Open Sim Description Status and Plans Science Advisor

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

What is Open. Sim? Object-Oriented Framework for the Simulation, Control, and Analysis Open. Sim, Gait Workflow Open. Sim API CVODE, Root. Solve, 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, … …

Original Plan (Nuclear Bomb)

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

Open. Sim API RKF 5 -6 CVODE … Simbody

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

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

Making Simulation Accessible- Open. Sim GUI Animation Playback Data, Model, and Simulation Navigator 3 D Visualization using VTK Plotting Simulation Progress Command Scripting Window

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

Gait Workflow Step -1 Preprocess Experimental Data

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 Open. Sim GUI – Stand-alone wizard

Preliminary Release Schedule April 2006 Open. Sim 0. 5 (alpha) documenting and testing June 2006 Open. Sim 0. 6 (alpha) Mar 2007 Open. Sim 0. 9 (beta) • • Use of Open. Sim name space Consistency in class names and file storage Dependent on SIMM and SDFast Sept 2006 Open. Sim 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 Open. Sim 0. 8 (alpha) • • • Simbody and CVODE available in Open. Sim 80% of SIMM modeling features in GUI No more dependence on SIMM / SDFast Streamlined installation documenting and broader testing June 2007 Open. Sim 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

Some Questions… • Do we need additional concepts in Open. Sim? – 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

Acknowledgements Supported by the National Institutes of Health through the NIH Roadmap for Medical Research Grant U 54 GM 072970. NIH HD 45109, HD 38962, HD 33929

Why use Open. Sim? • 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 Mo. Cap – CMC, … • Analyses • Extensible (plugins) – New actuators, controllers, analyses, …

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

Subject-Specific Simulation 1. 18 m/s 3 dof back 3 dof hips 6 dof pelvis 1 dof knees 1 dof ankles 78 kg, 1. 78 m 19 DOF, 92 Muscles (Delp, 1990) ~1° Tracking Accuracy ~20 min computer time

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

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

Computed Muscle Control Step 1: Compute Desired Accelerations (PD Control) velocity errors position errors

Computed Muscle Control Step 2: Solve for Muscle Excitations a) Integrate forward by T (0. 010) to compute b) Solve static optimization problem to find c) Root solve to find the muscle excitations and . to achieve that will generate . .

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

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

Different Causes Suggest Different Treatments

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

Perturbation analysis *Hold other active forces constant

Comparison of Joint Moments

% of total ext deg/s 2 flex Knee Extension in Early Swing for 6 Subjects at 4 Speeds Average Knee Acceleration Extension Phase All Subjects All Speeds