Overview
Added in OpenSim 4.0, the Output Reporter is a new Analysis tool that allows users to tailor their analysis workflow to their exact needs. In this example, we'll use a results from a previously generated jumping simulation to explore the Output Reporter.
Model and Simulation Background
In this tutorial, you will be using a simplified musculoskeletal model with muscle-driven lower extremities and torque-driven upper extremities. It is modified from the lower-extremity model of Delp et al. [1] to combine major muscles in the lower extremity and to include a torso and arms [2]. The anthropometry of the model has already been scaled to match the dimensions of the subject we will be analyzing.
The simulation was created following an Inverse Problem approach. Specifically, Inverse Kinematics was used to find the joint angles that best reproduce the experimental marker positions of the subject performing a maximum-height jump. The Residual Reduction Algorithm tool was used to adjust the model's torso mass parameters so that the motion from Inverse Kinematics with the model is more dynamically consistent with ground reaction data. Finally, Computed Muscle Control was used to estimate muscle excitation and other muscle and tendon states during the jump.
The files provided are the model, results from Computed Muscle Control, and an example setup file for the Output Reporter.
What are outputs?
Each component type (e.g., Muscle, Frame) has different outputs available for users. Each output is a quantity of interest that a user can query directly from a component for during a simulation.
Exploring outputs of different components
First, we'll find the output for the whole model's center of mass position.
- Load the model file jumper_model_updated.osim.
- In the Navigator pane, select the model by clicking on the model name "jumper". This should bring up the properties of the model in the Properties pane.
- In the Properties pane, click on "Outputs". This Properties pane will now be populated with the outputs that can be extracted from the model. The name of each output appears in the left column, and the data type in the right column.
- To use the Output Reporter, the full path to each output is needed. We'll find the output for the center of mass position of the whole model. Select "com_position" in the Outputs list. In the bottom left, there are now two strings. The top string is the name of the output (i.e., "com_position"), and the line below contains the full path (i.e., "/|com_position")
Next, we'll find the output for the right hand's position.
Finally, we'll find some interesting muscle outputs.
Exploring the Output Reporter analysis tool
References
- Delp, S.L., Loan, J.P., Hoy, M.G., Zajac, F.E., Topp E.L., Rosen, J.M. An interactive graphics-based model of the lower extremity to study orthopaedic surgical procedures. IEEE Transactions on Biomedical Engineering, vol. 37, pp. 757-767, 1990.
- Hamner, S.R., Seth, A., Steele, K.M., Delp, S.L.A rolling constraint reproduces ground reaction forces and moments in dynamic simulations of walking, running, and crouch gait. Journal of biomechanics, vol. 46, pp. 1772-1776, 2013.