1. Clay Anderson, Ayman Habib, Pete Loan, and Scott Delp
OpenSim Description, Status, and Plans Science Advisor Workshop June 1-2, 2006
Clay Anderson, Ayman Habib, Pete Loan, and Scott Delp

2. Object-Oriented Framework for the Simulation, Control, and Analysis
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 (
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 Simulation Navigator
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. Preprocess Experimental Data
Gait Workflow
Step -1
Preprocess Experimental Data

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

12. Preliminary Release Schedule
April OpenSim 0.5 (alpha)
June 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 OpenSim 0.9 (beta)
Streamlined installation
documenting and broader testing
June 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

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 GM
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
3 dof back
6 dof pelvis
3 dof
hips
1 dof
knees
1 dof
ankles
78 kg, 1.78 m
19 DOF, 92 Muscles (Delp, 1990)
~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)
velocity errors
position errors

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