Research On Electromechanical Coupling Characteristics Of Piezoelectric Vehicle Crash Sensor

The piezoelectric impact sensor can use the piezoelectric effect of the piezoelectric material to convert the acceleration signal of the measured object into an electric signal.It has the advantages of simple structure,high sensitivity,high signal-to-noise ratio,and no need for external power supply.It is an important part of automotive airbag system.Generally,a piezoelectric impact sensor is composed of piezoelectric ceramics,an insulating material,and an elastic substrate sequentially connected to form a sealed structure.The multilayer composite structure will produce a complex electromechanical coupling transformation process under the action of inertial load.Therefore,in order to realize the design of high-precision piezoelectric impact sensor,it is necessary to establish an accurate electromechanical coupling system analysis model.In the current research,the backward coupling force of the self-induced electric field generated by the piezoelectric effect on the sensor is ignored,which makes it difficult for the corresponding model to accurately predict the dynamic characteristics of the sensor.In order to solve the above problems,this paper makes relevant researches based on the electromechanical coupling characteristics of the compression piezoelectric impact sensor.The specific work is as follows:(1)The eight-degree-of-freedom equivalent dynamic model of the piezoelectric compression impact sensor is established,the SIMULINK numerical simulation model is built using the state-space equation method,and the fourth-order Runge-Kutta algorithm is used to calculate the eight-degree-of-freedom equivalent dynamic model.The response under half-sine pulse excitation is consistent with the finite element simulation;(2)The electromechanical coupling theoretical model of the piezoelectric impact sensor considering the piezoelectric ceramic self-induced electric field is established.The dynamic response and charge sensitivity of the sensor under the impact load are calculated.Compared with the finite element simulation results,it is shown that when the self-induced electric field is not considered,the theoretical and simulation errors of charge sensitivity corresponding to the first,middle and last three voltage peaks are 65.68%,15.42%,and 30.42% in sequence;when the self-induced electric field is considered,the theoretical and simulation errors of charge sensitivity corresponding to the first,middle and last three voltage peaks are 10.88%,7.71%,0.32% in sequence,the calculation accuracy is significantly improved compared with the model that does not consider the influence of the self-induction electric field,which verifies the accuracy of the established piezoelectric sensor analysis model considering the self-induction electric field;(3)The factors that affect the charge sensitivity of the sensor is analyzed systematically.The charge sensitivity has nothing to do with the magnitude of the impact load,and the sensor performance is stable;it is related to the load action time.The closer the external load action time conversion frequency is to the natural frequency of the sensor,the higher the corresponding charge sensitivity,but the resonance phenomenon affects the service life of the sensor.Under an impact load with an amplitude of 8000 g and an action time of 10 μs,when the piezoelectric material is PZT-5H and the thickness is 0.5mm,the charge sensitivity is the highest.