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Simulation Analysis: Estimating Joint Loads

Simulation Analysis: Estimating Joint Loads. Investigating a Simulation:. Velocities. Angles. Moments. Accelerations. EMGs. Forces. Controls. Simulated Movement. Musculotendon Dynamics. Musculoskeletal Geometry. Multibody Dynamics. ∫∫. OpenSim Model. Analysis. Analysis.

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Simulation Analysis: Estimating Joint Loads

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  1. Simulation Analysis: Estimating Joint Loads OpenSim Workshop

  2. Investigating a Simulation: Velocities. Angles Moments Accelerations EMGs Forces Controls Simulated Movement Musculotendon Dynamics Musculoskeletal Geometry Multibody Dynamics ∫∫ OpenSim Model Analysis Analysis Analysis Analysis Fiber/Tendon Lengths Moment Arms Body Kinematics Joint Reactions

  3. The Analyze Tool: Controls Analyze Tool Results Simulation States Model Analysis Analysis Analysis Analysis

  4. Example: Quantifying Joint Loads Design Biomedical Devices Predict Tissue Stress Study degradation Argenson et al, J. Biomech 2005 Besier et al, MED. SCI. SP & EXERCISE, 2006 USC2000, 2009, http://www.flickr.com/photos/usc2000/3189533413/

  5. Joint Reaction Analysis Calculate reaction forces and moments in joints Choose the joint load representation Available from the Analyze Tool

  6. Joint Reaction AnalysisTwo Part discussion Conceptual Overview: Estimating joint forces and moments during gait. Demonstration: Static Optimization and a Joint Reaction Analyses.

  7. Cut apart the joint What loads are transferred across the joint interface? Joint loads constrain the tibia to move on the ellipse.

  8. Estimating Joint Loads Know Model Joint Kinematics External Loads Muscle Forces Fit to measurements Estimate Calculate Joint Reaction Forces and Moments

  9. Static Optimization Input Model Joint Kinematics External Loads Output Muscle Forces Muscle Activations Complete dynamic description

  10. Joint Reaction analysis calculates joint loads in a post processing step. This step traverses all joints in the musculoskeletal model. Sn-2 Sn-1 Sn

  11. Joint Reaction analysis calculates joint loads in a post processing step. This step traverses all joints in the musculoskeletal model. Sn-1

  12. Joint Reaction analysis calculates joint loads in a post processing step. This step traverses all joints in the musculoskeletal model. Sn-2

  13. Si-1 Si Si+1

  14. Joint Reaction Analysis: Setting It Up Inputs from Static Optimization Model Kinematics External Loads data Residual Actuators Inputs specific to JointReaction Muscle force data Joints of interest Bodies of interest Coordinate reference frames Output *_JointReaction_ReactionLoads.sto

  15. Induced acceleration analysis OpenSim Workshop

  16. Induced Acceleration Analysis Equations of motion M: Mass matrix Q: Generalized coordinates G: Gravity V; Coriolis and centrifugal effects S: Generalized force due to contact elements S: Muscle force F: Generalized force (muscle force) R: Force transformation materix (moment arms)

  17. Induced Acceleration Analysis • Stiff 3D linear and torsional springs approximate a weld constraint

  18. Induced Acceleration Analysis • Replaces the contribution of contact • with an appropriate kinematic constraint. • Kinematic constraint reaction forces are • resolved simultaneously with the constrained • equations of motion

  19. Induced Acceleration Analysis Model Contact (Allows relative rotation) Pure rolling constraint on a rolling body in contact with a plane defined on another body (Hamner et al., 2010)

  20. Induced Acceleration Analysis Verify superposition Contribution to com acceleration (Liu, 2006) Kinematic or Bodykinematic Analysis

  21. Induced Acceleration Analysis • How to use IA: • COM vs angular kinematics • Requires Muscle force distribution (e.g. SO) • Does not work in case of missing contact forces (e.g. unilateral forces during double stance)

  22. Example of IAA • Gait2393 model • Run: • Scale • IK • (RRA) • SO • Analysis

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