Maximizing the Lowest Natural Frequency (Controller-Based Optimization)

The natural frequency might be optimized by using the maximization the first natural frequency.

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DRESP
  1. The following shows an example of maximization of the first natural eigenfrequency: 

    
DRESP
  ID_NAME  = dresp_max_eigenfrequency
  DEF_TYPE = SYSTEM
  TYPE     = DYN_FREQ
  LC_SET   = Modal,All,1
END_

OBJ_FUNC
  ID_NAME = maximize_eigenfrequency
  DRESP  = dresp_max_eigenfrequency
  TARGET = MAX
END_

  2. The type of the design response is DYN_FREQ (eigenfrequency). To choose the first eigenfrequency, set the third argument in the item LC_SET to 1.
  3. Reference this design responses ID_NAME in the OBJ_FUNC where it is set to be maximized.
  4. To consider for example the second eigenfrequency, the LC_SET parameter must be set as follows: LC_SET = Modal, All, 2.

    Important: Do NOT define the third argument in the LC_SET command as All (for example, LC_SET = Modal,1,all). The algorithm will then try to combine All modes from the modal analysis, which normally will NOT lead to good results for the controller-based algorithm.

    Consider that the sensitivity-based algorithm (BEAD_SENSITIVITY) is usually superior for this task.