RU2165629C1 - Method of detection of moving objects on line protected - Google Patents

Abstract

FIELD: protection of sections of terrain and approaches to them. SUBSTANCE: seismic signal is recorded in several preset frequency bands and spectral of recorded seismic signals are determined. Then analysis of high-frequency and low-frequency components of seismic signal spectrum is conducted. Change in relationship of high- frequency and low-frequency components of spectrum is indicative of approach or departure of moving object. EFFECT: enhanced informativeness. 1 dwg

Description

 The invention relates to technical means of protection and can be used to protect sections of the terrain and approaches to objects.

 Known similar methods for detecting violations of the guarded line, which include analyzing the frequency spectrum of seismic signals generated by the intruder object, which are implemented in the detection tools PS-75C [1], "Snowdrop" [2].

 In the PS-75C detection tool, a seismic signal is received by electrodynamic geophones, amplified, filtered in the band of 20 - 40 Hz, detected and processed by subsequent circuits.

 In the Snowdrop detection tool, a seismic signal is received by an electrodynamic seismic receiver, amplified by a resonant amplifier with a tuning frequency of 30 Hz, then filtered in a band of 25-35 Hz and processed further.

 In both cases, the decision on violation is made by a threshold device based on an energy feature.

 The disadvantage of such methods is the low information content of the results: there is a violation - there is no violation.

 Closest to the proposed one is a method for detecting seismic signals, filtering them in a certain frequency band and making a decision on the energy basis, implemented in the PS-75C detection tool.

 The aim of the present invention is to increase the information content of the method for detecting violations of the guarded line by obtaining the possibility of separation of signals according to the signs: "approaching object", "retreating object", "stationary source".

где r - расстояние от точки расположения источника сейсмического до точки приема;
n - коэффициент, зависящий от типа волны¹;
e^-α(ω)r - множитель ослабления волны;
α(ω) - характеристика среды, возрастающая с ростом ω² [3].This goal is achieved by the fact that in soils with increasing distance from the observation point, the high-frequency components of the spectrum of the seismic signal undergo a stronger absorption than low-frequency ones [3]. The frequency response of the soil can be represented as:

where r is the distance from the point of location of the seismic source to the point of reception;
n is a coefficient depending on the type of wave ¹ ;
e ^{-α (ω) r} is the wave attenuation factor;
α (ω) is the characteristic of the medium, increasing with increasing ω ² [3].

¹ Longitudinal, transverse, and Rayleigh waves. For S and P waves, n = 1, for R waves n = 0.5, for PS waves n = 2.

² For most soils, the relationship is linear or quadratic.

 The method is implemented as follows. The spectrum of the seismic signal is monitored in several frequency bands (the most characteristic of the detected object: a person, a vehicle ...) and, depending on the dynamics of changes in the ratio of spectral densities, a decision is made on the presence and nature of violation of the guarded line.

 The drawing illustrates a variant of the practical implementation of the proposed detection method.

 The seismic receiver 1 is affected by a signal. After amplification in amplifier 2, the signal is fed to the inputs of two or more weighing filters with different passbands 3 (15-25 Hz) and 4 (35-50 Hz). From the output of filter 3, the signals go to the input of the integrator 5, and from the output of the filter 4 to the integrator 6. After integration, the signals from the outputs of the integrators 5 and 6 go to the input of the solver 7, which makes a decision according to the level of signals at the outputs of the integrators 5 and 6: "approximation", "removal", "stationary source". In order to save the resource of the power supply, the threshold device 8 and actuator 9 are included in the circuit. The threshold device 8 is activated only when the signal at the output of amplifier 2 exceeds a certain level set at the installation site of the detection means. The triggering of the threshold device 8 triggers the actuation device 9, which provides signal processing that carries useful information. After a certain time, the actuator turns off the processing circuit and the entire device goes into standby mode for the next signal.

 The proposed method for detecting moving objects can increase the information content of seismic detection tools and thereby improve the quality of work of technical security equipment.

Sources of information
1. PS - 75C. Seismic alarm device. Technical description and instruction manual. 1a1.111.006 TO.

 2. Snowdrop. Detection system. : Tutorial. - M .: GUVV Ministry of Internal Affairs of the USSR, 1979. - 176 p.

 3. Gurvich I.I. Bogannik G.N. Seismic Intelligence: A Textbook for High Schools. - 3rd ed., Revised. - M .: Nedra, 1980 .-- 551 p.

Claims (1)

 A method for detecting a moving object at a guarded boundary, including recording and processing a seismic signal generated by an object, characterized in that the seismic signal is recorded in several predetermined frequency bands, the spectra of the registered seismic signals are determined, the high-frequency and low-frequency components of the spectrum of the seismic signal are analyzed, and ratios of high-frequency and low-frequency components of the spectrum judge the approach or removal of a moving object.