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Erco's Figure Eight Challenge — Parallax Forums

Erco's Figure Eight Challenge

Martin_HMartin_H Posts: 4,051
edited 2015-06-21 19:52 in Robotics
In another thread Erco issue the challenge that he would produce a robot with a single encoder that would beat a differential drive robot running a figure eight course. I foolishly accepted this challenge as I have a proof of concept robot I've been working on. But that isn't progressing quite as well as I would like, so in the mean time I figured I'll post my baseline attempt. This is CBA using its wheel encoders to run a figure eight course. I'm using the encoders as wheel speed sensors, so I arc by turning one wheel twice as fast, then even, then opposite wheel twice as fast, then even.

[video=youtube_share;BqrGA3aUha0]

I imagine an S2 could beat the wheels off my CBA because its encoders are much more accurate. But someone who owns one will need to do that.
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Comments

  • ercoerco Posts: 20,257
    edited 2012-02-21 19:56
    Nice job, Pal! I forgot about this one, the last challenge I recall issuing was about a square pattern. 10 feet on a side, 4x 90 degree turns. Remind this old dog what the particulars of the figure 8 course were. Any size?
  • Martin_HMartin_H Posts: 4,051
    edited 2012-02-22 03:58
    Me and my big mouth, it was the 4H robot thread:

    http://forums.parallax.com/showthread.php?137079-Low-cost-build-it-yourself-robot-for-4-H&p=1075195#post1075195

    The size of the figure eight wasn't specified, but you were planning a BS1 with a tricycle drive.

    My problem with the ten foot square challenge is that I don't have a ten foot area to run around in!
  • ercoerco Posts: 20,257
    edited 2012-02-22 08:16
    OK, now I remember that challenge for the simple trike drive. Gotcha. I'll sneak that in between catapult upgrades. I got more forum traction on that project!
    Martin_H wrote: »
    My problem with the ten foot square challenge is that I don't have a ten foot area to run around in!

    Yep, I had to move my living room furniture around to clear enough room to compete in a contest for ROBOT magazine:

    http://www.youtube.com/watch?v=ImriJO7DNac
  • ercoerco Posts: 20,257
    edited 2012-02-25 12:13
    My bot is in progress, Martin_H, thanks for the kick in the pants. Due to my typical overpromising and time constraints, I'm combining all my simple challenges into one ultra-simple slam-built BS1 tricycle bot: figure 8, 10' square, and 4H pitch. One servo, one drive motor, and the crudest encoder imaginable! Hope to have some video by Sunday night.
  • ercoerco Posts: 20,257
    edited 2012-02-28 19:19
    I'm sick with a cold and way behind schedule. But here's a first look at what my simple tricycle robot with a (WOW!) 4 PPR wheel encoder can do. I haven't tuned the mechanicals yet, but already I'm getting nearly 90-degree turns. The figure 8 will come later, I just had to get something on the board to keep up with Martin_H!

    and there's a look at the underside at


    and here:
    IMGP7652.jpg
    1024 x 768 - 54K
  • Martin_HMartin_H Posts: 4,051
    edited 2012-02-29 06:02
    Looking good! I could see that being used for line following as well. It wouldn't be as good for maze solving because turning completely around will be tricky.

    BTW Your insistence that the BS1 still has some life in it made me rethink my view that the BS2 is obsolete. True the BS2 doesn't have interrupts like the Arduino or concurrent processing like the Propeller, but for straight forward linear tasks it's more than adequate. Math is really its only major weak spot because the comparison operators don't understand two's compliment.
  • TtailspinTtailspin Posts: 1,326
    edited 2012-02-29 08:39
    Thats cool erco,
    It almost looks like you could use 1 PPR if the robot was dedicated to just do squares and triangles..


    -Tommy
  • ercoerco Posts: 20,257
    edited 2012-02-29 10:13
    Thanks guys. Don't forget that the steering is servo controlled. Here I only show 2 positions (straight and tight right turn), but I can steer anywhere in between and carve a perfect arc. The limiter is that I can only stop accurately in distance intervals (arc segments) of about an inch. A figure 8 made from 2 perfect circles is next. To do a perfect circle at stop at exactly 360 degrees will require the right combination of turn radius and distance.
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-02-29 11:14
    Sweet erco! I mean, "Sweet!, erco".

    Your prolific creativeness makes me jealous. It's like you get to play with toys, all day, everyday.
    -Matt
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-02-29 11:37
    With Erco, he goes to work when he comes home, with all those "honey do" jobs around the house.

    Then again he has to brave the 405 (I'm guessing, anyway). I wouldn't wish that on anyone, even if he does still use a BS1! :lol:

    -- Gordon
  • ercoerco Posts: 20,257
    edited 2012-02-29 16:51
    It's a dirty job, but... :)

    Gordon: I'm optionally on the 405 for ~3 miles, but that's the least of my worries. What are we gonna do about $4.50 gas?
  • ercoerco Posts: 20,257
    edited 2012-02-29 22:35
    This figure 8 was easy! Pretty dang accurate, too. Not bad for a quickie robot which doesn't even have reverse or speed control!
  • Tony B.Tony B. Posts: 356
    edited 2012-03-01 05:41
    Great Job! Very smooth and efficient. The clicking of the clock in the background adds a bit of suspense :) Edit: I was just watching the video again and realized that is the reed switch making the noise. Still cool!

    Tony
  • idbruceidbruce Posts: 6,197
    edited 2012-03-01 06:02
    Alright Martin_H and erco

    I think you guys are having just a bit too much fun.

    I have not really spent any time just having fun with microcontrollers, but I like a challenge and this figure eight challenge seems interesting. Are there any rules that apply to hardware?

    Bruce
  • Martin_HMartin_H Posts: 4,051
    edited 2012-03-01 07:05
    Nice Job Erco, and I wish I thought of using plates to mark the course. You win as your got closer to your origin than I did while using fewer parts than I did.

    Bruce, give it a try. This is a free form challenge and the only rule we have is that you make a figure eight. Erco was limited to a BS1 with a single sensor, but others are not.
  • photomankcphotomankc Posts: 943
    edited 2012-03-01 07:11
    Very nice. I'm working on programming arcs now for my stepper diff drive. I can tell right now that servo steering would make that much easier to do although having at least some ability to just know how far I have turned the wheel without encoders is helpful but obviously not fool-proof. Might give this a go when I have the full deck finished up.
  • Martin_HMartin_H Posts: 4,051
    edited 2012-03-01 07:45
    photomankc wrote: »
    Very nice. I'm working on programming arcs now for my stepper diff drive. I can tell right now that servo steering would make that much easier to do although having at least some ability to just know how far I have turned the wheel without encoders is helpful but obviously not fool-proof. Might give this a go when I have the full deck finished up.

    A stepper powered robot means no encoders. You could beat Erco with a robot like that!
  • ercoerco Posts: 20,257
    edited 2012-03-01 08:40
    idbruce wrote: »
    Are there any rules that apply to hardware?

    Bruce: Glad to hear you're interested! No hardware restrictions at all. As you know, I'm a minimalist who enjoys getting the most from the least. No one in their right mind would use a mechanical switch as an encoder! When I issued the challenge, I purposely limited myself to a BS1 and one encoder to draw other people in. Most anyone could program an S2 do this "two circle" figure 8 in a minute or two. But homebuilt bots are way more fun, and that's how you learn things, by scratch-building. Hope you and others decide to jump in.

    Even the definition of "figure 8" is loosey-goosey. Most anything 8-ish is valid, the primary goal is to end up right where you started.
  • ercoerco Posts: 20,257
    edited 2012-03-01 08:41
    Martin_H wrote: »
    You could beat Erco with a robot like that!

    Hey Pal, whose side are you on? :)
  • PublisonPublison Posts: 12,366
    edited 2012-03-01 08:46
    What we don't see are the PINGs underneath the bot following the outer surface of the plates. :)

    Jim

    PS: Nice job BTW
  • idbruceidbruce Posts: 6,197
    edited 2012-03-01 08:56
    Yea, I was thinking stepper motors also.
  • TtailspinTtailspin Posts: 1,326
    edited 2012-03-01 09:04
    Your estimate of "a minute or two" is a little tight, I would estimate at least 3 to 4 minutes to program the S2.
    as one will have to decide on what sound effects to play thru the speaker, and in what order to flash the LED's...
    oh yes, there is the decision of which program to use, either spin, or the more graphical S2 software.
    and of course the trivial amount of time to actually "write" the code for a figure 8...

    I will try to post tonight, and let you know the exact time it takes me...


    -Tommy
  • ercoerco Posts: 20,257
    edited 2012-03-01 09:16
    Where's Microcontrolled? He was chomping at the bit a challenge or two ago...
  • ercoerco Posts: 20,257
    edited 2012-03-01 09:23
    And where's Whit, Scribblerkart & the Gatorbots? They should be able to get an old blue Scribbler around a figure 8 in 10 minutes or less.
  • ercoerco Posts: 20,257
    edited 2012-03-01 11:18
    Howzabout PhiPi? He invented the BoeBot encoders, I'm sure this is a trivial pursuit for him.

    Or howzabout Matt_G? Perhaps he dismissed the figure 8 as a young man's game...?
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-03-01 12:32
    Or howzabout Matt_G? Perhaps he dismissed the figure 8 as a young man's game...?
    Sorry, count me out erco :-(
    The ankle shackles keep me pretty much bound to the workbench here.
    On those few occasions that I break free, Ken makes sure that the laser at my rooms' exit is fully charged.

    And with our ROBOTICS EXPO coming up, (preparations are fully underway!), there's no time - this is not a bad thing though, because we're expecting BOATLOADS of visitors (and lots of kids!) in about 5.5 weeks - It's gonna be a real treat.:thumb:

    -Matt

    ps. I'm ignoring the "young man's game" comment for now...however, watch yer back!
  • TtailspinTtailspin Posts: 1,326
    edited 2012-03-01 20:18
    I wouldn't sweat it Matt, we all understand, a guy can lose a step as he moves on in years,
    Go ahead and sit this one out, try out that new rocking chair, maybe take a nap, We'll try not to make to much noise...:)

    Here is my Scribbler 2 in action, 53 seconds of pure figure 8 fury...
    [video=youtube_share;jUukaoUDrqY]

    -Tommy
  • ercoerco Posts: 20,257
    edited 2012-03-02 00:09
    Beautiful, Tommy! Now while you're hot, send Caster's End out for a lap around those dinner plates. Come on, you can do it!

    Everybody get into the act! Your homebuilt robot, 2 plates, and a few minutes of quality coding time on YouTube. What's not to like?
  • Martin_HMartin_H Posts: 4,051
    edited 2012-03-02 06:01
    Nice job Tommy!
  • TtailspinTtailspin Posts: 1,326
    edited 2012-03-03 19:49
    The S2 encoders are a benchmark of robot accuracy to strive for, that is for sure..:thumb:

    But I like to roll my own as it were, So...
    Switch_Magnetic_Reed.jpg

    yah, thats right,.. I'm goin there..


    -Tommy
    Switch_Magnetic_Reed.jpg
    800 x 395 - 205K
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