The impact force localization inverse problem is considered through a nonlinear optimization procedure. The objective function is derived in the particular case of elastic structures for which Maxwell-Betti theorem holds. Additional geometric constraints were introduced in order to stabilize optimum search. The solution of the constrained non linear mathematical problem was performed by means of two outstanding evolutionary algorithms that include Genetic Algorithm and Particle Swarm Optimization. Focus was done on the robustness aspect of force impact localization predictability when an additive white noise is assumed to perturbed strain measurement. It was found that the Genetic Algorithm fails to track the exact solution independently from the noise level as an error was systematically present in the solution. On the other hand, the Particle Swarm Optimisation based algorithm performed very well even for noise levels as high as 2% of the measured strain signal. 1. Introduction Identification of impact force location for impact events occurring on elastic structures can be performed by various methods that were proposed in the literature [1–3]. To review briefly some of the important contributions in this filed, Martin and Doyle [4] have described how to find the location of an impact force using dynamic response measurements. They proposed a solution procedure using the spectral element method with a stochastic iterative search. Experimentally measured acceleration responses from two frame structures were used to achieve force localization by minimizing a fitness function. A Genetic Algorithm was used to guess iteratively the minimum through monitoring the actual error associated to a given sampling generation. The process enabled to discriminate between good and bad guesses and gave at convergence the correct impact location. An alternative technique which employs the arrival time of each frequency component of a pulse detected by means of wavelet transform was proposed by Inoue et al. [5]. But this approach suffers from the lack of accuracy in measurement of small arrival times of signals. Yen and Wu [6, 7] have used multiple strain responses along with a mutuality relationship based on Green’s functions and measured strains to achieve identification of force location on two-dimensional plate-like structures. Choi and Chang [8] minimized the error between measured strain responses in PZT sensors and numerically evaluated impact force locations. Shin [9] proposed a technique for identifying the force location using modal displacements and transient
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