Nonlinear Dynamic Modeling And Experimental Study Of Giant Magnetostrictive EHA Considering Magneto-mechanical Coupling

The giant magnetostrictive material Terfenol-D is an ideal driving element for the development of miniaturized high bandwidth electrohydrostatic actuator,which has the advantages of large magnetostrictive strain,wide working frequency,fast response speed and high positioning accuracy.The giant magnetostrictive electrohydrostatic actuator utilizes the fluid rectification function of the check valve to amplify the small high-frequency vibration of the giant magnetostrictive material into the large displacement movement of the hydraulic cylinder.Although predecessors have developed intelligent electrohydrostatic actuators based on this principle,the operating frequency of these actuators is limited to a small part of the available bandwidth of their driving materials.Based on this,the giant magnetostrictive material Terfenol-D is used as a driving element to develop a giant magnetostrictive electrohydrostatic actuator in the thesis,and conducts related research from two aspects: theoretical modeling and experimental testing:(1)According to the working principle and material-related characteristics of the giant magnetostrictive electrohydrostatic actuator,the overall design scheme of the actuator is proposed,and the functional characteristics and design of related structures and components are introduced in detail claim.According to the related requirements involved in the experimental test of the actuation system,the relevant structure of the actuator is optimized.(2)Based on the Jiles-Atherton model and the "proximity principle",a magnetomechanical coupling model of the giant magnetostrictive material Terfenol-D is established,and the dynamic characteristics of Terfenol-D under stress and magnetic field are described.The changes of the material’s magnetization,magnetostrictive strain and elastic modulus under the combined effects of stress and magnetic field are analyzed.(3)On the basis of the established magneto-mechanical coupling model,based on theories of mechanical dynamics and fluid mechanics,a dynamic output model of the actuator system level is established,according to the theory of electro-hydraulic analogy and the fluid-structure coupling characteristics of the check valve,the dynamic model of fluid system is established,and the effective bulk modulus of fluid is treated as a function of pressure.The influence of bulk modulus and density of fluid on the output performance of actuator is described.The fourth-order Runge-Kutta method is used to iteratively solve the model.The calculation results show that factors such as input current,operating frequency,prestress,bias pressure,and driving load affect the output performance of the giant magnetostrictive electrohydrostatic actuator.(4)The experimental prototype of the giant magnetostrictive electrohydrostatic actuator is fabricated and an experimental test platform is built.The actuator is tested.The test data agrees well with the simulation calculation results,which verifies the accuracy of the model.The test results show that the output speed of the actuator changes in a double peak with the driving frequency,and the peak frequency increases with the increase of the bias pressure.When the bias is 2.6 MPa,the optimal output level is reached.