| Shock wave pressure is an important index to evaluate the explosive performance of the ammunition.The pressure amplitude of the shock wave signal is high,the frequency component is rich,and the explosion field environment is complex,which makes the measurement of the shock wave pressure difficult.There are some problems in shock wave pressure measurement,such as uncertainty,incomparability and inability to trace the source.Accurate measurement of the shock wave pressure can improve the accuracy of the damage power assessment,which has important engineering application significance for the national defense construction and the national economy construction.The commonly used shock wave pressure measurement method is the electrical measurement.Considering the complexity of the explosion field,the piezoelectric shock wave pressure measurement system is often chosen.Because of the parasitic effects of high heat,strong shock and vibration in the explosion field,the shock wave pressure measurement system outputs the parasitic response.In order to suppress the parasitic effect,the sensor needs to be modified,which will inevitably cause the change of the operating parameters and transmission characteristics of the shock wave pressure measurement system.In addition,different cable lengths,repeated use of sensors and other factors will also introduce measurement errors.Therefore,the shock wave pressure measurement system needs to be calibrated,of which the calibration band should cover the effective bandwidth 0?100k Hz of the shock wave pressure signal,which is called the broadband calibration in this paper.However,the existing calibration devices are unable to achieve the so-called broadband calibration.Through theoretical analysis,experimental research and verification,this paper studied the method of broadband calibration,dynamic modeling and compensation,and uncertainty evaluation of engineering measurement for the modified piezoelectric shockwave surface reflection pressure measurement system.The main research contents are as follows:(1)A combined calibration method for the shock wave pressure measurement system was proposed.Based on quasi-static calibration,the operating characteristic parameters and the lowfrequency transmission characteristics of the shock wave pressure measurement system of0?1k Hz can be obtained.Based on the dynamic calibration of the shock tube,the transmission characteristics of the medium and high frequency band above 1k Hz can be obtained.Therefore,the combined calibration can realize the broadband calibration of the shock wave pressure measurement system.Based on the combined calibration,dynamic modeling and compensation of the shock wave pressure measurement system is needed to achieve the non-distortion measurement in engineering,which proves the necessity of dynamic modeling and compensation,and is of great significance to improve the accuracy of shock wave pressure measurement.(2)Combined calibration experiments were conducted on typical shock wave pressure measurement systems.For three typical shock wave pressure measurement systems in the ranges of 0?7MPa and 0?50MPa,firstly,based on the drop hammer hydraulic device,the lowfrequency band of 0?1k Hz was calibrated by the comparison quasi-static calibration.The standard pressure monitoring systems were set up and the uncertainty evaluation method of the standard pressure monitoring was studied.The quantity value transfer path of the quasi-static calibration was analyzed,and the traceability of the combined calibration results was proved.Secondly,based on the double-membrane shock tube,the dynamic calibration of the typical shock wave pressure measurement systems in the middle and high frequency band above 1k Hz was carried out.In view of the influence of the structure to suppress the parasitic effects on transmission characteristics,the difference of transmission characteristics of sensors from different manufacturers,and the difference of repeated dynamic calibration results,dynamic calibration experiments were designed respectively.Finally,in view of the problem that the piezoelectric pressure measurement system is not suitable for static calibration,a method for calculating the working characteristics of the shock wave pressure measurement system based on the quasi-static calibration was proposed,and the working characteristic curve and the sensitivity,the linearity,the repeatability of typical shock wave pressure measurement systems were obtained.The combined calibration has realized the broadband calibration and the calculation of the working characteristics of the shock wave pressure measurement system and laid a foundation for dynamic modeling and compensation.(3)Based on the combined calibration experiments,the transmission characteristics of the typical shock wave pressure measurement system were studied.Through qualitative analysis of the non-parametric model of transmission characteristics of the low-frequency band of 0?1k Hz and the medium and high frequency band above 1k Hz of shockwave pressure measurement systems,it was proved that the typical shockwave pressure measurement systems had good low-frequency characteristics,while the medium and high frequency characteristics cannot meet the condition of engineering measurement without distortion.In order to quantitatively analyze the transmission characteristics of shock wave pressure measurement system and further study its parameter model,a local(within 100 k Hz)parameter modeling method was proposed.The generalized least square method with special whitening filter(GLS(SF))was more fast,convenient,realieable and optimized for shock wave pressure measurement system,and the local parameter model of typical shock wave pressure measurement systems were established.Compared with the global modeling,the local modeling method can improve the efficiency and the accuracy of modeling.The analysis of transfer characteristics is the judgment basis of whether the shock wave pressure measurement system needs dynamic compensation,which is of great significance to improve the accuracy of the shock wave pressure measurement.(4)Based on the local parameter model of the transmission characteristics of the shockwave pressure measurement system,the local dynamic compensation of the shockwave pressure measurement system was studied.The effects and applicability of zero-pole elimination method and BP neural network method for dynamic compensation of the shock wave pressure measurement system were compared.For the shock wave pressure measurement system,the zero-pole elimination method was more fast,convenient,realieable and preferred.Then the dynamic compensation was made for the typical shock wave pressure measurement systems.The effectiveness of the zero-pole elimination method was verified,and the universality of the method was proved.The dynamic compensation was applied to the typical shock wave pressure signal,and the pressure peak error before and after compensation was about 10%,which indicated that the dynamic compensation is of great significance to improve the accuracy of shock wave pressure measurement and is an essential link.Through the zeropole elimination method,the engineering measurement without distortion of typical shock wave pressure measurement systems were realized,and the accuracy of shock wave pressure measurement was guaranteed.(5)In order to quantitatively evaluate the accuracy of shock wave pressure measurement,the evaluation method of the engineering measurement uncertainty of the shock wave pressure was studied.Firstly,according to the static and quasi-static calibration experiments,the uncertainty component of the instrument performance was obtained.The uncertainty component of parasitic effects was evaluated by the thermal simulation and the impact loading experiment.Through theoretical calculation,the uncertainty component of engineering installation was obtained.Based on the grey method,the evaluation method of dynamic calibration uncertainty component was proposed.Then,by synthesizing the uncertainty components,the engineering measurement uncertainty of the shock wave pressure was obtained.Finally,the corresponding measures to further control the uncertainty and improve the measurement accuracy were put forward.In the typical engineering measurement uncertainty of the shock wave pressure,the dynamic calibration uncertainty component had the largest influence,followed by the parasitic effects and the engineering installation component,and the instrument performance component was the smallest.The typical engineering measurement uncertainty with a double expansion of the shock wave pressure was 9.8%,which meets the requirement of 8%?10% of the shock wave pressure measurement,which is of great significance for accurately evaluating the damage power of the shock wave. |
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