Experimental modal analysis of non-self adjoint systems: inverse problem regularization

Abstract

When dealing with experimental modal analysis of non-self adjoint problems (rotordynamics, vibroacoustics, active control...), the nonsymmetry of the system induces specificities that must be considered for proper use of identification techniques. In this paper, the particularities of this kind of problem are addressed in order to be able to efficiently identify the dynamic behaviour. The first matter which is detailed is related to the ability of the technique to identify both right and left eigenvectors. The second point is associated to the regularization of inverse problem for matrices identification using the complex eigenvectors. The inverse procedure, which is one of the ways allowing the damping matrix identification, is very sensitive to noise. The technique of properness enforcement, already available in the context of symmetric systems, has been extended to nonself adjoint in order to regularize the problem. A numerical test-case has been performed on a rotordynamics application, and some experimental results are presented on a structural active control application.