Study On Electromagnetic-Mechanical Reversible Conversion And Fundamental Application Of Magnetically Controlled Shape Memory Alloy

Magnetically controlled shape memory alloy (MSMA) is a new functional material which is found in recent years. The material can produce large induced strain by magnetic field,and has fast dynamic response, high efficiency of electromagnetic-mechanical conversion and excellent controllability. The magnetically controlled shape memory effect of MSMA material possesses reversibility. The MSMA element can not only output displacement and force under magnetic field but also produce large induced voltage through variation of magnetic property under external force.The research work of this thesis is a part of the project"study on self-sensing actuator based on magnetically controlled shape memory reversible effect"supported by the National Natural Science Foundation of China (No. 50777043). The study is mainly concentrated to the basic application of MSMA material for sensors and self-sensing actuator. The main works of the thesis are listed as follows:Magnetically controlled shape memory characteristics for the deformation mechanism, phase transition temperature and shape recovery of MSMA material are described, some key parameters of MSMA external characteristics and their relations are analyzed. A MSMA integrated testing platform is developed, which can simultaneously measure deformation, pressure, temperature and magnetic field. Through the measurement of these parameters, the influence law of force, magnetic field and temperature on the deformation of MSMA material can be further understood. According to the difference of the force acting on MSMA material, the testing methods are discussed for the MSMA static and dynamic characteristics of mechanical-electromagnetic conversion.With the help of the developed integrated testing platform, electromagnetic- mechanical properties of MSMA material are tested. Based on the thermodynamic model and the calculation method of magnetic field-induced stress, the analytical expression of output displacement and force are determined for MSMA working as an actuator. The model can quantitatively describe the output displacement and force of the actuator under the magnetic field, temperature and stress. Based on MSMA linear actuator and differential control strategy, dual drive and differential MSMA rotating actuator are developed in which the linear motion produced by the MSMA element can be converted into rotating movement through an overstepping clutch. The experimental results of the prototype prove the feasibility of the mechanism and the design method of the MSMA rotating actuator.Mechanical-electromagnetic characteristics of MSMA material are tested, which reflects the variation laws of MSMA material under the static and dynamic force. The relation between magnetic flux density and external force is determined based on the stress-strain relation and the magnetic circuit model when MSMA is used as a sensor. Based on the MSMA mechanical-electromagnetic characteristics, a MSMA vibration sensor is developed. The relations between the sensor output voltage, driving force (amplitude and frequency) and bias conditions (pre-stress and bias magnetic field) are analyzed under sinusoidal excitation force. The experimental results show the correctness of the induced voltage model when MSMA works as a sensor.Based on the operating principle of actuator and sensor, the MSMA self-sensing actuator prototype is developed, which can realize active vibration control. The decoupling method of double-coil space-division multiplexing is adopted for separating actuating signal and sensing signal, the misoperation caused by signal conversion and interference can be avoided through the method of applying the bias magnetic field and the signal shielding. The experimental results show that the MSMA self-sensing actuator has good elimination effect for the periodic and non-periodic vibrations.