DOBJREF

Bulk Data Entry

DOBJREF – Design Objective for Minmax Problems

Description

Defines a response and its reference values for a minmax (maxmin) optimization problem.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
DOBJREF	DOID	RID	SID	NEGREF / LID	POSREF / UID	LOWFQ	HIGHFQ

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
DOBJREF	22	3	ALL	-1.0	1.0
DOBJREF	22	5	ALL	-1.0	1.0

Associated Cards

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
DRESP1	3	TOP	DISP			3		488
DRESP1	5	BOTTOM	DISP			3		601

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
DOBJREF	23	14	ALL	-1.0	1.0

Associated Cards

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
DRESP1	3	TOP	DISP			3		488
DRESP1	5	BOTTOM	DISP			3		601

Field	Contents
DOID	Design objective identification number. (Integer > 0)
RID	DRESP1 or DRESP2 identification number. (Integer > 0)
SID	Subcase identification number - use ALL if it applies to all subcases. Default = ALL (Integer > 0, blank or ALL)
NEGREF/ LID	NEGREF (Real < 0.0) Default = -1	Reference value for a negative response (should always be a negative real number or blank). See comments 2, 3 and 5.
	LID <Integer> No default	Table identification number of a TABLEDi entry that specifies the negative reference as a function of loading frequency. See comments 2, 3 and 5.
POSREF/ UID	POSREF (Real > 0.0) Default = 1.0	Reference value for a positive response (should always be a positive real number or blank). See comments 2, 3 and 5.
	UID <Integer> No default	Table identification number of a TABLEDi entry that specifies the positive reference as a function of loading frequency. See comments 2, 3 and 5.
LOWFQ	Lower bound on a loading frequency range. Default = 0.0 (Real > 0.0)
HIGHFQ	Upper bound on a loading frequency range. Default = 1.0E+20 (Real > LOWFQ)

Comments

1.	The same DOID can be used for multiple DOBJREF entries. If only one DOID is used, only one MINMAX=DOID entry is needed in the Subcase Information section.

2.	The use of reference values allows users to set up general minmax problems involving different responses with different magnitudes. For these problems, the objective can be defined as:

Or, alternatively:

Where, Wk are response values, and rk are corresponding reference values, which can take different values depending on whether the response is positive or negative.

Typically, the target value or constraint value of a response can be used as its reference value. So, instead of the traditional optimization problem where there is a single objective and multiple constraints, the problem may be formulated as a minmax (maxmin) optimization, where all the responses which were previously constrained are defined as objectives and their bounds are used as reference values. This works toward pushing the maximum ratio of response versus bound value as low as possible, thus increasing the safety of the structure.

LOWFQ and HIGHFQ apply only to response types related to a frequency response subcase (DRESPi, RTYPE = FRDISP, FRVELO, FRACCL, FRSTRS, FRSTRN, FRFORC, FRPRES and FRERP). The reference values NEGREF and POSREF are applied only if the loading frequency falls between LOWFQ and HIGHFQ. If ATTB of DRESP1 specifies a frequency value, LOWFQ and HIGHFQ are ignored.

5.	LID and UID identify a loading frequency dependent tabular input using TABLEDi. They are applied analogous to LOWFQ, HIGHFQ detailed in comment 4.

6.	The recommended setup to define Minmax or Maxmin models which reference several responses is:

•	Create multiple DOBJREF entries with the same DOID

•	Each DOBJREF entry references one response

•	MINMAX or MAXMIN entry should reference the single ID corresponding to all DOBJREF entries.

7.	This card is represented as a designobjectivereference in HyperMesh.