SE2050647A1

SE2050647A1 - Method, control arrangement and reference object for calibration of sensors

Info

Publication number: SE2050647A1
Application number: SE2050647A
Authority: SE
Inventors: Daniel Tenselius; Erik Johansson; Fredrich Claezon; Mattias Johansson; Mikael Salmén
Original assignee: Scania Cv Ab
Priority date: 2020-06-04
Filing date: 2020-06-04
Publication date: 2021-04-26

Abstract

Control arrangement (120), vehicle external controller (170) and methods (400, 500) therein, for calibration of a vehicle sensor (110) of a vehicle (101) in cooperation with a calibration structure (150). The control arrangement (120) is configured to detect at least one calibration target (160a, 160b, 160c, 160d) on the calibration structure (150) via the vehicle sensor (110); determine position of the calibration target (160a, 160b, 160c, 160d), based on the detection by the vehicle sensor (110); obtain calibration data from the calibration structure (150), relating to position of the calibration target (160a, 160b, 160c, 160d) on the calibration structure (150) and position of a vehicle reference point (140) on the vehicle (101); and calibrate the vehicle sensor (110), based on the determined position of the calibration target (160a, 160b, 160c, 160d) and the obtained calibration data.

Description

METHOD, CONTROL ARRANGEMENT AND REFERENCE OBJECT FOR CALIBRATIONOF SENSORS TECHNICAL FIELD This document discloses a method, a control arrangement and a reference object. I\/|oreparticularly, a method, a control arrangement and a reference object are disclosed for cali-bration of a vehicle sensor based on measurements of electromagnetic radiation.

BACKGROUND A vehicle, in particular an autonomous vehicle, comprises a large number of sensors of dif-ferent kind. Vehicle sensors are often calibrated in the production line using a reference pointor similar to ensure that the sensors are aligned as expected.

Autonomous vehicles cannot rely on human interaction, why it is important to ensure that the sensor information of the environment is correct.

Calibration of vehicle sensors are normally made in a calibration room in the production fa-cility of the vehicle. Conventional calibration rooms require a relatively large area/ space.The calibration room has to be made with very precise measurements, levelled floor etc., toenable correct calibration. Consequently, it is expensive to construct and maintain conven- tional calibration rooms.

When it comes to post-production calibration of sensors, rational sensor calibration becomesnot only expensive and difficult but may even be impossible. To get a good calibration it isimperative to have a flat and levelled surface when doing the calibration. This is contradictoryto workshop floors as they are typically designed to allow spill fluids to flow into a sink hole.When doing a calibration on an uneven surface, such as outdoors, the calibration quality isoften reduced.

Sensors on an autonomous vehicle operating in for example a mine, construction site, de-forestation site or similar rough environment is exposed to an enhanced risk of being tilted.lt may be impossible (or at least very expensive) to build/ have dedicated rooms with auto-mated processes for calibration of the vehicle sensors, while the sensors of working vehicles in rough environments are more likely than other vehicles to require occasional calibration.

The service calibration methods for workshops puts a lot of demand on the personnel toposition the measurement equipment at the exact same position relative to the vehicle, and the precision of the calibration is often of less quality than it is from the factory calibrationprocess.

Document US20190056479A1 describes a method for calibrating a radar sensor in a vehicle.A 3D coordinate of the radar sensor is detected, and a correction value is calculated and iscommunicated with the vehicle by a vehicle external entity.

The document only concerns radar adjustment, not other sensor types. Secondly, the systemdescribed in the document is a kind of calibration room with all comprised entities positionedwith precision on a flat surface, enabling the vehicle and the vehicle external sensors toshare a common coordinate system. The vehicle has to be aligned with a reference inspec-tion position and the vehicle wheels positioned on driving rollers. The provided solution ap-pears not presenting a solution to the problem of not requiring a dedicated calibration room.

Document US20190113608A1 describes a calibration method where image data of a vehiclesensor is transformed into global coordinate data. Fractal dimensions values of the globalcoordinate data are estimated, and calibrated parameters are determined based on the frac- tal dimensions values.

Although not mentioned explicitly in the document, it is a prerequisite for the method to func-tion that the vehicle is positioned in a calibration room, or under similar controlled conditions.

Document US20180141567A1 concerns a calibration station and a vehicle with onboardsensors to be calibrated. A vehicle situated in a vicinity of the calibration station may receivereference data which may be used for calibration of sensors of the vehicle.

However, the document does not explain how navigation sensors of the vehicle could becalibrated. The examples of sensors/ sensor values that are calibrated concerns temperatureand air humidity. lt would be desired to calibrate vehicle sensors automatically at a regular basis also on aworking site or during driving conditions which are not perfect for conventional calibration of vehicle sensors.

SUMMARY lt is therefore an object of this invention to solve at least some of the above problems and improve traffic security, in particular when driving an autonomous vehicle, by sensor calibra- tion.

According to a first aspect of the invention, this objective is achieved by a control arrange-ment for calibration of a vehicle sensor of a vehicle, in cooperation with a calibration struc-ture. The control arrangement is configured to detect at least one calibration target on thecalibration structure via the vehicle sensor. Further, the control arrangement is configured todetermine position of the calibration target, based on the detection by the vehicle sensor. lnaddition, the control arrangement is also configured to obtain calibration data from the cali-bration structure, relating to position of the calibration target on the calibration structure andposition of a vehicle reference point on the vehicle. The control arrangement is also config-ured to calibrate the vehicle sensor, based on the determined position of the calibration targetand the obtained calibration data.

According to a second aspect of the invention, this objective is achieved by a vehicle externalcontroller for enabling calibration of a vehicle sensor of a vehicle. The vehicle external con-troller is configured to determine position of a vehicle reference point on the vehicle. Thevehicle external controller is also configured to provide calibration data relating to position ofthe calibration target on the calibration structure and position of the vehicle reference pointon the vehicle, thereby enabling calibration of the sensor of the vehicle.

According to a third aspect of the invention, this objective is achieved by a method in a controlarrangement of a vehicle for calibration of a vehicle sensor in cooperation with a calibrationstructure. The method comprises detecting at least one calibration target on the calibrationstructure via the vehicle sensor. The method also comprises determining position of the cal-ibration target, based on the detection by the vehicle sensor. Furthermore, the method com-prises obtaining calibration data from the calibration structure, relating to position of the cal-ibration target on the calibration structure and position of a vehicle reference point on thevehicle, via wireless signalling. The method additionally comprises calibrating the vehiclesensor, based on the determined position of the calibration target and the obtained calibra-tion data.

According to a fourth aspect of the invention, this objective is achieved by a method of avehicle external controller for enabling calibration of a vehicle sensor of a vehicle. Themethod comprises determining position of a vehicle reference point. Also, the method furthercomprises providing calibration data to the vehicle, relating to position of the calibration targeton the calibration structure and position of a vehicle reference point on the vehicle, thereby enabling calibration of the sensor of the vehicle, via wireless signalling.

Thanks to the described aspects, the functionality of various sensors in a vehicle may bechecked regularly while passing or stopping at places where the calibration structure com-prising the calibration targets is situated. The vehicle reference point on the vehicle enablea conversion between a coordinate system of the vehicle and a coordinate system of thecalibration structure is enabled. By wireless communication of calibration data, received in-formation concerning position and properties of the calibration targets with the correspondinginformation determined by the sensors, a misalignment may be detected. Thus, a calibrationof the misaligned sensor may be performed. This process may be repeated until no misa-lignment (exceeding a predetermined threshold limit) is detected of any sensor in/ on thevehicle. Thereby, traffic safety is enhanced. Also, it is avoided that the vehicle has to interruptthe current transportation and stop, waiting for a service operator to come and check/ cali-brate/ exchange sensors on the vehicle. Hereby, time and money are saved.

Other advantages and additional novel features will become apparent from the subsequentdetailed description.

FIGURES Embodiments of the invention will now be described in further detail with reference to theaccompanying figures, in which: Figure 1 illustrates an example of a vehicle equipped with sensors and a calibrationstructure according to embodiments of the invention.

Figure 2 illustrates a vehicle interior of a vehicle equipped with sensors and a controlarrangement and a calibration structure according to embodiments of the in-vention.

Figure 3A illustrates an example of a mobile calibration structure from the front.

Figure 3B illustrates an example of a mobile calibration structure from the side.

Figure 4 is a flow chart illustrating an embodiment of a method in a control arrangementof a vehicle.

Figure 5 is a flow chart illustrating an embodiment of a method of a vehicle externalcontroller.

Figure 6 is an illustration depicting a system according to an embodiment.

DETAILED DESCRIPTION Embodiments of the invention described herein are defined as a control arrangement, a ve-hicle external controller and methods therein, which may be put into practice in the embodi-ments described below. These embodiments may, however, be exemplified and realised inmany different forms and are not to be limited to the examples set forth herein; rather, theseillustrative examples of embodiments are provided so that this disclosure will be thoroughand complete.

Still other objects and features may become apparent from the following detailed description,considered in conjunction with the accompanying drawings. lt is to be understood, however,that the drawings are designed solely for purposes of illustration and not as a definition ofthe limits of the herein disclosed embodiments, for which reference is to be made to theappended claims. Further, the drawings are not necessarily drawn to scale and, unless oth-en/vise indicated, they are merely intended to conceptually illustrate the structures and pro-cedures described herein.

Figure 1 illustrates a system 100 for calibration of a vehicle sensor 110 in a vehicle 101. Thevehicle 101 is standing or driving within sensor detection distance from a calibration structure150.

The vehicle 101 may comprise a truck, a bus, a car, a motorcycle, or similar means of con-veyance. The vehicle 101 may typically be autonomous/ driverless. However, the vehicle101 may also, or alternatively be conducted by a human driver.

The vehicle 101 comprises at least one vehicle sensor 110 configured for detecting trafficrelated objects such as e.g. the calibration structure 150 and/ or a calibration target 160thereon, in the relative vicinity of the vehicle 101.

The sensor 110 may comprise any arbitrary kind of sensor such as e.g. a camera, a stereocamera, an infrared camera, a video camera, a radar, a Light Detection and Ranging (Ll-DAR), an ultrasound device, a time-of-flight camera, or similar device, in different embodi-ments. The sensor 110 may capture, e.g., images, video sequences, views from multiplecameras, or multi-dimensional data from a scanner, data of a LIDAR, radar, etc., or a com-bination thereof. Sensors 110 may also in some embodiments be mounted on the vehicle101 in sensor modules, comprising a plurality of sensors 110, as schematically illustrated inFigure 2 and discussed in the corresponding description text segment.

The calibration structure 150 may be a mobile unit in some embodiments, which may be moved and placed at any arbitrary position where vehicles 101 are able to pass. ln otherembodiments, the calibration structure 150 may be stationery and form part of for examplea garage portal, a loading bay, a fuel/ energy loading station, a roadside building, a trafficsign/ light, a pole, etc.

The calibration structure 150 may have the shape of a portal in some embodiments, provid-ing enhanced stability to the structure and ensuring consistent relative positions of calibrationtargets 160 on the calibration structure 150. However, the calibration structure 150 may inother embodiments have the shape of e.g. one, two or several separate sub-structures situ-ated at one or both roadsides and/ or above the road.

When the vehicle 101 is approaching or situated within sensor recognition distance from thecalibration structure 150, the vehicle sensor 110 may detect the calibration target/s 160 onthe calibration structure 150. A control arrangement 120 of the vehicle 101 may determineposition of the calibration target 160, based on the detection by the vehicle sensor 110.

As the vehicle 101 is approaching or is detected as situated within sensor recognition dis-tance from the calibration structure 150, position of a vehicle reference point 140 on thevehicle 101 may be determined by a vehicle external controller 170 of the calibration struc-ture 150, based on a sensor detection made by a sensor 180 of the calibration structure 150.The sensor 180 is calibrated in relation to itself and the portal structure 150.

The position of the vehicle reference point 140 on the vehicle 101, as perceived by the portalsensor 180 may be communicated to the control arrangement 120 of the vehicle 101 viawireless communication between a wireless transceiver 190 of the calibration structure 150and a wireless transceiver 130 of the vehicle 101.

Based on the obtained calibration data from the calibration structure 150, the control ar-rangement 120 of the vehicle 101 may calibrate the vehicle sensor 110, based on the deter-mined position of the calibration target 160 and the obtained calibration data. lt hereby becomes possible to correlate a first coordinate system relating to the calibrationstructure 150 with a second coordinate system relating to the vehicle 101, based on thecommunicated calibration data. The vehicle reference point 140 may be the origin in thesensor fusion coordinate system. The detection of the vehicle reference point 140 may for example be done using a neural network.

The positional relation between the vehicle reference point 140 and the vehicle sensor 110is predetermined and stored in a memory or database, where it may be obtained by thecontrol arrangement 120 of the vehicle 101 . Correspondingly, the positional relation betweenthe calibration target/s 160 on the calibration structure 150 and the portal sensor 180 is pre-determined and stored in a memory or database, where it may be obtained by the controlarrangement 170 of the calibration structure 150.

Thereby, by determining the position of the vehicle reference point 140 by the portal sensor180 in relation to the portal sensor 180 and communicate calibration data comprising thisinformation (and position of the calibration target/s 160) to the control arrangement 120 ofthe vehicle 101, it becomes possible to convert positions of the calibration target/s 160 and/or the vehicle sensor 110 into a common coordinate system. lt then also becomes possibleto compare the obtained position of the calibration target/s 160 with the estimated positionof the calibration target/s 160 as perceived by the vehicle sensor 110. ln case a differenceis detected between these positions, the vehicle sensor 110 may be calibrated, based onthis detected difference.

Alternatively, the conversion of the respective positions may alternatively be made by thecontrol arrangement 170 of the calibration structure 150, or by any other vehicle externallogic, by providing the calibration data from the vehicle 101.

The calibration process can be made fully automatic, without human supervision. Further,the calibration structure 150 may be situated in the normal flow of the vehicle operation en-abling continuous and periodical check of sensor misalignment of sensors 110 on the vehicle101. Thereby, the need for complex and expensive calibration rooms is omitted. lt becomespossible to calibrate vehicle sensors 110 on an uneven underneath such as often is the caseoutdoors or in a workshop. The time it would have taken to drive and queue for a dedicatedcalibration room service is also saved, leading to more efficient usage/ runtime of the vehicle101.

The calibration (or at least a calibration check, each passing of the calibration structure 150may not result in a calibration if the sensor values are acceptable) could be made frequently,for example when the vehicle 101 is passing or stopping close to the calibration structure150, thereby eliminating or at least radically reducing the risk of accidents or vehicle emer-gency stop due to sensor calibration errors.

The wireless communication between the wireless transceiver 130 of the vehicle 101 andthe wireless transceiver 190 of the calibration structure 150 may comprise, or at least beinspired by wireless communication technology such as Wi-Fi, Wireless Local Area Network(WLAN), Ultra Mobile Broadband (UMB), Bluetooth (BT), Radio-Frequency Identification(RFID), optical communication such as Infrared Data Association (lrDA) or infrared transmis-sion to name but a few possible examples of wireless communications in some embodi- mentS. ln some embodiments, the wireless communication may be performed via vehicle-to-vehicle(V2V) communication, e.g. based on Dedicated Short-Range Communications (DSRC) de-vices. DSFIC works in 5.9 GHz band with bandwidth of 75 MHz and approximate range of1000 m.

The wireless communication may be made according to any IEEE standard for wireless ve-hicular communication like e.g. a special mode of operation of IEEE 802.11 for vehicularnetworks called Wireless Access in Vehicular Environments (WAVE). IEEE 802.11p is anextension to 802.11 Wireless LAN medium access layer (MAC) and physical layer (PHY)specification.

The communication may alternatively be made over a wireless interface comprising, or atleast being inspired by radio access technologies such as e.g. third Generation PartnershipProject (3GPP) 5G/ 4G, 3GPP Long Term Evolution (LTE), LTE-Advanced, Groupe SpecialMobile (GSM), or similar, just to mention some few options, via a wireless communication network.

However, in some embodiments, the calibration structure 150 may be passive, i.e. not com-prising any wireless transceiver 190, but wireless communication with the vehicle 101 maycomprise encoding in the calibration target/s 160, enabling identification of the respectivecalibration target/s 160, for example. The calibration structure 150 may then be utilised forcontrolling relative calibration of the vehicle sensor 110.

The control arrangement 120 of the vehicle 101 may comprise e.g. one or several ElectronicControl Units (ECUs), typically a plurality of interacting ECUs. The control arrangement 120may comprise a digital computer that controls one or more electrical systems, or electricalsub systems, of the vehicle 101, based on e.g. information read from the sensor 110. ECUis a generic term that often is used in automotive electronics, for any embedded system thatcontrols one or more of the electrical system or sub systems in the vehicle 101. The control arrangement 120 may be particularly designated to implement recognition pattern recogni-tion of the calibration target/s 160 based on sensor input.

The calibration target/s 160 may in some embodiments comprise a photogrammetry codedmarker, i.e., a distinctive visual pattern designed to be automatically detected by the sensor110. Thereby encoded information may be provided in the calibration target/s 160 which maybe decoded by the control arrangement 120 via sensor detection by the sensor 110.

The design of the calibration target/s 160 may be for example square, circular, based onconcentric circles etc. in black and white. By providing white dots in a black annulus, a robusttarget detection and decoding is provided, in some embodiments. ln other embodiments, thecalibration target/s 160 may comprise one or several colours.

The information encoded in each of the calibration target/s 160 may for example comprisean identity reference of the calibration target/s 160, e.g. in case the calibration structure 150comprises a plurality of calibration target/s 160. The information encoded in the calibrationtarget/s 160 may also, or in addition comprise an identity reference of the calibration structure150, information concerning number of calibration target/s 160 comprised on the calibrationstructure 150, type and/ or sensitivity of the portal sensor 180 and/ or other similar infor- mation.

Figure 2 illustrates a system 100 for calibration of a vehicle sensor 110 in a vehicle 101,which may be identical with or similar to the one illustrated in Figure 1, as regarded from aview inside the vehicle 101.

The calibration structure 150 may comprise a plurality of calibration targets 160a, 160b,160c, 160d situated at different predetermined positions on the calibration structure 150,which may be detected by the vehicle sensor 110.

To ensure a robust calibration, several calibration targets 160a, 160b, 160c, 160d may bedetected by the vehicle sensor 110, thereby achieving a more accurate result, according to some embodiments.

The vehicle sensor 110 may be comprised in a sensor module 200, which may comprise aplurality of sensors 110, 210. ln some embodiments, the other sensor 210 may be calibratedbased on the target measurement made by the vehicle sensor 110.

The vehicle sensor 110 used for recognising the calibration targets 160a, 160b, 160c, 160dmay be a lidar in some embodiments. Lidar is a sensor modality that is extremely accuratefor detecting distances to objects such as the calibration targets 160a, 160b, 160c, 160d.The other sensor/s 210 in the sensor module 200 may be for example cameras or radar.

The position/-s of the sensor 110 and/ or the sensor module 200 in relation to the position ofthe vehicle reference point 140 on the vehicle 101 may be known by the control arrangement120 of the vehicle 101. These position/-s may be stored in a local database for example. Byobtaining calibration data in form of the position of the vehicle reference point 140, as per-ceived by the sensor 180 of the calibration structure 150 and determined by the vehicle ex- ternal controller 170, a conversion into a common coordinate system may be made.

By obtaining the position of the vehicle reference point 140 in the coordinate system of thecalibration structure 150, the position of the sensor 110 and/ or the sensor module 200 maybe determined in the coordinate system of the calibration structure 150 in some embodi- mentS.

Thereafter, a sensor calibration may be made by comparing the positions of the calibrationtargets 160a, 160b, 160c, 160d in the coordinate system of the calibration structure 150 asobtained from the calibration structure 150, the calculated position of the vehicle sensor 110based on the obtained position of the vehicle reference point 140 in the coordinate systemof the calibration structure 150; and the positions of the calibration targets 160a, 160b, 160c,160d on the calibration structure 150 as perceived by the sensor 1 10, in case the calculationsare made by the control arrangement 120 of the vehicle 101. ln other embodiments, the calculations may be made entirely or partly external to the vehicle101, for example by the vehicle external controller 170 of the calibration structure 150, orany vehicle external controller. Hereby, computational efforts of the vehicle control arrange-ment 120 may be saved.

Via the wireless communication, information concerning absolute and/or relative position,size, shape, colour/s, etc., of the calibration targets 160a, 160b, 160c, 160d on the calibrationstructure 150 may be transferred to the control arrangement 120 of the vehicle 101. Thisinformation may then act as “ground truth” and be used for making comparisons with thesensor data.

By comparing the detection data from the sensor 110 with the reported position and size by 11 the calibration targets 160a, 160b, 160c, 160d, sensor misalignment can be detected andadjusted electronically and/ or mechanically to compensate for the current error betweendetections and the vehicle-to-infrastructure data, in case the error exceeds a predeterminedthreshold limit, such as e.g. 1%.

To ensure a robust calibration, several calibration targets 160a, 160b, 160c, 160d that canbe detected at the same time may be used to achieve a more accurate result, according to some embodiments.

Figures 3A and 3B illustrate a mobile calibration structure 150 as regarded from a front viewin Figure 3A and a sideview in Figure 3B.

The mobile calibration structure 150 may comprise a mobility facilitating arrangement 310,configured to enable mobility of the calibration structure 150. The mobility facilitating arrange-ment 310 may comprise a set of wheels for upholding the mobile calibration structure 150 atleast during transportation. ln some embodiments, the mobility facilitating arrangement 310 may comprise an engine formoving the mobile calibration structure 150 and possibly also autonomous logic to move themobile calibration structure 150 into different positions in order to calibrate vehicle sensors110 of different vehicles 100, for example depending on traffic density or other requirements.Thereby, the mobile calibration structure 150 may be situated for example at a ferry terminalat a time period when a ferry is arriving while otherwise being positioned at a trafficked road, for example. ln some embodiments, the sensor 180 of the mobile calibration structure 150 may detectnumber of passing vehicles and when the number of passing vehicles is lower than a thresh-old level, the mobile calibration structure 150 may relocate to another geographical positionwhere a higher traffic intensity may be expected.

Figure 4 illustrates an example of a method 400 according to an embodiment. The flow chartin Figure 4 shows the method 400 in a control arrangement 120 of a vehicle 101 for calibra-tion of a vehicle sensor 110 in cooperation with a calibration structure 150. The vehicle sen-sor 110 is based on measurements of electromagnetic radiation, e.g. camera, radar, lidar,etc.

The sensor calibration may be made based on detection of at least one calibration target 12 160a, 160b, 160c, 160d on the calibration structure 150. The calibration structure 150 maybe a mobile and/ or autonomous entity, or a static structure which may form part of anotherroad-side structure such as e.g. a traffic sign, a bus stop, a loading dock, a driveway, agarage entrance, a tunnel entrance, an edifice structure, etc. ln order to be able to correctly calibrate the vehicle sensor 110, the method 400 may com-prise a number of steps 401-404. However, some of these steps 401 -404 may be performedsolely in some alternative embodiments. Further, the described steps 401-404 may be per-formed in a somewhat different chronological order than the numbering suggests. Themethod 400 may comprise the subsequent steps: Step 401 comprises detecting at least one calibration target 160a, 160b, 160c, 160d situatedon the calibration structure 150, via the vehicle sensor 110.

The vehicle sensor 110 may comprise a |idar in some embodiments. Lidar is a sensor mo-dality which is in particular dedicated for precise distance estimation.

Step 402 comprises determining position of the calibration target 160a, 160b, 160c, 160d,based on the detection 401 by the vehicle sensor 110.

The position of the calibration target 160a, 160b, 160c, 160d may be determined in a coor-dinate system of the vehicle 101 in some embodiments, i.e. position in relation to the vehiclesensor 110. ln other embodiments, the position of the calibration target 160a, 160b, 160c, 160d may bedetermined in a common coordinate system between the vehicle 101 and the calibrationstructure 150, based on the obtained position of the vehicle reference point 140 on the vehi-cle 101 . The common coordinate system may be a coordinate system of the calibration struc-ture 150. ln yet some alternative embodiments, the determined position of the calibration target 160a,160b, 160c, 160d may be transmitted to a vehicle external controller 170. The vehicle exter-nal controller 170 may be associated with the calibration structure 150 but may alternativelybe another vehicle external entity.

The vehicle external controller 170 may then calculate position of the calibration target 160a,160b, 160c, 160d as determined by the vehicle sensor 110, in a common coordinate system. 13 The vehicle external controller 170 may in yet some alternative embodiments compare theposition of the calibration target 160a, 160b, 160c, 160d as detected 401 by the vehicle sen-sor 110 with the known position of the calibration target 160a, 160b, 160c, 160d in the com-mon coordinate system. Hereby, a deviation may be detected, which may trigger a calibrationof the vehicle sensor 110.

Step 403 comprises obtaining calibration data from the calibration structure 150, relating toposition of the calibration target 160a, 160b, 160c, 160d on the calibration structure 150 andposition of a vehicle reference point 140 on the vehicle 101, via wireless signalling.

The positions of the calibration target 160a, 160b, 160c, 160d and the position of the vehiclereference point 140 may be determined in the same coordinate system which may be com-mon between the vehicle 101 and the calibration structure 150. The common coordinatesystem may be a coordinate system of the calibration structure 150.

The position of the vehicle sensor 110 in relation to the vehicle reference point 140 may bepredetermined and stored in a memory or database. The control arrangement 120 of thevehicle 101 may obtain the position from the memory/ database and determine the positionof the vehicle sensor 110 in the common coordinate system. Also, the position of the calibra-tion target 160a, 160b, 160c, 160d in the common coordinate system, as determined by thevehicle sensor 110 may be calculated. ln some embodiments wherein the vehicle external controller 170 has calculated position ofthe calibration target 160a, 160b, 160c, 160d as determined by the vehicle sensor 110, inthe common coordinate system, the obtained calibration data may comprise a calculateddeviation between the position of the calibration target 160a, 160b, 160c, 160d as deter-mined by the vehicle sensor 110 and the known position of the calibration target 160a, 160b,160c, 160d; and/ or the position of the calibration target 160a, 160b, 160c, 160d as deter-mined by the vehicle sensor 110 and the known position of the calibration target 160a, 160b,160c, 160d in the common coordinate system. ln some embodiments, the obtained calibration data from the calibration structure 150 maycomprise an identity reference and/ or configuration of the calibration structure 150. Differentembodiments of the calibration structure 150 may have different capacities and/ or granular-ity in the positioning and calibration. 14 Step 404 comprises calibrating the vehicle sensor 110, based on the determined position ofthe calibration target 160a, 160b, 160c, 160d and the obtained calibration data.

The calibration of the sensor, or a calibration check at least, may be performed each timethe vehicle 101 is passing the calibration structure 150, without requiring the vehicle 101 tostop. With several calibration structures 150 positioned along selected positions along a ve-hicle route, sensor calibration (check) may be made frequently and automatically, which isan in particular suitable solution for autonomous vehicles but may also be applied for vehicleshaving a driver. Hereby, accidents and/ or vehicle emergency-stops due to uncalibrated sen-sors could be eliminated, or at least radically reduced.

By using a common coordinator system for determining the position of the calibration target160a, 160b, 160c, 160d on the calibration structure 150 as predetermined, and the positionof the calibration target 160a, 160b, 160c, 160d as perceived by the vehicle sensor 110, theprecondition of sensor calibration in conventional calibration rooms becomes superfluous. ltis not required that the vehicle sensor 1 10/ the vehicle 101 is positioned in a predeterminedposition, that the underneath is even, and/ or that the vehicle 101 is parked while making thecalibration. lt thereby becomes possible to perform the calibration procedure at arbitrary locations whereit otherwise would have been impossible or very expensive to build a traditional calibrationroom, such as on a mining excavation site, a deforestation site, an extra terresial explorationcentre, etc. ln some embodiments, the position of the obtained 403 position of the calibration target 160a,160b, 160c, 160d on the calibration structure 150 and the determined 402 position of thecalibration target 160a, 160b, 160c, 160d, as detected 401 by the vehicle sensor 110 maybe determined in a common coordinate system and compared with each other. A deviationin the positions of the calibration target 160a, 160b, 160c, 160d (exceeding a threshold limit,e.g. 1%) may trigger a calibration of the vehicle sensor 110 for eliminating the deviation. ln some embodiments wherein the vehicle sensor 110 is situated in a sensor module 200comprising a plurality of sensors 110, 210, the calibration may comprise calibration of an-other sensor 210 of the sensor module 200, based on the target measurement made by thevehicle sensor 110.

By keeping the vehicle sensors 110, 210 in a sensor module 200, with a predetermined and known configuration and position, a first positioning may be made with the most accuratesensor/ sensor type of the sensor module 200 and based on the result there upon, calibrationmay be made of the other sensors 210, thereby facilitating and improving the calibration.

Figure 5 illustrates an example of a method 500 according to an embodiment. The flow chartin Figure 5 shows the method 500 in a vehicle external controller 170 for enabling calibration of a vehicle sensor 110 of a vehicle 101.

The sensor calibration may be made based on sensor detections made by a vehicle sensor110 on the vehicle 101, of at least one calibration target 160a, 160b, 160c, 160d on thecalibration structure 150. The calibration structure 150 may be a mobile and/ or autonomousentity, or a static structure which may form part of another road-side structure such as e.g. atraffic sign, a bus stop, a loading dock, a driveway, a gar-age entrance, a tunnel entrance,an edifice structure, etc. ln order to correctly enable calibration of the vehicle sensor 110, the method 500 may com-prise a number of steps 501-502. However, some of these steps 501 -502 may be per-formedsolely in some alternative embodiments. Further, the described steps 501-502 may be per-formed in a somewhat different chronological order than the numbering suggests. Themethod 500 may comprise the subsequent steps: Step 501 comprises determining position of a vehicle reference point 140.

The position of the vehicle reference point 140 may be determined based on a sensor de-tection made by a sensor 180 on or associated with the calibration structure 150. ln some embodiments, the method 500 may comprise obtaining data related to the deter-mined position of the calibration target 160a, 160b, 160c, 160d, as determined by the vehiclesensor 110.

A calculation may then be made in some embodiments based on the obtained position ofthe calibration target 160a, 160b, 160c, 160d, as determined by the vehicle sensor 110,transferring this position into a common coordination system. ln yet some embodiments, the obtained position of the calibration target 160a, 160b, 160c,160d, as determined by the vehicle sensor 110 and the known positions of the calibrationtarget 160a, 160b, 160c, 160d may be compared with each other and a deviation between 16 the respective positions may be detected.

Step 502 comprises providing calibration data to the vehicle 101, relating to position of thecalibration target 160a, 160b, 160c, 160d on the calibration structure 150 and position of avehicle reference point 140 on the vehicle 101, thereby enabling calibration of the sensor110 of the vehicle 101, via wireless signalling.

The calibration data may comprise the position of the calibration target 160a, 160b, 160c,160d on the calibration structure 150 and position of a vehicle reference point 140 on thevehicle 101, in the coordinate system of the calibration structure 150 in some embodiments.

On some embodiments, the calibration data may comprise an identity reference and config-uration of the calibration structure 150. ln yet some embodiments wherein the position of the calibration target 160a, 160b, 160c,160d, as determined by the vehicle sensor 110 has been obtained from the vehicle 101,position thereof in the common coordination system has been calculated, the calibration datamay comprise this position. ln yet some embodiments wherein a comparison has been madebetween the vehicle sensor determined position of the calibration target 160a, 160b, 160c,160d and the known position of the calibration target 160a, 160b, 160c, 160d, the result ofthe comparison may be provided to the vehicle 101.

By making calculations on a vehicle external controller 170 outside the vehicle 101, calcula-tion ability onboard the vehicle 101 is saved for traffic critical navigation, leading to a possibly reduced risk of traffic accidents.

Figure 6 illustrates an embodiment of a system 100 for calibration of a vehicle sensor 110,in a vehicle 101.

The system 100 comprises a vehicle 101, which in turn comprises a control arrangement120, at least one vehicle sensor 110, a wireless transceiver 130 and a vehicle referencepoint 140.

The system 100 also comprises a calibration structure 150 for enabling calibration of thevehicle sensor 110 of the vehicle 101. The calibration structure 150 comprises a vehicleexternal controller 170, awireless transceiver 190, at least one calibration target 160a, 160b, 17 160c, 160d and at least one sensor 180a, 180b, 180c configured to detect a vehicle refer-ence point 140 on the vehicle 101.

The control arrangement 120 of the vehicle 101 is configured to calibrate a vehicle sensor110 of the vehicle 101 in cooperation with the calibration structure 150 by performing themethod 400 according to at least some of the described method steps 401-404. The controlarrangement 120 of the vehicle 101 is configured to detect at least one calibration target160a, 160b, 160c, 160d on the calibration structure 150 via the vehicle sensor 110. Also, thecontrol arrangement 120 is configured to determine position of the calibration target 160a,160b, 160c, 160d, based on the detection by the vehicle sensor 110. The control arrange-ment 120 is also configured to obtain calibration data from the calibration structure 150, re-lating to position of the calibration target 160a, 160b, 160c, 160d on the calibration structure150 and position of a vehicle reference point 140 on the vehicle 101. ln addition, the controlarrangement 120 is also configured to calibrate the vehicle sensor 110, based on the deter-mined position of the calibration target 160a, 160b, 160c, 160d and the obtained calibrationdata.

The control arrangement 120 may in some embodiments be further configured to determinethe obtained position of the calibration target 160a, 160b, 160c, 160d and the determinedposition of the calibration target 160a, 160b, 160c, 160d in a common coordinate system,based on the obtained position of the vehicle reference point 140 on the vehicle 101. Further,the control arrangement 120 may also in some embodiments be configured to compare theposition of the obtained position of the calibration target 160a, 160b, 160c, 160d on the cal-ibration structure 150 with the determined position of the calibration target 160a, 160b, 160c,160d. The control arrangement 120 may also be configured to calibrate the vehicle sensor110, based on the made comparison. ln some embodiments, the control arrangement 120 may be configured to provide the deter-mined position of the calibration target 160a, 160b, 160c, 160d to a vehicle external controller170. Furthermore, the control arrangement 120 may be configured to obtained calibrationdata comprises a result of a comparison between the position of the obtained position of thecalibration target 160a, 160b, 160c, 160d on the calibration structure 150 with the determinedposition of the calibration target 160a, 160b, 160c, 160d. ln yet some alternative embodiments wherein the vehicle sensor 110 may be situated in asensor module 200 comprising a plurality of sensors 110, 210, the control arrangement 120 18 may be configured to calibrate another sensor 210 of the sensor module 200, based on thetarget measurement made by the vehicle sensor 110.

The control arrangement 120 may also be configured to obtain an identity reference andconfiguration of the calibration structure 150.

The vehicle external controller 170 of the calibration structure 150 is configured to performthe method 500 according to at least some of the method steps 501-502 for calibration ofthe vehicle sensor 110 of the vehicle 101. The vehicle external controller 170 is configuredto determine position of a vehicle reference point 140 on the vehicle 101. Also, the vehicleexternal controller 170 is configured to provide calibration data relating to position of thecalibration target 160a, 160b, 160c, 160d on the calibration structure 150 and position of thevehicle reference point 140 on the vehicle 101, thereby enabling calibration of the sensor110 of the vehicle 101. ln some embodiments, the vehicle external controller 170 may be configured to provide cal-ibration data to the vehicle 101 comprising calibration data relating to position of the calibra-tion target 160a, 160b, 160c, 160d on the calibration structure 150 and position of a vehiclereference point 140 on the vehicle 101 relative to a reference coordinate system of a calibra-tion structure 150, thereby enabling determination of positions in a common coordinate sys-tem by the control arrangement 120 of the vehicle 101.

Further, the vehicle external controller 170 may be configured to obtain a position of thecalibration target 160a, 160b, 160c, 160d as determined by the sensor 110 of the vehicle101. Also, the vehicle external controller 170 may be configured to determine the obtainedposition of the calibration target 160a, 160b, 160c, 160d and the known position of the cali-bration target 160a, 160b, 160c, 160d in a common coordinate system, based on the positionof the vehicle reference point 140 on the vehicle 101. The vehicle external controller 170may furthermore be configured to compare the position of the obtained position of the cali-bration target 160a, 160b, 160c, 160d on the calibration structure 150 with the determinedposition of the calibration target 160a, 160b, 160c, 160d and provide the result of the com-parison to the control arrangement 120 of the vehicle 101. ln yet some embodiments, the vehicle external controller 170 may be configured to providean identity reference and configuration of the calibration structure 150 to the vehicle 101. 19 The control arrangement 120 of the vehicle 101 may comprise a processing circuit 620 con-figured to perform at least some of the method 400 according to method steps 401-404, in some embodiments.

Such processing circuit 620 may comprise one or more instances of a processing circuit, i.e.a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, anApplication Specific Integrated Circuit (ASIC), a microprocessor, or other processing logicthat may interpret and execute instructions. The herein utilised expression “processor” maythus represent a processing circuitry comprising a plurality of processing circuits, such as,e.g., any, some or all of the ones enumerated above.

The control arrangement 120 also comprises a receiving circuit 610 configured for receivinga signal from the sensor 110, and/ or a transceiver 130.

Furthermore, the control arrangement 120 may comprise a memory 625 in some embodi-ments. The optional memory 625 may comprise a physical device utilised to store data orprograms, i.e., sequences of instructions, on a temporary or permanent basis. According tosome embodiments, the memory 625 may comprise integrated circuits comprising silicon-based transistors. The memory 625 may comprise e.g. a memory card, a flash memory, aUSB memory, a hard disc, or another similar volatile or non-volatile storage unit for storingdata such as e.g. ROIVI (Read-Only l\/lemory), PROIVI (Programmable Read-Only Memory),EPROIVI (Erasable PROIVI), EEPROIVI (Electrically Erasable PROIVI), etc. in different embod- iments.

Further, the control arrangement 120 may comprise a signal transmitter 630. The signaltransmitter 630 may be configured for transmitting a control signal to be received by thesensor 110, 210, for calibration.

The terminology used in the description of the embodiments as illustrated in the accompa-nying drawings is not intended to be limiting of the described methods 400, 500; the controlarrangement 200; the computer program; the system 500 and/ or the vehicle 100. Variouschanges, substitutions and/ or alterations may be made, without departing from inventionembodiments as defined by the appended claims.

As used herein, the term “and/ or” comprises any and all combinations of one or more of theassociated listed items. The term “or” as used herein, is to be interpreted as a mathematical OR, i.e., as an inclusive disjunction; not as a mathematical exclusive OR (XOR), unless ex-pressly stated otherwise. ln addition, the singular forms “a”, “an” and “the” are to be inter-preted as “at least one”, thus also possibly comprising a plurality of entities of the same kind,unless expressly stated othen/vise. lt will be further understood that the terms “includes”,“comprises”, “including” and/ or “comprising”, specifies the presence of stated features, ac-tions, integers, steps, operations, elements, and/ or components, but do not preclude thepresence or addition of one or more other features, actions, integers, steps, operations, ele-ments, components, and/ or groups thereof. A single unit such as e.g. a processor may fulfilthe functions of several items recited in the claims. The mere fact that certain measures arerecited in mutually different dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage. A computer program may be stored/ distributed ona suitable medium, such as an optical storage medium or a solid-state medium suppliedtogether with or as part of other hardware, but may also be distributed in other forms such as via Internet or other wired or wireless communication system.

Claims

1. A control arrangement (120) for calibration of a vehicle sensor (110) of a vehicle(101) in cooperation with a calibration structure (150), wherein the control arrangement (120)is configured to: detect at least one calibration target (160a, 160b, 160c, 160d) on the calibrationstructure (150) via the vehicle sensor (110); determine position of the calibration target (160a, 160b, 160c, 160d), based on thedetection by the vehicle sensor (110); obtain calibration data from the calibration structure (150), relating to position of thecalibration target (160a, 160b, 160c, 160d) on the calibration structure (150) and position ofa vehicle reference point (140) on the vehicle (101); calibrate the vehicle sensor (110), based on the determined position of the calibra-tion target (160a, 160b, 160c, 160d) and the obtained calibration data.

2. The control arrangement (120) according to claim 1, further configured to: determine the obtained position of the calibration target (160a, 160b, 160c, 160d)and the determined position of the calibration target (160a, 160b, 160c, 160d) in a commoncoordinate system, based on the obtained position of the vehicle reference point (140) onthe vehicle (101); compare the position of the obtained position of the calibration target (160a, 160b,160c, 160d) on the calibration structure (150) with the determined position of the calibrationtarget (160a, 160b, 160c, 160d); and calibrate the vehicle sensor (110), based on the made comparison.

3. The control arrangement (120) according to claim 1, configured to: provide the determined position of the calibration target (160a, 160b, 160c, 160d)to a vehicle external controller (170); and wherein the obtained calibration data comprises aresult of a comparison between the position of the obtained position of the calibration target(160a, 160b, 160c, 160d) on the calibration structure (150) with the determined position ofthe calibration target (160a, 160b, 160c, 160d).

4. The control arrangement (120) according to any one of the preceding claims,wherein the vehicle sensor (110) is situated in a sensor module (200) comprising a pluralityof sensors (110, 210); and wherein the control arrangement (120) is configured to: calibrate another sensor (210) of the sensor module (200), based on the targetmeasurement made by the vehicle sensor (110). 22

5. The control arrangement (120) according to any one of the preceding claims, con-figured to: obtain an identity reference and configuration of the calibration structure (150).

6. A vehicle external controller (170) for enabling calibration of a vehicle sensor (110) of a vehicle (101), wherein the vehicle external controller (170) is configured to: determine position of a vehicle reference point (140) on the vehicle (101); provide calibration data relating to position of the calibration target (160a, 160b,160c, 160d) on the calibration structure (150) and position of the vehicle reference point(140) on the vehicle (101), thereby enabling calibration of the sensor (110) of the vehicle(101).

7. The vehicle external controller (170) according to claim 6, wherein the calibrationdata provided to the vehicle (101) comprises calibration data relating to position of the cali-bration target (160a, 160b, 160c, 160d) on the calibration structure (150) and position of avehicle reference point (140) on the vehicle (101) relative to a reference coordinate systemof a calibration structure (150), thereby enabling determination of positions in a commoncoordinate system by the control arrangement (120) of the vehicle (101).

8. The vehicle external controller (170) according to claim 6, configured to: obtain a position of the calibration target (160a, 160b, 160c, 160d) as determinedby the sensor (110) of the vehicle (101); determine the obtained position of the calibration target (160a, 160b, 160c, 160d)and the known position of the calibration target (160a, 160b, 160c, 160d) in a common co-ordinate system, based on the position of the vehicle reference point (140) on the vehicle(101); compare the position of the obtained position of the calibration target (160a, 160b,160c, 160d) on the calibration structure (150) with the determined position of the calibrationtarget (160a, 160b, 160c, 160d); and provide the result of the comparison to the control arrangement (120) of the vehicle(101).

9. The vehicle external controller (170) according to any one of claims 6-8, configuredto: provide an identity reference and configuration of the calibration structure (150) tothe vehicle (101). 23

10.vehicle sensor (110) in cooperation with a calibration structure (150), wherein the method A method (400) in a control arrangement (120) of a vehicle (101) for calibration of a (400) comprises: detecting (401) at least one calibration target (160a, 160b, 160c, 160d) on the cali-bration structure (150) via the vehicle sensor (110); determining (402) position of the calibration target (160a, 160b, 160c, 160d), basedon the detection by the vehicle sensor (110); obtaining (403) calibration data from the calibration structure (150), relating to posi-tion of the calibration target (160a, 160b, 160c, 160d) on the calibration structure (150) andposition of a vehicle reference point (140) on the vehicle (101), via wireless signalling; and calibrating (404) the vehicle sensor (110), based on the determined position of thecalibration target (160a, 160b, 160c, 160d) and the obtained calibration data.

11. A method (500) of a vehicle external controller (170) for enabling calibration of avehicle sensor (110) of a vehicle (101), wherein the method (500) comprises: determining (501) position of a vehicle reference point (140); providing (502) calibration data to the vehicle (101), relating to position of the cali-bration target (160a, 160b, 160c, 160d) on the calibration structure (150) and position of avehicle reference point (140) on the vehicle (101), thereby enabling calibration of the sensor(110) of the vehicle (101), via wireless signalling.

12. A vehicle (101), comprising:a control arrangement (120), according to any one of claims 1-5;a wireless transceiver (130);at least one vehicle sensor (110); anda vehicle reference point (140).

13.vehicle (101), wherein the calibration structure (150) comprises: A calibration structure (150) for enabling calibration of a vehicle sensor (110) of a a vehicle external controller (170) according to any one of claims 6-9; a wireless transceiver (190); at least one calibration target (160a, 160b, 160c, 160d); and at least one sensor (180a, 180b, 180c) configured to detect a vehicle reference point(140) on the vehicle (101).

14. The calibration structure (150) according to claim 13, comprising: 24 a mobility facilitating arrangement (310), configured to enable mobility of the cali- bration structure (150).

15. The calibration structure (150) according to claim 13 or 14, configured to form part 5 of a vehicle related structure.

16. pnses: A system (100) for calibration of a vehicle sensor (110), which system (100) com- a vehicle (101) according to claim 12; and a calibration structure (150) according to any one of claims 13-15.