A drive-over tire tread depth gauging system, use thereof, and method for gauging a tire tread depth of a moving vehilce

Abstract

The disclosure describes a system comprising a housing (110) comprising an optical opening (120), where the housing is configured to be embedded in a road (130), an optical scanner (150) arranged inside the housing, where the optical scanner (150) is configured to measure, through the optical opening (120) of the housing (110), the tread depth of the tire (140) as the tire rolls across the optical opening of the housing, a control unit (180) configured to activate the optical scanner (150), and a detection unit (170) arranged inside the housing (110) and configured to detect presence of a tire (140) at the optical opening (120) and send a detection signal in response to said detection. The control unit (180) is configured to activate the optical scanner (150) based on the received detection signal from the detection unit.

Description

A DRIVE-OVER TIRE TREAD DEPTH GAUGING SYSTEM, USE THEREOF, AND METHOD FOR GAUGING A TIRE TREAD DEPTH OF A MOVING VEHILCEField of disclosureThe disclosure relates to the field of optical systems, and especially a drive-over tire tread depth gauging system.Background

[0001] Tire treads are generally employed for improving the traction of tires with the ground, for example against wet surfaces by preventing hydroplaning. Treaded tires are particularly important in cold climates that are prone to snowfall and frost, as wide treads are commonly employed in order to give traction with snow and ice. Tire treads are unfortunately prone to wear, hence causing a reduction of traction over time, and eventually resulting in a need to replace the tire.

[0002] In order to maintain road safety, most jurisdictions have introduced requirements on tire tread depth. However, as it is generally the responsibility of the owner of the vehicle to ensure that the tread depths are within the legal limits, many vehicles may be found on the road equipped with tires that are not road legal. Increasing international travel, and varying requirements for tread depths across international border further contribute to a high number of vehicles on the road without road legal tires. The latter being a particular problem when freight is transported by road into a country with icy conditions from a country with a warm and generally frost free climate.

[0003] In order to improve road safety, various national authorities have recently started showing interest in installing automatic drive-over tire tread depth gauging sensors in the road that are configured to measure the tire tread depth of cars as these drive across the sensor. Several drive-over tire tread depth gauging sensors are already known in the art, but these have until now largely been employed inside, for example in garages and workshops.

[0004] A drive-over tire tread installed in the road will have a width corresponding to at least the width of the kind of vehicle expected to pass of the tire tread depth measurement, and may thereby comprise a plurality of measurement units. Each measurement unit will generate data, such as image data and distance data, which need to be processed in order to determine the tire's tread depth. Since the gauging system may be operating for long time periods, the amount of data may become an issue. It becomes relevant to make sure that only data necessary for the gauging operation needs to be processed.

[0005] The present disclosure describes a drive-over tire tread depth gauging system providing an efficient data management in relation to the tire tread depth measurements.Summary of the disclosure

[0006] The invention is defined by the appended independent claims, with embodiments being set forth in the appended dependent claims, in the following description and in the drawings. A first aspect of the present disclosure provides a drive- over tire tread depth gauging system, the system comprising a housing comprising an optical opening, where the housing is configured to be embedded in a road such that a tire of a vehicle can roll across the optical opening of the housing, an optical scanner arranged inside the housing, where the optical scanner is configured to measure, through the optical opening of the housing, the tread depth of the tire as the tire rolls across the optical opening of the housing, a control unit configured to activate the optical scanner, and a detection unit arranged inside the housing and configured to detect presence of a tire at the optical opening and send a detection signal in response to said detection. The control unit is configured to activate the optical scanner based on the received detection signal from the detection unit.

[0007] By using a detection unit to detect presence of a tire at the optical opening, unnecessary activation of the optical scanner may be avoided. When no tire is present at the optical opening, there may be no need for the optical scanner to perform a measurement. The optical scanner may then be inactive. The detection unit may provide an efficient way of only activating the optical scanner when needed. Further, by not having the optical scanner activated when no tire is present at the optical opening, unnecessary measurement data (e.g. image data, distance measurement data) may be avoided, and the amount of data processing needed by the system may be decreased. This becomes particularly relevant when the drive-over tire tread depth gauging system comprises a plurality of optical scanners, each generating e.g. high-resolution images. The amount of data to process then rapidly increases to large levels if not unnecessary data is avoided. Further, the optical scanner may comprise measurement instruments that transmit radiation that is desired do not propagate to the environment outside the optical opening, such as laser radiation that may be hazardous to the eyes of a human.

[0008] The detection unit may detect when the tire is no longer present at the optical opening, and based on such detection terminate the detection signal or issue astop signal. Such action from the detection unit may cause a deactivation or a termination of measurement of the optical scanner.

[0009] The detection unit may be arranged at a distance from the optical opening, with a line of sight to the optical opening. The detection unit is arranged inside the housing, which may be at a distance to the optical opening. The detection by the detection unit may be performed in a contactless manner in relation to the optical opening and the tire passing by the optical opening. The detection by the detection unit may be based on radiation transmitted from the detection unit. The detection unit may have a line of sight to the optical opening in order for radiation from the detection unit to reach the optical opening and a tire passing over.

[0010] The detection unit may be a radar unit. Using a radar to detect the presence of a tire at the optical opening may be a way to provide a fast detection, which may be capable of detecting the tire of a moving vehicle at a relatively high speed. Other alternatives of detection units providing a detection that is fast enough may be a laser detection or another detection unit based on radiation of light waves or radio waves. The radar unit may be provided with a radar lens configured to focus the radar measurement of the radar unit to a desired focus area.

[0011] The optical scanner, the control unit and the detection unit may together be arranged in a sensor unit, and the housing may comprise a plurality of such sensor units. The housing may comprise for instance two, four, eight, sixteen, or twenty-four sensor units. The housing may comprise between two and twenty- four sensor units.

[0012] The optical opening may extend from a first end to a second end along a moving direction of a tire of a moving vehicle over the drive-over tire tread depth gauging system. The second end may be downstream in the moving direction compared to the first end, and the detection unit may be configured to detect presence of a tire adjacent to the first end of the optical opening. The detection adjacent to the first end may provide that the detection unit may detect the presence of the tire as early as possible when the tire approaches the optical opening. If the detection unit is a radar unit provided with radar lens, the radar lens may be configured to focus the radar measurement to an area close to the first end of the optical opening.

[0013] The measurement of the tire at the optical opening by the optical scanner may be configured to be triggered by the detection signal issued by the detection unit. The activation of the optical scanner by the control unit may mean that the measurement of the tire is activated and thereby performed. The measurementof the tread depth of the tire may, at least partly, be triggered by the activation of the optical scanner by the control unit. The measurement by the optical scanner may, direct or indirect, be triggered by the detection signal.

[0014] The optical scanner may comprise the control unit. The control unit may be arranged inside the optical scanner, in combination with the optical scanner, or integrated with the optical scanner. Alternatively, the detection unit may comprise the control unit, or be arranged in combination with the detection unit, or arranged integrated with the detection unit. Alternatively, the control unit may be a physically separate unit from the optical scanner and / or the detection unit. The control unit may be arranged at a distance from the optical scanner and / or the detection unit. In some embodiments, the drive-over tire tread depth gauging system may comprise a plurality of sensor units each comprising an optical scanner and a detection unit, and one central control unit which receives detection signals from each detection unit, and activates the respective optical scanner or optical scanners based on the received detection signal or signals.

[0015] The optical scanner may comprise one or more out of the group of at least one camera, at least one laser triangulation scanner or at least one LED flash unit. The at least one camera (such as two cameras) may be provided to capture one or more camera images of the tire when activated to measure the tread depth of the tire. The camera image may be used for the determination of tread depth of the tire. The LED flash unit may be used to provide a light flash for the capturing of a camera image by the at least one camera. The laser triangulation unit may be used for measuring the tread depth of the tire by means of a laser measurement. The laser triangulation unit may comprise a laser transmitter and a laser receiver configured to provide the laser measurement. The optical scanner may comprise all of these three units, at least one of each. The drive- over tire tread depth gauging system may comprise a plurality of sensor units, each comprising such optical scanner.

[0016] The detection unit may be configured to detect presence of a tire at a distance of between 10-40 cm, preferably between 15-35 cm, from the detection unit. The detection unit may be configured to have a measurement focus at the desired distance. The accuracy and speed in the measurement may be improved by configuring the detection unit to measure at a desired distance. It may further avoid detection of other items passing over the optical opening at a larger distance, i.e. at a distance above the optical opening. The distance may substantially correspond to a distance from the detection unit arranged in the housing to the optical opening. If the detection unit is a radar unit provided witha radar lens, the radar lens may be configured to focus the radar measurement to the desired distance from the radar unit.

[0017] The drive-over tire tread depth gauging system may further comprise an aircleaning device configured to provide an air flow inside the housing for cleaning one or more of the optical scanner and the detection unit. The control unit may be configured to activate the air-cleaning device for cleaning of said one or more units based on reception of the detection signal from the detection unit. The aircleaning device may be used to reduce negative impact on subsequent measurements by the optical scanner by contaminants, such as water, snow, dust, sand, salt, gravel, or the like.

[0018] The drive-over tire tread depth gauging system may further comprise a housing lid configured to, in a closed position, cover the optical opening and in an open position enable visual communication between the optical scanner and a tire at the optical opening. The detection unit may be configured to detect an approaching vehicle by detecting vibrations in the housing and / or the housing lid. When detecting vibrations indicative of an approaching vehicle, the detection unit may further send an approaching signal to the control unit, which approaching signal may cause the housing lid to be moved to the open position. The detection of an approaching vehicle may be performed prior to detecting the presence of a tire at the optical opening. The housing lid may be in the closed position when the system is idle. When a vehicle is approaching, the detection unit may detect it and cause the housing lid to be opened. This may be performed at a rate fast enough for the housing lid to be in the open position when the tire of the approaching vehicle reaches the optical opening. When the detection unit subsequently detects the presence of the tire at the optical opening (now open after movement of the housing lid to the open position), the detection signal may be send causing the activation of the optical scanner as described above. The detection unit may be configured to, when the housing lid is in the closed position, detect vibrations in the housing and / or in the housing lid. The detection unit may be configured to detect vibrations at the location towards which it is directed and focused. Vibrations in the housing and / or housing lid may be indicative of an approaching vehicle and may cause the detection unit to send the approaching signal. The approaching signal may be a signal informing the control unit that a vehicle is approaching. The housing lid may provide a protection for the components in the housing during times when no measurements are being performed. After measurement of the tire tread depth, the housing lid may be moved to the closed position. The closing may be based on a predetermined time after measurement or after opening, or followinga detection of absence of vibrations by the detection unit. If the housing comprises a plurality of sensor units, each comprising a detection unit, only one of, or a selection of, or all of the detection units may be configured to detect vibrations in the housing and / or housing lid. The housing lid may be moved to the closed position as soon as at least one of the detection units has detected vibrations indicative of an approaching vehicle. The detection unit may be configured to identify whether the detected vibrations are the result of an approaching vehicle or of something else, and only send the approaching signal if it is determined that the vibrations are the result of an approaching vehicle.

[0019] A second aspect of the present disclosure provides a use of a drive-over tire tread depth gauging system according to any of the embodiments disclosed herein, for measuring the tread depth of a tire of a moving vehicle.

[0020] A third aspect of the present disclosure provides a method for gauging the tire tread depth of a moving vehicle, the method comprising the steps of providing a drive-over tire tread depth gauging system, wherein the drive-over tire tread depth gauging system is embedded in a road or road segment such that the top opening of the housing of the drive-over tire tread depth gauging system aligns with the surface of the road or road segment, detecting presence of a tire at the optical opening by means of the detection unit, based, at least in part, on the detection of a tire at the optical opening, issuing a detection signal to the control unit, and activating, based on the detection signal, the optical scanner of the drive-over tire tread depth gauging system to measure the tire tread depth of the tire detected at the optical opening.

[0021] The features of the embodiments of the drive-over tire tread depth gauging system presented above applies equally to corresponding embodiments of the method for gauging the tire tread depth of a moving vehicle.Brief description of the drawings

[0022] Figure 1 shows a schematic illustration of a drive-over tire tread depth gauging system embedded in a road,

[0023] Figure 2 shows a schematic perspective view of a drive-over tire tread depth gauging system according to an embodiment of the invention,

[0024] Figure 3a shows a side view of a schematic illustration of a drive-over tire tread depth gauging system according to an embodiment of the invention,

[0025] Figure 3b shows a side view of a schematic illustration of a drive-over tire tread depth gauging system according to an embodiment of the invention,

[0026] Figure 3c shows a side view of a schematic illustration of a drive-over tire tread depth gauging system according to an embodiment of the invention,

[0027] Figure 4 shows a side view of a schematic illustration of a drive-over tire tread depth gauging system comprising a plurality of sensor units according to an embodiment of the invention,

[0028] Figure 5 shows a schematic block scheme of an optical scanner, a detection unit and a control unit according to an embodiment of the invention,

[0029] Figure 6 shows a flowchart of a method according to an embodiment of the invention,

[0030] Figure 7a shows a schematic perspective view of a drive-over tire tread depth gauging system according to an embodiment of the invention,

[0031] Figure 7b shows a schematic perspective view of a drive-over tire tread depth gauging system according to an embodiment of the invention.Detailed description of the disclosure

[0032] In the following, general embodiments as well as particular exemplary embodiments of the disclosure will be described. References will be made to the accompanying drawings. It shall be noted, however, that the drawings are exemplary embodiments only, and that other features and embodiments may well be within the scope of the disclosure as claimed. Further, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality.

[0033] Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this disclosure pertains. Certain terms of art, notations, and other scientific terms or terminology may, however, be defined specifically as indicated below.

[0034] The present disclosure provides a drive-over tire tread depth gauging system 100. The drive-over tire tread depth gauging system 100 is configured to being embedded in a road 130 such that the tread depth of a tire may be measured as the vehicle equipped with said tire drives along the road 130 and across the drive-over tire tread depth gauging system 100. The drive-over tire tread depth gauging system 100 comprises a housing 110 with an optical opening 120, and an optical scanner provided in the housing 110. Figure 1 schematically illustrates a drive-over tire tread depth gauging system 100 embedded in a road 130. It will be appreciated that a drive-over tire tread depth gauging system 100 may generally be known in the art under different terminologies, e.g. a drive-over optical tread depth sensor, a tire tread scanner drive-over device, a tire tread scanner drive-over system or similar. The term gauge, may in the context of thepresent disclosure be understood as synonymous with terms such as measure or determine.

[0035] The drive-over tire tread depth gauging system 100 may, as schematically illustrated in figures 1 - 2, be embedded in a road 130 or road segment such that a vehicle may drive across the system 100 with at least one of its wheels passing over the optical opening 120 of the housing 110. The system 100 may ideally be embedded in a road 130 or road segment such that the top of the housing 110, and consequently the optical opening 120 of the housing 110, aligns with the surface of the road 130 or road segment. The optical opening 120 may generally be considered as provided in the top wall of the housing 110, and provides a physical connection between the interior and the exterior of the housing 110. The optical scanner 150 provided in the housing 110 may then through visual communication with the tire 140 through the optical opening 120 of the housing 110 gather optical data that may directly or indirectly be used in order to deduce the tread depth of said tire 140.

[0036] In order to stop any contaminant such as water, snow, dust, sand, salt, gravel and / or other types of debris from polluting optical scanner 150, the drive-over tire tread depth gauging system 100 may be provided with a housing lid 190 (see figures 7a-b). When not actively performing any measurements, the housing lid 190 may be used to cover the optical opening 120 of the housing 110, hence protecting the optical scanner 150 from typical environmental pollutants such as water, dust, sand, salt, pollen, snow and gravel.

[0037] The drive-over tire tread depth gauging system 100 further comprises a detection unit 170, which may be a radar unit, a laser unit, or the like. The detection unit 170 is configured to detect the presence of a tire 140 at the optical opening 120. The optical scanner 150 may then be inactive as long as no tire 140 is detected at the optical opening 120. As seen in figure 3a, the detection unit 170 is arranged in the housing 110 such that the presence of a tire at the optical opening 120 would be detected. When a tire 140 approaches the optical opening 120, as seen in figure 3b, the detection unit 170 will detect it, and issue a detection signal to a control unit 180. The control unit 180 is configured to active the optical scanner 150 in response to the detection signal being issued by the detection unit 170.

[0038] When the optical scanner 150 is activated, caused by the issuance of the detection signal, the measurement of the tire tread depth is activated, as illustrated in figure 3c.

[0039] The detection unit 170 may further detect when the tire 140 is no longer present at the optical opening 120, and based on such detection terminate the detectionsignal or issue a stop signal. Such action from the detection unit 170 may cause a deactivation or a termination of measurement of the optical scanner 150.

[0040] The optical scanner 150 described herein may be formed by one or more devices configured to be used for the measurement of the tire tread depth. Such devices may be one or more cameras 152, a laser triangulation device 154, and a LED flash 156. The laser triangulation device 154 may comprise two units, being one emitter unit and one receiver unit. If the optical scanner 150 comprises two or more of said devices, they may operate in interaction with each other. The detection signal may cause the camera 152 to capture an image of the tire 140. The detection signal may cause the laser triangulation device 154 to perform a laser measurement of the tire 140. The detection signal may cause the LED flash 156 to flash. The LED flash 156 may be configured to flash in a synchronized manner with the camera 152 to brighten the scene for the image capturing. In one embodiment, the optical scanner 150 may comprises one or two cameras 152, a LED flash 156, and a laser triangulation device 154, all configured to be activated by the detection signal.

[0041] The housing 110 may according to the present disclosure be any housing that is adapted to being embedded in a road or segment of a road such that a road vehicle may pass across the housing without causing any irreversible damage to the housing. The housing may for example be a casing of stainless steel, a concrete enclosure or a housing made of any other similar rigid material or combination of materials chosen in order to enable the housing to bear the weight of any type of standard road vehicle.

[0042] As will be appreciated by a person skilled in the art with knowledge of the present disclosure, the housing may generally take on a wide variety of shapes and sizes. The housing may generally be shaped such that it comprises a housing interior with a shape and size suitable for accommodating the optical scanner and detection unit. The housing may additionally be shaped and dimensioned such that the housing interior may accommodate additional equipment, such as for example communication equipment, and / or other auxiliary equipment. Communication equipment may for example comprise a transmitter and / or a sender configured to communicate data to and / or from the optical scanner from some remote source. Examples of auxiliary equipment may for example comprise one or more of a power source, control unit, a data processing device.

[0043] As schematically illustrated in figures 1, 3a-c, the housing 110 is adapted to being embedded in a road 130 or road segment. Being embedded in a road 130 or road segment may here be understood as being built in as a part of the road130 or road segment such that vehicles driving along the road 130 may drive across the housing 110 with one or more of their wheels passing directly over the housing 110. The system 100 may ideally be embedded in a road 130 or road segment such that the top of the housing 110, and consequently the optical opening 120 of the housing, aligns with the surface of the road 130 or road segment. Said alignment will result in a plane road surface, without the drive- over tire tread depth gauging system 100 creating any protruding bump in the road 130. As will be appreciated by a person skilled in the art with knowledge of the present disclosure, the exact way in which the housing 110 may be embedded may vary. The embedment may for example be provided though employment of expansion compensating mechanical joints that compensates for any thermal expansion mismatch between the road 130 and the housing 110. Alternatively, the embedment may be provided by simply placing and securing the housing 110 in a predesigned slot in the road 130 or road segment.

[0044] As schematically illustrated in figures 3a-c, the housing 110 is provided with an optical opening 120. The optical opening 120 is generally positioned on the housing 110 such that the optical opening 120 may provide a visual transmission between the interior of the housing 110 and the exterior top side of the housing 110 when the housing 110 is embedded in a road 130 or road segment. The exact size, shape and orientation of the optical opening 120 may vary, but are generally chosen such that the optical scanner 150 provided inside the housing 110 may obtain visual connection with a tire positioned over the optical opening 120. The optical opening 120 may be a physical opening between the interior and exterior of the housing 110, optionally with a size, shape and orientation that may be chosen in order to minimize the impact on a vehicle driving across the drive-over tire tread depth gauging system 100. A too large optical opening 120 may for example cause a tire 140 to be measured to fall a significant distance into the optical opening 120 as the vehicle with the tire 140 drives across the drive-over tire tread depth gauging system 100. On the contrary, a too small optical opening 120 may cause difficulties in obtaining a clear line of sight between the optical scanner 150 and the tire 140 to be measured.

[0045] Figures 1, 3a-c schematically illustrate an example of a 110 housing provided with an optical opening 120. The optical opening 120 is here illustrated with a length, L, and width, W, being perpendicular to one another, where the length L of the optical opening 120 being illustrated as being parallel with the driving direction, X, of a road 130 or road segment in which the housing 110 is embedded. A length L in the range from 5 cm to 10 cm has generally been found to be preferred, as such a width has been found to enable adequate line of sightbetween the optical scanner 150 while enabling most standard road tires to pass without causing an unacceptable obstacle to the vehicle carrying the tire. The housing 110 may, as schematically illustrated in figures 1, 3a-c, generally be provided with an optical opening 120 with a rectangular shape such that the width W of the optical opening 120 is larger than the length L. A width W larger than 50 cm has generally been found to be preferred in order ensure that a vehicle passing the drive-over tire tread depth gauging system 100 will actually have one of its tires pass over the optical opening 120 of the drive-over tire tread depth gauging system 100. In a preferred embodiment of the disclosure the optical opening 120 is shaped as a slit with a width > length.

[0046] The housing 110 may, as illustrated in figures 7a-b, further comprise a housing lid 190. The housing lid may be configured to, in a closed position (see figure 7a), cover the optical opening 120, and may be movable to an open position (see figure 7b). As will be appreciated by a person skilled in the art with knowledge of the present disclosure, the housing lid 190 may generally be moved between the closed and open position by employment of suitable moving means. The housing lid 190 may for example be moved between the closed and open position by employment of an actuator such as an electrical motor or an electromagnet. The moving means, such as an actuator, may further be controlled using a suitable control unit. The latter may for example be an on-site or remote computer.

[0047] The housing lid 190 may be moved between the closed and open position as a response to the detection of an approaching vehicle. An approaching vehicle may for example be detected using a camera next to the road, which may communicate a signal to the moving means, asking for the housing lid to be opened. In another embodiment of the disclosure, the housing lid 190 may be kept open between measurements. For example on a highway, an opening and closing cycle of the lid may depend on not only approaching cars, but also weather conditions and the speed / sequence approaching cars. It will be appreciated by a person skilled in the art with knowledge of the present disclosure that the duration of the opening of the housing lid 190 may vary significantly beyond the passing of a single car.

[0048] The detection unit 170 may be used for detection of an approaching vehicle. The detection of an approaching vehicle may be prior to the detection of a tire 140 and the optical opening 120. The detection of an approaching vehicle may be performed by the detection unit 170 (e.g. radar unit) when the housing lid 190 is in the closed position, closing the optical opening 120. The detection of an approaching vehicle may be made by the detection unit 170 by detectingvibrations in the housing 110 and / or the housing lid 190. The detection of an approaching vehicle by the detection unit 170 may cause the detection unit 170 to issue an approaching signal which may cause the housing lid 190 to move to the open position. The approaching signal may be issued to the control unit 180 and the control unit 180 may, in response to receiving the approaching signal, cause the housing lid 190 to open. When the tire 140 of the approaching vehicle reaches the optical opening 120, the housing lid 190 may be open and the detection unit 190 may detect the presence of the tire 140 at the optical opening 120, causing issuance of the detection signal to the control unit 180.

[0049] The housing lid 190 may generally be used to protect the optical scanner 150 and / or the detection unit 170 when the drive-over tire tread depth gauging system is turned off or idle. The housing lid 190 may thus generally be employed in order to protect the optical scanner from environmental pollutants such as water, dust, sand, salt, pollen, snow and gravel. During a measurement, however, the lid needs to be in the open position in order to enable visual communication between the optical scanner 150 and the tire 140 to be measured, thereby no longer offering protection of the optical scanner 150 from pollutants. As a way of maintaining a continuous protection of the optical scanner 150 from pollutants, at least one air nozzle (not shown) of the drive- over tire tread depth gauging system 100 may be configured to continuously provide an air flow barrier between the optical scanner 150 and the optical opening 120 of the housing 110 whenever the housing lid 190 is in an open position. The air nozzle is thus used both to protect the optical scanner 150 and the detection unit 170 from both environmental pollutants, and also from pollutants introduced by the tire 140 itself. The air nozzle may therefore be activated as a response to the opening of the housing lid 190. As previously described the housing lid 190 is in an open position when the housing lid 190 is not covering or only partly covering the optical opening 120 of the housing 110. It will be appreciated by a person skilled in the art that the mechanism controlling the activation of the air nozzle may be realized in a series of ways. The housing lid 190 and the air nozzle may for example both be connected to a control unit that is configured to control the activation and deactivation of the air nozzle based on the position of the housing lid.

[0050] The drive-over tire tread depth gauging system 100 comprises according to the present disclosure an optical scanner 150 arranged inside the housing 110. The optical scanner 150 is configured to measure, through the optical opening 120 of the housing 110, the tread depth of the tire 140 as the tire 140 rolls across the optical opening 120 of the housing 110. The optical scanner 150 may thus bearranged inside the housing 110 with a line of sight to the optical opening 120 of the housing 110. When a tire 140 is located by the optical opening 120, the optical scanner 150 may then capture an image of the tire 140 that further may be analyzed in order to determine the tread depth of the tire 140.

[0051] The optical scanner may generally be considered to include all the means needed in order to measure the tread depth of the tire as the tire roles across the optical opening. The optical scanner may therefore comprise the optical equipment required in order to capture an image of a tire, including at least a camera, and optionally one or more of a lens or lenses, light source, reflectors, etc. The optical scanner may optionally comprise image processing means configured to analyze said image in order to determine the tread depth from the image. Image processing means may for example be a computer, located locally or remotely. The capture of an image of a tire that may subsequently be used in order to determine the tread depth of the tire may in the context of the present disclosure be considered as a measurement of the tread depth of the tire. As will be appreciated by a person skilled in the art, optical scanners suitable for measuring the tread depth of the tire are well known in the art.

[0052] The optical scanner 150 may comprise a laser triangulation scanner 154. The laser triangulation scanner 154 comprises at least a detector, e.g. a camera, and a laser, preferably a line laser. The laser triangulation scanner 154 may generally have a standard geometry with relationship to the optical opening 120 of the housing 110, i.e. that the laser has a normal incidence with the optical opening 120 of the housing 110, and that the laser has an inclined incidence. The laser triangulation scanner 154 may alternatively have a reverse alignment, i.e. where the laser and the detector have swapped position relative to the standard geometry. The laser triangulation scanner may alternatively have a specular geometry, or a look-away geometry. A reverse geometry may be preferred in order to achieve a high resolution image, while a look away geometry may be preferred in order to obtain high resolution with reflective surfaces, e.g. during wet or icy conditions when the tires are more reflective than normal. A specular geometry may be preferred if the surface of the tire is very dark, e.g. when a measurement is performed during night or winter.

[0053] Figure 4 illustrates an embodiment of the housing 110 of the drive-over tire tread depth gauging system 100. Inside the housing 110, below the optical opening 120, a plurality of sensor units 200 are arranged. Each sensor unit 200 comprises an optical scanner 150 and a detection unit 170. The illustrated embodiment comprises twelve sensor unit 200, but the housing 110 may comprise more or less sensor units 200. Each sensor unit 200 may comprise acontrol unit 180 configured to active the optical scanner 150 based on the detection signal being received from the detection unit 170. Alternatively, the drive-over tire tread depth gauging system 100 comprises a central control unit 180 configured to receive detection signals from a plurality of detection units 170, and to active optical scanner 150 based on respective detection signals.

[0054] Figure 5 schematically illustrates the connection between the control unit 180, the detection unit 170 and the optical scanner 150. When a tire 140 is detected at the optical opening 120, the detection unit generates and transmits a detection signal to the control unit 180. The detection signal may have different forms, but may in any way be an electrical signal indicating to the control unit 180 that a tire 140 has been detected. The detection signal may be sent by wire or wirelessly to the control unit 180. Upon receipt of the detection signal, the control unit 180 activates the optical scanner 150. This may be done by sending an activation signal to the optical scanner 150. The activation of the optical scanner 150 may cause the optical scanner 150 to initiate the measurement of the tire 140. The control unit 180 may further be a recipient of measurement data from the optical scanner 150. The measurement data may involve image data and / or laser measurement data. The control unit 180 may be involved in the processing of the measurement data, and / or be forwarding the measurement data to a local or remote processing unit and / or storage unit. The processing of the measurement data may result in a tire tread depth value for the tire 140, used for determination whether the measured tire 140 has a tread depth above a requirement threshold.

[0055] A particular aspect of the present disclosure provides a method 300 for gauging the tire tread depth of a moving vehicle, illustrated in figure 6. The method 300 comprising the steps of a) providing 302 a drive-over tire tread depth gauging system 100 according to any of the embodiments described herein, such that the drive-over tire tread depth gauging system 100 is embedded in a road 130 or road segment such that the top opening of the housing 110 of the drive-over tire tread depth gauging system 100 aligns with the surface of the road 130 or road segment, b) detecting 304 presence of a tire 140 at the optical opening 120 by means of the detection unit 170, c) based, at least in part, on the detection of a tire 140 at the optical opening 120, issuing 306 a detection signal to the control unit 180, and d) activating 308, based on the detection signal, the optical scanner 150 of the drive-over tire tread depth gauging system 100 to measure the tire tread depth of the tire 140 detected at the optical opening 120.

[0056] The method 300 may be performed according to the configuration of the drive- over tire tread depth gauging system 100 described in any of the embodiments above.

[0057] In the drawings and specification, there have been disclosed preferred embodiments and examples of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being set forth in the following claims.

Claims

Claims1. A drive-over tire tread depth gauging system (100), the system (100) comprising: a housing (110) comprising an optical opening (120), where the housing (110) is configured to be embedded in a road (130) such that a tire (140) of a vehicle can roll across the optical opening (120) of the housing (110), an optical scanner (150) arranged inside the housing (110), where the optical scanner (150) is configured to measure, through the optical opening (120) of the housing (110), the tread depth of the tire (140) as the tire (140) rolls across the optical opening (120) of the housing (110), a control unit (180) configured to activate the optical scanner (150), a detection unit (170) arranged inside the housing, where the detection unit (170) is configured to detect presence of a tire (140) at the optical opening (120) and send a detection signal to the control unit (180), wherein the control unit (180) is configured to activate the optical scanner (150) upon reception of the detection signal from the detection unit (170).

2. The drive-over tire tread depth gauging system (100) according to claim 1, wherein the detection unit (170) is arranged at a distance from the optical opening (120), with a line of sight to the optical opening.

3. The drive-over tire tread depth gauging system (100) according to claim 1 or 2, wherein the detection unit (170) is a radar unit.

4. The drive-over tire tread depth gauging system (100) according to claim 3, wherein the radar unit comprises a radar lens configured to focus the radar measurement.

5. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein the optical scanner (150), the control unit (180) and the detection unit (170) are arranged in a sensor unit (200), and wherein the housing comprises a plurality of such sensor units (200).

6. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein the optical opening (120) extends from a first endto a second end along a moving direction (X) of a tire of a moving vehicle over the drive-over tire tread depth gauging system (100), the second end being downstream in the moving direction compared to the first end, and wherein the detection unit (170) is configured to detect presence of a tire (140) adjacent to the first end of the optical opening (120).

7. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein measurement of the tire (140) at the optical opening (120) by the optical scanner (150) is configured to be triggered by the detection signal issued by the detection unit (170).

8. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein the optical scanner (150) comprises the control unit (180).

9. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein the optical scanner (150) comprises one or more out of the group of at least one camera, at least one laser triangulation scanner (160) or at least one LED flash unit.

10. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, wherein the detection unit (170) is configured to detect presence of a tire (140) at a distance of between 10-40 cm, preferably between 15-35 cm, from the detection unit.

11. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, further comprising an air-cleaning device configured to provide an air flow inside the housing for cleaning one or more of the optical scanner (150) and the detection unit (170), wherein the control unit (180) is further configured to activate the air-cleaning device based on the detection signal.

12. The drive-over tire tread depth gauging system (100) according to any one of the preceding claims, further comprising a housing lid (190) configured to, in a closed position, cover the optical opening (120) and in an open position enable visual communication between the optical scanner (150) and a tire (140) at the optical opening (120), wherein the detection unit (170) is configured to detect an approaching vehicle by detecting vibrations in the housing (110) and / or thehousing lid (190), and, when detecting vibrations indicative of an approaching vehicle, send an approaching signal to the control unit (180) causing the housing lid (190) to be moved to the open position.

13. Use of a drive-over tire tread depth gauging system (100) according to any one of the claims 1 - 12, for measuring the tread depth of a tire (140) of a moving vehicle.

14. A method (300) for gauging the tire tread depth of a tire (140) of a moving vehicle, the method comprising the steps of: providing (302) a drive-over tire tread depth gauging system (100) according to any one of the claims 1 - 12, wherein the drive-over tire tread depth gauging system (100) is embedded in a road (130) or road segment such that the top opening of the housing (110) of the drive-over tire tread depth gauging system (100) aligns with the surface of the road (130) or road segment, detecting (304) presence of a tire (140) at the optical opening (120) by means of the detection unit (170), based, at least in part, on the detection of a tire (140) at the optical opening (120), issuing (306) a detection signal to the control unit (180), and activating (308), based on the detection signal, the optical scanner (150) of the drive-over tire tread depth gauging system (100) to measure the tire tread depth of the tire (140) detected at the optical opening.

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