GB2480306A

GB2480306A - Weighing vehicles in motion

Info

Publication number: GB2480306A
Application number: GB201007995A
Authority: GB
Inventors: Michael Trakhimovich
Original assignee: SHEKEL SCALES CO
Current assignee: SHEKEL SCALES CO
Priority date: 2010-05-13
Filing date: 2010-05-13
Publication date: 2011-11-16
Anticipated expiration: 2030-05-13
Also published as: GB201007995D0; GB2480306A8; GB2480306B; GB2480306B8

Abstract

A method and system for weighing vehicles in motion includes a base for anchoring to a roadbed; a weighing platform mounted on the base and adapted to receive wheels of moving vehicles along a longitudinal axis of the platform; at least one load cell disposed between the base and the platform adapted to provide load signals indicating loads applied by the wheels on the platform. A longitudinal differentiation mechanism, mechanically associated with the platform and the base, is used in measuring longitudinal forces. The longitudinal differentiation mechanism includes a mechanical unit adapted to provide a measurable resistance to a relative horizontal movement between the base and platform in order to differentiate horizontal forces produced by the wheels acting on the platform. A processing unit uses the load cell data and horizontal force data to determine the weight of the vehicle in motion.

Description

System and Method for Weighing Vehicles in Motion

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to weighing systems and methods, and more particularly, to weighing systems and methods for weighing vehicles in motion.

The ability to weigh vehicles in motion offers many advantages over static weighing. One commercially important application of a weigh-in-motion (WIM) system is the weighing of vehicles such as trucks as they travel on highways. This has usually been accomplished by requiring trucks traveling on interstate highways to enter weigh stations, where they are weighed using static scales. Truck operators may, however, go to considerable lengths to avoid a weigh station for various reasons. This avoidance reduces the amount of data available to regulatory authorities as to truck traffic and also places heavy trucks on roads not designed for such traffic.

A WIM system may typically include a base anchored in concrete beneath the surface of the roadway, a weighing platform preferably disposed in a substantially level fashion with respect to the surface of the roadway, and load cells, mounted between the platform and the base, adapted to provide a signal indicating the load applied by the wheel contacting the platform.

Known WIM systems may be highly inaccurate relative to static scales, and may be particularly unsuited to reliably and accurately convert dynamic weight readings into static weights.

The present inventor has recognized a need for improved methods and systems for weighing vehicles in motion, and the subject matter of the present disclosure and claims is aimed at fulfilling this need.

SUMMARY OF THE [NVENTION

According to the teachings of the present invention there is provided a system for weighing vehicles in motion, the system including: (a) a base for anchoring to a roadbed; (b) a weighing platform mounted on the base and adapted to receive wheels of moving vehicles along a longitudinal axis of the platform; (c) at least one load cell disposed between the base and the platform, and adapted to provide load signals indicating loads applied by the wheels on the platform; (d) a longitudinal differentiation mechanism, mechanically associated with the platform and the base, the longitudinal differentiation mechanism including: (i) a mechanical unit (element or assembly) adapted to provide a measurable resistance to a relative horizontal movement between the base and the platform, the movement generally along the longitudinal axis, to differentiate horizontal forces produced by the wheels acting on the platform, and (ii) a measuring unit, associated with the mechanical unit, the measuring unit adapted to make a measurement of a parameter associated with the resistance and to produce an output signal relating to the measurement, and (e) a processing unit configured to: (i) receive the load signals from the at least one load cell, and the output signal from the measuring unit, and (ii) produce a weight indication based on the load signals and the output signal from the measuring unit.

According to another aspect of the present invention there is provided a method of weighing vehicles in motion, including the steps of: (a) providing a system including: (i) a base anchored to a roadbed; (ii) a weighing platform mounted on the base and adapted to receive wheels of moving vehicles along a longitudinal axis of the platform; (iii) at least one load cell disposed between the base and the platform, and adapted to provide load signals indicating loads applied by the wheels on the platform; (iv) a longitudinal differentiation mechanism, mechanically associated with the platform and the base, the longitudinal differentiation mechanism including: (A) a mechanical unit (element or assembly) adapted to provide a measurable resistance to a relative horizontal movement between the base and the platform, the movement generally along the longitudinal axis, to differentiate horizontal forces produced by the wheels acting on the platform, and (B) a measuring unit, associated with the mechanical unit, the measuring unit adapted to make a measurement of a parameter associated with the resistance and to produce an output signal relating to the measurement, and (v) a processing unit configured to: (A) receive the load signals from the at least one load cell, and the output signal from the measuring unit, and (B) produce a weight indication based on the load signals and a measurement of the parameter; (b) moving wheels of a vehicle along a longitudinal axis of the platform to provide the load signals and to produce the relative horizontal movement; (c) producing the output signal containing the measurement of the parameter; (d) processing the load signals and the measurement to produce a weight indication for the vehicle.

According to further features in the described preferred embodiments, the output signal includes information pertaining to the horizontal forces.

According to still further features in the described preferred embodiments, the system further includes a restoration mechanism, mechanically associated with the platform, the restoration mechanism adapted to repeatably restore the platform to a particular position.

According to still further features in the described preferred embodiments, the system further includes the roadbed.

According to still further features in the described preferred embodiments, the mechanical unit includes a spring.

According to still further features in the described preferred embodiments, the mechanical unit includes a hydraulic arm adapted to provide the measurable resistance to the relative horizontal movement.

According to still further features in the described preferred embodiments, the mechanical unit includes a pneumatic arm adapted to provide the measurable resistance to the relative horizontal movement.

According to still further features in the described preferred embodiments, the mechanical unit includes a spring adapted to provide the measurable resistance to the relative horizontal movement.

According to still further features in the described preferred embodiments, the measuring unit is adapted to measure the relative horizontal movement.

According to still further features in the described preferred embodiments, the measuring unit is adapted to measure a change in length associated with the relative horizontal movement.

According to still further features in the described preferred embodiments, the measuring unit includes an extensometer.

According to still further features in the described preferred embodiments, the extensometer includes a mechanical extensometer.

According to still further features in the described preferred embodiments, the mechanical extensometer includes an electrical transducer.

According to still further features in the described preferred embodiments, the electrical transducer includes a strain-gauge device.

According to still further features in the described preferred embodiments, the electrical transducer includes a linear variable differential transformer sensor.

According to still further features in the described preferred embodiments, the processing unit is further configured to exclude an initial spike or initial time period from the measurement of the parameter.

According to still further features in the described preferred embodiments, the processing unit is further configured to exclude a final spike or final time period from the measurement of the parameter.

According to still further features in the described preferred embodiments, the processing unit is further configured to exclude an initial spike and/or a final spike from the measurement of the parameter, to define a measurement window, and to use the information pertaining to the horizontal forces to produce the weight indication for the vehicle, wherein the information is selected solely from the measurement window.

According to still further features in the described preferred embodiments, the measuring unit includes an extensometer, the output signal includes information pertaining to the horizontal forces, and the processing unit is configured to exclude an initial spike and/or a final spike from the measurement of the parameter, to define a measurement window, and is further configured to use the information pertaining to the horizontal forces to produce the weight indication for the vehicle, wherein the information is selected solely from the measurement window.

According to still further features in the described preferred embodiments, the at least one load cell includes at least two load cells, at least three load cells, or at least four load cells.

According to still further features in the described preferred embodiments, the output signal includes information pertaining to the horizontal forces.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is 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. Throughout the drawings, like-referenced characters are used to designate like elements.

In the drawings: Figure 1 is a simplified, schematic view of a WIM system 100 according to the present invention; Figure 2a is a logical flow diagram according to one aspect of the inventive method, and Figure 2b is a logical flow diagram according to another aspect of the inventive method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of the weigh-in-motion (WIM) system and method of the present invention may be better understood with reference to the

drawings and the accompanying description.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

Referring now to the drawings, Figure 1 is a simplified, schematic view of a WIM system 100 according to the present invention. WIM system 100 includes a base 110 for anchoring to a roadbed, a weighing platform 120 mounted on the base and adapted to receive wheels of moving vehicles such as motor vehicle wheel 50 along a longitudinal axis X of the platform, and at least one load cell disposed between the base and the platform, and adapted to provide load signals indicating loads applied by the wheels on the platform. WIM system 100 also includes a longitudinal differentiation mechanism 150, mechanically associated with the platform and the base. This mechanism may include a mechanical resistance unit (element or assembly) 152 adapted to provide a measurable resistance to a relative horizontal movement between the base and the platform, the movement generally along longitudinal axis X, to differentiate horizontal forces produced by the wheels acting on the platform, and a measuring unit 154, associated with the mechanical unit, and adapted to make a measurement of a parameter associated with the resistance and to produce an output signal relating to the measurement.

Mechanical resistance unit (element or assembly) 152 may include a spring such as a cylindrical or spiral spring, a hydraulic arm a pneumatic arm, or other mechanical resistance unit adapted to measurably resist the relative horizontal movement between the base and the platform.

Measuring unit 154 may include an extensometer. An extensometer is an instrument for measuring changes in length that are caused by application of force. Various types of extensometers are known. Changes in length may be measured directly by some types of devices, such as clip-on extensometers, or indirectly by non-contact or video extensometers.

Mechanical or contact-type extensometers may use electrical transducers such as linear variable differential transformer (LVDT) sensors or strain-gauge devices (and sometimes combinations of the two) to generate an electrical signal proportional to change in length or strain. An extensometer system may also incorporate electronics for amplification of small signals.

WIM system 100 also includes a processing unit or processor 180, such as a central processing unit (CPU). Processor 180 may be configured to receive the load signals from the at least one load cell and the output signal from the measuring unit, and to produce a weight indication based on the load signals and the output signal from the measuring unit.

WIM system 100 is preferably equipped with a restoration mechanism such as restoration mechanism 140, which serves to restore a position of weighing platform 120 with respect to base 110, in preparation for another wheel rolling on to weighing platform 120. In WIM system 100, load cell 130 is a column-type load cell, and restoration mechanism 140 includes cupped surfaces on the top and on the bottom of load cell 130.

One aspect of the method of the present invention will now be described, with reference to the logical flow diagram provided in Figure 2a. A wheel such as motor vehicle wheel 50 is enabled to roll along a longitudinal axis of platform 120 to produce a dynamic vertical load as well as longitudinal horizontal forces exerted on platform 120 (step 1). The vertical load acts upon at least one load cell such as load cell 130, which produces dynamic vertical load signals corresponding to, or associated with, the vertical load (step 2).

WIM system 100 may also measure a parameter (step 3) associated with these horizontal forces, and produce an output signal based on, or related to, this measured parameter (step 4).

In step 5, a processing unit such as processor 180 processes the vertical load signals along with the output signal from step 4 to produce a WIM weight indication. A restoration mechanism such as restoration mechanism 140, which serves to restore a position of weighing platform 120 with respect to base 110, may be activated (step 6) in preparation for another wheel rolling on to weighing platform 120.

Another aspect of the method of the present invention will now be described, with reference to the logical flow diagram provided in Figure 2b. A WIM system such as WIM system 100 is provided. Subsequently, a wheel such as motor vehicle wheel 50 is enabled to rotate along a longitudinal axis of platform 120 to produce a dynamic vertical load and load signals corresponding thereto, and to produce a relative horizontal movement between base 110 and platform 120 (step 2). The vertical load acts upon at least one load cell such as load cell 130, which produces load signals corresponding to the vertical load.

WIM system 100 includes a longitudinal differentiation mechanism, such as longitudinal differentiation mechanism 150 described hereinabove. A mechanical unit (element or assembly) thereof such as mechanical unit 152, provides a measurable resistance to the relative horizontal movement between base 110 and platform 120, generally along longitudinal axis X of platform 120, to longitudinally differentiate horizontal forces produced by wheel 50 acting on platform 120 (step 3).

A measuring unit (element or assembly), associated with mechanical unit 152, such as measuring unit 154, makes a measurement of a parameter associated with this measurable resistance and produces an output signal relating to this measurement (steps 4, 5).

In step 6, a processing unit such as processor 180 processes the vertical load signals along with the output signal from step 4 to produce a WIM weight indication. A restoration mechanism such as restoration mechanism 140, which serves to restore a position of weighing platform 120 with respect to base 110, may be activated (step 7) in preparation for another wheel rolling on to weighing platform 120.

As used herein in the specification and in the claims section that follows, the term "extensometer" refers to an instrument for measuring a longitudinal displacement or extension caused by an application of force.

Mechanical resistance unit (element or assembly) 152 may include a spring or other resistance units that, at least ideally, approach the behavior delineated by Hooke's law. In the ideal case, the extension produced is directly proportional to the load: F -kx wherein: F is the restoring force exerted by the material, and k is the spring constant (in units of force per unit length).

Thus, for systems in which the extension produced is well correlated (using Hooke's law or any other correlation) with the load --in this case, horizontal forces --accurate measurement of the extension of mechanical resistance unit 152 may, in turn, enable accurate computation of the load.

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, including U.S. Patent No. 4,957,178, 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.

Claims

WHAT IS CLAIMED IS: 1. A system for weighing vehicles in motion, the system comprising: (a) a base adapted to be anchored to a roadbed; (b) a weighing platform mounted on said base and adapted to receive wheels of moving vehicles along a longitudinal axis of said platform; (c) at least one load cell disposed between said base and said platform, and adapted to provide load signals indicating loads applied by said wheels on said platform; (d) a longitudinal differentiation mechanism, mechanically associated with said platform and said base, said longitudinal differentiation mechanism including: (i) a mechanica' unit (e'ement or assemlily) adapted to provide a measurable resistance to a relative horizontal movement between said base and said platform, said movement generally along said longitudinal axis, to differentiate horizontal forces produced by said wheels acting on said platform, and (ii) a measuring unit, associated with said mechanical unit, said measuring unit adapted to make a measurement of a parameter associated with said resistance and to produce an output signal relating to said measurement, and (e) a processing unit configured to: (i) receive said load signals from said at least one load cell, and said output signal from said measuring unit, and (ii) produce a weight indication based on said load signals and said output signal from said measuring unit.
2. The system of claim 1, wherein said output signal includes information pertaining to said horizontal forces.
3. The system of claim 2, wherein said processing unit is further configured to exclude an initial spike and a final spike from said measurement of said parameter, to define a measurement window, and to use said information pertaining to said horizontal forces to produce said weight indication for said vehicle, wherein said information is selected solely from said measurement window.
4. The system of claim 1 or claim 2, further comprising: (f) a restoration mechanism, mechanically associated with said platform, said restoration mechanism adapted to repeatably restore said platform to a particular position.
5. The system of any one of claims 1-4, wherein said mechanical unit includes a spring.
6. The system of claim any one of claims 1-5, wherein said mechanical unit includes a hydraulic arm adapted to provide said measurable resistance to said relative horizontal movement.
7. The system of any one of claims 1-6, wherein said mechanical unit includes a pneumatic arm adapted to provide said measurable resistance to said relative horizontal movement.
8. The system of any one of claims 1-7, wherein said mechanical unit includes a spring adapted to provide said measurable resistance to said relative horizontal movement.
9. The system of any one of claims 1-8, wherein said measuring unit is adapted to measure said relative horizontal movement.
10. The system of any one of claims 2-9, wherein said measuring unit is adapted to measure a change in length associated with said relative horizontal movement.
11. The system of claim 10, wherein said measuring unit includes an extensometer.
12. The system of claim 11, wherein said extensometer includes a mechanical extensometer.
13. The system of claim 12, wherein said mechanical extensometer includes an electrical transducer.
14. The system of claim 13, wherein said electrical transducer includes a strain-gauge device.
15. The system of claim 13 or claim 14, wherein said electrical transducer includes a linear variable differential transformer sensor.
16. The system of any one of claims 1-15, wherein said mechanical unit includes a spring adapted to provide said measurable resistance to said relative horizontal movement.
17. The system of any one of claims 1-16, wherein said processing unit is further configured to exclude an initial spike or initial time period from said measurement of said parameter.
18. The system of any one of claims 1-17, wherein said processing unit is further configured to exclude a final spike or final time period from said measurement of said parameter.
19. The system of any one of claims 2-10, wherein said measuring unit includes an extensometer, and said processing unit is configured to exclude at least one of an initial spike and a final spike from said measurement of said parameter, to define a measurement window, and is further configured to use said information pertaining to said horizontal forces to produce said weight indication for said vehicle, wherein said information is selected solely from said measurement window.
20. A method of weighing vehicles in motion, comprising the steps of: (a) providing a system including: (i) a base anchored to a roadbed; (ii) a weighing platform mounted on said base and adapted to receive wheels of moving vehicles along a longitudinal axis of said platform; (iii) at least one load cell disposed between said base and said platform, and adapted to provide load signals indicating loads applied by said wheels on said platform; (iv) a longitudinal differentiation mechanism, mechanically associated with said platform and said base, said longitudinal differentiation mechanism including: (A) a mechanical unit (element or assembly) adapted to provide a measurable resistance to a relative horizontal movement between said base and said platform, said movement generally along said longitudinal axis, to differentiate horizontal forces produced by said wheels acting on said platform, and (B) a measuring unit, associated with said mechanical unit, said measuring unit adapted to make a measurement of a parameter associated with said resistance and to produce an output signal relating to said measurement, and (v) a processing unit configured to: (A) receive said load signals from said at least one load cell, and said output signal from said measuring unit, and (B) produce a weight indication based on said load signals and a measurement of said parameter; (b) moving wheels of a vehicle along a longitudinal axis of said platform to provide said load signals and to produce said relative horizontal movement; (c) producing said output signal containing said measurement of said parameter; (d) processing said load signals and said measurement to produce a weight indication for said vehicle.