RU2175772C1 - Seismic facility for detection of objects - Google Patents

Abstract

FIELD: guarding of perimeters of objects and approaches to objects. SUBSTANCE: seismic facility for detection of objects has seismic converter, signal processing and decision making . circuits, frequency detection channel of received seismic signal. Presence of noise-like signal across output of frequency detector suggests that object is absent. Absence of noise-like signal across output of frequency detector validates presence of object. EFFECT: increased noise immunity of seismic means of detection and reduced number of false operations. 8 dwg

Description

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

 Known devices for the detection and recognition of seismic signals, implemented based on the analysis of the frequency spectrum of the received seismic signals [1, 2], where the decision on the presence of an object and its proposed class is made by the presence of a signal in characteristic frequency bands.

 A seismic signal recognition device [1] contains a seismic receiver in series, an input matching amplifier, a narrow-band filter, an amplitude detector, a comparator, a second narrow-band filter in the range of 70-100 Hz and a second amplitude detector. The first narrow-band filter is tunable in the band 120-240 Hz, the input of the second filter is connected to the output of the matching amplifier, and the output through the second amplitude detector is connected to the control input of the tunable filter. The second narrow-band filter and the second amplitude detector increase the reliability of recognition of seismic signals against interference. The decision on the probable class of the detected object is made by the presence of a signal in the frequency band characteristic of a particular object.

 Closest to the proposed is a seismic device for the detection and classification of objects [2]. The device is designed to detect and recognize moving objects by classes: people, wheeled vehicles, tracked vehicles and aircraft based on the seismic vibrations they create.

 The operation of the device is based on the registration of seismic field disturbances arising as a result of the movement of objects, the identification of classification features in the frequency ranges characteristic of certain classes of objects, the analysis of their quantitative relations and the formation of a decision on the class of the object. The structure of the device [2] includes a seismic transducer, a signal processing circuit, a decision circuit. The signal processing circuit consists of an automatic gain control, a pulse signal extraction and processing unit, seven frequency characteristic extraction channels, a group of comparators. Each channel for selecting frequency features consists of a band-pass filter, an amplitude detector, and an averaging circuit. The decision-making scheme is a logical circuit that forms a signal about the class of the detected object (logical classifier).

 The movement of people and equipment leads to the excitation of seismic vibrations of the soil due to the interaction of the foot of a walking person or elements of the undercarriage of the equipment with the surface layer of the soil. During the passage of motor aircraft, part of the energy of acoustic vibrations when reaching the interface “air - ground” is converted into the energy of seismic waves.

 Seismic waves act on the seismic transducer and electrical vibrations are formed at its output. A seismic signal is the result of a superposition of a useful seismic signal and random interference [3]. The electrical vibrations at the output of the seismic transducer are determined by the nature of the seismic effect, therefore, it is possible to classify the detected seismic signals from the objects to be detected.

 From the output of the seismic transducer, the signal enters the signal processing circuit, where, in seven channels of the identification of frequency characteristics of the same type, filtering is performed by active bandpass filters tuned to different frequency bands, signal detection and averaging. The voltages generated at the outputs of the channels for selecting frequency features are compared with reference voltages using comparators. When the signal at the output of the channel exceeds the frequency characteristics of the threshold voltage at the output of the comparator, a logical unit level is formed.

 The outputs of the comparators of the signal processing circuit are connected to the inputs of the decision circuit, where the decision on the class of the detected object by the seismic detection and classification device [2] is made by the logical classifier according to the presence of signals at the outputs of the comparators, taking into account the sequence of their formation and the temporal characteristics of the pulse effects of seismic signals.

 The disadvantage of such devices [1, 2] is the low noise immunity to the effects of intense seismic random interference.

 Improving the noise immunity of seismic detection and recognition of objects is possible by introducing a frequency channel for processing the seismic signal.

 A seismic background is observed in soils, the characteristics of which in time (amplitude, phase, frequency) have random values (Fig. 1, a) [3]. Therefore, after normalization and frequency detection, a random signal will be present at the output of the frequency detector (Fig. 1, b).

 When a source of seismic disturbances appears in the sensitivity zone of the seismic transducer, the signal at the output of the seismic transducer will have characteristics (phase and frequency) that are close to stationary.

 In FIG. 2a, an implementation of a seismic signal from a stationary tracked vehicle with a running engine is shown, and FIG. 2, b - signal at the output of the frequency detector.

 In FIG. 3a shows the implementation of a seismic signal from a moving tracked object at a speed of 10 km / h at a distance of 100 m from the installation site of the seismic transducer, and FIG. 3, b - signal at the output of the frequency detector.

 In FIG. 4a shows the implementation of a seismic signal from a moving URAL vehicle at a speed of 30 km / h at a distance of 50 m from the installation site of the seismic transducer, and FIG. 4, b - signal at the output of the frequency detector.

 In FIG. 5a shows the implementation of the seismic signal from a moving armored personnel carrier BTR-80 at a speed of 30 km / h at a distance of 50 m from the installation site of the seismic transducer, and in FIG. 5, b - signal at the output of the frequency detector.

 In FIG. 6a shows the implementation of a seismic signal from a moving person at a speed of 5 km / h at a distance of 15 m from the installation site of the seismic transducer, and FIG. 6, b - signal at the output of the frequency detector. In addition, in the structure of the signal at the output of the frequency detector, a pulse sequence corresponding to the sequence of human steps is observed.

 Analysis of the diagrams (Fig. 1-6) allows us to conclude that the phase and frequency of seismic signals from real objects are stationary in case the signal exceeds the noise. In the case of the presence of the detection object at the guarded line at the output of the frequency detection channel, there will be a signal several times smaller than in the absence of the detection object at the guarded line.

 The operation of the device is as follows (Fig. 7). The structurally proposed seismic device for detecting objects consists of a seismic transducer 1, a signal processing circuit 2, a frequency detection channel 3, a decision circuit 4.

 The seismic transducer 1 is designed to receive seismic vibrations and convert them into electrical vibrations.

 The signal processing circuit 2 is intended to highlight the characteristic features of the signals for the purpose of their subsequent classification. It includes in its composition a circuit for automatic gain control, a block for extracting and processing pulse signals, channels for selecting frequency signs, a group of comparators.

 The frequency detection channel 3 (Fig. 8) [4] is intended to form an additional feature for a decision-making scheme on the presence of a detection object in the coverage area of a seismic transducer 1.

 Decision making scheme 4, including a logical classifier, is designed to determine the class of the detected object based on the signals generated at the outputs of the comparators, at the output of the frequency detection channel and at the output of the pulse signal extraction and processing unit.

 The signal from the output of the seismic transducer 1 enters the signal processing circuit 2, where it is normalized by the automatic control circuit and filtered in the frequency bands characteristic of the detected classes of objects. Filtered using band-pass filters, the signals in the seven channels for selecting frequency characteristics are detected and averaged, after which they are compared with reference voltages by comparators. A combination of logic units and zeros will be formed at the outputs of the comparators depending on the signal intensity in the frequency bands to which the bandpass filters are tuned, and on the level of the reference voltage. The signal from the output of the automatic gain control circuit also enters the unit for extracting and processing pulse signals.

 From the output of the seismic transducer, the signal also enters the input of the frequency detection channel, at the output of which there will be a random signal in the absence of an object (exposure to random noise or noise) and the signal will be absent if the object is in the detection zone of the seismic transducer.

 The signals from the outputs of the comparators of the signal processing circuit, from the output of the pulse processing unit of the signal processing circuit, and from the output of the frequency detection channel are fed to the inputs of the decision-making circuit. The decision on the class of the detected object is made by a combination of logical units and zeros at the outputs of the comparators, the order in which this combination is formed in time, by the signal at the output of the pulse signal processing unit, and provided that there is no signal at the output of the frequency detection channel.

 The proposed device for detecting objects can increase the noise immunity of seismic detection means, reduce the number of false alarms, and thereby improve the quality of work of security equipment.

Sources of information
1. Patent SU 1832954, 7 G 01 V 1/28.

 2. Patent RU 2040807RF, 6 G 08 B 13/00.

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

 4. Radio-electronic systems: fundamentals of construction and theory. Reference book / Shirman Y.D., Losev Yu.I., Minervin N.N., et al. / Ed. POISON. Shirman - M .: ZAO "MAKVIS", 1998. - 828 s: ill., Bibl. 539 titles

Claims (1)

 A seismic object detection device containing a seismic transducer, the output of which is connected to the input of a signal processing circuit connected to a decision circuit, characterized by the presence of a frequency detection channel, whose input is connected to the output of a seismic transducer, and the output - to a decision circuit, while deciding on the presence of an object is taken in the case of the simultaneous presence of a signal at the output of the signal processing circuit and its absence in the frequency detection channel.

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