Wednesday, 26 September 2007

You may remember that I previously showed you my SICK PLS101-312 laser scanning range finder, that I intended to use with my 914.

I've now mounted the laser on top of the robot using a simple flat piece of HDPE to replace the top chassis plate, with holes drilled appropriately. The SICK lasers have all sorts of threaded mounting holes so this was the easy part. I've also mounted two 12V SLA batteries on there too - because the SICK lasers run from 24V:

The laser is simply connected to serial port of the mini-itx board as it has an RS232 interface. The 914 is more than capable of carrying the extra weight, but as I previously mentioned, if I had the choice I would probably have bought a smaller laser to mount under my lifting head mod.

The laser's front is angled downwards which means actually diverts the laser scan in this direction too, so even though the laser is mounted quite high, it still cuts though objects like coffee tables that are just above the downward facing IR beak sensors.

My original intention was to use the PLS with the Player/Stage and it's various out-of-the-box navigation, path planning and localization algorithms. However, I have had quite a lot of trouble getting the laser to work which appears to be down to the 'sickpls' driver for Player - basically it doesn't support all the functionality of the SICK LMS series driver which means it won't work with the Player graphical utilities.

My intention now is to attempt to write a program to interface to the PLS myself, since it's only RS232 comms it shouldn't be too hard. I will probably write some sort of simple mapping and collision avoidance program using the PLS, although it probably won't be quite as good as the Player functionality. Of course it's possible that the Player 'sickpls' driver may get merged with the 'sicklms200' driver and it will get full support at some point in the future - if anyone is an expert on writing or modifying Player divers then let me know.

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