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How to set up ROS to communicate with the scanner

Description: You learn how to set up the PILZ laser scanner with ROS and show the result in Rviz.

Keywords: PSENscan, psen_scan

Tutorial Level: BEGINNER

Next Tutorial: Launching multiple scanners

Introduction

This tutorial teaches you to set up and launch the ROS driver for the PSENscan laser scanner. This includes creating a new ROS package to read and display laser scanner data.

Prerequisites

In order to complete this tutorial, you need the following:

• A workstation or a Virtual machine with Ubuntu 18.04 LTS and ROS melodic installed.

• Completed the first ROS tutorial create a catkin workspace.

• An operable catkin workspace.
• An installed PSENscan package.

  sudo apt update
  sudo apt install ros-melodic-psen-scan

Create a ROS package with the required files

Install the psen_scan package as in the previous tutorials described.

In your workspace, create a new package:

cd ~/catkin_ws/src
catkin_create_pkg --rosdistro melodic psen_scan_tutorials psen_scan
cd psen_scan_tutorials
mkdir config
gedit config/scanner_config.yaml

Copy the following content and paste it into gedit. Do not forget to save the new created file.

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Like in the last step create the file psen_scan_tutorials/launch/psen_scan.launch with the following content by using gedit:

mkdir launch
gedit launch/psen_scan.launch

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The code explained:

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This starts the psen_scan_node and loads the newly created config file.

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This starts rviz with a predefined configuration.

Required parameters

To launch the ROS driver, the following parameters are mandatory:

• password

  The password is required to establish communication with the scanner. The password has to be encrypted. The default encrypted value is ac0d68d033.

• sensor_ip The IP of the laser scanner in the network. You have configured this in the first tutorial using the configuration tool.

• host_ip

  The IP under which the scanner can reach your PC and will send UDP packages to. It needs to be in the same subnet as the aforementioned sensor_ip. We suggest setting this IP statically for the appropriate network interface.

• host_udp_port

  Similar to the host_ip this is used for the scanner to reach your PC. It needs to be accessible by the scanner, so make sure it is not blocked by a firewall and the scanner can reach it.

For an overview of all parameters, please visit https://github.com/PilzDE/psen_scan/blob/melodic-devel/README.md#ros-api

Start the PSENscan application

Now you can launch your newly created launchfile with the following command:

roslaunch psen_scan_tutorials psen_scan.launch

This should launch rviz and look something like this:

The red lines show the detected surroundings of the scanner.

For comparison in reality the scanner was placed in an arrangement more or less like this:

Conclusion

In this tutorial you created a basis for an application using the PSENscan laser scanner together with ROS. In the next tutorial you learn how to connect to multiple scanners.