this is quite simply: awesome.

keep up the good work oomlout

Why would you pay to have a laser cut that plastic for you when you could do it yourself at home (the old fashioned way or with a DIY CNC machine of course). Mounting the servos like that rather than using linkages is a pretty inefficient design since each additional servo weighs on all the ones that came before it. A better idea is the old Armatron I think it was called, it had all the motors in the base with linkages going to all the arm joints.

Just a trick to sell you some laser cut at an incredible price
“material and cutting cost about USD$150″

Robotic arms that make extensive use of linkages also run into significant lash problems which leads to poor accuracy. Resolving that requires higher quality parts, and all of a sudden we’re not really in “hobby” territory anymore.

Which is not to say that it’s a bad idea, but I think you dismiss this one too easily.

@xander

We’ve been using one of these from Crustcrawler for a while in a class. Similar in design to the above with the servos in direct drive.

I can tell you that linkages alone do not cause positioning slop. Positional accuracy suffers a lot from gravity at the extremities, even with springs to help with the load. The aluminum frame flexes pretty easily. Not sure how the acrylic would hold up. The servos also are to be blamed for the slop unless you’ve got good feedback (externally) on your position.

@quig

Sure, linkages arent the only cause for slop. But it will tend to make most situations a little worse (accuracy-wise) and can be harder to fix than the other issues. Structural elements can be reinforced, better servos can be used, but only very tight tolerances and high quality bearings can help with linkage slop. Simply put, it’s even an issue in some industrial arms.

Anyway, robots using linkages certainly do have their uses, I was just pointing out that they’re far from being automatically better than the design in this post.

I’ve been messing around with an AL5D from lynxmotion (http://www.lynxmotion.com/Category.aspx?CategoryID=130) for a while. As far as slop is concerned, the main issue is with beam rigidity and weight causing the servos to sag.

The main problems I had with it is the jerkiness of motion. I’m going to use it in a light automation role at my company (gphirrigation.com) for an intermediate step in assembly. The problem is, the parts aren’t welded yet. So if it jerks them around, the parts go all over the place.

I ended up writing a few python modules to calculate servo values from a gripper position (x,y,z) and angle. Then it calculates intermediate positions for a sine wave like motion to that position.

Once I get the thing nailed down, I’ll open source the software. If anyone wants it now, drop me a line at thefekete on google mail.

Anyways, here’s some videos:

http://www.youtube.com/watch?v=82UjezBtZkY
It was about 3:00am, so I was a little spacey for the commentary…

The arm has all digital servos except the gripper and wrist. The shoulder and elbow are 1/4 scale digital robotics servos. All in all I like it alot, and would recommend it to anyone with $600 lying around.