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Rene Ferdinands
03-05-2001, 09:35 AM
Dear Biomch-L Subscribers,

Below is a summary of replies to my following request.

Special thanks to Silvia Fantozzi and Philip Requejo who provided me with
the exact reference I was after:

D.W. Risher, L.M. Schutte, C.F. Runge, " The use of inverse dynamics
solutions in direct dynamics simulations",
J Biomechanical Engineering, 1997, Vol.119, pp 417-422



> Hello, I am creating 3D full body models that can simulate human movement
> using both forward and inverse dynamics. I remember reading a reference
> recently - I think it was in the Journal of Biomechanics - where the
> authors stated that there are times when if the resulting forces and
> torques from an inverse solution are fed into the corresponding forward
> solution as the driving functions with the appropriate initial conditions,
> the inverse solution simulation (i.e.inverse solution kinematics) is not
> re-created. I have found this to be true when I use dynamic actuators that
> are non-linear.
>
> I would greatly appreciate it if someone can direct me to the
> aforementioned reference, or other related ones, and also inform me of any
> approaches that can circumvent this problem.
>
> Thank you.
>
> Rene Ferdinands
> University of Waikato
> Dept of Physics & Electronic Engineering
> Private Bag 3105
> Hamilton 2001
> New Zealand
>
> Phone: (+64 7) 838 4026
> Fax: (+64 7) 838 4219
> email: redf1@waikato.ac.nz
> --------------------------------------
>
SUMMARY OF REPLIES
--------------------
rom: "Silvia Fantozzi"
To: "Rene Ferdinands"
Subject: Re: Forward Solution dilemma
Date: Thu, 22 Feb 2001 17:36:59 +0100
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 5.50.4133.2400
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400

I think these papers will help you.
1. E.Y. Chao and K. Rim, "Application of optimization principles in
determining the applied moments in human leg joints during gait",
J Biomechanics, 1973, Vol. 6, pp 497-510.
2. A.D. Kuo, "A least-squares estimation approach to improving the
precision of inverse dynamics computations",
J Biomechanical Engineering, 1998, Vol. 120, pp 148-159.
3. D.W. Risher, L.M. Schutte, C.F. Runge, " The use of inverse dynamics
solutions in direct dynamics simulations",
J Biomechanical Engineering, 1997, Vol.119, pp 417-422

Silvia
__________________________________________________ ___________________________
Rene:

Our SIMM Musculographics would be able to handle such forward dynamics of
orthopedic/biomechanics situations.

Please view our website at:

www.musculographics.com or
www.motionanalysis.com


For more direct answers from Motion Analysis and SIMM, Jiping Shih, VP
Asia/Aust Sales at Jiping.shih@motionanalysis.com can address your specific
questions.
Dan India


Motion Analysis Corporation
Dan India, VP Biomechanics Sales
3617 Westwind Blvd
Santa Rosa, CA 95403 USA

T: 847-945-1411
F: 847-945-1442
M: 847-778-4949

Dan.India@motionanalysis.com
__________________________________________________ _________________________
To: redf1@WAIKATO.AC.NZ
From: philip requejo
Subject: Forward Solution dilemma

Rene,
Here's the ref:
Risher DW, Schutte LM, Runge CF. The use of inverse dynamics solutions in
direct dynamics simulations. Journal of Biomedical Engineering. vol. 119.
1997. 417-422.

Good luck,
Phil
University of Southern California
__________________________________________________ _________________________
To: Rene Ferdinands
Subject: Re: [BIOMCH-L] Forward Solution dilemma

Hello Rene,
was it this paper?

@Article{gruber98,
author = {Gruber, Karin and Ruder, Hanns and Denoth, Jachen and
Schneider, Klaus},
title = {A comparative study of impact dynamics. Wobbling
mass model versus rigid body models},
journal = {Journal of Biomechanics},
year = {1998},
volume = {31},
pages = {439--444}

Regards,
Arnim.
--
__________________________________________________ __________________________
From: "Simon, Dipl. Phys. Jan"
To: "'Rene Ferdinands'"
Subject: AW: [BIOMCH-L] Forward Solution dilemma
Date: Fri, 23 Feb 2001 17:44:10 +0100
X-Mailer: Internet Mail Service (5.5.2650.21)

Dear Rene!

A big problem of simualting human movement are redundant and multi-joint
muscles. They are obviously important, because the evolution likes them. But
inverse dynamics cannot handle them correctly. A second problem are the
joints: Human aren't able to walk with hinge joints in the knee (there are
some surprising tests with people using knee prosthetics: They jump and run
with stabilized 4 axes mechanisms and fall down awkwardly with single axis
hinge joint models). The hinge joint is "unstable", this means that a
straight leg tends to bend, while the flattend levels of real knee joints
lead to a plateau in the potential energy, which straightens a straight
attitude.
When computing the motion these instabilities seem to be the source for the
differences between forward and backward simulation with identical controls.
It's a problem of accuracy of the computer, and, in my opinion, it would be
a general problem for a control mechanism.

This is not the wanted answer, I'm afraid, but I ask some coworkers who are
doing dynamic optimization of human walking for better replies!

Regards from Heidelberg, Jan Simon
Orthopedic dept. of the University, Heidelberg
Interdisciplinary center for Scientific computing IWR, Heidelberg
__________________________________________________ __________________________
Rene Ferdinands
University of Waikato
Dept of Physics & Electronic Engineering
Private Bag 3105
Hamilton 2001
New Zealand

Phone: (+64 7) 838 4026
Fax: (+64 7) 838 4219
email: redf1@waikato.ac.nz
--------------------------------------

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