Detection of moving objects

• US 5,107,250 A
• Filed: 01/07/1980
• Issued: 04/21/1992
• Est. Priority Date: 01/07/1980
• Status: Expired due to Term

• Current Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Original Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Pykett, Colin E.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US06/116,343
• Time in Patent Office: 4,488 Days
• Field of Search: 367/136, 340/566
• US Class Current: 340/566
• CPC Class Codes: G08B 13/1663 using seismic sensing means
• CPC Class Codes: G08G 1/015 with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles

Abstract

A system for detecting and classifying vehicles, moving in the vicinity of a seismic detector, includes a time threshold circuit and, complementary to this circuit, two parallel amplitude detector circuits. One detector circuit utilizes amplitude thresholding to distinguish the seismic vibrations characteristic of moving vehicles, from other seismic vibrations. The other detector circuit utilizes amplitude thresholding to distinguish the seismic vibrations characteristic of a particular kind of moving vehicle (e.g. a tracked vehicle), from other seismic vibrations. The results of these two amplitude detector circuits and of the time threshold circuit are utilized by an indicator circuit and an indication of detected vehicle kind (e.g. tracked or wheeled) provided. Indication may be relayed, to a remote observer, by radio transmission.

Claims

1. In a system for detecting moving ground vehicles of the type including a seismic detector capable of detecting seismic vibrations generated by moving vehicles and of providing in response a corresponding electrical signal;

first detector means connected to the seismic detector, responsive to the electrical signal, for providing a first information signal, to distinguish electrical signals having peak amplitudes above and below a first amplitude threshold, namely a threshold of such set value as to distinguish electrical signals corresponding to seismic vibrations of peak amplitude characteristic of moving ground vehicles, from electrical signals corresponding to other seismic vibrations; and

indicator means connected to the first detector means, responsive to the information signal therefrom, for indicating the presence of a detected moving vehicle;

the improvement comprising a second detector means connected to the seismic detector, parallel to the first detector means, responsive to the electrical signal, for providing a further information signal, to distinguish electrical signals having peak amplitudes above and below a second amplitude threshold, namely a threshold of such set value as to distinguish electrical signals corresponding to seismic vibrations of peak amplitude characteristic of moving ground vehicles of a particular kind from electrical signals corresponding to seismic vibrations of peak amplitude characteristic of other sources including moving vehicles not of this particular kind;

said indicator means also being responsive to said further information signal, and being capable of providing in response an indication of the kind of moving vehicle detected, said system further including a duration channel connected to the seismic detector for discriminating against electrical signals of less than and longer than a given time interval, the duration channel including, connected in series in the following order;

a first signal comparator, a monostable, an integrator, and an amplifier;

the amplifier being connected to the first signal comparator to provide a first reference signal, the duration channel also including a second signal comparator connected to the amplifier, and a voltage source connected to the second signal comparator to provide a second reference signal for defining the time interval.

2. A system according to claim 1 wherein the second amplitude threshold is such as to distinguish an electrical signal corresponding to seismic vibrations that are of peak amplitude characteristic of a moving tracked vehicle from an electrical signal corresponding to seismic vibrations that are of peak amplitude characteristic of other sources including moving wheeled vehicles.

3. A system according to claim 1 wherein the indicator means includes a logic circuit capable of responding to changes of said information signals, the logic circuit being capable of providing a delayed indication whenever the first information signal changes corresponding to an electrical signal of peak amplitude rising above the first amplitude threshold, the indication distinguishing between two outcomes, namely:

a first outcome where the further information signal changes corresponding to an electrical signal of peak amplitude that rises above the second amplitude threshold; and

a second outcome where the electrical signal peak amplitude rises to a maximum amplitude between the first and second amplitude thresholds.

4. A system according to claim 3 wherein the logic circuit is capable of comparing changes of said information signals, and detecting, and providing indication of, the second outcome by checking between changes of the first information signal corresponding to an electrical signal of peak amplitude that rises above and falls below the first amplitude threshold, that there is no change in the further information signal.

5. A system according to claim 1 wherein each detector means includes:

an amplifier of specified gain a peak extractor connected to the amplifier for determining the peak amplitude of electrical signals amplified thereby, and a comparator connected to the peak extractor; and

a common voltage source connected to the comparators;

the amplifiers each being of different gain and in combination with the voltage source defining respectively the first and second amplitude thresholds for distinguishing the electrical signals.