Calibration Study

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1

Hi there,

I’ve a question on the calibration of the 3E Hill Muscles:
It’s almost clear to me how the calibration in general works but when I try to forecast (understand) ms MuscleForces during InverseAnalysis I’m stumbling: As I understood Lt0 is calibrated by the CalibrationStudy. Considering the Force-Length dependency of Hill Type Muscles (eg. the wiki graph) I’m wondering which value describes the resting position “0”.

Example: I’ve no velocity therefor “no” force-velocity dependency, just relative length change - force dependency. That means, according to the Wiki-Graph, I expect my muscle force to be slightly increasing or decreasing if the relative length change is small and around “0”. But what is the relative length change? Is it Lmt0 compared with Lmt(t=0) or Lt with Lt0? Regarding the graph “Total” (green) it should be Lmt(t) . But for that I couldn’t find any Lm0 values in AnyBody.

I’m a little bit confused … :confused:

Regards,
felix

2

Dear Felix,

First i would like to refer to two tutorial pages describing the calibration, i think these tutorial pages explain your question.

This tutorial deals with the muscle calibration
http://www.anybodytech.com/fileadmin/AnyBody/Docs/Tutorials/chapX_MuscleRecruitment/lesson_calibration.html

This tutorial deals also with the calibration.
http://www.anybodytech.com/fileadmin/AnyBody/Docs/Tutorials/chap5_Muscle_modeling/lesson5.html

Additionally this is what the reference manual says:
Muscle Tendon Length Calibration In this calibration method, the length of the muscle tendons are adjusted so that the muscle’s fiber length coincide with the optimal fiber length for the given position of the system. This method assumes full tensional force, i.e., it includes the maximal strain tendon specified for the muscle.

Usuallly the calibration is done in a given fixed position(it can also be a motion) this will provide the muscle calibration model with an Lmt value. It then assuming full tensional force in the tendon and adjust then tendon so that the maxium strength will be obtained in the provided position.

Please ask again if this does not answer your question.

Best regards
Søren

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