The parameter goal_names of type STRING_ARRAY define how many positions has to be passed to the robot. The goal names are then used as parameters to define linear and angular values respectively.

Versions tested

Please find below the versions where the packages have been tested

OS : Ubuntu 20.04
ROS2 : Galactic
Gazebo : Gazebo Edifice

Clone the repository

Open terminal and follow the commands mentioned below

mkdir -p dev_ws/src
cd dev_ws/src

Clone the packages of the repository inside the src folder

Build packages

Make sure to build the package inside dev_ws folder and not inside src folder

 colcon build

Source environment

Source both the underlay and overlay environment

source /opt/ros/galactic/setup.bash
source install/setup.bash

Visualize robot

Visualize the robot in Gazebo by running the following command

ros2 launch ign_gazebo_robot_package diff_drive_example.launch.py

You can view a differential drive robot inside Gazebo

Move the robot

Move the robot by running the following command

ros2 launch command_publisher_package cyclic_command_publisher.launch.py

You can also provide your own number of positions inside the dev_ws/src/command_publisher_package/config/cyclic_diff_drive_params.yaml file. Make sure to build the packages again after editing the yaml file.

References

1. Gazebo Robot
2. Command Publisher