Research On Shape Memory Alloy In Structure Design And Controller

As the research on shape memory alloy(SMA) has become an important content of intelligent material, analysis and research the driving form and controlling process of SMA actuator are paid more and more attention. SMAs have been widely applied to mechanical engineering, medical equipment, aerospace, robotics, etc. Most current researches don’t consider to control the deformation stress of SMA’s constitutive model, so the stress are vulnerable to be influenced by the external loads and the surrounding environment. In the application of SMA actuator as a drive, the control precision remains to be further promoted. This thesis explores to apply a constant force to control the deformation process of SMA phase transition, appropriately improve the control strategy and deformation mode of SMA actuator, and two kinds of SMA actuator system are established to improve the driving ability. The main contents are as follows:In chapter1, the background and significance of this project are presented, the development status of SMA and SMA actuator are summarized, the application of SMA actuator in various fields are introduced. After these discussions, the main objective of this research project is shown at the end of this chapter.In chapter2, the SMA’s properties are introduced, focusing on shape memory effect(SME), pseudelastic effect(SE), temperature memory effect(TME) and resistance characteristics. Several typical constitutive models of SMA are analyzed and compared. After balancing between them, one model is chose which is considered to be suitable for this research project and the relationship between resistance and stress is established. These models were fundamental for analyzing the system.In chapter3, one dimensional constitutive model of SMAs are established, the temperature variation characteristics following the process of heating and cooling are analyzed. With MATLAB/Simulink toolbox, a time-domain simulation analysis are made for SMA system. Experimental bench is designed and built, the PLC control system is introduced to implement the constant force control of SMA deformation process. Through the analysis and evaluation of the experiment result, the feasibility of model is verified.In chapter4, the common control methods are introduced, such as the neural network control, fuzzy control and PID control algorithm. After balancing between them, one control strategy is chose which is considered to be suitable for this research project.two types of SMA actuator system are introduced, the methods of control process are provided theoretical research. The actuator system and control algorithm are studied, the corresponding experimental platform is built, the control algorithm is verified through simulation analysis and experimental research. First, the structure of bias type SMA actuator is designed, with emphasis on describing the rotating body, achieving synchronous rotation between the angular displacement sensor and the rotating body. Second, the driving control performance of bias type SMA actuator is studied, through the comparison of theoretical simulation and experiment, the reliability of driver model is verified. Third, the dynamic model of SMA wire actuator is derived based on Brinson’s model and two types of inputs are used to produce different displacements. Then, PID control strategy for the SMA actuators is established and implemented to active control the position. Through the comparison of different amplitudes and frequencies of current inputs, the different control abilities and characteristics to acquire the maximal displacement can be approximately achieved. Significantly, the position can basically remain stable. The results demonstrate the SMA wire actuators can be used to stably control the displacement of the adaptive beam.In chapter5, the major research work is elaborated. In addition, combining the SMA actuator control strategy research, future development is predicted in order to provide references for the future research on this project.