SE1951478A1 - Method and control arrangement for status estimation of a trailer unit - Google Patents

Abstract

A method (400) and control arrangement (310) for status estimation of a posterior vehicle unit (100b) attached to an anterior vehicle unit (100a), which together are forming a vehicle combination (110). The control arrangement (310) is configured to estimate status of the posterior vehicle unit (100b), based on a comparison between a determined rolling resistance and a reference rolling resistance value of the posterior vehicle unit (100b); and a determined air resistance and a reference air resistance value of the posterior vehicle unit (100b), respectively.

Description

METHOD AND CONTROL ARRANGEMENT FOR STATUS ESTIMATION OF A VEHICLEUNIT TECHNICAL FIELD This document relates to a method and a control arrangement. More particularly, a methodand a control arrangement are described, for estimating status of a posterior vehicle unitattached to an anterior vehicle unit, which together are forming a vehicle combination.

BACKGROUND When driving a vehicle combination comprising an anterior vehicle unit and a posterior vehi-cle unit, the driver (or the autonomous vehicle control arrangement) may not know the statusof the posterior vehicle unit. The status may in this context relate to or be based on theadditional resistance, added by the posterior vehicle unit to the combined vehicle.

The anterior vehicle unit may be referred to as a truck, a tractor, a traction unit, a primemover, etc. The posterior vehicle unit may be referred to as a trailer, a semi-trailer, a dolly, or similar.

The anterior vehicle unit of a vehicle combination typically comprises an engine and either acabin for a driver, or alternatively a computer for autonomous propulsion of the vehicle com-bination. The anterior vehicle unit is typically maintained according to a schedule and a motorvehicle inspection is typically made at regular time intervals by a third-party operator. Thus,the driver/ computer program for autonomous driving are relatively well-aware of the status of the anterior vehicle unit. inspection and/ or maintenance of posterior vehicle unit/s of the vehicle combination is onthe other hand often neglected and/ or disregarded. One reason may be that maintenancerequire the posterior vehicle unit to be stationary at a workshop, which is deteriorative fordistribution profit and may cause a delay in the delivery scheme.

Sometimes the anterior vehicle unit picks up a posterior vehicle unit of another owner/ oper-ator, or othen/vise is unaccustomed for the driver/ driving logic.

Thus, the variation of driving resistance between different posterior vehicle units is consid-erable. Posterior vehicle units with high resistance cause higher fuel consumption, higherwear on both the anterior vehicle unit and the posterior vehicle unit and could potentiallyincrease the risk for accidents.

Some examples of problems affecting running resistance of both the posterior vehicle unitand the vehicle combination may be e.g. low tire pressure, bad axle alignment, incorrectadjustment of the air deflector, applied brakes, a bad wheel beating, etc.

Document DE102014210776 describes a method for determining a diagnostic parameter ofa vehicle such as a car. The weight of a trailer attached to the car is discussed, but nodiagnostics or status estimation of the trailer is made.

Document DE102018005566 discloses a method for determining a range of an electricallydriven motor vehicle by estimating charging state of the vehicle battery and a driving re- sistance value of the vehicle.

The provided method is exclusively directed towards electric vehicles. Neither is the methoddirected towards calculating diagnostics of a trailer attached to the vehicle. lt would be de-sired to find a more general solution, directed towards vehicle combinations independently of propulsion means.

Document US20140121889 provides a solution for determining a running resistance of avehicle. A model-based running resistance of the vehicle is estimated and a determined en-ergy change difference between a model-based estimated energy change and an actualenergy change for the vehicle. Based on the energy change difference, a braking force isdetermined. Based here upon, an adjusted value of the model-based estimate of the runningresistance may be based.

Neither this document is discussing an analysis of the status of an attached trailer and howthe added resistance may affect the fuel consumption, cause increased wear and/ or in-crease the risk of accidents. lt would thus be desired to improve running resistance of a posterior vehicle unit/ trailer in a vehicle combination.

SUMMARY lt would be advantageous to achieve a solution overcoming, or at least alleviating, at leastsome of the above-mentioned drawback(s). ln particular, it would be desirable to enable astatus estimation of a posterior vehicle unit attached to an anterior vehicle unit, which to-gether are forming a vehicle combination. To better address one or more of these concerns,a control arrangement and a method having the features defined in the respective independ-ent claim(s) are provided.

According to a first aspect, this objective is achieved by a control arrangement for statusestimation of a posterior vehicle unit attached to an anterior vehicle unit, which together areforming a vehicle combination. The control arrangement is configured to estimate status ofthe posterior vehicle unit, based on a comparison between a determined rolling resistanceand a reference rolling resistance value of the posterior vehicle unit and a determined airresistance and a reference air resistance value of the posterior vehicle unit, respectively.

According to a second aspect, this objective is achieved by a method for status estimationof a posterior vehicle unit attached to an anterior vehicle unit, which together are forming avehicle combination. The method comprises the step of estimating status of the posteriorvehicle unit, based on a comparison between a determined rolling resistance and a referencerolling resistance value of the posterior vehicle unit; and a determined air resistance and areference air resistance value of the posterior vehicle unit, respectively.

Thanks to described aspects, by determining and analysing the running resistance of theposterior vehicle unit and extract the additional running resistance provided by the posteriorvehicle unit to the vehicle combination, status of the posterior vehicle unit may be estimated.By separating rolling resistance and air resistance of the posterior vehicle unit and comparingthem with a respective reference resistance value, a problem leading to increased resistancemay be identified. By outputting the status of the posterior vehicle unit and/ or resistancevalue of the posterior vehicle unit to the driver/ owner, measures may be taken to eliminate or at least reduce the increased resistance of the posterior vehicle unit.

Hereby, fuel/ energy consumption of the combined vehicle may be reduced, wear of vehicleparts may be reduced, service intervals may be predicted and/ or extended, and traffic safetymay be increased.

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 1A illustrates a vehicle combination comprising an anterior vehicle unit and a pos-terior vehicle unit according to an embodiment of the invention;Figure 1B illustrates a vehicle combination comprising an anterior vehicle unit and a pos- terior vehicle unit according to an embodiment of the invention; Figure 2A illustrates a vehicle combination comprising an anterior vehicle unit and a pos-terior vehicle unit according to an embodiment of the invention; Figure 2B illustrates a vehicle combination comprising an anterior vehicle unit and a pos-terior vehicle unit as regarded from above according to an embodiment of theinvenfion; Figure 3A illustrates an example of a vehicle interior of an anterior vehicle unit accordingto an embodiment; Figure 3B illustrates an example of a vehicle interior of an anterior vehicle unit accordingto an embodiment; Figure 3C illustrates an example of a vehicle interior of an anterior vehicle unit accordingto an embodiment; Figure 4 is a flow chart illustrating an embodiment of the method; Figure 5 is an illustration depicting a system according to an embodiment.

DETAILED DESCRIPTION Embodiments of the invention described herein are defined as a method and a control ar-rangement, which may be put into practice in the embodiments described below. These em-bodiments may, however, be exemplified and realised in many different forms and are not tobe limited to the examples set forth herein; rather, these illustrative examples of embodi-ments are provided so that this disclosure will be thorough and 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 1A illustrates a scenario with an anterior vehicle unit 100a and a posterior vehicleunit 100b, together forming a vehicle combination 110 driving on a road 105. The assembledvehicle combination 110 is illustrated in Figure 1B.

The anterior vehicle unit 100a may comprise e.g. a powered vehicle/ tractor/ truck/ tractionunit/ a prime mover, etc. The posterior vehicle unit may be referred to as a trailer, a semi-trailer, a dolly, or similar. The vehicle combination 110 may comprise one or several anterior vehicle units 100a and/ or posterior vehicle units 100b, such as e.g. 2, 3, 4, etc., the latter sometimes referred to as a vehicle train.

The anterior vehicle unit 100a may be driver controlled or driverless (i.e. autonomously con-trolled) in different embodiments. However, for enhanced clarity, the anterior vehicle unit100a is subsequently described as having a driver.

The posterior vehicle unit 100b may typically be unpowered but may also be powered insome embodiments. The posterior vehicle unit 100b is normally unmanned but may in someparticular embodiments be manned. Further, the posterior vehicle unit 100b may be auton-omous in some particular embodiments, configured for making at least minor position ad-justments, e.g. adjusting the geographical position at a loading bay and/ or adjusting heightof the coupling device.

The anterior vehicle unit 100a and the posterior vehicle unit 100b may exchange informationover a datalink, e.g. via a bus such as e.g. a Controller Area Network (CAN) bus, a MediaOriented Systems Transport (I\/IOST) bus, or similar. However, the datalink may alternativelybe made over a wireless connection comprising, or at least be inspired by wireless commu-nication technology such as Wi-Fi, Ethernet, Wireless Local Area Network (WLAN), UltraMobile Broadband (UMB), Bluetooth (BT), optical communication such as Infrared Data As-sociation (lrDA) or infrared transmission to name but a few possible examples of wireless communications in some embodiments. ln some embodiments, the communication between the anterior vehicle unit 100a and theposterior vehicle unit 100b in the vehicle combination 110 may be performed via Vehicle-to-Vehicle (V2V) communication, e.g. based on Dedicated Short-Range Communications(DSFIC) devices. DSFIC may work in 5.9 GHz band with bandwidth of 75 MHz and approxi-mate range of 1000 m in some embodiments.

The wireless communication may alternatively be made according to any IEEE standard forwireless vehicular communication like e.g. a special mode of operation of IEEE 802.11 forvehicular networks called Wireless Access in Vehicular Environments (WAVE). IEEE802.11p is an extension to 802.11 Wireless LAN medium access layer (MAC) and physicallayer (PHY) specification.

The anterior vehicle unit 100a comprises an anterior coupling device 101 and the posteriorvehicle unit 100b comprises a rear coupling device 111. The vehicle combination 110 iscomposed by attaching the anterior coupling device 101 of the anterior vehicle unit 100a withthe rear coupling device 111 of the posterior vehicle unit 100b. The coupling devices 101, 111 may be referred to as a towing coupling/ towing eye/ king pin.

The respective coupling devices 101, 111 may have different heights. Also, the anterior ve-hicle unit 100a and the posterior vehicle unit 100b may have been made by different manu-facturers. The anterior vehicle unit 100a may not know the height of the posterior vehicle unit100b.

Monitoring of the running resistance of the posterior vehicle unit 100b may be performed byusing obtained data concerning the posterior vehicle unit 100b, tire pressure, wheel speed,trailer weight (bellow pressure) and comparing it to a reference value based on e.g. vehiclecalculated weight and calculated running resistance of the posterior vehicle unit 100b. Bymonitoring running resistance of the posterior vehicle unit 100b, or the vehicle combination110 comprising the posterior vehicle unit 100b and comparing running resistance of the pos-terior vehicle unit 100b made at low speed with running resistance of the posterior vehicleunit 100b at high speed, air resistance can be separated from rolling resistance. The airresistance of the posterior vehicle unit 100b is neglectable at low speed while the rollingresistance of the posterior vehicle unit 100b is approximately constant independently of thevehicle speed. By then comparing the measured/ estimated air resistance and rolling re-sistance, respectively, with a respective (expected) reference value, status of the posteriorvehicle unit 100b may be estimated.

The data may be stored on-board the anterior vehicle unit 100a and sent over cellular link toa central node to be evaluated and compared to other trailers/ posterior vehicle units 100b.By comparing the same posterior vehicle units 100b connected to different anterior vehicleunits 100a the margin of error can be narrowed down. A running resistance grading for theactual trailer/ posterior vehicle unit 100b is created to ease comparison of trailers/ posteriorvehicle units 100b.

Information concerning the status of the posterior vehicle unit 100b and/ or grading infor-mation may be displayed in the instrument cluster; and/ or to the owner of the anterior vehicleunit 100a/ posterior vehicle unit 100b; and/ or to a central database. ln case the posteriorvehicle unit 100b is detected to have higher running resistance than a reference value (rep-resenting a normal or desired state of the posterior vehicle unit 100b) an alert may be gen-erated and sent to the driver (if any), the owner of the anterior vehicle unit 100a/ posteriorvehicle unit 100b; and/ or to the central database.

When the driver has acknowledged the warning, it may not be shown for the same driverconcerning the particular posterior vehicle unit 100b if the score has not changed more thana certain limit, such as e.g. 10%, 20%, etc.

Some examples of problems of posterior vehicle units 100b that may be detected may forexample be low tire pressure, bad axle alignment, incorrect adjustment of air deflector, toolong distance between the anterior vehicle unit 100a and the posterior vehicle unit 100b, thatthe brakes are applied, bad wheel bearing etc.

Information concerning the detected/ suspected problem of the posterior vehicle unit 100bmay be presented to the driver, e.g. on a display in the cabin, for example at a moment whenthe vehicle combination 110 is stationary. The driver may then confirm the presented infor-mation and make an appropriate remedy, such as for example adjust the air deflector, check/inflate the tires, adjust the distance between the anterior vehicle unit 100a and the posteriorvehicle unit 100b, etc.

One method to detect deviation per individual wheel is monitoring the speeds. Vehicle turnsmay then be excluded since the turn will affect rolling resistance and wheel speed.

The grading of posterior vehicle units 100b may be used (by owners/ producers of trailers)to justify higher price for a good (i.e. high estimated status/ low resistance values) posteriorvehicle unit 100b with low running resistance generating a drive for better posterior vehicleunits 100b.

An advantage with the provided solution is that the driver/ owner/ operator may diagnoseposterior vehicle units 100b during transportation, i.e. without having to let the posterior ve-hicle unit 100b be stationary on a testing workshop. Thus, posterior vehicle units 100b withlow estimated status/ high running resistance could be identified and appropriate measuresfor reducing the running resistance may be triggered, leading to lower costs for fuel and maintenance.

The disclosed solution may also be used to detect wear (of bearings and other similar movingparts of the posterior vehicle unit 100b over time and trigger service such as lubrication and/or replacement at an optimal moment in time. Hereby, traffic safety is enhanced as mechan-ical failures due to wear could be avoided. Emergency stops and transportation delays areavoided or at least reduced.

Thanks to the disclosed solution, the driver/ owner/ operator could to diagnose and identifytrailers/ posterior vehicle units 100b with high running resistance and thereby enable possi- bility to lower cost. lncreased fuel/ energy consumption due to a rolling resistance/ air resistance exceeding an expected/ average/ ideal value may in some embodiment be calculated and output to the driver/ owner.

Figure 2A illustrates yet an embodiment of a vehicle combination 110 formed by an anteriorvehicle unit 100a in form of e.g. a tractor and the posterior vehicle unit 100b in form of asemi-trailer 100b, driving on a road segment 105 in a driving direction 205.

Figure 2B illustrates the vehicle combination 110 of Figure 2A as regarded from above.

The anterior vehicle unit 100a comprises a rearward looking sensor 21 Oa, 210b for exampleintegrated in, or alternatively replacing, one or both of the rean/vard looking mirrors. However,the rean/vard looking sensor 210a, 210b may be situated on any other arbitrary location ofthe anterior vehicle unit 100a.

The rean/vard looking sensor 21 Oa, 210b may estimate a distance between the anterior ve-hicle unit 100a and the posterior vehicle unit 100b, which may be compared with a referencedistance. ln case the reference distance is exceeded, information may be presented to thedriver, who then may adjust, i.e. reduce, the distance and thereby reduce the air resistanceof the posterior vehicle unit 100b and thereby of the vehicle combination 110.

The rean/vard looking sensor 210a, 210b may comprise e.g. a LIDAR, a camera, a stereocamera, an infrared camera, a video camera, a radar, an ultrasound device, a time-of-flightcamera, or similar device, in different embodiments. Further, the rean/vard looking sensor21 Oa, 210b may comprise a plurality of different sensors of the same or different types.

Figure 3A illustrates an example of a vehicle interior of an anterior vehicle unit 100a forminga combined vehicle 110 together with a posterior vehicle unit 100b and depicts how the pre-viously scenario in Figure 1A-1 B and/ or Figure 2A-2B may be perceived by the driver (ifany) of the anterior vehicle unit 100a.

The anterior vehicle unit 100a comprises a control arrangement 310. The control arrange-ment 310 may comprise e.g. one or several Electronic Control Units (ECUs), typically a plu-rality of interacting ECUs. The control arrangement 310 may comprise a digital computerthat controls one or more electrical systems, or electrical sub systems, of the anterior vehicleunit 100a/ vehicle combination 110, based on e.g. information read from sensors placed atvarious parts and in different components of the vehicle combination 110. ECU is a genericterm that often is used in automotive electronics, for any embedded system that controls oneor more of the electrical system or sub systems in the vehicle combination 110. The control arrangement 310 may be particularly designated to implement air/ rolling resistance estima-tion and status estimation of the posterior vehicle unit 100b attached to the anterior vehicleunit 100a.

The control arrangement 310 may perform various calculations and estimations concerningstatus of the posterior vehicle unit 100b. The status estimation may be based on a compari-son between a determined rolling resistance and a reference rolling resistance value of theposterior vehicle unit 100b; and a determined air resistance and a reference air resistancevalue of the posterior vehicle unit 100b, respectively. The control arrangement 310 may beconnected to a database 320 wherein determined resistance values may be stored associ-ated with a reference to the posterior vehicle unit 100b and/ or the anterior vehicle unit 100a in some embodiments, and/ or the respective resistance reference values.

The rolling resistance may be determined while driving on low speed, i.e. a speed low enoughfor neglecting the posterior vehicle unit 100b. Thus, all running resistance of the posteriorvehicle unit 100b at low speed may be considered as rolling resistance. “Low speed” in thiscontext may be for example below approximately 20 km/h, below approximately 30 km/h,etc. (arbitrary, non-limiting examples). The speed threshold limit may be predetermined orconfigurable.

Various sensors 210a, 210b of the anterior vehicle unit 100a and/ or the posterior vehicleunit 100b may be used for gathering data. These sensors and measured data may for ex-ample cover thermometer /temperature, air pressures in the vehicle's tyres, the vehicle'sweight, including cargo, by measurement of axle pressures, but measured data may alsocomprise information stored in the vehicle, e.g. its length, height etc.

Some of this information from sensors on-board the vehicle may for example be used tocalculate air resistance and/ or rolling resistance.

Rolling resistance can also be measured and stored in certain alternative embodiments.Consideration may be given to the type of underlying surface, such as gravel or asphaltwhich may affect the rolling resistance. This information may be extracted from map data, orby estimating from fon/vardly directed sensors of the anterior vehicle unit 100a in combinationwith image recognition. Also, for example temperature may somewhat affect the rolling re-sistance.

The rolling resistance of the posterior vehicle unit 100b and/ or the vehicle combination 110comprising the posterior vehicle unit 100b may be calculated as: F,= C,- N, where: F, is the rolling resistance force, C, is the dimensionless rolling resistance coefficient, and Nis the normal force, the force perpendicular to the road on which the wheel is rolling.

Cr is the force needed to push (or tow) the wheeled vehicle forward (at constant speed on alevel surface, or zero grade, with zero air resistance) per unit force of weight. lt may beassumed that all wheels are the same and bear identical weight.

The estimated rolling resistance may then be compared to a reference rolling resistancevalue of the posterior vehicle unit 100b. The reference rolling resistance value may for ex-ample be based on a previously determined and stored rolling resistance value when havingused the same posterior vehicle unit 100b, or a posterior vehicle unit 100b of the same type/category. The reference rolling resistance value may alternatively comprise an expected value, or an ideal value.

Further, the control arrangement 310 may also estimate air resistance/ air drag of the pos-terior vehicle unit 100b, or the vehicle combination 110 comprising the posterior vehicle unit100b and make a comparison with a reference air resistance value of the posterior vehicleunit 100b. The air resistance is proportional to the speed of the posterior vehicle unit 100band the air resistance may be estimated by the drag equation and may be approximated by: Fd: l\)|l-\ . p . A . ua, where: Fd is the air resistance force, p is the fluid density (which may be approximated with 1.2 Kg/ms), A is the frontal area of the vehicle combination 110 comprising the posterior vehicle unit100b, u is the vehicle speed.

The control arrangement 310 may then compare the air resistance with an air resistancereference value. The reference air resistance value may for example be based on a previ-ously determined and stored air resistance value when having used the same posterior ve-hicle unit 100b, or a posterior vehicle unit 100b of the same type/ category. The reference air resistance value may alternatively comprise an expected value, or an ideal value.

The anterior vehicle unit 100a may also comprise an output device 330 such as e.g. a dis-play, a loudspeaker, a projector, a head-up display, a display integrated in the windshield of 11 the anterior vehicle unit 100a, a display integrated in the dashboard of the anterior vehicleunit 100a, a tactile device, a portable device of the vehicle driver/ owner, a set of close-eyesdisplays (i.e. intelligent glasses) of the vehicle driver/ owner, etc.; or a combination thereof.Thus, the estimated status of the posterior vehicle unit 100b may be output to the vehicledriver/ owner. Also, or alternatively, various relevant information concerning relevant measures for the driver to check may be output.

The control arrangement 310, the database 320, the sensors 210a, 210b, the output device330 may interactively communicate between themselves via e.g. a wired or wireless com-munication bus. Communication between the anterior vehicle unit 100a and the posteriorvehicle unit 100b may also be made via the communication bus. The communication busmay comprise e.g. a Controller Area Network (CAN) bus, a l\/ledia Oriented SystemsTransport (MOST) bus, Ethernet, or similar. However, the communication may alternativelybe made over a wireless connection comprising, or at least be inspired by any common wireless communication technologies such as Wi-Fi, Bluetooth, etc.

Figure 3B illustrates an example of an alternative embodiment of the interior of an anteriorvehicle unit 100a forming a combined vehicle 1 10 together with a posterior vehicle unit 100b,similar to the embodiment of Figure 3A.

However, in the illustrated embodiment of Figure 3B, the control arrangement 310, and/ orthe database 320 may be external to the anterior vehicle unit 100a, e.g. situated at a centralnode. The control arrangement 310 may then communicate wirelessly with a wireless com- munication device 340 in the anterior vehicle unit 100a.

The communication may be made over a wireless communication interface, such as e.g.Vehicle-to-Vehicle (V2V) communication, or Vehicle-to-Infrastructure (V21) communication.The common term Vehicle-to-Everything (V2X) is sometimes used. ln some embodiments, the wireless communication between the wireless communicationdevice 340 of the anterior vehicle unit 100a and the control arrangement 310 may be per-formed via V2V communication, e.g. based on Dedicated Short-Range Communications(DSRC) devices. DSFIC works in 5.9 GHz band with bandwidth of 75 MHz and approximaterange of 1000 m in some embodiments.

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) 12 specification.

Such wireless communication interface may comprise, or at least be inspired by wirelesscommunication technology such as Wi-Fi, Ethernet, Wireless Local Area Network (WLAN),Bluetooth (BT), to name but a few possible examples of wireless communications in some embodiments.

The wireless communication may alternatively be made over a wireless interface comprising,or at least being inspired by radio access technologies such as e.g. 3rd Generation Partner-ship Project (3GPP) Long Term Evolution (LTE), LTE-Advanced, Evolved Universal Terres-trial Access Network (E-UTRAN), Global System for Mobile Communications/ GroupeSpécial Mobile (GSM), Wideband Code Division Multiple Access (WCDMA), etc.

Figure 3C illustrates an example of an alternative embodiment of the interior of an anteriorvehicle unit 100a forming a combined vehicle 1 10 together with a posterior vehicle unit 100b,similar to the embodiment of Figures 3A/ 3B.

The control arrangement 310 may, based on the estimated status of the posterior vehicleunit 100b of the combined vehicle 110, estimate a problem of the posterior vehicle unit 100b/vehicle combination 110.

For example, it may be concluded that increased air resistance of the combined vehicle 110/posterior vehicle unit 100b in relation to a reference air resistance value is due to incorrectair deflector adjustment, in case the distance between the anterior vehicle unit 100a and theposterior vehicle unit 100b is within a normality distance interval. ln case the distance be-tvveen the anterior vehicle unit 100a and the posterior vehicle unit 100b is exceeding thenormality distance interval, the increased air resistance may be due to the intra vehicle unitdistance.

Information concerning the suspected reason for increased resistance may then be outputto the driver, encouraging him/ her to make an appropriate control/ adjustment.

Figure 4 illustrates an example of a method 400 according to an embodiment. The flow chartin Figure 4 shows the method 400 for status estimation of a posterior vehicle unit 100b at-tached to an anterior vehicle unit 100a, which together are forming a vehicle combination110. ln order to correctly be able to estimate the vehicular status of the posterior vehicle unit 100b,the method 400 may comprise a number of steps 401-409. However, some of these steps 13 401-409 may be performed in various alternative manners. Some method steps may only beperformed in some optional embodiments; such as e.g. steps 401-403, 405-409. Further, thedescribed steps 401-409 may be performed in a somewhat different chronological order thanthe numbering suggests. The method 400 may comprise the subsequent steps: Step 401 which only may be comprised in some embodiments, comprises determining rollingresistance of the posterior vehicle unit 100b, or the vehicle combination 110 comprising theposterior vehicle unit 100b, at a speed lower than a first threshold speed limit. The firstthreshold speed limit may set to a speed sufficiently low for the air resistance to be neglected.

For example, the first threshold speed limit may be set to e.g. 10km/h, 15km/h, 20km/h,30km/h, etc., in different embodiments.

Thus, when propagating the vehicle combination 110 at a speed below the first thresholdspeed limit, the air resistance may be neglected, i.e. all resistance of the posterior vehicleunit 100b/ vehicle combination 110 is rolling resistance.

Step 402 which only may be comprised in some embodiments wherein step 401 has beenperformed, comprises determining air resistance of the posterior vehicle unit 100b, or thevehicle combination 110 comprising the posterior vehicle unit 100b, at a speed exceeding asecond threshold speed limit.

The second threshold speed limit may be set to 50km/h, 60km/h, 75km/h, etc. in some non- limiting examples.

Step 403 which only may be comprised in some embodiments, comprises extracting infor-mation concerning the posterior vehicle unit 100b over a vehicle bus.

The extracted information may comprise e.g. an identity reference of the posterior vehicleunit 100b, a reference of the type/ category of posterior vehicle unit 100b, information fromsensors situated on the posterior vehicle unit 100b such as air pressure sensors of tires onthe posterior vehicle unit 100b or axle pressure sensors, in some embodiments.

Step 404 comprises estimating status of the posterior vehicle unit 100b, based on a com-parison between a determined rolling resistance and a reference rolling resistance value ofthe posterior vehicle unit 100b, or the vehicle combination 110 comprising the posterior ve-hicle unit 100b; and a determined air resistance and a reference air resistance value of theposterior vehicle unit 100b/ the vehicle combination 110 comprising the posterior vehicle unit100b, respectively. 14 The estimation 404 of the status of the posterior vehicle unit 100b may, in some embodi-ments wherein step 403 has been performed, be further based on the extracted 403 infor-mation concerning the posterior vehicle unit 100b over a vehicle bus.

Step 405 which only may be comprised in some embodiments, comprises estimating a prob-lem of the posterior vehicle unit 100b/ vehicle combination 110 comprising the posterior ve-hicle unit 100b, based on the estimated 404 status of the posterior vehicle unit 100b.

The estimated problem may for example comprise low tire pressure on one or several tireson the posterior vehicle unit 100b; bad axle alignment; bad wheel bearing(s) or that brakesare applied. Any, some or all of these problems, all related to increased rolling resistance ofthe posterior vehicle unit 100b, or the vehicle combination 110 comprising the posterior ve-hicle unit 100b, may be a cause of the increased rolling resistance.

The estimated problem may also, alternatively or additionally for example comprise incorrectair deflector adjustment and/ or too large distance between the anterior vehicle unit 100aand the posterior vehicle unit 100b of the vehicle combination 110. These problems are re-lated to increased air resistance of the posterior vehicle unit 100b, or the vehicle combination110 comprising the posterior vehicle unit 100b.

The estimation 405 of the problem may in some embodiments comprise the steps of obtain-ing sensor measurements from a rearward looking sensor 210a, 210b of the anterior vehicleunit 100a, of a frontal end of the posterior vehicle unit 100b. Also, the estimation 405 maycomprise calculating a distance between the anterior vehicle unit 100a and the posteriorvehicle unit 100b. The distance estimation may be made by radar/ lidar measurements, for example.

Driving on a too low tire pressure leads to increased rolling resistance and increased fuel/energy consumption, but also to increased wear of the tire (i.e. the tire in question has to bereplaced sooner than othen/vise expected). Too low tire pressure also jeopardizes the trafficsafety of the vehicle combination 110, not the least in the event of a manoeuvre or braking.

Bad axle alignment may also lead to increased rolling resistance and increased fuel/ energyconsumption, but also to increased wear of the tires on the axle (i.e. the tire in question hasto be replaced sooner than othen/vise expected).

Applied brakes not only leads to increased rolling resistance and increased fuel/ energy con-sumption, but also to increased wear of the brakes and changed behaviour of the posterior vehicle unit 100b which may surprise the driver and thereby cause an accident.

A bad wheel bearing leads to increased rolling resistance and increased fuel/ energy con-sumption but may also cause a traffic accident in case the wheel bearing is not exchangedbefore the bearing is failing completely. lncorrect air deflector adjustment and/ or too large distance between the anterior vehicle unit100a and the posterior vehicle unit 100b leads to increased air resistance and increased fuel/energy consumption, and may also change behaviour of the posterior vehicle unit 100b/ ve-hicle combination 110 which may surprise the driver when making manoeuvres in high speed, thereby causing a traffic accident.

Step 406 which only may be comprised in some embodiments wherein step 405 has beenperformed, comprises outputting information concerning the estimated 405 problem and/ orthe estimated 404 status of the posterior vehicle unit 100b.

The outputted 406 information may in some embodiments comprise information concerningthe estimated 405 problem, e.g. to the driver so that he/ she can react and check/ adjust theproblem according to the outputted 406 information.

The estimated status may be output 406 as a colour code (green, yellow, red), as a happy/sad avatar, as a number between for example 0-100, 1-10, 1-5 or some other constraints,as a letter A-F, etc.

By outputting 406 the status in an easily perceivable manner, the driver is able to instantlyunderstand the status of the posterior vehicle unit 100b without leave perceptual focus of theroad and environmental traffic situation, leading to a safer traffic situation.

The outputted 406 information may in some embodiments comprise an advice of an adjust-ment of the distance between the anterior vehicle unit 100a and the posterior vehicle unit100b when the calculated distance exceeds a threshold limit. ln some embodiments, the outputted 406 information may comprise an estimation of in-creased fuel/ energy costs due to the increased resistance of the posterior vehicle unit 100b,thereby providing easily perceivable information to the driver or vehicle owner concerningthe economical consequences of the increased resistance.

Hereby, the problem causing the increased resistance could be removed or at least reduced,leading to reduced fuel/ energy consumption and possibly also to a safer driving situation 16 and less traffic accidents.

Step 407 which only may be comprised in some embodiments wherein steps 401 and 402have been performed, comprises storing the determined 401 rolling resistance value of theposterior vehicle unit 100b and the determined 402 air resistance value of the posterior ve-hicle unit 100b in a database 320, associated with e.g. a time stamp and possibly also withan identity reference of the posterior vehicle unit 100b, identity reference of the anterior ve-hicle unit 100a, the estimated 405 problem and/ or the estimated status of the posterior ve-hicle unit 100b.

Hereby, data may be stored of a rolling/ air resistance value and/ or status of the posteriorvehicle unit 100b in the database 320, which may be used for analysis and prediction of e.g.maintenance measures of the posterior vehicle unit 100b.

By comparing degradation of the rolling/ air resistance value and/ or the status over time,service/ maintenance measures may be predicted and scheduled, thereby reducing the in-creased fuel costs due to the increased resistance value and also achieving a safer vehicle.

Step 408 which only may be comprised in some embodiments wherein step 407 has beenperformed, comprises predicting a moment in time of maintenance of the posterior vehicle unit 100b, based on the stored 407 resistance values.

By analysing the stored 407 information concerning resistance values, a degradation overtime may be detected and when reaching a trigger level, an alert may be generated and sentto the driver/ owner. Hereby maintenance may be optimised, avoiding too frequent servicestops while at the same time avoiding the resistance to increase over the trigger level. increased fuel/ energy cost due the increased resistance values is thereby reduced/ elimi-nated, leading to cost savings of the vehicle owner, besides a safer traffic situation.

Step 409 which only may be comprised in some embodiments wherein step 404 has beenperformed, comprises reducing a margin of error based on the estimated 404 status of theposterior vehicle unit 100b when having been connected to different anterior vehicle units100a.

By comparing the estimated 404 status of the posterior vehicle unit 100b when having beenforming a vehicle combination 110 with other anterior vehicle units 100a, various estimation/calculation errors and/ or resistance affection of the anterior vehicle unit 100a could be re-duced and/ or filtered out. Hereby a more reliable estimation of the rolling/ air resistance 17 values of the particular posterior vehicle unit 100b may be obtained, leading to increasedreliability of the resistance estimation.

Figure 5 illustrates an embodiment of a system 500 in a vehicle 100 comprising a controlarrangement 310, a database 320, an output device 330 and a vehicle combination 110comprising an anterior vehicle unit 100a and a posterior vehicle unit 100b.

The control arrangement 310 of the system 500 may perform at least some of the previouslydescribed steps 401-409 according to the method 400 described above and illustrated inFigure 4 for status estimation of the posterior vehicle unit 100b attached to the anterior vehi-cle unit 100a, which together are forming a vehicle combination 110.

The control arrangement 310 is configured to estimate status of the posterior vehicle unit100b, based on a comparison between a determined rolling resistance and a reference roll-ing resistance value of the posterior vehicle unit 100b, or the vehicle combination 110 com-prising the posterior vehicle unit 100b; and a determined air resistance and a reference airresistance value of the posterior vehicle unit 100b, or the vehicle combination 110 compris-ing the posterior vehicle unit 100b, respectively.

Further, in some embodiments, the control arrangement 310 may be configured to determinerolling resistance of the posterior vehicle unit 100b at a speed lower than a first thresholdspeed limit. Also, the control arrangement 310 may be additionally configured to determineair resistance of the posterior vehicle unit 100b at a speed exceeding a second thresholdspeed limit. ln yet some embodiments, the control arrangement 310 may be configured to estimate aproblem of the posterior vehicle unit 100b, based on the estimated status of the posteriorvehicle unit 100b. Further, the control arrangement 310 may be configured to output infor-mation concerning the estimated problem and/ or the estimated status of the posterior vehi-cle unit 100b via the output device 330. The information may be output to the driver and/ or the owner. ln some embodiments, the control arrangement 310 may also be configured to estimate aproblem of the posterior vehicle unit 100b and/ or the vehicle combination 110 comprisingthe posterior vehicle unit 100b. The problem may be estimated by obtaining sensor meas-urements from a rearward looking sensor 210a, 210b of the anterior vehicle unit 100a, of afrontal end of the posterior vehicle unit 100b. The problem may furthermore be estimated bycalculating a distance between the anterior vehicle unit 100a and the posterior vehicle unit 18 100b. ln addition, the control arrangement 310 may be further configured to output infor-mation comprising an advice of an adjustment of the distance between the anterior vehicleunit 100a and the posterior vehicle unit 100b when the calculated distance exceeds a thresh-old limit.

The control arrangement 310 may in addition be configured to extract information concerningthe posterior vehicle unit 100b over a vehicle bus. Further, the control arrangement 310 maybe configured to estimate the status of the posterior vehicle unit 100b further based on theextracted information. ln yet some embodiments, the control arrangement 310 may also be configured to store thedetermined rolling resistance value of the posterior vehicle unit 100b and the determined airresistance value of the posterior vehicle unit 100b in a database 320, associated with a timestamp. The control arrangement 310 may also be configured to predict a moment in time ofmaintenance of the posterior vehicle unit 100b, based on the stored resistance values.

The control arrangement 310 may also be configured to reduce a margin of error based onthe estimated status of the posterior vehicle unit 100b when having been connected to dif-ferent anterior vehicle units 100a.

The control arrangement 310 comprises a receiving circuit 510 configured for receiving asignal from sensors 210a, 21 0b; and/ or information from the posterior vehicle unit 100b overthe bus or a database 320.

Further, the control arrangement 310 comprises a processing circuitry 520 configured forperforming at least some steps 401-409 of the method 400, according to some embodiments.

Such processing circuitry 520 may comprise one or more instances of a processing circuit,i.e. a Central Processing Unit (CPU), a processing unit, a processing circuit, an ApplicationSpecific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may in-terpret and execute instructions. The herein utilised expression “processing circuitry” maythus represent a processing entity comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones enumerated above.

Furthermore, the control arrangement 310 may comprise a memory 525 in some embodi-ments. The optional memory 525 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 525 may comprise integrated circuits comprising silicon-based transistors. The memory 525 may comprise e.g. a memory card, a flash memory, a 19 USB 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 310 may comprise a signal transmitter 530 in some em-bodiments. The signal transmitter 530 may be configured for transmitting a signal to e.g. thedatabase 320, the output device 330, and/ or a warning system or warning device, for exam- ple. ln addition, the system 500 may also comprise a sensor 210a, 210b of the anterior vehicleunit 100a, in some embodiments. The sensor 210a, 210b may comprise e.g. a camera, astereo camera, an infrared camera, a video camera, radar, lidar, ultrasonic sensor, time- of-flight camera, or thermal camera or similar. The sensor 210a, 210b may be utilised for per-forming at least a part of the method 400 may in some embodiments have another mainpurpose than performing the method 400, i.e. be already existing in the anterior vehicle unit100a.

The above described method steps 401 -409 to be performed in the control arrangement 310may be implemented through the one or more processing circuitries 520 within the controlarrangement 310, together with computer program product for performing at least some ofthe functions of the steps 401-409. Thus, a computer program product, comprising instruc-tions for performing the steps 401-409 in the control arrangement 310 may perform themethod 400 comprising at least some of the steps 401-409 for status estimation of a posteriorvehicle unit 100b, when the computer program is loaded into the one or more processingcircuitries 520 of the control arrangement 310.

Further, some embodiments of the solution may comprise the anterior vehicle units 100a,comprising the control arrangement 310, for status estimation of the posterior vehicle unit100b attached to the anterior vehicle unit 100a, which together are forming the vehicle com-bination, according to at least some of the method steps 401-409. ln yet some alternative embodiments, the control arrangement 310 may be comprised in avehicle external entity such as a central server or traffic control tower.

The computer program product mentioned above may be provided for instance in the formof a data carrier carrying computer program code for performing at least some of the steps401-409 according to some embodiments when being loaded into the one or more pro-cessing circuitries 520 of the control arrangement 310. The data carrier may be, e.g., a hard disk, a CD ROIVI disc, a memory stick, an optical storage device, a magnetic storage deviceor any other appropriate medium such as a disk or tape that may hold machine readabledata in a non-transitory manner. The computer program product may furthermore be pro-vided as computer program code on a server and downloaded to the control arrangement 310 remotely, e.g., over an Internet or an intranet connection.

The terminology used in the description of the embodiments as illustrated in the accompa-nying drawings is not intended to be |imiting of the described method 400; the control ar-rangement 310; the computer program; the system 500 and/ or the anterior vehicle unit 100a.Various changes, substitutions and/ or alterations may be made, without departing from in-vention embodiments 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 mathematicalOR, 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 (17)

1. A control arrangement (310) for status estimation of a posterior vehicle unit (100b)attached to an anterior vehicle unit (100a), which together are forming a vehicle combination(110); wherein the control arrangement (310) is configured toestimate status of the posterior vehicle unit (100b), based on a comparison betweena determined rolling resistance and a reference rolling resistance value of theposterior vehicle unit (100b); anda determined air resistance and a reference air resistance value of the poste-rior vehicle unit (100b), respectively.

2. The control arrangement (310) according to claim 1, further configured to determine rolling resistance of the posterior vehicle unit (100b) at a speed lower thana first threshold speed limit; and determine air resistance of the posterior vehicle unit (100b) at a speed exceeding asecond threshold speed limit.

3. The control arrangement (310) according to any one of the preceding claims, furtherconfigured to estimate a problem of the posterior vehicle unit (100b), based on the estimated statusof the posterior vehicle unit (100b); and output information concerning the estimated problem and/ or the estimated status ofthe posterior vehicle unit (100b).

4. The control arrangement (310) according to any one of the preceding claims, furtherconfigured to estimate a problem of the posterior vehicle unit (100b) by obtaining sensor measurements from a rearward looking sensor (210a, 210b) of theanterior vehicle unit (100a), of a frontal end of the posterior vehicle unit (100b); and calculating a distance between the anterior vehicle unit (100a) and the posterior ve-hicle unit (100b); and also configured to output information comprising an advice of an ad-justment of the distance between the anterior vehicle unit (100a) and the posterior vehicleunit (100b) when the calculated distance exceeds a threshold limit.

5. The control arrangement (310) according to any one of the preceding claims, furtherconfigured to extract information concerning the posterior vehicle unit (100b) over a vehicle bus;and also configured to estimate the status of the posterior vehicle unit (100b) further basedon the extracted information. 22

6. The control arrangement (310) according to any one of the preceding claims, furtherconfigured to store the determined rolling resistance value of the posterior vehicle unit (100b) andthe determined air resistance value of the posterior vehicle unit (100b) in a database (320),associated with a time stamp; and predict a moment in time of maintenance of the posterior vehicle unit (100b), basedon the stored resistance values.

7. The control arrangement (310) according to any one of the preceding claims, furtherconfigured to reduce a margin of error based on the estimated status of the posterior vehicle unit(100b) when having been connected to different anterior vehicle units (100a).

8. A method (400) for status estimation of a posterior vehicle unit (100b) attached to ananterior vehicle unit (100a), which together are forming a vehicle combination (110),whereinthe method (400) comprises the step ofestimating (404) status of the posterior vehicle unit (100b), based on a comparisonbetweena determined rolling resistance and a reference rolling resistance value of theposterior vehicle unit (100b); anda determined air resistance and a reference air resistance value of the poste-rior vehicle unit (100b), respectively.

9. The method (400) according to claim 8, further comprising the steps of determining (401) rolling resistance of the posterior vehicle unit (100b) at a speedlower than a first threshold speed limit; and determining (402) air resistance of the posterior vehicle unit (100b) at a speed ex-ceeding a second threshold speed limit.

10.steps of The method (400) according to any one of claim 8 or claim 9, further comprising the estimating (405) a problem of the posterior vehicle unit (100b), based on the esti-mated (404) status of the posterior vehicle unit (100b); and outputting (406) information concerning the estimated (405) problem and/ or the es-timated (404) status of the posterior vehicle unit (100b).

11. The method (400) according to claim 10, wherein the estimation (405) of the problemcomprises the steps ofobtaining sensor measurements from a rearward looking sensor (210a, 210b) of the 23 anterior vehicle unit (100a), of a frontal end of the posterior vehicle unit (100b); andcalculating a distance between the anterior vehicle unit (100a) and the posterior ve-hicle unit (100b); and wherein the outputted (406) information comprisesan advice of an adjustment of the distance between the anterior vehicle unit (100a)and the posterior vehicle unit (100b) when the calculated distance exceeds a threshold limit.

12.of The method (400) according to any one of claims 8-11, further comprising the step extracting (403) information concerning the posterior vehicle unit (100b) over a vehi-cle bus; and wherein the estimation (404) of the status of the posterior vehicle unit (100b) is further based on the extracted (403) information.

13.of The method (400) according to any one of claims 8-12, further comprising the steps storing (407) the determined (401) rolling resistance value of the posterior vehicleunit (100b) and the determined (402) air resistance value of the posterior vehicle unit (100b)in a database (320), associated with a time stamp; and predicting (408) a moment in time of maintenance of the posterior vehicle unit (100b),based on the stored (407) resistance values. 14.of The method (400) according to any one of claims 8-13, further comprising the step reducing (409) a margin of error based on the estimated (404) status of the posteriorvehicle unit (100b) when having been connected to different anterior vehicle units (100a). 15.by a computer, cause the computer to carry out the method (400) according to any one of A computer program comprising instructions which, when the program is executedclaims 8-14.16. computer, cause the computer to carry out the method (400) according to any one of claims8-

14. A computer-readable medium comprising instructions which, when executed by a 17.any one of claims 1-7. An anterior vehicle unit (100a) comprising a control arrangement (310) according to