How to deceide Foor-floor contact parameters

[shoko horibata]

Hi,
I used EFM to provide 'model's' ground reaction forces.
I would like to change some excitation(for example, weak muscle walking) and make new motion patters.
Therefore I want to run FWD but IAA.

I modeled foot as simplified EFM model(Fig.1).

Fig.1

Using it, I run FWD with normal muscle excitation without experimental GRF.
Force reporter reports these foot-floor contact forces(Fig.2).

Fig.2

But the model fall back to ground.

Fig.3

In webinar at OCT 30, 2014(http://opensim.stanford.edu/support/eve ... tml?id=113),
I saw a model it have three square contacts of hunt-crossley.
EFM and hunt-crossley model have 6-7 parameters(stiffness, dissipation, static friction, dynamic friction, viscous friction, transition velocity, (radius)).
It seems difficult to decide adequate parmeters.
So, I have 3 questions:

1. How I decide these value to reproduce correct GRF in FWD?

2. Are there some papers about FWD using EFM or hunt-crossley model to foot-floor contacts?
I have seen papers about RoolingConstarint in IAA, but I haven't seen about FWD using these.

3. Have the problem (how decide adequate parameters in foot-floor contact) still tackled? or finished? or is it not important ?

Please give me any information of this issue.
It would be great if someone give me information or answers.

Sincerely yours,
Shoko horibata

[Xiangjie Meng]

Hi,

Have your problem solved? I have met similar problems. It is pretty difficult to decide right parameter values. Sincerely hope you can give me some suggestions of solving this problems. My emal address is mengxjchina@gmail.com. Really looking forward to your early reply. Thanks a lot.

Jack Meng