How to Use the RRA Tool

The topics covered in this section include:

How to Use the GUI

The computed muscle control tool is accessed by selecting Tools → Reduce Residuals … from the OpenSim menu. The RRA Tool is governed by three tabs: 

	The Main Settings pane is used to specify the input kinematics, tracking tasks, and control constraints as well as the time range for the analysis, and the output of the results. The External Loads pane is used to specify parameters relating to the external loads applied to the model during the analysis. The Integrator Settings pane is described more in Settings Files and XML Tag Definitions.

Figure: Window for the RRA Tool. The residual reduction tool window has three panes. The Main Settings pane is shown here; there are other tabs for describing additional actuators (residual and reserve) to be used and integrator settings for forward dynamics simulation (as described for in How to Use the Forward Dynamics Tool).

Configuring the RRATool

To configure the RRATool, check Adjust model and specify a body to adjust. Specifically, RRA will compute the average residual forces that were necessary for tracking and use these values to change the center of mass location of the body specified and recommend mass adjustments. Secondly, kinematics are tracked (according to the task weightings) and experimental accelerations are not imposed as constraints.

Replacing Model Actuators

Critical to RRA is the replacement of muscles with just one ideal actuator per coordinate. In the gait2354_simbody example, these correspond to residuals for the pelvis' six degrees of freedom and reserves for all other model internal coordinates (joint angles). Under the Actuators and External Loads tab, you would load the gait2354_RRA_Actuators.xml file and select Replace model's force set.

Command-line Execution

RRA uses the command rra -S <setup file name>, for example, 

rra -S subject01_Setup_RRA.xml