OpenSim Description, Status, and Plans Science Advisor Workshop June 1-2, 2006

1. OpenSimDescription, Status, and PlansScience Advisor WorkshopJune 1-2, 2006 Clay Anderson, Ayman Habib, Pete Loan, and Scott Delp

2. What is OpenSim? Object-Oriented Framework for the Simulation, Control, and Analysis OpenSim, Gait Workflow OpenSim API CVODE, RootSolve, SQP, SA, LAPACK, Simbody Developers: Clay Anderson (Framework) Ayman Habib (Applications) Peter Loan (Musculographics / SIMM) Saryn Goldberg, May Liu, Ilse Jonker, Jen Hicks, Chand John, … … … …

3. Original Plan (Nuclear Bomb)

4. Chief Design Goals • Speed • Shareable code • Extensibility • Different Entry Levels • Algorithms • Modeling API • Scripting • Graphical User Interface Matlab!

5. OpenSim API RKF 5-6 CVODE … Simbody

6. Some Code • Like SIMM Dynamics Pipeline but using C++. • Platform independent • Windows • Mac • Linux • Other Unix flavors • CMake is a cross-platform compile system (www.cmake.org) • Swig is an automated wrapper generation facility • Java

7. Lowering the barrier for developers and users • Examples • Sample code • Templates for extending OpenSim (analyses, actuators, controllers) • Documentation • OpenSim Developer’s Guide • OpenSim API Reference (Doxygen) • Streamlined installation • Training • Workshops directed at solving your problems • Graphical User Interface (GUI)

8. Making Simulation Accessible- OpenSim GUI Animation Playback Data, Model,and SimulationNavigator 3D Visualization using VTK Plotting Simulation Progress Command and Scripting Window

9. Investigations and Workflows • Investigation- equivalent to something you’d normally write in a main routine • Optimization study • Inverse dynamics study • Workflow- a set of investigations • Gait Workflow • Subject-specific Simulation Workflow

10. Step -1 Preprocess Experimental Data Gait Workflow

11. Execution of the Gait Workflow currently % scale –Setup 900045_setup_scale.xml (seconds) % ik –Setup 900045_setup_ik.xml (minute) % rra –Setup 900045_setup_rra.xml (10 minutes) % cmc –Setup 900045_setup_cmc.xml (10 minutes) % perturb –Setup 900045_setup_perturb.xml (hours) Should we develop facilities for executing workflows in a GUI? • Main OpenSim GUI • Stand-alone wizard

12. April 2006 OpenSim 0.5 (alpha) June 2006 OpenSim 0.6 (alpha) Use of OpenSim name space Consistency in class names and file storage Dependent on SIMM and SDFast Sept 2006 OpenSim 0.7 (alpha) API supports SIMM modeling features, switching dynamics engines and integrators SIMM muscles native GUI for visualizing models with muscles Wizard for executing the gait workflow Dec 2006 OpenSim 0.8 (alpha) Simbody and CVODE available in OpenSim 80% of SIMM modeling features in GUI No more dependence on SIMM / SDFast documenting and testing Mar 2007 OpenSim 0.9 (beta) Streamlined installation documenting and broader testing June 2007 OpenSim 1.0 80% SIMM functionality Simbody, CVODE Gait Workflow Documentation Examples and pre-made simulations Materials for a short course August 2007 Dissemination Event Tutorials adjunct to ASBAnnual Meeting Preliminary Release Schedule

13. Some Questions… • Do we need additional concepts in OpenSim? • sensors, contact, … • How important is interfacing with Matlab? • What SIMM features are priorities? • What new things would be most compelling to you? • control, dynamic optimization, speed, … • When should we engage users? Who? • Are we being too ambitious? • Are there some simple wins, killer apps? • What should we be thinking about beyond the next year? • “Directed Reductionism” and Sherm’s Modeling Layer

14. Acknowledgements Supported by the National Institutes of Health through the NIH Roadmap for Medical Research Grant U54 GM072970. NIH HD45109, HD38962, HD33929

15. Why use OpenSim? • Many of the capabilities of SIMM • Choice of dynamics engines • SD/Fast (proven, but costs and requires compile step) • Simbody (free, no compile step, everything but loop joints) • Choice of integrators • RKF, CVODE, … • Pipeline for creating simulations from MoCap • CMC, … • Analyses • Extensible (plugins) • New actuators, controllers, analyses, …

16. Clinical Importance • Movement disorders are a challenging problem. • The causes are not well understood. • Muscles are the targets of treatments. • Treatments are often unsuccessful. Asakawa et al. (2004) J Bone Jnt Surg

17. Subject-Specific Simulation 1.18 m/s 78 kg, 1.78 m 19 DOF, 92 Muscles (Delp, 1990) 3 dofback 6 dofpelvis 3 dof hips 1 dof knees 1 dof ankles ~1° Tracking Accuracy ~20 min computer time

18. Simulations Generated with CMC Each generated with less than 10 minutes of CPU time.

19. Limitations of CMC • CMC is a tracking algorithm, not well suited for predicting emergent behavior. • Generating a simulation that replicates a subject’s gait cycle. • Solving for the theoretically most-efficient gait cycle. • CMC is dependent on the quality of the input data. • Kinematics • Ground reaction forces

20. Computed Muscle Control Step 1:Compute Desired Accelerations (PD Control) velocityerrors positionerrors

21. Computed Muscle Control Step 2:Solve for Muscle Excitations a) Integrate forward by T (0.010) to compute and . b) Solve static optimization problem to find to achieve . c) Root solve to find the muscle excitations that will generate .

22. Computed Muscle Control Step 3: Integrate from t to t+T

23. Computed Muscle Control Step 1 Step 2 Step 3 Repeat Steps 1, 2, and 3, until the final time is reached.

25. Different Causes Suggest Different Treatments

26. Number of 3D, Muscle-Actuated Simulations of Gait Liu, Jonkers, Arnold, Thelen, Anderson, Delp (92 Muscles) Number Hase et al., Sellers et at. (~60 Muscles) Yamaguchi & Zajac (9 Muscles) Anderson & Pandy (54 Muscles)

27. Perturbation analysis *Hold other active forces constant

28. Comparison of Joint Moments

29. Average Knee Acceleration Extension Phase ext deg/s2flex Knee Extension in Early Swing for 6 Subjects at 4 Speeds All Subjects All Speeds % of total