WO2012087150A1

WO2012087150A1 - Road surface condition monitoring apparatus

Info

Publication number: WO2012087150A1
Application number: PCT/NO2011/000349
Authority: WO
Inventors: Per Magnussen
Original assignee: Edp Systems As
Priority date: 2010-12-22
Filing date: 2011-12-20
Publication date: 2012-06-28
Also published as: GB2486930A; GB201118114D0

Abstract

A road surface condition monitoring apparatus (10) includes a radiation source arrangement (150, 160) for generating radiation (170) for interrogating a road surface (100), and a detector arrangement (200, 210, 220) for receiving radiation reflected in operation from the road surface (100) to generate a corresponding reflected radiation signal (S3), and a computer arrangement (20) for receiving the reflected radiation signal (S3) for determining frictional properties of the road surface (100). The computer arrangement (20) is operable to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for a given position for determining the frictional properties of the road surface (100). The apparatus (10) further includes a distance measuring device (335) for measuring a distance between the road surface (100) and the radiation source arrangement (150, 160) and/or the detector arrangement (200, 210, 220), and for applying a compensation derived from the measured distance for compensating the reflected radiation signal (S3) so as to render the apparatus (10) insensitive to variations in the distance when determining the frictional properties of the road surface (100). The apparatus (10) is capable of being implemented to detect loose gravel.

Description

ROAD SURFACE CONDITION MONITORING APPARATUS

Field of the invention

The present invention relates to road surface condition monitoring apparatus. Moreover, the present invention also concerns methods of monitoring road surface condition. Furthermore, the present invention relates to software products recorded on machine readable data storage media, wherein the software products are executable on computing hardware for implementing aforesaid methods. Background of the invention

Satisfactory adhesion of vehicle tyres (USA: tires) to road surfaces is generally appreciated by vehicle drivers to be an important safety issue when driving, especially in icy, snowy and wet weather conditions. In contemporary vehicles, automatic braking system (ABS) functionality is routinely provided in top-of-range vehicle models and operates by detecting a sudden angular acceleration of vehicle wheel rotation with an associated sudden drop in wheel torque. ABS functionality operates to maintain a braking force applied to vehicle wheels at just below a threshold where wheel slip occurs. However, ABS does not seek to monitor actual road surface condition and therefore is unable to anticipate potentially hazardous road conditions to be encountered at a future time.

It is known from a published PCT patent application no. WO2004/016485 A1 (Nederlandse Organisate voor Toegepastnatuurwe Tenschappelijk Onderzoek TNO) to employ a configuration of diverse sensors to sense properties of a road surface and therefrom deduce a potential frictional characteristic of the road surface. However, the configuration of diverse sensors is potentially costly and complex to implement, and is also potentially degraded by dirt and other contamination often encountered on undersides of vehicles after prolonged use. So far, there appears to be a lack of commercial vehicle manufacturers which have attempted to provide road surface condition monitoring functionality in their commercial production vehicles, and a generally tendency amongst contemporary vehicle manufacturers has been to provide solely well-known ABS functionality.

Road surface conditions are prone in practice to vary greatly, with different types of asphalt being employed in different sections of road which has tended to confuse contemporary road surface monitoring apparatus. Moreover, known types of camera-based road inspection systems tend to require considerable computing resources to function, thereby rendering them expensive to manufacture on account of a cost of computer parts required. Furthermore, camera-based systems are also susceptible to generate false results in an event that their associated camera field of view is obscured by road debris after prolonged use. This variability of road surface conditions has tended to confuse contemporary road surface monitoring apparatus such that reliable detection of films of oil, thin ice layers and slippery organic debris on road surfaces has been difficult to implement reliably. In consequence, road friction monitoring has not substantially advanced beyond ABS.

Summary of the invention

The present invention seeks to provide a road surface condition monitoring apparatus which is more effective and easier to implement than known contemporary road surface condition monitoring apparatus.

Moreover, the present invention seeks to provide a method of monitoring road surface condition which is more reliable and easier to implement.

According to a first aspect of the present invention, there is provided a road surface condition monitoring apparatus as claimed in appended claim 1 : there is provided a road surface condition monitoring apparatus including a radiation source arrangement for generating radiation for interrogating a road surface, and a detector arrangement for receiving radiation reflected in operation from the road surface to generate a corresponding reflected radiation signal (S3), and a computer arrangement for receiving the reflected radiation signal (S3) for determining frictional properties of the road surface, characterized in that the computer arrangement is operable to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for a given position for determining the frictional properties of the road surface.

The invention is of advantage in that comparing measured and expected radiation for a given position provides an indication of frictional properties without friction being tested by a small degree of slippage as occurs with conventional ABS. The invention is also beneficial in that it is susceptible to being used to provide advanced warning of road surface friction properties.

Optionally, the road surface condition monitoring apparatus further includes a distance measuring device for measuring a distance between the road surface and the radiation source arrangement and/or the detector arrangement, and for applying a compensation derived from the measured distance for compensating the reflected radiation signal so as to render the apparatus insensitive to variations in the distance when determining the frictional properties of the road surface.

Optionally, the road surface condition monitoring apparatus further includes a filtering arrangement for filtering the reflected radiation signal (S3) for identifying signal components therein corresponding to shadows cast by gravel at the road surface, and a comparison arrangement for comparing the signal components with one or more reference values for determining whether or not loose gravel is present at the road surface. Optionally, the apparatus includes one or more radiation tubes for providing a path for the radiation for interrogating the road surface and the radiation reflected from the road surface to propagate from the radiation source arrangement and to the detector arrangement respectively, wherein the apparatus further includes a fan arrangement for providing a flow of air through the one or more radiation tubes for expelling contamination from entering into the one or more tubes.

Optionally, the road surface condition monitoring apparatus is implemented so that the computer arrangement is operable to employ a mathematical model for determining the frictional properties of the road surface from at least the expected reflected radiation signal (Rexp) and the reflected radiation (R), wherein the mathematical model is based upon at least one of: a neural network, a physical model and a measurement database.

Optionally, the fan arrangement includes a heater arrangement in an air flow generated by the fan arrangement when in operation, wherein the heater arrangement is arranged to heat the one or more radiation tubes to reduce blockage thereof by snow and ice.

Optionally, the road surface condition monitoring apparatus is implemented such that the radiation source arrangement is operable to generate modulated radiation for interrogating the road surface, and the receiver arrangement is adapted to demodulate the reflected radiation received thereat to generate the reflected radiation signal (S3). Such an approach is capable of rendering the apparatus insensitive to pseudo-constant ambient radiation at the road surface, for example sunlight and headlamps of other vehicles.

Optionally, the road surface condition monitoring apparatus is implemented such that the radiation source arrangement is operable to generate one or more radiation components within at least one following frequency ranges: 800 nm to 1.5 μιη, 250 nm to 800 nm. More optionally, the road surface condition monitoring apparatus is implemented such that the computer arrangement is operable to adjust a phase angle between modulation applied to modulate the radiation for interrogating the road surface, and a reference signal (S2) employed to demodulate the reflected radiation received at the detection arrangement. Optionally, the road surface condition monitoring apparatus is implemented so that the radiation source arrangement includes one or more of: light emitting diodes, organic light emitting diodes, laser diodes, nanowire light emitting devices, incandescent devices.

Optionally, the road surface condition monitoring apparatus further includes a temperature sensor arrangement for measuring a temperature in a proximity of the road surface or of the road surface.

Optionally, the road surface condition monitoring apparatus is implemented such that the temperature sensor arrangement includes an aspirated thermometer for measuring the temperature in the proximity of the road surface. Alternatively, or additionally, the temperature sensor arrangement includes at least one pyrometer-type temperature sensor.

Optionally, the road surface condition monitoring apparatus further includes a communication arrangement coupled to the computer arrangement for communicating to other apparatus data including geographical position references (x, y) pertaining to the apparatus together with information pertaining to the measured reflected radiation (R) for use by the other apparatus as expected reflected radiation (R_exp). More optionally, the road surface condition monitoring apparatus is implemented so that the communication arrangement includes wireless communication apparatus. The wireless communication apparatus is optionally contemporary wireless Internet, 3G mobile network, 4G mobile network.

Optionally, the road surface condition monitoring apparatus includes a position determining arrangement implemented by way of at least one of: GPS, GPRS for determining the given position.

According to a second aspect of the invention, there is provided a tyre surface condition monitoring apparatus including a radiation source arrangement for generating radiation for interrogating a tyre surface, and a detector arrangement for receiving radiation reflected in operation from the tyre surface to generate a corresponding reflected radiation signal (S3), and a computer arrangement for receiving the reflected radiation signal (S3) for determining frictional properties of the tyre surface, characterized in that the computer arrangement is operable to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for determining the frictional properties of tyre surface; and the apparatus further includes a distance measuring device for measuring a distance between the road surface and the radiation source arrangement and/or the detector arrangement, and for applying a compensation derived from the measured distance for compensating the reflected radiation signal (S3) so as to render the apparatus insensitive to variations in the distance when determining the frictional properties of the road surface. According to a third aspect of the invention, there is provided a road maintenance system including one or more vehicles equipped with apparatus pursuant to the first aspect of the invention, wherein the apparatus is employed to monitor road surfaces and to provide information to road maintenance service facilities for maintaining the road surfaces.

According to a fourth aspect of the invention, there is provided a method of monitoring a road surface condition using a road surface monitoring apparatus including:

(a) using a radiation source arrangement for generating radiation for interrogating a road surface;

(b) using a detector arrangement for receiving radiation reflected in operation from the road surface to generate a corresponding reflected radiation signal (S3); and

(c) using a computer arrangement for receiving the reflected radiation signal (S3) for determining frictional properties of the road surface,

characterized in that the method includes using the computer arrangement to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for a given position for determining the frictional properties of the road surface.

Optionally, the method includes employing a distance measuring device for measuring a distance between the road surface and the radiation source arrangement and/or the detector arrangement, and for applying a compensation derived from the measured distance for compensating the reflected radiation signal (S3) so as to render the frictional properties insensitive to variations in the distance.

Optionally, the method includes using one or more radiation tubes of the apparatus for providing a path for the radiation for interrogating the road surface and the radiation reflected from the road surface to propagate from the radiation source arrangement and to the detector arrangement respectively, and using a fan arrangement of the apparatus for providing a flow of air through the one or more radiation tubes for expelling contamination from entering into the one or more tubes.

It will be appreciated that features of the invention are susceptible to being combined in various combination without departing from the scope of the invention as defined by the appended claims.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1A is a schematic illustration of a road surface monitoring apparatus pursuant to the present invention;

FIG. 1 B is a schematic illustration of a road surface monitoring apparatus pursuant to the present invention as in FIG. 1A with an addition of an ultrasonic road surface distance measuring sensor for enabling a height of the apparatus above the road surface to be determined, and thereby a height compensation to be applied by the apparatus to optical road surface measurements to render the optical road surface measurements insensitive to a distance between the apparatus and the road surface over a limited range of the distance;

FIG. 2A is an illustration of a first configuration of a transmitting arrangement and sensing arrangement of the apparatus of FIG. 1 in front view;

FIG. 2B is an illustration of the first configuration of FIG. 2A in side view;

FIG. 3 is an illustration of a second configuration of the transmitting arrangement and sensing arrangement of the apparatus of FIG. 1 disposed at a single side of a vehicle wheel;

FIG. 4 is an illustration of a practical implementation of component parts of the transmitter arrangement and sensing arrangement of the apparatus for monitoring properties of a road surface;

FIG. 5 is an illustration of a practical implementation of component parts of the transmitter arrangement and sensing arrangement of the apparatus for monitoring properties of a tyre (US: tire) to grip onto the road surface; and

FIG. 6 is an illustration of a system including the apparatus of FIG. 1 mounted upon or in vehicles coupled via wireless to a server database.

In the accompanying diagrams, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non- underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing. Description of embodiments of the invention

In overview, the present invention is concerned with a road surface condition monitoring apparatus which is operable to measure properties of a road surface; the surface is susceptible, depending upon weather conditions, to be one or more of: dry, covered in a layer of ice, covered in a layer of snow, wet, covered in organic debris such as leaves, covered in a thin layer of oil, covered in loose gravel. As a further complication, road surface material in a dry clean state can vary greatly depending upon its age, composition, state of repair; for example, cobblestones, asphalt, clay-stone tracks and polymer materials such as paints are often encountered. A contemporary problem with known road surface measuring apparatus is that there is often too much variability in road surface material and condition such that additional surface covering due to precipitation, for example rain and ice, is difficult to detect reliability. In consequence, known road surface monitoring apparatus is potentially susceptible to generate false alarms which can be potentially distracting to a driver of a vehicle fitted with such apparatus. The present invention addresses such known limitations by employing a simple robust potentially low-cost sensor arrangement coupled to an on-vehicle computer, for example a microcontroller provided with associated data memory. The sensor arrangement provides the computer with measured characteristics of a given road surface, and the computer is provided with a position indication, for example from a GPS and/or GPRS spatial position location apparatus, for determining coordinates of the given position together with a database having data associating spatial positions (x, y) of the vehicle to corresponding expected measured characteristics R_eXp(x, y) for the spatial positions (x, y). Moreover, apparatus pursuant to the present invention beneficially includes a height measurement arrangement as a part of the sensor arrangement, for example implemented using ultrasound reflection and/or microwave reflection, for measuring a height of the apparatus over the road surface, so that the apparatus is operable to apply a height compensation to measurements made by the apparatus of the road surface, so that the apparatus is not affected by changes in height of the apparatus over the road surface when in operation, at least for a limited of such height.

Referring to FIG. 1A, there is shown a road surface condition monitoring apparatus indicated generally 10. The apparatus 10 includes a computer 20 including a data processor and data memory for executing software products recorded on a data storage medium for executing methods pursuant to the present invention. The apparatus 10 further includes a transmitter arrangement and sensing arrangement 30, an aspirated thermometer arrangement 40 for sampling air near a road surface 100, together with a GPS and/or GPRS position sensing unit 50; optionally, the thermometer arrangement 40 is implemented using one or more pyrometers. In operation, the apparatus 10 is mounted upon or in a vehicle 5 shown in FIG. 6 and transported around upon or in the vehicle 5 within a given geographical region. The GPS and/or GPRS position sensing unit 50 determines a substantially instantaneous position (x, y) of the vehicle 5 within the geographical region and provides corresponding information as a signal S5 to the computer 20. A flow of air 330 is drawn from an immediate vicinity of the road surface 100 into a first end of a flow tube 300 by way of a partial vacuum generated by a fan unit 310, for example a series of one or more axial fans or a miniature centrifugal fan. The flow 330 passes by a thermocouple sensor 320 to generate a signal S4 indicative of road surface temperature to the computer 20. As an alternative or addition to employing the aspirated thermometer 40, an infrared sensor, for example a pyrometer, is directed towards the road surface 100 to assist to generate the signal S4. As aforementioned, the signal S4 is indicative of a surface temperature of the road surface 100.

The computer 20 is operable to generate a strobe signal S1 , for example a 1 :1 mark-space ratio square-wave signal at a frequency in a range of 1 kHz to 10 kHz at an amplitude of 10 Volts peak-to-peak with a minimum OFF potential of 0 Volts and a maximum ON potential of 10 Volts. The signal S1 is applied to a current amplifier 150 which controls a corresponding signal S10 which is applied to an arrangement of one or more radiation emitters 160, for example one or more of laser diodes, light emitting diodes (LED), organic LEDs, nanowire- based high efficiency light emitter (for example Zinc Oxide nanowire devices) or similar. Optionally, the one or more radiation emitters 160 are implemented in a more conventional manner, for example using incandescence sources provided with modulation devices such as light cells or rotating mirrors to modulate light emitted from the incandescent sources. In operation, the arrangement 160 generates negligible radiation when the signal S1 is 0 Volts and nearly their maximum light output when the signal S1 is 10 Volts. The arrangement 160 includes, for example, an array of light emitting diodes; certain diodes of the arrangement 160 are operable to emit radiation at wavelengths longer than circa 800 nm, for example in a range 800 nm to 1.5 μιτι wavelength, namely in a near-infrared band, whereas other of the diodes 160 are operable to emit over a broad spectrum of wavelengths within a human visible radiation spectrum, namely from 800 nm to 250 nm. Optionally, the arrangement 160 is operable to generate near-infrared radiation and/or visible radiation, for example controllable via an additional control signal generated by the computer 20 to complement the signal S1. The arrangement 160 is operable to generate an interrogating beam 170 which impinges in operation onto the road surface 100, wherefrom a portion of the impinging radiation is reflected and received at a detector arrangement 200 including one or more photosensors, for example phototransistors. Beneficially, the arrangement of emitters 160 and the detector arrangement 200 have a temporal bandwidth which is at least an order of magnitude greater than a fundamental frequency of signal components in the signal S1 , namely at least an order of magnitude greater frequency response than a frequency of modulation employed. On receiving radiation reflected from the road surface 100, the detector arrangement 200 generates a signal S11 which is amplified by an analogue amplifier 210 to generate a corresponding amplified signal which is then demodulated via a synchronous demodulator 220 to generate a demodulated signal S3. The synchronous demodulator is beneficially implemented using one or more analogue switches, for example of a type CD4016 manufactured by various semiconductor manufacturers; alternatively, the synchronous demodulator can be implemented digitally, for example in a high-speed RISC- type microcontroller. Use of strobed radiation for implementing the sensing arrangement 30 is beneficial for removing effects from ambient sunlight, from street lights, from other vehicle lights and so forth, so that such pseudo-constant extraneous sources do not contribute to the signal S3. The synchronous demodulator 220 is provided with a strobe signal S2 generated by the computer 20. The strobe signal S2 is of a similar frequency to the signal S1 , but the computer 20 is optionally operable to trim a phase difference between the signals S1, S2 so that a maximum output in any given area of the road surface 100 is adjusted to a maximum; in other words, the computer 20 is operable to adjust a phase difference between the signals S1 , S2 to try to compensate for any signal phase changes occurring at the arrangement of emitters 160, at the detector arrangement 200 and at the amplifier 210.

As an alternative to employing strobed radiation, namely strobed modulation, for interrogating the road surface 100, other types of modulation are optionally alternatively or additionally employed, for example: frequency modulation, phase-shift modulation, amplitude modulation when of a different form to the strobed radiation.

The apparatus 10, when installed and functioning on a road vehicle, operates according to a method which includes following steps:

(a) determining a geographical position (x, y) of the vehicle 5 by using the position sensing unit 50; (b) measuring reflected radiation from the road surface 100 using the sensing arrangement 30, namely generating a signal R(x, y), wherein R is the magnitude of the measured reflected radiation;

(c) measuring a surface temperature T(x, y) of the road surface 100 using the thermometer 40;

(d) determining from preloaded data in the data memory of the computer 20 expected values of reflected radiation R_eXp(x, y) from the road surface 100 for the determined position of the vehicle; and

(e) using a numerical model of the road surface M(x, y, R_exp(x, y), T) programmed into the software executed by the computer 20 to determine a likely frictional property of the road surface 100 in respect of tyre adhesion thereto during driving.

Optionally, temperature sensing can be omitted. Optionally, a step of applying height compensation is included in the method for rendering measurements from the sensing arrangement 30 insensitive to their height over the road surface 100, for example as a result of varying vehicle loading.

The numerical model is beneficially based on one or more of:

(i) measurements of the reflected radiation R of the road surface 100 made under dry conditions at a temperature well above water freezing point (0 °C), for example at 20 °C;

(ii) a neural network programmed with previous measurements of road surface friction condition, wherein the neural network is provided with inputs of R_exp, R and T together with an indication of frictional properties of the road surface 100; and

(iii) using a physical numerical model based upon temperature, expected reflected radiation R_exp and measured reflected radiation R.

Optionally, a combination of two or more of (i), (ii) and (iii) is employed and the computer 20 is operable to select a most reliable indication amongst them, for example based upon sensitivity analysis determined by applying small perturbations on the parameters R, R_exp and T.

Optionally, when the temperature T is well above freezing point, for example 20 °C, the measured values of reflected radiation R(x, y) is employed to update the computer's 20 own database of expected reflected radiation R_exp(x, y), or communicated, for example via wireless 105, to update the expected radiation of other vehicles 5 which are similarly equipped with the apparatus 10. Optionally, as illustrated in FIG. 1B, the apparatus 10 includes a distance measuring device 335 for measuring a distance between arrangement of emitters 160 and the detector arrangement 200, by way of providing a signal S20 to the computer 20. The distance measuring device 335 is beneficially implemented using microwave radar and/or ultrasonic distance measurement. For example, sound has a velocity in air of approximately 330 metres/second, such that a 0.3 metre distance for an ultrasonic pulse train of circa 40 kHz frequency and five cycles duration takes about 1 millisecond to propagate from the device 335 to a road surface and back to the device again for generating the signal S20. The computer 20 is beneficially operable to apply a correction to the signal S3, for example a simply polynomial-based multiplying compensation of the signal S3 to render the apparatus 10 insensitive to variations of height of the apparatus 10 over the road surface, for example to compensate to changes due to tyre pressure, vehicle weight loading and event the apparatus being transferred from one vehicle to another. Such compensations simplifies installation of the apparatus 10 and also enables it to provide highly accurate measurement results enabling comparison of measurements derived from one vehicle to another. Such height compensation can either be implemented frequently, for example in real time to compensate for movements in vehicle suspension system, or occasionally to account for changes in vehicle tyre pressure and/or vehicle weight loading and/or vehicle wheel/tyre change. Optionally, the height of the apparatus 10 as measured by the device 335 is provided as a measurement parameter for communicating to a central database, for example for data processing and/or compensation purposes.

On account of the apparatus 10 measuring optical reflection, it is desirable that the apparatus 10 be mounted onto the vehicle 5 in such a manner that it is not directly struck by water and particles flung from wheels of the vehicle 5 due to centrifugal forces. As illustrated in FIG. 2A and FIG. 2B, the arrangement of emitters 160 and the detector arrangement 200 are spatially positioned away from a plane 410 of a wheel and associated tyre 400 of the vehicle 5 in respect of which they are mounted, for example with the arrangement of emitters 160 disposed at a first side of the wheel 400, and the detector arrangement 200 at a second side of the wheel 400 as shown in FIG. 2A. The arrangement of emitters 160 and the detector arrangement 200 are also beneficially placed up-stream or down-stream of the wheel 400 so that the wheel 400 does not obscure radiation beams from the arrangement of emitters 160 and to the detector arrangement 200, for example as illustrated in FIG. 2B. Optionally, the arrangement of emitters 160 and the detector arrangement 200 are mounted to one side of the wheel 400 as illustrated in FIG. 3, with the road surface 100 being sensed up-stream of the tyre 400 or down-stream of the tyre 400, most preferably, the friction is measured upstream of the tyre in respect of a forward direction of movement of the vehicle 5. A practical implementation of the arrangement of emitters 160 and the detector arrangement 200 is illustrated in FIG. 4. In FIG. 4, the arrangement of emitters 160 and the detector arrangement 200 are housed within a protective enclosure 480 which includes an optical isolating wall 490 to prevent radiation generated by the arrangement of emitters 160 passing directly to the detector arrangement 200. The enclosure includes a fan arrangement 450, for example implemented using one or more axial fans or a small centrifugal fan, for blowing air through the enclosure 480 and out through its radiation tubes 470 to maintain the enclosure 480 and its tubes 470 free of debris by blowing away any particulate matter thrown up by centrifugal force by rotating wheels of the vehicle. Optionally, a particle filter 430 is included up-stream of the fan arrangement 450 to prevent an interior of the enclosure 480 and its internal components from being covered in obscuring particles over a prolonged period of operation. Down-stream of the fan arrangement 450 is an optional heater arrangement 460 controlled by a signal S12 from the computer 20; the heater arrangement 460 is beneficially a ceramic heater element which is energized by commands from the computer 20, for example in an event that the temperature T is less than +5 °C, for warming the enclosure 480 during cold conditions, for example when snowing, to prevent ice and snow forming onto the enclosure 480 of any of its associated radiation tubes 470 when in use at lower temperature near freezing point and below. Beneficially, the tubes 470 are fabricated from extruded aluminium and their inside surface are painted or anodized to exhibit a substantially white colour. Alternatively, the tubes 470 are formed by machining holes into a block of material. They alternatively, the tubes 470 are formed in a moulded assembly, for example a plastics material moulded assembly. Air blown by the fan arrangement 450 and exiting via the tubes 470 as air jets 420 does not affect or otherwise inhibit or attenuate radiation from the arrangement of emitters 160 reaching the road surface 100, nor affect reflected radiation reflected from the road surface 100 reaching the detection arrangement 200. Such an arrangement avoids a need for using optical windows which tend to become occluded and contaminated by debris which can effect their optical transmission. The tubes 470 are beneficially angularly aligned so that their elongate principal axes are substantially parallel to ray paths of radiation from the arrangement of emitters 160 and to the detection arrangement 200 as illustrated. The tubes 470 beneficially have a length-to-diameter ratio in a range of 2:1 to 10:1 , namely the tubes are beneficially elongate components, for example elongate thin-walled components. Beneficially, the tubes 470 have a diameter in a range of 3 mm to 10 mm, and wall thickness in a range of 0.5 mm to 1.5 mm. Optionally, the tubes 470 are of rectangular cross-section to enables them to be arranged in a bunch of parallel tubes. The enclosure 480 is beneficially mounted within vehicle wheel arches, on an underside of the vehicle 5 facing the road surface, at a rear portion of the vehicle 5, at a front portion of the vehicle 5. Optionally, as aforementioned, the tubes 470 are machined and/or moulded as an array of holes in a block which is employed for constructing the apparatus 10.

Grip of a vehicle on the road surface 100 is both a function of the road surface 100 and also a function of status and quality of tyres of the vehicle 5. Optionally, the apparatus 10 can be adapted to measure characteristics of surfaces of tyres of the vehicle by a variant of the apparatus 10 as illustrated in FIG. 5. In FIG. 5, the arrangement of emitters 160 is implemented by a single source, for example one or more laser diodes 500 providing a collimated strobed beam of aforementioned radiation which is passed via an optical scanning component 510, for example an actuated mirror, and via the tube 470 to scan a surface 520 of a tyre of a wheel 400 of the vehicle. The scanning component 510 is beneficially operable to deflect the beam of radiation from the laser diode 500. Radiation reflected from the tyre is received at the detection arrangement 200 to generate a received signal which is, as aforementioned, synchronously demodulated to generate a signal for the computer 20. The computer 20 is operable to receive the synchronously demodulated signal from the detection arrangement 200 and its synchronous demodulator and therefrom, in association with scanning from the scanning component 510, acquire data which describes a substantially transverse profile of the tyre from which frictional properties can be derived, for example whether the tyre is new or is severely worn.

Beneficially, a plurality of apparatus 10 pursuant to the present invention are furnished with a flow of air from the fan arrangement 450 which is commonly shared by the plurality of apparatus 10. Moreover, analysis data 60 provided by the apparatus 10 in operation is beneficially employed in a system 8 as illustrated in FIG. 6 to provide a driver of the vehicle 5 with warnings regarding potential friction problems of the road surface, for example via visual dash-board display warnings or similar. Beneficially, the data 60 is provided via a communication arrangement, for example, a wireless and/or Internet data communication link 105, to road authorities 505 responsible for maintaining roads; for example, the apparatus 10 is potentially useable for automatically warning road authorities 505 regarding road gritting and road snow clearance activities. The road authorities 505 beneficially support a server-based database for real-time information regarding road surface conditions. The apparatus 10 is capable of being adapted to measure loose gravel upon the road surface 100 by way of at least one of the arrangement of emitters 160 being a laser diode forming a compact spot, by way of collimated radiation, onto the road surface 100 of around 1 mm diameter of less. When gravel is present, the detection arrangement 200 receives a reflected signal component including shadow information pertaining to shadows cast by the gravel, wherein the shadow information is determinable by performing a Fourier spectrum analysis of frequency components and amplitude present in the signal S3 generated by the detection arrangement 200. Such Fourier analysis employs frequency filtering of the signal S3 provided from the detection arrangement 200 and is beneficially performed using a Fast Fourier Transform or similar algorithms executed upon the computer 20; optionally, digital recursive filtering is employed to a FIFO memory buffer of measured results corresponding to the signal S3, wherein parameters for the recursive filtering is varied as a function of speed of travel of the vehicle 5. Beneficially, specific frequency ranges typical for identifying loose gravel are employed, wherein the frequency ranges are dynamically adjusted as a function of a travelling speed of the vehicle 5. When signal energy in frequency ranges corresponding to loose gravel exceeds a threshold value, the apparatus 10 is operable to provide an analysis to the driver of the vehicle 5, optionally a warning, that loose gravel is present on the road surface 100.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "consisting of, "have", "is" used to describe and claim the present invention are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims

1. A road surface condition monitoring apparatus (10) including a radiation source arrangement (150, 160) for generating radiation (170) for interrogating a road surface (100), and a detector arrangement (200, 210, 220) for receiving radiation reflected in operation from the road surface (100) to generate a corresponding reflected radiation signal (S3), and a computer arrangement (20) for receiving the reflected radiation signal (S3) for determining frictional properties of the road surface (100), characterized in that the computer arrangement (20) is operable to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for a given position for determining the frictional properties of the road surface (100).

2. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the apparatus (10) further includes a distance measuring device (335) for measuring a distance between the road surface (100) and the radiation source arrangement (150, 160) and/or the detector arrangement (200, 210, 220), and for applying a compensation derived from said measured distance for compensating the reflected radiation signal (S3) so as to render the apparatus (10) insensitive to variations in said distance when determining the frictional properties of the road surface (100).

3. A road surface condition monitoring apparatus (10) as claimed in claim 1 or 2, characterized in that the apparatus (10) further includes a filtering arrangement for filtering the reflected radiation signal (S3) for identifying signal components therein corresponding to shadows cast by gravel at the road surface (100), and a comparison arrangement for comparing said signal components with one or more reference values for determining whether or not loose gravel is present at said road surface (100).

4. A road surface condition monitoring apparatus (10) as claimed in claim 1 , 2 or 3, characterized in that the apparatus (10) includes one or more radiation tubes (270) for providing a path for the radiation (170) for interrogating the road surface (100) and the radiation reflected from the road surface (100) to propagate from the radiation source arrangement (160) and to the detector arrangement (200, 210, 220) respectively, wherein the apparatus further includes a fan arrangement (450) for providing a flow of air through the one or more radiation tubes (470) for expelling contamination from entering into the one or more tubes (470).

5. A road surface condition monitoring apparatus (10) as claimed in claim 4, characterized in that the fan arrangement (450) includes a heater arrangement (430) in an air flow generated by the fan arrangement when in operation, wherein the heater arrangement (430) is arranged to heat the one or more radiation tubes (270) to reduce blockage thereof by snow and ice.

6. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the computer arrangement (20) is operable to employ a mathematical model for determining the frictional properties of the road surface (100) from at least the expected reflected radiation signal (Rexp) and the reflected radiation (R), wherein the mathematical model is based upon at least one of: a neural network, a physical model and a measurement database.

7. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the radiation source arrangement (150, 160) is operable to generate modulated radiation for interrogating the road surface (100), and the receiver arrangement (200, 210, 220) is adapted to demodulate the reflected radiation received thereat to generate the reflected radiation signal (S3).

8. A road surface condition monitoring apparatus (10) as claimed in claim 7, characterized in that the radiation source arrangement (200, 210, 220) is operable to generate one or more radiation components within at least one following frequency ranges: 800 nm to 1.5 μητι, 250 nm to 800 nm.

9. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the radiation source arrangement (200, 210, 220) includes one or more of: light emitting diodes, organic light emitting diodes, laser diodes, nanowire light emitting devices, incandescent devices.

10. A road surface condition monitoring apparatus (10) as claimed in claim 7, characterized in that the computer arrangement (20) is operable to adjust a phase angle between modulation applied to modulate the radiation for interrogating the road surface, and a reference signal (S2) employed to demodulate the reflected radiation received at the detection arrangement (200, 210, 220).

11. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the apparatus (10) further includes a temperature sensor arrangement (300, 310, 320) for measuring a temperature in a proximity of the road surface (100) or of the road surface (100).

12. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the temperature sensor arrangement (300, 310, 320) includes an aspirated thermometer for measuring the temperature in the proximity of the road surface (100).

13. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the apparatus (10) further includes a communication arrangement (105) coupled to the computer arrangement (20) for communicating to other apparatus data including geographical position references (x, y) pertaining to the apparatus (10) together with information pertaining to the measured reflected radiation (R) for use by the other apparatus as expected reflected radiation (R_exp).

14. A road surface condition monitoring apparatus (10) as claimed in claim 13, characterized in that the communication arrangement (105) includes wireless communication apparatus.

15. A road surface condition monitoring apparatus (10) as claimed in claim 1 , characterized in that the apparatus (10) includes a position determining arrangement (50) implemented by way of at least one of: GPS, GPRS for determining the given position.

16. A tyre surface condition monitoring apparatus (10) including a radiation source arrangement (150, 160) for generating radiation (170) for interrogating a tyre surface (400), and a detector arrangement (200, 210, 220) for receiving radiation reflected in operation from the tyre surface (100) to generate a corresponding reflected radiation signal (S3), and a computer arrangement (20) for receiving the reflected radiation signal (S3) for determining frictional properties of the tyre surface (100), characterized in that the computer arrangement (20) is operable to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_exp) for determining the frictional properties of tyre surface (100); and the apparatus (10) further includes a distance measuring device (335) for measuring a distance between the tyre surface (100) and the radiation source arrangement (150, 160) and/or the detector arrangement (200, 210, 220), and for applying a compensation derived from said measured distance for compensating the reflected radiation (S3) so as to render the apparatus (10) insensitive to variations in said distance when determining the frictional properties of the tyre surface (100).

17. A road maintenance system (8) including one or more vehicles (5) equipped with apparatus (10) as claimed in any one of claims 1 to 16, characterized in that the apparatus (10) is employed to monitor road surfaces (100) and to provide information to road maintenance service facilities for maintaining the road surfaces (100).

18. A method of monitoring a road surface condition using a road surface monitoring apparatus (10) including:

(a) using a radiation source arrangement (150, 160) for generating radiation (170) for interrogating a road surface (100);

(b) using a detector arrangement (200, 210, 220) for receiving radiation reflected in operation from the road surface (100) to generate a corresponding reflected radiation signal (S3); and

(c) using a computer arrangement (20) for receiving the reflected radiation signal (S3) for determining frictional properties of the road surface (100),

characterized in that the method includes using the computer arrangement (20) to compare the reflected radiation signal (S3, R) with a corresponding expected reflected radiation signal (R_eXp) for a given position for determining the frictional properties of the road surface (100).

19. A method as claimed in claim 18, characterized in that said method includes employing a distance measuring device (335) for measuring a distance between the road surface (100) and the radiation source arrangement (150, 160) and/or the detector arrangement (200, 210, 220), and for applying a compensation derived from said measured distance for compensating the reflected radiation signal (S3) so as to render the frictional properties insensitive to variations in said distance.

20. A method as claimed in claim 18 or 19, characterized in that said method includes using one or more radiation tubes (270) of the apparatus (10) for providing a path for the radiation (170) for interrogating the road surface (100) and the radiation reflected from the road surface (100) to propagate from the radiation source arrangement (160) and to the detector arrangement (200, 210, 220) respectively, and using a fan arrangement (450) of the apparatus (10) for providing a flow of air through the one or more radiation tubes (470) for expelling contamination from entering into the one or more tubes (470).