Research On The Electric-magnetic-thermal Characteristics Of Giant Magnetostrictive Actuator And Its Applications

Giant magnetostrictive material (GMM) is a kind of smart materials withbidirectional reversible energy conversion characteristics. Compared to thetraditional actuators, actuators based on giant magnetostrictive material have manymerits, such as high precision, high speed, high reliability, etc. It has broadapplication prospects in precision motion control, active damping, precision fluidcontrol technology, et al. In this thesis, different types of GMA are put into forward,and the problems of stress-strain linear relationship model, the equivalent circuitmodel, highly uniform driven magnetic field design method and dynamic lossesnumerical method have been studied. Different kinds of GMA are developed and acomprehensive experimental platform is built. Two kinds of giant magnetostrictiveflow control valves (GMV) are developed and tested. The results have a universalsignificance for the design and application of GMA. And the development of GMVhas a practical application value.Based on free energy minimization principle and the magnetic domaindeflection theory, this thesis derived a simplified giant magnetostrictive materialstress-strain linear mathematical model from the micro actuating mechanism ofGMM. The lumped equivalent circuit model and distributed parameter equivalentcircuit model of GMM are established. Considering the eddy hysteresis loss and theinfluence of high magnetic permeability material to the external magnetic circuit,the equivalent circuit model of the GMM under closed magnetic loop is analyzedand established. It can express the coupled rules between the macro displacementoutput and the excitation parameters during the GMM’s work process, intuitively.Based on the analysis of the magnetic circuit structure feature for GMA, thevariation of the magnetic field with different driving solenoid magnetic structuresare studied, using the equivalent circuit method. The influences of the geometry ofsolenoid and the magnetic structure on the driving magnetic field homogeneity anddrive efficiency are derived. The results show that: with a closed magnetic circuitstructure, the GMM rod has the highest axial uniformity magnetic field when thedrive coil has the same axial length of the GMM rod. The diameter of the magneticblocks is most impact of the radial magnetic field distribution at the ends of GMMrod. Using segmented current-driven approach can effectively improve theuniformity of axial magnetic field in GMM rod, but more difficult to be realized.The analytical expression of the GMA’s inductance parameters is derived. Thevariation of the GMA’s inductor parameters is studied using the finite elementmethod, considering the changes with permeability characteristics of GMM. And then, the optimized design guidelines for GMA are established.A further research is carried on the thermal problem of GMA. Based onmagnetic domain deflection theory, the magnetization curve numerical method ofGMM is derived. The establishing process of the magnetic field and the loss ofGMA is analyzed and calculated. And the loss and heat under dynamic excitationare analyzed by simulation. Then the heat transfer, heat balance and temperaturecharacteristics of GMA are summarized. The results showed that: the drivefrequency of GMM will affect the magnetic energy loss, changing the distributionin GMA temperature. Under low frequency, the temperature in the end portion ofGMM rod is higher than that in the middle. Corresponding to the high frequencysituation, the temperature of the middle part in GMM rod is higher.Finally, the actuator based on the giant magnetostrictive material isdeveloped.A special current source is designed and the integrated test platform forGMA is constructed. The static and dynamic displacement output characteristics ofGMA are tested and analyzed.The results show that, dynamic response of GMAdepends on the response time of driving current source. Due to the dynamichysteresis and eddy current effects, the output position of GMA is slightly lower asthe drive current frequency increases.Two kinds of GMV with different shape ofGMM rod are designed.Test results show that, under the same steady flow rate state,the response time of the GMV with a displacement amplification mechanism isnearly15-times less than the conventional solenoid valve.The flow rate of singleswitch period of the GMV with internal cooling structure is only0.0099g/s.Combined with PWM control technology, it is suitable for high-pressure,high-speed, high-precision flow control system applications.