Re: typical servo speeds

Graham,
You might try hacking apart a hard drive, they have very fast moving
coil drives that move through an angle of about 45°. It is easy to
remove the case to get at the mechanism. The small drives of course
have very small drive mechanisms.

Companies like http://www.h2wtech.com/noncommdcactu.htm make small
voil coil actuators and related equipment, which could be pretty fast.

Hard drive head position feedback is usually through tracks on the
disk, so you'll need to come up with your own. The simplest thing is
probably a LED, a shutter in the moving part, and a silicon
photodetector. The shutter is arranged so that a one end of travel
no light is blocked, at the other end all light is blocked, half way
half the light is block. A silicon photodiode can be found in
several devices, for example a CD player or try digikey.

If you manage to make one of these fly, we'd love to see it!

It is probable that a voice coil drive like the hard drive motor will
not have as high an energy density as an optimized motor with
commutation.

Has anyone on the list opened up a really small hard drive? I've
never had my hands on one that could be dissected.

regards-
Elliot


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham
Stabler" <grezmos@...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@> wrote:
>
> That is encouraging Jon.
>
> > A real hummingbird, I believe, flaps its wings at about 600 Hz
> > (or am I thinking about a bumblebee?)
>
>
> A Bumblebee (I'm currently analyzing microCTscans of a honeybee)

flaps

> at around 200hz, a humming bird depending on the species is in the
> 15-30hz range though I'd have to look it up to be sure. I'm looking
> at building something inspired by an insects flight apparatus but

more

> on the size scale of a humming bird. This rig is to allow PIV and
> such analysis in air (other rigs have been scaled up and done in

oil).

> Its a tall order as the wings describe a figure of 8 and they have
> controllable stroke reversal for control all at 20hz, the reversals

of

> course are at 40hz!
>
> Small flies can go right up to 1000hz
>
> All of the insects are resonant mechanisms meaning that the inertia

is

> accounted for with elastic storage, the muscles need only do useful
> work and overcome losses. They can even tweak the resonance by
> stiffening the thorax, its neat stuff.
>
> Graham
>