Research On Characteristic Modeling And Resistance Sensing Control Of Shape Memory Alloy Actuators

With the development of smart materials,shape memory alloys(SMAs)with their unique shape memory effect(SME)and superelasticity(SE)have become more and more widely used in aerospace,automotive,medical equipment,etc.Through investigation and comparison,it is found that the current SMA application still has insufficient exploration of the relat ionship between theory,control and practical application,which limits the application of SMAs.In order to overcome these problems,the characteristics of SMA actuators are modeled,and a control strategy of one-dimension SMA actuators based on resistance feedback control is proposed in this paper.In order to describe the thermodynamic behavior of the shape memory alloy more effectively and accurately,a novel variable speed constitutive model of SMAs is established.The crystal variable speed function K and the crystal variable speed coefficient k is introduced to describe the phase transformation process of SMA in the new model,and the constitutive equation is established based on the decomposition of the strain of SMA.An experiment system is designed to test the thermodynamic properties of SMAs,including DSC test,loading experiments at different temperatures and Thermal cycling experiments.The experiment results are processed by using the new data processing method and the traditional tangent processing method,and the material parameters are obtained.Numerical simulations are performed by using the variable speed constitutive model and the conventional Brinson model,respectively.The results are compared with the experimental results,and the acc uracy and effectiveness of the variable speed constitutive model are verified.In order to make the resistance of the SMA wire an effective feedback signal and realize resistance feedback control,the relationship between resistance-forcetemperature is established,combining the variable speed constitutive model of SMAs and resistance characteristics of metal materials.By studying the principle of electrothermal driving,the three-dimensional coupling relationship of current-temperature-time is established.A control strategy is designed for SMA wire-constant load system,including feedforward design based on the variable speed constitutive model and the electrothermal driving principle,variable parameter PID feedback design and resistance feedback cont rol design based on the resistance characteristic model.A corresponding control system of one-dimension SMA actuators and a test system for testing the precision driving performance of SMA actuators are designed.In a single-wire system,the feedforward control,displacement feedback control and resistance feedback control are simulated and analyzed respectively,and three typical signals are tracked.Compared with the traditional PID controller,the control performance of the controller is verified.In the two-wires system,changing the ambient temperature and load conditions,the synchronous performance control of the SMA under different conditions is simulated,and the simulation results are analyzed.The synchronous control performance of the system is verified,and the accuracy of synchronous control is determined.The research results indicate that the proposed control strategy based on resistance feedback has excellent control performance.