The topics covered in this section include:

Setup File and XML Tag Definitions

The settings file is an XML file whose tags specify properties to be used by OpenSim for the inverse dynamics analysis. The XML tags used are defined in the following sections.

Note: The following setup file example can be found in examples/Gait2354_Simbody.


Example: XML file for an inverse dynamics setup file

<?xml version="1.0" encoding="UTF-8"?>
<OpenSimDocument Version="20302">
   <InverseDynamicsTool name="subject01_walk1">
      <!--Directory used for writing results.-->
      <results_directory> ResultsInverseDynamics </results_directory>
      <!--Name of the .osim file used to construct a model.-->
      <model_file> subject01_simbody.osim </model_file>
      <!--Time range over which the inverse dynamics problem is solved.-->
      <time_range>       0.40000000       1.60000000 </time_range>
      <!--List of forces by individual or grouping name (e.g. All, actuators,
          muscles, ...) to be excluded when computing model dynamics.-->
      <forces_to_exclude> Muscles </forces_to_exclude>

      <!--XML file (.xml) containing the external loads applied to the model as
          a set of ExternalForce(s).-->
      <external_loads_file> subject01_walk1_grf.xml </external_loads_file>

      <!--The name of the file containing coordinate data. Can be a motion
          (.mot) or a states (.sto) file.-->
      <coordinates_file> subject01_walk1_ik.mot </coordinates_file>

      <!--Low-pass cut-off frequency for filtering the coordinates_file data
          (currently does not apply to states_file or speeds_file). A negative
          value results in no filtering. The default value is -1.0, so no
      <lowpass_cutoff_frequency_for_coordinates>       6.00000000 </lowpass_cutoff_frequency_for_coordinates>

      <!--Name of the storage file (.sto) to which the results should be
      <output_gen_force_file> inverse_dynamics.sto </output_gen_force_file>


Execution Name

The properties for the analyze tool, which is responsible for performing the inverse dynamics analysis, are enclosed inside the opening and closing tags <InverseDynamicsTool> and </ InverseDynamicsTool >. The name attribute name="subject01_walk1" specifies the execution name. The name of the results file generated will be prefixed with this name.


The <model_file> tag specifies the OpenSim .osim file used to construct a model. This file typically defines the OpenSim musculoskeletal model scaled to the dimensions of the subject by the Scale Tool.

Forces to Exclude/Include

The <forces_to_exclude> allows the modification of the forces defined in the model file for the purpose of InverseDynamics. Forces can be specified either individually or as groups, the default behavior is to exclude "Muscles" and leave all other forces (e.g. Bushing forces or contact) in effect.

Results Directory and Precision

The <results_directory> tag specifies the directory where results should be written.

Initial and Final Times

The <time_range> tag specifies the time interval over which the inverse dynamics analysis is to be performed. The initial and final times may be adjusted to the nearest frames of data available.

Coordinates and Filtering

The <coordinates_file> tag specifies the time histories of kinematics (e.g., generalized coordinates) that describe the movement of the model. For example, this file may be generated by the inverse kinematics tool. The <lowpass_cutoff_frequency_for_coordinates> tag specifies the low-pass cutoff frequency for filtering the kinematics. If the kinematics have already been filtered, specify a negative cutoff frequency to prevent filtering.

External Loads

The <external_loads_file> tag specifies the XML file containing the external loads applied to the model during an inverse dynamics analysis. Detailed description of the contents of this file are given above.