Trajectory Detection For An Earth Penetrator In Soil

In today’s world, large-scale wars no longer exist, but local conflicts still occur. Many countries have hidden a lot of important military facilities in deep underground, because the military targets on the ground can been easily detected and combated, then, earth penetrator has become an important weapon to attack underground military targets. Earth penetrator is a kind of warhead that penetrating into the underground defense projects and destroying targets underground. It can be used to destroy military bases reinforced on the ground, surface high-level targets, deep underground military and important civilian facilities.The research of earth penetrators can be divided into theoretical research and outfield experimental research. In the outfield experiment, the dynamic parameters of earth penetrators’ penetrating progress such as fuze, overload response of the bomb and the track of earth penetrator can be recorded by electronic memory in the bomb and obtained by recycled after the experiment. But the recycling of built-in electronic recorder needs to detect the projectile trajectory, and the electronic memory in the bomb may have effect on the penetration process, or it is forbidden to use built-in recording apparatus, so it’s very important to monitor the penetration trajectory of earth penetrators in the experiment(such as the experiment of the real bomb).After analyzing the seismic wave effects on the targets when earth penetrator penetrates, this paper treats the earth penetrator surveillance as a special seismic exploration technology. Firstly, in the process of penetration, the earth penetrator surveillance is regarded as the moving sources passive ranging, and TDOA is chosen as the basic method for the path calculation of earth penetrator. According to the distribution of detectors of test model, for estimating the time difference of TDOA, a method of local direct cross-correlation is put forward. Because the velocity is unknown during the process of penetration, a method for estimating relative time difference is designed. Then, for estimating the frequency difference, the method of frequency energy analysis with HHT is given and it proves to be a high-precision FDOA positioning method. Next, in view of the characteristics of seismic waves in time domain and frequency domain, a method of positioning with serial TDOA/FDOA and a method of positioning with parallel TDOA/FDOA are put forward. The analysis result indicates that these two methods are practical in the calculation of the path of earth penetrator.This paper starts to improve the positioning precision of these methods above such as processing noise-suppressed to seismic signal, extracting high precision time difference and frequency difference signal.Finally, the paper estimates the merits and gets the applicable conditions of TDOA, FDOA, serial TDOA/FDOA and parallel TDOA/FDOA positioning algorithm by processing and analyzing experimental data. The result shows that these methods can be used to positioning the trajectory of earth penetrators effectively.