Prescribing muscle Activations in Forward Dynamics
Posted: Fri Apr 03, 2020 2:57 am
Hello everyone,
I am wanting to directly prescribe activations to my model's muscles so that I can run my simulations without having to allow time for excitation and activation dynamic "time lag".
For the model's muscles to be at the required activation from the start of the simulation and through its duration (i.e. i_muscle_activation=0.3 for Dt=0.05) I am setting the muscles' minimum activation to the value I require with setMinimumActivation(). This works for having the muscles' activation constant throughout the simulation at the value I want as long as the value is >=0.05. If the specified value is <0.05 the activation starts at 0.05 and then begins to drop. Is there a more preferable way of prescribing the muscle activations without applying controls/excitations and going through excitation dynamics in the Forward Tool?
Even though I can directly apply the activations I cannot get around the activation dynamics as the muscle take some time to generate the appropriate force for the state they are in. Ideally I would like the muscles to produce the appropriate force for their given state as soon as I start the simulation.
From what I can understand I could set ignoreActivationDynamics() to true but only in Millard muscle models. My model has Thelen muscle models. Is there a OpenSim function to programatically convert Thelen to Millard muscle models? If not are they any parameters in particular I should focus on when doing it myself?
Thanks in advance!
All the best,
Pavlos
I am wanting to directly prescribe activations to my model's muscles so that I can run my simulations without having to allow time for excitation and activation dynamic "time lag".
For the model's muscles to be at the required activation from the start of the simulation and through its duration (i.e. i_muscle_activation=0.3 for Dt=0.05) I am setting the muscles' minimum activation to the value I require with setMinimumActivation(). This works for having the muscles' activation constant throughout the simulation at the value I want as long as the value is >=0.05. If the specified value is <0.05 the activation starts at 0.05 and then begins to drop. Is there a more preferable way of prescribing the muscle activations without applying controls/excitations and going through excitation dynamics in the Forward Tool?
Even though I can directly apply the activations I cannot get around the activation dynamics as the muscle take some time to generate the appropriate force for the state they are in. Ideally I would like the muscles to produce the appropriate force for their given state as soon as I start the simulation.
From what I can understand I could set ignoreActivationDynamics() to true but only in Millard muscle models. My model has Thelen muscle models. Is there a OpenSim function to programatically convert Thelen to Millard muscle models? If not are they any parameters in particular I should focus on when doing it myself?
Thanks in advance!
All the best,
Pavlos