Maximize a Range of Modes

This section describes how to set up Tosca to maximize multiple modes.

Maximizing a range of modes can be done as follows:


DRESP
 ID_NAME  = dresp_eigs_1-5
 DEF_TYPE = SYSTEM
 TYPE     = DYN_FREQ
 LC_SET   = Modal,All,1-5
END_

OBJ_FUNC
 ID_NAME = max_dresp_eigs_1-5
 DRESP   = dresp_eigs _1-5
 TARGET  = MAX
END_

Here, the 5 first modes are summed in one design response (dresp_eigs_1-5). This sum is being maximized (TARGET=MAX).

This solution often has the pitfall that the higher modes usually are weighted higher than the lower ones. One way to circumvent this is to define a design response for each eigenmode:


DRESP
 ID_NAME  = dresp_eig1
 DEF_TYPE = SYSTEM
 TYPE     = DYN_FREQ
 LC_SET   = Modal,All,1
END_

DRESP
 ID_NAME  = dresp_eig2
 DEF_TYPE = SYSTEM
 TYPE     = DYN_FREQ
 LC_SET   = Modal,All,2
END_

DRESP
 ID_NAME = dresp_eig...
 ...

OBJ_FUNC
 ID_NAME =  max_dresp_eigs_1-5
 DRESP   = dresp_eig1,  0.10 , ! 100. Hz
 DRESP   = dresp_eig2,  0.05, ! 200. Hz
 DRESP   = dresp_eig3,  0.04 , ! 250. Hz
 DRESP   = dresp_eig4,  0.0025 ! 400. Hz
 DRESP   = dresp_eig5,  0.002 ,! 500. Hz
 TARGET  = MAX
END_

Here, each of the five first modes is multiplied by a weight (reciprocal value of the initial eigenvalue) and then summed and maximized.