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Originally Posted by sciguy125
Speaking of ball drive, I may have just figured out a way to reinvent the wheel. Think of a stepper motor. Instead of a traditional cylindrical rotor, use a spherical one. Like a golf ball with magnets instead of dimples. Now, use two stators that are 90 degrees apart from each other such that you can rotate the sphere about the x axis and about the y-axis. Voila, compact ball drive.
Now if you'll excuse me, I need to find a patent lawyer.
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I've messed around with this idea in order to replicate something I saw in a music video.
A company called Animusic (
www.animusic.com ) makes this sweet midi driven animations... I've always wanted to re-create a scene out of one of the animations... so I'm going for the 3 slightly humanoid looking robots on the "Starship Groove" animation... anyhow back to the story...
The spherical track motor works exactly like a linear track motor except for the fact that the micro-electromagnets are arranged within a sphere made of a non-ferrous material. For my design, this sphere would fit into a matching hemisphere, very slightly larger than the sphere. This, in effect creates a fully functional low-load-bearing ball and socket joint.
OK thats the overview, now heres the problems with it:
There would have to be a processor dedicated to each joint. The design requires at least 3 (4 if it is going to be stable) pulse width modulation channels. It would never be FIRST legal since the victor's update rates are over 26 times too slow for updates. The PWM period would most likely be something like 500ns or so, because of the high instability of intersecting lines of magnetic flux.
The joint itself would have to be encoded for position somehow, perhaps with a hall cell array or something like that. The updates for the servoed position would have to be done every 500ns to keep up with the pulse train, the high update rate is needed to overcome the problems with the intersecting flux lines.
So in a nutshell, here's how it is:
1. Would have to be based on a DSP running around 100MHz for a clock
2. It will eat TONS of current
3. Has to be run at a very very high voltage if you want to get much speed
or load capacity out of it.
4. Will require one UART for positional data input will need 4 channels
of simultaneous high speed PWM, run through a mux chip of some kind
in order to drive the hundreds of micro-electromagnets inside of the
sphere.
5. Will need a super high speed latch chip in order to retrieve data from all
those hall cells.
6. Driver board will have to have a power transistor or mosfet for every
single electromagnet.
7. All parts within about 6 inches of the thing will have to be non ferrous.
8. And oh yeah, the programming will be extremely hard (servoing in 2
dimensions)
Did I lose anyone?
Granted, this is a design which would work for a positional as well as a speed based spherical track motor. But, like I said, my application required positional. It would work for motion purposes as well, though. I'm putting this on my "Things to do before I die" list.
-Q