How to determine the value of the parameters?

[Paul Jiang]

I am interested in making a custom model, and I want to know how to determine the value of the parameters?

Code: Select all

</GeometryPath>
					<!--The maximum force this actuator can produce.-->
					<optimal_force>1</optimal_force>
					<!--Maximum isometric force that the fibers can generate-->
					<max_isometric_force>819</max_isometric_force>
					<!--Optimal length of the muscle fibers-->
					<optimal_fiber_length>0.0535</optimal_fiber_length>
					<!--Resting length of the tendon-->
					<tendon_slack_length>0.078</tendon_slack_length>
					<!--Angle between tendon and fibers at optimal fiber length expressed in radians-->
					<pennation_angle_at_optimal>0.13962634</pennation_angle_at_optimal>
					<!--Maximum contraction velocity of the fibers, in optimal fiberlengths/second-->
					<max_contraction_velocity>10</max_contraction_velocity>
					<!--time constant for ramping up muscle activation-->
					<activation_time_constant>0.01</activation_time_constant>
					<!--time constant for ramping down of muscle activation-->
					<deactivation_time_constant>0.04</deactivation_time_constant>
					<!--tendon strain at maximum isometric muscle force-->
					<FmaxTendonStrain>0.033</FmaxTendonStrain>
					<!--passive muscle strain at maximum isometric muscle force-->
					<FmaxMuscleStrain>0.6</FmaxMuscleStrain>
					<!--shape factor for Gaussian active muscle force-length relationship-->
					<KshapeActive>0.5</KshapeActive>
					<!--exponential shape factor for passive force-length relationship-->
					<KshapePassive>4</KshapePassive>
					<!--force-velocity shape factor-->
					<Af>0.3</Af>
					<!--maximum normalized lengthening force-->
					<Flen>1.8</Flen>

[Carmichael Ong]

You can learn more about how the muscle models work on the documentation site here: https://simtk-confluence.stanford.edu:8 ... blications

The papers will provide some info and references for how the default values were chosen and what experiments they may be based on. For customizing the model, this will depend on carefully analyzing the literature around your specific research question and adjusting parameters as needed.