Communications: electrical – Vehicle detectors – Sonic or ultrasonic
Reexamination Certificate
2001-06-22
2003-01-07
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Vehicle detectors
Sonic or ultrasonic
C340S934000, C340S935000, C340S936000, C701S118000, C701S119000, C701S120000
Reexamination Certificate
active
06504490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle detection apparatus and a vehicle detection method which can detect a desired vehicle by using a microphone array.
2. Description of the Related Art
There have so far been proposed a wide variety of apparatuses for detecting the state of traffic flow from the noises produced by vehicles, and such proposed apparatuses include those intended for reducing the sizes and costs of the apparatuses. An exemplified apparatus is shown in
FIG. 16
, as comprising sound collectors
701
and
702
, amplifying circuits
703
and
704
, a switching circuit
705
, a frequency analyzing circuit
706
, a frequency distribution comparing circuit
707
, a time difference detecting circuit
708
, a time difference/velocity converting circuit
709
, a timing controlling circuit
710
and a velocity display outputting circuit
711
and determines the velocity of traffic flow by measuring noises at the two spots along and in the vicinity of a road where traffic flows (Japanese Patent Application Laid-Open No. 114098/1993).
In
FIG. 16
, the first sound collector
701
and the second sound collector
702
are placed along traffic flow with a fixed distance L therebetween. The noises A and B of the traffic flow which have been collected by these sound collectors
701
and
702
are in turn inputted to the frequency analyzing circuit
706
by switching the switching circuit
705
alternately, and their frequencies are in turn analyzed by the frequency analyzing circuit
706
, to ensure that frequency spectral distributions SA and SB are obtained.
Then, the degree of similarity between the frequency spectral distribution SA and the frequency spectral distribution SB is detected by the frequency distribution comparing circuit
707
, and the time difference between the frequency spectral distribution SA and the frequency spectral distribution SB which nearly match with each other is determined by the time difference detecting circuit
708
. The time difference/velocity converting circuit
709
determines the velocity V of a noise source (vehicle) by performing the computation represented by the expression “V=L/dt”. In this case, the direction in which the vehicle in headed can be calculated from the calculated time difference.
However, such a conventional detection apparatus has the problem that the accuracy of detecting a vehicle lowers when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than a desired vehicle because, as described above, the conventional detection apparatus measures noises only at the two spots along and in the vicinity of a road where traffic flows and calculates the velocity and traveling direction of the vehicle based on the time difference between the frequency spectral distribution SA and the frequency spectral distribution SB which nearly match with each other.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a vehicle detection apparatus which is capable of detecting a sound source even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle and calculating the location in the vehicle traveling direction and the lane direction of the vehicle and the number of passing vehicles.
It is another object of the present invention to provide a vehicle detection method which is capable of detecting a sound source even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle and calculating the location in the vehicle traveling direction and the lane direction of the vehicle and the number of passing vehicles.
In accordance with a first aspect of the present invention, there is provided a vehicle detection apparatus which comprises a sound collection means comprising a plurality of microphones and placed in the vicinity of a road; a direction estimation means for sampling the input signals from the sound collection means periodically with time windows and estimating the direction of a sound source in each time window; and a similarity calculation means for calculating the degree of similarity between the estimation results by the direction estimation means and a plurality of templates which indicate a change in the location of the sound source with time while the vehicle is traveling. According to this constitution, a change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction of a vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected. In this case, the above direction estimation means comprises an estimation means for estimating the location in the vehicle traveling direction and the lane direction of the sound source.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected. In this case, when the above road has a plurality of lanes, the vehicle detection apparatus according to the present invention comprises counters for counting the estimation results by the above direction estimation means for each lane and a lane detection means for detecting the location in the lane direction of the sound source based on the counting values of these counters.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones arranged in the form of a matrix in the same plane. According to this constitution, even when a plurality of vehicles are traveling simultaneously, the microphones arranged in the form of a matrix identifies a sound source precisely and detects the location in the vehicle traveling direction and the lane direction of the vehicle while the deterioration of the accuracy of the detection by other noises is suppressed.
In the aforesaid vehicle detection apparatus according to the present invention, the above direction estimation means comprises an estimation means for estimating the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source. According to this constitution, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an &agr; direction (lane direction) or a &bgr; d
Hofsass Jeffery
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Previl Daniel
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