PILZ safety laser scanner PSENscan

Package: psen_scan_v2

The psen_scan_v2 package is a ROS integration driver for the PSENscan safety laser scanner product. It lets you integrate the laser scanner data into your ROS Environment easily. Using the standard [sensor_msgs/LaserScan][] message format ensures compatibility with other laserscan-post-processing nodes such as [gmapping][]. For a general overview, link collection and tutorials we refer to the ROS wiki page.

PSENscan firmware >= 3.1.0 is supported on the following models:

C++ standalone library

If you are interested in using the PSENscan safety laser scanner without ROS, please take a look at our C++ standalone library. You can read more about it in the standalone folder

Table of Contents

1. Installation
2. Usage
   • Parameters
   • Optional Parameters
   • Expert Parameters (optional)
   • Published Topics
   • TF Frames
   • Defining the scan range
   • Timestamp details
   • Importing the zoneset configuration
   • Visualizing the active zoneset
3. Developer Information
   • Build Status
   • Branching model
   • Test concept
4. Migration

Installation

Needed Equipment: - PSENscan safety laser scanner - ROS Machine

To use the package, you can install prebuilt packages with

sudo apt install ros-$ROS_DISTRO-psen-scan-v2

Usage

To start reading data from the safety laser scanner and publishing scans execute roslaunch psen_scan_v2 psen_scan_v2.launch in a command line. This will launch the ROS Node with the default configuration.

If you wish to set parameters from the command line, add them to the end of the command as parameter:=value, separated by spaces.

roslaunch psen_scan_v2 psen_scan_v2.launch sensor_ip:=192.168.0.10

This example configures the safety laser scanner at 192.168.0.10 to send it´s frames to the ROS node at localhost.

In order to create an application with your own launch file, you can include the bringup.launch, where you can easily adjust the configuration parameters. A more detailed explanation can be found in the tutorials.

Parameters

sensor_ip (string, default: "192.168.0.10")
IP-Address of safety laser scanner.

Optional Parameters

tf_prefix (string, default: "laser_1")
Name of this scanner that can be changed to differentiate between multiple devices. By convention this is used as tf prefix.

angle_start (double, default: -2.398 (= -137.4 deg))
Start angle of measurement. (Radian)

angle_end (double, default: 2.398 (= 137.4 deg))
End angle of measurement. It is included in the measurements. (Radian)

intensities (bool, default: false)
Publish intensities. If this is enabled, the resolution needs to be increased (at least 0.2 deg).

resolution (double, default: 0.0017 (= 0.1 deg))
Scan angle resolution. (Radian) The value is rounded to a multiple of 0.1 deg and has to be in the range [0.1, 10] degrees.

config_file (string, default: "") Full path to a scanner config file. If a file is provided the configured zonesets and active zone marker are published, see here for more information.

Expert Parameters (optional)

host_ip (string, default: "auto")
IP-Address of host machine. The IP of the local machine is used by default.

host_udp_port_data (int, default: 55115)
UDP Port on which monitoring frames (scans) should be received.

host_udp_port_control (int, default: 55116)
UDP Port used to send commands (start/stop) and receive the corresponding replies.

fragmented_scans (bool, default: false)
Publish scan data as soon as a UDP packet is ready, do not wait for a full scan.

rviz (bool, default: true)
Start a preconfigured rviz visualizing the scan data.

Published Topics

/<name>/scan ([sensor_msgs/LaserScan][])

• If fragmented_scans is set to false (default) the driver will publish complete scan rounds from the PSENscan safety laser scanner as a single message.
• If fragmented_scans is enabled the driver will send the measurement data as soon as they arrive, instead of waiting for the scan round to be completed. This way the scan data is received sooner but is split into several sensor messages.
• Hint 1: Scan rounds and fragments that contain no measurement data are not published. This can happen with smaller scan ranges.
• Hint 2: Frequency of the laser scan messages is about 33hz for the combined and 200hz for the fragmented scans.

/<name>/zoneconfiguration (psen_scan_v2/ZoneSetConfiguration)

• Hint 1: Will not be advertised if no config_file is provided.

/<name>/active_zoneset ([std_msgs/UInt8][])

• This topic contains the id of the currently active zoneset of the PSENscan safety laser scanner.

• Hint 1: If no zonesets are configured the driver will publish "0" as default.

/<name>/active_zoneset_marker ([visualization_msgs/Marker][])

• The markers published represent the currently active zoneset as triangle lists. They can be viewed e.g. in rviz.

• Hint 1: Uses the topics /<name>/zoneconfiguration and /<name>/active_zoneset to calculate the vizualization and updates in the same frequency as those topics.

• Hint 2: Will not be advertised if no config_file is provided.

TF Frames

The location of the TF frames is shown in the image below. These names are defined by the aforementioned launchfile parameter name. Changing them is necessary for instance when running multiple scanners.

Defining the scan range

You can adjust the scan field to your needs by changing angle_start and angle_end. The published ([sensor_msgs/LaserScan][]) will only contain data within the given angle limits. Both limits are defined within the laser_1 frame as shown in the image below.

Timestamp details

The timestamps of the scan data published are computed to be close to reality and processing speed of incoming data was optimized to reduce the time for the scan data to be published. This should suffice for localization and slam algorithms. If you application benefits from getting the scan data any sooner there are two possibilities:

• Use fragmented scans. This will publish the individual frames received by the PsenScan hardware immediately instead of waiting for a scan round to be completed and combined to a single laser scan message.
• Use the tcp_nodelay flag in your ROS subscriber. This will disable the nagle's algorithm, which is a TCP optimization. This algorithm can produce a jitter of about 20ms in the ros topic.
  • The cpp API of ROS does not support disabling this on the publisher side. If you don't have control over the subscriber e.g. due to using a third party package you can create a python node which acts as a repeater for the scan topic. rospy subscriber and publisher both allow setting this flag and thus can disable it for this driver and the third party package.

Importing the zoneset configuration

Once you setup the scanner and created a configuration according to our tutorial you can use an exported xml configuration file within ROS. The configured zonesets will be published.

The zonesets you created in the Pilz configurator:

will be exactly the same in ROS:

You can try this out with:

roslaunch psen_scan_v2 psen_scan_v2.lauch config_file:='full_path_to/example_config.xml'

If you want to use the configuration node in your launchfile add a section such as:

<node ns="$(arg laser_ns)" name="config_server_node_$(arg laser_ns)" type="config_server_node" pkg="psen_scan_v2">
  <param name="config_file" value="$(arg config_file)" />
  <param name="frame_id" value="$(arg frame_id)" />
</node>

Visualizing the active zoneset

For visualizing the active zoneset in RViz you can run the active_zoneset_node. It will publish markers on the /<name>/active_zoneset_marker topic like shown in the RViz screenshot above.

Developer Information

Build Status

Platform	Melodic	Noetic
CI
Buildfarm src
Buildfarm bin

Branching model

main is considered to be the active development branch, it targets the ROS distributions melodic and noetic.

Test concept

Migration

To update your ROS environment from the former psen_scan package (which supported firmware versions up to 3.0), please execute the following steps: 1. Update scanner firmware using PSENscan Configurator (unless the device has firmware 3.1 already) 2. Install the new ROS package sudo apt install ros-$ROS_DISTRO-psen-scan-v2 3. Replace the launch file arguments: * password and x_axis_rotation are obsolete and should be dropped * angle_start and angle_end are now in radians, in direction of the x axis of the scanner tf frame * prefix is replaced by tf_prefix 4. In your application launch file / roslaunch command: replace all occurrences of psen_scan with psen_scan_v2

You need further information?

Our international hotline staff will support you individually about our ROS packages at ros@pilz.de

Find more information about the PILZ safety laser scanner on the product website.

Visit us at pilz.com

PILZ is an international-scale, innovative automation technology company. PILZ uses its solutions to create safety for man, machine and the environment. In addition to head office in Ostfildern near Stuttgart, the family business is represented over 2,400 employees at 42 subsidiaries and branches on all continents.

The company’s products include sensor technology, electronic monitoring relays, safety relays, configurable and programmable control systems, automation solutions with motion control, systems for industrial communication as well as visualization solutions and operator terminals.

PILZ solutions can be used in all areas of mechanical engineering, including the packaging and automotive sector, plus the railway technology, press and wind energy sectors. These solutions ensure that baggage handling systems run safely at airports and funiculars or roller coasters travel safely; they also guarantee fire protection and energy supply in buildings.

[sensor_msgs/LaserScan]: http://docs.ros.org/noetic/api/sensor_msgs/html/msg/LaserScan.html [std_msgs/UInt8]: https://docs.ros.org/en/api/std_msgs/html/msg/UInt8.html [visualization_msgs/Marker]: https://docs.ros.org/en/noetic/api/visualization_msgs/html/msg/Marker.html [gmapping]: http://wiki.ros.org/gmapping