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6DOF Robot Arm

Building an open source robot arm for schools and DIYers

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This project was created on 04/28/2014 and last updated 13 days ago.

Description
I want to put robots on the moon to build my base. An industrial arm starts at $10k and go up from there. I figure I can make some money to pay for the space ticket by building and selling the robots myself. I'd like to drive the cost down by making an arm that others can tinker with, improve on, and build community around. I'd like to see two arms assemble a third.

So far I've built a 3DOF arm that I brought to the 2014 San Mateo Maker Faire. I've taught it to write so it can sign pictures and print your message here. I've also built a 5DOF prototype (pictured).

I need all the help I can get. Please share with your friends!

Thanks for reading,
Dan
Details

I don't know what to write here that isn't covered elsewhere.   Ask questions?

You can get the full part list or support me by buying a copy of the current design here:

http://marginallyclever.com/shop/robot-arms/

Components

Project logs
  • New video added

    13 days ago • 0 comments

    1 minutes, 59 seconds!  The trick with filming on a potato is to find one with good eyes so you get a clear picture.  As you can see here, my spud is a little stale.

  • System Diagram added. All requirements met?

    14 days ago • 1 comment

    Can you please tell me if I'm missing a req for stage two?  Please 2x check my work so far.

    I'm really frustrated by the lack of progress in a several areas.  I get stuck in one place, I try another, I get stuck there, I try another, then I have lots of mostly finished things all demanding my time.  I may have to throw money at the problem and figure out how to pay for it later.  Time to call some machinists.

  • There's more than one way to skin a cat ||

    a month ago • 1 comment

    Teaching a robot arm what to do from a keyboard with inverse kinematics is friggin' hard.  The IK has lots of singularities - special cases where things suddenly go stupid.  To avoid this I'm trying to make a 6DOF joystick. 

    It works just like the robot arm but it has no motors.  When I move it around the arduino in the base will pick up the angle values, copy that to the simulation on the screen, and even send it to the robot arm.

    I've already made the sensor blocks.  See picture 1 and picture 2 on instagram.  There's a sensor block under the base, next to the arduino.  I need some 5mm female headers to plug in and someone to help me make the base, the L brackets, and the other mechanical parts.  Anyone want collaborate with me?

    In the mean time I'm printing another 5 blocks.

    I hope this joystick will have other uses, too.  Maybe Kerbal Space Program fans will be able to pull of orbital maneuvers more easily.

View all 20 project logs

Build instructions
  • 1

    Instructions so far:

    http://learn.marginallyclever.com/index.php/Arm3_v1

Discussions

Andrew Becker wrote 3 months ago null point

Hi Dan, sorry for the long delay, I took my family on holiday and decided to leave the hobbies behind. I have already had a good look at your project and it looks great, I would be more than happy to share my work with you, I'm also very curious as to what control system you're using.

Are you sure? [yes] / [no]

Dan Royer wrote 3 months ago null point

The software is home-grown. The electronics are a RUMBA controller - think an Arduino MEGA and a super sized RAMPS board put together.

Are you sure? [yes] / [no]

Andrew Becker wrote 3 months ago null point

So you are doing all of the forward and inverse kinematics from first principles? I've managed to logic out the geometric relationships for my arm because the axis pairs intersect which simplifies the maths. I've then moved all of that into excel to visualise it and plan on using that to implement it in Linux CNC. It works out fairly simple because the alpha, beta and gamma angles fix the position of the 3rd link in space, thereafter it's a matter of working back through each joint position. Because of the geometry I chose there is only one solution to the set of equations and it's not necessary to use matrices to solve. How are you handling it?

I have a Reprap Ormerod and initially I had some trouble with the software. It turned out that the PSU supplied was not supplying a stable voltage to the controller and when the heated bed switched on it would freeze. I went for an industrial PSU with a much higher rated amperage and the problem disappeared. It did however put me off using an arduino based controller considering how easily my first Linux CNC set-up went.

Are you sure? [yes] / [no]

mad.hephaestus wrote 3 months ago 1 point

I had a random thought:
If you take that whole arm section and put it in a 2 axis gambol, centered around the elbow joint (with the elbow being the outside joint), you could get a true R-R-R spherical wrist, without twisting the belts. The entire section you have now would rotate around the center axis. With a circular track around the edge the track race could then form the elbow joint on the out side. You could actuate it with a third counterbalance motor and a gear interface to the outer track.

Are you sure? [yes] / [no]

Dan Royer wrote 3 months ago null point

That's the first thought I had. I've skipped it for now to ... Work my way up? Also as the gimbal turns the wrist motors could collide with the shoulder assembly. I'm looking for a method closer to what existing arms do where the ulna rotation is between the elbow and wrist. I have some drawings and I'm saving them for later.

Are you sure? [yes] / [no]

Dan Royer wrote 3 months ago null point

One of the things that drives my business most is customer feedback. You asked for it and I can do it, so I'll start posting here more. Given how busy I am it will probably be a copy/paste from my website, which may hurt my SEO.

Are you sure? [yes] / [no]

zakqwy wrote 3 months ago null point

Thanks Dan. Great work so far, it's been fun to watch your progress as you develop the 4th and 5th axes.

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zakqwy wrote 3 months ago 1 point

What are your thoughts on putting more info on HaD.io? I'm less likely to click through for project logs or other updates, it's easier to read everything in one place (and comment on it here, too).

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