Meeting Abstract
Opensim is a free open-source software package that was developed to enable users to ‘build, exchange, and analyze computer models of the musculoskeletal system and dynamics simulations of movement.” Traditionally, most OpenSim models are very complex with 10-60 actuators and dozens of degrees of freedom. These models can take many years to develop and validate, making the approach less than ideal for comparative work where research often spans multiple taxa. But, OpenSim models do not need to be complex. Simple models can be built via Matlab scripts that would allow comparative biomechanists to harness the physics engine behind OpenSim to address broader biomechanical questions and take advantage of the thousands of brain-hours already invested in streamlining this process. In order to illustrate the method, strengths and limitations of using OpenSim, here I present three examples of models built to replicate or extend published comparative computational work. The first is a power amplified system consisting of a latch, motor, spring and a projectile intended to demonstrate how forward dynamic simulations of simple mechanical models can be constructed, modified and analyzed in OpenSim. Second, 2D frog model is presented to show how experimentally collected marker data can be used to scale a generic model to a species or individual’s morphology and compute joint kinematics or, with force data, moments. Lastly, I present a 21 degree of freedom lower-limb model of a guinea fowl with 47 hill-type muscles to illustrate how OpenSim can be used to predict motor control patterns that would generate a prescribed motion. OpenSim is a powerful tool, in part, because of its community of sharing. Models and data are expected to be made freely available and are readily modified, allowing research to more easily build on the efforts of others.
