More and More, Bigger and Bigger

I'm finally up to 4 servos, and 5 snake segments. Motion/programming-wise, I'm still just up to rolling on the ground, but I've only put a few hours into that, so there will definitely be more cool gaits to come. (think climbing stairs, climbing trees, etc) As of now, there really is no program that makes it slither or roll, rather, I have two joysticks (2 axises each) where each axis on the 2 joysticks controls a particular servo in the snake. This lets me get to fool around with it much more easily than writing code, debugging, etc. Once I get the hang of controlling the articulated motion with the joysticks (which is MUCH harder than it sounds) I'll be able to write a program that will do it much more efficiently and effectively.

I've fully moved myself off of the two 6V lantern batteries in parallel, and onto a salvaged computer power supply. Since the servo controller runs on 4.8-7 volts, I'm using the 5V rail (red wire) from the power supply, which provides up to 20 amps. Each servo draws about an amp for normal usage, more when stalled.

Again, I can't stress enough that none of this would have been possible without the help of Robotics and Beyond. Anyone or anyone who has kids who have any interest of robotics, engineering, electrical, or just building wicked cool stuff, should absolutely check out their summer program. As a past student and current mentor, I can say that it was a great way to introduce me to the field of engineering.

Again, here's some more updated pictures:

Here it is after pulling itself up vertically on just 2 servo motors. You'd never expect it, but these servos have about 21 kg (300ish oz) of torque. These guys are real finger crunchers.

In a rolling motion, notice the short (but existent) sin curve on both the X and Y axis.

Heres my end piece with power switches, plug, and even a switch guard for the main power toggle switch. See the cracks on the plexiglass in the bottom left? Moral of the story: don't run debugging programs on a concrete floor...

Here's the two joysticks that are currently being used to control everything.

And finally, my 'new' power supply. God bless the guy who thought of grounding the green rail to ground with a paper clip to turn on the PSU, you have made my life so much easier.

That's it for now, hopefully next post I'll be able to put up some videos of it in action.

More! More! More!

So, not too much has changed design-wise, except for the addition of the electronics/control module to the snake in the last segment (the Plexiglas one). As of now, that only contains a servo controller, but in the future, it will have power switches, a microcontroller, and maybe even a bluetooth modem for wireless capabilities.

So, here's some more pictures:

Ready to be wired up

Electronics/control segment. No servo means more room for the controlling elements.

All bent up

So even though there's only 4 segments, it's possible to get it to move across a surface. As the number of segments goes up, it'll be able to do a lot more cool stuff. On a positive note though, my power supply is no longer a 6V lantern battery, and rather, a wall transformer. If the three amps that gives isn't enough, then the next step may be to salvage a computer power supply and use one of the 6V rails from that. It's not incredibly professional, but it works just as well as buying a regulated power supply just for this.

That's it for this time. Hopefully next time, I'll be able to put up some videos of it's motion.

Happy Holidays!

quick note to everyone

For those of you who don't know what I'm designing and building, I'm working on building a robotic snake as an biomimicry internship for the Robotics and Beyond summer camp. If anyone's interested, check out their website:

http://www.roboticsandbeyond.com/

Anyways, back to what I was talking about before. What I'm working on building is a robotic
snake, capable of moving in both the X any Y directions. Some guys at Carnegie Mellon did the same thing (and also did an incredible job), and you can see their work at:

http://www.youtube.com/watch?v=T62E-_pQt3c
and
www.modsnake.com

Once finished, my snake should be very similar to that, with probably roughly the same number of degrees of freedom. Some more pictures should be up tonight or tomorrow.

Anyone with questions/comments, I'd love to hear from you.

Taking Shape!

Finally, it's really starting to take shape and start to resemble a snake! A few updates from my last post include: an additional segment and an extra servo reinforcement that hooks the back of the servo into the rotating chassis, as well as the horn. This allows for the force/stress to pass through the snake through two points, and not just the one that had originally been planned. This addition greatly improves the structural integrity of the snake. So far, I have two joints in the X direction and one in the Y. After one more in the Y, I should be able to get some very basic motion patterns down, but nothing as good as the final product.

I'm getting to the point where I'm comfortable enough with the design that I'm getting ready to get a nice big sheet of aluminium for the chassis pieces, and weaning off the scraps laying around the garage. Also, I'm getting to the point where more servos are going to be

necessary, and not just the 4 I got to start with.

I'd like to make a quick thanks to Michael Morrissey and Robotics and Beyond for providing me with the chance to do something as cool as this. Without their help, I would never have been able to do this.

Now, here's some more photos of the status of the project so far:

A shot of the segments each twisted at 90 degrees so you can see the different aluminium chassis pieces connected together.

The segments angled at slight less angles than before.

Another 90 degree shot from a different angle.

All the segments in-line.

Another shot of everything straight together, and you can see how the different pieces interact.

Coming Together

12/3/09

This project's no longer just thoughts and crude drawings scribbled out on napkins, or even the CAD sketches I've put together. As of now, something worthwhile exists. It's not too complex yet, seeing as I only have one joint of the snake flopping around on my desk, but, it's there, it's moving, and it's working just as planned. It shows that it IS all possible, and I expect to have up to 4 sections put together within the upcoming week. Here are a few pictures of the work so far:

Here's a preliminary shot of the first round of work, with just one servo and one chassis mount

Here's another shot of the second servo mounted into place, with the top chassis mounted in too.

A shot from the side

Here's a shot of the two servos without their top chassis piece holding them together.

blast off

So, the snake idea has been starting to take shape, despite the fact that it still looks nothing like one, and won't for a while at least. However, I did manage to overcome my first expected problem: getting a live data feed from the computer, through the basic stamp microcontroller and to the servo controller, in turn moving the servos. It's not a 2 independent axis sine waves working together to coordinate a snakes movement like it will be in the future, but rather, a single servo with 2 positions, chosen by whether the the mouse button is depressed or not. However, the hard part has been taken out of the way, and the more complex multiple servo control should be relatively easy.

Hardware wise, I've just come out of the crude "folded index card mockup stage", and have entered the stage of using real materials, including aluminium, plexiglass, and lots and lots of screws. It still resembles no snake you have ever seen, because it's literally just part of one of the many segments the finished product will have.

I've included a few pictures to document my progress:

A Close up of all the electronics powered up and ready to work

Circuit boards, power sources, and servos

Just the electronic equipment, before being hooked up

A quick view of just some of the code used for the most basic motor functions.

A servo and its aluminium mount: just a small part of one of the many sections of the entire snake.