Instructables

Simple 18dof Hexapod, Arduino nano (optionally with pololu maestro)

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hexapod_leg.png
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Hello,
Here is a simple hexapod that can be built by hand very quickly. The mechanical design is not great, but it is very much in the KISS (keep it stupidly simple) style and should be doable in a weekend for builders of novice to medium experience.

I won't be improving this project any time soon, and people seem to visit my blog from pololu, so I thought I'd go ahead and document it as is. I built this for a sophomore mechanical engineering class at MIT. The wires and six legs make it look complicated, but since the legs are just the same thing repeated 6 times, it's simpler than it appears. Additionally, I did not implement remote controls so all the code runs autonomously (zero input, multiple output system).

Again, this is documentation of the exact steps involved in a semi-working project. No theoretical underpinnings for designing your own hexapod are really explained here.

A complete picture set of the build process exists here: 2.007 Hexapod (Spring 2011). The first few pictures on there are from Aluminum Hexalinkagepod, based off of the Parallax boebot hexapod.
A set of blog posts exists here: http://orangenarwhals.blogspot.com/search/label/hexaringapod
I would specifically recommend this post: http://orangenarwhals.blogspot.com/2011/05/dreaming-of-dancing-hexapods-2007.html
A video explaining the design process in 7 minutes (this instructables goes into the construction but not the design): http://youtu.be/qTh-OGA_LeM 
and here is a video of it at the end:


Required items (hardware):
~ Vertical bandsaw (unless you have a lot of patience with a razor)
~ 1/4'' plastic sheet (any reasonable thickness such that the plastic is fairly rigid is fine. I used 1/4'' ABS)
~ About 6'' of 
~ 18 R/C servos (I recommend standard size, I've seen hexapods with the tiny 9g servos, but I think that it would be hard to cut out the holes for such servos by hand), complete with the "+" shaped servo horns and servo center screws that should come with the kit.
I used 6 Hitec-311 and 12 Vigor VS-2 servos because that was what I could scavenge for.
~ Screwdriver
~ 4-40 bolts and locknuts (about 48 of them), or whatever bolts fit through your servo flange holes (the side holes). At least 3/8'' long (enough for the 1/4'' plastic or Al and a locknut to fit on there).
~ Drill and drill bit, ideally also a drill press
~ Ratchet or socket wrench for 4-40 bolts
~ Ideally, a vice or clamp
~ Ideally, a horizontal bandsaw
~Optional: Scrap 2x4 wood
~ Measuring instrument, ruler or vastly preferably calipers
~ Optional: Deburring tool


Required items (electronics): 
~ Arduino nano + breadboard + male headers (for the servos)
~ Either 6 Y-splitter servo cables or a pololu serial servo controller (because the default arduino library only supports 12 servos). I bought an 24ch one, but obviously didn't need all 24 ch, not sure why I did that. >.<;; but I am a conservative person and tend to make large purchases just in case. I'm working on fixing this.
I guess another option is to use an arduino mega.
~ Laptop and usb programming cable appropriate for your flavor of arduino
Male Headers
~ Jumper wires (or single core wire
 suitable for breadboards)
~ Potentially some servo extension cables, female-to-female (and you stick headers in them to make them female-to-male) will come in handy.
~ Breadboard (probably a standard 700 point one is best if you are putting the nano onto the breadboard)
~ Battery pack (I recommend a rechargeable battery flavor of battery pack, as the 18 servos are power hungry)
~~ so you could use a 4xAA battery pack and it'd be fine (the servos are nominally 5V servos but they will run fine at 6v, they will just be a bit twitchy because their circuitry/feedback+controls are designed for 5v use), but if they were alkaline batteries (~3000mAh) they would run out after an hour or less of use

~~alternatively, use a LM7805 chip to regulate a lipo battery pack, which runs at 7.4v, down to 5V. These linear power regulators dissipate the extra energy as heat. For how to use one, please google "7805 tutorial". For instance, see: http://jumptuck.com/2011/11/15/voltage-regulation-friend-7805/.


Time required: 1 weekend if you just follow my design. I encourage you to design your own hexapod though, once you see how easy it is!


What I used also included a 2.007 (that's a course at MIT) carrier board (looks like https://sites.google.com/site/2007arduino/). This just brings the servo pins out for easy access, as well as has a built in breadboard and a switching power regulator* that can supply up to 3A at 5v, which is probably enough for the 18 servos. It seemed to function a-okay, but my code only ever had 6 servos moving at any given time.

I also made my own battery pack out of some Sanyo UR18650U batteries that were donated to MITERS by Tesla. They are 3.6V, so I made a 2-series, 3 parallel battery pack for a 7.2V 3.3Ah battery pack. This is obviously overkill. At 3.3 Ah and continuously drawing 3A, I could run my hexapod for over an hour. I've found that 10-20 minutes is plenty of runtime for hexapod.

*as opposed to a LM7805 linear power regulator, a switching power regulator is much more efficient.

Note:The hexapod CAD files are for Solidworks 2012 and do not detail nuts and bolts, they are for reference only. I also made a diameter versus radius error on the body, so the body is too big. 

==
Submitted by MITERS for the Instructables Sponsorship Program.
 
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Creagon1 year ago
Yea I was thinking of the CAD aright thank you!
srhnz Creagon3 months ago

I know...8 months down the track is a long time to make a comment..but:

Sketchup with the Sketchy Physics plugin is a cheap, and highly effective 3d modelling combo for doing this sort of thing. You can add servos, hinges, motors, etc to models, then animate them with the slider controls (these show up when you select the animation icon, which is part of the plugin) Great for checking clearances, and concepts, and (as I have done) exporting to STL for printing.

I've also been recently experimenting with a "bender" plugin combined with a helix drawing plugin to make printable nut & bolt models that work like the real thing. Purely for demo purposes since there's not a lot of tensile strength in them, but nonetheless, a good conversation starter.

Creagon1 year ago
In picture #2 you have an animation of the robots leg, wht did you use for that, I'd like to design my robots on a computer before I start to build them
orangenarwhals (author)  Creagon1 year ago
Hello,
I think of animations as in moving pictures so I am a bit confused. If you mean the computer model of a hexapod leg, that is in a CAD (computer aided design) program called solidworks. If you are an university student you can get solidworks or inventor trials. If not, I suggest you look at google sketchup. Good luck!
Creagon1 year ago
What software did you use to simulate that on a computer?
orangenarwhals (author)  Creagon1 year ago
Hi! Not sure what you mean by simulate -- I CAD'd it in Solidworks, programmed it in arduino, and that was it software-wise. It's not a very intelligent robot.
mmwrz1 year ago
Can u plz tell me the minimum materials required for this project?? I'm in 9th standard and I've a science fair after 1 week... Plz help me out of this.. :( OR suggest me any other project based on technology without arduino parts...plz help..
orangenarwhals (author)  mmwrz1 year ago
Hello,
There is a full list of materials on the initial step of this instructables.
I would suggest browsing instructables, your comment is too vague for me to suggest anything in particular that you could adapt on.
Good luck!
mmwrz1 year ago
Hey.. I'm from India and m not getting the arduino nano...what can I use instead of that??
orangenarwhals (author)  mmwrz1 year ago
you can use an arduino mega or any arduino, or in fact any other microcontroller as long as it has at least 12 digital outputs. good luck!
I know! You can control a whole army with a single controller if you wish! Their invented is quite an interesting individual.
And I have not built much. Just line followers and the like. I'm learning though
A fellow robotics enthusiast! But you obviously outclass me. What is "pololu?" And if you love hexapod robots/systems, you should look up "The Attacknids!" Fun ible too
orangenarwhals (author)  HelmutHound1 year ago
pololu sells a serial servo controller. hexapods! can't believe I hadn't heard of the attacknids before. what do you build?
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