lightsensor_gazebo

A trivial "light sensor" for Gazebo under ROS, which traverses the world calculating angles to specially marked models and producing an array of pixel values from the extents of those models.

Lacking an omnidirectional camera sim, and realising any sim would be far too slow for my purposes, I realised my application just needs to head toward or away from different coloured lights.

This plugin provides that functionality. It traverses the models in the world, looking for those with names of the form "lightrgbXXX" where XXX is a hexadecimal RGB colour. The relative angle and distance of the "light" is taken into account, and a buffer of RGB pixels - a virtual omnidirectional planar camera - is built up. This is then broadcast on a ROS topic. The simulation is entirely 2D (in the XY plane) and there is no occlusion. If multiple lights overlap a sensor, they are added together (with each colour channel clamped at 255).

Output

The output is published on the light topic by default, is of type LightSensor, which is an array of Pixel, which is 3 uint8 values (r,g,b). The middle value is the front sensor, with the first half of the values covering the left side and the second half covering the right side of the robot.

watch.py

This script, which requires pygame, displays the light topic as a circle of coloured squares. It's a useful example of working with the output.

watch_node

This is a C++ program which monitors both the lightsensor and the sonars using the wheelyPioneer rendering code.

Elements

• robotNamespace - the namespace for the broadcast topic (default none)
• interval - the update interval in seconds (default 0.1)
• bodyName - the name of the link to which the sensor is attached (required)
• topic - the broadcast topic (default light)
• pixels - the resolution of the sensor, as the number of pixels (default 10)

Example URDF

This attaches a light sensor to a robot which has a link called base_link:

  <gazebo>
    <plugin name="lightsensor" filename="liblightsensor_gazebo.so">
      <link name="base_link"/>
      <interval>0.1</interval>
      <pixels>100</pixels>
    </plugin>
  </gazebo>