Traffic sensor having piezoelectric sensors which distinguish lanes
First Claim
1. A traffic sensor for sensing the number of vehicles travelling in each lane of a predetermined portion of a roadway, comprising:
- a piezoelectric sensor stretched across a width of said predetermined portion of said roadway, said piezoelectric sensor generating an electrical signal when deflected by a vehicle, generated electrical signal having a first polarity when deflected by a vehicle in a first lane of said roadway and a second polarity when deflected by a vehicle in a second lane of said roadway; and
means for discriminating the polarity of said generated electrical signal and for determining from the respective polarities in which lane of said roadway said piezoelectric sensor has been deflected by one of the vehicles.
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Accused Products
Abstract
A traffic sensor including piezoelectric sensors having different polarities in different lanes of the roadway so that traffic data for different lanes of a roadway may be discriminated from the polarity of the received signal(s). Preferably, the piezoelectric sensors are formed by splicing oppositely polarized piezoelectric cables or films, by changing the applied electric field during manufacture so that adjacent portions of a piezoelectric cable or film have different polarities, or by applying an electric field of a reversed polarity to respective longitudinal sections of a piezoelectric film. Traffic data from up to 8 different lanes of traffic may be discriminated using only two piezoelectric sensors in accordance with the invention by providing unique combinations of output polarities for deflections of the piezoelectric sensors in the different lanes. In order to simplify installation, such piezoelectric sensors may be disposed in parallel within the same housing or concentrically within the same cable.
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Citations
28 Claims
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1. A traffic sensor for sensing the number of vehicles travelling in each lane of a predetermined portion of a roadway, comprising:
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a piezoelectric sensor stretched across a width of said predetermined portion of said roadway, said piezoelectric sensor generating an electrical signal when deflected by a vehicle, generated electrical signal having a first polarity when deflected by a vehicle in a first lane of said roadway and a second polarity when deflected by a vehicle in a second lane of said roadway; and means for discriminating the polarity of said generated electrical signal and for determining from the respective polarities in which lane of said roadway said piezoelectric sensor has been deflected by one of the vehicles. - View Dependent Claims (2, 3, 4)
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5. A traffic sensor for sensing the number of vehicles travelling in each lane of a predetermined portion of a roadway, comprising:
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a first piezoelectric sensor stretched across a width of a lane of said predetermined portion of said roadway, said first piezoelectric sensor outputting an electrical signal having a first polarity when deflected by a vehicle in said lane; a second piezoelectric sensor stretched across said width of said lane and another lane of said predetermined portion of said roadway, said second piezoelectric sensor outputting an electrical signal having a second polarity when deflected by a vehicle in either said lane or said another lane; and means responsive to said electrical signals from said first and second piezoelectric sensors for uniquely identifying from the polarities of said electrical signals whether a vehicle has passed through said lane or said another lane of said roadway.
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6. A traffic sensor for sensing the number of vehicles traveling in each of L lanes of a predetermined portion of a roadway comprising:
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n piezoelectric sensors stretched across a width of said predetermined portion of said roadway, each of said n piezoelectric sensors generating an electrical signal having one of s states of polarity when deflected by a vehicle in one of said L lanes of said roadway;
at least one lane having a different polarity from an adjacent lane; anda lane identifier responsive to respective polarities of generated electrical signals from said n piezoelectric sensors for uniquely identifying one of L=Sn said lanes from at least one other of said lanes of said roadway in which at least one of said n piezoelectric sensors was deflected by a sensed vehicle. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of making a piezoelectric sensor having a first polarity for a first finite length in a first longitudinal section thereof and a second polarity, different from said first polarity, for a second finite length in a second longitudinal section which is adjacent said first longitudinal section in a longitudinal direction of said sensor, comprising the steps of:
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extruding a piezoelectric material through an extruder at a predetermined rate; applying an electric field having said first polarity to said piezoelectric material for a first predetermined amount of time in accordance with said predetermined rate until said first finite length is polarized with said first polarity; switching said electric field to said second polarity; and applying said electric field having said second polarity to said piezoelectric material for a second predetermined amount of time in accordance with said predetermined rate until said second finite length is polarized with said second polarity.
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16. A traffic data acquisition method, comprising the steps of:
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laying n piezoelectric sensors across L lanes of a predetermined portion of a roadway; generating an electrical signal by each of said n piezoelectric sensors, said signals vehicle in one of said lanes L of said roadway at least one lane having a different polarity from an adjacent lane; and determining from said electrical signals from said n piezoelectric sensors which one of L=sn said lanes of said roadway and at least one of said n piezoelectric sensors deflected by a vehicle. - View Dependent Claims (17, 18)
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19. A traffic sensor for sensing the number of vehicles travelling in each lane of a predetermined portion of a roadway, comprising:
- at least one piezoelectric sensor stretched across a width of said predetermined portion of said roadway, said piezoelectric sensor generating at least one electrical signal when deflected by a vehicle, each said electrical signal having a first polarity when deflected by a vehicle in a first lane of said roadway and a second polarity when deflected by another vehicle in another lane of said roadway, and a discriminator for determining the polarity of each said electrical signal that corresponds to the lane in which the piezoelectric sensor was deflected by each of the vehicles.
- View Dependent Claims (20)
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21. A traffic sensor for sensing vehicles traveling in different lanes of a roadway, comprising:
- piezoelectric sensors placed in the different lanes, a first piezoelectric sensor and a second piezoelectric sensor have polarities along their respective longitudinal sections corresponding to each lane so that a unique combination of electrical signals will be received, wherein said first piezoelectric sensor placed in a first land with a first polarity, said second piezoelectric sensor placed in an adjacent lane with a different polarity, and each piezoelectric sensor generating at least one electrical signal having one of said combinations of polarities when said each piezoelectric sensor is deflected by a vehicle in one of the different lanes, and a discriminator discriminating the combination of polarities of each said electrical signal to determine the corresponding lane in which said piezoelectric sensor was deflected by said vehicle.
- View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
Specification