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Thread: Woodstock - Mech Warfare entry

  1. #1
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    Woodstock - Mech Warfare entry

    Introducing Woodstock, my Mechwarfare 2011 project.

    This is a rather ambitious project for me given my lack of robotics experience and the time frame I have to complete it, but the challenge/reward is just too awesome to pass up. I've been loosely following Mech Warfare since I first discovered it back in 2008 as the first event was being planned. I couldn't help but be drawn into it, as it's easily the coolest robotics event (at least in my opinion) since the humanoid "kung-fu" events started popping up.



    Woodstock is ready from a hardware usability perspective, but I do need to add the hopper(s), some cosmetic niceties and the scoring system, which I'll do when I have the scoring system.

    I have more pictures of Woodstock in one of my profile albums http://forums.trossenrobotics.com/album.php?albumid=86

    Currently Woodstock's major parts consists of

    • 14 AX-12 servos (technically 13 AX-12 and 1 AX-12+ servos)
    • a BeagleBoard (rev C3) for onboard processing and providing me a comfy environment to play in.
    • goodies by HUV Robotics : Bioloid bus board, I/O Board, 6 axis IMU and Foot Pressure Sensors
    • a Stunt Studios semi-auto airsoft pistol
    • USB Webcam & Wifi

    As you can see from the picture I have 6DOF legs and a pan & tilt turret. I'm a bit worried that the tilt servo won't be able to cope with the load, over the course of a match, once I add all the targeting half plates on it. It's a little front heavy already, but hopefully I can balance it out. If not, I might have to drop the tilt servo and make use of the hip servos.

    I've opted to make use of a Bioloid I/O board to trigger the RCE200X switch for firing the gun. I had originally planned to use the BeagleBoard expansion header for this, but it's just so much easier to keep everything interfaced off the Bioloid bus.

    I'm currently running Ubuntu 10.10 (ARM) on the BeagleBoard and making use of gstreamer for network video streaming from the USB webcam. It works great and makes for a smaller overall package (size & weight?) than an arbotix combined an IP camera from what I've seen. The USB wifi dongle I'm using (with the case removed) is only slightly larger than a ZIG100 board and has an external antenna that you can sort of see sticking up off the top of Woodstock's head in the picture above. Mostly, I prefer the comfort of running Linux, it means there is one less thing I need to learn/worry about to make my robot work.

    I have code for interfacing with all of the goodies on my bioloid bus and specific to controlling the turret via a PS3 controller. I still need to finish making all the needed changes to get this working across the network, but as soon as I do I'll post video of that.

    The big ticket item left to do is make this thing walk. I feel that it's very doable based on the balance experiments I've done with this leg configuration so far. Specifically, balancing on one leg with no power on (or even connected). I am aiming to use Inverse Kinematics to generate a variable gaits and have been further fueled in this ideal by seeing Zenta's awesome work with Archer. Not that I think I'm anywhere near Zenta's mad skill level, it's just awesome and inspiring to see that caliber of work. I started on the math for this a while ago and I think I'm close to having something usable for it.

    I scored myself the seasoned Mech Warfare veteran Gdubb2 as partner in the 2vs2 competition, so failure is not an option. Go Team Maggot!

    Cheers!


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    Re: Woodstock - Mech Warfare entry

    Wait a minute?!! He let a biped on his team?!!! Nice work with that Beagle Board, Btw.

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    Re: Woodstock - Mech Warfare entry

    Nice bot! I like that you are using the Beagleboard and that you are streaming a usb cam rather than having to rely on a wifi ip camera. I've experimented with streaming a usb cam, and the picture quality was great, but the camera (logitech I believe) didn't like jitter. Any sudden movement would cause the picture to blur, so I put this element of my project on the backburner.

    What brand of camera are you using, and have you seen any issues like the one I described?
    Always outnumbered, never outgunned. Axiom Robotics

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    Re: Woodstock - Mech Warfare entry

    Thanks mannyr7 & master_of_robots

    The BeagleBoard has been pretty fun overall.

    I'm using the cheapest "no name" UVC camera I could find, it was less than $10 and I got 3 of them. I went cheap on the camera because I was just experimenting with making it work at the time and figured I'd probably break one or two. I might upgrade to something a little nicer in the future. Though, this cheap camera has pretty great value for the money. It's low light ability without IR is fantastic. The flipside, it tends to wash out a bit under very bright light, but that should be a matter of adjusting the auto-white balance or something like that.

    If I run the server stream at 640x480 I can get a fairly solid 13 fps with a slight (200ms) lag and ok image quality. I do get a fair bit of motion blur on that too. After seeing Tyberius' wifi encoder test run, I figured I should be able to do a lot better. I was right. I dropped the capture resolution to 320x240, maxed the image quality and was getting a very good quality clear image at 25fps, which also eliminated the motion blur. It even scaled up to 640x480 nicely on the client side. I know I can get gstreamer using the DSP and will probably try that out at some point, time permitting.

    Cheers,


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    Re: Woodstock - Mech Warfare entry

    And yet more good advise from Tyberius!

    I'll have to try out various video settings with my wireless connection unencrypted. It's currently doing WPA2.

    Cheers,


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    Re: Woodstock - Mech Warfare entry

    Quote Originally Posted by kamondelious View Post
    And yet more good advise from Tyberius! I'll have to try out various video settings with my wireless connection unencrypted. It's currently doing WPA2.
    I will concur, that removing the encryption also made a drastic improvement in my framerate/reliability for my setup. Just out of curiosity, what language are you developing in?
    Always outnumbered, never outgunned. Axiom Robotics

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    Re: Woodstock - Mech Warfare entry

    I'm doing all my development in C.

    I'm no expert in it, so I've got some learning curve going on there too, but it's a good time.


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    Re: Woodstock - Mech Warfare entry

    Quote Originally Posted by kamondelious View Post
    I'm doing all my development in C.

    I'm no expert in it, so I've got some learning curve going on there too, but it's a good time.

    Ever considered python? It's great for prototyping...then once you get it the way you want, you can re-write in C/C++. Since you mentioned you are on a short development cycle, you might consider it.
    Always outnumbered, never outgunned. Axiom Robotics

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    Re: Woodstock - Mech Warfare entry

    Indeed I have.

    I'm already fairly proficient with Perl, Bash & PHP and have explored those avenues as alternatives. I have always wanted to learn C and have been using Robotics and my motivational means to learn it. Adding another language at this point might hurt my head too much. That said, I have seriously been considering picking up Python for use on the client side of things instead of C. I think it's the only programming language I haven't heard anyone complain about and I probably could pick it up fairly quick. I know it's multithreading capabilities far and away exceed that of Perl and PHP.

    I want to use SDL on the client side for control/display goodness and there is a nice library for it and gstreamer. I'll have to explore how well ported it is to Python, but a quick search and things look promising. I did some work trying to make a go of it with Perl, but couldn't get it to work with SDL.


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    Re: Woodstock - Mech Warfare entry

    I'm hard pressed for time, so my usual "do it all the hard way" approach wasn't going to have me ready for Mech Warfare 2011. So I picked myself up an Arbotix starter kit and gave Woodstock a quick makeover.

    I've been playing with pypose since late last week. I did a sequence for getting up yesterday and took some video of it.

    [ame="http://www.youtube.com/watch?v=06G4Ua1ULuQ"]YouTube - Woodstock getting up[/ame]

    I'm hoping to connect the guns together with a servo so I can adjust their aiming, but if I don't have time, I'll lock them in place at a slightly inward angle.

    I was test firing the guns off a 3.7V 500mAh Lipo so I'm thinking that I can power them straight off digital IO ports of the Arbotix. I'm only planning to fire one at a time in an alternating pattern, but I need to double check that the Arbotix can handle it (pretty sure it can).

    I'm using two 1800mAh (143g) 3S Lipos at the moment and it seems to be giving me a good couple hours of playing with poses. I have four 2200mAh (122g) 3S Lipos ordered which should make life even better.

    More to come.


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