Shop OBEX P1 Docs P2 Docs Learn Events
invisible (or hardly) tracking marker for a robot — Parallax Forums

invisible (or hardly) tracking marker for a robot

GeorgeCollinsGeorgeCollins Posts: 132
edited 2011-07-01 09:51 in Robotics
I was trying to think of something I could use to have my robot track a path, like a line following robot, where the line on the ground would not be easy to see with the human eye. The ideal thing would be a transparent piece of tape that an IR or color sensor picks up the way IR sensors can detect a white line on a black background. Other more exotic alternatives could be very small RFID stickers, or some kind or marker that is really small or hidden from view.

The idea is to be able to have my robot follow a path on a hardwood floor without having to paint a big white line on the floor.

This seems like a problem that others have probably thought about, but I didn't get any good hits from Google. Does anyone here have suggestions? Ideas? Something they saw someone else try?

Thank you for your help.

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-06-23 10:54
    You could also use IR beacons. There's been some discussion here about these.

    I think the jest of it is each beacon would flash its IRED at different frequencies. The robot would know ahead of time were each beacon is located. The robot could then triangulate its own position base on the angle to each beacon.

    Duane
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-06-23 10:56
    You could try something that fluoresces under UV and use a UV LED to illuminate it. If it fluoresces monochromatically, a same-color filter in front of the sensor would increase reliability.

    I just use black masking tape on my kitchen floor and leave it there, even though it comes up easily. But, hey, I'm single and can get by with stuff like that! :)

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-06-23 10:57
    I know there is IR reflective paint. People use the paint on their license plates to block the automatic cameras from photographing their plates.

    I'm pretty sure the paint is transparent to visible light. I doubt you want to paint your hardwood floors with it.

    Duane
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-06-23 11:22
    Duane Degn wrote: »
    I know there is IR reflective paint. People use the paint on their license plates to block the automatic cameras from photographing their plates.

    So they think! Anyone who's gotten a ticket from one of these (not me, but my son) knows they're color cameras. No amount of IR blocking paint is going to keep you from getting a ticket. Those products are a sham, at least for any red light camera made in the last decade.

    I second Phil's suggestion of an "invisible ink" which will fluoresce under a UV LED. The only trick is to get the fluorescence into the green/yellow region where you have a better chance of detecting it using an ordinary photo detector. A CdS cell works well here, but is slower-acting than a phototransistor. So-called blue enhanced photo detectors tend to be fairly expensive. (Parallax has one, though, if you go this direction.) You can also try a phototransistor in a CLEAR casing. Don't get the kind with the built-in IR filtration.

    -- Gordon
  • GeorgeCollinsGeorgeCollins Posts: 132
    edited 2011-06-23 11:43
    A beacon is an interesting idea because you could probably mount it on the wall so it is hard to see at eye level but easy to detect by a sensor low to the ground. UV ink could also do it-- now I have two things to Google. I may have more questions later but let me gather some information on these ideas first.

    Thank you everyone for your good suggestions!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-06-23 11:57
    I think I have one of these. I haven't tried it out myself yet.

    I've found glow-in-the-dark stuff fluoresces very nicely with a violet laser. Some glow-in-the-dark paint can be nearly invisible in daylight.

    @Gordon, I thought they use IR photography to cut through the glare of the windshield? Those type of things are much too high tech for my neck of the woods.

    P.S. I grew up in Pacific Beach, San Diego. What the heck I'm I doing in Idaho?!
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-06-23 13:34
    Duane Degn wrote: »
    @Gordon, I thought they use IR photography to cut through the glare of the windshield? Those type of things are much too high tech for my neck of the woods.

    It's the opposite. IR increases light glare. UV filtration + polarization reduces glare. And that's exactly what any modern red light camera does.

    The typical setup may include an IR camera in case the photoflash doesn't trigger, but most now include a VERY high resolution color camera capable of maintaining resolution even at 50X or 100X zoom, plus a color video camera.

    (IR plus photoflash is a mess; the photoflash is used for the color image which has IR filtration, just like our eyes see it. They use both to circumvent exactly this sort of thing -- and likely send an additional violation if they see any attempt to block the license plate!)
    P.S. I grew up in Pacific Beach, San Diego. What the heck I'm I doing in Idaho?!
    A few months back I met a woman at a craft show at the Del Mar Fairgrounds that was headed to Coeur d'Alene. Greener pastures, I guess. Personally I'd have a hard time living outside Southern California.

    -- Gordon
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2011-06-23 15:30
    Most standard conformal coatings fluoresce under UV light. At work, we use a black ring light to inspect the conformal coating coverage. I etched some holes half way through a piece of acrylic, filled some with conformal coat and some with a clear CA glue to create a "coded stick" that can only be seen with a UV light. Drawing out a lot of lines would cost a bit much though....
  • LaserLinesLaserLines Posts: 14
    edited 2011-06-30 15:37
    GordonMcComb wrote: »
    It's the opposite. IR increases light glare. UV filtration + polarization reduces glare. And that's exactly what any modern red light camera does.
    otoflash doesn't trigger, but most now include a VERY high resolution color camera capable of maintaining resolution even at 50X or 100X zoom, plus a color video camera.
    -- Gordon

    This reminds me of an Idea I had a while back, one I'll never build and test.

    Put an LCD screen over the plate with a activated bar wide enough to black out a couple of the numbers. Then scan the bar across the plate fast enough that a human can't see the bar. It would look like a slightly tinted plate, but otherwise normal. A camera with it's shutter fast enough to capture a moving car, would see some of the plate numbers blocked out.

    When I thought of this I didn't know video cameras were involved. At lease a human would have to watch the video and figure it out from several frames, A computer couldn't just send you an automated ticket.

    I was planning it as a political statement, but the installation of cameras in my community was killed by others quicker and louder than I.
  • ercoerco Posts: 20,256
    edited 2011-06-30 16:29
    A dozen years ago at work, we had a fairly advanced mail-delivery robot (nicknamed Mailvin) that would follow an "invisible" IR line painted on the carpet through the building, making regularly scheduled stops. Once a week, the carpet cleaners would come through at night. It was a hoot watching them avoid scrubbing the lines. They would crawl around on hands & knees first with a UV light, marking the line with strips of paper, and they would shampoo around the strips of paper. Then once every few months, a crew would come around to repaint the line. To prevent people from stepping on their freshly-painted lines, they they would also leave a trail of paper signs reading, "No Step, Wet Invisible Line Drying".

    That's so pre-Y2K. It always seemed to take more effort to maintain the lines than the robot ever saved.
  • mindrobotsmindrobots Posts: 6,506
    edited 2011-06-30 16:53
    Time for robots to have pheromones. Spray a scent line where you want the robot to go - let it sniff out its route. A servo actuated spray canister and your robot can leave its own trail for a return journey.

    @erco, I'm impressed that your company was shampooing carpets once a week 12 years ago. I think my company might have shampooed the carpets 12 years ago - cost cutting and all. :smile:
  • Mike GMike G Posts: 2,702
    edited 2011-06-30 19:30
    What about painting the white lines on clear plastic sheets the kind used in overhead projectors. Then you could lay out the all kinds of patterns on the floor and just pick em' up when you're done.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-06-30 20:06
    Mike,

    'Interesting idea! Bright yellow polypropylene rope or sash cord might also work.

    -Phil
  • HumanoidoHumanoido Posts: 5,770
    edited 2011-07-01 08:54
    Magnetic tape or small very flat magnets could line the center inside lines of no shag carpet, perhaps sewn into the fabric. The robot just follows along using a Hall Effect sensor. If the carpet gets dirty, just vacuum it. I did some experiments with magnets and a Hall Effect sensor from Parallax, with a Penguin walking robot.
  • graffixgraffix Posts: 389
    edited 2011-07-01 09:13
    I was considering using this portable black light(two AA batteries) mounted and shrouded in front of a QTI line follower with invisible painted lines on the floor.They have paintable and aerosol paint here with all the colors.I was hopeing the blacklight wouldnt wash out the IR light.The idea was to mount the parts on a walker (for elderly people) for my gramma (who is blind) to navigate my house with Haptic (vibration) feed back to tell her right or left depending on where she wanted to go.

    all just a thought with little resourcing

    http://www.clearneon.com/cart.php?m=product_detail&p=25
    http://www.clearneon.com/cart.php?m=product_list&c=2
    http://www.clearneon.com/cart.php?m=product_list&c=3
  • HumanoidoHumanoido Posts: 5,770
    edited 2011-07-01 09:51
    A long wire can also embed inside a carpet and emit RF. A robot signal strength receiver sensor could track it.
Sign In or Register to comment.