Method for weighing a vehicle, and measuring system and measuring arrangement therefor

Abstract

A method for determining the weight G of a vehicle (1) while the vehicle is travelling on a section (3) of road (4) uses at least one weigh-in-motion (WIM) sensor (5) that is narrower than the length of the footprint of a wheel in the direction of vehicle travel. When the vehicle (1) travels along this section (3) of road (4) both the wheel loads F.sub.i(t) of all the wheels (2) or twin wheels i, and the speed v.sub.i(t) of the vehicle (1) during the entire passing are acquired as time functions, and during evaluation of the data for determining the weight G the speeds v.sub.i(t) and their change over time are used as weighting of the simultaneously determined wheel loads F.sub.i(t).

Claims

1. A method for determining the weight G of a vehicle travelling on a section of road and having a vehicle wheel footprint having its length measured in the direction of vehicle travel during the weight determination of the vehicle, the method comprising: employing a weigh-in-motion (WIM) sensor that has a width that elongates in a direction that is substantially parallel to the direction of vehicle travel during the weight determination of the vehicle and that is narrower than the length of the vehicle wheel footprint; using the WIM sensor in acquiring the wheel load of each wheel (i) as a time function F.sub.i(t) when the vehicle travels along the section of road; acquiring the speed v(t) of the vehicle as a time function simultaneously with acquiring the wheel load F.sub.i(t) of the wheel (i); and using the speed v(t) and the change in the speed v(t) over time as weighting of the simultaneously determined wheel load F.sub.i(t) to evaluate the data for determining the weight G.

2. The method according to claim 1, the steps according to which a) the wheel load F.sub.i(t) of follows: each wheel i in the case of a single wheel vehicle, or in the case of a vehicle with twin wheels then of each twin wheel of the vehicle with twin wheels, is individually acquired as a time function, during rolling on the road, by at least one WIM sensor; b) the speed v(t) of the vehicle, at least while all the wheels or twin wheels pass over a WIM sensor, is determined as a time function; c) the determined wheel loads F.sub.i(t) are synchronised with the determined speed values v(t) and are multiplied by each other F.sub.i.Math.v; d) each of the resulting products F.sub.i.Math.v is integrated over the time dt during the entire passing over of the vehicle to produce the integral I.sub.i; and e) each of the integrals I.sub.i is multiplied by its respective one of a plurality of calibration constants K.sub.i and all of these products of I.sub.i and K.sub.i are added up for determining the weight G.

3. The method according to claim 1, wherein the speed v(t) of the vehicle is acquired by means of radar or by means of the laser Doppler velocimetry method.

4. The method according to claim 1, wherein the speed v(t) of the vehicle is acquired by means of a device comprising an array of beams, which array is arranged in the direction of movement of the vehicle, through which array the wheels of the vehicle travel in turn as they travel over the WIM sensors.

5. The method according to claim 4, wherein the beams in the array are spaced apart from one another by a distance between the beams in the array that at most corresponds to the width of the WIM sensor.

6. The method according to claim 4, wherein the array is at least sufficiently long so that when the vehicle passes, always at least one beam of the array is not interrupted by a wheel.

7. The method according to claim 4, wherein the beams in the array are spaced apart from one another by a distance between the beams in the array that at most corresponds to approximately half the width of the WIM sensor.

8. The method according to claim 1, wherein any passing speeds of vehicles are admissible as passing speeds of the vehicles.

9. The method according to claim 1, wherein by means of a device it is determined which wheels/twin wheels i with all the trailers are to be allocated to a vehicle composition in order to determine the total weight of the vehicle composition.

10. The method according to claim 1, wherein the vehicle speeds v(t) and the wheel loads F(t) of all the wheels/twin wheels are acquired a second time on at least a second WIM sensor, which in the direction of travel is arranged downstream of the first WIM sensor, in order to improve the accuracy of weight determination.

11. The method according to claim 10, wherein each wheel load/twin wheel load with the associated speed is analysed at each WIM sensor and the average of both results is taken into account in further determining the vehicle weight G.

12. The method according to claim 1, wherein a toll for transit is levied based on the determined weight data G.

13. The method according to claim 1, wherein the passing speeds of vehicles can include speeds when the vehicle is in reverse.

14. A measuring system for determining the weight G of a vehicle while it is travelling on a section of road, taking into account the speed of the vehicle and its changes over time during determination of the weight of the vehicle, the measuring system comprising: at least one WIM sensor for installation in the section of road, which WIM sensor is configured for determining data about passing wheel loads F(t) in a time-dependent manner, and wherein the at least one WIM sensor in the direction of travel is narrower than the length of the footprint of a wheel of the vehicle; a device for determining data about the speed v(t) of the vehicle as a time function while the vehicle is travelling on the section of road; and an evaluation unit for evaluating the determined data, the evaluation unit configured for communicating with the WIM sensor and the device.

15. The measuring system according to claim 14, additionally comprising a device for determining the end of a vehicle composition that travels on a section of road and includes a beam grid that is established across the road and configured for communicating with the evaluation unit.

16. The measuring system according to claim 14, wherein the device for determining the speed of vehicle is one selected from one of the following devices for determining speed: a radar, a device measuring by means of laser Doppler velocimetry methods, and a device for generating and acquiring an array of beams.

17. The measuring system according to claim 14, additionally comprising induction loops that are installed in the road surface for determining the end of the vehicle composition that travels on the section of the road, the induction loops being configured for communicating with the evaluation unit.

18. A measuring arrangement for determining the weight G of a vehicle while it is travelling on a section of road, taking into account the speed of the vehicle and its changes over time during determination of the weight of the vehicle, comprising: at least one WIM sensor installed in the section of road, which WIM sensor can acquire passing wheel loads F(t) in a time-dependent manner; a device for determining the speed v(t) of a vehicle as a time function while the vehicle is travelling on the section of road; an evaluation unit for evaluating the determined vehicle weight data and vehicle speed data, the evaluation unit being configured for communicating with the WIM sensor and the device; and wherein the WIM sensor is installed in the road across the direction of travel so that the surface of said WIM sensor is flush with the road surface, and wherein the WIM sensor is narrower in the direction of travel than the length of the footprint of a wheel of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is explained in more detail with reference to the drawings. The following are shown:

(2) FIG. 1 a diagrammatic section view of a section of road with an installed WIM sensor, and a wheel of a vehicle while it passes over the sensor;

(3) FIG. 2 an acquired time-dependent signal of a wheel load F(t);

(4) FIG. 3 an acquired time-dependent speed v(t) of the vehicle while passing over the WIM sensor;

(5) FIG. 4 a measuring arrangement according to the invention with vehicles that travel along the section of road;

(6) FIG. 5 an example of a time signal F.sub.i(t) of a WIM sensor while a vehicle composition is passing, with synchronised time-dependent speed values v(t);

(7) FIG. 6 weighting of the wheel loads F.sub.i(t) with the synchronised speeds v(t);

(8) FIG. 7 a section of road with two WIM sensors and an array of beams for acquiring the speed.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

(9) FIG. 1 shows a WIM sensor 5, installed in a section of road 3, and a wheel 2 of a vehicle 1 (FIG. 4) while driving over the WIM sensor 5. The diagram shows in an exaggerated manner that the wheel 2 as a result of the load of the lorry I does not contact the road 4 in a point-shaped manner, but instead is somewhat flattened. As a rule, the WIM sensor 5 has a width of 50-70 mm, with the typical contact surface of a lorry wheel, depending on the diameter and air pressure of the wheel, comprising a length 14 of approximately 100-200 mm.

(10) FIG. 2 shows the time-dependent wheel load F.sub.i(t) of the wheel 2 i, which wheel load has been acquired by the WIM sensor 5. In this arrangement the wheel i can be a wheel or a twin wheel, wherein both wheels 2 of a twin wheel, which are installed on the same side of an axle of a vehicle 1, together move over the WIM sensor 5. A twin wheel 2 is treated in the same manner as a single wheel 2, and there is no differentiation. Consequently, this document simply refers to wheels 2, although twin wheels 2 are also included.

(11) FIG. 3 shows the time-dependent speed reading of the vehicle 2 v(t) that has been measured simultaneously with the wheel load reading F(t). For this purpose the measured data sets F(t) and v(t) need to be precisely synchronised in time, and therefore the times t in both data sets F(t) and v(t) need to be identical at all times.

(12) FIG. 4 shows a section of road 3 and a measuring system 12 according to an embodiment of the invention for determining the vehicle weight G of a vehicle composition 1 travelling on the section of road 3. The measuring system 12 comprises a WIM sensor 5 for determining the wheel loads F(t), a device 7 for determining the speed v(t) and an evaluation unit 10 for evaluating the acquired data and for determining the weight G of the vehicle composition 1. FIG. 4 shows, in particular, the measuring system 12 according to an embodiment of the invention in its installed state, which results in the measuring arrangement 13 according to an embodiment of the invention. The WIM sensor 5 is installed in the road 4, across the direction of travel, with the surface of said sensor being flush with the road surface. In this arrangement, as a rule, a WIM sensor 5 only extends to the middle of the road for acquiring one side of the wheel axles, while an adjacent WIM sensor 5′ extends from the middle of the road to the other road edge for acquiring the wheel loads of the wheels 2 on the other side of the axis. These WIM sensors 5, 5′ together are referred to as the WIM sensor.

(13) The device 7 for determining the speed v(t) needs to be arranged in such a manner that the vehicle speed during the entire passing over of the vehicle 1 can be acquired with all the axles over the WIM sensor 5. The data F(t) and v(t) is transmitted to an evaluation unit 10 which synchronises the two data series F(t), v(t). In this context it is important that synchronisation truly composes simultaneous data series.

(14) FIG. 4 shows a vehicle composition 1 comprising five axles. Preferably, the measuring system 12 or the measuring arrangement 13 comprises a device 11 for determining the end of a vehicle composition 1. This can, for example, be implemented in the form of a beam grid that can be established across the roadway, or in the form of induction loops that can be installed in the road surface. FIG. 4 diagrammatically shows this device 11.

(15) As soon as the end of a vehicle composition 1 has been determined, a corresponding signal is transmitted to the evaluation unit 10. This then terminates determining weight, and prepares for weight determination of the next vehicle 1′.

(16) FIG. 5 shows the synchronised wheel loads F(t) and v(t) in relation to a vehicle composition 1 comprising five axles for one side of the vehicle. In this example the vehicle 1 has come to a standstill and rolls in reverse somewhat before accelerating to continue. In the diagram the wheel loads acquired are correspondingly wider when the vehicle moves slowly, and narrower when the vehicle moves faster, because passing over the WIM sensor then takes less time.

(17) FIG. 6 diagrammatically shows the product of F(t) and v(t), which corresponds to weighting of the wheel loads F(t) with the speed v(t).

(18) To determine the weight G of the vehicle composition 1 the product of the wheel loads F(t) and of the speeds v(t) over the entire time of passing over is integrated as a whole or individually in relation to each wheel 2, and is multiplied by a calibration constant K that comprises calibration data of the WIM sensor. The weight G finally results from the sum of these results relating to all the wheels or to all the WIM sensors 5, 5′ that are arranged side-by-side, and together cover the entire roadway width 4.

(19) In a preferred embodiment the method according to the invention is characterised by the following method-related steps:

(20) a) the wheel load F.sub.i(t) of each wheel 2 ior, in the case of twin wheels, of each twin wheel i of the vehicle 1 is individually acquired as a time function, during rolling on the road 4, by WIM (weigh-in-motion) sensors;

(21) b) the speed v(t) of the vehicle, at least while all the wheels 2 or twin wheels i pass over a WIM sensor 5, is determined as a time function;

(22) c) the determined wheel loads F.sub.i(t) are synchronised with the determined speed values v(t) and are multiplied by each other F.sub.i.Math.v;

(23) d) the resulting products F.sub.i.Math.v are integrated over the time dt during the entire passing over of the vehicle;

(24) e) the integrals I.sub.i are multiplied by calibration constants K.sub.i and are added up for determining the weight G.

(25) According to the invention the speed v(t) of the vehicle 1 can be acquired by means of radar 7. This involves simple and mature technology. As an alternative to this, said speed can also be determined by means of the laser Doppler velocimetry method. This method uses a laser 7 directed towards the vehicle, obliquely to the direction of travel, with the reflected signals of said laser 7 as a result of the Doppler effect allowing conclusions relating to the speed of the vehicle.

(26) As an alternative to this the vehicle speed can be acquired by means of a device comprising an array of beams 9, which array is arranged in the direction of movement of the vehicle, through which array the wheels 2 of the vehicle 1 travel in turn as they travel over the WIM sensors 5. FIG. 7 shows one example of such an array of beams 9. Preferably, the distance between the individual beams 8 in the array 9 at most corresponds to the width of the WIM sensor 5, preferably to approximately half the width of the WIM sensor 5. This ensures that as each wheel travels over the WIM sensor several speed data readings are available, irrespective of the speed of travel. In contrast to this, in the case of radar measuring, the time interval between two measuring points is always constant. Thus at a fast speed of 200 km/h far fewer speed measurements for each instance of travelling over the WIM sensor 5 are acquired than is the case at slow speeds. Even when the vehicle 1 is at a standstill the measuring rate in the case of radar readings is constant. As a result of determination of the speed by an array of beams 9, which array is arranged in the direction of travel, the number of speed readings is always constant. Consequently the accuracy of weighting of the individual wheel loads is identical in respect of all the wheels 2 and of all the vehicles 1, irrespective of the speed of travel at the time. However, care should always be taken that the array 9 is at least sufficiently long so that when a vehicle with the maximum wheel size to be assumed passes, always at least one beam 8 of the array 9 is not interrupted by a wheel 2. This ensures that the speed can always be determined with sufficient accuracy, and no system error occurs, for example as a result of the vehicle 1 having come to a standstill on the WIM sensor 5.

(27) Preferably, by means of a device 11 it is determined which wheels/twin wheels 2 with all the trailers are to be allocated to a vehicle composition 1 in order to determine the total weight of the vehicle composition 1.

(28) A further option for improving the accuracy of determining the weight G of a vehicle 1 can be achieved in that downstream of the WIM sensor 5, at a distance of, for example, 0.2 to 1 m, a further WIM sensor 6 is installed across the entire roadway 4 in the section of road 3. As is the case with the first WIM sensor, this second WIM sensor 6 can comprise several WIM sensors 6, 6′ arranged in a row, with the totality of these sensors extending across the entire roadway 3. Hereinafter this is referred to as one WIM sensor 6, although a plurality of sensors can be involved. FIG. 7 shows a measuring arrangement 13 comprising a second WIM sensor 6.

(29) This second WIM sensor 6 is also connected to the evaluation unit 10 for transmitting the acquired data. The speed v(t) of course needs to be acquired until such time as the last wheel 2 of the vehicle composition 1 has fully passed over the second WIM sensor 6.

(30) Each wheel load with the associated speed is then analysed at each WIM sensor 5, 6. Depending on the plausibility of the results, a WIM sensor reading c relating to a wheel load is rejected and only the result of the other WIM measurement F.sub.i.sup.2 (t) is taken into account, or, if both results return plausible values, the average of both results is taken into account in further determining the vehicle weight g. Erroneous readings can arise, in particular, when a vehicle reverses.

(31) According to the invention, a toll for transit can be levied based on the determined weight data G. This can, for example, take place directly, by way of a debiting system, to an electronically communicating component carried in the vehicle 1, or by way of debiting an account that can be associated with the vehicle owner by way of identification of the vehicle 1.

(32) In this manner it is possible to establish toll plazas that conveniently can collect weight-specific toll amounts, in particular without enforced stopping or slowing-down of the vehicles 1, wherein the accuracy of weight measuring G is ensured at all speeds.

LIST OF REFERENCE CHARACTERS

(33) 1, 1′ Vehicle, vehicle composition 2 Wheel, twin wheel 3 Section of road 4 Road 5, 5′ Weigh-in-motion sensor; WIM sensor, row of WIM sensors 6, 6′ Second WIM sensor, second row of WIM sensors 7 Device for determining the speed, radar, laser Doppler velocimetry device 8 Beam 9 Array of beams 10 Evaluation unit 11 Device for determining the end of a vehicle composition 12 Measuring system 13 Measuring arrangement 14 Length of the footprint G Weight F(t) Time-dependent wheel load V(t) Time-dependent speed i Single wheel or twin wheel I Integral of F(t) v(t) K Calibration constant