You Move Me (with 6 degrees of freedom)

October 7, 2008 11:13 AM

I’m looking to either buy or build a small motion control platform capable of holding up to about 9lbs, with 6 degrees of freedom. Has anyone out there built anything along these lines, or are there companies that sell devices like this?

As part of the testing at the company I work at, I’m looking into building or buying a motion control platform that can accurately reproduce hand shake in a pre-defined pattern. I’m looking into either building a Sampson platform or buying one. Has anyone either built such a device, or could anyone provide a recommendation for a company that sells such a device?

posted by baggers to Technology (10 answers total)

Best answer: There are multiple axis factory robots all over ebay, which could likely do the job handily, though I'd expect some work once it arrives. Prices vary from under 4k to well over 50k. Even a cheap one of these ought to give you the repeatability you're looking for.
While this:
http://cgi.ebay.com/ABB-IRB6400-M94-ROBOT_W0QQitemZ190255805180QQcmdZViewItem?hash=item190255805180&_trkparms=39%3A1%7C66%3A4%7C65%3A3%7C240%3A1318&_trksid=p3286.c0.m14
May be a bit large though...
posted by asavage at 11:37 AM on October 7, 2008

Response by poster: That would do the job, but it's waaay too big; we just need a simple platform that a prodcut such as a camera or camcorder can be attached to. We are just testing some specific aspects of performance, not blowing stuff up like you do ;-)
posted by baggers at 11:43 AM on October 7, 2008

Response by poster: Adam, didn't mean to sound rude in that reply; a second hand factory robot arm off eBay is a great idea. I am concerned about accuracy, though; we need a good degree of accuracy in small movements, which is why I was considering a latform. Any suggestions on models or types that might be good for that?
posted by baggers at 12:04 PM on October 7, 2008

Best answer: How many axes of independent shaking do you need? In the aerospace industry there are several companies dedicated to shake tables, but they vary a lot in how precise and how versatile they are (if you just want a sinusoidal shake in one axis, that's easy, if you want arbitrary functions with certain transient response in multiple axes, that's hard).
posted by phrontist at 1:57 PM on October 7, 2008

I know nothing about this company, but here is an example of an electrodynamic shake tables specs. They're actually pretty cool... kind of like a giant speaker - many allow you to input an arbitrary signal to drive the displacement coil of the table. We always thought about turning one in to a bass cabinet from hell.
posted by phrontist at 2:05 PM on October 7, 2008

And obviously, you can't get much displacement out of those. An industrial robot may be a better off the shelf option.
posted by phrontist at 2:08 PM on October 7, 2008

Response by poster: Phrontist, I am looking for 3 axis of movement if possible, but we might be able to get by on two. I'm doing some modelling using a 3D accelerometer in the next few days to try and work out the dynamics of the movement.
posted by baggers at 2:27 PM on October 7, 2008

I'm not sure what a Sampson platform is, but when I read the intro to your question the first thing that came to mind was a hexapod positioner or Stewart platform.
posted by Mike1024 at 3:17 PM on October 7, 2008

I also thought you'd be looking for a Stewart platform... lots unstated from your question but a low-rent version of one isn't terribly hard to build (2 plates you can waterjet, some ball joints and linear actuators) -- we had a group of freshmen build one (for a cockpit simulator) in our shop last year. Where it gets hard is in the area you've left unspecified -- what's the max speed and acceleration (ultimately derived from frequency and amplitude) you want, are you okay with overshoot, are you working in a domain where the modes of the mechanical system become important factors, etc... A some point the $5000 systems start looking cheap.

If you can really get by on 2 axes then you might want to look into the DIY CNC mill community; there is a pretty wide array of 2-axis control setups folks have dreamed up (e.g., stolen from plotters, made from scratch out of a pair of stepper motors, and on and on).
posted by range at 5:25 PM on October 7, 2008

Response by poster: Sorry, I meant Stewart platform; got my names mixed up. As to Range's other questions; the aim here is to model hand shake, so we are looking for something that can accurately model the basic parameters of hand shake at several different levels of shake. I'm researching more on that now, so I can't answer your question on speed, acceleration, overshoot, etc.
posted by baggers at 7:15 AM on October 8, 2008