| Giant Magnetostrictive Material(GMM)is a functional material with superior performance,which has outstanding advantages such as large gauge factor,high conversion efficiency,fast response speed,high power density,good frequency characteristics and high Curie temperature.The application of GMM to develop giant magnetostrictive vibration exciters can make up for the following shortcomings of mechanical vibration exciters:It is difficult to approach the natural frequency of high-rigidity components when the vibration frequency is lower than 200Hz;the excitation force cannot be smoothly adjusted;it is driven by a motor,which has low reliability and short life.However,for a long time,mechanical vibration exciters have dominated the field of vibration aging.Therefore,the research and development of giant magnetostrictive vibration exciters is of practical significance to the further promotion of vibration aging technology,accelerating the replacement of vibration aging equipment and even industrial upgrading.In this paper,the giant magnetostrictive vibration exciter is regarded as the research object,and its structure design,system modeling,parameter identification,heat loss analysis,heat conduction model and response characteristics are studied.The principle prototype of the giant magnetostrictive vibration exciter was designed and tested.The research results have guiding significance for the theoretical analysis and engineering design of the giant magnetostrictive vibration exciter,and the principle prototype produced has application value in the field of vibration aging.A new structure of giant magnetostrictive vibration exciter is developed.When the magnetostriction coefficient under the dynamic magnetic field is large,the required magnetic field strength will increase accordingly.Since the design of the drive coil is restricted by factors such as the number of coil turns,current size,coil inductance and time constant,the operating frequency of the vibration exciter will not meet the design requirements,and the power loss of the drive coil cannot be effectively controlled.Therefore,the appropriate magnetostriction coefficient is selected to reduce the dynamic range of the magnetic field strength,and the cross-sectional area of the GMM rod is increased to obtain sufficient output force.The drive coil adopts the design scheme of reducing the number of turns,increasing the wire diameter and the current to reduce the inductance and the loss.Utilize the frequency doubling effect of giant magnetostrictive material without applying a bias magnetic field to optimize the magnetic circuit structure.Permalloy is used to increase magnetic permeability to reduce magnetic resistance,while reducing magnetic flux leakage and improving magnetic field uniformity.The time constant of the driving coil is compensated to shorten the response time and improve the dynamic performance of the giant magnetostrictive vibration exciter.The system model of giant magnetostrictive vibration exciter is established.The system modeling of giant magnetostrictive vibration exciter includes three aspects:magnetostriction model,magnetization model and structural dynamics model.Among them,the magnetostriction model describes the relationship between magnetization and magnetostriction coefficient,and the model is established by using the quadratic domain transformation model.The magnetization model,which describes the relationship between magnetic field intensity and magnetization intensity,is established by Jiles-Atherton model.The physical meaning of the model is clear,but it contains 5 undetermined parameters.The structural dynamic model is composed of displacement model and excitation force model,which is established by Newton's second law.The combination of magnetostrictive model,magnetization model and structural dynamics model can clearly reflect the relationship between excitation current and excitation force.The Jiles-Atherton model is replaced by the linear magnetization model,and the linear model of the giant magnetostrictive vibration exciter is established,which is applied to the open-loop control of the vibration exciter.The immune genetic algorithm is used to identify the pending parameters of the Jiles-Atherton model.In order to avoid the improper parameter setting causing premature populations and making the search results to fall into the local optimum,an adaptive strategy is adopted to dynamically adjust the crossover probability and mutation probability,and the immune genetic algorithm is used to identify the parameters of the Jiles-Atherton model.Based on the identification results and the least square method,a linear function is used to curve-fit the magnetic field intensity and the magnetization intensity,and a linear magnetization model is established to replace the Jiles-Atherton model,which is applied to the control of the giant magnetostrictive vibration exciter.Therefore,the shortcomings of complex solution process and difficult engineering application of the Jiles-Atherton model were overcomed,which provides a reference basis for exciting current-exciting force control.Under the highest frequency dynamic magnetic field,The hysteresis loss and eddy current loss of the vibration exciter are analyzed,and the heat conduction model of the radiator is established.Under the dynamic magnetic field with the highest operating frequency of the vibration exciter,when the diameter of the GMM rod is fixed,the hysteresis loss is estimated by considering the complex permeability,and the Galerkin weighted margin finite element method is used to estimate the eddy current loss.Analysis shows that hysteresis and eddy current are the secondary factors that produce loss,and the main factor that drives the coil to generate heat is resistance loss.In order to achieve natural cooling,an aluminum radiator with an annular finned structure is designed,and the second law of thermodynamics is used to establish a heat conduction model for the radiator and calculate the heat dissipation efficiency.The simulation and test results of heat dissipation performance show that the maximum temperature of the vibration exciter is effectively controlled,and the designed radiator can ensure the stable operation of the vibration exciter.The accuracy of the giant magnetostrictive vibration exciter system model is verified.Applying the analysis method of non-sinusoidal periodic quantity,using the first four terms of Fourier series as the approximate expression of excitation current,the excitation current,magnetic field intensity,magnetization intensity,magnetostriction coefficient,GMM rod output force and excitation current are described.The relationship between the vibration force,within the operating frequency range of the vibration exciter,the excitation current and the excitation force are approximately linear.Experiments have shown that the rise time,peak time,response time,overshoot and time constant of the step response are consistent with theoretical analysis.When the excitation current changes within 2.5?30A,the magnetic field intensity is 1.5?31.5A/m,the magnetization intensity is 12.9?216.9A/m,the excitation force can be adjusted within 0.343?9.98kN,and the maximum excitation force meets the design requirements,the accuracy of the giant magnetostrictive vibration exciter system model established by the magnetostrictive model,linear magnetization model and structural dynamics model has been verified. |
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