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!


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.


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:

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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Since each rotating unit is a 'wheg' I guess the flexible sub-units are therefore 'legs'... although they're more tentacle-like than anything. I trialed some similar but much stiffer tubes on a previous prototype, but they were too rigid, and were prone to jamming in cracks, etc. The springs inside the current rubber tubes make them a little better, but ideally I'd have them somewhere in the middle, so a bit stiffer and shorter than the current model.
Mr. Lobster was fun - his descendants (planning is underway!) will be a lot more energetic =D

Edit: wow, the audio track has already been blocked - no more "What's New Pussycat?" by Tom Jones =/
Edit2: ok, new video is up and audio is back.

I would have liked to see the cat take your efforts more seriously. I find the best robots are the ones where the pets don't know if they should run away from or attack.

Considering my cat is happy to chase cats twice his size (as long as mum or dad are nearby) I don't think Mr. Lobster should consider it too much of an insult =)

When Mr. Lobster was charging the cat kept his distance - not sure whether that was due to boredom or because of the awful whine the on-board boost converter makes... sounds like a distressed camera-flash charger.

Video now posted!
I'm guessing the audio will be neutered in short order, so I'll probably have to re-upload by tomorrow anyway =D

And very original/impressive setup with the fuel cell and hydrogen/oxygen tank.

Are you a chemist (too) or how did that even occur to you?


I'm a mechatronics engineer by profession, which means I've picked up a fair amount of chemistry-based knowledge through studying the properties of different materials. Plus with all the recent advances in MEMS, quantum and nanotechnology, I feel that a good understanding of at least the fundamentals of chemistry is important.

As far as coming up with the idea, I've been interested in alternative power for mobile devices (mostly autonomous robotics) for ages now - I like my critters to be able to look after themselves =)
I knew a guy working at my local JayCar, so I was able to pick up the double layer fuel cell for quite a good price a few months ago. Apart from basic testing (charging up to power motors, etc) I hadn't really made use of it because the voltage output is so low, so I figured it was about time I did something about that... Originally I was going to use small plastic bottles to store the hydrogen and oxygen, but the more you pump into the bottle the higher the pressure gets, so it becomes hard for the fuel cell to generate more gas (i.e. the charging capacity becomes quite limited). On the other hand, flexible containers like the balloons are able to store much more gas at lower pressures, but they're prone to scrapes and punctures...
After a bit of puzzling I came up with the idea of combining the two and sticking the balloons inside a plastic bottle =D
Not exactly a genius idea, but the simple ones are the ones that work!

...a mechatronics engineer. I myself have been working as a selftaught programmer for years. I recently started studying IT enginnering. I thought very long and hard about choosing mechatronics engineering instead, but in the end decided to go for IT. The thing is my main interest is AI and if I'm to make any contribution to robotics some day it will be in the creation of robot brains rather then their bodies.

However I'm still considering whether I should have chosen mechatronics instead :/

Anyway cool robot indeed :)

My university only had about 40 places for the mechatronics specialisation, since they'd only started it 2 years beforehand, so naturally I put mechatronics first on my list of choices. If it was the hardest to get into, it must have been the best right?

To be honest I don't think it'd take much work to learn any of the topics you're not covering, and in any case technology is moving so fast that by the time you learn something it's already out of date =)
University is more about learning how to learn than simply teaching you what to do. Your software/programming knowledge will no doubt help you learn other things more quickly, in the same way that my hardware/control background helped me learn about programming.

Ok, this is freaky, somewhat like Frits would make, except not of wood, polymorph, and hot glue. Good job!

Really like the fuel cell usage, hope it moves well.  


I gotta see this one in action

-And could you please make a walkthrough about the whole fuel cell gizmo? That's really exciting.