In this tutorial, a robust optimization of a 25-bars truss structure, an antenna tower, is carried out. The direction of the force acting on the structure and the structural parameter are affected by uncertainties.
Objective of the optimization is to minimize the volume of the structure, while assuring that the maximum nodal displacement is under a certain threshold. Because of the uncertainties involved in the problem, the maximum displacement is varying for fixed values of the design variables. Thus, a design-by-six-sigma approach is used to take into account the output variability in the constraint function.
In order to perform the robust design, it is first necessary to define and inner loop model. This model will be used with a simulation method to obtain samples of the quantities of interest, in this case the maximum nodal displacement.
In a second step, an optimization problem will be created, which constraints will depend from mean and standard deviation of the maximum displacement. To perform the optimization, a mapping between the design variables and the relevant model parameters will be created.
Note that this approach is actually a simplification of RBO, where the distribution of the output is assumed to be Gaussian.
Aim of the Tutorial
The aim of the tutorial is to perform robust design optimization in COSSAN-X.