Study Of Hysteresis Nonlinear Models For Giant Magnetostrictive Transducers

The relationships between the inputs and the outputs of giant magnetostrictive transducers exhibit dominant magneto-mechanical coupling and hysteresis nonlinear behaviors under the magnetostrictive effect and the inverse magnetostrictive effect. To design and use the devices, it is necessary to establish an accurate model of the devices. In this dissertation, hysteresis nonlinear models for giant magnetostrictive transducers are studied systematically and deeply, the main research contents and contributions are given as follows.1. The linear piezomagnetic equation is extended to a nonlinear constitutive model (called the Model I in this paper) based on a quadratic moment domain rotation magnetostriciton model and an anhysteretic magnetization model. A nonlinear constitutive model (called the Model II in this paper), which is founded by thermodynamic relations, is presented. The magneto-mechanical coupling nonlinear experimental behaviors for giant magnetostrictive materials are simulated using the two constitutive models. The performances of the two models are compared and analyzed, which provides a theory basis for modeling a magneto-mechanical coupling hysteresis nonlinear model of giant magnetostrictive transducers.2. A hysteresis model of giant magnetostrictive transducers is presented. The hysteresis model is based on the Jiles-Atherton model. To obtain optimal parameters of the hysteresis model, four hybrid genetic algorithms, namely GATR1, GALM1, GATR2 and GALM2, are proposed by combining the gradient-based algorithms with a hybrid coded genetic algorithm. The simulation and experimental results show that GATR1 can automatically and accurately identify the parameters of the hysteresis model at different frequencies, thus can extend the hysteresis model to a dynamic hysteresis model, which can accurately describe the relationship between the input magnetic field and the output strain for the transducers in a wide frequency range.3. A magneto-mechanical coupling dynamic hysteresis nonlinear model for giant magnetostrictive transducers under applied magnetic field is founded according to the nonlinear constitutive Model II, the Weiss ferromagnetic theory, the Jiles-Atherton model, the Bertotti loss statistical physical theory and the transducer structural dynamics principle. Comparisons between the experimental and the calculated results show the proposed model can describe the magneto-mechanical coupling dynamic hysteresis characteristics of the input magnetic field, the output magnetization and strain for the transducers in a wide operating conditions (such as different bias magnetic field, different drive frequency and different pre-stress), thus has important significance for performance estimation and controller design of the transducers.4. The updated expressions of the memory curve vertex coordinate matrix for Preisach model are derived under all kinds of input sequences. Based on the memory curve vertex coordinate matrix, a Preisach-type neural network hysteresis model of giant magnetostrictive transducers is founded. Simulation results show that the proposed model can eliminate the constraint in input sequences when using the traditional Preisach model, and can predict the output magnetization and displacement hysteresis characteristics under the complicated applied magnetic field.5. Based on the Jiles-Atherton model, the law of approach for the magnetomechanical effect and the magnetic circuit law, a hysteresis model of a giant magnetostrictive device for magnetic force control is founded. Comparisons between the experimental and the calculated results show that the proposed model can better describe the hysteresis relationship among the input stress, the output magnetization and magnetic force for the device under varying stress and constant bias magnetic field. Moreover, the proposed model can predict the effect of the bias magnetic field on the output performance of the device. Thus, the model has important significance for design and analysis of the magnetostrictive transducers based on the inverse magnetostrictive effect.