OpenSim Moco: Musculoskeletal optimal control

Abstract

Musculoskeletal simulations of movement can provide insights needed to help humans regain mobility after injuries and design robots that interact with humans. Here, we introduce OpenSim Moco, a software toolkit for optimizing the motion and control of musculoskeletal models built in the OpenSim modeling and simulation package. Open-Sim Moco uses the direct collocation method, which is often faster and can handle more diverse problems than other methods for musculoskeletal simulation but requires extensive technical expertise to implement. Moco frees researchers from implementing direct collocation themselves, allowing them to focus on their scientific questions. The software can handle the wide range of problems that interest biomechanists, including motion tracking, motion prediction, parameter optimization, model fitting, electromyographydriven simulation, and device design. Moco is the first musculoskeletal direct collocation tool to handle kinematic constraints, which are common in musculoskeletal models. To show Moco's abilities, we first solve for muscle activity that produces an observed walking motion while minimizing muscle excitations and knee joint loading. Then, we predict a squat-to-stand motion and optimize the stiffness of a passive assistive knee device. We designed Moco to be easy to use, customizable, and extensible, thereby accelerating the use of simulations to understand human and animal movement.

Bioptim, a Python framework for Musculoskeletal Optimal Control in Biomechanics

“…Some Opensim models can be translated into but Biorbd does not yet support multiple wrapping objects, non-orthogonal DoFs between bodies, compliant contact force models ([34]) or muscle-tendon equilibrium. As seen in [22], wrapping objects are rare due to the computational cost and required optimization when a line of action is in contact with more than one object, which compromises automatic differentiation. Via-points and pre-processed moment arms [35] (to be expressed as polynomial functions of crossed DoFs) are often preferred.…”

“…In order to promote the use of musculoskeletal optimal control among biomechanics researcher, we identified a strong need for a dedicated tool, as shown by the recently launched OpenSim Moco [22]. The biomechanics community being mainly composed of software users, such a tool should request a flexible user interface written in a widely used high-level and if possible open-source language (e.g.…”

Simulating the effect of glenohumeral capsulorrhaphy on kinematics and muscle function

“…Each capsulorrhaphy model was used in predictive muscle-driven simulations of functional movements (see Table 1 and Videos S1-S3) generated using OpenSim Moco (version 0.3.0) 25 The functional movements replicated experimental tasks measured in the literature. 26,27 The predictive simulations were generated by prescribing a series of task constraints and goals that contributed to an objective function value, with the optimal control problem aiming to minimize this value.…”

Simulating the Impact of Glenohumeral Capsulorrhaphy on Movement Kinematics and Muscle Function in Activities of Daily Living

“…Each capsulorrhaphy model was used in predictive muscle-driven simulations of functional movements (see Table 1 and Online Videos 1, 2 & 3) generated using OpenSim Moco (version 0.3.0) 27 in MATLAB (version 2019b, The Mathworks Inc., Natick, MA, United States). OpenSim Moco provides a framework for solving optimal control problems for musculoskeletal systems using direct collocation.…”