On Tuesday, May 12, 2015 at 5:21:39 PM UTC-7, Ed Huntress wrote:
On Tue, 12 May 2015 15:15:54 -0700 (PDT), Dan
wrote:

On Tuesday, May 12, 2015 at 2:38:02 PM UTC-7, Ed Huntress wrote:
On Tue, 12 May 2015 14:23:38 -0700 (PDT), Dan
wrote:

On Tuesday, May 12, 2015 at 2:02:10 PM UTC-7, Ed Huntress wrote:
On Tue, 12 May 2015 16:51:30 -0400, Tom Gardner
wrote:

On 5/12/2015 12:50 PM, Ed Huntress wrote:
Eyes getting old? Having trouble hitting the ten ring? Are those
running pronghorns just too jumpy for you these days?

DARPA's .50 cal EXACTO bullets may be just what you need. Don't shoot
it and then forget it; just shoot it, and then steer it:

http://tinyurl.com/lkyjp9f



ALL my bullets are steerable...until they leave the tube!

Steerable...but are they steered? g

This is a very weird thing. How thay got that optical communications
and mechanical steering technology into a .50 cal bullet, I can hardly
imagine.

--
Ed Huntress

I was the Guidance and Control Manager for my companies' proposal for the original EXACTO BAA. We lost but it was a lot of fun. It was huge technology risk to make it all work. I still have the Stero-Lithogrphy bullet concept and a actuator control demonstrator on my desk.

There was a press release a year or so ago from Teledyne where they disclosed the steering concept. It used and magnetostictve material (Terfinol) to actuate the rear fins.

Aha! I figured it was either piezoelectric or Terfenol-D. But I worked
on a project at Wasino (now Amada Machine Tools) for turning
elliptical pistons using a Terfenol actuator, and we had to apply a
lot of electronics and programming to overcome the hysteresis. In
fact, that's what eventually killed the project.

--
Ed Huntress

I suspect Telidyne used an on off control and aero surface PWM to get some sort of proportional control.

That sounds reasonable, and would self-correct the hysteresis problem.

IIRC, the material has a response rate of around 10 kHz, or maybe it's
20 kHz. The hysteresis is non-linear; it will respond to a reverse
signal quickly, but to a diminished degree. And the non linearity
itself varies, non-linearly, with the *size* of the signal.

It made for a real programming mess. After the consulting engineers
tried for six months to do it with equations, we built a look-up table
and it worked pretty well. But then the control was too slow.

It was a sticky problem.

--
Ed Huntress

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