Modify Gigatron launch file to include rear LIDAR

[DJGCrusader]

I changed the URDF. We should now include these changes in the launch file. DO THE THING!

[5yler]

The RPLIDAR will be used as the front LIDAR, and the XV will go on the back. We have a laser filter set up to only publish the front 180˚ of points in laser_filters.launch, but that currently only filters the front-facing scan.

To use the data from both LIDARs for localization see Using multiple LaserScan (ROS Answers):

Normally, it should not be a problem when both lasers publish their data on the same topic since the LaserScan message contains a header with a frame_id and a time stamp. Of course, this requires a valid TF tree and the laser drivers to be configured to use a different frame id for each scanner. Amcl, for instance, supports several lasers on one topic. On our robot, we use two Hokuyo lasers for amcl. Both laser drivers publish on separate topics and in the amcl node, we relay both topics to amcl's input topic using topic_tools' relay. That way, we can access the laser scans separately or, if needed, on one single topic.

The final setup here should be:

• [x] RPLIDAR with link laser_link and topic scan_rp with 180˚ scan published to topic scan_front
• [x] XV with link back_laser_link should publish on topic scan_xv with 180˚ scan published to scan_back
• [x] scan_front and scan_back topics both republished to scan topic for use in localization

If we go with the reactive controller for the race, we will use the scan_front topic for steering.

[5yler]

Still need to get scan_front and scan_back combined on the same topic with relay from topic_tools

[DJGCrusader]

ISSUE CLOSED.