alexbgreat / nox_robot

Nox robot project

Nox Robot project

Nox is a nice (and time-consuming for me) robot which uses SLAM (ROS) with a Kinect to navigate in its environment. It is powered by ROS running on a Raspberry Pi 3B and an Arduino that controls two motors with encoders.

In its current state the robot can use SLAM (gmapping) to create a map of its surroundings (using the Kinect depth perception to detect wall and obstacles) and localize itself within the map. It can plan a path to a given goal and drive to it avoiding obstacles.

Nox characteristics

Nox is a differential drive robot with the motors placed on the same axis. The base is made of wood with two caster wheels for support. The rest of the structure is made mainly of wood and metal brackets, easy to find in any DIY retail store. On the rear part of the robot plates can be stacked to put the electronic boards on. More information (such as components used) can be found in the Hackster page of the project.

Schematics

ROS packages

• nox_description:

This package includes the URDF description of the robot and the associated CAD files for display in RViz. The launch file "nox_rviz.launch" launches the joint and robot state publisher as well as RViz to display the model.

• nox:

This package includes the base controller node "nox_controller.cpp". This node will convert velocity command data into proper command data for the robot (according to the robot kinematic model) and send it to the Arduino Mega (through ROSSerial). It also computes the odometry (with the encoder data and according to the robot kinematic model) from data received from the Arduino Mega. The package also includes several launch files used to start the navigation (see "How to use Nox" below).

• Arduino:

The arduino node receives the command order from the base controller node and commands the motor speeds. It also sends back the encoder data needed for the odometry to the controller node through ROSSerial.

How to use Nox

Packages installation

The software for the Nox project was developped with ROS Kinetic and Ubuntu 16.04. More recent versions should work as well but might require some tweaking. This readme doesn't explain how to install ROS and packages. For more information you can check the ROS tutorials.

To use Nox you will need the following packages (most of them should already be installed by default or requested when building the nox packages):

• The navigation stack,
• The freenect package (for connecting to the Kinect)
• RViz
• TF, Joint State and Robot State Publishers
• ROSSerial package (for connecting to the Arduino Mega)
• SLAM gmapping.
• TEB local planner.

Installation

You can install and build the package by copying the "nox" and "nox_description" folders in "your_catkin_workspace/src" on both your computer and the Raspberry Pi and running:

catkin_make

Running Nox

In order to navigate Nox you will need to start two launch files using SSH and ROS nodes over network.

1. Connect to Nox Wi-Fi

I haven't included in my GitHub the RPi network configuration but basically the RPi creates an Ad-Hoc network I connect to with my computer in order to send SSH commands. It's also possible to connect both the Rpi and the computer to the same WiFi network. Once connected and before launching any ROS command you should sync the RPi to the computer using the following code in RPi:

sudo ntpdate ip_address_of_the_computer

You can also setup the ntpdate or use chrony to do that automatically.

2. Start the odometry and motor control

In the RPi, use the following command to start the main program:

roslaunch nox nox_bringup.launch

It will launch the serial controller node connected to the Arduino, the Kinect node, the odometry calculation node and the joint state publisher. If this step succeded you should see the side light of the robot going from a series of three quick blinks to a slow "breathing-like" type of blinking.

3. Start the navigation

In order to be able to do path planning calculation and mapping you have to use a launch file on your computer this time. Before doing so, assure yourself that you exported the ROS master from the RPi (modify the command to suit your own setup):

export ROS_MASTER_URI=http://localhost:11311

You can then launch:

roslaunch nox nox_slam.launch

It will launch the move_base node and RViz. By using the "2D Nav Goal" arrow you can give a goal for the robot to reach. Alternatively, you can use the ROS teleop keyboard to control the robot:

rosrun teleop_twist_keyboard teleop_twist_keyboard.py

Authors

• Robin Baran - Initial work

License

This project is licensed under the GNU General Public License version 3

Acknowledgments

• Sungjik's project which was the biggest inspiration to make my own robot
• "ROS Navigation Tuning Guide" by Kaiyu Zheng
• "How to connect Kinect to Raspberry Pi 2 or 3 with ROS" Youtube video by Robotics Weekends
• "Communication between Raspberry Pi and PC (ROS)" by mktk1117
• "On Differential Drive Robot Odometry with Application to Path Planning" by Evangelos Papadopoulos and Michael Misailidis
• Turtlebot programs
• Prof. Shuro Nakajima from Wakayama University where I got the occasion to learn by working on the PMV (Personal Mobility Vehicle) project (check it it's awesome)
• Everyone in the ROS community who got the same problems as me and those who answered them