WO2012038955A1

WO2012038955A1 - Piezoelectric-based weigh-in-motion system and method for moving vehicles

Info

Publication number: WO2012038955A1
Application number: PCT/IL2011/000741
Authority: WO
Inventors: Haim Abramovich; Charles Milgrom; Eugeny Harash; Lucy Edery Azulay; Uri Amit; Gregory Klein
Original assignee: Innowattech Ltd.
Priority date: 2010-09-20
Filing date: 2011-09-19
Publication date: 2012-03-29

Abstract

A piezoelectric vehicle weight-in-motion system having piezoelectric sensors, situated substantially perpendicular to the direction of traffic on a motorway, wherein each of said piezoelectric sensor comprises at least one piezoelectric element configured to produce electrical signal indicative of the force applied on said sensor by a vehicle passing over said sensor; and a processor, receiving signals from said piezoelectric sensors, wherein said processor is capable of determining the speed in which said vehicle passed over said sensors and the load of said vehicle while said vehicle is traveling at normal traffic speed.

Description

PIEZOELECTRIC-BASED WEIGH-IN-MOTION SYSTEM AND METHOD

FOR MOVING VEHICLES

FIELD OF THE INVENTION

The present invention relates to piezoelectric applications. In particular, the present invention relates to a piezoelectric system and method for measuring weight of passing vehicles while the vehicles travel at any traffic speeds.

BACKGROUND OF THE INVENTION

Truck load awareness assists in preventing truck overloading, a common safety hazard which may be heavily fined. Overweight trucks both accelerate deterioration of the roadway and are a safety hazard because they increase the braking distance of trucks.

Truck overload prevention is a common practice in industries that manufacture or move bulk items, such as in goods transport, mines, quarries, garbage dumps, recycling centers or the like. Static electronic, mechanical or electro-mechanical truck scales and weigh bridges are usually mounted on a concrete foundation and are used to weigh entire vehicles and their contents. By weighing a loaded vehicle, the weight of the load carried by the vehicle can be calculated. Usually, the weight of the vehicle carrying the goods is known, or can be ascertained quickly according to vehicle type and model. A truck can have one or more of its axels overloaded even though the total weight of the truck is within legal limits.

Weigh bridges have been largely supplanted by simple and thin electronic weigh cells, over which a vehicle is slowly driven. A computer records the output of the cell and accumulates the total vehicle weight. By measuring the force of each axle it can be assured that the vehicle is within statutory limits, which typically will impose a total vehicle weight, maximum weight within an axle span limit and an individual axle limit. The former two limits ensure the safety of bridges while the latter protects the road surface.

Determining the weight of a loaded truck may be used for charging passing vehicles according to the weight they carry. Governmental and law enforcement authorities use the gross vehicle weight to determine whether the vehicle is safe to travel on the public highway. Truck weigh stations operated by trained personnel are commonly used for determining whether vehicles meet weight restrictions. When weight violations are detected, vehicles and drivers may be pulled off the road or fined accordingly.

Vehicle weight enforcement requires that truck weigh stations be built at predefined locations, and that trained personnel operate these stations. It also causes potential delays in delivery schedules, because enforcement requires that driving vehicles be stopped in at least one of a plurality of road intercepts, and go through a lengthy manual process.

Some details regarding energy harvesting and piezoelectric generators may be found in the following patent applications which are incorporated herein by reference:

• US20100045111 "MULTI-LAYER MODULAR ENERGY HARVESTING APPARATUS, SYSTEM AND METHOD";

• US20090195226 "Power Harvesting From Apparatus, System And Method";

• US20090195124 "ENERGY HARVESTING FROM AIRPORT RUNWAY";

• US20090195122 "Power Harvesting From Railway; Apparatus, System And Method";

• WO2009098676 "ENERGY HARVESTING"; and

• WO2009098673 "POWER HARVESTING FROM RAILWAYS; APPARATUS SYSTEM AND METHOD".

SUMMARY OF THE INVENTION

Exemplary embodiments of the current invention provide automated system and method for enforcing vehicle weight restrictions in motion without disturbing road traffic.

One aspect of the invention is to provide a piezoelectric vehicle weight-in-motion system comprising: at least two rows of piezoelectric sensors, situated such that the rows are substantially perpendicular to the direction of traffic on a motorway, and separated by at least 1 m, wherein each of said rows comprises at least a right-wheel cluster of sensors and a left-wheel cluster of sensor, and wherein each of said cluster comprises at least two piezoelectric sensors connected in parallel, wherein each of said piezoelectric sensor comprises at least one piezoelectric element configured to produce electrical signal indicative of the force applied on said sensor by a vehicle passing over said sensor; and a processor, receiving signals from said piezoelectric sensors, wherein said processor is capable of determining the speed in which said vehicle passed over said sensors and the load of said vehicle while said vehicle is traveling at normal traffic speed.

In another aspect of the invention the system is configured with two rows of piezoelectric sensors, situated such that the rows are substantially perpendicular to the direction of traffic on a motorway, and separated by at least one meter, wherein one of said rows comprises a right-wheel cluster of sensors and the second row a left-wheel cluster of sensor, and wherein each of said cluster comprises at least two piezoelectric sensors connected in parallel, wherein each of said piezoelectric sensor comprises at least one piezoelectric element configured to produce electrical signal indicative of the force applied on said sensor by a vehicle passing over said sensor; and a processor, receiving signals from said piezoelectric sensor.

In some embodiments said piezoelectric element produces said electrical signal by reaction to compression forces with active D3,3 piezoelectric effect, generating signal indicative of the applied force.

In some embodiments said piezoelectric sensor comprises: a box; a cover; a plurality of piezoelectric elements disposed between said box and said cover, wherein said piezoelectric elements are connected in parallel and are configured to produce electrical signal indicative of compressive force applied between said cover and said box.

In some embodiments said plurality of piezoelectric elements are arranged in a single layer.

In some embodiments said plurality of piezoelectric elements are arranged in a single row.

In some embodiments at least one of said box and said cover is made of aluminum.

In some embodiments at least one sensor measures approximately 400 mm long, 40 mm wide and 60 mm deep.

In some embodiments each of the clusters of sensors comprises at least three sensors.

In some embodiments the system comprises a camera capable of capturing an electronic image of said passing vehicle and transferring said capture image to said compressor, wherein said processor is capable of determining the license plate number of said passing vehicle and associating the load of said passing vehicle to said determined license plate number.

In some embodiments the system comprises a vehicle detection unit capable of detecting a passing vehicle and transferring information indicative of said passing vehicle to said compressor, wherein said processor is capable of using said transfer information to associate all signals generated by said sensors in response to a specific passing to said specific passing vehicle.

In some embodiments the system comprises a speed detection unit capable of determining the speed of a passing vehicle and transferring information indicative of the speed of said passing vehicle to said compressor, wherein said processor is capable of using said transfer information to calculate the loads on wheels of said passing vehicle.

In some embodiments the processor is capable of determining imbalanced loading of said passing vehicle.

In some embodiments the processor is capable of determining overloading of said passing vehicle.

In some embodiments the system comprises: a remote server; and a communication unit, connected to said processor and capable of transmitting information indicative of said passing vehicle to said remote server.

In some embodiments the system comprises: at least one piezoelectric generator capable of generating electric power when force is applied to said piezoelectric generator by a wheel of a vehicle passing over said generator; an energy conversion unit converting said generating electric power to useful electric energy; and an energy storage, capable of storing said useful electric power and supply energy to power said system.

Another aspect of the invention is to provide a method for determining the weight of passing vehicles while in motion using piezoelectric generators comprising the steps of: positioning at least a first row of piezoelectric sensors and a second rows of piezoelectric sensors substantially parallel to each other, perpendicular to the direction of traffic on a roadway lane, and spatially separated; generating electric signals from said at least two rows of piezoelectric sensors in response to forces applied by the wheels of a passing vehicle over said piezoelectric sensors; determining the speed of said passing vehicle from the time difference between a signal generated by at least one sensor in said first row and a signal generated by at least one sensor in said second row; and determining the weight of said passing vehicle from said generated signals taking into account said determined speed of said passing vehicle.

Another aspect of the invention is to provide methods of implementing piezoelectric sensors in a roadway.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings:

Figure 1 schematically illustrates a block diagram of an exemplary embodiment of a piezoelectric vehicle WIM system according to an exemplary embodiment of the current invention.

Figure 2A shows an isometric external view of a narrow piezoelectric generator according to an exemplary embodiment of the current invention.

Figure 2B schematically depicts an isometric internal view of the housing of a narrow piezoelectric generator, accommodating a plurality of piezoelectric elements arranged in two horizontal rows according to an exemplary embodiment of the current invention. The rows of disks can be parallel or in a zigzag pattern.

Figure 3A schematically illustrates a cross-sectional view of a road showing a concrete casing serving as a placeholder for two narrow generators according to an exemplary embodiment of the current invention.

Figure 3B schematically depicts a cross section of a road illustrating how generators may be placed within a casing below the surface of the road according to another exemplary embodiment of the current invention.

Figure 4 depicts a schematic top view of a road lane embedded with two succession casing clusters according to an exemplary embodiment of the current invention.

Figure 5 schematically depicts vies of a WIM sensor/generator, according to an exemplary embodiment of the current invention.

DETAILED DESCRIPTION OF THE SELECTED EMBODIMENTS

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

The terms "comprises", "comprising", "includes", "including", and "having" together with their conjugates mean "including but not limited to". The term "consisting of" has the same meaning as "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

In discussion of the various figures described herein below, like numbers refer to like parts. The drawings are generally not to scale. For clarity, non-essential elements were omitted from some of the drawing.

Various embodiments of the piezoelectric weigh-in-motion (WIM) system and method for moving vehicles are disclosed hereinbelow. Embodiments are based on signal extraction from piezoelectric elements embedded into roads.

Prior applications focus on energy harvesting from compression of piezoelectric elements, whereas the embodiments described herein further enable a weigh in motion system for measuring the weight of passing vehicles as they travel on the road. Embodiments described herein enable precise vehicle weight measurement when the vehicle is in motion, regardless of the speed in which the vehicle travels. Thus, with this system there is no need to stop the vehicle, slow it considerably, or take it off the road to a dedicated weigh bridge.

Embodiments of the system disclosed herein may be incorporated beneath an asphalt road and be covered with a layer of asphalt, such that the road is completely leveled despite the presence of the piezoelectric generators or sensors. This prevents the creation of cracks and leveling differences in the road as a result of road wear out, which may destroy the integrity of the piezoelectric elements over time. Alternatively the system may be incorporated beneath the surface of a concrete road and covered with grouting.

Alternatively weighing system may be installed above the road's surface or such that the sensor is at the level of the road's surface.

Furthermore, the system's components, such as its control unit and its communication unit, may optionally operate on energy harvested from the piezoelectric elements, without a need for an external power source.

In various embodiments, piezoelectric generators are embedded into roads and respond to mechanical load caused by passing vehicles. Piezoelectric energy may be generated by compression forces resulting from the combination of speed and weight of passing vehicles. With proper calibration, every amount of generated energy can be mapped to values representing a combination of vehicle weight and velocity. It is an optional advantage of the current invention that it may operate at both high and low speeds of the passing vehicles.

Figure 1 schematically illustrates a block diagram of an exemplary embodiment of a piezoelectric vehicle WIM system 100. Although presented in the block diagram as separate blocks, the system may optionally be integrated into subunits or a stand-alone system.

WIM system Embodiment 100 comprises piezoelectric generators/sensors 110 (two such generators - 110A and HOB are seen in the exemplary embodiment). Generators 110 are connected to at least one energy conversion and signal extraction unit 120, at least one processor 130, an optional data storage unit 140, and one or more optional: display units 160; communication units 150, and optional energy storage units 170.

Piezoelectric generators/sensors 110 comprises piezoelectric elements embedded into the road, for example as described in the prior art of piezoelectric power harvesting. Generators 110A and HOB may be used for generating and optionally storing power harvested off piezoelectric elements within optional energy storage unit 170. Energy harvested from piezoelectric generators 110A and HOB and stored in energy storage unit 170 may serve as an independent power source for the vehicle WIM system 100, and optionally for other uses such as, but not limited to powering surrounding traffic signs and lights. Energy storage unit 170 may further be connected to an external power source or external power users such as external load 180, for example a main power grid. In some exemplary embodiments, excess energy generated by system 100 may be transferred to the external load 180 such as main electrical grid for distribution. In some exemplary embodiments, external load/power source 180 such as main electrical grid may supply energy to system 100 when its energy consumption is greater than its energy generation and receive energy from system 100 when its energy generation is grater than its energy consumption.

Processor 130 is capable of analyzing data received from signal extraction unit 120 regarding the amount of harvested energy from a passing vehicle, and translates the data to determine the speed and weight of the passing vehicle passing. Optionally, the processor uses configurable parameters to analyze and translate the data. Data may be stored in a data storage unit 140.

Optionally, processor 130 may verify that the translation is accurate or legitimate according to optional external units, for example camera 190. Camera 190 may be used to obtain a picture or a license ID of passing vehicles.

Data received from optional external speed detection unit 192 for detecting speed of passing vehicles may also be used by processor 130. Optionally, speed detection unit 192 may be a Doppler-based radar, laser speed trap or any other vehicle speed measurement tool which suits requirements. Additionally, alternatively and optionally, a plurality of generators 110 are embedded in the road at distances along the direction of travel (as seen for example in figure 4. In these embodiments, speed of travel may be extracted from the known distance between the generators and the measured time difference between signals generated by the same wheel as it passes a first and a second generator.

Data is typically recorded and stored in a central data storage unit 140 for further reference. Processor 130 is optionally further capable of sending analyzed data to remote stations by using a communication unit 150 optionally connected to a remote server 155 via a wired or a wireless communication channel such as but not limited to phone, radio or cellular communication. Processor 130 may use optional display units 160 for displaying analyzed data to users. Display units 160 may be for example and without limitation computer screens, laptops, PDAs, cellular phone screens, printed sheets, integrated LCD screens (e.g. Thin Film Transistors, touch screens) or the like. In some applications, law enforcing unit such a police patrol vehicle or a roadside checkpoint may be alerted when law violation or hazardous condition is detected. This may include one or combination of: excessive load, uneven or imbalanced loading, above limit travel speed, uneven tire inflation or such like violations and hazardous conditions. Alert may be issued locally, for example using display 160, or remotely for example and without limitation using the communication unit 150.

Data storage unit 140 may be a database, or any other data storage means that suits requirements. Optionally, data storage unit 140 is mobile, or located at a remote location not residing in physical proximity to generators 110A and HOB, processor 130 or other components of system 100.

Optionally, each piezoelectric WIM system 100 may have its own dedicated data processor 130, storage unit 140 and display system 160, for processing, storing and displaying data locally. Alternatively, a number of WIM systems 100 may share processors 130, storage units 140 and display unit 160 or communication unit 150.

It should be noted that in some exemplary embodiments system 100 may supply power for its operation and may be used without connection to an external power source 180, relaying on energy generated by generators 110, converted to useful energy by energy conversion unit 120 and stored in energy storage 170.

It should be noted that system 100 may be used with piezoelectric sensors that do not generate enough energy for operating the system, or with sensors that require bias for their operation such as resistive strain gauges. In this case, the external load 180 is replaced with a power source such as main electrical power or a renewable power source such as wind or solar power source, or a battery such as rechargeable or replaceable battery.

For example, piezoelectric transducer made of piezoelectric polymers may produce sufficiently large signal for operate as sensors, but not efficient generators for energy harvesting. Such sensors may be cheaper to make. Similarly, transducers having small quantity of piezoelectric material may be used as sensors only. The mechanical construction of the sensors' case may be design such that mechanical load is primarily supported by the structure of the case such that only a portion of the stress is applied to the piezoelectric material, thus reducing the generated energy while protecting the piezoelectric from being overloaded and optionally reducing its size.

Optionally, system 100 may comprise a vehicle detection unit 193. Optional vehicle detection unit 193 may be an electromagnetic induction loop as known in the art. Vehicle detection unit 193 remove the ambiguity of multi-axial vehicles such as trucks, pickup-tracks and trailers and ensures that signals caused by a specific passing vehicle is correctly associated with a single vehicle. Optionally, the optional camera 190 performs this function when used with image recognition software.

It should be noted that electrical signals generated by piezoelectric sensors in response to a passing vehicle are large and easy to detect and/or digitize with an ADC (Analog to Digital Converter) and do not require amplification. For example, voltage of few volts or even up to 100 volts may be generated. These signals may be transferred over electrical wires from sensors 110 to signal extraction electronics front end 120 which may be positioned near the road's curb or roadside structure without the use of signal amplification.

GENERATORS / SENSORS

Reference is now made to Figures 2A and 2B showing an external view and an internal view respectively of a narrow piezoelectric generator 200, comprising a housing 210 with a cover 212.

Figure 2A shows an isometric external view of a narrow piezoelectric generator 200 according to an exemplary embodiment of the current invention.

The figure schematically shows the housing 210 for accommodating a plurality of piezoelectric elements (not shown in this figure), cover 212 and screws 214A - 214G arranged next to each other in a horizontal line according to an exemplary embodiment of the current invention. Preferably, screws 214 run from the cover 212 to bottom 216. Preferably, heads of screws 214 are within recesses in cover 212 so as not to protrude above the surface of cover 212. This allows transfer of load applied to cover 212 to be transferred to the piezoelectric elements with body 210 of narrow piezoelectric generator 200.

Screws serve as fastening means and for ensuring that cover 212 is in contact with the embedded piezoelectric elements 220 (not seen in this figure). Other fastening means that suits requirements may alternatively be used. The arrangement of the screws is generally targeted towards creating a pre-loading effect.

Screws ends are preferably not leveled with cover 212 or bottom 216, but rather slightly submerged within. This is to ensure that force generated from moving vehicles acts directly upon the cover and transferred the mechanical loads directly to the embedded piezoelectric elements.

Figure 2B schematically depicts an isometric internal view of the housing 210 of a narrow piezoelectric generator 200, accommodating a plurality of piezoelectric elements 220 arranged in two horizontal rows according to an exemplary embodiment of the current invention.

A single piezoelectric element will be referred to herein as 220. The length of narrow WIM generator 200 may be 50 centimeters and its width may be 7 centimeters. Alternatively, other dimensions may be used which suit requirements.

PZT elements 220 may be in the form of a rod, a disk, or any other form which suits requirements. PZT elements 220 act upon compression forces with active D₃ piezoelectric effect generating signal indicative of the applied force. The dimensions selected for a single PZT element may vary according to requirements. PZT elements of different sizes, shapes and types may be embedded into a single piezoelectric generator. PZT elements may be layered on top of one another, as disclosed in the applicant's previous applications. Piezoelectric elements 220 are sometimes reffered herein as "PZT elements" may be made of Lead zirconate Titanate (PZT), but other piezoelectric materials may be used. For example, piezoelectric polymers may be used. Each element 220 may be a single element, a sintered (co-fired) piezoelectric stack of assembled piezoelectric stack. The number of rows, the number of elements, location and interspersion of embedded PZT elements within a WIM 200 may vary according to requirements. For example and without limitation. A generator may comprise two rows of 8 to 16 elements each of disks having a diameter or between 7 to 20 millimeters arrange in parallel rows or in a zig-zag pattern. The load on the elements should not exceed 20 MegaPascals so as to ensure the stability and longevity of the system. It should be noted that shape of PZT elements may be round as disks or rods, but rectangular or other shapes may be used.

Piezoelectric elements 220 may be held in cavities in a matrix 299 that support the elements.

Tapped holes 298A to 298G (only three: 298A, B and C are marked) are used for securing screws 214A to 214G respectively.

Figure 3A schematically illustrates a cross-sectional view of a road 300 comprising a concrete casing 310 serving as a placeholder for two narrow generators 200A and 200B according to an exemplary embodiment of the current invention.

Casing 310 may be constructed from materials other than concrete which suit requirements, for example plastic or metal. In this exemplary embodiment, generators 200 are exposed and are placed such that their covers are at the level of the road's surface 331.

Figure 3B schematically depicts a cross section of a road 300 that illustrates how generators 200A and 200B may be placed within casing 310 below the surface 331 of the road 300 according to another exemplary embodiment of the current invention.

In this exemplary embodiment, casing 310 is embedded into the road and covered with an insulting layer 320, optionally a bituminous sheet, and further covered by a layer of asphalt 330 according to an exemplary embodiment of the current invention.

In this exemplary embodiment, generators 200 are placed below road surface level, 331 and the asphalt layer 330 is used for creating a smooth and leveled road surface. Figure 4 depicts a schematic top view of a road lane 400 showing the driving direction 410 and embedded with two succession casing clusters 420A and 420B according to an exemplary embodiment of the current invention.

In the figure, each casing cluster 420A and 420B comprises a plurality of PZT casings, for example casing cluster 420A having two casings 422A and 424B, each casing capable of receiving two narrow piezoelectric generators 200.

The clusters are arranged such that casings are placed next to each other in a straight line perpendicular to driving direction 410. Casings 422 in clusters 420A and 420B are connected to energy conversion and signal extraction unit 120 (seen in figure 1) via connecting cables 421A and 421B respectively. For drawing simplicity, other elements of scale system 100 were omitted from this and other figures.

Generators in casing 422 may be connected to each other or may be separately connected to energy conversion and signal extraction unit 120.

In the exemplary embodiments, clusters 420A and 420B are separated along the direction of vehicle travel, thus enabling speed determination from time difference between the signals produced by the two clusters.

In the exemplary embodiments, each one of clusters 420A and 420B may comprise two casings such as depicted in figures 3A or 3B. Preferably, the casings are placed upon the road in locations where passing vehicles' wheels are most likely to pass directly over them. An optional gap 459 may be left between the casings where probability of wheel passing is low. However, generators 200 may be placed without gaps or across the entire lane 400.

It should be noted that figure 4 is to be viewed as demonstrating the optional positions of the generators in a first row and second row along the direction of the traffic, where in each row the generators positioned at right wheel route and left wheel route. For figure clarity, other components of system 100 seen in figure 1 are not seen here. For example optional camera 190 and optionally license plate illuminators for nighttime operation may be positioned near the road's curb 499 or on a pole or arch above the road 400. Similarly, optional speed detection unit 192, for example RADAR or laser unit used in automatic speed limit enforcement, may be positioned near the road's curb 499 or on a pole or arch above the road 400. Optionally, camera 190 or an additional camera may be used for vehicle detection purposes, optionally also identifying the type of vehicle. Optionally, vehicle detection unit such as induction loop is embedded in the relevant lane.

For drawing simplicity, figure 4 depicts installation of unit 100 in one of the lanes of road 400. It should be noted that systems may be installed on several lanes, all the lanes, and optionally on opposite sides of the road. However, since traffic is usually heavier on the right lane; and heavy truck, for which load monitoring is more important, often travel on the right lane right lane installation may be preferred.

SENSORS

Piezoelectric energy generation and data extraction can be studied to determine how much energy can be harvested from passing vehicles according to their velocity and weight, for example and without limitation by measuring electric voltage or current. Accordingly, the weight of a passing vehicle can be deduced from the amount of energy generated by piezoelectric generators or the signals generated by sensors.

Additionally, optionally or alternatively, signal shape (voltage vs. time) and magnetite may be analyzed. For example, a less inflated tire may create a longer signal with lower peak voltage due to its larger contact with road's surface. Data may optionally and additionally be calibrated according to additional measurement tools such as radars for measuring velocity of moving vehicles. Other factors such as temperature may be used during the calibration process. Calibration vehicle may be driven periodically over the generator for calibration. Uneven and/or unbalanced loading may be detected by comparing signals generated by separate passing wheels of the same vehicle. Imbalanced tire may be detected by identifying an unusual signal time-profile and/or by observing signal signature of the same wheel traversing different generators at different phases of its rotation.

The study may comprise a calibration phase, during which data about the amount of energy harvested or signal generated from vehicles is recorded. During the calibration phase, vehicles typically have pre-defined weights and are moving at pre-defined speeds. The data may be stored in storage units, analyzed by a person or dedicated software, and optionally displayed in the form of tables, graphs, or any other means which suit requirements. After calibration is complete, vehicles may pass over the piezoelectric scale. Their speed may be measured for example and without limitation by traveling over two consecutive piezoelectric clusters comprising piezoelectric generators or sensors, and measuring the energy or signal generated from the applied forces. The speed of the vehicle may be deduced, for example and without limitation, by measuring the times in which the two piezoelectric energy readings are recorded. Alternatively, the speed may be deduced according to the time cycle of the recorded signal's frequency, the external speed detection unit 192, or any other means which suit requirements.

The data recorded in the calibration phase can be used to deduce the weight of the passing vehicle according to the electric current or voltage measurements and the recorded speed.

Optionally, deducing the weight of the vehicle can be performed by a person skilled in the art. Optionally, the processor 130, the server 155, or any other automated means that suits requirements may be used to interpret and extract vehicle weight information.

Axial load distribution of a vehicle may be determined with the piezoelectric weigh in motion system disclosed herein. Attributing axial load to a specific vehicle may be determined for example and without limitation according to an analysis of one or more of measured speed, typical distance between axes within a single vehicle, typical distance between moving vehicles at a specific travel speed, and specific load profiles of moving vehicles and information deduced from vehicle detection unit 193.

Optionally, data about vehicle speed and weight can be automatically transferred to authorities via a communication unit. This data may be correlated by vehicle identification as determined by camera 190. Optionally, data can be transferred to the driver of the vehicle or the vehicle owner.

Statistical data can be obtained about road traffic comprising vehicles such as but not limited to trucks, vehicles, motorcycles or the like. For example and without limitation, data about vehicle density may be used in "smart road" applications, where traffic lights can be timed to alert vehicles on heavy traffic, vehicles slowing or stopping for example due to a possible accident, and to adjust traffic for example by directing it to alternative roads. Data obtained from this system may further be used for enforcing safety regulations, for example lane retention, keeping safe distance between vehicles, and maintaining balanced loads on trucks. Measurement accuracy and precision may be influenced by vehicle speed, but in general the system enables in-motion weight measurement capabilities regardless of the speed in which the vehicle travels.

According to another exemplary embodiment of the current invention, a method for embedding embodiments of vehicle WIM devices in a road may comprise:

• Exposing a nest within a road lane for receiving at least one vehicle WIM device. This can be done by scratching the surface of an asphalt road, optionally by using a road scarifier;

• arranging a plurality of piezoelectric WIM generators or sensors such as generators 200 in the form of clusters within the exposed nest;

· molding a casing for the PZT generators, optionally by pouring cement around the generators to fill the gaps formed between the generators and secure them to the nest and to each other;

• Molding a casing for the PZT generator, optionally by pouring grouting material around the generators to fill the gaps formed between the generator and secure then to the nest and to each other.

• Molding a casing for the PZT generator, optionally by pouring grouting material between the base of the roadway and around the generators to fill the gaps formed between the generator and secure then to the roadbed and to and to each other.

• arranging the wires attached to the generators and connecting them to a conversion and signal extraction unit;

• optionally applying a layer of epoxy on top of the generators and casing;

• optionally applying a layer of hot rubber bitumen, covering the generators and casing;

• applying a layer of cold rubber bitumen, covering the generators and casing.

• laying bituminous sheets over the rubber bitumen; and

· applying an asphalt layer over the rubber bitumen and compressing it such that the covered nest is leveled with the road.

The nest may be for example and without limitation 8-15 centimeters deep. The other dimensions of the nest may vary according to the size and type of the generators intended to be embedded within the nest. For example and without limitation the dimensions of the nest may be configured to receive two adjacent narrow generators 200 (having a total length of 100 centimeters, a width of 10 centimeters and a thickness of three centimeters).

The method described herein is by way of illustration, and should not be looked at as limiting. For example, different dimensions may be used to create the nest within the road lane, and different machinery may be used to perform part or all of the tasks mentioned in the method above.

The vehicle WIM system is designed so that the signal from the generator needs no external amplification. The system can be designed to provide itself with the energy required for its operation. It is easily embedded into roads in construction, as well as into existing roads by means of retrofitting as described hereinabove. Energy and data obtained from the generators may be transferred be means of wired or wireless communication. The automated system and method for enforcing vehicle weight restrictions in motion without disturbing road traffic is a superior alternative to weigh bridges and other vehicle weight enforcement mechanisms.

The vehicle WIM system may serve for other uses, for example it may be embedded into entrances to plants and factories.

Figure 5 schematically depicts vies of WIM sensor 900 which may serve as a piezoelectric generator or sensor, substituting for generators/sensors 200 and/or clusters 422, according to an exemplary embodiment of the current invention.

In this figure, 901a is a long side view, 901b is a narrow side view, 901c is an isometric view, 901d is a top view and 901e is an enlarged cross section taken at the A-A seen in view 901d.

WIM sensor 900 comprises a box 910 and a cover 911. Cover 911 has tapped holes 920 for fastening or holding the WIM sensor 900, for example during the process of embedding it into a road.

Within box 910, and in contact with the box and the cover 911 is the piezoelectric assembly 930 (seen in the cross section view 901e). Piezoelectric assembly 930 comprises two plastic layers 931 transferring compression force to the piezoelectric active structure 933 when force is applied to cover 911. Piezoelectric active structure 933 comprises a single or a stack of multiple layers of piezoelectric material, and conductive layers acting as electrodes. Piezoelectric assembly 930 is held in place with holding screws 935 which are fastened to box 910. Piezoelectric material in Piezoelectric active structure 933 act upon compression forces with active D_{3 3} piezoelectric effect, generating signal indicative of the applied force. Optionally, holding screws 935 provides pre-loading force on piezoelectric assembly 930 by forcing the upper plastic layers 931 towards box 910.

In an exemplary embodiment of the current invention, the dimensions of WI sensor 900 may be approximately 400 mm long, 40 mm wide and 60 mm deep. In an exemplary embodiment of the current invention, clusters of three WIM sensor 900 may be used as "left wheel assembly" and "right wheel assembly"; wherein each assembly is approximately 3x0.4 = ~1.2 m in length. Alternatively each cluster is made of four WIM sensor 900 and has a length of approximately 4x0.4 = ~1.6 m. Optionally, the three or four WIM sensor 900 in a cluster are wired together in parallel to form a sensor for one wheel.

The narrow and shallow dimensions of the assembly enable installation of the assembly in a ditch curved in the road. Preferably, the WIM sensor 900 is hermetically sealed against the weather.

In an exemplary embodiment of the invention, the upper and lower parts (911 and 910 respectively) of the WIM sensor 900 may be made of rigid material such as aluminum. The sensor's active structure 933 comprises a single row of piezoelectric disks which are designed to be loaded at 20 megapascals or less to ensure stability. Preferably, diameter of the disks is between 6.5 to 10 mm for greater efficiency.

Two of clusters are placed in a row in the traffic lane so as to provide recordings for both right and left wheels. A second row of these clusters is placed at a distance of preferably at least one meter apart so that the speed of the vehicle can be calculated. Alternatively one row records only the right wheel and the second row records only the left wheel.

The sensors 900 are placed in slots cut in the road. The slots may be filed with polymer grouting or the base of the slot may be filled with a concrete layer and then filled with polymer grouting, or the slot may be filled with cold asphalt or other material used for fixing road cracks with or without the concrete base. Sensors 900 produce sufficient voltage so that amplification of the signal is not need. Sensors 900 may not produce enough energy to power a wireless information communication. In some embodiments, additional piezoelectric generators modules may be added to the system to provide enough energy for wireless transmission and/or to power other equipment such as vehicle identification.

In some embodiments sensors 900 may be placed at roadway level such that the wheel of a passing vehicle makes direct contact with the cover of sensor 900.

In some embodiments sensors 900 may be placed such that the box is facing upwards and the cover is downward. In some embodiments the wheel of a passing vehicle makes direct contact with the box of sensor 900.

The scope of the present invention is defined by the appended claims and includes both combinations and sub combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.

In the claims, the word "comprise", and variations thereof such as "comprises",

"comprising" and the like indicate that the components listed are included, but not generally to the exclusion of other components.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims

A piezoelectric vehicle weight-in-motion system comprising:

at least two rows of piezoelectric sensors, situated such that said rows are substantially perpendicular to the direction of traffic on a motorway, and separated by at least 1 m, wherein one of said rows comprises a right-wheel cluster of sensors and the other row a left-wheel cluster of sensors, and wherein each of said cluster comprises at least two piezoelectric sensors connected in parallel, wherein each of said piezoelectric sensor comprises at least one piezoelectric element configured to produce electrical signal indicative of the force applied on said sensor by a vehicle passing over said sensor; and a processor, receiving signals from said piezoelectric sensors, wherein said processor is capable of determining the speed in which said vehicle passed over said sensors and the load of said vehicle while said vehicle is traveling at normal traffic speed.

A piezoelectric vehicle weight-in-motion system comprising:

at least two rows of piezoelectric sensors, situated such that the rows are substantially perpendicular to the direction of traffic on a motorway, and separated by at least 1 m, wherein each of said rows comprises at least a right-wheel cluster of sensors and a left- wheel cluster of sensor, and wherein each of said cluster comprises at least two piezoelectric sensors connected in parallel, wherein each of said piezoelectric sensor comprises at least one piezoelectric element configured to produce electrical signal indicative of the force applied on said sensor by a vehicle passing over said sensor; and a processor, receiving signals from said piezoelectric sensors, wherein said processor is capable of determining the speed in which said vehicle passed over said sensors and the load of said vehicle while said vehicle is traveling at normal traffic speed.

The system of claim 1 or 2 wherein said piezoelectric element produces said electrical signal by reaction to compression forces with active D_{3 3} piezoelectric effect, generating signal indicative of the applied force.

A system claim 1 or 2 wherein the signal from the piezoelectric sensors does not require external amplification .

5. A system claim 1 or 2 wherein the piezoelectric sensor is coupled with other piezoelectric generators so that the electrical needs of the system including or not including a vehicle identification system are supplied by the piezoelectric elements without need for an external power source.

6. The system of claim 1 or 2 wherein said piezoelectric sensor comprises:

a box;

a cover;

a plurality of piezoelectric elements disposed between said box and said cover, wherein said piezoelectric elements are connected in parallel and are configured to produce electrical signal indicative of compressive force applied between said cover and said box.

7. The system of claim 6 wherein said plurality of piezoelectric elements are arranged in a single layer.

8. The system of claim 6 wherein said plurality of piezoelectric elements are arranged in a single row.

9. The system of claim 6 wherein said plurality of piezoelectric elements are arrange in a zig-zag pattern.

10. The system of claim 6 wherein at least one of said box and said cover is made of aluminum.

11. The system of claim 6 wherein the sensor measures approximately 400 mm long, 40 mm wide and 60 mm deep.

12. The system of claim 6 wherein each of the clusters of sensors comprises at least three sensors.

13. The system of claim 1 or 2 and comprising a camera capable of capturing an electronic image of said passing vehicle and transferring said capture image to said compressor, wherein said processor is capable of determining the license plate number of said passing vehicle and associating the load of said passing vehicle to said determined license plate number.

14. The system of claim 1 or 2 and comprising a vehicle detection unit capable of detecting a passing vehicle and transferring information indicative of said passing vehicle to said compressor,

wherein said processor is capable of using said transfer information to associate all signals generated by said sensors in response to a specific passing vehicle to said specific passing vehicle.

15. The system of claim 1 or 2 and comprising a speed detection unit capable of determining the speed of a passing vehicle and transferring information indicative of the speed of said passing vehicle to said compressor,

wherein said processor is capable of using said transfer information to calculate the loads on wheels of said passing vehicle.

16. The system of claim 1 wherein said processor is capable of determining ^'unbalanced loading of said passing vehicle.

17. The system of claim 1 or 2 wherein said processor is capable of determining overloading of said passing Vehicle.

18. The system of claim 1 or 2 and comprising:

a remote server; and

a communication unit, connected to said processor and capable of transmitting information indicative of said passing vehicle to said remote server.

19. The system of claim 1 or 2 and comprising:

at least one piezoelectric generator capable of generating electric power when force is applied to said piezoelectric generator by a wheel of a vehicle passing over said generator;

an energy conversion unit converting said generating electric power to useful electric energy; and

an energy storage, capable of storing said useful electric power and supply energy to power said system.

20. A method for determining the weight of passing vehicles while in motion using piezoelectric generators comprising the steps of: positioning at least a first row of piezoelectric sensors and a second rows of piezoelectric sensors substantially parallel to each other, perpendicular to the direction of traffic on a roadway lane, and spatially separated;

generating electric signals from said at least two rows of piezoelectric sensors in response to forces applied by the wheels of a passing vehicle over said piezoelectric sensors;

determining the speed of said passing vehicle from the time difference between a signal generated by at least one sensor in said first row and a signal generated by at least one sensor in said second row; and

determining the weight of said passing vehicle from said generated signals taking into account said determined speed of said passing vehicle.