Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Traffic analysis or control of surface vehicle
Reexamination Certificate
1998-05-07
2001-02-27
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Traffic analysis or control of surface vehicle
C340S943000
Reexamination Certificate
active
06195608
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to highway monitoring systems in general and, more specifically, to systems which detect and signal the existence of a motor vehicle within a predetermined detection zone on the roadway.
BACKGROUND OF THE INVENTION
Highway departments use a variety of techniques to monitor traffic in an effort to detect, mitigate, and prevent congestion. Typically, each highway department has a command center that receives and integrates a plurality of signals which are transmitted by monitoring systems located along the highway. Although different kinds of monitoring systems are used, the most prevalent system employs a roadway metal detector. In such system, a wire loop is embedded in the roadway and its terminals are connected to detection circuitry that measures the inductance changes in the wire loop. Because the inductance in the wire loop is perturbed by a motor vehicle (comprising a quantity of ferromagnetic material) passing over it, the detection circuitry can detect when a motor vehicle is over the wire loop. Based on this perturbation, the detection circuitry creates a binary signal, called a “loop relay signal,” which is transmitted to the command center of the highway department. The command center gathers the respective loop relay signals and from there makes a determination as to the likelihood of congestion. The use of wire loops is, however, disadvantageous for several reasons.
First, a wire loop system will not detect a motor vehicle unless the motor vehicle comprises a sufficient ferromagnetic material to create a noticeable perturbation in the inductance in the wire loop. Because the trend is to fabricate motor vehicles with non-ferromagnetic alloys, plastics and composite materials, wire loop systems will increasingly fail to detect the presence of motor vehicles. It is already well known that wire loops often overlook small vehicles. Another disadvantage of wire loop systems is that they are expensive to install and maintain. Installation and repair require that a lane be closed, that the roadway be cut and that the cut be sealed. Often too, harsh weather can preclude this operation for several months.
Other non-invasive systems have been suggested. U.S. Pat. No. 5,060,206, patented Oct. 22, 1991, by F. C. de Metz, Sr., entitled “Marine Acoustic Aerobuoy and Method of Operation,” provided a marine acoustic detector for use in identifying a characteristic airborne sound pressure field generated by a propeller-driven aircraft. The detector included a surface-buoyed resonator chamber which was tuned to the narrow frequency band of the airborne sound pressure field and which had a dimensioned opening formed into a first endplate of the chamber for admitting the airborne sound pressure field. Mounted within the resonator chamber was a transducer circuit comprising a microphone and a preamplifier. The microphone functioned to detect the resonating sound pressure field within the chamber and to convert the resonating sound waves into an electrical signal. The preamplifier functioned to amplify the electrical signal for transmission via a cable to an underwater or surface marine vehicle to undergo signal processing. The sound amplification properties of the resonator air chamber were exploited in the passive detection of propeller-driven aircraft at airborne ranges exceeding those ranges of visual or sonar detection to provide 44 dB of received sound amplification at common aircraft frequencies below 100 Hz. However, this patent used only a single electro-acoustic transducer for receiving acoustic signals within a detection zone, and did not teach spatial discrimination circuitry for representing acoustic energy emanating from a detection zone.
U.S. Pat. No. 3,445,637, patented May 20, 1969, by J. M. Auer, Jr., entitled “Apparatus For Measuring Traffic Density” provided apparatus for measuring traffic density in which a sonic detector produced a discrete signal which was inversely proportional only to vehicle speed for each passing vehicle. A meter, which was responsive to the discrete signals, produced a measurement representative of traffic density. However, this patent used only a single electro-acoustic transducer for receiving acoustic signals within a detection zone, and did not teach spatial discrimination circuitry for representing acoustic energy emanating from a detection zone.
U.S. Pat. No. 3,047,838, patented Jul. 31, 1962, by G. D. Hendricks, entitled “Traffic Cycle Length Selector” provided a traffic cycle length selector which automatically related the duration of a traffic signal cycle to the volume of traffic in the direction of heavier traffic along a throughfare. The Hendricks system did not teach the use of electro-acoustic transducers, but instead used pressure-sensitive detectors. While Hendricks employed plural, non-electro-acoustic transducers, the traffic cycle length selector system did not include spatial discrimination circuitry. Hendricks merely described the use of the output of several spatially discriminate detectors to generate a spatially indiscriminate signal.
SUMMARY OF THE INVENTION
Aims of the Invention
One object of the present invention is to provide apparatus and method to monitor highway traffic while avoiding many of the costs and restrictions associated with prior techniques.
Another object of the present invention is to provide such apparatus which can be installed and maintained in any weather and which does not require that the roadway be closed, torn-up or repaved.
Statements of Invention
The present invention provides apparatus for detecting vehicles moving through a predetermined zone, comprising: (a) a plurality of acousto-electric transducers trained on that zone; (b) bandpass filtering means for processing electrical signals from the plurality of acousto-electric transducers; (c) correlator means having at least two inputs and an output for correlating filtered versions of the electrical signals originating from at least two of the plurality of acousto-electric transducers; (d) integrator means for integrating the output of the correlator means over time; and (e) comparator means for indicating detection of a vehicle when the integrated output exceeds a predetermined threshold.
The present invention also provides a method for detecting vehicles moving through a predetermined zone, comprising the steps of: (a) training a plurality of acousto-electric transducers on that zone; (b) filtering electrical signals from the plurality acousto-electric transducers; (c) correlating at least two of the filtered electrical signals with one another; (d) integrating the results of correlation in step (c) over time; and (e) comparing the integrated result of step (d) to a predetermined threshold and indicating detection of a vehicle when the threshold is exceeded by the integrated result.
Other Features of the Invention
By one feature of this invention, the apparatus further includes a plurality of analog-to-digital converter means for converting said electrical signals to digital representations prior to the processing thereof.
By a further feature of this invention, the integrator and the comparator means are each microprocessor-based programs.
By still another feature of this invention, the plurality of acousto-electric transducers comprises two vertical and two horizontal multiple-microphone elements, and the correlator means has one of the at least two inputs receiving a sum of the two multiple-microphone vertical elements, and the other of the at least two inputs receiving a sum of the two horizontal multiple-microphone elements.
By one feature of the method of this invention, the method further includes the step of converting said electrical signals to digital representations prior to said filtering. By a feature of such feature, the steps of integrating and comparing are each computational routines.
By another feature of the method of this invention, the plurality of acousto-electric transducers comprises two vertical and two horizontal multiple-microphone elements, and the correla
Berliner Edward Fredrick
Kuhn John Patrick
Rawson Scott Andrew
Whalen Anthony Donald
Chin Gary
Finston Martin I.
Lucent Technologies - Inc.
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