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Creepy Hybrid

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Posted: 2009-07-29 12:46 
 Post subject: Re: Creepy Hybrid
I suppose it could get quite complicated!

I've got a wireless camera on a 4WD, nothing great. I'd like to be able to focus it through a digital camera and use it to "aim". Optics aren't cooperating.

Don't know about the pix. After I get the names right (case must match) for the file to reference, they show up quite dependably for me.

Alan KM6VV

tnay wrote:
I'm afraid it's nothing like that. That is waaay to complicated. :lol: It's just a simple code. Since the transmitter use PPM method, I just treat the pulse width as a range of value.

p.s.: I was able to see your previous image this morning, now I cant see it, include the image in your last post. :?:

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Last edited by KM6VV on 2009-07-29 14:47, edited 2 times in total.

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Posted: 2009-07-29 13:24 
 Post subject: Re: Creepy Hybrid
Robot Dude wrote:
tnay wrote:
Letting the brain go wild, I imagine a seperate 2.4ghz camera display lifeview on a colour GLCD. :D Ready for Mechwar!!! But that is just waaay above my current programming level. :roll:


Don't make the mistake I did assuming cheap 2.4ghz "spy" cameras will work for Mech War. They are saying no go and wifi is the only show in town for Mech War bots. If you are saying use a channel of some other 2.4ghz system it's not got the bandwidth to do video. That's what I'm getting from them anyway.


Really? I guess it is still not fast enough for video streaming. But wifi also run at 2.4ghz right? Wifi camera doesn't come cheap, don't they?

Anyway, I did look up for some info on camera, and it seems like we need something like >100mhz processing speed for 30 fps of vga video streaming. Pick that up from sparkfun forum. Very challenging. It sure is a good-to-have features. I hope lynxmotion got their own camera module. :wink:

Not exactly for mechwar, but I do like to see the world through the eyes of robot. at ground level. :wink: Like going under the couch, exploring the nature.


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Posted: 2009-07-30 12:01 
 Post subject: Re: Creepy Hybrid
Can you see me now?

How about my new Avatar thingy? Some of my youngest son's work. "Retro Spaceman", from a project he's working on.

Alan KM6VV

tnay wrote:
p.s.: I was able to see your previous image this morning, now I cant see it, include the image in your last post. :?:

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Posted: 2009-07-30 12:58 
 Post subject: Re: Creepy Hybrid
tnay wrote:
Really? I guess it is still not fast enough for video streaming. But wifi also run at 2.4ghz right? Wifi camera doesn't come cheap, don't they?

Anyway, I did look up for some info on camera, and it seems like we need something like >100mhz processing speed for 30 fps of vga video streaming. Pick that up from sparkfun forum. Very challenging. It sure is a good-to-have features. I hope lynxmotion got their own camera module. :wink:

Not exactly for mechwar, but I do like to see the world through the eyes of robot. at ground level. :wink: Like going under the couch, exploring the nature.


We bought the Trendnet wifi camera for ~$99.00. The difference is in compression not transmission frequency. Sending raw video fields apparently is extremely inefficient.

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Posted: 2009-08-03 19:36 
 Post subject: Re: Creepy Hybrid
Jim,

How thick is your "Lexan Quadrapod Body Kit - Mini" chassis plate? Is Lexan stiffer then Polycarb for the same thickness?

As I mentioned earlier, my Polycarb chassis was bending under the weight of 4DOF legs. I'll check my thickness again, but I think it was 1/8".

Any interest in putting a few more holes (for LPAs) in your 'quad chassis?

Alan KM6VV

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Posted: 2009-08-05 11:05 
 Post subject: Re: Creepy Hybrid
I had this answered yesterday and about 8:45. But the power went out before I could send it. All the backup supplies held on long enough for us to shut everything down. lol

Lexan is a trade name for polycarbonate.

Polycarbonate: Lexan, Macrolon
Tough, bendy, not brittle...

Acrylic: Plexiglass
Tough but brittle...

If I were making a single panel as a chassis I would probably go with 2 1/8" panels glued or bolted to make one stronger part, or go with 0.09" aluminum.

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Posted: 2009-08-05 14:20 
 Post subject: Re: Creepy Hybrid
OUCH! That could have been disastrous! Glad you're back up. No worries on the slight delay.

OK, so they're the same. Nice stuff, for plastic!

I have scrap Plexiglas as well. Plexiglas and Polycarbonate are great for quick prototype and proof-of-concept pieces; although I prefer to work in aluminum (also brass and lead-alloy steel).

I'm going forward to an aluminum chassis, I might even retrofit the Creepy Hybrid's chassis with the additional servo body cutouts and threaded holes.

I'm still kicking around the idea of threaded servo mounting holes vs: matching slots. Threading 20 or so holes may run your costs up, and not be practical for production.

One thing I became acutely aware of was the dependency on the thickness of the "bracket" material of the LPA (as I'm sure you're aware). When I "ported" the LPA into my chassis design, I came up with a mismatch in the axial alignment of the gears. No surprise! My chassis is thicker then the LPA bracket! The solution, of course will be to mill out a pocket to adjust the LPA bearing height to match the lower-seated servo. No problem! However another machine step.

Alan KM6VV

Robot Dude wrote:
I had this answered yesterday and about 8:45. But the power went out before I could send it. All the backup supplies held on long enough for us to shut everything down. lol

Lexan is a trade name for polycarbonate.

Polycarbonate: Lexan, Macrolon
Tough, bendy, not brittle...

Acrylic: Plexiglass
Tough but brittle...

If I were making a single panel as a chassis I would probably go with 2 1/8" panels glued or bolted to make one stronger part, or go with 0.09" aluminum.

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Last edited by KM6VV on 2009-08-07 19:00, edited 1 time in total.

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Posted: 2009-08-05 19:33 
 Post subject: Nice!
Cool project! I'm looking forward to the articles


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Posted: 2009-08-06 00:17 
 Post subject: Re: Nice!
Thanks!

I can't wait either! There are a lot of photos, charts and CAD drawings, as well as considerable text in the two-part article. I hope you enjoy it!

Alan KM6VV

rhewitt wrote:
Cool project! I'm looking forward to the articles

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Posted: 2009-08-06 04:55 
 Post subject: Re: Nice!
KM6VV wrote:
Thanks!

I can't wait either! There are a lot of photos, charts and CAD drawings, as well as considerable text in the two-part article. I hope you enjoy it!

Alan KM6VV

rhewitt wrote:
Cool project! I'm looking forward to the articles
hi alan. Well done with the news for the artical. Cant wait to read it. Im starting work on another quadruped project very soon. Good luck with the competition, things looking good for ya. Jonny.

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Posted: 2009-08-06 13:09 
 Post subject: Re: Nice!
Hi Jonny,

Thanks! Yes I'm really proud of this article.

A new 'Quad you say? What leg layout? I found out that my initial splayed leg layout would probably make it difficult to walk. Maybe that's why all the mammals you see have the more upright legs. Crocks, Monitor lizards and the like (reptiles) have the splayed legs, 'tho. I think it would be wise to mimic maybe a cat or dog's basic proportions initially.

Alan KM6VV

innerbreed wrote:
hi Alan. Well done with the news for the artical. Cant wait to read it. Im starting work on another quadruped project very soon. Good luck with the competition, things looking good for ya. Jonny.

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Posted: 2009-08-06 23:00 
 Post subject: Re: Creepy Hybrid
I think you might notice that when heavy lizards with splayed legs are walking slowly (not talking advantage of momentum when running) use their tails to help leverage themselves.

Animals that walk "taller" have less stress on their leg joints to keep them upright and the force seems to be directed more down through the physical geometeries of the leg.

Although I personally haven't "proved" this but it seems to me that through experimentation it takes more joint torque to maintain an upright position in a mammal quadruped configuration than it does a insect quadruped configuration.

The robotshop formula seems to take into account all of the forces and torque in leg design, at the hobbyist level.

http://www.robotshop.us/robot-leg-tutorial.html

Perhaps these formulas explain the difference in forces vs angles in different leg positionings.

Also, never forget that the taller the robot is, the more you have to work to maintain balance.


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Posts: 26
Posted: 2009-08-06 23:25 
 Post subject: Re: Creepy Hybrid
Also, in case someone didn't already put it out there, some great resources are:

MIT OpenCourseWare: Intro to Robotics

http://ocw.mit.edu/OcwWeb/Mechanical-Engineering/2-12Fall-2005/CourseHome/index.htm

and Stanford's Intro to Robotics Videos:

http://www.youtube.com/view_play_list?p=65CC0384A1798ADF

Don't forget your Linear Algebra!

http://www.youtube.com/view_play_list?p=E7DDD91010BC51F8


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Posted: 2009-08-06 23:36 
 Post subject: Re: Creepy Hybrid
Yes, that's a good observation. Probably aids in the swing of the body that apparently helps them shift their feet forward.

The leg stresses of large mammals practically demands a vertical leg! Something like the cosine of the joint angle applies.

A cat would be my target.

It takes hardly any joint torque to support a let that's vertical! A spayed leg has several joints with a considerable static load on them. But yeah, a test would be good. The weight, leg and joint count would have to be equal for the comparison. Actually, a single leg would be sufficient for the comparison.

The Roboshop tutorials are interesting, but might be limited to sprawled leg configurations from a cursory examination.

Height can be your friend for balance!

Alan KM6VV

thesa1nt01 wrote:
I think you might notice that when heavy lizards with splayed legs are walking slowly (not talking advantage of momentum when running) use their tails to help leverage themselves.

Animals that walk "taller" have less stress on their leg joints to keep them upright and the force seems to be directed more down through the physical geometeries of the leg.

Although I personally haven't "proved" this but it seems to me that through experimentation it takes more joint torque to maintain an upright position in a mammal quadruped configuration than it does a insect quadruped configuration.

The robotshop formula seems to take into account all of the forces and torque in leg design, at the hobbyist level.

http://www.robotshop.us/robot-leg-tutorial.html

Perhaps these formulas explain the difference in forces vs angles in different leg positionings.

Also, never forget that the taller the robot is, the more you have to work to maintain balance.

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Posts: 26
Posted: 2009-08-06 23:41 
 Post subject: Re: Creepy Hybrid
Height can be your friend for static balace but as soon as you try to make the robot walk (shifting the center of gravity to balance over three legs) the force/momentum produced by that shift at such a tall moment arm can work against you.

Quote:
The weight, leg and joint count would have to be equal for the comparison.


What do you mean?


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