| The giant magnetostrictive actuator,which uses the giant magnetostrictive materials bar as the driving element,has the excellent performance of high driving accuracy,wide damping band,and good low frequency characteristics,and can convert electromagnetic energy into mechanical energy by magnetostrictive effect,which is the core device to realize active vibration control.However,due to the hysteresis nonlinearity inherent in GMM,the input current of GMA has the complex nonlinear relationship with the output displacement and output force,which is not conducive to predicting the output performance of GMA and improving the control accuracy of GMA.Therefore,in this paper,GMA is used as the research object in structural design,internal physical field finite element analysis,structural parameter optimization,hysteresis nonlinear modeling and dynamics simulation.The main research works are as follows:Firstly,the design requirements and overall structure of GMA are determined according to the mechanism of magnetostrictive effect and the working characteristics of GMM,and then the selection of the GMM bar and the design of the drive coil,magnetic circuit structure,cooling device and preloading mechanism are completed according to the design requirements and the target parameters.The comparative analysis of the coils illustrates that the coil wound by enamelled rectangular copper winding wires can generate stronger driving magnetic field than the coil wound by enamelled round winding wires of the same size.By constructing the magnetic circuit model of GMA,it is shown that the axial magnetic field strength and the magnetic field uniformity of the GMM bar are related to the structural parameters of the drive coil and the magnetic conductivity members.By analyzing the internal heat transfer process of GMA,it is illustrated that the steady-state temperature of the GMM bar is related to the flow rate of cooling water and the structural parameters of the cooling chamber.Secondly,based on the structural parameters of GMA,finite element analysis of the magnetic field and the temperature field are carried out by COMSOL Multiphysics software,and then the magnetic circuit structure and cooling device of GMA are optimized based on the mapping relationships between the structural parameters of the drive coil and the magnetic conductivity components and the axial magnetic field strength and magnetic field uniformity of the GMM bar,and between the flow rate of cooling water and the structural parameters of the cooling chamber and the steady-state temperature of the GMM bar,respectively.By optimizing the magnetic circuit structure,the average value of the axial magnetic field strength of the GMM bar increases from 87.53 k A/m to 95.02 k A/m,and the magnetic field uniformity increases from 77.95% to 90.45%.By optimizing the cooling device,the maximum and minimum values of the steady-state temperature of the GMM bar are in the optimal operating temperature range of 40°C to 50°C,and its average value is reduced from54.38°C to 47.39°C.Finally,based on the Jiles-Atherton model,the hysteresis nonlinear model between magnetic field strength and magnetization intensity is established by considering the effects of steady-state temperature and precompression stress on the magnetization state of the GMM bar.Meanwhile,the dynamic mathematical model of GMA between input current and output displacement and output force is established by combining the magnetic field model,secondary magnetic domain rotation model,nonlinear piezomagnetic equation and equivalent kinetic model.Then,based on the dynamic mathematical model of GMA,the dynamics simulation model is constructed by MATLAB/Simulink software.By comparing the output performance of GMA before and after optimization,it is shown that the output displacement of GMA after optimization can reach 322 μm,which is 19 μm higher than that before optimization,and it can meet the requirement of maximum output displacement in the target parameters.The output force of GMA after optimization can reach 3175 N,which is 208 N higher than that before optimization,and it can meet the requirement of maximum output force in the target parameters.In addition,the effect of different load mass,load stiffness and load damping on the dynamic response of GMA is quantitatively analyzed with the unit step signal as input,which shows that the dynamic response of GMA can be improved by reducing the load mass and increasing the load damping,while the output force and output displacement of GMA can be ensured to be larger by reducing the load stiffness. |
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