Research On Low Frequency Characteristics And Compensation Methods Of Shock Wave Test System

Shock wave is the main product in the explosion field.Its characteristic parameters,such as overpressure peak value,positive pressure action time and specific impulse,are important parameters for damage effectiveness evaluation.Most scholars study the high frequency characteristics of the test system to improve the accuracy of peak measurement for the purpose of broadening the bandwidth.The low frequency characteristics that affect the positive pressure action time and specific impulse are often ignored.In order to obtain the low frequency characteristic of shock wave test system,the measured shock wave signal is studied by using HHT marginal spectrum analysis method.Through simulation analysis of high-pass filter with different cut-off frequencies below100 Hz for ideal shock wave signal,the influence of low-frequency characteristics of the system on shock wave signal is further verified.The results show that the low frequency characteristic of shock wave measurement system is the main factor affecting the positive pressure action time and specific impulse.Aiming at the poor low frequency of the shock wave test system,the first-order low frequency model and the high-order system model of the test system were established through two methods of mechanism modeling and system identification.The low frequency compensation model of the test system was established by using the pole-zero configuration method.The two methods are as follows:The first method is mechanism modeling compensation method.Firstly,through analyzing the electrical principle of the test system,the main reasons affecting the low-frequency characteristics of the test system are obtained.Based on the electrical principle,the first-order low frequency model of the test system was established,and the low frequencycompensation test plan of the shock wave test system was determined by using the shock tube as the calibration source.The low frequency model parameters of seven types of test system were obtained by shock tube test.After the low frequency model was established,the low frequency compensation model was established by using the pole-zero configuration method.The second method is system identification modeling compensation,which regards the test system as a "black box" and selects a test system in the shock tube test.Firstly,the optimal order of the model is determined by the QR decomposition method,and then the7-order model of the test system is established by the system identification method in the Matlab environment.According to the pole-zero distribution,the 7-order model was divided into four subsystem models.Through the step-simulation experiments on the subsystems,the subsystems that affect the low frequency characteristics of the test system was established.Finally,the low frequency compensation model was established by the pole-zero configuration method.The low frequency compensation model established by the two methods was applied to the shock tube experimental data for compensation verification,then it compared with the standard piezoresistive system,and the correlation coefficient was analyzed.The results show that the first method is simple and accurate,but it is limited to the low frequency compensation of the test system.The compensation effect of the second method is slightly lower than that of the first method,but it can compensate the high frequency characteristics as well as the low frequency compensation of the test system.Finally,two compensation models were applied to the static explosion test,and the results show that the data processing method based on low frequency characteristics compensation can effectively improve the test accuracy of the positive pressure action time and specific impulse of the shock wave signal.