Development Of Low Frequency Shock Spectrum Measuring Device And Study Of Response Spectrum Correction Method

The traditional piezoelectric acceleration sensor is measure the acceleration load of the base,the calculated shock response spectrum is the standard for the anti-shock design,evaluation,examination of ships and shipborne equipment.However,the acceleration signals measured under strong shock conditions is mixed with strong low-frequency trend term errors,resulting in zero drift phenomenon in the low spectrum values of the calculate shock response spectrum,which is1～2 orders of magnitude higher than the real value.Therefore,the calculate shock response spectrum must be modified to restore the real shock environment.In this paper,on the basis of studying the filtering algorithm of the relevant acceleration trend term,the measuring device of the medium and low frequency shock environment,a new measuring device of the shock spectrum based on the spring-mass-damping system is developed to measure the spectrum value of the medium and low frequency of the shock response spectrum.It provides a reference for the error filtering algorithm of the related acceleration trend term and the correction of the shock response spectrum.In order to verify the feasibility of the shock spectrum measurement device,the relevant characteristics of the shock response spectrum were firstly studied.The motion differential equation and finite element model of the shock spectrum measuring device were established,the shock responses with the same natural frequency which different damping ratios were calculated.The shock characteristics of the preloaded plate spring structure in the measuring system were studied,the natural frequency of the plate spring was calculated,the finite element model of the plate spring was established.Finite element shock simulation was carried out to verify the feasibility of the shock spectrum measurement device under the shock condition,which is of guiding significance to the development of other spring.It is of guiding significance to the development of other spring.According to the theoretical calculation and simulation calculation results of the shock spectrum measuring device,the principle prototypes of single and double spring shock spectrum measuring devices were developed.The feasibility and accuracy of the measuring device were verified by shock tests on the prototype under transverse,axial and complex environment conditions.experimental results showed that the damping ratio of the two shock spectrum measuring devices were very small,the influence on the measurement results were less than 4.2%,the difference between the prototype and the designed natural frequency was very small,which meets the design requirements.Taking the data measured by the shock spectrum measuring device as the basis for the correction of the mid-low frequency shock spectrum,"wavelet transform","empirical mode decomposition" and "least square method" are respectively used to process the low frequency trend term error in the shock signal.And the shock response spectrum is plotted.The modified middle and low spectrum lines are highly correlated with the equivalent displacement curve fitted by the shock spectrum measuring device,and the spectrum lines return to the low-frequency equivalent displacement position.After comparison,the empirical mode decomposition method has high adaptive degree and ideal correction effect.Based on the calculation,simulation and test results of the shock spectrum measuring device,it is concluded that the shock spectrum measuring device can accurately measure the low and medium frequency shock environment,which provides a basis for the correction of relevant theoretical algorithms,reduces the influence of human factors,and improves the correction accuracy of the low and medium frequency of the shock response spectrum.