Calibration of and Site Selection for a WIM Sensor and WIM Sensor

Abstract

A method for generating a calibration function of a WIM sensor that is arranged in a roadway and measures a wheel force exerted on the surface of the roadway includes recording the roadway's road profile. A wheel force is determined by a simulation. The simulation is used to determine the dependency of the wheel force on the road profile for at least one position of the road profile that has been recorded in the first step. The dependency is used to minimize the influence of the road profile on the measured wheel force of the WIM sensor.

Claims

1. Method for generating a calibration function of a WIM sensor that is arranged in a roadway for measuring a wheel force exerted on the surface of the roadway, the method comprising the following steps: a) using an apparatus to record the road profile of the roadway, wherein the road profile of the roadway being a three dimensional representation of the surface of the roadway; b) a wheel force is determined by a simulation, which wheel force is exerted on the road profile by a wheel according to the simulation; which wheel is moving with a speed across the road profile of step a) in a longitudinal direction according to the simulation; which wheel is pressed onto the surface of the roadway according to the simulation; c) the dependency of the wheel force determined in step b) on the road profile recorded in step a) is determined by the simulation for at least one position of the road profile recorded in step a); and d) the dependency of the position determined in step c) is used la the simulation to minimize the influence of the road profile on the wheel force measured by the WIM sensor.

2. Method according to claim 1, wherein in step a) the road profile is recorded by the apparatus with an accuracy of at least 1 mm, along a vertical axis of the roadway; that in step a) the road profile is recorded by the apparatus with an accuracy of at least 100 mm, along a longitudinal axis of the roadway; that in step a) the road profile is recorded by the apparatus with an accuracy of at least 100 mm, along a lateral axis of the roadway.

3. Method according to claim 1, wherein in step b) the wheel is connected according to the simulation with at least one body mass; and wherein the wheel in step b) is pressed onto the road profile by the body mass according to the simulation.

4. Method according to claim 3, wherein in step b) the wheel is connected to the body mass via a resilient connection that includes a first spring element with a predefined spring constant and that includes a first damper element with a damping constant.

5. Method according to claim 4, wherein in step b) the wheel according to the simulation features a wheel mass, a second spring element and a second damper element; the wheel in step b) is pressed onto the surface of the roadway by the wheel mass according to the simulation; and that the wheel with the second spring element and second damper element is a damped mass-spring system.

6. Method according to claim 1, wherein in step b) the simulation is configured with a damped mass-spring system that includes at least one spring element, at least one damper element and at least one mass; wherein according to the simulation the mass is connected to a contact point between the wheel and the roadway via at least one damper element and at least one spring element; and wherein the simulation determines the wheel force that a wheel exerts onto the contact point between wheel and roadway.

7. Method according to claim 6, wherein in step b) the simulation determines an excitation of the damped mass-spring system excited by the wheel moving with a speed across an unevenness of the surface of the roadway, wherein the unevenness being represented within the road profile of step a).

8. Method according to claim 7, wherein for a position in step c) the wheel force according to the simulation is depending on the spring element and damper element of the damped mass-spring system; wherein for a position in step c) the wheel force according to the simulation is depending on the speed of the wheel moving across the surface of the roadway; and wherein for a position in step c) the wheel force according to the simulation is depending on at least one mass of the mass spring system.

9. Method according to claim 8, wherein step c) is performed by the simulation for a number of adjacent positions on the longitudinal axis and/or adjacent positions on the lateral axis; wherein adjacent positions has a distance between 2 mm and 500 mm to each other; wherein step c) is performed by the simulation for at least one speed of the wheel on the road profile; wherein the simulation uses the speed in combination with the road profile of the roadway in determining the excitation of the damped mass-spring system.

10. Method according to claim 1, wherein the apparatus used in step a) to record the road profile is a recording vehicle recording the unevenness of the roadway while driving on the roadway.

11. Method according to claim 1, wherein the following substeps of step d) are performed: d1a) the road profile 2 in step a) is recorded for at least one lane of a section of the roadway, starting at a distance in front of a position a WIM sensor is arranged at with respect to the longitudinal direction and ending at least 100 mm behind the position the WIM sensor is arranged at; with the distance being at least 25 m; d2a) wherein the wheel force according to step b) is determined by the simulation; d3a) wherein the dependency of the wheel force on the road profile at the position the WIM sensor is arranged in the roadway is determined by the simulation according to step c) for different speed ranges within an overall speed range between and including 5 km/h and 250 km/h; and step c) is performed by the simulation for different wheel force ranges within an overall wheel force range between and including 1000 N and 50000 N per wheel; and wherein the simulation includes spring elements and damper elements that are predetermined for a respective wheel force range; d4a) wherein the simulation determines a deviation of the wheel force depending on the speed range and mass range and on the road profile from a measured wheel force of a stationary vehicle with a mass within the mass range; and wherein the simulation generates a calibration function by subtracting the deviation from a measured wheel force of the WIM sensor according to the wheel force range and according to the speed range of a speed determined by the simulation for the wheel.

12. WIM System comprising: an evaluation element that includes the calibration function according to claim 11; a WIM sensor connected to the evaluation element that is configured to use the calibration function to subtract the deviation from a measured wheel force of the WIM sensor according to a wheel force range of the measured wheel force that is within and according to a speed range of a speed determined for the wheel is within; and wherein the evaluation element is configured to provide the result as a calibrated wheel force.

13. WIM System according to claim 12, wherein the wheel force measured by the WIM sensor is calibrated with the calibration function; wherein the calibrated wheel force reduces the influence of the road profile on the measured wheel force by at least 75% with respect to the measured wheel force of a stationary vehicle.

14. Method to select a location for a WIM sensor to be arranged in a roadway at the selected location, characterized in that the following steps are performed: a2) a road profile of a section of the roadway is recorded according to step a) of claim 1 for at least one lane of the roadway, in which lane the WIM sensor is to be arranged; which section of the roadway comprises a length in longitudinal direction of at least 25 m; b2) a wheel force is determined by a simulation according to step b) of claim 1; c2) the simulation is used to determine a dependence of the wheel force exerted on the road profile determined in step a) of claim 1 for a number of adjacent positions in the longitudinal direction, wherein adjacent positions have a distance between 250 mm and 5000 mm to each other; which positions lie within the road profile recorded in step a) of claim 1; c3) Step c2) of claim 1 is performed for different speed ranges within an overall speed range between and including 5 km/h and 250 km/h; and step c2) of claim 1 is performed for different wheel force ranges within an overall wheel force range between and including 1000 N and 50000 N per wheel; and spring elements and damper elements are predetermined for a respective wheel force range; d2) From the results of step c3) of claim 1 a position of the roadway is selected, where the dependence of wheel force is minimal for at least one preselected wheel force range and at least one preselected speed range.

15. A method of installing a WIM System in a roadway, the method comprising: applying the method according to claim 14 to select a location in the roadway for installing a WIM sensor; preparing an opening in the roadway at the selected location to receive the WIM sensor; and installing the WIM sensor in the opening.

16. Method according to claim 1, wherein the apparatus used in step a) to record the road profile is an aircraft recording the unevenness of the roadway while flying over the roadway or while flying next to the roadway.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings used to explain the embodiments show:

[0037] FIG. 1 A schematic illustration of the method for improving the precision of a WIM sensor,

[0038] FIG. 2 A representation of a sectional view of a vehicle on a roadway,

[0039] FIG. 3 A representation of a sectional view of a wheel of a vehicle on a roadway,

[0040] FIG. 4 A schematic representation of a mass-spring model representing a vehicle on a roadway,

[0041] FIG. 5 A schematic representation of the mass-spring model representing a vehicle on a roadway of FIG. 4 illustrating the forces involved,

[0042] FIG. 6 A sketch of a sectional view of a wheel of a vehicle on a roadway, with a WIM sensor arranged in the roadway, and

[0043] FIG. 7 A sketch of a view taken from above a section of a roadway.

DETAILED DESCRIPTIONS OF PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

[0044] FIG. 1 shows an illustration that is a schematic representation of the method for improving the precision of a WIM sensor arranged in a roadway, comprised of step a) 101, step b) 102, step c) 103 and step d) 104. The steps are described in detail below.

[0045] Step a) comprises recording a profile of a roadway 1, the profile of a roadway being a three dimensional representation of the surface 2 of the roadway schematically shown in FIGS. 2-7. The profile of the roadway that is determined according to step a) of the method is stored electronically in an electronic memory, which profile for example can be in the form of a three-dimensional object. An electronic memory can be a random access memory (RAM) and/or a memory, for example an EEPROM (electrically erasable programmable read-only memory). A three-dimensional object can be represented in the form of a 3-dimensional wire frame model known from computer assisted design software. The electronically stored road profile 2 is provided for further use in the simulation of step b) 102.

[0046] Step b) 102 comprises determining the wheel force F9 by a simulation 102; which wheel force F9 is exerted on the road profile 2 by a wheel 8; which wheel 8 is moving with a speed across the road profile 2 of step a) in a longitudinal direction X; which wheel 8 is pressed onto the surface of the roadway 1. The simulation is run on a processing element of a computer system. The simulation is generated by a computer program, which defines certain operations that the processing element should perform on an input. The input data for generating the simulation are at least the road profile 2 and a description of the vehicle and vehicle speed. The description of the vehicle includes all data that the simulation needs to calculate a wheel force F9 as an output of the simulation as described below.

[0047] FIG. 2 shows a sketch of a sectional view of a vehicle on a roadway in a plane given by the lateral axis Y′Y and vertical axis Z′Z. The wheels 8 of the vehicle 10 are connected to the body mass 3 of the vehicle 10 by the suspension 4 of the vehicle 10. The vehicle 10 in FIG. 2 is depicted moving on the surface of the roadway 1 in a longitudinal direction X (not shown), which is the direction that is orthogonal to the directions of both the lateral axis Y′Y and the vertical axis Z′Z.

[0048] FIG. 3 shows a sectional view of the wheel 8 of a vehicle 10 on a roadway 1 in a plane given by the longitudinal axis Y′Y and the vertical Z′Z axis simulated in one embodiment of the simulation 102. In step b) the wheel 8 is connected to at least one body mass m3 of the body 3 of the vehicle 10. The wheel 8 in step b) 102 is pressed onto the road profile 2 by the body mass m3.

[0049] In one embodiment, in step b) the wheel 8 is connected to the body mass m3 via a resilient connection that is characterized with a predefined spring element constant c42, c84 and damper element constant k41, k83, for example a resilient connection, in particular a wheel suspension 4 with a spring element 42 and a damper element 41 or shock absorber 41 of a vehicle 10. In the simulation, the wheel 8 moves across the surface of the roadway 1 in the longitudinal direction X. The wheel 8 comprises a wheel hub 82, which is the centre of rotation of the wheel 8 and the theoretical location of the mass m8 of the wheel 8 in the simulation step 102.

[0050] In one embodiment of the simulation 102, in step b) the wheel 8 is characterized by a spring element 84 and a damper element 83, for example an elastic running surface with a predetermined spring element 84 and a predetermined damper element 83. Therefore, the wheel 8 with the spring element 84 and the damper element 83 is a damped mass-spring system 200 in the simulation step 102.

[0051] In one embodiment, in step b) the simulation 102 comprises at least one damped mass-spring system 200; the damped mass-spring system 200 comprising at least one spring element 42, 84, at least one damper element 41, 83 and at least one mass m3, m8.

[0052] FIG. 4 shows the damped mass-spring system 200 simulated in one embodiment of the step b) simulation 102. The mathematical description of the model of a vehicle 10 on a roadway 1 can be represented in the simulation 102 as a one-dimensional juxtaposition of a first spring 84, a wheel mass 8, a second spring 42 and a body mass m3. Parallel to the first spring 84, a first damper element 83 is arranged. Each spring 42, 84 and damper element 41, 83 can be moved in one dimension, which is parallel to the vertical axis Z′Z.

[0053] The simulation 102 carried out in step b) determines the wheel force F9 that a wheel 8 exerts onto a contact point 9 between the wheel 8 and the roadway 1 on the surface of the roadway 1 by the mass m3, m8 connected to the contact point 9 via at least one damper element 41, 83 and at least one spring element 42, 84.

[0054] As schematically shown in FIG. 4, the first spring 84 and the first damper element 83 are fixed to the wheel mass m8. The second end of the first spring mass 84 and the first damper element 83 are commonly connected to a theoretical contact point 9. The contact point 9 is in contact with the surface of the roadway 2. The contact point 9 is the point in the middle of a contact surface where the wheel 8 touches the surface of the roadway 2.

[0055] Parallel to the second spring 42, a second damper element 41 is arranged as schematically shown in FIG. 4. The second spring 42 and the second damper element 41 are connected to the body mass m3 and connected to the wheel mass m8.

[0056] As schematically shown in FIG. 4, mass m3 and wheel mass m8 can move freely in the direction along the vertical axis Z′Z and within the constraints given by the forces that the springs 42, 84 and damper elements 41, 83 exert on the body mass m3 and wheel mass m8.

[0057] For a resting vehicle 10, forces acting on the body mass m3 and the wheel mass m8 are in equilibrium. For a moving vehicle 10, the only forces that have to be considered are those which are differing from the equilibrium forces. The forces involved in the simulation 102 of the vehicle 10 moving on the surface of the roadway 1 are shown schematically in FIG. 5.

[0058] The forces acting on the body mass m3 are given according to the simulation 102 of step b) by the following differential equations:

[00001] $m 3 \frac{d^{2} (h 3)}{{dt}^{2}} = - F 42 - F 41 + F 3, F 42 = c 42 h 3, F 41 = k 41 \frac{d (h 3)}{dt},$

with d/dt being the first time derivative, d.sup.2/dt.sup.2 being the second time derivative, h3 representing the distance between the body mass m3 and the wheel mass m8, F3 is representing a force due to an acceleration or deceleration of the vehicle 10 and/or due to the vehicle 10 driving along curve on the roadway 1, c42 represents the spring constant of the second spring 42, and k41 represents the damping constant of the second damper 41.

[0059] The forces acting on the wheel mass m8 are given according to the simulation 102 of step b) by the following differential equations:

[00002] $m 8 \frac{d^{2} (h 8)}{{dt}^{2}} = - F 84 - F 83 + F 42 + F 41 + F 8, F 84 = c 84 h 8, F 83 = k 83 \frac{d (h 8)}{dt},$

with d/dt being the first time derivative, d.sup.2/dt.sup.2 being the second time derivative, h8 representing the distance between wheel mass m8 and contact point 9, F8 is representing a force due to a potential unbalance of the wheel 8 or a non-uniformity of the wheel 8 or suchlike, c84 representing the spring constant of the first spring 84, and k83 representing the damping constant of the second damper 83.

[0060] The wheel force F9 acting on the road profile 2 is given according to the simulation 102 of step b) by the following differential equation:

[00003] $F 9 = F 8 4 + F 8 3 .$

The simulation 102 determines the movement of the wheel mass m3 and the body mass m8 by introducing an unevenness of the roadway 1 in the road profile 2 as an excitation of the damped spring mass system 200. A movement of the wheel 8 across the road profile 2 is simulated by moving the contact point 9 in a longitudinal direction X. This changes the distance h8. The temporal rate at which the distance h8 changes. depends on the speed of the vehicle 10. Thus, for calculating the wheel force F9 at a given position on the roadway 1, the simulation needs the speed of the vehicle 10 and the road profile 2 of the roadway 1 that the wheel 8 encounters for all positions on the roadway as an input data. As this is not possible in practice, especially since the road profile 2 of the roadway 1 recorded in step a) is limited in a longitudinal direction, the simulation is started with starting conditions of the damped spring systems involved in equilibrium. In order to determine the wheel force F9 at a certain position on the roadway, the starting position of the simulation 102 is chosen to be at least 1 m distance, preferably at least 100 m distance, optimal 500 m distance, from the position the wheel force F9 should be calculated for by the simulation 102.

[0061] In a presently preferred embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the damped mass spring system 200 given above.

[0062] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein some terms of the system of differential equations are neglected. A term is neglected if it does not contribute to the resulting wheel force F9 more than 10 percent, preferably less than one percent.

[0063] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the first spring 84 and the second spring 42 are combined in one spring element (not shown), the first damper element 83 and the second damper element 41 are combined into one damper element (not shown) and the wheel mass m8 is neglected and the forces F8 acting on the wheel 8 are neglected. The differential equations and the system of differential equations are adapted respectively. In this embodiment, the calculation is performed faster compared to calculating the first and second damper elements 41, 83 separately.

[0064] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the wheel mass 8 and the contact point 9 are connected with an element of constant length, comprising distance h8 constant. First damper element 83 and the first spring element 84 are omitted. The differential equations and the system of differential equations are adapted respectively.

[0065] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the first damper element 83 and the second damper element 41 are omitted. The differential equations and the system of differential equations are adapted respectively.

[0066] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the first damper element 83 is omitted. The differential equations and the system of differential equations are adapted respectively.

[0067] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the force F8 acting on the wheel mass m8 due to a potential unbalance of the wheel 8 or a non-uniformity of the wheel 8 or suchlike is omitted. The differential equations and the system of differential equations are adapted respectively.

[0068] In another embodiment of the invention, the simulation 102 determines the wheel force F9 by establishing and solving a system of differential equations given by the differential equations for the mass spring system 200 given above, wherein the force F3 acting on the body mass m3 due to an acceleration or deceleration of the vehicle 10 and/or due to the vehicle 10 driving along a curve on the roadway 1 is omitted. The differential equations and the system of differential equations are adapted respectively.

[0069] In another embodiment of the invention, the force F3 includes forces exerted on the body mass m3 by wheel forces F9 of other wheels 8 of the vehicle 10. A wheel force F9 can be determined with the simulation 102, and each wheel 8 has its own body mass in its simulation. As body masses m3 of each wheel 8 are connected in a real vehicle 10, movement of the body mass m3 of one wheel 8 influences the movement of the other body masses m3 of the other wheels 8 of a vehicle 10. The differential equations and the system of differential equations are adapted to consider the movement of other body masses m3. This simulation 102 thus uses a full car model or a half car model mentioned above.

[0070] In the different embodiments described above, the calculation is faster due to the omitting of terms, combination of terms, or rendering terms constant. This way, calculation power can be saved and a more cost-effective computing device for the simulation can be used.

[0071] The different embodiments may be combined where possible, and embodiments resulting from such a combination of embodiments described above are part of the invention as well.

[0072] In step c) of FIG. 1, the dependence of the wheel force F9 determined by the simulation 102 in step b) on the road profile 2 recorded in step a) is determined by the simulation 102 for at least one position P of the road profile 2 recorded in step a).

[0073] The dependency of the position P determined in step c) is used to minimize the influence of the road profile 2 on the wheel force W measured by the WIM sensor 7. This increases the measurement accuracy of the WIM sensor 7, as perturbations of the measurement by the road profile 2 are minimized.

[0074] It has been found that in order to obtain realistic results in the simulation 102 of a dynamic wheel force F9, the road profile 2 recorded in step a) 101 is recorded with an accuracy of at least 1 mm, preferred 0.2 mm, along a vertical axis Z′Z of the roadway 1; and the road profile 2 recorded in step a) 101 is recorded with an accuracy of at least 100 mm, preferred 2 mm, along a longitudinal axis X′X of the roadway 1; and the road profile 2 recorded in step a) is recorded with an accuracy of at least 100 mm, preferred 2 mm, along a lateral axis Y′Y of the roadway 1.

[0075] In one embodiment, in step b) the simulation 102 determines an excitation of the damped mass-spring system 200, excited by the wheel 8 moving with a speed across an unevenness of the surface of the roadway 1. In terms of the simulation 102, the unevenness is being represented within the road profile 2 of step a). This ensures that results of the simulation 102 are showing the same wheel force F9 as a vehicle 10 that would be travelling on the roadway 1.

[0076] In one embodiment, for a position P in step c) the wheel force F9 depends on the spring element 42, 84 defined by a spring constant and damper element 41, 83 defined by a damping constant of the at least one damped mass-spring system 200. The wheel force F9 depends on the speed of the wheel 8 moving across the surface of the roadway 1. The wheel force F9 depends on at least one mass m3, m8 of the mass spring system 200 for a position in step c). The speed of the wheel 8 changes the excitation of the mass spring system 200 and has therefore an influence on the dynamic motion of the excited damped mass spring system 200 as well as the damped mass spring systems dynamic motion is depending on the mass m3, m8 being part of the damped mass spring system 200.

[0077] In one embodiment, step c) is performed for a number of adjacent positions P on the longitudinal axis X′X and/or adjacent positions P on the lateral axis Y′Y; wherein an adjacent position has a distance between 2 mm and 500 mm to each other. Furthermore, step c) is performed for at least one damped mass-spring system 200 comprising at least one mass m3, m8 and at least one spring element 42, 84 and at least one damper element 41, 83 and for at least one speed of the wheel 8 on the road profile 2; the speed in combination with the road profile 2 of the roadway 1 determining the excitation of the damped mass-spring system 200.

[0078] In one embodiment, the road profile (2) in step a) 101 is determined by a recording vehicle (not shown recording the unevenness of the roadway (1) while driving on the roadway (1) or that the road profile (2) of step a) 101 is recorded by an aircraft (not shown) recording the unevenness of the roadway (1) while flying over or next to the roadway (1).

[0079] Minimizing the dependence of the wheel force F9 measurement of the WIM sensor 7 from the road profile 2 is achieved by generation of a calibration function (C) for a WIM sensor 7. For generation of the calibration function (C) the following steps are performed:

[0080] d1a) The road profile 2 in step a) is recorded for at least one lane of a section of the roadway 1, starting at a distance in front of the position P the WIM sensor 7 is arranged at with respect to the longitudinal direction X and ending at least 100 mm behind the position P the WIM sensor 7 is arranged at; with the distance being at least 25 m, preferred 100 m, optimal 500 m;

[0081] d2a) the wheel force F9 according to step b) is determined by the simulation 102;

[0082] d3a) the dependency of the wheel force F9 on the road profile 2 at the positions P the WIM sensor 7 is arranged in the roadway 1 is determined according to step c) 103 for different speeds ranges within an overall speed range between and including 5 km/h and 250 km/h; and step c) 103 is performed for different wheel force ranges within an overall wheel force range between and including 1000 N and 50000 N per wheel 8; and spring elements 42, 84 and damper elements 41, 83 are predetermined for a respective wheel force range;

[0083] d4a) the deviation of the wheel force F9 according to d3a) depending on the speed range and mass range and on the road profile 2 from a measured wheel force W of a stationary vehicle 10 with a mass within the mass range is determined; and that the calibration function (C) generated is able to subtract the deviation from the measured wheel force W of the WIM sensor 7 according to the wheel force range and according to the speed range of a speed determined for the wheel 8. FIG. 1 schematically shows a sectional view of a wheel 8 of a vehicle on a roadway 2, with a WIM sensor 7 arranged in the roadway 2.

[0084] It was found that the length of the road profile 2 given in step d1a) is enough to obtain realistic results of the wheel force F9 from the simulation 102. With the result of the simulation 102 of Step d4a) a calibration function (C) can be generated which is not only calibrating a measured wheel force W depending on the measured wheel force W but also calibrating the measured wheel force W depending on the speed of the vehicle 10.

[0085] Thus, the calibration function (C) calibrates the measured wheel force W. The calibration function (C) is a function of measured wheel force W and speed of the vehicle 10.

[0086] The calibration function (C) can be used readily in a WIM System 77. One embodiment of a WIM system 77 is shown as an example in FIG. 7. The WIM system 77 includes an evaluation element 6. The WIM system 77 is adapted to determine the speed of a wheel driving across the WIM sensor 7. The WIM sensor 7 is part of the WIM system 77 and the evaluation element 6 uses the calibration function (C) to subtract the deviation from a measured wheel force of the WIM sensor 7 according to the wheel force range the measured wheel force is within, and according to the speed range the speed determined for the wheel 8 is within; and accordingly the evaluation element 6 provides the result as a calibrated wheel force CW.

[0087] The wheel force F9 determined by the WIM sensor 7 of a WIM system 77 is calibrated with the calibration function (C); accordingly the calibrated wheel force CW reduces the influence of the road profile 2 on the measured wheel force W by at least 75% with respect to the measured wheel force W of a stationary vehicle 10.

[0088] In one embodiment, the simulation 102 is used to select a location fora WIM sensor 7. This is advantageous, as deviations of a measured wheel force W depending on the road profile 2 can be minimized before the WIM sensor 7 is installed in the roadway 1.

[0089] For selection of a location for a WIM sensor 7 to be installed in the roadway 1, the following steps are performed:

[0090] a2) The road profile 2 of a section of the roadway 1 is recorded according to step a) for at least one lane of the roadway 1, in which lane the WIM sensor 7 is to be installed; which section of the roadway 1 comprises a length along the longitudinal direction X of at least 25 m, preferred 1000 m, optimal 5000 m;

[0091] b2) The wheel force (F9) is determined by a simulation (102) according to step b) (102);

[0092] c2) The dependence of the wheel force F9 exerted on the road profile 2 determined in step a) 101 is determined by the simulation 102 for a number of adjacent positions P in the longitudinal direction X, wherein adjacent positions P are separated from each other by a distance between 250 mm and 5000 mm; which positions lie within the road profile (2) recorded in step a) 101;

[0093] c3) Step c2) is performed for different speed ranges within an overall speed range between and including 5 km/h and 250 km/h; and step c2) is performed for different wheel force ranges within an overall wheel force range between and including 1000 N and 50000 N per wheel 8; and spring elements (42, 84) and damper elements 41, 83 are predetermined for a respective wheel force range;

[0094] d2) From the results of step c3) a position P of the roadway 1 is selected, where the dependence of the wheel force F9 is minimal for at least one preselected wheel force range and at least one preselected speed range.

[0095] Of course, the preselected wheel force range must be chosen according to the demands on the wheel force measurement W. Such demands are different for wheel force measurements W at a toll booth versus wheel force measurements W at a mining site or versus wheel force measurements at an airport. The same is true for preselected speed ranges. The selection of the wheel force range and the speed range is therefore at the discretion of the owner of the WIM sensor 7.

[0096] In one embodiment, the location of a WIM sensor 7 that is installed in the roadway is selected for all WIM sensors 7 of the WIM System 77. The WIM system 77 comprising at least one WIM sensor 7. When all WIM sensors 7 of a WIM System are in respective positions P where deviations of a measured wheel force W depending on the road profile 2 are minimized, then the overall accuracy of the WIM system 77 is increased.

[0097] It is understood that the different aspects and embodiments described above may be combined where possible, and embodiments resulting from such a combination of embodiments described above are part of the invention as well.

LIST OF REFERENCE SYMBOLS

[0098] 1 roadway [0099] 10 vehicle [0100] 11 track of wheel [0101] 101 step a) [0102] 102 step b)/simulation [0103] 103 step c) [0104] 104 step d) [0105] 2 road profile [0106] 3 body [0107] 4 suspension [0108] 41 damper element [0109] 42 spring element [0110] 6 evaluation element [0111] 7 WIM sensor [0112] 77 WIM system [0113] 8 wheel [0114] 81 running surface [0115] 82 hub [0116] 83 damper element [0117] 84 spring element [0118] 9 contact point [0119] c42 spring constant [0120] c84 spring constant [0121] CW calibrated wheel force [0122] F9 determined wheel force [0123] h3 distance [0124] h8 distance [0125] k41 damping constant [0126] k83 damping constant [0127] m3 body mass [0128] m8 wheel mass [0129] P position [0130] W measured wheel force [0131] X longitudinal direction [0132] Y lateral direction [0133] Z vertical direction [0134] X′X longitudinal axis [0135] Y′Y lateral axis [0136] Z′Z vertical axis

Calibration of and Site Selection for a WIM Sensor and WIM Sensor

Inventors

Cpc classification

Classification Explorer

G01G19/022

PHYSICS

Classification Explorer

G01G19/024

PHYSICS

Classification Explorer

G01G23/01

PHYSICS

International classification

Classification Explorer

G01G19/02

PHYSICS

Classification Explorer

G01G23/01

PHYSICS

Abstract

Claims

Description