IDENTIFICATION OF EXTERNAL LOADS IN MECHANICAL SYSTEMS THROUGH HEURISTIC-BASED OPTIMIZATION METHODS AND DYNAMIC RESPONSES

Abstract

THIS PAPER PRESENTS AN INVERSE PROCEDURE FOR THE DETERMINATION OF EXTERNAL LOADS, GIVEN THE DYNAMIC RESPONSES OF THE LOADED STRUCTURE AND ITS CORRESPONDING ¯NITE ELEMENT MODEL. THE INFUENCE OF THE STRESS-STIFFENING EFFECT ON THE DYNAMIC CHARACTERISTICS OF STRUCTURAL SYSTEMS IS USED TO ESTABLISH A RELATION BETWEEN THE DYNAMIC RESPONSES AND THE APPLIED EXTERNAL LOADING. AN OPTIMIZATION PROBLEM IS FORMULATED IN WHICH THE OBJECTIVE FUNCTION REPRESENTS THE DIFFERENCE BETWEEN THE MEASURED MODAL CHARACTERISTICS OF THE LOADED STRUCTURE AND THEIR FINITE ELEMENT COUNTERPARTS. THE LOADING PARAMETERS (MAGNITUDE, POSITION AND DIRECTION) ASSUMED AS BEING UNKNOWN, ARE CONSIDERED AS DESIGN VARIABLES. THE IDENTI¯CATION PROCEDURE IS ILLUSTRATED BY MEANS OF NUMERICAL SIMULATIONS, IN WHICH THE IDENTI¯CATION PROBLEM IS SOLVED BY USING HEURISTIC TECHNIQUES COUPLED WITH CLASSICAL OPTIMIZATION METHODS. TWO HEURISTIC TECHNIQUES ARE CONSIDERED, NAMELY THE LIFECYCLE MODEL AND PARTICLE SWARM OPTIMIZATION. THE CLASSICAL OPTIMIZATION STRATEGY IS THE LAGRANGE-NEWTON SQP (SEQUENTIAL QUADRATIC PROGRAMMING) METHOD.