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Thread: Ally -My First Hexapod Project

  1. #1
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    Lightbulb Ally -My First Hexapod Project

    Hello everyone!

    I have been a lurker on this forum for quite some time (BTW, you guys are incredible) and I have decided to track my progress on my latest project here. I had been posting in my blog, but have come to realize this area (the project shocase) is a far more appropriate place.

    I am building a pheonix/micromagic inspired hexapod that will primarily be a testbed for different computer vision and AI concepts I am working on. My goal is to make him as autonomous and aware of his environment as possible. My senior project consisted of a camera on a lynxmotion pan-tilt rig controlled by a phidget advanced servocontroller which tracked peoples faces using OpenCV. This uploaded data to a webserver about what it viewed. So my first goal with Ally is to use the core of that project as the foundation for this one. My parts list as of now:

    6 HS 225MG
    8 HS 485HB
    6 HS 645MG
    (all servo choices are subject to change without notice)
    9 Multipurpose Brackets (Servo Erector Set)
    1 "C" Bracket
    1 1.2G Wireless Surveillance Camera
    SSC-32 Servocontroller
    BlueSmirf Bluetooth Modem
    2.4 GHz Duck Antenna
    6.0 Volt 1600mA NiMH Battery
    2 9 Volt Recharge-ables
    Battery Harness
    Lots of 1/8" (3.175mm) Polycarbonate

    I have all of my parts together (finally) and have produced a shrine to robotics on my bedroom desk. Needless to say, my girlfriend will not be as thrilled as I am to have this monument to geekdom less than three feet from where we sleep

    I went through some major design changes to my chassis after someone pointed out a few flaws to my original design. So I have done a quick and dirty layout in Sketchup of the new chassis. Any comments/criticisms would be most appreciated!

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    Re: Ally -My First Hexapod Project

    So I have the chassis cut, and am working on the legs. I also have the coxa joint assemblies just about put together. Thinking about mounting the pan-tilt mechanism for the camera on the front of the chassis. However if I do that I loose the higher POV (which could be important). Mounting it on the front would give it a more organic feel, but would also shift its COG pretty drastically, and may unduly tax the front legs servos. I could just give it a pan head, which would minimize this by eliminating a servo and a bracket. I guess I have to weigh the pros/cons of each more carefully and take care not to loose my focus on why I am building this in the first place. So I have held off on cutting the mount for it until I get a little further along.

    If anyone is thinking about using polycarbonate or it's derivatives (Lexan, Plexiglass, etc.) you should check out these links below:

    http://www.modders-inc.com/modules.p...=Story2&mdid=4

    http://www.controlbooth.com/forums/s...carbonate.html

    They have some good basic information on tools and techniques, especially for finishing cut pieces and how to work through curves. Bless the case-modding community

    I'll get some pictures up soon. Wrapping up some essays for my college transfer apps (ugh) is eating up a bunch of my time.

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    Re: Ally -My First Hexapod Project

    Okay guys its been awhile since I updated here. Progress is coming along smoothly (albeit slowly) on the construction. I'm still wrapping up my college apps for transfer and it's eating a lot of my time. So I managed to "sneak" into the Marine Biology workshop here on campus and use the tools. No sneaking about it actually... I'm the programmer for the schools MATE team again this year. So instead of building the ROV, I was working on my hexapod.

    So I mounted a grinding stone on the drill press running at 2500RPM and used it to rough out the femurs. It worked surprisingly well on the poly. I didn't have any melting issues, and once I figured out the gist of it I started cruising along nicely. The nice thing about using the tinted polycarbonate is you can see right through it. I had a scale drawing I could hold the piece I was working on to and check out how I was doing.

    I'll be back in the workshop tonight and will have more pics up later.

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    Re: Ally -My First Hexapod Project

    Looking good! Thanks for the pictorial build process
    Andrew Dresner
    Principal Engineer
    Interbotix GIthub
    Interbotix Labs Google+

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    Re: Ally -My First Hexapod Project

    Thanks Tyberius! That means a lot coming from you.

    So I learned a few new things about working with polycarbonate, and I have a few more shop pictures to post. What I learned (the hard way) was that a little heat might be a good thing but too much heat is really bad when grinding it. Normally what I have been doing it grinding a section at a time, give the stone a chance to cool just a bit, and then grinding a different section. When the stone is just a bit warm it seems to grind better. However, when I was working out the curves on the body I ended up letting the stone get a bit too hot... The picture speaks for itself Luckily it was an easy fix (both the stone and the body).

    So the lesson learned:
    *When using powertools with polycarbonate, have more patience than what is normally required!

    Anyway, it turned out fine and you can see the before and after shots below. Now that I'm this far along I will try to get some pictures of the body with some of the hardware mounted in the next couple days.

    I also need to start working on converting Phidget AdvancedServoController code into something an SSC-32 can understand. Why reinvent the wheel, when I already have my pan-tilt mechanism coded to track faces with OpenCV, right? I'm hoping that won't be too much of a problem. Programming is my strongpoint. I also have a framework for the IK but I need to actually begin implementing it into code. Now that I'm this far along in the construction, I can work on it more and have some meaningful progress because I will have a platform to test it on (yay!).

    Never built a bot entirely on my own before... It has always been as part of a team, and never anything like this. You know what?

    ....This is ridiculously fun.

  6. #6

    Re: Ally -My First Hexapod Project

    Putting the grinding on a drill press is a pretty cool idea. Low-tech, but effective.

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    Re: Ally -My First Hexapod Project

    Thank you! Whatever works, right? I've been busy the past few days and I managed to find a few more interesting ways to use a drill/drillpress, as you will see.

    I also managed to cover myself in toothpaste Let me explain...

    I had all of the femurs and main chassis roughed out, and the edges were, well, rough. So I used a 60 grit sandpaper drum mounted on a handheld to clean them up. After that, a 120 grit. Now this is where the toothpaste comes in. I had read on a case-modding site that toothpaste acts as a great finisher/polisher because it contains mild abrasives. I think to myself, "Why not?" and grab a tube of Crest, a buffing head for the handheld, and go outside. Well, I was a little too liberal in applying it, and managed to cover a 4 x 4 meter area in toothpaste spray, with little 'ol me getting the worst of it. Hence, no pictures of that escapade, as I was way to sticky to touch a camera. The funny thing is that it worked beautifully! The edges are nice and smooth (smoother than when the poly came from the factory, in fact). For anyone thinking about doing this, all you need is VERY little toothpaste

    I used a drill to punch a hole in the chassis for the pan-tilt assembly, and then used sandpaper to smooth the edges. Again, it worked supprisingly well, if only a little labor-intensive. I was concerned I would crack the poly working close to the edge like that, but I have found that by taking my time and applying minor amounts of pressure that the poly seems to undergo very little stress.

    Now I have the coxa assemblies and the pan-tilt mounted. I still need to get around to making the cutaways for the tibia sections, and drilling holes in the femurs to mount them on the servos. I submit these pictures for approval. How's it looking so far, guys?

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    Re: Ally -My First Hexapod Project

    Nice work so far! You really need a jigsaw or better yet a band saw and a scroll saw. They would save you a ton of time.
    "If A is a success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut."
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    Einstein

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    Re: Ally -My First Hexapod Project

    Thank you for the compliment, and what I wouldn't have done for a jigsaw! Alas the poor college student dilemma strikes again

    It's been awhile since I updated so I shot a quick video update to share with you all. I'm on spring break, so I have a ton of time to work on this

    Enjoy!



    Look for some good build pics here soon as well
    Last edited by parallax; 03-18-2010 at 07:51 PM. Reason: I left out some information... oops!

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    Re: Ally -My First Hexapod Project

    What I just realized from posting this video on YouTube is that the word Ally (as in the singular form of Allies) is spelled the same as the name Ally (as in Ally McBeal). That was totally unintentional...Guess I just figured whether Ally is a boy or girl!

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