fflaser_deadspots man page

fflaser_deadspots — Calibrate dead spots for the Fawkes laser plugin


fflaser_deadspots [-r host[:port]] [-w sec] [-n N] [-c dist]
                  [-m margin_deg] [-d] [-b] num spots


This tool is used to calibrate dead spots for spinning laser scanners. If a laser scanner is mounted, sometimes not the whole field of view can be used, because mounting of other hardware requires brackets or poles, creating regions where laser data is useless and generally short, i.e. dead spots.

This tool reads laser data from the blackboard for a given number of cycles, and thresholds it based on a given distance. It records a given number of data sets and compares the threshold to the median of each beam. Any laser beam that is shorted than the given distance is considered to be in a dead spot. After registering all short beams, adjacent beams are accumulated to dead spot regions. The configuration information is then written to the configuration of the connected Fawkes instance for later use (unless a dry run is performed). To prevent false calibration the number of expected dead spots can be supplied, to detect if there was not enough free space around the robot during calibration.



Show usage instructions.

-r host[:port]]

The host and port of the Fawkes instance to connect to.

-w sec

Wait the given time in seconds before acquiring the data. This gives some time for last preparations, like removing a cable. The maximum wait time is 60 seconds, the default wait time is 10 seconds.

-n N

The number of measurements to use to calculate the median of the laser beam distance value to compare to the threshold. The default number of measurements is 100.

-c dist

The threshold distance. Laser beams below this distance are considered dead, longer once are good. The default threshold distance is 0.9 meters.

-m margin_deg

Add an extra margin of margin_deg to each calculated dead spots, on both sides. Dead spots, that overlap after applying the margin are merged. The margin can be negative to shrink the regions. The margin is given in degrees as integer with a value range of [-359..359].


Do a dry run, i.e. do not write the calibration information to the configuration file but only print it to the console.


Write a fake laser scan to the blackboard interface "Laser720Interface::Laser Calibration", with "good" values having a distance of 1.0, and dead values a distance of 0. This allows for a quick inspection if the result matches the expectation. Stop showing the data with Ctrl-C when done.

num spots

Expect to have N dead spots. If a different number of dead spots is found abort and report an error.


fflaser_deadspots 4

Read measurements from Fawkes on localhost, calculate dead spots with the default values and expect 4 dead spots. Write the data back to the configuration when successful.

fflaser_deadspots -w 5 -n 200 -c 1.5 -m 1 -d 3

Run the calibration, based on 200 measurements and a distance threshold of 1.5 meters, after waiting 5 seconds. Add a margin of 1 degree to calculated spots, expect 3 dead spots. Do not write data to the configuration (perform a dry run).

See Also



Written by Tim Niemueller <niemueller@kbsg.rwth-aachen.de>


Documentation by Tim Niemueller <niemueller@kbsg.rwth-aachen.de>


Part of the Fawkes Robot Software Framework. Project website is at http://www.fawkesrobotics.org


01/27/2017 Fawkes 1.0.0 Fawkes Manual