On the Investigation of Nonlinear Dynamics of a Rotor with Rub-impact Using Numerical Analysis and Evolutionary Algorithms

In this paper the dynamics of a rotor-stator system with mass imbalance induced rub-impact interactions is investigated with particular attention on the routes to chaos. The rub-impact interaction is modelled by a Hertz contact radial force and a Coulomb friction tangential force. Extensive numerical experimentation for a wide range of parameters shows the resulting response to be rich in subharmonic, quasiperiodic and chaotic motions. Parameter identification of chaotic systems has become an important topic of research in the past decade. Of particular interest is the problem of identifying or estimating system parameters when the quasiperiodic or chaotic responses of the system are known. The problem of identifying parameters can be cast as an optimization problem and non-traditional optimization methods such as evolutionary algorithms, simulated annealing and others have been developed to identify system parameters. In this paper, three evolutionary algorithms – particle swarm optimization, differential evolution and firefly algorithm are presented and compared for the problem of identifying parameters of a rotordynamical system given a chaotic response. The results of this analysis can potentially be of a considerable value as diagnostic tools in assessing condition monitoring signals that are routinely taken on modern rotating machinery.