prescribing muscle activation
Posted: Tue Feb 19, 2013 12:18 pm
Hi all,
I've been running a forward dynamic simulation with constant prescribed activations with four muscles. I used Millard2012EquilibriumMuscle and set the flag "ignore_activation_dynamics" to true, and created a PrescribedController with Constant functions which equaled the initial state activation values. After running 50 ms of simulation time, and plotting the activations I see strange results. I notice that all my muscle activations start at their correct prescribed activation value, but then ramp up to a slightly higher incorrect value, and remain constant thereafter at this incorrect value. I expected a constant activation throughout.
I also performed the following tests:
I changed the recfem muscle to a deprecated Schutte muscle->It DOESN'T show the ramp behavior.
I changed the vasint muscle to a Thelen2003Muscle-> It DOES show the ramp behavior
I changed the "ignore_activation_dynamics" flag of the vaslat muscle to FALSE and gave it very small activation time constants-> It shows a very quick ramping behavior. Then I changed the "ignore_activation_dynamics" flag to TRUE and it showed the exact same behavior. Could someone please explain to me what is happening here?
I've been running a forward dynamic simulation with constant prescribed activations with four muscles. I used Millard2012EquilibriumMuscle and set the flag "ignore_activation_dynamics" to true, and created a PrescribedController with Constant functions which equaled the initial state activation values. After running 50 ms of simulation time, and plotting the activations I see strange results. I notice that all my muscle activations start at their correct prescribed activation value, but then ramp up to a slightly higher incorrect value, and remain constant thereafter at this incorrect value. I expected a constant activation throughout.
I also performed the following tests:
I changed the recfem muscle to a deprecated Schutte muscle->It DOESN'T show the ramp behavior.
I changed the vasint muscle to a Thelen2003Muscle-> It DOES show the ramp behavior
I changed the "ignore_activation_dynamics" flag of the vaslat muscle to FALSE and gave it very small activation time constants-> It shows a very quick ramping behavior. Then I changed the "ignore_activation_dynamics" flag to TRUE and it showed the exact same behavior. Could someone please explain to me what is happening here?