Let's Make Robots!

Rotary Stewart Platform

6DOF movement

All my projects & progress are available at marginallyclever.com.

This is a Stewart platform.  While it is very similar to a delta robot (see my other creations) this one can roll, pitch, and yaw for a full 6 degrees of freedom.  You could put in a pen and draw on an easter egg, add a dremel and carve tiny sculptures, or a nozzle and print 3D shapes impossible on a makerbot.

This particular kind is a rotary platform because the "arms" have an elbow - the shoulder turns, which pushes the elbow, which pushes the wrist.  I have also built a model with linear actuators (no elbow required).

A curious factoid: the mathmatical principles to calculate the angle of the motors are the same used for the spider bot and the delta3.  Convenient!

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It's nice to see some more advanced stuff on here. Keep up the great work and thanks for sharing! 

Have you implemented full inverse kinematics for your enhanced delta robot? (as a arduino library you are going to share...)

The defacto hobby delta robot code here http://forums.trossenrobotics.com/tutorials/introduction-129/delta-robot-kinematics-3276/ is pretty scary, and with your added tilt and rotate things only getting worse.

Anyway, cool idea you got there, going to try that some day too!

As a matter of fact, I have implemented this.  I had not considered releasing it as a library, it would take a lot of overhead to make it generic enough for other people's applications and that overhead would kind of kill the usefulness.  I will, however, post some tutorials on my website giving a human-readable breakdown of the process so that others can do it, too.  I really want to get my kit into schools so that's something I need to practice - making it approachable.

If you want to start on your own, the first thing you need is a Vector(x,y,z) class that you can add, subtract, assign (=), find the length of, scale, normalize, dot, cross, and rotate around another vector.  That is your single most useful tool.  The math everybody else writes is all a.x+b.x*cos(theta) garbage that is hard to read and intimidating.

This is a great project my friend, I love it. Very well done, thanks for sharing :)

It is solid 6061.  There are pockets inside to hold the servos in place.

i'm using DUBRO 4-40 as well.  I made sure the screw/spacer gave as much clearance as possible.  I'd guess I can get 40 degrees.  I'm trying to get someone to quote me on some rare earth magnetic ball joints - they come with M3 tappered holes and support up to 2kg.  The range on those would be awesome!

Why did the delta bot (aka simple version) get 9 comments and this guy sits all alone? The internets are a weird place.

Love the work, design, construction --all clean, no bs, just what they should be. I am a fan so far. However, there are a few things that escape me. First off, the metal work. This can not possibly be 1/2 or 3/4" solid aluminum, could it? I would be quite impressed indeed if it were solid. If it is sheet, I would love to know how it was formed. I am most intrigued (if it is sheet metal) with the edge work, the corner. Was it spun? Was a strip welded to a disc and then finished? --But then I look again and I see that the 6 servos are "sandwiched" between the two plates and think, "no, it has to be solid." Wow. Moving on.

How are you getting that much lateral throw out of your ball links? I have seen this arangement a few times for delta bots and the like, and they all seem to move quite smoothly and with lots of travel. I found myself making a small delta bot to support a robot "head" and used the same fitting but could only squeeze maybe 10 degrees either way. Obviously, the pivot gives me all I want, but the "Z" travel of the ball itself was quite limited. I was using sorta "standard" DuBro hardware --just regular ol' 4-40 ball joints. Are you using a fancy one? Maybe it is the layout of the spacers to each side of the ball. I dunno, I thought I tried everything when I built one, but just couldn't get that much travel.

Gimme what you got.


Oh, wait a sec... I think I just got it... Its not metal, its is MDF painted silver. Maybe. Yes?