View Single Post
Old 11-28-2012, 05:08 PM   #218
Erick Mead
Erick Mead's Avatar
Dojo: Big Green Drum (W. Florida Aikikai)
Location: West Florida
Join Date: Jun 2005
Posts: 2,505
Re: Is aiki a clash of forces?

Mark Murray wrote: View Post
Now, if you can use physics to validate the walk-run cycle or use physics for animated human movement, or use physics in robotics, then you've just earned a nobel prize for doing something other physicists can't explain.
I disagree. Reference the above walk-run cycle above. There is no basic physics involved in that.
Actually -- there is. Humans are a multiple inverted pendulum -- and you stabilize a multiple inverted pendulum by bouncing it vertically from the support at a certain range of frequencies of simple harmonic oscillation (can we spell -- "furitama"?). See here for a triple- pendulum, stably inverted -- stability of this system requires no feedback control whatsoever -- just the pure physics of motion. The stability parameters (frequency range etc.) are given by a diffy-q Mathieu function.

Walking is just moving the pendulum from one support to the other in an alternating series (a second oscillation -- at right angles to the first) -- which now makes it complex harmonic oscillation -- and thus a potentially chaotic system -- in the technical sense.

The existence of this basic oscillatory stability regime and mechanism was demonstrated empirically in 1908, though the dynamics -- even of the simple pendulum -- were not successfully analyzed until the 1950's. Chaos as a fundamental principle arrived in the 1970's, but the chaotic aspects of this kind of stability were only grasped beginning in the 1990's. But I doubt any prizes are being handed out at this point. Although some kinks remain.

Walk/run transition is simply a change of the frequency range of the system's oscillation and which also drives a change in the series structure of the number of alternating supports (a bifurcation point -- in chaos terms), The number series of supports changes from the walk series (1,2,1,2,1, ...), to the jog series (1,1,1,1,1... ) to the run series (1,0,1,0,1, ...) -- but we'll leave those three loops of the resulting chaotic attractor (and their additional lateral sway components - forming a third oscillation) for another day, shall we?

All the neuro-muscular stuff is involved in slewing any disturbance outside the stability range back within the broad limits of the stability regime. All props to the IS/IP crowd for what they work on doing within it -- this is the sandbox of stability that they play in. The physics says so.

The oscillatory component dynamic or (what is missed by those who resist the physics on this point) its physical equivalent in potentials -- formed by poising moments within the body ) -- is the inherent basis for aiki manipulation of stability. The physics AND Ueshiba said so -- and showed so ...the spirit of bees and of the demon snake, the red and the white tidal gems, in-yo ho, and the chinkon-kishin (furitama, funetori, udefuri, tekubi-furi, ibuki kokyu, etc. etc. etc.)

Last edited by Erick Mead : 11-28-2012 at 05:11 PM.


Erick Mead
  Reply With Quote