Research On The Micropositioning Control Of Giant Magnetorstrictive Actuator

Precision positioning is widely used in many fields with the development of precision engineering technology. Giant magnetostrictive material (GMM) is an ideal material to contribute to realizing precision actuator as it has the advantage of large strain, high positioning accuracy. Nonlinearity is also the instinct characteristic of GMM, which will cause overshot and long settling time in normal PID control. Giant magnetostrictive material is the most important component of Giant magnetostrictive actuator (GMA). Some experiments are taken to get the performance of GMA. Based on the experimental results, the thesis presents hysteresis model and feedforward compensation control method. The work could be summarized as follow:In chapter1, the thesis introduces the significance of precision positioning, summarizes the type of precise actuators and their applications, and development of large stroke precise actuator, presents the GMM characteristic, GMA application and control method.In chapter 2, the thesis introduces the structure of permanent magnetic biased GMA and unbiased GMA, and designs to implement experiments for each type of GMA. The change of GMA displacement and hysteresis under different prestress and the applying magnetic field strength is discussed carefully, which is based on the experiment results.In chapter 3, the GMA displacement model is presented which contains the parameters needing to be estimated. Common estimation method, such as least square method, could easily lead to convergence in the early stage. In order to resolve the problem, hierarchical genetic algorithm is used to estimate the model parameters. Finally, the relationship between estimate parameters and experiment condition, such as prestress and the applying magnetic field strength, is carefully discussed.In the chapter 4, to improve control efficiency, inverse compensation controller is added to the close loop control. The parameters of PID controller are solved by Z-N method. Finally, settling time and positioning definition is compared under feedforward control and normal control, respectively.In chapter 5, the thesis introduces the scheme of large stroke precise actuator, and implements some performance test. By following the method of single GMA control, a new method is conceived for controlling three actuators, and the factors which influence the positioning accuracy are discussed.In chapter 6, main work of the thesis is summarized, and the further researches are dicussed, finally.