Fancy Fly-ing!

Mosquito Haltere (from wikipedia)
Fantastic talk today, by Itai Cohen, from Cornell's Physics department. He's studied the flight of bugs to distraction, and perfection. This ties into a favorite site of mine, sodaplay, which opines that biological movements can be made, can emerge from simple parts.

The fruit fly wing, it turns out, operates with nothing but the main oscillatory flight muscles, a lightly damped (stable) pitching moment coefficient and an adjustable bias for the unloaded incidence angle. Those characteristics make it sweep like a fish's fin: the wing inverts on every back stroke. For me it was reminiscent of helicopter cyclic control.

Even more fun, the prof was able to demonstrate basic lift, propulsion and orientation with his very own home-made man sized fruitfly wings, which he was able (with the studied focus of his enTIRE cerebral cortex) to articulate just as does the bug, thereby spinning himself around on a lazy susan. Here's the fly doing it. I find it interesting that I had a hard time visualizing the motions, too.  There's another way I can do it though, and easily:  think of reorienting yourself while treading water!  If you've spent some time on that, you'll realize you use the same technique, except sculling, meaning you exchange the leading and trailing edges of your hands on the alternate  forward and back-beats of your arms.  Once I realized that difference, it clicked.  I was almost ready to be a fruit fly!  But wait, there's more!

It gets better: vestigial hind wings (called halteres) wobble and somehow are gyros! "And how does the insect use them in the control loop," you ask?  Why, by driving the GYRO with lead integral loop, of course. Then the attitude control, being servoed to null the gyro, just follows along. Why am I the last person to find this out? It is SO old school: AMRAAM, anyone? I remember Dan and Dick Olerich 'splainin this stuff to me back in the day. (Ok, not Dick, this was way below the sort of problem I dared take to the master.) That's still not even the coolest thing!

The coolest thing was that they glued a tiny piece of iron wire to the back of the bug and then zapped it with a magnetic field to knock it off course. It's a form of insect spectrometer.  Way too much fun.

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