Mechanical engineering: designing roof trusses and improving vehicle safety.

In the following, two applications of Reactive Taboo Search (RTS) by prof. Kazuhiro Saitou and co-authors (K. Hamza, H. Mahmoud, A. Nassef), at Department of Mechanical Engineering University of Michigan are briefly summarized. Actually, they propose interesting modifications of the basic RTS scheme. Tools related to RTS are now supported also in the Reactive Search Optimization framework of LIONoso.

Photo of actual N-shaped truss, a plane truss that has a certain general shape resembling the letter "N".

Mechanical and industrial engineering demand for automated or semi-automated simulation-based optimization is growing, fueled by a greater emphasis on efficiency, safety, robustness, and flexibility. Recently, co-design is changing the conventional design processes and replacing them with design processes that make customers an integral and active member of the design team. The rapid integration of different software components (installed on the customer premises and in the design team) and the possibility to quickly adapt processes and strategies through online intelligent and learning schemes is crucial.

Design optimization of N-shaped roof trusses using reactive taboo search

Abstract: Design optimization of a class of plane trusses called the N-shaped truss (NST) is addressed. The parametric model of NST presented is intended for real-world application, avoiding simplifications of the design details that compromise the applicability. The model, which includes 27 discrete variables concerning topology, configuration and sizing of the truss, presents a challenging optimization problem. Aspects of such challenge include large search space dimensionality, absence of a closed-form objective function (OF) and constraints, multimodal objective function and costly CPU time per objective function evaluation. Three implementations of general-purpose genetic algorithms (GAs) are tested for this problem, along with a version of taboo search called reactive taboo search (RTS). In this study, the raw version of RTS exhibited better performance than the tested versions of GA but lacks some of the GA capabilities to span the search space. A modification of RTS that uses a population-based exploitation of the search history is proposed. The optimization results show that the introduced modification can further improve the performance of RTS.

A comparison of RTS (Reactive Tabu Search) and Genetica Algorithms (GA) from the cited paper.

A digital version of the paper is now available here.

Desing optimization of a vehicle B-pillar subjected to roof crush using mixed Reactive Tabuu Search

Abstract: The primary obstacle in automated design for crashworthiness is the heavy computational resources required during the optimization processes. Hence it is desirable to develop efficient optimization algorithms capable of finding good solutions without requiring too many model simulations. This paper presents an efficient mixed discrete and continuous optimization algorithm, Mixed Reactive Taboo Search (MRTS), and its application to the design of a vehicle B-Pillar subjected to roof crush conditions. The problem is sophisticated enough to explore the MRTS' capability of identifying multiple local optima with a single optimization run, yet the associated finite element model (FEM) is not too large to make the computational resources required for global optimization prohibitive. The optimization results demonstrated that a single run of MRTS identified a set of better designs with smaller number of simulation runs, than multiple runs of Sequential Quadratic Programming (SQP) with several starting points.

Design variables for the B-pillar (from the cited paper)

A digital version of the paper is now available here.

Karim Hamza, Haitham Mahmoud, Kazuhiro Saitou,
Design optimization of N-shaped roof trusses using reactive taboo search,
Applied Soft Computing, Volume 3, Issue 3, November 2003, Pages 221-235, ISSN 1568-4946, 10.1016/S1568-4946(03)00036-X. (

Karim Hamza, Kazuhiro Saitou and Ashraf Nassef,
Proceedings of DETC' 03 ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference Chicago, Illinois, September 2-6, 2003