Parameter Identification Of Critical Scale Particle Deposition In Lunar Soil Based On Penetration Method

China's Chang'e-5 lunar probe uses drilling method to sample the lunar subsurface soil,and the critical scale particles widely distributed in the subsurface are easily accumulated under the bit during drilling,which has adverse effects on drilling,such as worsening of the bit,reducing the heart rate,sticking,jumping and other failure conditions,leading to the failure of the lunar sampling mission.When this kind of working condition occurs,its load parameters are similar to those of rock plugging drilling.It can not be accurately identified only by rotary load parameters.It can only be stopped by identifying the drilling mode of percussive drilling and solved by pertinent drilling conditions in order to avoid adverse effects on sampling drilling tasks.Based on the virtual soil pile theory,the interaction model between drill pipe and lunar soil under impact(penetration mode)is established.The strict analytical solutions of frequency domain response of top displacement of drill pipe and frequency domain response of top velocity of drill pipe under arbitrary load are obtained in frequency domain by using the method of separation of variables.The effects of the measured parameters on the frequency domain response of the top of the drill pipe and the frequency domain response of the top speed of the drill pipe when the parameters of the drill pipe change under three typical working conditions are analyzed.Simulated impact tests were carried out under three typical working conditions and data were collected.Spectrum and power spectrum were obtained based on fast Fourier transform processing data.Frequency spectrum analysis was used to compare the theoretical and single impact test results.The theoretical curves of frequency domain response of drill pipe top velocity under three working conditions were consistent with the experimental results,which verified the feasibility and accuracy of the theory.Through the analysis of the physical law of the peak points on the power spectrum of the test results through multiple impact tests,the characteristic index of frequency value which can effectively characterize the working conditions is selected.It is found that the peak points of power spectral density amplitude show certain regularity when simulating the critical scale particle accumulation condition,which are different from the homogeneous simulated lunar soil and simulated lunar rock conditions.The peak points vary with the impact frequency,and the peak points are different from the homogeneous simulated lunar soil and simulated lunar rock conditions.With the increase of impact frequency,the number of peak points of power spectral density amplitude gradually decreases until a single peak appears.Several impact tests were carried out to analyze the effects of thickness and density of the critical scale particle accumulation layer on frequency domain response characteristics of drill pipe top velocity.Frequency characteristics which effectively characterize the accumulation condition were extracted as identification features to identify the critical scale particle accumulation condition.In this paper,a method of identification based on feedback parameters of drilling tools is proposed by using cone penetration method.The signal characteristics of drilling tools are extracted when they encounter different drilled objects.The type of drilled objects is identified effectively,and the limit conditions caused by critical scale accumulation are identified.The identification of the parameters of the critical scale particle accumulation condition is studied,which complements the blank of the method for identifying the drilling state fault caused by the bad replacement of the critical scale particle,and provides the theoretical basis for the reliability of the lunar drilling sampling and the drilling coring efficiency in China.