SICK LMS-200 and reflectivity data mode.

Nov 13, 2003 2 Replies

Have you worked with a SICK rangefinder? Have you used it to get reflectivity data from its scans? If so, please read this!



My lab has a SICK LMS200-30106. The manual states in section 4.1.7 that we should be able to change the operating mode of the scanner to include reflectivity data (using the BM_TGM telegram and mode 0x2B). It also states that responses are formatted as described in 4.2.46 (MWREM_TGM telegram, code 0xF5)--in short, two bytes give the distance value for that angle and another 2 bytes give the reflectivity.



I can successfully set the SICK to return MWREM_TGM packets, but they all look something like this (Hope the formatting turns out ok):


2 80 de 2 f5 1 0 1 0 b5 0 b5 40

ad 1b 0 0 ac 1b 0 0 a9 8 0 0 a0 8 0 0 10 d2 6


...basically, the data portion of the scan gives 181 angle measurements (as I expected) where in each case the second 2 bytes of each angle measurement (the reflectivity portion) is zero. I get scans like this no matter what I do--I've put retroreflective strips, shiny metal, whatever--the reflectivity bytes are ALWAYS zero.



So am I doing something wrong? Am I mis-reading the MWREM_TGM packet format? Something else? Any help is much appreciated. Thanks,



Ed Clarkson Georgia Tech Mobile Robot Lab


Never done it the way you describe, but have managed to use 77H (LMSKFGDEF_TGM) and mode 1 or 3 to get reflector information (more or less TRUE/FALSE [REFLECTOR/NO_REFLECTOR]) together with normal range measurement. Works well with 3M Diamond Grade.

Out of interest, what are you trying to achieve?

Regards

Sjur

I've heard of this 'low-resolution' mode but have never heard details-- thanks, I'll look into that. There've been a number of groups to use the SICKs for reflector barcode readings on mobile robots, and I think that's how most of them do that. Unfortunately, I don't think that will do much good for what we'd like to do...

The simple answer is that my advisor asked me to :). More informatively--we'd like to see if we can use reflectivity information for terrain characterization (on a mobile robotics platform). Obviously, on/off isn't useful for that but a ~13,000 value gradient (as the SICK manual describes) might be. Thanks,

Ed

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