Research On The Key Technologies Of Force Sensing Actuator With Giant Magnetostrictive Materials

Giant magnetostrictive materials (GMM) attracts wide attention, due to its excellent characteristics of large magnetostrictive coefficient, high magnetomechanical coupling coefficient, fast response capability and easy driving etc. GMM with strong positive magnetostrictive effect and inverse magnetostrictive effect shows bidirectional energy conversion characteristics in the working process. Using GMM as the core element, driving devices and sensors can be developed on the basis of positive magnetostrictive effect and inverse magnetostrictive effect respectively. While GMM works in mechanical constrained condition, there is a coupling effect between positive and inverse magnetostrictive effect. If the coupling characteristics of positive and inverse magnetostrictive effect are known, GMM devices with driving and sensing functions can be developed on the basis of coupling effect between positive and inverse magnetostrictive effects. The development of a single micro-displacement driving device with driving, sensing and other applications is the trend of theoretical research and engineering application in the micro-displacement driving field. Moreover, in the precision and ultra precision machining field, such as the down-force controlling for mechanical polishing process, a driving mechanism with constant output force and controllable output force is needed. Therefore, GMM device which is developed based on the positive and inverse magnetostrictive effects and has an integrated function of force measuring, output force sensing, and output force controlling has a prospect in the engineering application. However, at present, it mainly focuses on the study of single positive magnetostrictive effect characteristics and inverse magnetostrictive effect characteristics, and actuators and sensors developed on the basis of a single effect. However, it lacks of research on the coupling characteristics of positive and inverse magnetostrictive effects, and controllable mechanism of output force. Moreover, there has not been reported on GMM devices with driving, force measuring, output force sensing, and output force controllable functions. Therefore, in this paper, coupling characteristic between positive magnetostrictive effect and inverse magnetostrictive effect of GMM is studied. Based on this, a giant magnetostrictive force sensing actuator which has additional functions of force sensing and output force controllable is developed. It has force measuring, output force sensing, and output force controllable functions besides the driving function for output displacement and force. The research work in details is as follows: First, starting from the manifestation and reason of positive and inverse magnetostrictive effects, occurrence mechanism for positive and inverse magnetostrictive effects is analyzed. Physical principle of the mapping and transfer process relationship among positive magnetostrictive effect, inverse magnetostrictive effect and Faraday effect is studied.The coupling characteristic between positive and inverse magnetostrictive effects of GMM is critical for describing the output performance of giant magnetostrictive force sensing actuator. Starting from the internal energy in GMM, the relationship between output displacement, force and magnetization of GMM when positive magnetostrictive effect and inverse magnetostrictive effect occurs is established. It provides a theoretical basis for the implementation of GMM's output force sensing and the control current solution in the process of output force controlling. According to Weiss ferromagnetic theory and magnetized nature of GMM, and based on the J-A magnetization theory and magneto-mechanical effect method, magnetization quantitative equations of GMM for positive magnetostrictive effect and inverse magnetostrictive effect are deduced and the correlative relationship among magnetization and magnetic field intensity and force is analyzed for the coupling effect of positive magnetostrictive effect and inverse magnetostrictive effect. It provides a theoretical foundation for decoupling of the coupling effect between positive magnetostrictive effect and inverse magnetostrictive effect. A hybrid algorithm which is an improved genetic simulated annealing algorithm is proposed for parameter identification through combining the genetic algorithm and simulated annealing algorithm. In addition, magnetization and magnetostrictive parameters of GMM in the magnetization quantitative equations are identified. The results showed that:the algorithm has advantages of needing fewer measuring parameters, high identification precision and high speed. Meanwhile, according to the magnetization parameters and magnetostrictive parameters of GMM, the relationship among magnetization and magnetic field intensity and stress is simulated and analyzed through Newton's iterative method.For the force measuring, output force sensing, and output force controllable functions of giant magnetostrictive micro-displacement actuator, the relationships between hall voltage and force, induced voltage and force are established. It is starting from the magnetostrictive piezomagnetic equations, principle of Hall effect and Faraday effect. It provides a theoretical basis for the implementation of force measuring. Based on the relationship between output displacement, force and magnetization of GMM, and magnetization quantitative equations, two types of hardware combining with software methods for obtaining the output force are proposed. Meanwhile, the control current solution method for the process of output force controlling is put forward. Based on working principle of giant magnetostrictive micro-displacement actuator, and implementation methods of output force sensing, output force controllable and force measuring, a giant magnetostrictive force sensing actuator is developed through theoretical calculation and finite element analysis method for electromagnetic field. With a GMM rod as the core element, the actuator has the functions of actuator, force sensor, actuating and sensing, and output force controllable. Meanwhile, aiming to its output force controllable function, a control method which is a combination of control current solution method based on the mapping relationship of positive and inverse magnetostrictive effects and PID method is presented. And an output force control system is developed.Finally, output performance experiments for the giant magnetostrictive force sensing actuator are carried out through establishing different experiment platforms and systems. The related force measuring experiment results show that:When the force sensing actuator is used as a force sensor to measure force, the linearity and sensitivity of static force measuring are about±1.01%and-0.29mV/N respectively. The induced voltage peak-peak value for dynamic force measuring is proportional to the force amplitude approximately. The related output displacement experiment results show that:When there is no mechanical constraint, the linear range of output displacement is about0.3A～1.0A (magnetic field intensity is about4.26KA/m～14.2KA/m correspondingly). The related output force controllable experiment results show that:When an artificial disturbance makes the constraint displacement of actuator change suddenly, the control system is able to make the actuator's output displacement follow rapidly until the force between constraints reaches the force target. Output force controllable function for the actuator is realized.In this paper, physical principle of the mapping and transfer process relationship among positive magnetostrictive effect, inverse magnetostrictive effect and Faraday effect is studied firstly. Based on this, the coupling characteristic between positive and inverse magnetostrictive effects is studied. Moreover, implementation principle and method and integration technology for displacement output (or force output), force measuring, output force sensing and output force controllable functions are analyzed and studied. A giant magnetostrictive force sensing actuator which has additional functions of force sensor, actuating and sensing, and output force controllable is developed. Research results provide a theoretical basis and new way for the composite application of positive and inverse magnetostrictive effects and development of multifunctional GMM devices.