Reference: FrequencyInput

Model ElementA Reference_FrequencyInput defines the input to the frequency response analysis.


The frequency response analysis calculates the response of the system to steady-state oscillatory excitation. The frequency input is characterized by magnitude and phase_angle. You can specify the frequency input on any marker based on forces, displacements, velocity, and acceleration.


   id          = "integer"
   amplitude   = "real"
   phase_angle = "real"
   type        = { "FORCE" | "DISPLACEMENT" | "VELOCITY" | "ACCELERATION" }
   marker_id   = "integer"
   dof         = "integer"
   rm          = "integer"


Element identification number (integer>0). This number is unique among all Reference_FrequencyInput elements.
Amplitude of the sinusoidal input.
Phase angle of the sinusoidal input.
Specify the type of frequency input from Force, Displacement, Velocity, or Acceleration.
Specify the Reference_Marker at which the frequency excitation is to be applied.
Specify the direction of excitation 1-6 for x,y,z, b1, b2, and b3. Multiple direction combinations are allowed.
Specify the Reference_Marker whose coordinate system is used as the basis for defining the components of the frequency input.
This attribute is optional.
When not specified, it defaults to the ground coordinate system.


Consider a quarter car suspension. Assume that you interested in the frequency response of a vehicle body with respect to the frequency input at the wheel hub in the x, y, z directions, with a amplitude of 1 and a phase_angle of 0.
     id = "1"
     amplitude = "1"
     type = "DISPLACEMENT"
     marker_id = "30102010"
     dof = "123"


  1. The frequency input should have a path or degrees of freedom in the direction specified to calculate the frequency response, or else the frequency response leads to a singular configuration.
  2. All output requests of type Marker_Displacement, Marker_Velocity, Marker_Acceleration and Marker_Force are the output for the frequency response analysis.