View Full Version : Non-linear spring mass model

11-20-2006, 12:24 PM
Hello All,

Can someone direct me to any published papers on modeling the restoring
force generated by a human leg during compression?

I wanted to modify my spring mass model (1) so it reflected more closely the
upward restoring force exerted by the leg between foot-strike and mid-stance
while running. The linear spring generates a restoring force that increases
with compression. The leg does not behave this way.

When I used a "hopping" technique (k=m*(2*PI*f)^2) to examine the spring
"constant", k, for different angles of knee flexion, I found that the hopping
frequency, the spring constant and the restoring force decreased the more that
the knee was flexed.

A simple model (2) generates an inverse relation between the force and the
deformation. Has anyone else tried this approach? Any citations would be
greatly appreciated.


Ted Andresen
Math Dept. (SP/G)
St. Petersburg College
St. Petersburg, Florida

(1) _http://members.aol.com/tjacmc/SpringMass.gif_
(2) _http://members.aol.com/tjacmc/KneeModel.gif_