Let's Make Robots!

Mr. Lobster


Meet Mr. Lobster.
He's big, ugly and lazy - but he's also environmentally conscientious.
Now in full-colour video! Wow!

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The small photovoltaic array on his head powers a 600mW double PEM (proton exchange membrane) fuel cell, causing the fuel cell to split stored water in hydrogen and oxygen gas. The gases are stored in 'helium grade' balloons inside the tank that makes up Mr. Lobster's 'abdoben'.
The fuel cell then consumes to stored gases and converts them back into water, producing around 2V @ 500mA which is boosted by an on-board voltage converter. The voltage converter charges a 1F super-capacitor, which is used to power the two microcontrollers and motors.

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As for behaviour, Mr. Lobster just wants to spend all day frolicking in the sun. If he's not yet fully charged and there's ample sunlight he'll just laze about, but if he's 'full' he'll wander about aimlessly. If there's a sunnier patch nearby he'll move towards it, otherwise if it's dark he'll shut off as much hardware as possible to conserve energy - the voltage boost converter goes into a low-power state, and one of the two PIC16LF628A microcontrollers is turned off.
The 'master' PIC handles decision making, reading of LDR couples and boost converter management. The 'slave' PIC monitors the stored power level and controls the motors using quantised charge feedback. The PICs communicate via two-way asynchronous USART (like typical serial comms, but without a clock).

Up until yesterday Mr. Lobster looked like this:
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So as you can see he's changed quite a lot in the last 24 hours =D
Sadly one of the feedback circuits for his forearm motors went ballistic and there was no time to track down and correct the problem. I tried to manually control the walking gait, but without feedback Mr. Lobster was so inept that he couldn't walk at all.
The whegs (wheel-legs) were actually part of the original concept, so I quickly added those back in. They're simply made of thick-walled rubber gardening hose with a curtain-wire spring fitted tightly inside. They're not terribly effective on smooth carpet, but Mr. Lobster is surprisingly agile over grass or rubble.

As requested I've written a bit of a walkthrough on using PEM Fuel Cells which you can check out here.

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Nice, the cat has a new friend to play with. I love the fuel cells idea... congrats. :)

Claudia will be sending you out a Caterpillar robot kit tomorrow :D  Your design was definitely unique!

Please email her with your name address and phone number.

Very original. I just learned of fuel cells yesterday on this site. New to me but a bit pricy at the moment. I just started working with a solar panel today.. So far learned continous servos work better ( less power) then LM 298 H bridge bot with servos convertted to DC motors. So far I am using strictly solar for now and planning to use cell phone batterys later down the road. I like the unique motovation design. Have you tried it on grass yet? How long does it have to sit in sunlight before being able to store enough gas to move?

 

Hehe, I have to admit I wouldn't have bought a fuel cell if I hadn't been able to 'negotiate' a special deal on the one I got...
As far as power-to-weight ratio goes, you can beat a good rechargeable NiMH or Li-ion battery. Interesting about the servo controllers being more efficient, I was just wondering about how good they were yesterday.
Mr. Lobster performs better on grass than on concrete, unless it's wet, then he has all kinds of trouble =) If he's totally tapped out of power he can usually get enough energy to start moving after about 2 minutes in moderate sunlight, thanks to the boost converter and the efficient, highly geared motors.

Woohoo!

Thanks for all the kind words and interest guys, there have been a few tough patches as with any project, but on the whole Mr. Lobster was a lot of fun.
If there's anything else you'd like to know about Mr. Lobster, don't hesitate to ask. 

thinks maneuver is really excited ;)

Congrats TeleFox! You've definitely given me some inspiration with this.

Hey. You just won the Mr. Basic challenge V2.0. Congratulations!
You got a freaking fuel cell? WHERE DID YOU GET THE FUEL CELL?

http://letsmakerobots.com/node/12583#comment-36143

Although I'm pretty sure you can get them cheaper, especially since you're living in the US. What I really want is a DEFC (Direct Ethanol Fuel Cell), those thing have a sweet power density factor.

Wow. Cool video. Are you getting the effect you want with his locomotion? It looks like a more grippy surface on his... uh, his... uh, his whateveryoucallems might move him along more effectively. Or maybe do something to stiffen the whateveryoucallems.

Anyway, very cool style of motion and power. Your cat seems well pleased too.