Global Search Option

The global search option is incorporated directly in OptiStruct. It does not require an external program to run with OptiStruct.

It is activated by the DGLOBAL Bulk Data and I/O Options Entries.

The DGLOBAL Bulk Data Entry consists of many parameters that can be tweaked to maximize the probability of finding the global optimum. The Global Search Option can be run with the default options (see example below) initially to check optimization results, and further adjustments using the various parameters can be carried out depending on the specific model.
DGLOBAL = 10
...
BEGIN BULK
...
DGLOBAL 10

Engine Mount Optimization Example

This example demonstrates the usage of the Global Search Option to optimize engine mount locations in a full vehicle model for a simple rough road shake input.
PARAM, MASSPROP
DGLOBAL = 10
SENSITIVITY = ALL
SENSOUT = FL 
$
INCLUDE '/ANALYSIS/H3D_FILES.dat'
TITLE = ENGINE MOUNT LOCATION OPTIMIZATION
$  ENGINE MOUNT LOCATIONS
SET  400  =  6966 6967 6968 6998 6999 7000
DESVAR = 400
DESOBJ = 1
RANDOM =      2400
SET 2 =1006001,9006002 
   ACCE(SORT1,PHASE,PLOT,PSDF) = 2
SUBCASE 10  $RIGHT SIDE INPUT
   DLOAD=10
   ANALYSIS = MFREQ
   FREQUENCY = 100
   SPC =   1
   MPC =   400
   METHOD = 1
SUBCASE 20  $LEFT SIDE INPUT
   DLOAD=20
   FREQUENCY = 100
   ANALYSIS = MFREQ
   SPC =   1
   MPC =   400
   METHOD = 1
$
OUTPUT(XYPLOT)
XYPUNCH ACCE PSDF / 1006001(T1)
XYPUNCH ACCE PSDF / 1006001(T2)
XYPUNCH ACCE PSDF / 1006001(T3)
XYPUNCH ACCE PSDF / 9006002(T1)
XYPUNCH ACCE PSDF / 9006002(T2)
XYPUNCH ACCE PSDF / 9006002(T3)
BEGIN BULK
$-------------------------------------------------------------------------------
$  PARAM CARDS FOR ANALYSIS
PARAM   WTMASS  1.
$==01==><==02==><==03==><==04==><==05==><==06==><==07==><==08==><==09==><==10==>
$
FREQ1   1       1.0     0.2     95
EIGRL   1               45.0 
$
$-------------------------------------------------------------------------------
$==01==><==02==><==03==><==04==><==05==><==06==><==07==><==08==><==09==><==10==>
DOPTPRM   DESMAX      50
DGLOBAL 10
$-------------------------------------------------------------------------------
$==01==><==02==><==03==><==04==><==05==><==06==><==07==><==08==><==09==><==10==>
$
$-----------------------------------------------------------------------$
$ Left Engine Mount Point of Action
$
GRID        4500          1250.0  -325.0   747.0 
GRID        4505          1250.0  -325.0   747.0 
GRID        4501          1260.0  -325.0   747.0        123456
GRID        4503          1250.0  -325.0   757.0        123456
CBUSH       5955    5964    4505    4500                            5901
CORD1R      5901    4500    4503    4501
$--1---|---2---|---3---|---4---|---5---|---6---|---7---|---8---|---9---|-------|
RBE2        5961 4004501  123456    4500
RBE2        5962 6004501  123456    4505
CONM2       5956 6004501       00.0035  0.0     0.0     0.0 
CONM2       5957 4004501       00.0035  0.0     0.0     0.0 
DESVAR      6966 EM4501X    10.0  -70.00   80.00    0.2
DVGRID      6966    4505             1.0     1.0    0.0     0.0
DVGRID      6966    4500             1.0     1.0    0.0     0.0
DESVAR      6967 EM4501Y    10.0  -60.00   30.00    0.2
DVGRID      6967    4505             1.0     0.0    1.0     0.0
DVGRID      6967    4500             1.0     0.0    1.0     0.0
DESVAR      6968 EM4501Z    10.0  -90.00   70.00    0.2
DVGRID      6968    4505             1.0     0.0    0.0     1.0 
DVGRID      6968    4500             1.0     0.0    0.0     1.0 
$--1---|---2---|---3---|---4---|---5---|---6---|---7---|---8---|---9---|-------|
PLOTEL      5977 6004501    4501 
PLOTEL      5979 6004501    4503 
$  
PBUSH       5964       K   450.0   300.0   500.0     0.0     0.0     0.0
                       B     0.0     0.0     0.0     0.0     0.0     0.0
                      GE   0.040   0.040   0.040     0.0     0.0     0.0
$-----------------------------------------------------------------------$
$ Right Engine Mount Point of Action
$
$
GRID        4510          1250.0   325.0   747.0 
GRID        4515          1250.0   325.0   747.0 
GRID        4511          1260.0   325.0   747.0        123456
GRID        4517          1250.0   325.0   757.0        123456
CBUSH       5964    5964    4515    4510                            6001
CORD1R      6001    4510    4517    4511              
$--1---|---2---|---3---|---4---|---5---|---6---|---7---|---8---|---9---|-------|
RBE2        5994 4004511  123456    4510
RBE2        5995 6004511  123456    4515
CONM2       5996 6004511       00.0035  0.0     0.0     0.0
CONM2       5997 4004511       00.0035  0.0     0.0     0.0
DESVAR      6998 EM4511X    10.0  -75.00   80.00     0.2
DVGRID      5998    4515             1.0     1.0     0.0     0.0
DVGRID      5998    4510             1.0     1.0     0.0     0.0
DESVAR      6999 EM4511Y    10.0  -20.00   80.00     0.2
DVGRID      6999    4515             1.0     0.0     1.0     0.0
DVGRID      6999    4510             1.0     0.0     1.0     0.0
DESVAR      7000 EM4511Z    10.0  -65.00   60.00     0.2
DVGRID      7000    4515             1.0     0.0     0.0     1.0
DVGRID      7000    4510             1.0     0.0     0.0     1.0
$--1---|---2---|---3---|---4---|---5---|---6---|---7---|---8---|---9---|-------|
PLOTEL      6011 6004511    4511 
PLOTEL      6013 6004511    4517                   
PLOTEL     24511 6004511 4004511
INCLUDE '/ANALYSIS/OPTIMIZATION_CARDS.dat' 
INCLUDE '/ANALYSIS/SIMPLE_ROAD_INPUT.dat'
INCLUDE '/ANALYSIS/CONNECTIONS_WO_ENGING_MOUNTS.dat' 
INCLUDE '/ANALYSIS/NON_H3D_FILES.dat'
ENDDATA

In this model, the left and right mount locations are being optimized for improving the driver's seat track for a simple rough road shake input. A majority of the component files are in the CMS super element format. The simple component files are in OptiStruct. The super elements are required in order to make each optimization run faster.

This run will consist of several optimization runs from different starting points. Each optimization output will be added into a separate directory. The .pch files from each directory can be viewed in HyperGraph and the best results can be chosen.

The resulting .grid file for the best results can be included in the basic model file by the ASSIGN,UPDATE card. This will automatically update the engine mount locations for you.