Author Topic: tetrapod  (Read 3418 times)

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Offline nagycncTopic starter

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tetrapod
« on: August 05, 2009, 02:38:52 PM »
Hello Everyone,

Just wanted to say hi to the group and show my first robot. It doesn.t do much just walks straight. The design
goal was to build a 4 legged walker that doesn.t collapse and able to walk by shifting its CG. I.ve built my own
servo controller using an Atmega168, servo signals are currently sent from a PC over RS232. The steps are
pre-programmed and the robot doesn.t have any feedback. I.m designing an enclosure with a button for FSR sensors
which I will add to the legs. The idea is to provide feedback when the leg touches the ground. An accelerometer
will measure the tilt and adjust the legs accordingly. I started to program an AVR32 (I.m very impressed with the
Linux SDK) to evaluate all the data. The current walker design has some major flaws. Futaba S3114 servos are too
week and for smoother walking I.d need to add 4 more servos to move the lower arms. But for now I.ll use the
robot I have to gain more experience with FSRs and the accelerometer before I start redesigning the whole thing.

[youtube=425,350]Bi_3rhX9WoQ[/youtube]


Pictures:
http://nagycnc.com/joomla/index.php?option=com_content&task=blogsection&id=9&Itemid=41

Thanks,
James
Vancouver, BC

Offline gaurav.p

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Re: tetrapod
« Reply #1 on: August 05, 2009, 09:44:21 PM »
wel come to the forums ,
gr8 bot
Big Things Come In Small Packages!!!

Offline robotcoder

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Re: tetrapod
« Reply #2 on: August 05, 2009, 09:48:28 PM »
Did you purchase the legs or did you fabricate them yourself?

Offline nagycncTopic starter

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Re: tetrapod
« Reply #3 on: August 05, 2009, 10:33:22 PM »
I designed the chassis and the legs with Alibre. Then exported the solid files into OneCNC CAM.
The parts were milled on a Tormach Personal CNC in my garage. 

Offline Joker94

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Re: tetrapod
« Reply #4 on: August 06, 2009, 05:47:30 AM »
nice bot and brilliant machining and parts.

The legs look like they need some rubber feet as alot of the power is being lost in the slide, or is that ment to happen

Offline wil.hamilton

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Re: tetrapod
« Reply #5 on: August 06, 2009, 06:18:44 AM »
very nice, i agree with joker that you could use something on the feet to give yourself some grip, you might be able to use heatshink tubing to give yourself the grip you need, if you indeed want grip
use the google.  it's your friend.

Offline Joker94

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Re: tetrapod
« Reply #6 on: August 06, 2009, 04:41:58 PM »
heat shrink tubing is a good idea, the rubbery kind not the plastic tipe

Offline nagycncTopic starter

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Re: tetrapod
« Reply #7 on: August 06, 2009, 06:05:32 PM »
Thanks for your feedback. Good point about the slipping but in order to move I have to shift the CG and to shift the CG I need to move two legs simultaneously. I’ll have to add 4 more servos so I could move the upper & lower legs separately this would prevent the slipping while shifting the CG.
I’ll attach this FSR sensor with mounting to the legs. I’m not sure what kind of non-slipping material I could use for the white button part. For now I’ll use delrin to see how it works and maybe later I’ll experiment with different materials (hockey puck?). The material also has to be machinable.

(the FSR sensor is the green long part in 3D draft, I’ll use a heatshrink to secure it to the leg)
« Last Edit: August 06, 2009, 06:13:35 PM by nagycnc »

 


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