SE1550533A1 - Method and system for controlling a clutch of a vehicle - Google Patents

Abstract

The invention relates to a method for controlling a clutch. (106) of a vehicle (100) comprising driver manoeuvrable means. (118),a clutch pedal, manoeuvring the clutch and being movable between a first end position (A) and a second end position (B). Transmittable torque of said clutch (106) is controlled on the basis of the position of said driver manoeuvrable means (118) . The method includes, for a plurality of different magnitudes of at least one force forming at least part of the driving resistanceof said vehicle (100) : - controlling said clutch (106) such that transmittable torque of at least one position in a first portionof said movement region (A-B) of said driver controllable means (118) gives rise to a propelling force on the vehicle drive wheels (113, 114) substantially corresponding to the magnitude of said at least one force. Fig. 4B

Description

lO METHOD AND SYSTEM FOR CONTROLLING A CLUTCH OF A VEHICLEField of the invention The present invention relates to vehicles, and in particularto a method and system for controlling a clutch of a vehicle.The present invention also relates to a vehicle, as well as acomputer program and a computer program product that implement the method according to the invention.Background of the invention There exist various kinds of vehicle transmissions. Forexample, vehicle transmissions can be of a fully automatickind, where a vehicle control system controls completely gearchanging operations. The gearboxes being used in these systemsmay consist of automated manual transmissions where thevehicle control system automatically controls gear shifting in “manual” gearboxes.

There also exist manual transmissions where the vehicle driveris in control of the gear changing operation. A change of gearin manual transmissions is often performed through the use ofa driver controllable clutch, oftentimes through the use of aclutch pedal. Clutches can also be used in automated manualtransmissions, in which case clutch operation is controlled bythe vehicle control system and not by the driver. There alsoexist systems having automated manual transmissions, wheredriver controllable means such as a clutch pedal is stillpresent and used e.g. when starting the vehicle fromstandstill. When the vehicle has been set in motion, use ofthe clutch in subsequent changes of gear can be controlledcompletely by the vehicle control system without driver interaction.

Irrespective of the particular kind of transmission being used driver comfortability is oftentimes an aspect of interest when lO designing a vehicle powertrain. For example, it is essentialthat the vehicle behaves as expected by the driver when being driven on roads.

Such vehicle behaviour can relate to various different aspectsand, for example, relate to the manner in which the vehiclebehaves when performing a start from standstill and when beingmanoeuvred with high precision, e.g. when manoeuvring thevehicle to and from loading docks/loading bays. Situations ofthis kind often involve operation of a clutch, and it isessential that the clutch transmits torque in an expectedmanner so that the vehicle thereby also behaves as expected by the driver.Summary of the invention It is an object of the present invention to provide a methodand system that facilitates clutch operation in particularwhen starting a vehicle from standstill and when operating thevehicle at low speeds. This object is achieved by a method according to claim l.

According to the present invention, it is provided a methodfor controlling a clutch of a vehicle, the vehicle including aclutch for selectively transmitting torque to and/or from afirst power source, said vehicle further including drivermanoeuvrable means for manoeuvring a clutch, said drivermanoeuvrable means being movable in a movement region betweena first end position and a second end position, transmittabletorque of said clutch being controlled by a vehicle controlsystem on the basis of the position of said drivermanoeuvrable means in said movement region. The methodincludes, for a plurality of different magnitudes of at leastone force forming at least part of the driving resistance of said vehicle: lO - controlling said clutch on the basis of the position of saiddriver manoeuvrable means in said movement region independence of the magnitude of said at least one force, further including: - controlling said clutch such that transmittable torque of atleast one position in a first portion of said movement regionof said driver controllable means gives rise to a propelling force on the vehicle drive wheels substantially corresponding to the magnitude of said at least one force.

The driver manoeuvrable means can, for example, be a clutchpedal. The magnitude of said at least one force can be anestimated magnitude, and according to one embodiment of theinvention the estimation of the magnitude of said at least oneforce is part of the method according to the invention.Likewise, a device according to the invention can be arrangedto perform the estimation. According to one embodiment said atleast one force is represented by the vehicle driving resistance.

As was mentioned above, it is important that vehicles behaveas expected by the driver, e.g. in situations when manoeuvredthrough the use of a clutch. For example, when manoeuvring avehicle in places where space is limited, the manoeuvring ofthe vehicle often involve a number of driver controlledopenings and closings of the clutch. It is also important thatthe vehicle behaves as expected e.g. when performing a startfrom standstill. Manoeuvring in situations according to theabove often involves a partially open clutch, i.e. the clutchis slipping. That is, the output shaft of the power source(e.g. a combustion engine) rotates at a different speed thanthe gearbox input shaft, and hence the clutch is onlypartially engaged. lO When the clutch is slipping part of the work produced by thepower source is dissipated over the clutch, usually in theform of friction losses. The clutch slip, consequently, allowsthe vehicle to be propelled at lower speeds than wouldotherwise be possible, and hence facilitates manoeuvring at higher accuracy.

However, clutch plates often engage and disengage in a non-linear manner, i.e. the clutch has a non-linearcharacteristic. That is, the relation between transmittabletorque and position of the movable clutch element(s) beingused to control the transmittable torque is not linear.Manoeuvring of the clutch in a desired manner can thereforestill be difficult due to this non-linearity, e.g. in order totransmit precisely the amount of torque that is required topropel the vehicle in a manner intended by the driver in orderto avoid unexpected accelerations/decelerations. Also, thedriving conditions may vary substantially from one situationto another, e.g. having as result that the required torque tobe transmitted by the clutch e.g. to overcome the drivingresistance may differ to a great extent from one situation to another.

Correspondingly, this means that actual clutch pedal movement,e.g. when setting a vehicle in motion, may vary substantiallyin dependence of the current driving resistance. Suchvariations are increased due to the non-linearity according tothe above. The driving resistance represents the resultantforce that must be overcome in order to accelerate the vehicleand/or set the vehicle in motion from standstill. The drivingresistance may vary substantially from one situation toanother, e.g. in dependence on vehicle speed, load (vehicle mass) and road inclination. lO Oftentimes the operation of the clutch, such as themanoeuvring of a clutch friction element, and hence theengagement of the clutch, is controlled by driver manoeuvrablemeans such as a clutch pedal that is mechanically linked tothe clutch movable elements. This means that the clutchoperation is constrained by the characteristics of the mechanical linkage.

The present invention, however, relates to systems where thedriver manoeuvrable means is not used to control the clutchdirectly through the use of a mechanical linkage, but,instead, clutch-by-wire systems. In clutch-by-wire systems anelectrical signal representing e.g. a clutch pedal position istranslated into a corresponding clutch movement. For example,a position sensor or other suitable means can be used todetect a position of the driver manoeuvrable means, such ase.g. the position of a clutch pedal. An electrical signalrepresenting this position is then translated into acorresponding driver request regarding clutch operation, andthe vehicle control system controls the actual clutch movementon the basis of the signal representing the position of theclutch pedal. The actual clutch movement, consequently, is notmechanically linked to movements of the driver manoeuvrable ITIGÛIIS .

In general, from a driver perspective, a clutch-by-wire systembehaves in a manner similar to systems having a mechanicallinkage according to the above, but clutches of this kind canalso be controlled fully automatically by the vehicle control system, e.g. in automated manual transmissions (AMT).

According to the present invention, it has been realized thatdrivability with regard to operation of the clutch can be improved in vehicles having a clutch-by-wire system. lO According to the present invention, this is accomplished bythe use of a method which changes the dependency between theposition of the driver manoeuvrable means and resultingtransmittable torque of the clutch. The dependency is changedsuch that a particular position of the driver manoeuvrablemeans, e.g. a particular clutch pedal position, is arranged tocorrespond to a propelling force on the drive wheels thatsubstantially or precisely meet said at least one forceforming part of the vehicle driving resistance, such as e.g.the current driving resistance. According to one embodimentsaid position can be any position in a specific portion of themovement region, This is further arranged to be fulfilled fora plurality of magnitudes of the at least one force (drivingresistance). That is, the current driving resistance may bearranged to always be met by a corresponding transmittabletorque at the same clutch pedal position irrespective of the actual magnitude of the driving resistance.

According to one embodiment, the dependency is arranged suchthat the transmittable torque of the clutch of said particularposition is arranged to always correspond to the currentdriving resistance of the vehicle. The driver controllablemeans for controlling a clutch is, in general, movable in amovement region between a first end position and a second endposition, where the opening/closing of the clutch is dependenton the position of said driver controllable means.Consequently, according to the present invention, the saidparticular position of the driver manoeuvrable means willresult in different transmittable torques in dependence of the variations in driving resistance.

Consequently, the driver of the vehicle can always be aware ofe.g. the clutch pedal position at which the clutch will transmit a torque corresponding to propelling force lO corresponding to the current driving resistance. In this way,irrespective of whether the vehicle is e.g. heavily loaded orless heavily loaded, and irrespective of whether the vehicleis starting from standstill on a horizontal surface or in anuphill inclination, one and the same clutch pedal position canbe arranged to always, or substantially always, correspond tothe driving resistance prevailing at the particular situation.Consequently the driver will always be able to know at which clutch pedal position vehicle motion will begin.

When a vehicle is set in motion from standstill this, unlessthe vehicle takes off in a downhill slope, in general occurswhen the transmittable torque of the clutch gives rise to avehicle propelling force on the vehicle drive wheels thatexceeds the prevailing driving resistance. These forcesinclude rolling resistance, air resistance and influence ofthe force of gravity. For example, when the drivermanoeuvrable means is a clutch pedal, the dependency, such asclutch pedal characteristic, is made to depend on said at least one force forming part of the driving resistance.

According to one embodiment of the present invention, controlaccording to the present invention is only utilized when thedriving resistance is such that the driving resistance in itself is not capable of setting the vehicle in motion in the desired direction of travel.

According to one embodiment, the clutch pedal characteristicis further controlled such that variations in transmittabletorque as a function of movement of the driver manoeuvrablemeans is reduced about said position or portion of movementregion. In this way, driveability is further improved to the driver. lO Further, as is appreciated by the person skilled in the art,clutches may be of various designs, and the particular design,e.g. whether the clutch is a friction clutch or not, is not ofrelevance to the present invention. The present invention is applicable in any clutch-by-wire system.

Further characteristics of the present invention andadvantages thereof are indicated in the detailed descriptionof exemplary embodiments set out below and the attached drawings.Brief description of the drawingsFig. 1A illustrates a powertrain of an exemplary vehicle; Fig. lB illustrates an example of a control unit in a vehicle control system; Fig. lC illustrates a clutch pedal of the exemplary vehicle ofFig. lA.

Fig. 2 illustrates an exemplary method according to the present invention.

Fig. 3 illustrates an exemplary clutch pedal characteristic ofa vehicle in which the present invention can advantageously be utilised.

Fig. 4A illustrates a first exemplary clutch pedal characteristic according to the present invention.

Fig. 4B illustrates a second exemplary clutch pedal characteristic according to the present invention.

Fig. 5 illustrates a further clutch pedal characteristic according to the present invention.Detailed description of exemplary embodiments The driver controllable means for controlling a clutch is exemplified for a clutch pedal in the following detailed description. The present invention is, however, applicable forany kind of driver controllable means for controlling a clutch.

Fig. 1A schematically depicts a powertrain of an exemplaryvehicle 100. The powertrain comprises a power source, in thepresent example a combustion engine 101, which, in aconventional manner, is connected via an output shaft of thecombustion engine 101, normally via a flywheel 102, to agearbox 103 via a clutch 106. An output shaft 107 from thegearbox 103 propels drive wheels 113, 114 via a final drive108, such as a common differential, and drive axles 104, 105 connected to said final drive 108.

The combustion engine 101 is controlled by the vehicle controlsystem via a control unit 117. The clutch 106 and gearbox 103are also controlled by the vehicle control system by means ofa control unit 116. According to the present example, theclutch consists of a dry clutch where a friction element(disc) 110 is connected to, and rotates with, a first gearboxelement, e.g. an input shaft 109 of the gearbox 103. Thefriction element 110 selectively engages the flywheel 102, orany other suitable rotating part of the combustion engine 101,to transmit torque to/from the combustion engine 101, i.e.between combustion engine 101 and powertrain componentsdownstream of the clutch 106, such as to/from at least one of the drive wheels 113, 114 via the gearbox 103.

The engagement of the friction element 110 with the engineflywheel 102 is controlled by means of a pressure plate 111 bymeans of a lever arm 112, which is manoeuvred by a clutch actuator 115.

In systems where the clutch 106 is controlled directly by means of a clutch pedal, the clutch pedal is mechanically linked to the clutch. For example, the clutch pedal can bemechanically linked to the lever arm 112 in order to directlycontrol movement of the friction element 110. It is to beunderstood, however, that the exemplified clutch is merely anexample, and that clutches, irrespective of whether the clutchconstitutes part of a clutch-by-wire system or is controlledmechanically by driver controllable means, may be of variousdesigns. For example, the clutch actuator may be arranged coaxially with the gearbox input shaft 109.

According to the disclosed system, opening and closing of theclutch 106 may still be controlled by the driver using aclutch pedal 118, however with the difference that theinfluence of the clutch actuator 115 on the lever arm 112 iscontrolled by the vehicle control system on the basis of signals representing the clutch pedal 118 position.

That is, the actual movement of the lever arm 112 is no longermechanically linked to the clutch pedal 118. This means, inturn, that the clutch pedal 118 position, instead, is used asa request for a particular clutch operation, which is then, bymeans of the vehicle control system, translated into an actualclutch movement via the clutch actuator 115. Still, thepositioning of the lever arm 112 is dependent on the clutch pedal 118 position.

An exemplary clutch pedal 118 is schematically shown in Fig.1C. The clutch pedal 118 is movable within a movement regiondefined by two end positions A, B, defining an angular ranged. The clutch pedal 118 position in said movement region canbe determined, e.g. by means of a suitable sensor, such as,for example, an angle sensor 119 or any other suitable kind ofsensor which determines the current position of the clutchpedal 118 in the movement region in which the clutch pedal is movable. 11 The present invention takes advantage of the fact that theclutch pedal is not physically linked to the clutch so thatthe clutch pedal characteristic, i.e. the relationship betweenclutch pedal position and transmittable torque over theclutch, can be adapted to a particular situation. This isaccomplished by controlling the clutch, e.g. by controllingthe dependency of the movement of the friction element 110and/or the lever arm 112 in relation to clutch pedal 118movement such that transmittable torque of one and the sameclutch pedal position always, or at least for a plurality ofdifferent situations where different driving resistancesprevail, result in a propelling force of the vehicle drivewheels that corresponds, or substantially corresponds, to thevehicle driving resistance. As is explained below, the drivingresistance can at least in some instances be considered to berepresented by at least one force forming part of the drivingresistance, e.g. when this force constitutes a major portionof the driving resistance. An exemplary method 200 of thepresent invention is shown in Fig. 2, which method can beimplemented at least partly e.g. in the control unit 116 forcontrolling the clutch 106 and gearbox 103. As indicatedabove, the functions of a vehicle are, in general, controlledby a number of control units, and control systems in vehiclesof the disclosed kind generally comprise a communication bussystem consisting of one or more communication buses forconnecting a number of electronic control units (ECUs), orcontrollers, to various components on board the vehicle. Sucha control system may comprise a large number of control units,and the control of a specific function may be divided between two or more of them.

For the sake of simplicity, Fig. 1A depicts only control units116-117, but vehicles 100 of the illustrated kind are often 12 provided with significantly more control units, as one skilledin the art will appreciate. Control units 116-117 are arrangedto communicate with one another and various components viasaid communication bus system and other wiring, partly indicated by interconnecting lines in Fig. 1A.

The present invention can be implemented in any suitablecontrol unit in the vehicle 100, and hence not necessarily inthe control unit 116. The control of the clutch 106 accordingto the present invention will usually depend on signals beingreceived from other control units and/or vehicle components,and it is generally the case that control units of thedisclosed type are normally adapted to receive sensor signalsfrom various parts of the vehicle 100. The control unit 116will, for example, receive signals from clutch pedal positionsensor 119 and clutch actuator 115. Further, the control unitwill receive signals representing, or signals from which canbe determined, the current driving resistance and/or one ormore forces forming part of the current driving resistance, ofthe vehicle 100. Control units of the illustrated type arealso usually adapted to deliver control signals to variousparts and components of the vehicle, e.g. to control the clutch actuator 115.

Control of this kind is often accomplished by programmedinstructions. The programmed instructions typically consist ofa computer program which, when executed in a computer orcontrol unit, causes the computer/control unit to exercise thedesired control, such as method steps according to the presentinvention. The computer program usually constitutes a part ofa computer program product, wherein said computer programproduct comprises a suitable storage medium 121 (see Fig. IB)with the computer program 126 stored on said storage medium 121. The computer program can be stored in a non-volatile 13 manner on said storage medium. The digital storage medium 121can, for example, consist of any of the group comprising: ROM(Read-Only Memory), PROM (Programmable Read-Only Memory),EPROM (Erasable PROM), Flash memory, EEPROM (ElectricallyErasable PROM), a hard disk unit etc, and be arranged in or inconnection with the control unit, whereupon the computerprogram is executed by the control unit. The behaviour of thevehicle in a specific situation can thus be adapted by modifying the instructions of the computer program.

An exemplary control unit (the control unit 116) is shownschematically in Fig. 1B, wherein the control unit cancomprise a processing unit 120, which can consist of, forexample, any suitable type of processor or microcomputer, suchas a circuit for digital signal processing (Digital SignalProcessor, DSP) or a circuit with a predetermined specificfunction (Application Specific Integrated Circuit, ASIC). Theprocessing unit 120 is connected to a memory unit 121, whichprovides the processing unit 120, with e.g. the stored programcode 126 and/or the stored data that the processing unit 120requires to be able to perform calculations. The processingunit 120 is also arranged so as to store partial or final results of calculations in the memory unit 121.

Furthermore, the control unit 112 is equipped with devices122, 123, 124, 125 for receiving and transmitting input andoutput signals, respectively. These input and output signalscan comprise waveforms, pulses or other attributes that thedevices 122, 125 for receiving input signals can detect asinformation for processing by the processing unit 120. Thedevices 123, 124 for transmitting output signals are arrangedso as to convert calculation results from the processing unit120 into output signals for transfer to other parts of the vehicle control system and/or the component (s) for which the 14 signals are intended. Each and every one of the connections tothe devices for receiving and transmitting respective inputand output signals can consist of one or more of a cable; adata bus, such as a CAN bus (Controller Area Network bus), aMOST bus (Media Oriented Systems Transport) or any other bus configuration, or of a wireless connection.

Returning to the exemplary method 200 illustrated in Fig. 2,the method starts in step 201. As was mentioned above, thepresent invention relates to a method and system where theinfluence of the clutch pedal (or other suitable means formanoeuvring the clutch) on the clutch is arranged to differaccording to at least one force forming part of the current driving resistance of the vehicle 100.

According to the present example, the influence of the clutchpedal is arranged to depend on the magnitude of the drivingresistance. In step 201, it is determined whether thecharacteristic of the clutch pedal 118 is to be controlledaccording to the current driving resistance. The methodremains in step 201 for as long as this is not the case, andcontinues to step 202 when the clutch pedal characteristic isto be controlled on the basis of the current driving resistance.

The transition from step 201 to step 202 can, for example, beperformed each time the vehicle 100 is set in motion, or isabout to be set in motion from standstill, such as e.g. when amovement of the clutch pedal in a clutch closing direction isdetected. The transition from step 201 to step 202 can also bearranged to take place when the vehicle 100 is in motion and aclutch pedal movement is detected and/or when being manoeuvredthrough the use of a partially open clutch, i.e. when theclutch is slipping.

According to one embodiment, the method according to thepresent invention is carried out each time a movement of theclutch pedal is detected, and according to one embodiment eachtime a movement of the clutch pedal is detected whilesimultaneously the vehicle speed is below some suitable speed limit, such as e.g. 30 km/h.

In step 202 the current driving resistance of the vehicle 100is determined. As was mentioned above, the driving resistancerepresents the combination forces that must be overcome inorder to accelerate the vehicle. The driving resistance isoften estimated by one or more vehicle functions, and istherefore often already available on the vehicle communicationbus system, and hence can be established in a straightforwardmanner. Alternatively the driving resistance of the vehiclecan be arranged to be determined by, or on demand of, thecontrol unit in which the present invention is implemented.The driving resistance can be estimated in any suitablemanner, and plural examples of estimating the drivingresistance can be found in the prior art. For example, the driving resistance can be estimated as: F Drive _ res I FAirRes +FR0llRes +FGrav Where: FQmw represents the air resistance, fkmms represents the rolling resistance, and F Grav represents the force resulting from the influence of gravity.

These forces can be estimated in any known conventionalmanner. Further forces may also be included in the model, suchas e.g. powertrain friction losses. Such losses can also be arranged to be included e.g. as part of the rolling 16 resistance. The respective influences of the various forcesare highly dependent on the current driving conditions, andtherefore, according to one embodiment, only one or two forcesneed to be considered. For example, when the vehicle 100performs a start from standstill the air resistance will benegligible due to its high vehicle speed dependency.Similarly, the force resulting from the influence of gravity is highly dependent on road inclination as well as vehicle mass, and can be neglected, e.g., on level ground.

As was mentioned above, the estimation of the drivingresistance and forces forming part of the driving resistanceis highly straightforward, and therefore not explained further in detail herein.

In step 203 a clutch pedal 118 characteristic for use isdetermined based on the determined driving resistance. Fig. 3illustrates an example of a characteristic Pdmrlfor anexemplary clutch of a kind that can be used in a vehicle ofFig. 1A. The y-axis denotes the transmittable torque, i.e. thetorque that the clutch 106 can transmit between combustionengine 101 and further powertrain components, such as drivewheels, downstream the clutch. In general, with regard toclutch characteristics, the x-axis denotes clutch position,which can be determined in any suitable manner, and, forexample, be represented by the clutch actuator position and/orthe lever arm position. Clutch characteristics are, ingeneral, stored in the vehicle control system, e.g. for usewhen the clutch is automatically controlled by the vehiclecontrol system, e.g. in automatic manual transmissions (AMT),so that, for example, smooth gear changes and/or starts of the vehicle can be obtained. 17 Furthermore, clutch characteristics are often subject tochanges as the clutch wears, and/or due to changes intemperature, which might render the vehicle control system toperform adaptions of the clutch characteristic when found suitable. Such adaptions are well described in the prior art.

According to the present example, however, the x-axis does notrepresent actual clutch position, but according to the presentexample, instead, the graph is used to disclose transmittabletorque as a function of the clutch pedal 118 position. Theorigin, “O”, represents the clutch open position, i.e. aposition where the clutch pedal 118, and usually frictionelement (the lever arm/the clutch actuator) is at its oneextreme position, position B in Fig. 1C. This oftentimescorresponds to a fully depressed clutch pedal 118, and thefriction element 110 being completely disconnected from thecombustion engine 101, i.e. being positioned to the right asin Fig. 1A. Conversely, the “closed clutch” positionrepresents a fully released clutch pedal. That is, position Ain Fig. 1C, and the friction element 110 being as close to theflywheel as possible and thereby pressed against the flywheel,for example by the aid of a spring action. The lever arm canbe used to pull out the friction element by applying a forceto the friction element when opening the clutch. Tmflrepresents the maximum torque that can be transmitted by meansof the present combination of clutch and combustion engine,which in general is limited by the maximum torque that thecombustion engine 101 can deliver. According to the figure,the distance A-B consequently represents the movement region A-B in fig. 1C of the clutch pedal.

The friction element 110, when the clutch is fully open, isnormally at a distance from the engine's flywheel so that closing of the clutch involves the friction element, and hence 18 the clutch pedal, initially moving a distance x1 beforeactually contacting the flywheel. Once the friction elementprecisely contacts the flywheel, at the contact point CP,torque transfer between the engine and rest of the powertraincan commence. The more the clutch closes from this point (i.e.the more strongly the friction element 110 engages theflywheel 102), the more torque can be transmitted over the clutch.

The exact amount of torque that can be transmitted at eachfriction element position depends on the clutchcharacteristic, i.e. the relation between transmittable torqueand friction element position. This relation might resemblethe relation Pdmn shown in Fig. 3, and may vary from clutch toclutch and which, as mentioned, needs to be estimated (adapted) at regular intervals.

As was mentioned, in the present example, the x-axisrepresents the clutch pedal position and not clutch positionand the characteristic Pdmn hence being a clutch pedalcharacteristic, i.e. transmittable torque as a function of the clutch pedal 118 position.

Fig. 3 further discloses a clutch pedal position Åf that drive _ resl corresponds to a transmittable torque Y; that must be rive _ resl transmitted in order to meet the driving resistance according to a first exemplary driving resistance [Q As was ríve resl °explained above, the driving resistance may vary substantiallyfrom one situation to another, e.g. in dependence of whetherthe vehicle 100 is heavily loaded or not, and whether thevehicle 100 is on level ground or in an uphill section ofroad. Consequently the clutch pedal 118 position at which thetransmittable torque corresponds to the torque required to overcome the driving resistance will vary from one situation 19 to another. This means that the clutch will behave quitedifferently from one situation to another, since e.g. theclutch pedal movement that is required from a fully openclutch until the vehicle starts moving, i.e. until thetransmittable torque corresponds to a drive wheel force thatis equal to or overcomes the current driving resistance of thevehicle may differ substantially from one situation to anothersince the difference in driving resistance may be considerable.

This is also exemplified in Fig 3. Apart from the first exemplary driving resistance P2 rive _ res1 f corresponding to the required transmittable torque Y; ríve_ res1 f fig. 3 also discloses the situation for a second exemplary driving resistance IQ ríve_ res 2 °According to this second example, the driving resistance corresponds to a required transmittable torque Y; drive_ res 2 ríve_ res 2 f which is achieved at a clutch pedal position Å; ríve_ res 2 ° Consequently, the required transmittable torques in the fig. 3examples differs from each other, and this is also the casefor the clutch pedal motion that is required to set the vehicle in motion. When the required transmittable torque is T dríve_ res1 f the clutch pedal 118 must be moved a portion AX' of drive _ res1 the total movement region A-B of the clutch pedal 118.

Similarly, when the required transmittable torque is 7; ríve_ res 2 f the clutch pedal 118 must be moved a portion AX; of the rive _ res 2 total movement region A-B of the clutch pedal 118.

As can be seen from the figure, larger clutch pedal motions are in general required for higher transmittable torques, T drive_ res1 > T dríve_ res 2 f than for comparatively lower transmittable torques. The bigger the difference is, i.e. the bigger the difference between the vehicle driving resistance IQ in different situations, the bigger the difference in clutch pedal movement.

This means that the vehicle 100 behaviour when the clutchpedal 118 is being manoeuvred may be quite different fordifferent driving resistances, e.g. when setting the vehiclein motion from standstill. Differences of this kind can bemitigated or eliminated through the use of the present invention.

When the clutch 106 is controlled by the vehicle controlsystem the clutch pedal characteristic can, in principle, beset to any desirable characteristic, since the actual positionof the clutch is controlled independently from the actualpedal position. This is utilised by the present invention andin step 203 the clutch pedal characteristic is set to acharacteristic that is determined on the basis of thedetermined driving resistance. According to the presentexample, the clutch pedal characteristic is set to a characteristic where the transmittable torque at a position .X MW,m, shown in fig. 3, is set to correspond to the prevailingvehicle driving resistance, i.e. a transmittable torque thatgives rise to a propelling force on the vehicle drive wheels that corresponds to the current driving resistance.

Consequently, according to the invention, the clutch pedal characteristic can be controlled such that a single particular position Å; ÜWJÜ in the clutch pedal movement region A-B isarranged to e.g. always correspond to the clutch pedalposition where the transmittable torque results in a probetelling force precisely at or about which the vehicle will be set in motion. l0 2l This is exemplified in Figs. 4A-B. Fig. 4A discloses the example of fig. 3 where a transmittable torque Ä, is rive res1required to meet the current driving resistance. According tothis example, the clutch pedal characteristic is adapted instep 203 such that the clutch pedal characteristic Pdmn offig. 3, shown with dashed line in fig. 4A, is displaced in thedirection according to the arrows 402 in fig. 4A, therebyforming a characteristic Pdmfl. In this way, the characteristic is changed so that the transmittable torque will equal the torque Ä, instead of at the position ríve_ res1 at the position Å; rive _ res sX drive _ res1 ° Hence, according to fig. 4A, the transmittable torque is increased at the clutch pedal position ÅQ rive _ res in comparison to fig. 3.

Similarly, fig. 4B discloses the example of fig. 3 where a transmittable torque 7; måæü is required to meet the currentdriving resistance. In this situation, the clutch pedalcharacteristic is adapted in step 203 such that the clutchpedal characteristic Pdmfl of fig. 3 is, instead, displaced inthe direction according to the arrows 404 in fig. 4B, i.e.opposite the direction of displacement in fig. 4A. In this way, the characteristic is, instead, changed to a characteristic P@m¿;where the transmittable torque will equal the torque 7; instead of at the rive _ res 2 at the position Å; rive _ res position Å; ríve_ res 2 ° Hence, according to fig. 4B, the transmittable torque is decreased at the clutch pedal position sX drive_ res in comparison to fig. 3.

The disclosed method can, for example, be arranged todetermine a clutch pedal characteristic that always results ina transmittable torque resulting in a propelling force on the vehicle drive wheels equalling the vehicle driving resistance lO 22 at the clutch pedal position Å; flæjm. Furthermore, according tothe disclosed example, the clutch pedal characteristics Pdmflhave been displaced in a direction parallel to the Pos-axis ofthe figure. According to one embodiment, the clutch pedalcharacteristics are instead displaced in parallel to the T-axis, i.e. “raised” or “lowered” in the figure such that thetransmittable torque fulfils the criteria according to theabove. According to one embodiment, it is only ensured thatthe transmittable torque equals the desired transmittabletorque at the desired position, while the remainder of theclutch pedal characteristic can be adapted in any suitablemanner. For example, the characteristic may be adapted suchthat the slope (changes in transmittable torque per unitdistance movement of the clutch pedal) becomes suitable e.g. towards fully opened and fully closed positions.

Consequently, according to the present invention, the driver will always be aware of the clutch pedal position Å; that rive _ res corresponds to the current driving resistance IQ i.e. the rive _ res fposition where there is an equilibrium of the forces acting onthe vehicle. Hence the driver will also be aware of the clutchpedal position where the vehicle will be set in motion (from standstill) or begin to accelerate, since a movement from the clutch pedal position Å; rive _ res will change the transmittabletorque, and at least an increase in transmittable torque from clutch pedal position Å; will set the vehicle in motion. rive _ res According to the above example, the transmittable torquecorresponding to the vehicle driving resistance is controlled to always be obtained at a particular clutch pedal position, .X drive_ res ° According to one embodiment of the present invention, the control is only utilized e.g. when the driving resistance 23 is below some suitable value and/or above some suitable value.For example, it may not always be desired that the inventionis utilized when the driving resistance is very high or verylow. At least not if this may result in clutch pedalcharacteristics where the remaining available portion of themovement region for controlling torques above and/or below thetorque corresponding to the driving resistance may be too small to ensure satisfactory control of the clutch.

Furthermore, according to one embodiment of the invention, a single position Å; fiæjm according to the above is not used, butinstead, the clutch is controlled such that the transmittabletorque corresponding to the vehicle driving resistance insteadis controlled to be within a particular portion of themovement region A-B. For example, this portion may vehicle e.g. 2%, 5% or 10% of the total movement region of the clutch pedal 118, e.g. centered about the position Å; In this way, the clutch pedal may still behave from a driver point ofview substantially as if the same position always results in atransmittable torque meeting the vehicle driving resistance,while the vehicle control system more easy may find a clutchpedal characteristic that fulfils set criteria. This is exemplified by the portion AX> of fig. 4B. drive _ res The clutch 106 can be arranged to be controlled according tothe determined clutch pedal characteristic, e.g. Pdwrg orPdmß, step 204, e.g. for as long as the clutch is slipping,and the method can be ended e.g. when the clutch has beencompletely closed, or completely opened, determined in step205. The method is then ended in step 206. Alternatively themethod can be arranged to continuously return to step 201 from step 204 in order to update the clutch pedal characteristic in lO 24 dependence of changes in driving resistance during an ongoing clutch slip.

Furthermore, according to one embodiment of the invention, the position ÅQ in the rive _ res and/or region about a position Å; ríve res fmovement region A-B can be arranged to be driver controlled.That is, the driver may be allowed to, e.g. by means of thevehicle control system, set the clutch pedal position at whichthe driving resistance is to be met irrespective of the actualmagnitude of the driving resistance. In this way, the clutchbehaviour can be adapted individually according to the preferences of different drivers.

Furthermore, the present invention can also be utilised incombination with the invention disclosed in the parallelSwedish patent application SEl55XXXX-X, with the title “METHODAND SYSTEM FOR CONTROLLING A CLUTCH OF A VEHICLE II", andhaving the same inventors and the same filing date as thepresent invention. According to the invention disclosed inthis parallel application, the clutch is also controlled independence of the position of the drivel manoeuvrable meanssuch as e.g. a clutch pedal in the movement region A-B. Inparticular, a control is used where the characteristic of theclutch pedal can be adapted such that e.g. changes intransmittable torque as function of clutch pedal movement canbe reduced when moving the clutch pedal in a region about theposition at which the transmittable torque equals, or substantially equals, e.g. the current driving resistance.

When used in combination with the present invention, aparticular clutch pedal position, or at least one position ina portion of the clutch pedal movement region, will alwayscorrespond to the current driving resistance. In addition, the clutch pedal characteristic about this position is adapted lO according to the above-referenced application such that e.g.changes in transmittable torque about this position/region iscontrolled in a manner that further facilitates clutch operation for the driver.

For example, the change in transmittable torque as a functionof clutch pedal movement about the clutch pedal positioncorresponding to the current driving resistance can bereduced. This is exemplified in fig. 5, which discloses asituation corresponding to the fig. 4B example. In fig. 5 the clutch pedal characteristic Pdmfi has not only been displaced such that transmittable torque at the position Åf drive_ rescorrespond to the current driving resistance. In addition, thetransmittable torque is further controlled such that thederivative of the clutch pedal characteristic about the positionÅf is reduced in a portion of the movement region drive_ res A-B about the clutch pedal position Åf The corresponding drive_ res °fig. 3 characteristic Pdmfl is shown by dashed line. The changein transmittable torque can be controlled such that the changein transmittable torque for a first movement of said driver manoeuvrable means about said first portion of said movement region A-B and/or the position Åf is controlled to be below drive_ res some suitable change in transmittable torque.

Consequently, when combining the present invention with thesolution disclosed in the above-referenced patent applicationa combined solution is obtained which not only enables thedriver to always know where in the clutch pedal movementregion that the transmittable torque will correspond to thecurrent driving resistance. The control of the vehicle willalso be further improved by reducing variations intransmittable torque as a function of the movement about this clutch pedal position. 26 Finally, the present invention has been described above for aparticular example of a vehicle, but is applicable for anyvehicle in which driver manoeuvrable means are used to controla clutch, the clutch being any kind of suitable clutchcomprising any kind of elements, and hence not necessarily aclutch of the kind exemplified above, for as long as themanoeuvring of the clutch can be accomplished independently from the manoeuvring of the driver manoeuvrable means.

Claims (17)

1. 27 Claims ln Method for controlling a clutch of a vehicle (100), thevehicle (100) including a clutch (106) for selectivelytransmitting torque to and/or from a first power source(101), said vehicle (100) further including drivermanoeuvrable means (118) for manoeuvring a clutch (106),said driver manoeuvrable means (118) being movable in amovement region (A-B) between a first end position (A)and a second end position (B), transmittable torque ofsaid clutch (106) being controlled by a vehicle controlsystem on the basis of the position of said drivermanoeuvrable means (118) in said movement region (A-B),the method being characterised in, for a plurality of different magnitudes of at least one force forming at least part of the driving resistance (F' ) of said dríve_ resvehicle (100): - controlling said clutch (106) on the basis of theposition of said driver manoeuvrable means (118) in said movement region (A-B) in dependence of the magnitude of said at least one force (F IMWJW), further including:- controlling said clutch (106) such that transmittable torque of at least one position in a first portion ( AX lwwjm) of said movement region (A-B) of said drivercontrollable means (118) gives rise to a propelling forceon the vehicle drive wheels (113, 114) substantiallycorresponding to the magnitude of said at least one force (F dríve_res ) °

2. Method according to claim 1, further including, whencontrolling said clutch (106):- controlling said clutch (106) on the basis of the position of said driver manoeuvrable means (118) in said lO 28 movement region (A-B) according to a first dependency(Pdmfl) for a first magnitude of said at least one force ( and dra/eyes ) I- controlling said clutch (106) on the basis of theposition of said driver manoeuvrable means (ll8) in saidmovement region (A-B) according to a second dependency(Pdmfl), being different from said first dependency,

3. (Pümfl) for a second magnitude, being different from said first magnitude of said at least one force (F' such dríve_res ) f that according to said dependencies transmittable torque of at least one position in said first portion (AX

4. Drive _ res)of said movement region (A-B) of said drivercontrollable means (ll8) gives rise to a propelling force on the vehicle drive wheels (ll3, ll4) substantially equalling the magnitude of said at least one force (F dríve_ res

5. ) .

6. .Method according to claim 2, said dependency being a representation of the transmittable torque of said clutch(106) as a function of the position of said driver manoeuvrable (ll8) means in said movement region (A-B).

7. .Method according to any one of claims l-3, further including:- controlling said clutch such that said first portion (

8. AX lwæjm) of said movement region (A-B) constitutes aportion corresponding to any of: O-2% of the totalmovement in said movement region (A-B), O-5% of the totalmovement in said movement region (A-B), O-lO% of the total movement in said movement region (A-B).

9. .Method according to any one of the claims l-4, further including:

10. 29 - controlling said clutch (106) such that, for said magnitudes of said at least one force (F dríve_res ) f transmittable torque at substantially a same first position (Åf of said movement region (A-B) of said Drive _ res )driver controllable means (118) gives rise to apropelling force on the vehicle drive wheels (113, 114)substantially equalling the magnitude of said at least one force (F dríve_res ) ° .Method according to any one of the claims 1-5 further including: - controlling said clutch (106) according to any one ofthe claims 1-5 when a positive propelling force on saiddrive wheels is required to set the vehicle in motion in an intended direction of travel. .Method according to any one of the claims 1-6, further including:- controlling said clutch (106) according to any one ofthe claims 1-6 irrespective of the magnitude of said at least one force. .Method according to any one of the claims 1-7, further including:- controlling said clutch according to any one of theclaims 1-7 when the magnitude of said at least one force at most equals a first magnitude. .Method according to any one of the claims 1-8, wherein the location of said first portion of said movementregion (A-B) and/or said first position in said movement region (A-B) is controllable by a driver of the vehicle. Method according to any one of the claims 1-9, wherein said at least one force (F' ) is an estimation of at dríve_ res

11.

12.

13.

14.

15. least one of: rolling resistance, air resistance, force resulting from the influence of gravity. Method according to any one of claims 1-10, wherein said at least one force is an estimation of the driving resistance (F' of said vehicle (100). drive_ res ) Method according to any one of the preceding claims,further including: - reducing variations in transmittable torque of saidclutch (106) as a function of movement of said driver controllable means (118) about said first portion ( AX Drive _ res ) of said movement region (A-B) and/or said first position (Åf in said movement region (A-B). Drive _ res ) Method according to claim 12, further including:- reducing said change in transmittable torque of saidclutch (106) such that the change in transmittable torque for a first movement of said driver manoeuvrable means about said first portion (AX' of said movement Drive _ res ) region (A-B) and/or said first position (Åf in said Drive _ res )movement region (A-B) is controlled to be below a first change in transmittable torque. Computer program comprising program code that, when saidprogram code is executed in a computer, causes saidcomputer to carry out the method according to any of claims 1-13. Computer program product comprising a computer-readablemedium and a computer program according to claim 14,wherein said computer program is contained in said computer-readable medium. 31

16.System for controlling a clutch of a vehicle (100), the

17. vehicle (100) including a clutch (106) for selectivelytransmitting torque to and/or from a first power source(101), said vehicle (100) further including drivermanoeuvrable means (118) for manoeuvring a clutch (106),said driver manoeuvrable means (118) being movable in amovement region (A-B) between a first end position (A)and a second end position (B), transmittable torque ofsaid clutch (106) being controlled by a vehicle controlsystem on the basis of the position of said drivermanoeuvrable means (118) in said movement region (A-B),the system being characterised in means for, for a plurality of different magnitudes of at least one force forming at least part of the driving resistance (F drivejes )of said vehicle (100): - controlling said clutch (106) on the basis of theposition of said driver manoeuvrable means (118) in said movement region (A-B) in dependence of the magnitude if said at least one force (F' and dríve_res ) ;- controlling said clutch (106) such that transmittabletorque of at least one position in a first portion ( AX Drive _ res ) of said movement region (A-B) of said driver controllable means (118) gives rise to a propelling forceon the vehicle drive wheels (113, 114) substantially corresponding to the magnitude of said at least one force ( dríve_res ) ° Vehicle, characterised in that it comprises a system according to claim 16.