Modeling And Control Method Of Giant Magnetostrictive Microdisplacement Actuator

Giant magnetostrictive material (GMM) is a kind of promising smart material. It indicats the wide prospect in the actuator application field relying on its advantages of giant magnetostriction, high coupling coefficient, fast response, easy to drive and excellent structural performance. The scientists from all over the world paid more attentions to researches on working mechanism and applications about devices comprising of GMM rod or film. The problems of strong nonlinearity, working environment dependency, and poor open loop precision are the bottlenecks of the application of GMM devices.The thesis concentrates on the analysis, simulation, modeling and control actuator working in the situations of the precision and ultra-precision field. It studies the working principle and its nonlinearity to set up giant magnetostrictive actuator's control model and solve the accurate control problem. The results will direct the actuator design, provide the method of Giant magnetostrictive actuator accurate control and basic theory for giant magnetostrictive actuators applicated in the precision and ultra-precision field.It firstly state the characteristics of GMM systemically, analyses the external stress, magnetization field, magnetomechanical coupling and temperature influences on GMM characteristics. It presents the caculating method of the actuator's mechanical, magnetic and thermal system, and utilizes the finite element method to analysis the actuator's prestress mechanism, modal mode, permanent and electromagnetic magnetic circuit. It will provide the basic theory for the actuator's analysis, modeling and control.In view of GMM magnetization process, on the basis of ferromagnetic hysteresis model presented by Jiles-Atherton and magnetomechanical effect presented by Jiles, dynamics and magnetic parameters identification method is presented for giant magnetostrictive actuator in the view of energy equilibrium equation. based on the experimental data and estimated by least square method (LSM), The method included reasonable deduction and transformation about the model. To study the Giant magnetostrictive actuator under the external uniaxial stress, utilizing the homogenized energy field model and magnetomechanical couple theory, Defining the average magnetization caculated by the theory of magnetomechanical effect as hystresis operator, and adjusted the interactive and coercive density function with the change of external stress of homogenized energy model., it presents a magneto-mecchanical coupled model. Meanwhile, it gives the inverse algorithm for the model and sketches the error between the model and its inverse algorithm. The model can describe the magnetization process under the compress stress well.Considering the system integral characteristics of giant magnetostrictive actuator, from the view of system dynamics and electromechanical transformation process, it sets up a mathematical model for giant magnetostrictive actuator. Regarding GMM rod as a viscoelastic rod continuous system and treating the induced strain by external magnetic field as equivalent force. It built a one dimension wave equation for the actuator. The solution of the equation by finite element method was given. The simulated and experimental results indicated the validity of the model.Employing the linear piezomagnetism equation, electromechanical transformation equation and impedance analysis method, it sets up the vector impedance model of the system.The model divides the system vector impedance into two sections, mechanical admittance and electrical impedance. Considering the external load influence and defineing the coefficient of pizeomagnetism as a constant complex variable, it simulates the displacement hystersis.In the solved magnetization of the magnetostrictive material; it added eddy current term to simulate the system nonlinear characteristics. The sum of two sections is the system vector impedance. As indicated in the comparison between experimental and model data.the results show us the model can be simulated the system impedance characteristics.For the trajectory track problem of giant magnetostrictive actuator system, it employs the linear and nonlinear system equation to build and simulate the PID and discrete sliding mode variable structure control law. It set up the state equation of system by system identification method, takes the state equation as the system model to design the PID controller for Giant magnetostrictive actuator, applys Ziegler-Nichols method and SRS (Step Response Specification) module block setting the PID control parameters separately. Employing the Homogeneity energy model as magnetization model, utilizing the viscoelasticity distributive parameters system model as dynamics model and placing an model-based inverse filter before the system to compensate the hysteresis, It implements the adaptive discrete sliding variable structure control on the plant designed by exponential reaching law method. The system chattering amplitude is proportional to the switching function. The two control strategys express good control accuracy in the simulation.It finally Builds an xPC target system platform for GMM actuator real-time control, utilizes the experimental platform to verify the PID control strategy and discrete sliding variable structure control strategy for GMM actuator control, and Resets the parameters of PID and discrete sliding variable structure control. The square waveform, sine waveform and hybrid signal trajectory track was tested. The experiment shows that the PID controller has a good control precision of square waveform and adapted to low cost static and quasi-static accurate position and feeding occasion. The discrete sliding mode controller controlled system is more accurate than PID controller's and adapted to high precision real-time control application.