The spring allows you to connect two parts together
within your biomechanical model using a standard damped spring that you can
find described in any physics textbook. The mathematical description for this system is shown in equation 1.
K is the stiffness of the spring. Delta x is the displacement of the spring from its resting length.
B is the damping coefficient, and v is the velocity of the mass. So the spring exerts a force
that is proportional to the amount it is stretched or compressed. The damper produces forces
proportional to how fast the mass is moving. So the faster the block tries to move, the harder
the dashpot pushes back on it to resist that movement.
The spring connects to other body parts using
attachments. It has two properties for the primary and secondary
When you select these properties they display a drop-down list that shows all attachment points in this body for you to
select the one you want. When you have set the two attachment points a colored line is drawn between the two attachment points.
Biomechanical springs can be enabled or disabled. You can set this feature directly using the Enable property. You can also do it by applying an
enabler stimulus to enable and disable the spring for specific periods of time. Another way to control whether a spring is enabled is
by using neural control. The default input into a spring controls whether it is enabled. Any input into a spring above 0 will cause
the setting of the enabled property to be flipped. So if the spring is initially set to be disabled and you have a positive input
go into the spring it will enable it while that positive input is maintained. If Enabled is initially set to true then any input into
the spring will disable the spring while the input is maintained.
For more information on how the spring works please see the
spring page of the mechanical tests section and watch the video tutorial.
This project was supported by: