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The Octapod Project

#1

Grettings everyone!

After doing a lot of research over the past several months on components and such for a robot and what to build, I have finally settled on my project. It will be a true Octabot, in that it will have 8 legs on an octagonal chassis. Actually, it will be a bit of a hybrid, since it will also have a two or three wheel drive for times when it is on flat terrain.

I’ve already determined that I will be able to control 24 servos (8 3DOF legs) plus the wheeled drive with a single SSC-32 servo controller. I’ll have 3 servo ports left to control a small 3 or 4 DOF arm. That will take care of using all a SSC-32 has for servo ports. :slight_smile:

I plan to start all this off with a custom octagonal chassis patterned according to the servo erector set parts and hole patterns. I just have to find somebody to make the octagonal chassis sections for me for a reasonable fee.

The 2 or 3 wheel drive will be mounted completely within the form factor of the chassis so it will not interfere with any of the legs. The legs will come out direct from the chassis as with a standard round hexapod. I’ll start out with 2DOF legs and later upgrade them to 3DOF. I am on a fixed income, so this will all take quite a long time to build. I will start out with just the wheeled drive system so I can have something to play with while working on the legged subsystem.

As for controlling all of this, all motion of the platform will be handled by a single small microcontroller. This will probably end up being a controller such as the Oricom Technologies OOBOT40-3 board and a Java microcontroller chip programmed by Muvium. I’ll start out with the ooPIC that comes with the board and move to the Java chip later on. I may also use a bot board with a Parallax Java Stamp on it for the motion controller.

Ultimately, there will be a master controller added which will run Linux and handle everything else I want to do, including added computing power, wireless link, etc. I want to coordinate everything via an I2C or similar bus for sensers and inter controller communication.

Well, this is pretty much what I have down on paper for this project at present. I also have a couple designs for custom 3DOF legs I want to try out at some point. Right now, I am just getting together all the support components I need (bench power supply, batteries, charger (have one 7.2v pack and charger I just got from Lynxmotion), etc. Hopefully I can find somebody to build the bot chassis soon for a reasonable cost.

8-Dale

#2

Sounds interesting. I would like to see pics of your progress when you begin. I also like to design web grapgics for fun. If you click on my web link at the bottom of this reply, you will see all my custom graphics I created for my project website.

#3

I will be documenting everything as I move into the build phase. Hopefully this will be next month for the wheeled part of the platform. I have found a small octagonal base I could start with at Budget Robotics, and it already has a two wheeled drive. I would just have to add another wheel if I decide to go the three wheel route. I would prefer to start with a custom octogonal chassis though, because I can have it made with all the SES compatible holes already drilled.

I am going to change one of the sections of one of my websites (I have 3, all with forum sections) into a Robotics section where I will have all my documentation, musings, etc. (as well as some here of course).

8-Dale

#4

you have a link to the base you have.

also since your looking to have a 8 legs w/ 2-3 wheeles have you though about using sketchup or some other cad program to draw up what you need?

#5

This is the base I will start out with if I can’t get the custom one right away. I should be able to get this next month.

budgetrobotics.com/shop/?sho … art=328445

Yes. I have been looking at CAD software for the past few weeks, but there doesn’t seem to be anything real decent I can afford. I have had some training with AutoCad, but that is WAY out of my range, as is Solidworks which I would love to have.

#6

There’s a free CAD program out there for us Windows freaks.
It’s called MSPaint.
With a dash of figure-drawing knowledge and a nice pile of time, you can hammer out ideas pretty well.
Here’s a recent “CAD” of mine:
f10.putfile.com/thumb/8/23717122913.jpg
If you look closely, I’ve actually written true values on the caps and drawn the right colored stripes on the resistors.
Yes, I’m pathetic.
:stuck_out_tongue:

Of course, you don’t get the fancy-shmancy 3d interaction that you get with Solidworks, but you get what you paid for.
As for those 2-D limits, they didn’t seem to much affect Michaelangelo, now did they?
:wink:

#7

This works, as do my scribblings on paper, up to a point. However, when I want to give somebody a drawing to show how I want my chassis parts to be made, I need more - including dimensions. Right now am putzing around with CadMax, VariCad, and others.

I still have to figure out how to make these programs show the additions I need off of each octagonal flat where the legs will be attached.

I also still have to figure out how I will attach the legs if I end end up having to use the Octabot II chassis from Budget Robotics. I need some way to make this chassis compatible with the SES parts. but I don’t like any of the methods I have designed so far for structural reasons.

No you aren;t. :stuck_out_tongue:

Ah, if only I had even 1% of Michaelangelo’s talent… I am not one of those artistic types, except when it comes to computer programming and design tasks with hardware (which I usually can not build myself due to being mechanically challenged)

#8

Nick,

You are a true master with MS-Paint! I thought that you used some kind of sketch program! :laughing:

#9

He sure is! :smiley:

I have been doing a lot of design work on two different chassis setups I could use for my Octapod.

For the first, I could just bolt a multi-purpose braclet (ASB-04) to the Budget Robotics Octapod II chassis, one for each leg. I think this would be strong enough to support the legs and keep everything attached to the chassis. The existing wheel drive will be used with the addition of a third wheel to replace the balance caster. I have another idea for this too, but will keep that secret for now in case I do it - have not quite figured out how to make it work yet but know it is doable.

For the second, I could do everything with 100% SES parts using two of the hexagonal tube connectors (AHC-03) connected in turn by a section of tubing. Four legs would come off the sides of each hexagon using various brackets (Long “C” or Offset). Oh yes, I have also figured out a way to attached a four wheel drive all wheel independent steering system to this. :smiley: I’ll be in servo heaven (or maybe hell) if I go this route, but it will sure be different from anything I have seen anyone else do.

#10

I just noticed your reference to Sketchup and I am checking it out right now.

Thanks!

#11

I know your wanting 8 legs and Lynxmotion sells a 6 leg base … Have you though about using that as a Guide or starting point. to hold the legs.

example would be take there wheele platform (Bottom layer only) and attached it to LM hex body. Just to get thing rolling.

Sketchup is a nice free tool, Just wish I had some CAD expreiance.

#12

Yes, I am considering doing this just so I have something to hang legs pff of for testing, and it would give me experience with the round hexapod in the process (a good thing). :wink:

Yes, I think this is what I may do. I can build the wheeled base separate, test it, get all my legs built and tested, and then put them all together on the hexapod body (6 legs at a time, of course). This seems like it would be a good progression towards my end goal. Then it will be time to get the custom Octapod base made so I can put it all together.

I think these steps are something I can manage and it won’t require me to to everything all at once. And, at one point I will actually have two complete robots (wheeled rover and hexapod).

I downloaded Sketchup and am playing with it now, but I only get a total of 8 hours play time in the demo. The full version is not free - it costs $495.00, which I am thinking is worth the price now.

In just about 30 minutes of fiddling with Sketchup, I was able to get this drawn, and I am definitely no artist:

http://www.thedynaplex.org/robotics/img/octopod_base.jpg
I have not been able to get this kind of results from any of the CAD pacakges I have tried or am trying now - at least not so far.

#13

You could always try Google SketchUp. I haven’t been able to play with it yet, but it is free. :wink: From the image on the page I linked, I’m not even entirely sure it’s the same type of program, but like I said, it’s free. :laughing: If you try it, let me know how it works!

#14

Wow, I completely missed the reference to Google Sketchup when I went to get Sketchup earlier today! Yes, it is from the same company I got the trial of Sketchup Pro 5 fron, so when my time runs out on that I will switch to Google Sketchup and try that out. Thanks for the info! I’ll post my experiences with Google Sketchup when I take it out for a spin.

#15

Google Sketchup is a really nice 3d program. It is the easiest to use from the ones I tried (I tried like 5 or 7 3d programs). If you want to make a quick 3d drawing its pretty easy to do, but if you want to make an exact replica of something (exact dimensions) then youl be in for a lot of tweaking. I believe the pro version (and this free one?) export to autodesk which can export into EMS but its a pain in the ■■■■ to do final touchups in EMS from an export.

Have you thought about getting 2 Quadrapods and connecting them together somehow? Or do you want the legs to be in a circle? (Sorry, I didn’t read the whole topic)

#16

I’ve been going through the same process and it has not been pretty until I found Sketchup. I believe Google Sketchup will do what I need to do also, from what I see on the SKetchup website.

I don’t need to be that exact with my sketches. I just need to be able to provide a visual of what I want done. :smiley:

Sketchup Pro can export to .dwg and .dxf, so I am hoping Google Sketchup can also.

Yes, I have though about the two quad sections to make up an Octapod, and I can do it using 100% SES parts. :smiley: I’d use two hexagon tubing connectors and put 4 legs on it - two off each side. Then I would connect the two sections with a length of tubing. I would add a length of tubing and brackets to each section for leg mounts. I’d use long “C” brackets for the front leggs of the front section and back legs of the back section and offset brackets for the middle lefts so they would come out straight from the body.

I want the front and back legs coming out straight from the body, which makes them come out angled so they don’t interfere with the middle legs.

I have also figured out how to attache a wheeled base underneath the Octapod body and have almost got a design for automatically switching from wheeled to walking that can be done under autonomous control. :smiley:

Now that I have Sketchup, Here is the drawing of the long Octapod base I can build 100% with SES parts.

http://www.thedynaplex.org/robotics/img/long_octapod_base.jpg

#17

WOW, that is so well thought out! I hope Jim takes it into consideration of actaully making it an SES kit and maybe name it after you?? hehe :smiley:

#18

Many thanks. :slight_smile: I’ve been kicking this idea around for about 3 months to get this far and I am finally ready to start aquiring parts and building. :smiley: I just need to get the parts a bit at a time, but I will get it all done in time. I am ordering the first parts tomorrow.

Now, THAT would sure be motivation for me to build the long Octapod… :smiley:

#19

This looks like fun.

It sounds like you will mount the powered wheels to the chassis rather than putting them on the legs themselves.

What if you put two powered wheels on two of the legs (Rear) and two freewheeling wheels on two on the other segment (Front) The steering could then be accomplished by the positioning of the legs and it could walk and drive simultainously.

:slight_smile:

#20

Yes, this is how I will be doing it for my first Octapod. It’s easier for me to start out this way and I want something I can play with as soon as possible. It will take a lot longer for me to get all the legs built.

This is certainly an interesting variation, and I am planning to put something addional on at least the two front legs - just not wheels at this time although my desired mounting scheme should allow me to change what I put there easily enough. :smiley: I am designing for flexibility as well as function. In any case, all wheels will be independently driven and steerable.

I am designing the robot’s legs such that I can add stuff on the knees and ankes. :smiley: