Compound Damages Detection for Rotors by the Coupled Piezoelectric Impedance

The rotor is a key component of rotating machinery, thus it is of great importance to quantitatively detect its damage. Since the sensitivity matrix in the impedance-based rotor damage identification model with a single piezoelectric transducer has lower rank and the available impedances are not sufficient enough, a highly underdetermined inverse problem arises, which may seriously affect the identification of the damaged location and severity. It follows that a coupled impedance-based composite rotor damages detection method with double piezoelectric transducers is proposed to improve the accuracy of damage identification. In this method, the dynamics characteristics of the electromechanically coupled system can be changed by adding a piezoelectric transducer and a corresponding circuit. Thus the coupled impedance is different from the rotor impedance based on a single piezoelectric transducer. Moreover, owing to the different locations of the two piezoelectric transducers, two sets of sensitivity matrix which are linearly independent with each other are derived, and then more available admittances can be obtained by exciting the two piezoelectric transducers successively. Obviously, the rank of the sensitivity matrix can be increased and the ill-posed inverse problem of damage identification equations can be well improved, which leads to an accurate damage detection. Simulated and experimental results show that the proposed coupled impedance-based composite rotor damages identification method with double piezoelectric transducers can more accurately identify the locations and severities of the compound damages and be more suitable for the detection of composite tiny damages, compared to the impedance-based damage detection method with a single piezoelectric transducer.