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    • 专利摘要:
    23 Abstract The invention relates to a method for limiting a vehic|e”s impact on a roadsurface. The method comprises the steps of determining (s100) a maximumderivative of the steering angle as a function of vehicle speed, and controlling(s101) the steering of the vehicle (f) based on the maximum derivative of thesteering angle. The invention also relates to a system (4) for limiting a vehic|e's impact on the road surface, a vehicle (1) comprising such a system (4), a computer program(P) and a computer program product. (Pig. zb)
    公开号:SE1650745A1
    申请号:SE1650745
    申请日:2016-05-30
    公开日:2017-12-01
    发明作者:Granström Magnus
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    A method and a system for Iimiting a vehicle”s impact on the roadsurface TECHNICAL FIELD The present invention relates to a method for Iimiting a vehicles impact on theroad surface, a system for Iimiting a vehicles, impact on the road surface, avehicle comprising such a system, a computer program and a computerprogram product according to the appended claims.
    BACKG FtOUND lleavy vehicles such as trucks, husses, construction vehicles etc. cornerise asleering servernechanism assisllrtg the oeerater ot the vehicle lvhen changingthe sleering angle hy nteans el the steering vvheel. This vtfay, the large analheavy' vehicle can easily he manoeilvreti hv using the steerlng tfvheei. Theserveniechanisrn also limlts the maneeuvrahility el the vehicle hy an inherentlirnitatlon regarding the maximum sleerlng angle anti the possible maximumeerlvatlve ei the steering angle When the vehicle is an autenorneuslyeeeratee vehicle paths and traleetories must he oeterrnlneci vvith suchllrtiltatlons/constraints taken inte consideration. This vvay, lt is ertsurecl thai thevehicle ls given a lralectory which il actually can erlve along. Other limitatiensrelating te steering angle may also he set ler safety reasens, tor example inercler te prevent that the vehicle rells over during high vehicle seeees. llaplel clianges ei steerlng angle ancl thus a high eerivale el the steerirlg angle:nav cause unnecessary wear ei a reatl. ll a vehicle is driving en a gravel roaela rapid change el steering angle may cause the contact area oi the wheels toretate against the rose surlace such that the reacl surface is rlisclacee antitherehy cause the formation et a ltole/cavity. This tyeicallv cccurs vvhen thechange el steering angle is tee last in relation te the vehicle speed. lt is thusdesired to limit the risk el wheels affecting the roacl surface in order te limit the wear of the road and the tires. Document US2üQ50034-437 At describes ahautomated vehicle yvhere operatihg parameters such as maximum rate ofchange of steering angel varies dependiiig on xri/eather conditions. This iiiay,the daniage of the ground under wet conditions is limited.
    SUMMARY OF THE INVENTION Despite known solutions in the field, there is still a need to develop a methodand system for limiting a vehicles impact on the road surface.
    An object of the present invention is to achieve an advantageous method forlimiting a vehicle's impact on the road surface by reducing the risk that thecontact area of the steered wheels of the vehicle rotates against the roadsurface, such that the road surface is frayed and/or displaced.
    An object of the present invention is to achieve an advantageous method forlimiting an autonomously operated vehicle's impact on the road surface, whichprevents the vehicle from travelling along trajectories causing the contact areaof the steered wheels to rotate against the road surface, such that the roadsurface is frayed and/or displaced.
    Another object of the present invention is to achieve an advantageous methodfor limiting a manually operated vehicle's impact on the road surface, whichinstantly informs the operator of the vehicle if there is a risk that the contactarea of the steered wheels will rotate against the road surface, such that theroad surface is frayed and/or displaced.
    A further object of the present invention is to achieve an advantageous systemfor limiting a vehic|e”s impact on the road surface by reducing the risk that thecontact area of the steered wheels of the vehicle rotates against the roadsurface, such that the road surface is frayed and/or displaced.
    Another object of the invention is to achieve an advantageous system forIimiting an autonomously operated vehicle”s impact on the road surface, whichprevents the vehicle from travelling along trajectories causing the contact areaof the steered wheels to rotate against the road surface, such that the roadsurface is frayed and/or displaced.
    A further object of the invention is to achieve an advantageous system forIimiting a manually operated vehicle”s impact on the road surface, whichinstantly informs the operator of the vehicle if there is a risk that the contactarea of the steered wheels will be rotated against the road surface, such thatthe road surface is frayed and/or displaced.
    The herein mentioned objects are achieved by a method for Iimiting a vehicle'simpact on the road surface, a system for Iimiting a vehicle's impact on the roadsurface, a vehicle, a computer program and a computer program productaccording to the independent claims.
    According to an aspect of the invention a method for Iimiting a vehicle's impacton the road surface is provided. The method comprises the steps of: - determining a maximum derivative of the steering angle as a function ofvehicle speed, and - controlling the steering of the vehicle based on the maximum derivative of thesteering angle.
    The derivative of the steering angle is the rate of change of steering angle, i.e.how fast the steering wheel is turned. The steering angle is suitably defined asthe angie of the steering wheel in relation to a zero position, in *which thesteering twheei is directed such that the steered vvheeis ot the vehicie aredirected in parailel with the longitudinei extension ot the vehicle. By maximumderivative oi steering angle means the maximum derivative ot steering angie which is suitable tor limiting a vehicies intpaot on the road stirtace. lt is thus not stlltable to have a higher derivative of the steering angle at a certainvehicle speed than the ittaximurn derivatiife of the steering angle.
    The vehicle's impact on the road surface is suitably limited by reducing the riskthat the contact areas of the steered wheels of the vehicle are rotated againstthe road surface, such that the road surface is frayed and/or displaced. Thecontact area of a steered wheel is the area of the tire of the steered wheel,which touches the ground. When the steering wheel is turned the steeredwheels are turned sideways, i.e. turned to the right or to the left, in relation tothe zero position. When the steered wheels are turned too fast in relation tothe vehicle speed the contact areas of the steered wheels may rotate againstthe road surface such that the wheels are chafed against the road surface. Theroad surface will thereby be frayed or even displaced, which means that acavity or similar may be formed in the road. This typically occur when thesteering wheel, and thus the steered wheels, is turned too fast in relation to thevehicle speed. This is specifically a problem at low vehicle speeds.
    The vehicle is suitably a heavy vehicle, such as a truck, a construction vehicle,bus or similar. Heavy vehicles entail different demands on how they areoperated compared to cars. As for cars the servorriechanlsih lirnits thernaneeuvrabilily of the heavy vehicle hy lirrtiflng the maximum possible steeringangle etc. When maltoeutritihg a heavy vehicle and turning the steering wheeltoo fast in relation to the vehicle speed, the contact areas of the steeredwheels rotate against the road surface and the ground and/or the tlres of thesteered wheels ls/are thereby exposed to consideralole strain. lf the vehicle isdriving on a oral/el road or a road of poor quality such a rapid change ofsteering angle may cause a formation of a cavity in the road due to the heavyweight/load of the vehicle. This is for example the case vvhen a vehicle isstanding still on a gravel road and the operalor of the vehicle turns the steeringwheel. in ihining applications or constructlons sites where a lot of heavyvehicles are loading/'unloading on the same location this problem may alsooccur since the vehicle speed is low and the vehicle manoeuvrlng typically invoives freetient steering ivheei movements. After some time tiie road may beso damaged that it isnï even possibie to use the read. The road thus has to berepaired and the cost of road inaintenance is tiiereby unnecessary itigh. Bydetermining a maximum derivative of the steering angle as a function ofvehicie speed and controiiiitg the steering of the vehicie based on thisntaximum derivative, such probiems can be ntiniinized. This izvay, the vehiciesimpact en the read snrtace is ilntited and the wear ct the tfenicie tires is iirnited.The higher the vehicle speed is, the faster you can turn the steering wneeiwithout the steered wheeis affecting the road surface. The maximum derivativeoi the steering angie is therefore suitahiy determined such that it increaseswith vehicie speed and thus decreases when the vehicie speed deereases.
    By determining the maximum derivative of the steering angle as a iunction oithe vehicie speed, the ntaximum derivative is zero when the tfehicie speed iszero. This means that it is not suitabie te turn the steering wheei at aii whenthe vehlcie is standing stiii.
    According to an aspect of the invention the maximum derivative of the steeringangle is determined based on a constant depending on vehicle parametersand/or road parameters. The constant may depend on the type of vehicle, theweight of the vehicle, the tires of the vehicle, the wheel diameter and/or theroad surface. The constant may be determined empirically and is suitablysaved in a control unit. The control unit suitably determines the maximum derivative of steering angle as a function of vehicle speed.
    The maximum derivative of the steering angle is preferably determined only forvehicle speeds lower than 10km/h. For vehicle speeds higher than 10 km/h theeffect of turning the steering wheel too fast is not as problematic since thesteered wheels won't affect the road surface as much. The maximumderivative of the steering angle may be between 0-2 rad/s.
    According to an aspect of the invention the step of controlling the steering ofthe vehicle comprises to determine a trajectory for the vehicle based on themaximum derivative of the steering angle. The vehicle may be autonomouslyoperated. Thus, according to an aspect of the invention a method for limitingan autonomous vehicle's impact on the road surface is provided. The methodmay comprise the steps of determining a maximum derivative of the steeringangle as a function of vehicle speed, and determining a trajectory for thevehicle based on the maximum derivative of steering angle. The method isthus used for motion planning of an autonomous vehicle. When a vehicle isautonomously ooerated oaths and traiectories must he deterrnined withlirnitatioits/coitstrairtts regarding steering angle, vehicle speed etc. taken intoconsideration. This way, it is ensured that the vehicle is given a trajectorywhich it can actually ioliow. Ûther factors, stich as iuel consumption, tirne oitravel etc. are tyoically also taken into consideration when determiningtraiectcry, By also considering the maximum derivative oi the steering angle asa function oi the vehicle speed when determining trajectory, traiectories *wherethe ntaximum derivative oi the steering angle is exceeded lreduently can beavoided. This vvay, the risk that the steereol wheels rotate against the roadsurface, such that the road surface is frayed and/or displaced is reduced andthe vehicles imoaot on the road surtace is limited. For example, it an operatorwishes to operate an autonomous vehicle trom point A to ooini B the vehiclesystem computes a plurality oi oaths which the vehicle can take to go *from A toB. Üilierent factors may he taken into consideration tivhen determining thetralectory. Each trajectory is suitably evaiuated with regard to the derivative otsteering angle required at each point tor ioliovving the trajectory. Bydetermining a maximum derivative oi the steering angle based on vehiclespeed, vvhich should not he exceedeol in order to limit the vehicles impact onthe road, traiectcries that are not suitable can he avoided.
    The maximum derivative of the steering angle preferably constitutes aparameter in a cost function for motion planning. A cost function suitably comprises a plurality of constraints relating to vehicle speed, steering angle etc.
    The determined ntaximum derivative of the steering angie is suitably set as aconstraint in a cost furtctfcn for determining trafectory, such that if a trajectorydoes :tot cornply vrith the constraint, that trajectory is not chosen for thevehicle. lf aff cornpufed trajectoršes vfofate the consfraint refating to thefnaxfrnum derivative of the steering angle, the trajectory that is best in view ofother factors is suitabiy chosen. fn order to Eimit the impact on the road surface,different trajectories are suifabfy chosen for a vehicie going to the samedestination repeatedly.
    According to an aspect of the invention step of controlling the steering of thevehicle comprises to determine if an actual derivative of steering angleexceeds the maximum derivative; and if so inform the operator of the vehicle.The vehicle may be a manually operated vehicle. Thus, according to an aspectof the invention a method for limiting a manually operated vehicle's impact onthe road surface is provided. The method may comprise the steps ofdetermining a maximum derivative of the steering angle as a function ofvehicle speed; determining if the actual derivative of the steering angleexceeds the maximum derivative; and if so, informing the operator of thevehicle. The actual derivative of the steering angle and the vehicle speed aresuitably continuously determined and compared with the maximum derivativeof the steering angle for the current vehicle speed. This way, the actualoperation of the vehicle is evaluated and suitable actions can be taken whenthe maximum derivative is exceeded. The actual derivative of the steeringangle and the current vehicle speed are suitably determined according toconventional methods. By informing the operator of the vehicle that thesteering wheel is turned too fast, the operator can instantly improve his drivingbehaviour. Also, by informing the operator each time the derivative of thesteering angle exceeds the maximum derivative of the steering angle, theoperator will be encouraged to change his behaviour in the long run and will beaware that the steering wheel should not be turned too fast at low vehiclespeeds. This is also valid for vehicles that are remotely controlled by anoperator.
    The operator of the vehicle is suitably informed by an audial alert and/or by atactile alert. The audial alert may be a continuous long sound or a plurality ofshort sounds. The tactile alert may be provided as vibrations in the steeringwheel. Alternatively or additionally, the operator is informed by informationpresented on a display unit.
    According to an aspect of the invention the method further comprises the stepto log the geographical position where the actual derivative of the steeringangle is higher than the maximum derivative. The geographical location issuitably logged in a control unit. Where an actual derivative of the steeringangle exceeds the maximum derivative of the steering angle, it is very likelythat the contact area of the steered wheels of the vehicle will rotate against theroad surface, such that the road surface is frayed and/or displaced wherebythe road is damaged. By logging these geographical locations the operator ofthe vehicle can be warned before reaching such location. The operator willthereby be aware that the road ahead may be damaged and can choose totake another road or adapt the vehicle speed. Also, by logging each occasionwhen the actual derivative of the steering angle exceeds the maximumderivative of the steering angle the information can be used for rating theoperator of the vehicle. Thus, if the operator manoeuvres the vehicle such thatthe actual derivative of the steering angle exceeds the maximum derivative ofthe steering angle the rating is decreased. lt is therefore in the interest of theoperator to manoeuvre the vehicle with the maximum derivative in mind. Bylogging the geographical location it is also possible to identify locations wherewear of the road is very probable. This information can be useful in that theroad can be inspected and repaired before the damage causes seriousproblems. The geographical location where the actual derivative of the steeringangle of a vehicle was higher than the maximum derivative may be transferredto a vehicle external system collecting the same information from a plurality ofvehicles, for example all vehicles in a vehicle fleet, within a certain constructionsite etc. This way, a more reliable conclusion regarding the road condition can be drawn, based on information from a plurality of vehicles. The geographicallocation where the actual derivative of the steering angle exceeds themaximum derivative of the steering angle may be logged for manuallyoperated vehicles as well as autonomous vehicles.
    According to an aspect of the invention a system associated with a vehicle forlimiting the vehicle”s impact on the road surface is provided. The systemcomprises a control unit adapted to determine a maximum derivative of thesteering angle as a function of vehicle speed and to control the steering of thevehicle based on the maximum derivative of the steering angle. By detetminihga maximum derivative at the eteering ahgie based oh the vehicie speed andautomaticaiiy take action based en this maximum tierivative. the oceurrence ofwheels affecting the read surface cart be aveided er iimiteoi. This wfay, thevehiciels impact en the read surface is iimiteci and the »wear ei the tires iareduced. The ceritroi unit ie suitabiy adapted to tnieterhtihe the maximumderivative ai the steering ahgie such that it ihcreases with vehieie speed andthus decreaees tfvheh the vehieie speed deereasee.
    The control unit is suitably adapted to determine the maximum derivative of thesteering angle based on a constant depending on vehicle parameters and/orroad parameters. The constant may depend on the type of vehicle, the weightof the vehicle, the tires of the vehicle, the wheel diameter and/or the roadsurface. The constant may be determined empirically and is suitably saved inthe control unit.
    The control unit is suitably adapted to determine the maximum derivative of thesteering angle only for vehicle speeds lower than 10km/h. At higher vehiclespeeds the steered wheels are seldom turned, such that the movement of thesteered wheels displaces the road surface and the impact on the road surfaceis thereby not significant.
    According to an aspect of the invention the control unit is adapted to controlthe steering of the vehicle by determining a trajectory for the vehicle based onthe maximum derivative of the steering angle. The vehicle is suitably anautonomously operated vehicle. Thus, according to an aspect of the inventiona system for limiting an autonomous vehicle's impact on the road surface isprovided, wherein a control unit is adapted to determine a maximum derivativeof the steering angle as a function of vehicle speed, and determine a trajectoryfor the vehicle based on the maximum derivative of the steering angle. The system is thus suitably a system for motion planning of an autonomous vehicle.
    By considering the maximum derivative cl the steering angle when deiermlhihgtrajectory, the control tihit can avoid trajectcries where the :maximum derivativecl the steering angle is exceedetzl frequency. This way, the risk that ihcvemehtcl the eteered vvheels cl the vehicle lifays andfcr dispiacee the road surface isreduced and the vehicles impact oh the rcacl surface is thus limited.
    The maximum derivative of the steering angle preferably constitutes aparameter in a cost function for motion planning controlled by the control unit.The cchtrel uhit is suitably adaptect te set the determihed maximum derivativeei the steering angle as a. coristraiitit ih a cest function for determiningtraiectcry, such that traiecteries that viclate the ccristraiht are hot chosen lcrthe vehicle.
    According to an aspect of the invention control unit is adapted to control thesteering of the vehicle by determining if an actual derivative of the steeringangle is higher than the maximum derivative; and if so inform the operator ofthe vehicle. The vehicle may be a manually operated vehicle. Thus, accordingto an aspect of the invention a system for limiting a manually operatedvehicle's impact on the road surface is provided. The control unit is therebyadapted to determine a maximum derivative of the steering angle as a functionof vehicle speed; determine if the actual derivative of the steering wheelexceeds the maximum derivative, and if so, inform the operator of the vehicle.The control unit is thus adapted to control the steering of the vehicle by 11 providing information relating to the maximum derivative of the steering angleand thereby affecting the driving behaviour of the operator of the vehicle. Thecontrol unit is suitably adapted to continuously determine the actual derivativeof the steering angle and compare it with the maximum derivative of thesteering angle for the current vehicle speed. This way, the control unit isadapted to evaluate the actual operation of the vehicle and to take suitableactions when the maximum derivative is exceeded. The control unit is suitablyconnected to sensor means determining the actual derivative of the steeringangle and the current vehicle speed according to conventional methods.
    The control unit is suitably adapted to inform the operator of the vehicle by anaudial alert and/or by a tactile alert. The audial alert may be a continuous longsound or a plurality of short sounds. The tactile alert may be provided asvibrations in the steering wheel. The control unit may alternatively oradditionally be adapted to inform the operator by presenting information on adisplay unit.
    According to an aspect of the invention the control unit is adapted to log thegeographical position where the actual derivative of the steering angle ishigher than the maximum derivative. By logging these geographical positionsthe control unit can warn the operator of the vehicle before reaching suchposition. The operator will thereby be aware that the road ahead may bedamaged and can choose to take another road or adapt the vehicle speed.Also, by logging the geographical position it is possible to identify locationswhere wear of the road is very probable. This information can be useful in thatthe road can be inspected and repaired before the damage causes seriousproblems. Preferably, the control unit is adapted to transfer the geographicalposition where the actual derivative of the steering angle of a vehicle washigher than the maximum derivative to a system collecting the sameinformation from a plurality of vehicles. This way, a more reliable conclusionregarding the road condition can be drawn. 12 Further objects, advantages and novel features of the present invention willbecome apparent to one skilled in the art from the following details, and alsoby putting the invention into practice. Whereas the invention is describedbelow, it should be noted that it is not restricted to the specific detailsdescribed. Specialists having access to the teachings herein will recognisefurther applications, modifications and incorporations within other fields, whichare within the scope of the invention.
    BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the present invention and further objects and advantages of it, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which: Figure 1 schematically illustrates a vehicle according to an embodiment of the invention; Figure 2a-b schematically illustrates a the function of a system for limiting avehicle's impact of the road surface according to an embodimentof the invention; Figure 3 schematically illustrates a flow chart for a method for limiting avehicle”s impact on the road surface according to an embodimentof the invention; and Figure 4 schematically illustrates a control unit or computer according to an embodiment of the invention.
    DETAILED DESCRIPTION OF THE DRAWINGS Figure i scnematicaiiy shows e side view of a vehicle i according io anernbedirneati ei the invention. The vehicle i inciudes a combuetion engine 2, esystern 4 for limiting the vehiciis-'s impact on the road surface, a steering tfvheei 13 6 and steered wheels 8 connected te the steering vrhee! 8. The system 4suitably comprises a control unit 5. A computer (not shown) may be connectedto the control unit 5. The control unit 5 is adapted to determine a maximumderivative of the steering angle as a function of vehicle speed and to controlthe steering of the vehicle 1 based on said maximum derivative of the steeringangle. The vehicle 1 may be a heavy vehicle, e.g. a truck, a constructionvehicle or a bus. The vehicle may be a hybrid vehicle comprising an electricmachine (not shown) in addition to the combustion engine 2.
    Figures 2a-b schematically shows the function of a system 4 associated with avehicle 1 for limiting the vehicle”s impact of the road surface according to anembodiment of the invention. The vehicle 1 and the system 4 are suitablyconfigured as described in Figure 1. The figures schematically show thevehicle 1 which is about to drive from point A to point B via Point C. Thevehicle is directed with the front F of the vehicle to the left at point A andshould end up with the front directed to the right at point B.
    The most common trajectory for the vehicle 1 to achieve this is shown inFigure 2a. The vehicle is typically operated such that it moves backwards topoint C along trajectory 1”. The steered wheels 8 of the vehicle 1 are thusturned slightly to the left when the vehicle 1 has reached point C. The vehicle 1 essentially stops in point C and the operator of the vehicle turns the steeringwheel 6 to the right in order to continue to point B along trajectory 2”. At point C,the steered wheels 8 of the vehicle 1 are thus turned to the right while thevehicle 1 is essentially still. The contact area of the steered wheels 8 willthereby rotate against the road surface. The road surface and the tires of thesteered wheels 8 are thus exposed to considerable strain and depending onthe road condition the weight/load of the vehicle 1may cause the steeredwheels 8 to displace the road surface and thus damage the road.
    With a system 4 for limiting the vehicle”s impact on the road surface accordingto the invention the operator of the vehicle 1 would be encouraged to take 14 another trajectory from A to B. This is illustrated in Figure 2b. The vehicle 1starts at point A and the operator operates the vehicle 1 such that it movesbackwards along trajectory 1” to point C. The steered wheels 8 of the vehicle 1are thus directed slightly to the left when reaching point C. To continue to pointB the operator of the vehicle 1 maintains the direction of the steered wheels 8at the beginning of trajectory 2” and therefore does not have to turn thesteering wheel 6 when the vehicle speed is essentially zero. This way, thesteered wheels 8 will not be moved such that they displace the road surfaceand the vehicle's impact on the road surface is thereby minimized. lf the vehicle 1 is an autonomously operated vehicle the system 4 would havedetermined a maximum derivative of the steering angle as a function of vehiclespeed and realised that the trajectory shown in Figure 2a would cause theactual derivative of the steering angle to exceed the maximum derivative of thesteering angle at point C. The system 4 would therefore determine that it ismore suitable to take the trajectory shown in Figure 2b in order to limit thevehicle”s impact on the road surface. The maximum derivative of the steeringangle as a function of vehicle speed may be set as a constraint in a costfunction for motion planning of autonomous vehicles. ln that case, thetrajectory in Figure 2a would violate the constraint and would get a penaltywhereas the trajectory in Figure 2b would satisfy the constraint, and thesystem 4 would control the vehicle 1 such that it follows the trajectory in Figure2b. lf the vehicle 1 is a manually operated vehicle the operator of the vehicle 1would probably try the trajectory in Figure 2a first. The system 4 would havedetermined a maximum derivative of the steering angle as a function of vehiclespeed and would have determined that the actual derivative of the steeringangle at point C exceeds the maximum derivative. The system 4 would thenhave informed the operator accordingly by an audial/tactile/visual alert. Thenext time the operator of the manually operated vehicle 1 is about to drive fromA to B he is aware of the problem at point C and will avoid turning the steering wheel too fast in relation to the vehicle speed. Also, the system 4 could warnthe operator prior to reaching point C to make sure that the trajectory 2' inFigure 2a is avoided.
    Figure 3 shows a flowchart for a method for limiting a vehicle's impact on theroad surface according to an embodiment of the invention. The vehicle 1 issuitably configured as described in Figure 1. The method comprises the stepsof determining s101 a maximum derivative of the steering angle as a functionof vehicle speed, and controlling s102 the steering of the vehicle 1 based onthe maximum derivative of the steering angle.
    The step to control s102 the steering of the vehicle 1 suitably comprises toreduce the risk that the contact areas of the steered wheels 8 of the vehicle 1rotate against the road surface, such that the road surface is frayed and/ordisplaced. This typically occurs when the steering wheel 6, and thus thesteered wheels 8, is turned too fast in relation to the vehicle speed. Bydetermining a maximum derivative ei the steering angie es a tunetien oi thevehicle speed and centroiiing the steering oi the vehicle based oh thismaximum derivative, such prebiertts can he reduced. This way, the vehicles impact en the read surface and the wear et the tires is timited.
    The ntaxirrtum derivative of the steering angle is suiiahiy determined such thatit inereases vvith vehieie speed and thus decreases when the vehicie speeddecreases. By determining the inaximum derivative as a function et the veitieiespeed, the maximum derivative is zero wheh the vehieie speed is zero. Thismeans that it is not suitebie te turn the steering wheei at ali when the vehieie isstanding stiii.
    The step to determine s101 the maximum derivative of the steering angle issuitably based on a constant depending on vehicle parameters and/or roadparameters. The constant may depend on the type of vehicle, the weight of thevehicle, the tires of the vehicle, the wheel diameter and/or the road surface. 16 The constant may be determined empirically and is suitably saved in thecontrol unit 5 of the system 4. The control unit 5 suitably determines themaximum derivative of the steering angle as a function of vehicle speed.
    The maximum derivative of the steering angle is preferably determined only forvehicle speeds lower than 10km/h. For vehicle speeds higher than 10 km/h theeffect of turning the steering wheel 6 too fast is not as problematic. Themaximum derivative of the steering angle may be between 0-2 rad/s.
    The step to control s102 the steering of the vehicle 1 suitably comprises todetermine a trajectory for the vehicle 1 based on the maximum derivative ofthe steering angle. The vehicle 1 may thus be an autonomously operatedvehicle. By considering the rhaxirrtum derivative of the steering ahgie whendeterrrtirting trajectory, trajectories witere the maximum derivative of thesteering arigie is exceeoied irequerttiy cart be avoideci. This vtfay, the risk thatthe contact areas of the steereoi vvheeis 8 ot the vehicle are rotatett against theroad surface, such that the steerect wheeis 8 affect and dispiace the roadsurface, is reduced and the vehicles impact on the road surface is iirnited. Themaximum derivative of the steering angle preferably constitutes a parameter ina cost function for motion planning. The oieterrrtitted maximum derivative ot thesteering angle is suitabiy set as a constrairtt in a cost function for deterrhirtingtrajectory. The step to ccrrtroi sf02 the steering of the vehicie thus corttprieesto, for each trajectory, ttetermihe if the trajectory; vioiates or satisiies thecohstraint. ii a trajectory vioiates the constraint the trajectory gets a penaityand ntay not he citosert for the vehicie t.
    The step to control s102 the steering of the vehicle 1 may comprise todetermine if an actual derivative of the steering angle exceeds the maximumderivative; and if so informing the operator of the vehicle. The vehicle is thussuitably a manually operated vehicle. The actual derivative of the steeringangle and the current vehicle speed are suitably continuously determined and compared with the maximum derivative of the steering angle for the current 17 vehicle speed. The actual derivative of the steering angle and the currentvehicle speed are suitably determined according to conventional methods. Byinforming the operator of the vehicle 1 that the steering wheel 6 is turned toofast, the operator is encouraged to instantly improve his driving behaviour andthe steering of the vehicle 1 is thus affected. Also, by informing the operatoreach time the derivative of the steering angle exceeds the maximum derivativeof the steering angle, the operator is encourage to change his behaviour in thelong run. The operator of the vehicle is suitably informed by an audial alertand/or by a tactile alert. The audial alert may be a continuous long sound or aplurality of short sounds. The tactile alert may be provided as vibrations in thesteering wheel. Alternatively or additionally, the operator is informed byinformation presented on a display unit.
    The method may further comprise the step to log the geographical positionwhere the actual derivative of the steering angle is higher than the maximumderivative. The geographical position is suitably logged in the control unit 5. Bylogging these geographical positions the operator of the vehicle 1 can bewarned before reaching such a position. The operator will thereby be awarethat the road ahead may be damaged and can choose to take another road oradapt the vehicle speed. Also, by logging the geographical position it ispossible to identify locations where wear of the road is very probable. Thisinformation can be very useful and the road can be inspected and repairedbefore the damage causes serious problems. The geographical position wherethe actual derivative of the steering angle of a vehicle 1 is higher than themaximum derivative may be transferred to a vehicle external system collectingthe same information from a plurality of vehicles. The geographical positionwhere the actual derivative of the steering angle exceeds the maximumderivative of the steering angle may be logged for manually operated vehiclesas well as autonomous vehicles.
    Figure 4 schematically illustrates a device 500. The control unit 5 and/orcomputer described with reference to Figure 1 may in a version comprise the 18 device 500. The term “link” refers herein to a communication link which may bea physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link ormicrowave link. The device 500 comprises a non-volatile memory 520, a dataprocessing unit 510 and a read/write memory 550. The non-volatile memory520 has a first memory element 530 in which a computer program, e.g. anoperating system, is stored for controlling the function of the device 500. Thedevice 500 further comprises a bus controller, a serial communication port, I/Omeans, an A/D converter, a time and date input and transfer unit, an eventcounter and an interruption controller (not depicted). The non-volatile memory520 has also a second memory element 540.
    There is provided a computer program P which comprises routines for amethod for limiting a vehicle's impact on the road surface according to theinvention. The computer program P comprises routines for determining amaximum derivative of steering angle as a function of vehicle speed. Thecomputer program P comprises routines for controlling the steering of thevehicle based on the maximum derivative of steering angle. The computerprogram P comprises routines for automatically taking action to limit thevehicle's impact on the road surface based on the maximum derivative ofsteering angle. The computer program P comprises routines for determining atrajectory based on the maximum derivative of steering angle. The computerprogram P comprises routines for determining if the actual derivative ofsteering angle exceeds the maximum derivative of steering angle. Thecomputer program P comprises routines for informing the operator of thevehicle 1 that the maximum derivative of steering angle has been exceeded.The computer program P comprises routines for logging the geographicalposition where the actual derivative of steering angle has exceeded themaximum derivative of steering angle. The program P may be stored in anexecutable form or in a compressed form in a memory 560 and/or in aread/write memory 550. 19 Where the data processing unit 510 is described as performing a certainfunction, it means that the data processing unit 510 effects a certain part of theprogram stored in the memory 560 or a certain part of the program stored inthe read/write memory 550.
    The data processing device 510 can communicate with a data port 599 via adata bus 515. The non-volatile memory 520 is intended for communication withthe data processing unit 510 via a data bus 512. The separate memory 560 isintended to communicate with the data processing unit 510 via a data bus 511.The read/write memory 550 is adapted to communicating with the dataprocessing unit 510 via a data bus 514.
    When data are received on the data port 599, they are stored temporarily inthe second memory element 540. When input data received have beentemporarily stored, the data processing unit 510 is prepared to effect codeexecution as described above.
    Parts of the methods herein described may be effected by the device 500 bymeans of the data processing unit 510 which runs the program stored in thememory 560 or the read/write memory 550. When the device 500 runs theprogram, methods herein described are executed.
    The foregoing description of the preferred embodiments of the presentinvention is provided for illustrative and descriptive purposes. It is not intendedto be exhaustive or to restrict the invention to the variants described. Manymodifications and variations will obviously be apparent to one skilled in the art.The embodiments have been chosen and described in order best to explainthe principles of the invention and its practical applications and hence make itpossible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.
    权利要求:
    Claims (18)
    [1] 1. A method for Iimiting a vehicle's impact on a road surface, characterized bythe steps of: - determining (s100) a maximum derivative of the steering angle as a functionof vehicle speed, and - controlling (s101) the steering of the vehicle (1) based on the maximumderivative of the steering angle.
    [2] 2. The method according to claim 1, wherein the maximum derivative of thesteering angle is determined based on a constant, which depends on vehicleparameters and/or road parameters.
    [3] 3. The method according to claim1 or 2, wherein the maximum derivative ofthe steering angle is determined only for vehicle speeds lower than 10km/h.
    [4] 4. The method according to any of the preceding claims, wherein the step ofcontrolling (s101) the steering of the vehicle (1) comprises to determine atrajectory for the vehicle (1) based on the maximum derivative of the steering angle.
    [5] 5. The method according to claim 4, wherein the maximum derivative of thesteering angle constitutes a parameter in a cost function for motion planning.
    [6] 6. The method according to any of claims 1-3, wherein the step of controlling(s101) the steering of the vehicle (1) comprises to determine if the actualderivative of the steering angle is higher than the maximum derivative of thesteering angle; and if so inform an operator of the vehicle (1).
    [7] 7. The method according to claim 6, wherein the operator is Informed by anaudial alert and/or by a tactile alert. 21
    [8] 8. The method according to any of claims 6-7, wherein the method furthercomprises to log the geographical position where the actual derivative of thesteering angle exceeds the maximum derivative of the steering angle.
    [9] 9. A system (4) associated with a vehicle (1) for limiting a vehicle”s impact on aroad surface, characterized in that it comprises a control unit (5) adapted todetermine a maximum derivative of steering angle as a function of vehiclespeed, and to control the steering of the vehicle (1) based on the maximum derivative of steering angle.
    [10] 10. The system according to claim 9, wherein the control unit (5) is adapted todetermine the maximum derivative of the steering angle based on a constant,which depends on vehicle parameters and/or road parameters.
    [11] 11. The system according to any of claims 9-10, wherein the control unit (5) isadapted to determine the maximum derivative of the steering angle only forvehicle speeds lower than 10km/h.
    [12] 12. The system according to any of claims 9-11, wherein the control unit (5) isadapted to control the steering of the vehicle (1) by determining a trajectory forthe vehicle (1) based on the maximum derivative of the steering angle.
    [13] 13. The system according to claim 12, wherein the maximum derivative of thesteering angle constitutes a parameter in a cost function for motion planning.
    [14] 14. The system according to any of claims 9-11, wherein the control unit (5) isadapted to control the steering of the vehicle (1) by determining if an actualderivative of the steering angle is higher than the maximum derivative of thesteering angle; and if so inform the operator of the vehicle. 22
    [15] 15. The system according to claim 14, wherein the control unit (5) is adaptedto log the geographical position where the actual derivative of the steeringangle exceeds the maximum derivative of the steering angle.
    [16] 16. A vehicle, characterized in that it comprises a system (4) according toany of claims 9-15.
    [17] 17. A computer program (P), wherein said computer program comprisesprogram code for causing an electronic control unit (5; 500) or a computer(500) connected to the electronic control unit (5; 500) to perform the stepsaccording to any of the claims 1-8.
    [18] 18. A computer program product comprising a program code stored on acomputer-readable medium for performing the method steps according to anyof claims 1-8, when said computer program is run on an electronic control unit(5; 500) or a computer (500) connected to the electronic control unit (5; 500)
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    同族专利:
    公开号 | 公开日
    DE102017004897A1|2017-11-30|
    SE541613C2|2019-11-12|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    GB2386970A|2002-03-26|2003-10-01|Mcmurtry Ltd|Environmentally responsive ground maintenance equipment|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1650745A|SE541613C2|2016-05-30|2016-05-30|A method and system for limiting an autonomous vehicle´s impact on a road surface|SE1650745A| SE541613C2|2016-05-30|2016-05-30|A method and system for limiting an autonomous vehicle´s impact on a road surface|
    DE102017004897.5A| DE102017004897A1|2016-05-30|2017-05-22|Method and system for limiting the effect of a vehicle on the road surface|
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