Draco 08 - Quad Mech

[elaughlin]

Ok, I am finally getting around to starting my project thread for the Mech I am working on for Mech Warfare 2011. I will definitely be going, and I have to get it done before the time comes, so I work on some part of it at least for a little while everyday. I might not get so much physical work done each day or week, but I am learning things, like Autodesk Inventor, C++ Programming, Electronics, etc. Guys like Tyberius, Inxfergy, Upgrayd, and Webgeek have all helped me out a ton already. Even if not directly, I have used a lot of their tutorials at least to get my stuff up and running.

Alright, so to get on with what has happened so far with my Mech. It is going to be a Quad, seeing as I wanted to go with a Biped, but I knew it would be a little much for my first run at this. Plus I think I came up with a really nice design so far for what I want to do. I am using the Robotis Bioloid Comprehensive Kit so far. (That was a blast to put together all of the projects that come with that, and had a walking Biped, Quad, Dinosaur, within a day per project. Its a good build all on its own.) I have stepped past the CM-5 now and am using the Arbotix Robocontroller setup from Trossen Robotics website. I got the startup kit with the 2 Xbees and the AVR Programmer and Xbee explorer board. Now then, I assembled just a mock up of something That I am trying to do, just using the Bioloid brackets. So I haven't customized any parts yet, but after assembled, I used the NUKE and PyPose software, uploaded them to the Arbotix, and had my very own walking Quad Mech Robot. It is getting power through the Power Block that came with the Bioloid Kit right now, and that runs throught the USB Bioloid Bus Board to the Arbotix. Oh, and it is also running wirelessly via controller through the Xbees to my computer, and just test run through the NUKE program. So thats what I have done so far with the physical aspect of my Mech. I will be posting pictures and a video at the end of the post.

The future plans for the Mech, are to custom build the torso and chasis. Attach 2 tank aursoft guns. Install a Trendnet IP 110 camera for vision. Add LiPo batteries for power. Be controller from a PS# controller possibly, unsure how hard that is to do right now. (Will post about that in another thread, but answer here also if you want.) Thats about it. I want to keep it simple, not too many extras on it (i.e. range finders, IR, etc.). I want to keep it as light as possible for quick movement around the arena.

If you have any questions about what I am doing with it or comments about any parts, please let me know. This is my first robot build, so I need lots of help and pointers.

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[elaughlin]

I forgot I had a PDF file of the lay out of the legs if anyone wanted to see. You can move it around and see the different angles of the legs.


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[Tyberius]

Have you tried out the amble gaits from NUKE on this bot yet? I think you can switch between them with the middle most buttons on your ArbotiX commander.

[elaughlin]

I have not tried that. I dont have the Commander to use. I dont have any controlling device yet, except for the computer.

[Tyberius]

I think there is a way to do it via the software version of the commander. Fergs?

[lnxfergy]

Good looking bot!

As for Tyb's suggestions: the default NUKE sketch doesn't currently include the button functionality that he is thinking of (It's something I tend to add, and it will be stock in the next release of NUKE/PyPose). The Python-based ArbotiX Commander GUI also doesn't have buttons... another thing that will be fixed in the next release. You can do all of this programmatically though. To switch to using amble, just change the line near the top of the setup() function that says:

gaitSelect(RIPPLE);

to:

gaitSelect(AMBLE);

This will move 2 legs at once -- for some bots it's more stable than a ripple, for others it's not -- this mostly depends on how wide your stance is. The biggest thing here though is: you can increase the speed by adding a multiplier. The default sketch only will go -100mm/s to 100mm/s. In your main loop, you change the line that says:

Xspeed = command.walkV;

to:

Xspeed = 2*command.walkV;

Which will double the max speed. You might also be able to do a 3 or a 4 instead of 2x. Realistically speaking, 200-300mm/s is probably close to the limit of what can actually be driven through a webcam.

-Fergs

[elaughlin]

Wow, thanks a lot. That is really something I am looking to do. I want to have a good amount of speed out of my Mech. Hoping it will be low enough COG that I can work on speed more than having to deal with stability, and that is something the Quad as a big advantage over Bipeds.

When using the different gait and speed modifications, can that be seen while "Test Run"ning in the PyPose/Nuke, or would it only be seen when I am really commanding it from a different source?

[lnxfergy]

The "test" in PyPose/Nuke is just a virtual Commander, dragging the cursor up/down is like pushing the joystick forward/backward. This sends Xspeeds in the range of -100mm/s to 100mm/s. By scaling it on the bot, we can make it move faster. So, yes, if you change your loop and re-upload the code, the bot should walk 2x as fast in the forward/backward directions.

You can actually get fairly fancy with this portion of the code: by varying speeds and by switching gaits if the speed is at a certain point. Issy2 walked up to 300mm/s in forward speed, if he backed up, we automatically switched to the Amble gait, and capped the reverse speed at 150mm/s.

This page has a few notes about the Gait Engine: http://code.google.com/p/arbotix/wiki/NukeTuning

-Fergs

[elaughlin]

I have a question for you, how come recently, my IDLE Python is getting error every time I try to open it. It has two pop-up errors:
1 - IDLE Subprocess Error
X Socket Error: Connection refused

2 - Subprocess Startup Error
X IDLE's subprocess didn't make connection. Either IDLE can't start a subprocess or personal firewall software is blocking connection.

I did look through the firewall protection, and allowed access for anything Python pretty much that I could find as a possible fix, but still always get that error.

I can bypass it though by going to a .py file, and choosing to edit it, then it will open up IDLE fine, and can run it. Confused, if I have to always open the file first, its not a problem, but thought maybe you'd have an idea about it.

[lnxfergy]

I have a question for you, how come recently, my IDLE Python is getting error every time I try to open it. It has two pop-up errors:
1 - IDLE Subprocess Error
X Socket Error: Connection refused

2 - Subprocess Startup Error
X IDLE's subprocess didn't make connection. Either IDLE can't start a subprocess or personal firewall software is blocking connection.

I did look through the firewall protection, and allowed access for anything Python pretty much that I could find as a possible fix, but still always get that error.

I can bypass it though by going to a .py file, and choosing to edit it, then it will open up IDLE fine, and can run it. Confused, if I have to always open the file first, its not a problem, but thought maybe you'd have an idea about it.

I really don't use IDLE, I just start python at the command line. I seem to recall this being a problem with IDLE back when I was a TA for a python based course a few years ago. As I recall, it had something to do with how you opened IDLE, but I really don't recall.

-Fergs