| At present,there are more than 200 movable parts that need to be driven in automobiles.With the continuous pursuit of intelligent vehicles,this number will continue to increase,and cars are increasingly becoming a aggregation of driving structures.The flexible driver using shape memory alloy(SMA)as the driving component can overcome the shortcomings of the traditional driver structure,such as heavy structure and large impact noise.Today,with more and more attention to cost,space and comfort,the research and application of SMA flexible actuators have very good development prospects.Using the shape memory effect(SME)of SMA,SMA can be used as a drive element for driving structures.The resistance of SMA is relatively large,so the actuator can be operated by direct electric heating,which has the advantages of convenient driving and simple control.The external flexible support with multiple degrees of freedom and arbitrarily adjustable shape enables the driving structure to have any shape.It is arranged in a small space on the car to facilitate miniaturization and weight reduction of the structure.In this paper,the theoretical analysis and experimental research on the driving characteristics of SMA wire are carried out.Based on this,SMA wire is used as the driving component,and an offset double-pass flexible driver with tension spring is designed and driven.Theoretical and experimental research,the main work content and results of the thesis are:(1)The mechanical and thermodynamic static tensile tests of SMA wire under different experimental conditions were carried out to obtain the material properties of SMA wire,and the material parameters were provided for the subsequent theoretical analysis and finite element simulation,and different experimental conditions were obtained for SMA wire.The influence of the driving characteristics.(2)Experimental study on the driving characteristics of SMA wire under different loads,the influence law of the driving characteristics of SMA wire under different constant load and different stiffness bias springs is obtained,including the action amplitude,strength and driving speed.And the law of influence of driving power.The results show that the return time of the driver under constant load needs about 17 s,and the return time of the driver is only 8s under the action of the biasing spring.Therefore,the dual-pass flexible actuator under the bias spring is selected as the research focus.(3)According to the Brison and Turner models,the model of the offset two-way driver after the SMA wire is connected with the spring is established.The model is calculated and the driving strain under the action of the spring is obtained,and compared with the experimental results,the model is verified.accuracy.A flexible actuator was designed.The dimensions of the actuator were theoretically calculated and the flexible support was designed.The thermodynamic model of the SMA wire heating and heat dissipation process was established.The calculation results of the model were compared with the experimental results to verify the thermodynamics.The validity of the model.(4)Using the 3D printer to fabricate the designed driver prototype,the driving performance of the driver was experimentally studied,and the driving characteristics of the driver under different currents,different spring stiffnesses and bending curvatures of different flexible tubes were tested.The experimental results show that the designed driver has flexible external support,and the bending curvature of the flexible tube has little influence on the driving characteristics of the driver.Therefore,the designed flexible actuator can be applied to the micro space in the automobile in any shape.At 1.5A current intensity,a fast drive of 0.43 s is achieved.The bias spring not only provides a biasing force for the SMA wire after heating,but also enables the drive to achieve multiple cycles of two-way drive,which overcomes the disadvantages of slow driving speed and long response time,the feasibility of the flexible actuator is verified. |
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