Harmonic Drive Joints. Shoulder, elbow, wrist, end effector, vertical lift. $7 servo

The Harmonic Drive [www.thingiverse.com] is an assembly that can multiply the torque of a single chepo metal gear servo and also hold position without using power. I would like to incorporate the components into universal joints for a dual arm robot. basically taking the harmonic drive design and adding the arm structure to the 3d model. Print the arm and joints in parts then drop in the servo and secure to the horn and finish asembly of a nice strong arm to put on a vertical lift also based on the harmonic drive system. Any takers on the design end, I have a printer too.
FA

Edited 1 time(s). Last edit at 01/29/2013 07:09PM by freddya.

Harmonic drive robot

I'm amazed at how functional printed harmonic drives can be, though I'm curious how long they will last. Any chance you could run one of these until failure, possibly with a mechanism to count rotations?

Also what kind of torque can these things hold and how big are you thinking of making an arm?

And if you're making a manipulator or walking robot, you really ought to see if you can't print a torsion spring with a relatively linear response. That way you can make something called a series elastic actuator. Basically you put a torsion spring between your harmonic drive and whatever you're trying to move and measure the deformation of the spring, this way you can get a measure of the torque on your actuator. And if you know actuator torques, there's quite a bit of cool stuff you can do.

In addition, the spring helps isolate the gearbox from any shocks experienced. One can also use the spring to store energy, something that's really useful if you're building a walking robot.

... with the right materials (elasticity/stiffness/friction/wear/surface) for the flexspline and the teeth a harmonic drive can perform myriads of turns!

I've assembled some really small (0.7mm diameter for the planetary gears, 1.9mm diameter for the gear-box) 3-staged HD's made of plastic for Faulhaber, where the micro-motor has more than 100k rpms, that were continuous running for some weeks without remarkable wear.

Have another micro-HD with flexspline, where all parts are LIGA.fabricated from Ni, that has similar lifetime-expectations.

So a lifetime-test could be a really long-lasting job

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Viktor
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