Reading Notes

Scott L. Delp, Frank C. Anderson, Allison S. Arnold, Peter Loan, Ayman Habib, Chand T. John, Eran Guendelman, and Darryl G. Thelen. OpenSim: Open-Source Software to Create and Analyze Dynamic Simulations of Movement. IEEE Trans. on Biomedical Engineering, Vol. 54, No. 11, November 2007.

http://nmbl.stanford.edu/publications/pdf/Delp2007.pdf

Summary

Presents OpenSim, an open-source biomechanic simulation software available at https://simtk.org. The paper provides a brief overview of the OpenSim platform but focus more on SimTrack, a plug-in aimed at tracking motion-captured data.

SimTrack works in 4 steps:

1. Scaling. A generic muskuloskeletal model is scaled to fit measured data (global body mass and mocap markers)
2. IK. Inverste kinematic is used to let the scaled model track the mocap data.
3. RRA. A residual reduction algorithm is used to ensure that the modeled masses and the tracked accelerations match the measured ground reaction forces and moments.
4. CMC. Computed muscle control generate muscle activation to produce coordinated muscle-driven simulation of the movement.

A sample case study is given, where a stiff-knee gait is tracked, a chirurgical procedure is simulated in OpenSim, and then compared with results from the actual procedure.

Comments

• I don't understand equation 2, that looks quite simple at first glance. Ran it by Stelian and he finds it quite fishy too.
• The most interesting part, step 4 CMC, is not very precisely described. It is mentioned that a static optimization criterion is used to distribute forces across synergistic muscles.
• Another muscle model is given here, I should investigate.
• I should check the Physiome Project, that outline the challenge of building a human neuromuskuloskeletal model. (See ref 78)
• It is mentioned that Thelen and Anderson were able to drive a 21 DOF, 92 muscles model to track gaits, with simulation times of 30 minutes for a half-cycle (see ref 25).

-- PhilippeBeaudoin - 13 Feb 2009

-- PhilippeBeaudoin - 11 Mar 2009