Specifications

152
It looks like the force development is slightly nonlinear. This would make sense because ligament elasticity
is generally nonlinear, but in this case it just shows that the abscissa is not the ligament length but rather
an artificial "time" that is proportional to the joint angle.
In the Chart View you can plot any output data against each other. Let's select instead of time the ligament
length. Click the "Out" button, and the field containing the abscissa becomes white. You can now type
LigStudy.Output.Model.Lig.Pos" in the abscissa field:
That's better. Now the elasticity of the ligament is completely linear over the slack length. Let us take a look
at the definition of the ligament model:
AnyLigamentModelPol LigModel = {
L0 = 1.30; // Slack length
eps1 = 0.2; // Strain where F1 is valid
F1 = 1000; // Force in the ligament at strain eps1
};
As you can see, we have only defined three properties. L0 is the slack length. The ligament is not stretched
until its length goes beyond L0, so its strain is zero at L0. When the ligament is stretched, it also builds up a
force. The rate of force development with stretching can be thought of as the stiffness of the ligament, and