Maximizing the lowest natural frequency (controller-based optimization)

The natural frequency may be optimized by using the maximization the dynamic frequency response.

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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 has to be set as follows: LC_SET = Modal, All, 2.

    Important: Do NOT define the third argument in the LC_SET command as All (e.g. 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.

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