Musculoskeletal Modeling

filercaliforniaΜηχανική

14 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

59 εμφανίσεις

Musculoskeletal Modeling

Colin Smith


A method for Studying Movemen
t


Things we can measure in movement:


Kinematics (using motion capture)


Output Forces (Using Force Plates)


Muscle Activation Timing (EMG)



What about in vivo? We need a model


Muscle Forces


Bone contact forces


Musculoskeletal Models


Approach the body like a Machine


Model Bones as Rigid Bodies


Model Muscles as actuators

Inverse Kinematics


Collect Motion Data


Scale Model to match subject


Use least squares method to match position of
markers to model segments


We now know



the kinematics


of each body



segment

Inverse Kinetics


Solving the Equations of motion for each
segment, we can find the forces and moments
between each segment

Muscle Forces


If we know the moments at a joint, we can
find the muscle forces needed to create that
moment


Distribution Problem


Multiple Muscles cross each joint


Bi
-
articular Muscles


Ligaments


Bone
-
Bone Contact


Set up optimization problem


Solve to get Muscle forces

Forward Dynamic Model


Give muscle excitations


Find kinematics, resultant forces


How do we model muscle forces?


Hill Muscle Model

F = Muscle Force

F
0

= Max Isometric Force

v = Contraction Velocity

a =
Coefficent

of Shortening Heat

b

= a* v
0
/F
0


v
0

= Max velocity (F=0)

What can we do with a
Musculoskeletal Model?


Simulate Surgeries


Diagnose causes of atypical gait


Study Neuromuscular Coordination


Analyze Athletic Movements


Compute Internal Forces


Wear on Knee Replacements

Software Demo

How do we know the model is correct?


Must Validate!


Use Inverse Model to compute muscle activations


Compare against EMG data



Measure something in vivo


Bone contact force


The
eTibia

A parameter study


What are the most important parameters to measure in a Subject Specific
Model


Muscle Properties


Length


Cross sectional area


Pennation

Angle


Origin and Insertion locations


Tendon Slack Length


Bone Properties


Dimensions


Joint kinematics


Segment Properties


Mass


Inertia


Joint constraints


Error in Marker Locations?

The Coolest Models

The End


Download Open
Sim
:


www.simtk.org