SE1650726A1

SE1650726A1 - A wheeled motor vehicle and a method for controlling the flow of electric power of an electric system of such a vehicle

Info

Publication number: SE1650726A1
Application number: SE1650726A
Authority: SE
Inventors: Poli Ninos
Original assignee: Scania Cv Ab
Priority date: 2016-05-25
Filing date: 2016-05-25
Publication date: 2017-10-24
Also published as: WO2017204718A1; SE539664C2; DE112017002140T5

Abstract

Abstract A wheeled motor vehicle comprises an electric motor (4) config-ured to assist a driver of the vehicle to steer the vehicle and anelectric system comprising an arrangement configured to provideelectric power to the electric motor and other consumers (10-13)of electric power of the vehicle. A data collector is arranged tocollect data useable for calculating/estimating a maximum electricpower possibly needed for accurate function of the electric motorand a control unit (8) calculates/estimates said maximum electricpower and controls the arrangement to have an amount of electricpower possible to deliver to the electric motor exceeding said max- imum electric power. (Fig 2).

Description

A wheeled motor vehicle and a method for controllingthe flow of electric power of an electric system of sucha vehicle TECHNICAL FIELD OF THE INVENTION The present invention relates to a wheeled motor vehicle compris-ingø an electric motor configured to assist a driver of the vehicleto steer the vehicle, ando an electric system comprising an arrangement configured toprovide electric power to said electric motor and other con-sumers of electric power of said vehicle,as well as a method for controlling the flow of electric power of anelectric system of a wheeled motor vehicle according to the pre- amble of the independent method claim.

The invention is not restricted to a special type of wheeled motorvehicles, although the invention is particularly applicable to utilityvehicles in the form of trucks or lorries and buses, but the inventiondoes also cover for instance tractors, wheel loaders and passen- ger cars.

Furthermore, the wheeled motor vehicle may have a propulsionsystem of any conceivable type, such as only having an internalcombustion engine, in which said arrangement comprises a gen-erator for providing electric power, such an internal combustionengine in combination with an electric machine in a hybrid vehiclein which electric power for said electric motor may then be pro-vided also through a DC/DC converter of the hybrid system, or a purely electrically driven vehicle in which the arrangement may provide electric power to said electric motor through such a con-verter. Electric batteries included in the electric system may ofcourse also be used for provide electric power to the electric mo- tor.

Said electric motor may be a part of any known type of equipmentused to assist a driver of a wheeled motor vehicle to steer thevehicle, but the invention is particularly directed to such equipmentin the form of an EHPS (Electro Hydraulic Power Steering) or anEPS (Electric Power Steering) arranged in a truck, which is a rea-son for hereinafter primarily discussing the invention for that par-ticular application thereof so as to illuminate the invention but ac-cordingly not in any way restrict it thereto. EHPS will hereinafterbe used when referring to said type of equipment but does then represent all other equipment of this type.

When driving such a motor vehicle the electric system thereof mayfor different reasons be overloaded, which may be caused by par-ticular operating conditions of the vehicle, and electric batteries ofthe vehicle may at the same time have a rather poor charging level.Would then a driving situation occur in which the EHPS is to beused there will possibly not be enough electric power available foraccurate function of the EHPS and this may then be shut downwhich may be really life threatening. ln the case of a hybrid vehiclesuch an overload may occur due to an unusually high consumptionof electric power by members, such as fans, water pumps, com-pressors etc., used to cool components of the hybrid system, whichwill then jeopardize the accurate function of the EHPS when needed.

BACKGROUND ART US 2010/0006360 A1 discloses a hybrid vehicle which has anEHPS for assisting the driver of the vehicle to steer the vehicle.This vehicle is provided with a system addressing a possible bat-tery defect arising during driving of the vehicle in a high voltagepower source of the vehicle taking care of supply of electric powerto the EHPS by change of operating mode upon occurrence of sucha defect. However, this document does not discuss the aboveproblems of overloading the electric system so that there will not be enough electric power for accurate function of the EHPS.

SUMMARY OF THE INVENTION The object of the present invention is to provide a wheeled motorvehicle as well as a method of the type defined in the introductionbeing improved in at least some aspect with respect to such motor vehicles and methods already known.

This object is with respect to the wheeled motor vehicle obtainedby providing such a vehicle with the features listed in the charac- terizing part of appended patent claim 1.

By having a data collector configured to, during operation of thevehicle, collect data useable for calculating/estimating a maximumelectric power possibly needed for accurate function of said elec-tric motor in the existing driving situation of the vehicle, and a unitconfigured to calculate/estimate said maximum electric powerbased on said data received from said data collector and to control the arrangement to have an amount of electric power possible to deliver to the electric motor in the existing driving situation ex-ceeding said maximum electric power there will always, in everydriving situation of the vehicle, be enough electric power availablefor the electric motor, such as of an EHPS, so that this will thenfunction accurately even in case of a suddenly occurring drivingsituation requiring a maximum electric power to the EHPS, suchas would the vehicle have to turn sharply on a dry road at a low speed.

According to an embodiment of the invention said control unit isconfigured to, based on said data received from said data collec-tor, determine whether a change of the operation of said arrange-ment is to be carried out for obtaining a said amount of electricpower possible to deliver to the electric motor. Thus, it is by thisachieved that no action has to be taken with respect to the controlof said arrangement if not really necessary for ensuring thatenough electric power would be available for the electric motor in the existing driving situation.

According to another embodiment of the invention the control unitis configured to control said arrangement to reduce the electricpower delivered to said other consumers would said amount ofelectric power not be available for the electric motor. This meansthat the feed of electric power to consumers not critical for theproper function of the vehicle will then be reduced for ensuring thatsaid amount of electric power is available for the electric motorand by that for the EHPS when needed.

According to another embodiment of the invention said control unit is configured to control said arrangement to increase the electric power available for being delivered to said electric motor and otherconsumers of electric power would said amount of electric powernot be available for the electric motor. This constitutes anotherefficient and reliable option to ensure that the EHPS has enoughpower to function accurately irrespectively of the conditions pre- vailing.

According to another embodiment of the invention said data col-lector comprises a member configured to measure the system volt-age of said electric system, and said control unit is configured todetermine that there is a need to increase the amount of electricpower available for said electric motor when the system voltagemeasured is below a predetermined level for a predetermined pe-riod of time. An overload of the electric system resulting in a needto increase the amount of electric power available for said electric motor may reliably be determined in this way.

According to another embodiment of the invention said data col-lector comprises a member configured to measure the consump-tion of electric power by said other consumers of electric power,and said control unit is configured to compare a value of the con-sumption of electric power measured with a value of a maximumelectric power, which may be provided by said arrangement in theexisting driving situation, and to reduce the electric power deliv-ered to said other consumers or increase the electric power avail-able for being delivered to said electric motor and other consumersif the difference between these values is less than said amount. ltis by this ensured that there will be enough electric power availa-ble for an accurate function of the EHPS irrespectively of the ex- isting and approaching driving situation of the vehicle.

According to another embodiment of the invention said data col-lector is configured to collect said data in the form of the conditionof the surface of the road the vehicle is driving on. Such data couldindicate how much electric power may be needed for an accuratefunction of the EHPS, and the same apply for data in the form ofthe velocity of the vehicle, which said data collector is configuredto collect according to another embodiment of the invention.

According to another embodiment of the invention said data col-lector comprises a GPS (Global Positioning System) device con-figured to collect said data in the form of the extension of the roadthe vehicle is driving on. The use of a GPS device to collect suchdata makes it possible to predict the amount of electric power thatmay be needed for accurate function of the EHPS, since this datawill tell the control unit of the vehicle if the vehicle is approachingany location where the EHPS may be needed, such a sharp turn, a roundabout etc.

According to another embodiment of the invention said control unitis in case of receiving data from said GPS device informing abouta substantially straight road over a distance above a predeter-mined length ahead of the vehicle configured to leave said ar-rangement as it is irrespectively of other said data collected bysaid data collector. Accordingly, the control unit will then leavesaid arrangement as it is even if it is calculated or estimated thatthere will not be enough electric power for an accurate function ofthe EHPS would this require much power, since the GPS device informs that the EHPS will in any case not be needed at all for a certain time of travel corresponding to said predetermined length, which perhaps may be 200 m - 2 km.

According to another embodiment of the invention said control unitis configured to control said arrangement to have an amount ofelectric power possible to deliver to the electric motor exceedingsaid maximum electric power in case of receiving data from saidGPS device informing that the vehicle is approaching a location,such as a turn of the road or a roundabout, where the vehicle maypossibly change direction. Thus, the control unit will then ensurethat there will be enough electric power available for accuratefunction of the EHPS when there is a real need to engage theEHPS.

According to another embodiment of the invention said data col-lector is configured to collect said data in the form of the state ofa direction indicator of the vehicle, and said control unit is config-ured to delay a control of said arrangement until said direction in-dicator is actuated. This means that the control unit is preventedfrom unnecessarily controlling said arrangement when the vehicleis approaching a turn or a roundabout but not carrying out a turn, such as in an intersection.

According to another embodiment of the invention the motor vehi-cle comprises at least one electric machine for the propulsion ofthe vehicle with components associated therewith, such as electricbatteries, an inverter, a DC/DC-converter etc., as well as membersconfigured to cool these components, and the control unit is con-figured to control said arrangement to reduce the electric power delivered to said cooling members would said amount of electric power not be available for the electric motor. This constitutes afavourable way to ensure that enough electric power will be avail-able for said electric motor, since there will be no harm caused byshortly reducing the electric power fed to these cooling members,and a substantial reduction of electric power may be obtained by such a reduction.

According to another embodiment of the invention said electricsystem comprises an arrangement with a service battery, a startbattery connected in parallel with the service battery, consumersof electric energy comprising a start motor connected between op-posite poles of the service battery on a consumer side thereof op-posite to the side for connection of the service battery to the startbattery and a switch arranged between one pole of the servicebattery and one pole of the start battery so as to enable closingand opening of a current path between the start battery and saidconsumer side of the service battery, said switch is normally openduring driving of the vehicle, and the control unit is configured tocontrol said arrangement to increase the electric power availablefor being delivered to said electric motor and other consumers ofelectric power by controlling said switch to close said current pathbetween the start battery and the consumer side of the servicebattery would said amount of electric power not be available forthe electric motor. The connection of said start battery to the con-sumer side of the service battery is an efficient measure to betaken when more electric power is needed for ensuring an appro-priate function of the EHPS of the vehicle, since the start batteryof such an electric system will have a high charging degree evenif the consumption of electric power of said consumer is that high that the charging degree of the service battery is low.

According to another embodiment of the invention said electric mo-tor is a part of an EHPS (Electro Hydraulic Power Steering), anEPS (Electric Power Steering) or an EST (Electric Steered Tagaxle).

The object of the present invention is with respect to the methodobtained by providing a method according to the appended inde-pendent method claim. The advantages of such a method appearclearly from the above discussion of a motor vehicle according to the present invention.

The invention also relates to a computer program, a computer pro-gram product and an electronic control unit having the features ofthe claims directed to a computer program, a computer program product and an electronic control unit, respectively.

Other advantageous features as well as advantages of the present invention appear from the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a specific description of embodiments of the invention cited as examples. ln the drawings: Fig 1 is a simplified view illustrating a wheeled motor vehicle of the type to which the present invention relates, Fig 2 is a schematic view of parts of a motor vehicle relevantfor a first embodiment of the invention in a driving situ-ation of the vehicle, Fig 3 is a view corresponding to Fig 2 of the vehicle in an-other driving situation, Fig 4-6 are views corresponding to Figs 2 and 3 for a vehicleaccording to a second embodiment of the invention, Fig 7 is a flow chart illustrating the steps carried out in amethod according to an embodiment of the invention,and Fig 8 is a schematic view illustrating an electronic control unit for implementing a method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION Fig 1 illustrates schematically a wheeled motor vehicle 1 in theform of a truck with a front axle 2, which in a conventional way canbe steered by connection to the vehicle's steering wheel 3. Anelectric motor 4 as a part of an EHPS (Electrio Hydraulic PowerSteering) 5 is configured to assist a driver of the vehicle to steerthe vehicle. The vehicle has an electric system 6 indicated by abox with an arrangement 7 configured to provide electric power tothe electric motor and other consumers of electric power of thevehicle. The vehicle has an electronic control unit 8 configured to control the electric system of the vehicle. 11 Fig 2 illustrates schematically a part of the electric system of amotor vehicle according to a first embodiment of the invention inwhich said arrangement in the case of a hybrid vehicle has aDC/DC converter 9 configured to provide electric power to theelectric motor of the EHPS 5 and other consumers 10-13 of electricpower. ln the case of a motor vehicle having only an internal com-bustion engine for the propulsion thereof the box 9 stands for agenerator. The arrangement thus also includes 24V service bat-teries 14 of the vehicle. ln case of a hybrid vehicle the consumersof electric power 10-13 may include members for cooling compo-nents associated with the electric machine of the vehicle, such aselectric batteries, an inverter, the DC/DC converter etc., in theform of cooling fans 10, water pumps 11 and compressors 12. Thevehicle has of course many more consumers of electric power,such as heaters, lightening, music players, etc., which are left outhere for simplicity. lt is shown by the dashed lines 15, 16 how theEHPS 5 and said consumers of electric power are fed by electricpower through the converter/generator 9 and possibly also throughthe service batteries 14 when needed. The vehicle has a data col-lector 17 configured to, during operation of the vehicle, collect datauseable for calculating/estimating a maximum electric power pos-sibly needed for accurate function of the EHPS 5 in the existingdriving situation of the vehicle. Said data collector 17 can in ac-cordance with some embodiments comprise a member 18 config-ured to measure the system voltage of the electric system andprovide the control unit 8 with results from these measurements.ln accordance with some embodiments the data collector can alsocomprises a GPS device 19 configured to collect data in the form of the extension of the road the vehicle is driving on and sending 12 these data to the control unit 8. ln the case of a hybrid vehicle thetotal amount of electric power fed by the converter 9 to the con-sumers 10-13 and the EHPS is reported to the control unit 8.

The control unit 8 is configured to calculate/estimate the maximumelectric power possibly needed for accurate function of the EHPSbased on the data received from the data collector 17 and to con-trol said arrangement to have an amount of electric power possibleto deliver to the EHPS 5 in the existing driving situation exceedingsaid maximum electric power. Fig 3 illustrates how such controlmay be carried out in case of a calculation or estimation that theelectric power that may be provided to the EHPS 5 and the con-sumers of electric power 10-13 is not high enough for ensuring thatthe EHPS 5 will get enough electric power with the existing fed ofelectric power to said consumers. The control unit 8 may have re-ceived information about the consumption of the electric power ofsaid consumers 10-13 from a member 40 which is that high thatthere will not be sufficient electric power available for accuratefunction of the EHPS 5 under certain circumstances, such as aneed to make a sharp turn on a dry road surface at low speed. lnthe case of a hybrid vehicle said consumption may for example be6.5 kW and it is known that the maximum power that may be pro-vided through the converter 9 is 7 kW and a maximum electricpower possibly needed for an accurate function of the EHPS 5 maybe 2 kW. ln such a case the control unit 8 will control said con-sumers 10-13 in order to consume less power, e.g. reduce ther.p.m. of them or shutting all or some of them down. ln case ofpresence of said cooling members as consumers 10-12 these may consume a lot of power and readily overload the electric system. 13 However, the control unit may then also consider information re-ceived from the GPS device 19 and decide to leave the feeding ofelectric power as illustrated in Fig 2 even if a said too high con-sumption of electric power by the consumers 10-13 is reportedwould the GPS device inform about a substantially straight roadover a distance above a predetermined length ahead of the vehi-cle, which means that said maximum electric power possiblyneeded for accurate function of the EHPS 5 will be low in the ex-isting driving situation of vehicle. The control unit 8 is, however,configured to control said arrangement to have an amount of elec-tric power possible to deliver to the EHPS 5 exceeding said maxi-mum electric power in case of receiving data from the GPS device19 informing that the vehicle is approaching a location, such as aturn of the road or a roundabout, where the vehicle may possiblychange direction. Such information from the GPS device 19 maythen cause a change of feeding of electric power as illustrated inFig 3. This change of feeding of electric power may also be causedby a measurement result of the member 18 showing that the sys-tem voltage is below a predetermined level for a predetermined period of time.

The data collector 17 may also, such as through the GPS device19, collect data in the form of the condition of the surface of theroad the vehicle is driving on and this and also the velocity of thevehicle may be used by the control unit 8 to calculate the maximumelectric power possibly needed for accurate function of the EHPS Furthermore, it is possible to have the control unit 8 configured to reduce the feed of electric power to some consumers of electric 14 power of the vehicle when the vehicle is approaching a locationwhere the EHPS 5 is predicted to be used irrespectively of howmuch electric power is available for the function of the EHPS 5 asa safety measure. Heating of the vehicle and other not critical con-sumers of electric power will then for instance be automaticallyswitched off until such a location has been passed by the vehicle.This eliminates the risk of dips of the system voltage of the electricsystem which may cause flickering of the head lights of the vehiclewhich would not be acceptable and even more serious, the EHPSmay be shut down. Furthermore, for not unnecessarily changing orinterrupting the feed of electric power to said other consumers 10-13 of the vehicle the control unit 8 may be configured to considerinformation from a direction indicator of the vehicle and to make asaid change only if such information indicates that the vehicle willreally make a turn when approaching for instance an intersection.lt is also possible that the control unit may receive information fromthe steering wheel of the vehicle that a change of direction isstarted and then control said arrangement to change the way offeeding of electric power carried out by said arrangement, such asfrom the situation shown in Fig 2 to that shown in Fig 3.

Fig 4 illustrates schematically the appearance of the electric sys-tem of a motor vehicle according to a second embodiment of theinvention having besides the service batteries 14 two start batter-ies 20 connected in parallel with the service batteries. Only oneconsumer 21 of electric energy besides the EHPS 5 is shown here,but there are of course a number of such consumers. This con-sumer is here considered to be a start motor connected betweenopposite poles 22, 23 of the service batteries on the consumer side thereof opposite to the side for connection of the service batteries to the start batteries. A switch 24 is arranged between one pole 22of the service batteries and one pole of the start batteries so as toenable closing and opening of a current path between the startbatteries and the consumer side of the service batteries. Theswitch is normally open as illustrated in Fig 4 during driving of thevehicle. But the switch 24 is closed before all types of start motorstarts, i.e. when the combustion engine is started by means of thestart motor. This also includes start motor starts in “engine-pause”-position which takes place in stop/start-situations and electricaloperation. The switch 24 is then kept closed sufficiently long forcompletely recharging the start batteries before opening. The con-trol unit 8 is configured to control said arrangement to increase theelectric power available for being delivered to the EHPS and otherconsumers of electric power by controlling the switch 24 to closesaid current path between the start batteries and the consumerside of the service batteries would the amount of electric powerneeded for the EHPS not be available. The control unit 8 may fordeciding upon how to control the switch 24 receive the same typeof information as disclosed above while making reference to Figs2 and 3, such as from a GPS device, a member measuring thesystem voltage, a member measuring the consumption of electricpower by consumers, the velocity of the vehicle, the condition ofthe surface of the road the vehicle is driving on, actuation of adirection indicator etc. lt is shown in Fig 4 that the EHPS 5 is op-erating and that the generator/converter 9 may provide enoughelectric power for accurate function of the EHPS 5. lt is shown inFig 5 that the converter/generator 9 is not able to alone provideenough electric power to the EHPS 5, so that electric power is alsofed to the EHPS from the service batteries 14. The control unit 8 may now have received data through which it has determined that 16 there is a need to increase the electric power available to be fedto the EHPS 5 and do for that sake control the switch 24 to close,so that electric power may also be fed from the start batteries 20to the EHPS 5, which is shown in Fig 6. Such closing of the switch24 may also be combined with other measures such as temporarilyreducing the feed of power to not critical consumers or completelydisconnect them, and the switch 24 may also be controlled to au-tomatically be closed before each turn to be carried out by the vehicle.

Fig 7 illustrates a flow chart of a method according to an embodi-ment of the present invention carried out for controlling the flow ofelectric power of an electric system of a wheeled motor vehicle ofthe type shown in Figs 1-6. The method is started with a step S1by collecting data useable for calculating/estimating a maximumelectric power possibly needed for accurate function of an electricmotor of an EHPS. Said maximum electric power is then calcu-lated/estimated in a step S2. The question: ls more electric powerthan said maximum electric power available to be delivered to theEHPS? is then asked in a step S3. lf the answer to this question is"No" the method is continued through a step S4 of controlling thearrangement to make enough electric power available for the func-tion of the EHPS.

Computer program code for implementing a method according tothe invention is with advantage included in a computer programwhich can be read into the internal memory of a computer, e.g. theinternal memory of an electronic control unit of a motor vehicle.Such a computer program is with advantage provided via a com- puter program product comprising a data storage medium which 17 can be read by a computer and which has the computer programstored on it. Said data storage medium is for example an opticaldata storage medium in the form of a CD ROM disc, a DVD discetc., a magnetic data storage medium in the form of a hard disc, adiskette, a cassette tape etc., or a flash memory or a memory ofthe ROM, PROM, EPROM or EEPROM type. Fig. 8 illustrates veryschematically an electronic control unit 8 comprising an executionmeans 31, e.g. a central processor unit (CPU), for execution ofcomputer software. The execution means 31 communicates with amemory 32, e.g. of the RAM type, via a data bus 33. The controlunit 8 comprises also a non-transitory data storage medium 34,e.g. in the form of a flash memory or a memory of the ROM, PROM,EPROM or EEPROM type. The execution means 31 communicateswith the data storage medium 34 via the data bus 33. A computerprogram comprising computer program code for implementing amethod according to the invention, e.g. in accordance with the em-bodiment illustrated in Fig. 7 is stored on the data storage medium34.

The invention is of course in no way restricted to the embodimentsdescribed above, since many possibilities for modifications thereofare likely to be obvious to one skilled in the art without having toderivate from the scope of invention defined in the appended claims. lt is pointed out that it is within the scope of the invention to havethe control unit to not carry out any calculation but only an estima-tion, such as in the form of, when receiving data about a turn com-ing, an automatic disconnection of certain consumers of electric power, such as said cooling members, heaters or the like. lt is also 18 pointed out that the invention ensures that the maximum electricpower needed for the electric motor in the existing driving situationis always made available, but this amount has not to be as high asthe amount the electric motor may need under other conditions as appears from the dependent claims.

The data collector configured to collect data useable for calculat-ing/estimating a maximum electric power possibly needed for ac-curate function of the electric motor in the existing driving situationof the vehicle may be embodied in numerous different ways of which some have been described in the above disclosure.

Claims

1. _ 19 Claims A wheeled motor vehicle comprising o an electric motor (4) configured to assist a driver of the ve-hicle to steer the vehicle, and o an electric system comprising an arrangement (7) config-ured to provide electric power to said electric motor andother consumers (10-13) of electric power of said vehicle, characterized in that the vehicle also comprises ø a data collector (17) configured to, during operation of thevehicle, collect data useable for calculating/estimating amaximum electric power possibly needed for accurate func-tion of said electric motor (4) in the existing driving situationof the vehicle, and o a unit (8) configured to calculate/estimate said maximumelectric power based on said data received from said datacollector and to control said arrangement (7) to have anamount of electric power possible to deliver to the electricmotor (4) in the existing driving situation exceeding said maximum electric power. A motor vehicle according to claim 1, characterized in thatsaid control unit (8) is configured to, based on said data re-ceived from said data collector(17), determine whether achange of the operation of said arrangement (7) is to be car-ried out for obtaining a said amount of electric power possible to deliver to the electric motor (4). A motor vehicle according to claim 1 or 2, characterized inthat the control unit (8) is configured to control said arrange-ment (7) to reduce the electric power delivered to said otherconsumers (10-13) would said amount of electric power not beavailable for the electric motor. A motor vehicle according to any of the preceding claims,characterized in that said control unit (8) is configured to con-trol said arrangement (7) to increase the electric power avail-able for being delivered to said electric motor (4) and otherconsumers (10-13) of electric power would said amount of electric power not be available for the electric motor. A motor vehicle according to any of the preceding claims,characterized in that said data collector comprises a member(18) configured to measure the system voltage of said electricsystem, and that said control unit (8) is configured to deter-mine that there is a need to increase the amount of electricpower available for said electric motor (4) when the systemvoltage measured is below a predetermined level for a prede- termined period of time. A motor vehicle according to any of preceding claims, macterized in that said data collector comprises a member (40)configured to measure the consumption of electric power bysaid other consumers (10-13) of electric power, and that saidcontrol unit (8) is configured to compare a value of the con-sumption of electric power measured with a value of a maxi- mum electric power, which may be provided by said arrange- 10. 21 ment in the existing driving situation, and to reduce the elec-tric power delivered to said other consumers or increase theelectric power available for being delivered to said electricmotor (4) and other consumers (10-13) if the difference be- tween these values is less than said amount. A motor vehicle according to any of the preceding claims,characterized in that said data collector (17) is configured tocollect said data in the form of the condition of the surface ofthe road the vehicle is driving on. A motor vehicle according to any of the preceding claims,characterized in that said data collector (17) is configured to collect said data in the form of the velocity of the vehicle. A motor vehicle according to any of the preceding claims,characterized in that said data collector comprises a GPS(Global Positioning System) device (19) configured to collectsaid data in the form of the extension of the road the vehicle is driving on. A motor vehicle according to claim 9, characterized in thatsaid control unit (8) is in case of receiving data from said GPSdevice (19) informing about a substantially straight road overa distance above a predetermined length ahead of the vehicleconfigured to leave said arrangement as it is irrespectively of other said data collected by said data collector (17). 11. 12. 13. 14. 22 A motor vehicle according to claim 9 or 10, characterized inthat said control unit (8) is configured to control said arrange-ment (7) to have an amount of electric power possible to de-liver to the electric motor (4) exceeding said maximum electricpower in case of receiving data from said GPS device (19)informing that the vehicle is approaching a location, such asa turn of the road or a roundabout, where the vehicle may possibly change direction. A motor vehicle according to claim 11, characterized in thatsaid data collector (17) is configured to collect said data in theform of the state of a direction indicator of the vehicle, andthat said control unit (8) is configured to delay a control of said arrangement (7) until said direction indicator is actuated. A motor vehicle according to claim 3, characterized in that itcomprises at least one electric machine for the propulsion ofthe vehicle with components associated therewith, such aselectric batteries, an inverter, a DC/DC-converter (9) etc., aswell as members (10-12) configured to cool these compo-nents, and that the control unit (8) is configured to control saidarrangement (7) to reduce the electric power delivered to saidcooling members (10-12) would said amount of electric power not be available for the electric motor. A motor vehicle according to any of the preceding claims,characterized in that said electric system comprises an ar-rangement (7) with a service battery (14), a start battery (20) connected in parallel with the service battery, consumers of 15. 16. 23 electric energy comprising a start motor (21) connected be-tween opposite poles of the service battery on a consumerside thereof opposite to the side for connection of the servicebattery to the start battery and a switch (24) arranged betweenone pole of the service battery and one pole of the start bat-tery so as to enable closing and opening of a current pathbetween the start battery (20) and said consumer side of theservice battery (14), that said switch is normally open duringdriving of the vehicle, and that the control unit (8) is config-ured to control said arrangement (7) to increase the electricpower available for being delivered to said electric motor (4)and other consumers of electric power by controlling saidswitch (24) to close said current path between the start battery(20) and the consumer side of the service battery (14) wouldsaid amount of electric power not be available for the electric motor. A motor vehicle according to any of the preceding claims,characterized in that said electric motor (4) is a part of anEHPS (5) (Electro Hydraulic Power Steering), an EPS (Elec- tric Power Steering) or an EST (Electric Steered Tag axle). A method for controlling the flow of electric power of an elec-tric system of a wheeled motor vehicle, said motor vehicle (1)comprising an electric motor (4) configured to assist a driverof the vehicle to steer the vehicle and said electric systemcomprising an arrangement (7) configured to provide electricpower to said electric motor (4) and other consumers (10-13)of electric power of said vehicle, characterized by the steps of 17. 18. 19. 24 ø collecting data, during operation of the vehicle, useable forcalculating/estimating a maximum electric power possiblyneeded for accurate function of said electric motor (4) in theexisting driving situation of the vehicle, o calculating/estimating said maximum electric power basedon said data collected, and o controlling said arrangement to have an amount of electricpower possible to deliver to the electric motor (4) in the ex-isting driving situation exceeding said maximum electric power. Computer program comprising computer program code forcausing a computer to implement a method according to claim 16 when the computer program is executed in the computer. A computer program product comprising a non-transitory datastorage medium (34) which can be read by a computer and onwhich the program code of a computer program according to claim 17 is stored. An electronic control unit of a motor vehicle comprising an ex-ecution means (31), a memory (32) connected to the execu-tion means and a non-transitory data storage medium (34)which is connected to the execution means (31) and on whichthe computer program code of a computer program according to claim 17 is stored.