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Laser Triangulation for Navigation — Parallax Forums

Laser Triangulation for Navigation

ercoerco Posts: 20,254
edited 2014-01-12 06:34 in Robotics
I'm finally starting on this long-term project to determine robot position using an on-board scanning laser and a few fixed reflectors around the room. I'm curious if anyone else has implemented this successfully. I've done some preliminary experiments with the Hamamatsu P6986 sensor Philo used at http://www.philohome.com/sensors/lasersensor.htm Sensor works as advertised, range is ~6-7 feet even without a lens.

Naturally, the sensor is backordered at the only source, must find out if Junun will restock: http://www.junun.org/MarkIII/Info.jsp?item=79

Richard Vannoy 2001 interesting geometry document http://www.seattlerobotics.org/encoder/200109/lasernav.htm

Comments

  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-12 00:45
    Erco while I havent acually spent much time writing any code, been busy with assembly im very intrested in using lasers for object detection and navigation too. Im wondering why this senor over a wiimote cam? maybe i should look into these also? the wiicam just seemed very powerful and easy to use, heck it suposedly even works well in sunlight
  • Martin_HMartin_H Posts: 4,051
    edited 2012-11-12 05:44
    Sounds like a cool project. Keep us posted.

    I've been meaning to try a laser pointer with my TSL1401 to see if it could pick up reflectors. The line scan camera is more general sensor and picking the right threshold should allow it to differentiate between ambient and laser light. It has the advantage of excellent tech support in this forum as well.
  • lardomlardom Posts: 1,659
    edited 2012-11-12 06:19
    I'd like to follow your progress. I bookmarked a video where warehouse robots read scanbars on the floor to determine location.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-12 07:11
    martim, ive been looing for a suitable camera to connect to a prop so i can send images to the pc for robo realm to scan. do you know approxamitely how many images per second the tsl1401 can take? also what is meant by 128 pixel line scan does this thing take a full picture?
  • Martin_HMartin_H Posts: 4,051
    edited 2012-11-12 08:02
    rwgast_logicdesign wrote: »
    martim, ive been looing for a suitable camera to connect to a prop so i can send images to the pc for robo realm to scan. do you know approxamitely how many images per second the tsl1401 can take? also what is meant by 128 pixel line scan does this thing take a full picture?

    The TSL1401 doesn't take a complete image. It scans a single line of 128 pixels gray scale pixels. At first glance that doesn't sound that useful, but it's more useful than you would think as Robots mostly live in a 2D world. So you can tell relative brightness across the field of view and locate a bright light like a beacon or a candle flame. Phil Pi is the designer and has said that if you replace the lens with a vertical slit it becomes even more useful for this sort of thing.

    Because it is a single black and white scan line the frame rate is good because you're not moving that much data around. Image processing of a single scan line is much easier to do as well.
  • rjo__rjo__ Posts: 2,114
    edited 2012-11-16 12:26
    I concur with the TSL1401, I have tested it for laser triangulation using a laser from a $29 hardware store laser-line thingy. I actually used 2 TSL1401's so that I could move the laser line and not have to worry about exactly where it was moving. I could see targets up to 20ft by stobing the laser on and off and then subtracting the off data from the on data. Laser line generators are perfect because you don't have to have the laser and the tsl lined up with absolute precision.

    I have also generated full color images by using colored LED's and stepper motors to move the target. The only thing I don't like about the TSL is the connectors... either a male plug should be provided or a reference to the cable. At the time I couldn't find one and ended up hand soldering my connections in a really tiny space:)
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-16 12:46
    Wow so if I set up a tsl your telling me I could accuretly get 20ft readings, could this be extended? I already have a few lasers and wii cams but they could be useful for other things while I used the tsl14 for object detection, especially since it has a much farther range. One thing I dont understand is if its in black and white how can you tell the difference in light wavelengths, or do you just detect your lasers/leds by using the tsl to count pulse patterns emitted from them?
  • rjo__rjo__ Posts: 2,114
    edited 2012-11-16 21:47
    yup!!!!!!!!!!!!

    (sorry for the extra !!!'s but there is a 10 character minimum).

    I looked for a maximum in the difference data between on and off laser states... I didn't have any intelligence in my set up. To be fully functional, you would have to do some data analysis to see if the surround is compatible with your expectations;.

    Rich
  • ercoerco Posts: 20,254
    edited 2012-11-17 14:33
    Once again, Tim at Junun gave a way the farm (to me). I inquired about whether the Hamamatsu S6986 sensor was available, and he sent me his last two for free. I'll insist on paying him. It's nice that he offered them for free, but it's bad that he doesn't plan to restock them. They are simple to use and work very well.

    http://www.junun.org/MarkIII/Info.jsp?item=79
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-17 16:17
    :/ im not seeing anywhere to buy these either except http://www.active-robots.com/shop-by-brand/hamamatsu which is in the uk and some guy on al baba or whatever which idk how to buy from i think its got to be huge quantity, I just pulled two wii remote cams yesterday id make you a good trade on one just so I can see what you come up with :)
  • ercoerco Posts: 20,254
    edited 2013-01-17 15:20
    Just found & bookmarked this 12-year-old page with lots of useful math & trig for laser navigation: http://www.seattlerobotics.org/encoder/200109/lasernav.htm

    If you like PhiPi's paper on BoeBot encoders and navigation, you'll love this! http://www.parallax.com/Portals/0/Downloads/docs/prod/datast/ApplyEncoder.pdf
  • PublisonPublison Posts: 12,366
    edited 2014-01-12 06:34
    erco wrote: »
    Just found & bookmarked this 12-year-old page with lots of useful math & trig for laser navigation: http://www.seattlerobotics.org/encoder/200109/lasernav.htm

    If you like PhiPi's paper on BoeBot encoders and navigation, you'll love this! http://www.parallax.com/Portals/0/Downloads/docs/prod/datast/ApplyEncoder.pdf

    If you are looking for Phil's paper on the BoeBot encoders, it's now located at:

    http://www.parallax.com/downloads/applying-boe-bot-digital-encoder-kit
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