Parameters for the ESLM

Control the maximum number of outer loops executed in the ESLM by using the following parameter:

In this case, the ESLMAX is an integer value, greater than or equal to 0. If the ESLMAX is equal to 0, then optimization process is not activated. The default value for the ESLMAX is 30.

The ESLM has a feature that screens out the time steps that are not dominant during the optimization. In the most cases, this feature is very helpful to improve the efficiency of the ESL optimization process in terms of CPU time. This feature can be activated or deactivated by using:

DOPTPRM, ESLSOPT

The ESLSOPT can be either 0 or 1. If ESLSOPT is 0, the screening is deactivated. If ESLSOPT is 1, this screening is activated. The default value is 1. Unless deactivated by DOPTPRM, ESLSOPT, 0, this feature is always activated.

The time step screening feature is different from the constraint screening of the static response optimization in Step 3, although the concepts of both screening capabilities are similar. The time step screening is performed at time Step 2, which is right before entering the static response optimization phase. By performing the time step screening before entering the static response optimization phase, the huge amounts of CPU time required for structural analysis and subsequent constraint screening strategy can be saved at the 0-th iteration in the static response optimization phase.

Once ESLSOPT is activated, the number of time steps that should be screened out can be controlled by using:

DOPTPRM, ESLSTOL

ESLSTOL is a real number between 0.0 and 1.0. The smaller the value of ESLSTOL, the fewer the number of time steps involved in the optimization process. If ESLSTOL is 1.0, all of the time steps in multi-body dynamic analysis will be involved in the optimization process. Obviously, the smaller the ESLSTOL value, the less total CPU time will be used. Note, however, that assigning too small a value to the ESLSTOL could cause the optimization process to diverge. Therefore, if the number of time steps retained by ESLSTOL is less than 10, the 10 most dominant time steps will be involved in the optimization process. The default value for the ESLSTOL is 0.3.