Inputs and Outputs

The inputs for setting up the Analyze Tool consists of (see Analyses):

  1. OpenSim model [.osim file] (same as input to CMC)
  2. External loads [.xml file] applied to the model (same as input to CMC)
  3. Actuator controls [.xml file] output from CMC, used to drive muscles and other actuators
  4. Model states [.sto file] output from CMC, used to define actuator and kinematic state of the model for analysis

The Induced Acceleration Analysis, also requires several additional inputs:

  1. Coordinate names of the coordinate induced accelerations one wishes to obtain. Key word 'all' reports all coordinate accelerations.
  2. Body names of individual bodies whos accelearations one wishes to obtain. Key word 'all' reports all body accelerations. Keyword 'center_of_mass' reports on the induced acceleration of the mass center.
  3. ConstraintSet is a list of Constraints used to replace the ExternalForces in the set of ExternaLoads. The user can specify the constraint type from PointConstraint, WeldConstraint and RollingOnSurfaceConstraint. The Induced Acceleration analysis will replace the ExternalForce with the corresponding Constraint when theforce_threshold is exceeded.
  4. force_threshold is the minimum external force magnitude required for constraints to be considered on. For example if the force threshold is set to 10N, if the ground reaction force is below 10N, no constraint is applied and if the ground reaction force is above 10N the specified constraint (Weld, Point, or RollingOnSurface) is applied.
  5. compute_potentials_only if true provides just the potential (acceleration per unit force) of each contributor. Since a muscle's potential is not dependent on the activation level of the muscle a states file is not required to calculate the potentials. .
  6. report_constraint_reactions if true reports the induced reaction forces for each constraint applied. This option provides the means of comparing the superposition of reaction forces to the experimentally measured reaction forces.

The outputs from an Induced Acceleration Analysis consists of:

  1. The induced accelerations generated by each force contributor (muscles, actuators, gravity and velocity related forces) listed for each coordinate or body of interest listed (above).
  2. Note, if compute_potentials_only is true, then the induced acceleration results correspond to 1N of applied force for any of the muscles and other actuators or 1Nm for residual and reserve torque actuators.
  3. Optionally, if report_constraint_reactions is true, the contribution of each force contributor to the constraint reaction forces and moments are reported on the bodies connected by the constraint (typically the ground and the foot).