Abstract
Lanes sensors are used to count the number of wheel assemblies on vehicles passing over roadway sensors. Lane sensors can also be used to classify vehicles at single and multiple lane sites for tolling and/or traffic planning. For counting vehicles, the Smart Loop Treadle of the present invention is designed for both tire and wheel assembly detection using inductive loop sensors for toll roads in single (Conventional) lane applications. The sensors detect the tire assemblies of both vehicles and vehicle trailers being towed to provide the sum of axle assemblies. For vehicle characterization, the sensor arrangement can have a combination of unique sensors that include tire/wheel detection sensors and vehicle lane position sensors. The characteristics of the vehicle, travel direction, speed, in lane position of the vehicle can be detected using combination of these sensors.
Claims
1. A lane sensor for detecting the passage of a vehicle over the lane sensor, the lane sensor comprising: a first, Eddy Current sensor for detecting wheel assemblies having non-steel belted tires; a second, Ferromagnetic sensor for detecting steel belted tires; a controller for receiving information from both the first and second sensors to detect the passage of a vehicle over the lane sensor whether the vehicle has steel belted tires or non-steel belted tires.
2. The lane sensor of claim 1, further comprising: said second, Ferromagnetic sensor and said first, Eddy Current sensor being installed in a roadway, with said second Ferromagnetic sensor being installed on top of said first, Eddy Current sensor.
3. The lane sensor of claim 2, further comprising: said second, Ferromagnetic sensor and said first, Eddy Current sensor being installed in a single lane of travel of roadway, with said second Ferromagnetic sensor being installed 1-2 inches below a surface of the roadway; and said first, Eddy Current sensor being installed 3-6 inches below the surface of the roadway.
4. The lane sensor of claim 1, wherein said second, Ferromagnetic sensor includes a series of three or more rectangular sensors connected in series
5. The lane sensor of claim 1, further including a lane position sensor, wherein said lane position sensor includes a left sensor loop and a right sensor loop installed in a lane of travel to determine the position of a vehicle within the lane of travel.
6. The lane sensor of claim 1, wherein each of said first and second sensors detect frequency changes caused by the wheel assemblies with steel belted tires or non-steel belted wheel assembly.
7. The lane sensor of claim 1, including at least two Eddy Current sensors and two Ferromagnetic sensors for detecting a direction of travel of the vehicle over the lane sensor.
8. The lane sensor of claim 7, further including a lane position sensor, wherein said lane position sensor includes a left sensor loop and a right sensor loop installed in a lane of travel to determine the position of a vehicle within the lane of travel.
9. The lane sensor of claim 8, wherein said controller detects from said first and second sensors and from said lane position sensor, the vehicle direction of travel and speed over the lane sensor, the number of axles on the vehicle, the presences of double tire wheel assemblies (“dualie tires”), the vehicle length, the axle spacing, the vehicle travel position in the lane, and a vehicle classification for the vehicle.
10. A method of detecting objects passing over a location, comprising: providing a first, Eddy Current sensor installed at the location for detecting wheel assemblies having steel belted tires or non-steel belted tires passing over the location; providing a second, Ferromagnetic sensor for detecting steel belted tires passing over the location; providing a controller in communication with the first and second sensors, said controller receiving information from both the first and second sensors, and interpreting the information from the first and second sensors to detect the passage of steel belted tires and wheel assemblies having non-steel belted tires over the location.
11. A method of detecting objects passing over a location, comprising: providing a first, Eddy Current sensor and a second, Ferromagnetic sensor; providing a controller in communication with the first and second sensors, said controller receiving information from both the first and second sensors; said first, Eddy Current sensor comprising a wire loop installed at the location for detecting wheel assemblies having non-steel belted tires passing over the location; applying an oscillating frequency to said wire loop to create flux fields across at least a portion the location; said first, Eddy Current sensor sensing a change in the frequency when a wheel assembly passes through the flux field changing the resonant frequency of the first, Eddy Current sensor, said second, Ferromagnetic sensor comprising a sensor loop wire installed at the location for detecting steel belted tires passing over the location; applying an oscillating frequency to said sensor loop wire to create magnetic fields across at least a portion the location; providing a controller in c said second, Ferromagnetic sensor sensing a change in the frequency when a steel belted tire passes through the magnetic field changing the resonant frequency of the second, Ferromagnetic sensor; said controller in communication receiving information from both the first and second sensors generated by the change in frequencies sensed by the first and second sensors; said controller interpreting the information from the first and second sensors to detect the passage of steel belted tires and wheel assemblies having non-steel belted tires over the location.
12. The method of detecting objects passing over a location of claim 11, further comprising: said controller determining from the information received from the first and second sensors a number of vehicles passing over the location.
13. The method of detecting objects passing over a location of claim 11, further comprising: said controller determining from the information received from the first and second sensors a vehicle direction of travel and speed over the lane sensor for a vehicle associated with wheel assembly or with the steel belted tires, the number of axles on the vehicle, the presences of more than two tires per axel, the vehicle length, the spacing between sequentially detected axles, the vehicle travel position in the lane, and a vehicle classification for the vehicle associated with wheel assembly or with the steel belted tires.
14. The method of detecting objects passing over a location of claim 11, wherein said second, Ferromagnetic sensor and said first, Eddy Current sensor are installed in a single lane of travel of roadway, with said second Ferromagnetic sensor being installed 1-2 inches below a surface of the roadway; and said first, Eddy Current sensor being installed 3-6 inches below the surface of the roadway.
15. The method of detecting objects passing over a location of claim 11, wherein said second, Ferromagnetic sensor includes a series of three or more rectangular sensors connected in series
16. The method of detecting objects passing over a location of claim 11, further including a lane position sensor, wherein said lane position sensor includes a left sensor loop and a right sensor loop installed in a lane of travel to determine the position of a vehicle within the lane of travel.
17. A lane sensor for detecting the passage of a vehicle over the lane sensor, the lane sensor comprising: a first, Eddy Current sensor for detecting wheel assemblies having non-steel belted tires and wheel assemblies having steel belted; a second, Ferromagnetic sensor for detecting steel belted tires; a controller for receiving information from both the first and second sensors to detect the passage of a vehicle over the lane sensor whether the vehicle has steel belted tires or non-steel belted tires.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0048] FIG. 1 is a diagram of smart loop treadle with a double threshold and a single threshold in a single toll lane. This combination allows for the detection of wheel assemblies having steel belted tires and non-steel belted tires. Also, the system detects the direction of vehicle travel and can detect a reversal in the direction of a vehicle traveling over the sensor. The sensor is bidirectional. The double threshold smart loop treadle contains two Eddy current sensor (22×24 with 5 turns and 6 segments) and two Ferromagnetic sensors (3-6-6-3). The single threshold sensor contains one Eddy current sensor and one Ferromagnetic sensor.
[0049] FIG. 1A is a system block diagram of smart loop treadle in single toll lane. The three primary components of the system include the four sensors, a loop amplifier, and a controller. The Smart Loop Treadle assembly includes two Eddy Current sensors and two Ferromagnetic sensors. These sensors are installed on or near the road surface.
[0050] FIG. 1B is a diagrammatic view of a multiple lanes application with smart loop treadle sensors and a lane position sensor. The device assembly shown illustrates the primary lane components relationship including the two loop circuits in the Lane Position sensor and the Smart Loop Treadle sensors that include an Eddy Current sensor and Ferromagnetic sensor. This illustrates an alternative lane layout of the Lane Position sensor. The two loop circuits can be installed with the loop sensor leading edge perpendicular to the direction of traffic and having each loop circuit rotated forty-five degrees to the direction of traffic.
[0051] FIG. 1C is a system block diagram of multiple lane installation. The system block diagram illustrates the primary components relationships including the Eddy Current Sensor, Ferromagnetic Sensor, Lane Position Sensor, Loop detector, and Processing Controller.
[0052] FIG. 1D is a graph showing an eddy current sensor and ferromagnetic sensor-signature of a SUV vehicle towing a trailer with 1 axle. The signature from Eddy Current sensor illustrates how the frequency of the sensor is lowered from the eddy current effect when a vehicles towing a trailer passes over the sensor. The signature from a Ferromagnetic sensor illustrates how the frequency of the sensor increases from the Ferromagnetic effect when a vehicle towing a trailer passes over the sensor.
[0053] FIG. 2 is a graph showing an eddy current sensor with six (6) equal segments and five (5) turnings. The drawing illustrates the construction and installation of an Eddy Current sensor having six equal segments and five wire turnings. The sensor provides detection for the entire lane of travel. This example of an Eddy Current sensor has six segments each 22 inches wide by 24 inches long. The single sensor circuit has five wire turnings.
[0054] FIG. 2A is a graph showing an eddy current sensor with equal segments' signature of motorcycle with polyester reinforced tires. The signature from the Eddy Current sensor has a decrease in the frequency when the motorcycle passes over the sensor. The two decreases in the frequency are from the eddy currents that are created when the front and rear wheel travel over the sensor.
[0055] FIG. 2B is a diagrammatic view of an eddy current sensor with unequal segments four (4) (22W×16L) and two (2) (15W×16L) with five (5) windings. The drawing illustrates an Eddy Current Loop having a total of six (6) rectangular segments that are unequal in widths and the sum of the segments creates a sensor 9 feet 10 inches wide by 16 inches long. This sensor length can be used in a lane 11 feet wide. This sensor width can be adjusted to provide for the detection of the full width of lane by using segments that have different lengths.
[0056] FIG. 2C is a diagrammatic view of an eddy current with segments that have unequal widths the sum of the segments width is 9 feet wide and this sensor can be used for lanes 10 feet wide. The drawing illustrates an eddy current loop having a total of five rectangular segments that are unequal. This sensor width can be adjusted to provide detection the full width of lane by using segments that have different lengths. This sensor is designed to provide full coverage in a travel lane ten (10) feet wide.
[0057] FIG. 2D is a diagrammatic view of an eddy current sensor's signature of a pick-up truck with 1 axle trailer. The signature from the Eddy Current sensor has a decrease in the frequency when the Pick-up truck towing a trailer with one axle. The Eddy current sensor detects the pick-up truck has steel belted tires and the trailer wheel assemblies has a non-steel belted tires.
[0058] FIG. 2E is a diagrammatic view of Eddy Current Sensors Signatures from three different Eddy Current Sensors with Unequal Size Segments. This illustrates the signatures from three different Eddy Current sensors sizes. All the signatures are from the same vehicle.
[0059] FIG. 2F is a diagrammatic view of Eddy Current Sensor with Unequal Segments four (4)(22W×16L) and three (3) (15W×16L) with five (5) Windings. This sensor is designed for a lane that is 12 feet wide. The sensor has an overall width of 11 feet and 1 inch. The sensor has a length of 16 inches.
[0060] FIG. 2G is a diagrammatic view of eddy current sensors with unequal segments and ferromagnetic sensor. This illustration includes a comparison of a vehicle signature from a Ferromagnetic Sensor and the signatures from three Eddy Current sensors when the same vehicle passes over all four sensors. The Eddy Current sensors frequencies decrease during the detection and the Ferromagnetic sensor frequency increase during the detection.
[0061] FIG. 2H is a diagrammatic view of eddy current sensor with unequal wire turnings. This illustrates the windings that are formed using counter clockwise and counter clockwise turnings. The rectangular segments are equal in size. The number of wire turnings are forming the rectangular segments is unequal.
[0062] FIG. 3 is a diagrammatic view of ferromagnetic sensor 2-4-4-2 windings. This drawing illustrates the three rectangular loops of the Ferromagnetic sensor. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction. The sensor is typically 11 feet wide by 12 inches long. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction.
[0063] FIG. 3A is a diagrammatic view of ferromagnetic sensor 3-6-6-3 windings. This drawing illustrates the three rectangular loops of the Ferromagnetic sensor has three wire turnings. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction. The sensor is typically 11 feet wide by 12 inches long.
[0064] FIG. 3B is a diagrammatic view of ferromagnetic sensor 4-8-8-4 windings. This drawing illustrates the three rectangular loops of the Ferromagnetic sensor has four wire turnings. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction. The sensor is typically 11 feet wide by 12 inches long. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction.
[0065] FIG. 3C is a diagrammatic view of the signature from a pickup truck traveling over a ferromagnetic sensor with 2-4-4-2 windings. The frequency of a Ferromagnetic Sensor increases when the vehicle wheels pass over. The sensor is typically 11 feet wide by 12 inches long.
[0066] FIG. 3D is a diagrammatic view of a signature of SUV from ferromagnetic 3-6-6-3. The frequency of a Ferromagnetic Sensor increases when the vehicle wheels pass over. The sensor is typically 11 feet wide by 12 inches long.
[0067] FIG. 3E is a diagrammatic view of ferromagnetic sensor 2-4-4-4-2 windings. This drawing illustrates the four rectangular loops of the Ferromagnetic sensor. The sensor is typically 11 feet wide by 16 inches long. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction.
[0068] FIG. 3F is a diagrammatic view of ferromagnetic sensor 2-4-4-4-4-2 windings. This drawing illustrates the five rectangular loops of the Ferromagnetic sensor. The sensor is typically 11 feet wide by 20 inches long. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction.
[0069] FIG. 3G is a diagrammatic view of ferromagnetic sensor 2-4-4-4-4-4-2 windings. This drawing illustrates the six rectangular loops of the Ferromagnetic sensor. The sensor is typically 11 feet wide by 24 inches long. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction.
[0070] FIG. 3H is a diagrammatic view of signature of a five axle truck from a 2-4-4-4-4-4-2 ferromagnetic sensor. The frequency of a Ferromagnetic Sensor increases when the vehicle wheels pass over. The sensor is typically 11 feet wide by 24 inches long.
[0071] FIG. 3I is a diagrammatic view of cross section of wheel assembly sensors used in multi-lane tolling application using a (3-6-6-3), (3-6-6-6-3), (3-6-6-6-6-3), and (3-6-6-6-6-6-3). This drawing illustrates the Ferromagnetic sensor having three wire turnings. The cross sectional views of the sensors wire turnings illustrate the increasing of the number of rectangular sections having alternating windings from clockwise direction to the counter clockwise direction. The sensor width can be increased or decreased to provide full detection for the width of the lane. The length of the sensor can be increased from (3-6-6-3) that is 12 inches long to (3-6-6-6-6-6-3) that is 30 inches long. The increase in the sensor lengths increases the sensor sample length.
[0072] FIG. 3J is a diagrammatic view of Ferromagnetic Sensor 2-3-2-3-2 Windings. This drawing illustrates an alternate design for the Ferromagnetic sensor windings. This different winding pattern produces a different flux field and ratio in the windings. The drawing to provides the pattern for the windings and a cross section of the wire turnings having the designation (2-3-2-3-2) and a length of 16 inches.
[0073] FIG. 3K is a diagrammatic view of ferromagnetic sensor 2-3-2-3-3-2-3-2 windings. This drawing illustrates the Ferromagnetic sensor windings. This winding pattern produces a sensor that is 28 inches long. The drawing provides the pattern for the windings and a cross section of the wire turning having the designation (2-3-2-3-3-2-3-2).
[0074] FIG. 3L is a diagrammatic view of signature from a two axle truck with dual tires on an axle passing over a ferromagnetic sensor. is a diagrammatic view of 2-3-2-3-2. This is an illustration of a vehicle signature from a SUV traveling over a Ferromagnetic sensor 2-3-2-3-2 having one winding. The frequency of a Ferromagnetic Sensor increases when the vehicle wheels pass over the sensor. The sensor is typically 11 feet wide by 12 inches long.
[0075] FIG. 4 is a diagrammatic view of lane position sensor plan view and cross section of parallel installation. The sensor is composed of two separate wire windings and they are identical in the shape and number of turns. The pair of loops overlap in the center of the travel lane. They do not overlap on the left side and right side on the lane. The cross section of the loop illustrates the area where the two circuit overlap.
[0076] FIG. 4A is a diagrammatic view of lane position sensor plan view and cross section of diamond installation. The sensor is composed of two separate wire windings and they are identical in the shape and number of turns. They are installed at an angle of 45 degrees to the direction of travel. The pair of loops overlap in the center of the travel lane. They do not overlap on the left side and right side on the lane. The cross section of the loop illustrates the area where the two circuit overlap.
[0077] FIG. 4B is a diagrammatic view of sample signature of vehicle traveling on the left of the lane. The signature indicates that the vehicle is traveling on the left side of the lane. The change in frequency is greater in the left loop circuit. This information can aid in correlating the toll tag read and /or the vehicle image in toll applications.
[0078] FIG. 4C is a diagrammatic view of sample signature of vehicle traveling in the center of the lane. The signature indicates that the vehicle is in the center of the lane and the change in frequency is equal in both he left and right loop circuit. This information can aid in correlating the toll tag read and/or the vehicle image in toll applications.
[0079] FIG. 4D is a sample signature of vehicle traveling on the right side of the lane. The signature indicates that the vehicle is traveling on the right side of the lane. The change in frequency is greater in the right loop circuit. This information can aid in correlating the toll tag read and/or the vehicle image in toll applications.
[0080] FIG. 5 is a diagrammatic view of prior art of wheel sensors and loop arrangements. This drawing illustrates three arrangements of sensors in a lane that are used for vehicle classification in a lane. These sensor arrangements include wheel sensors and inductive loops.
[0081] FIG. 5A is a diagrammatic view of prior art of toll lanes with treadle. This drawing illustrates two arrangements of sensors in a lane that are used for toll collection at a toll booth. These sensor arrangements include a treadle and an inductive loop.
[0082] FIG. 6 is a diagrammatic view of a prior art Stanczyk cross section wheel detection on a rectangular type loop. This illustrates the single rectangular winding of the sensor as divulged in the patent. The sensor provides two thresholds and is restricted in its length geometry to being smaller than the diameter of the wheel. The sensor detects both the wheel assemblies and the chassis. The positive voltage reading is from the chassis. The negative voltage is from the wheels of the vehicle.
[0083] FIG. 7 is a diagrammatic view of a prior Art Lee cross section wheel detection on quadrupole type loop. This illustrates the quadrupole or figure eight winding. This design incorporates multiple sensors with figure eight winding circuits. There are typically two loop circuits per wheel path and a total of four used per lane for detection.
[0084] FIG. 8 is a diagrammatic view of a prior art publication no. FHWA-IP-90-002, bicycle lane loop layout. This serpentine pattern of wire turnings was also divulged and used in the bicycle loop in Publication “Traffic Detection Handbook, Second Edition, Publication No. FHWA-IP-90-002 date July 1990, page 93 FIG. 94. Bicycle lane loop layout.
[0085] FIG. 9 is a diagrammatic view of a prior art Allen cross section wheel detection on a serpentine polygon loop. This illustrates the series serpentine windings in a rectangular pattern. The preferred design has two different lengths of rectangles in a single circuit.
[0086] FIG. 10 is a diagrammatic view of a Prior Art Publication No. FHWA-IP-90-002, Directional detection. The use of two rectangular loops on separate circuits can be used to support directional logic.
DETAILED DESCRIPTION OF THE INVENTION
[0087] System Description FIG. 1 illustrates the preferred installation of the Smart Loop Treadle with a double threshold smart loop treadle (107) having two pairs of sensors. Each pair of sensors contains one Eddy current sensor (101) and one Ferromagnetic sensor (102) creating a Smart Loop Treadle assembly. The Eddy current sensor is installed below the ferromagnetic sensor. Two smart loop treadle assemblies (100) are installed in the roadway side by side. The single threshold Smart Loop Treadle (100) contains one Eddy Current effect type sensor and one Ferromagnetic effect type sensor. These sensors are arranged in the roadway by having the Eddy current sensor installed in the roadway below the Ferromagnetic sensor that is installed in the roadway close to the surface of the roadway The preferred method of installation is having the Eddy Current type sensor (101) installed below the Ferromagnetic effect type sensor (102). These two types of sensors provide the detection of two types of wheel assemblies: the non-ferrous wheel assemblies (Eddy Current Type) such as a wheel assembly with a polyester tire and the ferrous materials (Ferromagnetic Type) such as a wheel assembly with a steel belted tire. The sensors are installed on top of the roadway or near the surface of the roadway (103). Also, the direction of vehicle travel (104) is perpendicular to the width (105) of the sensor and the length of the sensor (106) is parallel to the direction of travel. The Smart Loop Treadle can be installed providing a double threshold (107) to detect a reverse in the direction of a vehicle traveling over the sensor. This also provides redundant wheel detection. A Smart Loop Treadle sensor can be installed having a single threshold (108) configuration. This can be used in
[0088] applications where detection of vehicles reversing direction is not required or additional sensors are present to support the detection of vehicle's reversing their direction of travel.
[0089] FIG. 1A is a system diagram that illustrates the components of a Smart Loop Treadle having a double threshold sensor array composed of two Smart Loop Treadle assemblies (118). The Eddy current sensors (110) are all designed to optimize the detection of wheel assemblies while minimizing the detection of the vehicle chassis and the Ferromagnetic sensor (111) is optimized to detect steel belted reinforced tires. This installation can also be used for the single threshold Smart Loop Treadle that includes one Eddy current sensor (110) and one Ferromagnetic sensor (111).
[0090] The Smart Loop Treadle assemblies provide detection of both steel belted reinforced tires and non-steel belted tires in, for example, wheel assemblies that contain polyester reinforced tires. The Smart Loop Treadle is designed to provide the detection of a vehicle's direction of travel (112) as the vehicles pass over the Smart Loop Treadle located in the roadway (113). The detection of both wheel assemblies with non-steel ferrous tires and steel belted reinforced tires are detected this is very important since both types of tires exist in the general vehicle population. Also they both can occur in combination on the same vehicle when trailers are towed by vehicles.
[0091] This detection is accomplished by using two distinctly different sensor designs described in this patent. One sensor type is designed to optimize the detection of wheels with non-steel belted tires by responding with a decrease in frequency when wheel assemblies having non-steel belted tires pass over the sensors (110). The second sensor type is designed to optimize the detection ferrous materials and reinforced steel belted tires by responding with an increase in frequency when the steel belted reinforced tires pass over the sensor (111).
[0092] This invention works by using a Eddy current loop sensor that is installed in the roadway and below the surface at the preferred depth of 3 to 6 inches. The sensor's magnetic field is intersected by the wheels of vehicles passing over the sensor. When the wheels intersect the magnetic fields of the sensor the resonant frequency of the loop sensor decreases and these frequency changes are measured to detect to wheels on the vehicles.
[0093] The ferromagnetic sensor is installed in the roadway and near the surface at the preferred depth of 1 to 2 inches. When vehicles wheels pass over the ferromagnetic loop sensor the steel belted tires can conduct the magnetic fields. This causes an increase in the magnetic fields strength and will cause the frequency of the loop circuit to increase. The increase in frequency is measured to detect the steel belted tires on tires on the vehicle. The sensor loop wire is activated with an oscillating frequency by the loop detector amplifier and acts like an antenna. Each sensor has magnetic fields associated with the loop circuit. This oscillating loop circuit has a resonant frequency that is provided as an output. The output frequency is sent and monitored by the controller. When vehicles pass over the sensor's loop wire the frequency of the loops circuit will change by increasing and/or decreasing. The controller contains software algorithms that interrupts the outputs from the various sensors and records the results. These results are processed to provide the number of vehicle axles and vehicle classification.]
[0094] For example, the non-ferrous tire wheel assemblies are detected by sensors that are designed to optimize the effect of Eddy currents that generate resistive losses that are a source of energy loss and lower the residence frequency of the loop circuit when the non-ferrous wheel assemblies pass over the sensor (110). In contrast, steel belted reinforced tires are detected from the rotatory magnetism by loop sensors designed to optimize the ferromagnetic effect that provides an increase in the loop residence frequency when the steel belted reinforced tires pass over the sensor (111).
[0095] The use of both types of sensors in the Smart Loop Treadle provides very high accuracy for wheel assembly detection. Vehicles with non-steel belted tires such as small cars, motorcycles, and small trailers are detected by the first type of sensors that optimize the Eddy current effect (110). Vehicles containing steel belted reinforced tires such as cars or trucks are detected by the second type of sensor that optimizes the ferromagnetic effect (111).
[0096] The Smart Loop Treadle design can be used by transportation planning and tolling agencies for vehicle classification. The sensors generate an electromagnetic flux field that can be used to distinguish single tire wheel assemblies from dual tire wheel assemblies. The information can be used to levy toll revenue.
[0097] The Smart Loop Treadle sensor assembly provides the direction of the vehicle and can detect when a vehicle reverses direction. The assembly contains both types of sensors and can accurately count the number of wheel assemblies when a vehicle traveling over the sensors has steel belted tires and is towing a vehicle or trailer that has non-steel belted tires.
[0098] This invention, the Smart Loop Treadle in FIG. 1A (details 110 & 111), is used in combination with two other components: a traffic loop amplifier (114), and signal processing controller (115). The tire assembly sensors (details 110 &111) are activated by a traffic loop amplifier (114). The loop amplifier (114) provides oscillating frequencies into the sensor circuits, creating fields of flux and the frequencies of the sensors change when the vehicles on the roadway pass through the fields of flux present in the sensors. This causes changes in the resident frequency of the sensors that are sent from the loop amplifier to the controller. The traffic loop detector processes these frequency changes and they are expressed in a digital data stream to the data processing controller (115).
[0099] The digital data stream from the loop amplifier is processed and analyzed by the signal processing controller (115) to identify the vehicle tire assembly characteristics from a vehicle traveling over a sensor or sensors. This information is associated with the vehicle attributes and applied to the sum of axles present on the vehicle or applied to classify the vehicles. The data processing controller is composed of communication ports for inputs and outputs of the processed sensor information. The controller processes the input and outputs storing the vehicle characteristics and can transmit the processed information to other devices as required by the application.
[0100] A multiple lane installation is illustrated in FIG. 1B each lane has a Lane Position Sensor (details 120 & 121), Ferromagnetic Sensor (122) and Eddy Current Sensor (123). The Lane Position Sensor contains two loop circuits a left side loop circuit (120) and a right side loop circuit (121). The lane position sensor identifies the vehicle position in the travel lane by determining if the vehicle is traveling on the left side of the lane, in the center of the lane or on the right side of the lane. The lane position sensor contains two separate loop circuits in a travel lane. The loops overlap each other and one loop is place towards the left side of the lane and the other loop is placed towards the right side of the lane. The two loop sensors are connected to loop amplifier. The loop sensor frequency of both loops is monitored by the controller. The amplitude of the signatures are compared. When a vehicle passes over the loops the frequency of the loops changes. The amount of frequency change that occurs in each loop is compared. When the vehicle is traveling in the center of the lane the amount of frequency change in the two loops is equal. This indicates that the vehicle is traveling in the center of the lane.
[0101] When a vehicle travels on the left side of the lane the amount of frequency change in the two loops is compared and the loop located towards the left side of the lane has a greater change in frequency than the loop located towards the right side of the lane. This indicates that the vehicle is traveling on the left side of the lane.
When a vehicle travels on the right side of the lane the change in loop frequencies is compared. The loop located towards the right side of the lane has a greater change in frequency. This indicates that the vehicle is travel on the right side of the lane.
[0102] In FIG. 1C, the system block diagram of a multiple lane installation is illustrated. The primary components include the three sensors the Lane Position Sensor (130 & 131), Ferromagnetic Sensor (132), and Eddy Current Sensor (133). These sensors are connected to a traffic loop amplifier (134). The traffic loop detector is connected to the processing Controller (135). The processing controller can store vehicle classification information and transmit the information for toll and traffic planning applications. When used for tolling applications the Smart Loop Treadle can detect and identify different wheel assemblies such as single tire assemblies and dual tire assemblies present on vehicles. This information is used to assign the amount of payment due in the tolling operation. This same information can be used for planning applications to classify the type of vehicle.
[0103] The number of lanes can be increased or decreased depending on the sight requirements. Each lane contains the same sensor layout. This sequence of sensors includes the Ferromagnetic Sensor (132), and the Eddy Current Sensor (133), and the vehicle position sensor (130 & 131). The direction of travel (136) provides the sequence of sensor signatures. This combination of sensors provides digital signatures that are processed into vehicle classification as required by the FHWA traffic monitoring guide or can be configured to provide a different schema.
[0104] The Test Signature of FIG. 1D illustrates the signature for an SUV with Steel Belted tires towing a single axle trailer with polyester reinforced tires. The SUV steel belted tires are detected by the Ferromagnetic sensor (140) and produce an increase in frequency illustrated by the two peaks (141) from the front and rear SUV axles.
[0105] The Eddy current sensor (142) shows a decrease in frequency from the eddy currents caused by the SUV front and rear wheel assemblies (143) and detects the trailer wheel assembly (144) with the polyester tire. This is where the frequency decreased and then returns to the base line frequency. In contrast the Ferromagnetic sensor does not detect the trailer wheel.
[0106] Eddy Current Sensor This embodiment has two Eddy Currents Effect sensor designs. The first design has a series of rectangular segments that are equal in size (FIG. 2). The second design has a series of rectangular segments that are not all equal in size. The significant difference in this design when compared to a Ferromagnetic Loop Sensor is the Eddy Current Sensor is designed to have the vehicles travel over the sensor parallel with the dominant primary flux fields. The Ferromagnetic Loop Sensor is designed to have the vehicles travel over the sensor perpendicular to the dominant primary flux fields.
[0107] Each Eddy Current Sensor is made of multi-stranded copper electrical wire. The wire is installed on the top of the roadway or in the roadway in the surface. The Eddy current sensor has multiple rectangular wire coils connected in series. The number of wire turnings can range from 2 turns up to 6 turns to achieve the desired inductance of the sensor (200). This unique series of rectangles are on a single circuit. The rectangles provide multiple electrical flux thresholds for wheel assembly detection as vehicles pass over the sensors installed on or in the roadway FIG. 2 (201).
[0108] The first design type of Eddy Current Effect sensor design consists of a multiple rectangular segments uniform in size connected in series in a single circuit (202). The number of rectangles in the series can be increased or decreased in the sensor to change the width of the sensor in order to provide detection the full width of the travel lane and the sensor width is the of the sum of rectangular loop segments (203). The length of the loop (204) can be increased to increase the data signature sample collected from the sensor. The length for each sensor is directly related to the sample length, since the sample rate of the loop detector occurs on a fixed time basis as the vehicles pass over the sensor. The increased number of samples is beneficial for wheel detection. When the vehicle speeds increase, the length of the loop can be increased by increasing the length (204) of the loop the number of samples or signature lengths from the wheel assembly is increased. The width (203) of each rectangular segment can range from 14 inches to 24 inches wide.
[0109] The length of the rectangular loop segments (204) can range from 12 inches to 36 inches long. Again, all the rectangular segments are equal in size (202) in the sensor.
[0110] The first Eddy current sensor design is described above and is illustrated in FIG. 2. The preferred method of installation is at a depth of 3 to 6 inches below the roadway (205). The preferred width of the rectangular segment (203) is 22 inches. The preferred number of wire wound turnings (200) is five (5). The preferred length (204) of this sensor is 24 inches long. The direction of travel for the vehicles is parallel to the primary flux fields of the sensor (207).
[0111] The first design is described above and illustrated in FIG. 2. The sensor can include six (6) segments and have an overall width of 11 feet and is preferably used in lanes that are 12 feet to 13 feet wide. The sensor can include five (5) segments (202) and have an overall width of 9.16 feet (203) and used in narrow lanes that are 10 feet wide.
[0112] The preferred width of the segments (202) is 22 inches. The length (204) of each segment can vary from 12 inches to 36 inches. The preferred length (204) is equal to the length of the Ferromagnetic effect type sensor being used in combination with the Eddy Currents effect sensor for the Smart Loop Treadle. The preferred method of installation is at a depth of 3 to 6 inches below the roadway (205). The preferred number of wire wound turnings (200) is five (5). The preferred loop windings are 14-gauge multi-stranded copper wire (206). The geometry and size of the rectangular segments are designed to optimize the Eddy Currents from the wheel assemblies and minimize the Eddy Currents from the chassis of the vehicles when they pass over the sensor.
[0113] FIG. 2A illustrates the detection signature using the above Eddy Current Sensor with 6 rectangular segments (22 inches wide by 24 inches long), and five wire turnings. The signature is from a Motorcycle have polyester reinforced tires. The signature of the loop (210) has two sharp decreases in the frequency from the front wheel (211) and from the rear wheel (212).
[0114] The second Eddy Current sensor design has rectangular segments that are unequal in size FIG. 2B. Toll plazas and divided highways can have a variety of lane widths. They can range in width from narrow lanes only 8 feet wide to lanes designed for extra wide loads that are 16 feet wide. The second Eddy Current sensor design can be used for this Toll plaza application and secondary roadways for planning applications. This design contains a combination of rectangular segments (details 220 and 221) having different widths. The use of different segment widths provides adjustment in the sensors overall width (222). This allows the sensor overall width to be adjusted to provide full detection coverage of the lane. The length of the sensor (223) can be adjusted for the application. The preferred method of installation is at a depth of 3 to 6 inches below the roadway surface (224). This Eddy current sensor example has five (5) wire turnings (225).
[0115] This design can be adjusted to fit different lane width by changing the number of segments and the width of the segments. The number of wire turning can be changed to change the field strength of the loop segments. The number of turning changes the inductance and sensitivity of the loop circuit.
[0116] FIG. 2B the Eddy Currents Effect sensor has a combination of four (4) large rectangular segments (220) and two smaller rectangular segments (221). This sensor has four (4) 22 inches wide by 16 inches long rectangular segments (220) and two (2) segments 15 inches wide by 16 inches long (221). The number of these segments can be reduced to reduce the overall width for narrow lanes or can be increased for wider lanes.
[0117] The length of the sensors (223) can also be increased to increase the sample length. The number of wire wound turnings (225) can be increased or decreased to adjust the sensor inductance. The FIG. 2B illustrates four (4) wire turnings (225). The loop windings are made using 14 gauge multi-stranded copper wires (226).
[0118] FIG. 2C is an example of an Eddy Current sensor with unequal segments that is designed for a lane 11 feet wide. This Eddy Currents Effect sensor has a combination of four (4) large rectangular segments (230) and one smaller rectangular segment (231). The sensor has four (4) 22 inches wide by 16 inches long rectangular segments (230) and one (1) segments 20 inches wide by 16 inches long (231). The preferred method of installation is at a depth of 3 to 6 inches (232) below the roadway. This preferred number of wire turnings for this sensor is (233) is five (5). This sensor is 10 feet wide (234).
[0119] FIG. 2D is an illustration of a Test sample signature using the Eddy Currents sensor (240) with unequal segments as described in FIG. 2C. The start of the vehicle and the front wheel (241) caused a decrease in frequency and the rear wheel (242) caused a decrease in frequency. The sensor returned to its resident frequency (243) at the end of the pickup truck. The trailer axle was detected (244) and the sensor returned to the resident frequency baseline at the end of the trailer (245).
[0120] In FIG. 2E the following Eddy Current Sensors have segments that are equal. The width and length of the segments in the three sensors are different. They were compared since they have different inductance and different resident frequencies.
[0121] Eddy Current sensor (251) with segments that are equal with seven (7) segments 18 inches wide by 30 inches long having 4 wire Turnings.
[0122] Eddy Current sensor (255) with segments that are equal with seven (7) segments 18 inches wide by 18 inches long having 4 wire Turnings.
[0123] Eddy Current sensor (259) with segments that are equal with seven (7) segments 22 inches wide by 18 inches long having 4 wire Turnings.
[0124] Three Eddy Current Effect sensors were compared in FIG. 2E. The vehicle sample is an SUV towing a single axle utility trailer. The sensor (251) is constructed using 7 segments that were 18 inches wide by 30 inches long having 4 wire turnings and had a base frequency of 65,234 Hertz. The start of the SUV front wheels were detected at (252) frequency decreased to 65,094 Hertz. The end of the SUV and start of the trailer was detected at (253) and the frequency was 65,232 Hertz. The non-steel belted trailer wheel was detected at (254) and the frequency decreased to 65,191 Hertz.
[0125] The sensor (255) is constructed using 7 segments that were 18 inches wide by 18 inches long having 4 wire turnings and had a base frequency of 64,930 Hertz. The start of the SUV was detected at (256) and the frequency decreased to 64,822 Hertz. The end of the SUV and start of the trailer was detected at (257) and the frequency was 64,933 Hertz.
[0126] The non-steel belted trailer wheel was detected at (258) and the frequency decreased to 64,888 Hertz.
[0127] The sensor (259) is constructed using 7 segments that were 22 inches wide by 18 inches long having 4 wire turnings and had a base frequency of 64,371 Hertz. The start of the SUV was detected at (260) and the frequency decreased to 64,225 Hertz. The end of the SUV and start of the trailer was detected at (261) and the frequency was 64,368 Hertz. The non-steel belted trailer wheel was detected at (262) and the frequency decreased to 64,316 Hertz.
[0128] The FIG. 2F is an illustration of an Eddy current sensor with unequal segments. This sensor has seven (7) segments consisting of four (4) segments 22″W by 16″ L (260) and three (3) segments 15″W by 16″L (261). This sensor has five wire turnings (262). The sensor is installed below the surface of the roadway (263) at a nominal depth of 3 to 6 inches. The wire is 14 gauge multi-stranded copper (264). This sensor has an overall width of 11 feet and 1 inch (265) and can be used in a lane 12 feet wide. This sensor has an overall length of 16 inches (266) and this length could be increased to a length of 30 inches as in the previous signature example (FIG. 2E, detail 251).
[0129] The FIG. 2G illustrates a signature of a SUV towing a single axle trailer. The tires on the SUV are steel belted reinforced and the trailer tires are non-steel belted. All four signatures are from this same vehicle and it illustrates the Ferromagnetic Sensor increases in frequency when the vehicle passes over the sensor and the Eddy Current sensor decreases in frequency when the vehicle passes over the sensor. The Ferromagnetic Effect tire sensor (270) has a base frequency. The frequency of the sensor increases when the front tire of the SUV passes over the sensor increasing the frequency to 65,322 Hertz (271). This Ferromagnetic sensor was the 2-4-4-2 design. The rear axle of the SUV passes over the Ferromagnetic Effect sensor increasing the sensor frequency (272). The SUV was towing a trailer. The trailer tires were non-steel belted and were not detected in area (273) by the Ferromagnetic sensor.
[0130] The Eddy Currents sensor (274) has a base frequency. The start of the SUV (275) was detected and the frequency decreased. The end of the SUV (276) and start of the trailer was detected. The non-steel belted trailer wheel was detected (277) and the frequency decreased. This Eddy Current sensor contained six segments 22″ Wide by 16″ Long with 5 turnings.
[0131] The Eddy Currents sensor detail 278 has a base frequency and is constructed of four (4) segments 22″ Wide by 16″ Long and three (3) segments 15″ Wide by 16″ Long as described in FIG. 2A. The start of the SUV (279) was detected and the frequency decreased. The end of the SUV (280) and start of the trailer was detected. The non-steel belted trailer wheel (281) was detected and the frequency decreased.
[0132] The Eddy Currents sensor (282) has a base frequency and is constructed of four (4) segments 22″ Wide by 12″ Long and three (3) segments 15″ Wide by 12″ Long as described in FIG. 2A. The start of the SUV (283) was detected and the frequency decreased. The end of the SUV (284) and start of the trailer was detected. The non-steel belted trailer wheel (285) was detected and the frequency decreased.
[0133] In FIG. 2H illustrates an Eddy current sensor having a different the number of turnings that include the range of 3-6-5-4-5-6-3 (290). This is an alternate winding for the Eddy current sensor that forms rectangular loop circuits in a series. This is in contrast to the original Prior Art bicycle loop that used a serpentine winding. When the sensor is formed using a serpentine wrapping the number of turns increases are uniform for all the rectangles. This Eddy current sensor windings alternate from clockwise turnings to counter clockwise turnings (291) forming a series of rectangular loops circuits. The width of each rectangle is equal in size (292). The lengths of the rectangles are all equal (293). The advantage of this wire winding design is it permits the number of turnings of each rectangle to be increased without adding turnings to the whole sensor. This is illustrated in the cross section (290).
[0134] This winding design allows for the strongest field to occur in both wheel paths in the lane of the roadway. Typical range for trailers axles is from 5 feet to 9 end to end and this sensor design provides the fields to be strength in these areas. The overall width (292) of the sensor is 11 feet and the length can be adjusted to provide full lane coverage. The length of the sensor is 2 feet (293). The direction of travel is parallel to the strongest field (294).
[0135] Ferromagnetic Sensor There are three sensor designs that optimize the Ferromagnetic effect sensor these designs that have unique wire turnings. These three designs can have the width increased or decreased to provide detection across the full width of the lane. FIG. 3 illustrates a Ferromagnetic Sensor designated as a 2-4-4-2 configuration (2 turns-4 turns-4 turns-2 turns). The sensor is installed in the travel lane and can vary in width from 8 ft. to 16 ft. wide (300). The sensor is designed to have both left and right wheels of a vehicle pass over the tire assembly sensor. The wire turnings are installed on or near the surface of the roadway using 14-gauge multi-strand copper wires (301) for the turnings. The typical depth (302) of the installation is 2 inches below the road surface.
[0136] These three designs can have the length of the sensor increased or decreased from leading edge to trailing edge to increase or decrease the length of the vehicle tire assembly signature. These sensors can also have the number of windings increased to adjust the inductance of the sensor this aids in balancing the inductance of the sensor with the length of the lead-in cable. The width of the sensor is measured perpendicular to the direction of travel (300). The length of the sensor is measured parallel to the direction of vehicle travel (303).
[0137] The important functions for these designs are their response to the ferromagnetic effect from the tire assemblies and their minimum influenced by the eddy currents from the vehicle chassis.
[0138] The present invention first sensor design can have a series of rectangular loops that can be longer than the diameter of the wheel assembly being detector. FIG. 3 contains three rectangular loops. The sensor is designed to be extended into a series connected circuit arrangement of multiple uniform rectangular loop segments (304). Increasing the number of rectangular segments will directly increase the length in time of the sample size when a vehicle wheel assembly passes over the sensor in the direction of travel (305). This increase in the number of rectangular loops in the series does not change the field height of the sensor. This is a very important design function since the sensors field height is optimized to detect wheel assemblies and not the chassis of vehicles.
[0139] The FIG. 3 illustrates the wheel sensor that contains multiple rectangular loops connected in series (304). This example has the designation of (2-4-4-2) and consists of three rectangular loops connected in series as a single circuit. The rectangular loops alternate the windings from clockwise to counter clockwise or from counter clockwise to clockwise depending on the layout requirements of the lead-in installation in the travel lane. Each of the rectangular loops are 11 ft. wide (300) having a nominal length of four (4) inches long (303). The size of each rectangular loop can vary in length from 3 to 6 inches but are all segments are uniform in length. This loop can have additional wire windings/turnings in example the (3-6-6-3) has three rectangular loops that are illustrated in (FIG. 3A detail 310) each loop has three (3) turnings. The series of the three loops provide four flux thresholds (311). The FIG. 3B (320) illustrates the Ferromagnetic sensor 4-8-8-4 windings having four (4) wire turns (321) in a series in a single circuit having three rectangular loops (322). The direction of travel for the vehicles is perpendicular to the primary flux fields of the sensor (323).
[0140] The preferred size of the 3-6-6-3 (FIG. 3A) in a travel lane that is 13 feet wide has a width (311) of 12 feet and overall length (312) of 12 to 13 inches. The windings for the three rectangular loops are clockwise—counter clockwise—clockwise and are all equal (313). FIG. 3C illustrates a vehicle signature from a pickup truck using the 2-4-4-2 Ferromagnetic sensor (330). The front wheel (331) and rear wheel (332) assemblies cause an increase in the frequency of the sensors when the vehicle travels over the sensor. FIG. 3D illustrates a vehicle signature traveling over the 3-6-6-3 Ferromagnetic sensor (340). The front wheel (341) and rear wheel (342) assemblies cause an increase in the frequency of the sensors when the vehicle travels over the sensor.
[0141] FIG. 3E illustrates an example of four rectangular loops (350) in a series in a single circuit. The plan views of the sensors wire turnings are alternated from clockwise direction to a counter clockwise direction. These loops have the following design designations (351) Ferromagnetic 2-4-4-4-2. FIG. 3F illustrates an example of five rectangular loops (360). These loops have the following design designations (361) Ferromagnetic 2-4-4-4-4-2. FIG. 3G illustrates an example of six rectangular loops (370). These loops have the following design designations (371) Ferromagnetic 2-4-4-4-4-4-2. The number of flux field thresholds (372) increases with the length of the sensor. This design optimizes the ferromagnetic effect to detect the attributes of wheel assemblies.
[0142] Each flux field is low and minimizes the influence by eddy currents from the vehicles chassis when the length of the sensor is increased.
[0143] FIG. 3H illustrates a signature from a five axle truck the is traveling over a Ferromagnetic Sensor 2-4-4-4-4-4-2 (380) the front wheels cause an increase in the frequency and a peak (381) is present in the signature. The second set of wheels cause an increase in frequency and a peak (382) is present in the signature. The third set of wheel assemblies cause an increase in frequency and a peak (383) is present in the signature. The fourth set of wheel assemblies cause an increase in frequency and a peak (384) is present in the signature. The fifth set of wheel assemblies cause an increase in frequency and a peak (385) is present in the signature.
[0144] This ferromagnetic sensor design using a series of rectangular loops that allows for the increase or decrease of wire turnings in order to increase or decrease the inductance of the sensor as required. The FIG. 31 illustrates the above ferromagnetic sensors with additional wire turnings. The same pattern alternating pattern of clockwise and counter clockwise of wire turning for the rectangular series of loops is used. These loops have the following design designations Ferromagnetic sensor 3-6-6-3 (390), Ferromagnetic sensor 3-6-6-6-3 (391), Ferromagnetic sensor 3-6-6-6-6-3 (392), and Ferromagnetic sensor 3-6-6-6-6-6-3 (393). The number of flux field thresholds (394) increases with the length of the sensor. The vehicles direction of travel over the sensors is indicated as (395).
[0145] The second design has a unique winding FIG. 3J illustrates an alternate design that uses a different winding method (400) to provide a cross section of the wire turnings (401) having the designation (2-3-2-3-2). The wire turnings are installed on or near the surface of the roadway using 14-gauge multi-stranded copper wire. This sensor is a single circuit consisting of rectangular loops. The width (402) of the loop can be increased or decreased to provide detection across the lane perpendicular to the direction of travel. Each of the rectangular segments (403) has a nominal length of 4 inches and all the segments are the same size resulting in a nominal length (404) of 16 inches. The size of each rectangular loop can vary in length from 3 to 6 inches but are all segments are uniform in length. These sensors are installed on or near the surface of the roadway. In FIG. 3J (405) indicates the direction of travel for vehicles passing over the sensor.
[0146] The Ferromagnetic sensor (2-3-2-3-2) can be doubled in length using a single circuit. The doubled sensor results in a Ferromagnetic sensor (2-3-2-3-2-2-3-2-3-2) this double length sensor is illustrated in FIG. 3K (410) and has a nominal length (411) of 36 inches. This doubles the sample length when compared to the Ferromagnetic sensor (2-3-2-3-2) however the sensor cannot be increased by individual segments because of the alternating windings pattern (412). The increase number of samples is beneficial as the vehicle speeds increase. The increase in the number of rectangles does not degrade the optimization of the Ferromagnetic effect. The width of the sensor (413) can be increased or decreased to provide detection across the lane perpendicular to the direction of travel (414).
[0147] FIG. 3L illustrates a signature from a Ferromagnetic Sensor 2-3-2-3-2 (420) from a two axle truck. The frequency increases when the front and rear wheels pass over the sensor (421). The rear axle (422) has dual tires and this is reflected in the larger change in frequency.
[0148] Lane Position Sensor
[0149] The Lane Position sensor has two loop circuits each loop circuit has a single wire rectangular loop having from 2 to 6 wire turnings. In FIGS. 4 and 4A each of the loops are 6 ft. wide by 6 ft. long. The two loop circuits are identical is size and can be adjusted in size to provide full coverage in one lane. FIG. 4 illustrates the Lane Position sensor having the loop circuits partially overlapping and providing detection across the entire width of the lane (430). The placement of the first loop circuit (431) is biased to the left of the travel lane. The second loop circuit is biased to the right side of the lane (432). The placement of these loops provides the logic for the vehicle signatures to determine the position of the vehicle as it travels in the lane.
[0150] The Lane Position sensor design provides two signatures from the same vehicle that is traveling in the lane. The two signatures are used to determine the vehicle path of travel in the lane. FIG. 4 illustrates the Lane Position sensor. The present invention Lane Position sensor has two rectangular loops (433) that are configured in a single lane of travel.
[0151] This combination of two loops provides the detection to determine the position of the vehicle in the lane if a vehicle is in the left side of the lane, center of the lane, or right side of the lane. This information is useful in open road tolling applications. The additional information can be used to associate a vehicle lane position with the electronic toll tag reading, and vehicle photo association. This loop configuration is also beneficial for motor cycle detection since they usually travel in the left or right wheel path of the roadway and not the center of the lane. The combinations of the two loops can also detect wide vehicles traveling in a single lane.
[0152] The two loops can be installed using a diamond pattern by having the rectangular loops rotated 45 degrees. FIG. 4A illustrates this installation of two loop circuits partially overlapping (440). This Lane Position sensor detects the travel position of the vehicle in the lane. The Lane Position sensor provides detection across the entire width of the lane (441).
[0153] FIG. 4B illustrates the two signatures from a SUV traveling on the left side of the lane. These loops respond to the eddy current effect and the frequency of both loops decrease when the vehicle passes over the sensors. The loop on the left side of the lane has a greater decrease in the frequency (450) from the vehicle traveling on the left side of the lane. The loop on the right side of the lane has less frequency change (451).
[0154] FIG. 4C illustrates the two signatures from a SUV traveling in the center of the lane. These loops respond to the eddy current effect and the frequency of both loops decrease equally (460) when the vehicle passes over the sensors.
[0155] FIG. 4D illustrates the two signatures from a SUV traveling on the right side of the lane. These loops respond to the eddy current effect and the frequency of both sensors decrease when the vehicle passes over the sensors.
[0156] The loop on the right has a greater decrease in the frequency (470) from the vehicle traveling on the right side of the lane. The loop on the left side of the lane has a smaller decrease in the frequency (471).
[0157] While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, uses and/or adaptations of the invention following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the invention pertains and as maybe applied to the central features hereinbefore set forth, and fall within the scope of the invention and the limits of the appended claims. It is therefore to be understood that the present invention is not limited to the sole embodiment described above, but encompasses any and all embodiments within the scope of the following claims
