Shop OBEX P1 Docs P2 Docs Learn Events
Robo to robo location detection help — Parallax Forums

Robo to robo location detection help

alphanerd132alphanerd132 Posts: 9
in Robotics
I have 2 BOE bots and I need both of them to know where the other is. I want to have a little bot run around and pick up small items and put them in the back of a truck and then from there the truck will deposit the items and come back for the little bot and pick it up. Then go back go the dock. Right now I am using IR for wall and object detection but I can use sonar and RF.

Comments

  • kwinnkwinn Posts: 8,697
    An IR or sonar beacon and scanner on each robot should work. IR would probably be easier. Each beacon rotates through 360 degrees and sends out a unique frequency or code multiple times per revolution. Each receiver detects detects the frequency or code sent by the other robot and saves the direction the beacon was pointing in. Use a remote control IR receiver module and appropriate IR led.
  • alphanerd132alphanerd132 Posts: 9
    kwinn wrote: »
    An IR or sonar beacon and scanner on each robot should work. IR would probably be easier. Each beacon rotates through 360 degrees and sends out a unique frequency or code multiple times per revolution. Each receiver detects detects the frequency or code sent by the other robot and saves the direction the beacon was pointing in. Use a remote control IR receiver module and appropriate IR led.

    I was planning on just having a system of a ring of IRs and then haveing a total of 12 IR transistors so that it can detect at all times. My next question is how does sonar systems work and do you know a good place to get cheap ones? I found them for $8 on amazon and i think that is what i will go with
  • kwinnkwinn Posts: 8,697
    alphanerd132 wrote: »
    kwinn wrote: »
    An IR or sonar beacon and scanner on each robot should work. IR would probably be easier. Each beacon rotates through 360 degrees and sends out a unique frequency or code multiple times per revolution. Each receiver detects detects the frequency or code sent by the other robot and saves the direction the beacon was pointing in. Use a remote control IR receiver module and appropriate IR led.

    I was planning on just having a system of a ring of IRs and then haveing a total of 12 IR transistors so that it can detect at all times. My next question is how does sonar systems work and do you know a good place to get cheap ones? I found them for $8 on amazon and i think that is what i will go with

    The ring of IR receivers is a great idea. Provides a rough location that can be narrowed down by having the robot turn. No extra motors or mechanical system required. Not sure how well the sonar would work. Seems to me the range is a bit on the short side for this.
  • xanaduxanadu Posts: 3,347
    For $60 you could get a pair of these https://www.pololu.com/product/701 or just use the article as a DIY guideline.
  • alphanerd132alphanerd132 Posts: 9
    kwinn wrote: »
    alphanerd132 wrote: »
    kwinn wrote: »
    An IR or sonar beacon and scanner on each robot should work. IR would probably be easier. Each beacon rotates through 360 degrees and sends out a unique frequency or code multiple times per revolution. Each receiver detects detects the frequency or code sent by the other robot and saves the direction the beacon was pointing in. Use a remote control IR receiver module and appropriate IR led.

    I was planning on just having a system of a ring of IRs and then haveing a total of 12 IR transistors so that it can detect at all times. My next question is how does sonar systems work and do you know a good place to get cheap ones? I found them for $8 on amazon and i think that is what i will go with

    The ring of IR receivers is a great idea. Provides a rough location that can be narrowed down by having the robot turn. No extra motors or mechanical system required. Not sure how well the sonar would work. Seems to me the range is a bit on the short side for this.

    My issue is that i can not then have wall detection

  • Martin_HMartin_H Posts: 4,051
    edited 2016-01-14 00:52
    I have a pair of the Pololu beacons and have used them in a couple of projects. I'd recommend them for what you want to do. Here's one where my Boe-bot uses a laser sensor to find a target and bring it to the beacon:

  • xanaduxanadu Posts: 3,347
    edited 2016-01-14 01:36
    I missed the part about not wanting to use IR, I think you can. You could poll the sensors individually instead of all at once. Shut down the obstacle IR while the locator IR is active. If you bounce fast enough between them you probably wouldn't notice a difference.

    Edit: Then again maybe not, because both IR locators would need to be on at the same time... That would take some experimentation.

    eBay is a good place to get cheap ultrasonic, just be careful some are 4 wire and require much different setup than the 3 pin Parallax sells.
  • kwinnkwinn Posts: 8,697
    alphanerd132 wrote: »
    kwinn wrote: »
    alphanerd132 wrote: »
    kwinn wrote: »
    An IR or sonar beacon and scanner on each robot should work. IR would probably be easier. Each beacon rotates through 360 degrees and sends out a unique frequency or code multiple times per revolution. Each receiver detects detects the frequency or code sent by the other robot and saves the direction the beacon was pointing in. Use a remote control IR receiver module and appropriate IR led.

    I was planning on just having a system of a ring of IRs and then haveing a total of 12 IR transistors so that it can detect at all times. My next question is how does sonar systems work and do you know a good place to get cheap ones? I found them for $8 on amazon and i think that is what i will go with

    The ring of IR receivers is a great idea. Provides a rough location that can be narrowed down by having the robot turn. No extra motors or mechanical system required. Not sure how well the sonar would work. Seems to me the range is a bit on the short side for this.

    My issue is that i can not then have wall detection

    I didn't realize these were for wall detection. Still, no reason you couldn't add an IR receiver to detect the beacon signal. Might even add a transmitter and use a retroreflector instead of a beacon.
  • alphanerd132alphanerd132 Posts: 9
    xanadu wrote: »
    I missed the part about not wanting to use IR, I think you can. You could poll the sensors individually instead of all at once. Shut down the obstacle IR while the locator IR is active. If you bounce fast enough between them you probably wouldn't notice a difference.

    Edit: Then again maybe not, because both IR locators would need to be on at the same time... That would take some experimentation.

    eBay is a good place to get cheap ultrasonic, just be careful some are 4 wire and require much different setup than the 3 pin Parallax sells.

    I think i will try your method even tho the boe borde has a slow clock speed. And i am already having the borde in a old RC humve body and such. I can work with it if it turns out being a 4 pin. And I am using this for a high school compatition and funding it my self. So i need to stay on the cheap side and learn how to use what i have to work with
  • MikeDYurMikeDYur Posts: 2,176
    Martin_H wrote: »
    I have a pair of the Pololu beacons and have used them in a couple of projects. I'd recommend them for what you want to do. Here's one where my Boe-bot uses a laser sensor to find a target and bring it to the beacon:





    Martin, this looks like the best way to have a robot find it's charging station, I would like to have the robot make it's own call, through ADC to head for recharge, that willl have to be a variable, and depend on distance it will have to travel. So as not to run out of gas getting there.

    _mike
  • xanaduxanadu Posts: 3,347
    Are "whiskers" off the table? They're not bad, sometimes better than a single sensor mounted out front. Cheap, and frees up your IR range for the tracking.

  • ercoerco Posts: 20,256
    edited 2016-01-14 20:27
    Seems to me that IR or laser are your only realistic options for reliable localization. Line of sight is pretty easy to verify, and you can view the IR energy using a camera. Ultrasonic can reflect and dissipate in unanticipated ways and it's hard to aim and control, much less view. Martin's laser demo was pretty darn cool, where he stops periodically to rescan for the reflective target. Here's another method shown below: I drive forward constantly, steering slightly left when the laser loses the target or slightly right when the laser sees the target. I still have a few of those Hamamatsu laser sensors if you want to experiment. These last few are going for $8 now, almost gone. Won't last! :)



  • Martin_HMartin_H Posts: 4,051
    @_mike, as erco mentioned, the Hamamatsu laser sensors coupled with the good retro-reflector tape are excellent for pinpoint object location from across the room. As I said in the video, when you couple it with a Ping))) you can really zero in on something.

    But the Pololu IR beacons are pretty sweet too, they allow a robot to turn off and on the IR emission versus detection function. If you have another channel of communication between a pair of robot (e.g. Bluetooth, XBees, or Wixels) you can coordinate their IR usage to avoid collision and let both bots use IR for more than just beacons.
  • ercoerco Posts: 20,256
    edited 2016-01-15 20:49
    These $1.65 four-pin IR modules emit a 38 khz IR signal to look for a reflection as obstacle sensors. There is an ENable pin which can turn off the IR signal, then the unfettered 38 khz receiver module can detect signals from IR beacons or remote controls. Uses a rare low-gain continuous signal compatible IR receiver. Double duty, slick and cheap. BUT, quality varies wildly. Order twice as many as you need, some will be better than others, you need to test, adjust, and sort into matching groups. Quality-wise, I see modules with wildly different (and often transposed) pot number values. Note the difference between the Ebay link unit and the image in my Youtube still (also lifted from Ebay). Probably misassembled, the values rarely match the numbers screened on the PCB.

    Edit: I used and wrote about this sensor at http://servo.texterity.com/servo/201512/?folio=44&pg=44#pg44

    Do not bother with 3-pin modules, which only use DC IR light levels.

    http://www.ebay.com/itm/311523477616

    Extended range when a big Scotchlite reflector is used. Coupled with an ultrasonic sensor to verify range, you could so some impressive feats .


  • MikeDYurMikeDYur Posts: 2,176
    @Martin
    @erco

    That setup looks great for indoor use, and will be the path I take for my Activity Bot, you guys are having a lot of fun with the BoeBot types, I have the gripper on mine and need to start working with it, I am missing out.


    Interested in my options for outdoor use,
    I followed cmdr erco's recommendations,
    and have recently finished the code for the Gimbal Joystick remote control, I now have proportional steering and throttle, also will be employing the Ackermann steering geometry,
    it should be achived fairly easy on my robot, shortening the tie rod and some re-adjustment plus coding changes, I should have done the latter first, but I have had limited mobility for over week. Will be incorporating long range radios for control, and long range video/audio.

    As Martin mentioned to me, GPS will keep me in the ballpark of where and where not to go, ping sensors work outside maybe not as good as indoors, but if I lost video, control or just need a re-charge, I want it to head back home on it's own, must keep it out of the road.
Sign In or Register to comment.