Precise Driving Method And Experimental Research Of Wire-Type Shape Memory Alloy Vehicle-Mounted Actuator

With the development of science and technology,proposed the development direction of electrification,light weight,and intelligence was proposed by the automobile industry.However,the disadvantages of traditional electromagnetic actuators on the car body such as quality,volume,and noise have become increasingly prominent,which are not contrary to the future development of the automobile industry.Because of its unique shape memory effect,shape memory alloys have been widely used in various engineering fields.The actuators using shape memory alloy materials as actuators have the advantages of small structure,no impact noise,no electromagnetic interference,etc.,which can be used to replace traditional electromagnetic actuators in automobiles to solve the shortcomings,so that they have good prospects for development.Shape memory alloy(SMA)has special properties such as shape memory effect,super elasticity,stiffness,and resistance,which enable it to complete more work requirements than ordinary metals.The wire-type SMA material can undergo a phase change by heating when it is in a low temperature.The macroscopic expression is that the length is shortened,and at the same time a large displacement and stress are applied to the outside.The SMA actuator has a fast response speed and a large output force.No noise and other advantages,through a certain control method,it can complete the displacement output work at any specified position,and at the same time provide more research foundations and ideas for future new SMA actuators.In this paper,a certain theoretical analysis is made on the basic characteristics of the SMA material.The actuator prototype is made in combination with the material characteristics.The control method is researched according to the performance of the prototype.The main research contents are as follows: the principle analysis of the known main properties of the SMA material combined with the material structure was carried out,and a static tensile experiment was carried out,including the maximum recoverable strain,strain amplitude,strain rate,and the influence of temperature on the SMA material.The relative mechanical performance parameters of the wire SMA of the actuator element provide a theoretical basis for subsequent simulation calculations.The SMA constitutive model theory is explained from the perspective of numerical simulation,and based on the material constitutive model of SMA which combined with the material elastic modulus,critical stress,phase transition temperature and other parameters obtained from the experiment,a numerical model of the two-way motion of the SMA actuator is established.In the aspect,the double-wire pair-pull structure is used to design and produce the SMA actuator prototype.Obtain the data of the SMA actuator’s reciprocating motion process at the specified temperature through the actual machine test,and compare it with the simulation calculation of the constitutive model to ensure the consistency of the model establishment and the actuator prototype,and obtain the different actuators through different current excitations.The output response under input and the obtainment of relevant experimental data provide a numerical basis for the study of the precise driving method of the actuator.Using programmable control power supply,linear displacement sensor,NI acquisition card and other experimental equipment,combined with PC software to conduct control experiments on the SMA actuator prototype,according to the relevant experimental data of the actuator prototype combined with modern control theory,three control methods are proposed.The SMA actuator prototype is used for precise control experiment and control effect comparison,including self-adjusting control method based on current characteristics,dual-channel PID self-adjusting control method,and fuzzy control method based on proportional gain.After the experiment,obtain the influence law of the control parameters on the control effect,and further optimize the control method.Finally,three target signals of fixed-point output,sine output,and step output are used to conduct control effect experiments on the three control methods.The experimental results show that the three control methods have good performance under fixed-point output conditions,the fuzzy control method performs best under step output conditions,and the robustness and rapidity of PID control under sine output conditions are both Stronger.Compared with mainstream control methods,the self-adjusting control method based on current characteristics is not universal and robust,but it is more targeted for the actual machine in the process of this research;PID control can perform real-time response to the system Judgment,with strong robustness and accuracy;fuzzy control is more stable and universal than the first two control methods compared to the first two control methods,and the effect is compared with the other two when the target signal change rate is low.This method is particularly prominent.The three control methods have good performance under the working conditions in this study,which overcomes the slow recovery speed of SMA and the difficulty of precise positioning.In terms of variance value,PID control tracking performance is the best under both sine and step conditions.The performance of self-adjustment method is slightly worse under step conditions,and the tracking ability of fuzzy control method is moderate.However,from the actual curve,the disadvantage of the self-adjusting method is that it is difficult to handle high-frequency changing conditions.This method has the best stability in fixed-point output capability.The other two methods have different degrees of overshoot and fluctuation。The study proves the potential and feasibility of SMA material as a new type of actuator.