| Dynamic pressure measurement is widely used in the performance evaluation of weapon system,such as the gunpowder gas pressure measurement in gun bore,the explosion shock wave pressure measurement of all kinds of ammunition,etc.Piezoelectric sensors have excellent dynamic characteristics,so for these dynamic pressure test objects,piezoelectric pressure electrical measurement system is widely used at present.However,due to the poor low frequency characteristics of the piezoelectric pressure electrical measurement system,static calibration is not suitable;in addition,for the corresponding piezoelectric pressure electrical measurement systems of different test objects,the installation mode of sensors,the test environment and the waveform characteristics of measured pressure are all different.Therefore,in order to improve calibration efficiency and calibration accuracy,it is necessary to develop suitable calibration devices,study the corresponding quasi-static and dynamic pressure calibration technology,and put forward the corresponding operating characteristic parameters and dynamic transfer characteristics calculation methods according to the characteristics of the actual test objects.In addition,the measurement uncertainty is an important index to evaluate the test results of the pressure electrical measurement system.The time-domain transient characteristics of dynamic pressure make the original static measurement uncertainty evaluation method can not completely and reasonably reflect the quality of dynamic measurement results.Therefore,it is necessary to carry out the research on the evaluation technology of measurement uncertainty of piezoelectric pressure electrical measurement system under the condition of quasi-static calibration and dynamic calibration.Based on the above considerations,this paper uses dynamic modeling theory,BP neural network,genetic algorithm,grey theory and finite element simulation to study the calibration technology,operating characteristic parameters calculation method,dynamic correction method and measurement uncertainty evaluation method of three typical piezoelectric pressure electrical measurement systems such as gunpowder gas pressure,air shock wave pressure and underwater shock wave pressure.The main work of this paper is as follows:(1)Aiming at the problems that the low frequency characteristic of the measurement system is not good and the static calibration method is not suitable,a comparison quasi-static calibration method based on drop-weight device is studied.The circuit characteristics of piezoelectric pressure electrical are analyzed,which provides theoretical basis for the effectiveness of quasi-static calibration method in reducing charge leakage and restraining output drift.The working principle of the drop-weight device and comparison quasi-static calibration method are introduced,the standard pressure monitoring system is established and calibrated in different pressure ranges.The value transfer result shows that the standard pressure monitoring system has high measurement accuracy in the high and low pressure ranges.Through the comparison quasi-static calibration experiment,the sensitivity,linearity and repeatability of the calibrated pressure electrical measurement system are obtained,and the feasibility of the operating characteristic parameters calculation method is verified.(2)In view of the high cost of the standard pressure monitoring system and the low efficiency of the calibration experiment existing in the traditional comparison quasi-static calibration method,a parameter configuration method of the calibration device and a quasi-static calibration method of the pressure electrical measurement system based on the artificial neural network optimized by genetic algorithm are proposed.By training the quasi-static calibration experiment sample data,the mathematical model between the working parameters of the drop-weight device and the generated peak pressure and pulse width is established.The prediction errors of peak pressure and pulse width of the mathematical model are lower than 0.7 % and 0.2 % respectively.Based on the prediction model of GABP neural network,the operating characteristic parameters of the calibrated pressure electrical measurement system are obtained.The calibration results are similar to the traditional quasi-static calibration method,which verifies the feasibility of this calibration method.(3)In view of the shortcomings of the traditional calibration method and the calibration method based on GABP neural network,an absolute quasi-static calibration method based on the self-developed force sensor is studied.The influence of pretightening force,inertia force and natural frequency reduction caused by the installation and connection mode on the measurement of force value is analyzed.A high-precision strain-gauge-type force sensor is developed by using the hammerhead structure of the existing drop-weight device as the elastic sensing element.Through theoretical research,simulation analysis and static and dynamic calibration experiments,it is verified that the mechanical strength,bending strength and static and dynamic characteristics of the force sensor all meet the requirements of quasi-static calibration.By analyzing the factors that affect the pressure calibration accuracy,the relationship model between force and pressure is studied,and the corresponding peak pressure correction method is proposed.The calculation error between the corrected and the reference peak pressure is less than 0.7 %.Based on the absolute calibration method,the operating characteristic parameters of the calibrated pressure electrical measurement system are obtained,and the calibration results are very similar to those obtained by the previous calibration methods,which verifies the feasibility of this calibration method.(4)Aiming at the problems of dynamic calibration of air and underwater shock wave pressure electrical measurement system,the dynamic calibration and dynamic compensation methods based on air shock tube and pre-pressure water shock tube are studied.Through the finite element simulation,the propagation rule of underwater shock wave pressure,the formation rule of plane wave in water shock tube,and the influence of the length of water shock tube cavity,the static pre-pressure value and the explosive mass on the shock wave pressure are analyzed.The standard and calibrated pressure electrical measurement systems are established.Based on the air shock tube and the pre-pressure water shock tube,the dynamic pressure calibration experiment is carried out,and the dynamic transmission characteristics of the calibrated pressure electrical measurement system are calculated.Based on the generalized least square method with special whitening filter,the mathematical model of the transfer function of the calibrated pressure electrical measurement system is identified,and the corresponding dynamic compensation measures are taken.After compensation,the dynamic characteristics of the calibrated system are improved,and the dynamic errors are obviously reduced.(5)In order to solve the measurement uncertainty evaluation problem of three different quasi-static pressure calibration methods based on comparison,GABP model and force sensor,the influence factors of measurement uncertainty of the reference pressure value and the calibrated pressure electrical measurement system are analyzed,and the measurement uncertainty is calculated based on the traditional GUM method,Monte Carlo method and uncertainty propagation rule.Aiming at the phenomenon of "using static method to evaluate dynamic uncertainty" and the problem of small sample measurement in the uncertainty evaluation of piezoelectric pressure measurement system,a dynamic measurement uncertainty evaluation method in full range and full frequency based on grey theory and neural network algorithm is proposed,and the dynamic measurement uncertainty of typical air and underwater shock wave pressure measurement system is evaluated by this method. |
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