SE1550123A1 - Method and system for controlling a clutch of a vehicle - Google Patents

Abstract

Abstract The present invention relates to a method for controlling a clutch of a vehicle, the vehicle including a clutch (106) for selectively transmitting torque to and/or from a first power source (101), said vehicle further including driver manoeuvrable means (118), such as a clutch pedal, for manoeuvring a clutch (106), said driver manoeuvrable means (118) being movable in a movement region (A-B) between a first end position (A) and a second end position (B), opening and closing of said clutch (106) being controlled by a vehicle control system on the basis of the position of said driver manoeuvrable means (118) in said movement region(A-B). The method includes, when detecting a to and fro motion of said driver manoeuvrable means (118): - determining whether said to and fro motion at least partially depends on a motion of said vehicle (100), and - when it is determined that said to and fro motion at least partially depends on a motion of said vehicle (100), at least partially disregarding said to and fro motion when controlling said clutch (106). Fig. 2

Description

Abstract The present invention relates to a method for controlling a clutch of a vehicle, the vehicle including a clutch (106) for selectively transmitting torque to and/or from a first power source (101), said vehicle further including driver manoeuvrable means (118), such as a clutch pedal, for manoeuvring a clutch (106), said driver manoeuvrable means (118) being movable in a movement region (A-B) between a first end position (A) and a second end position (B), opening and closing of said clutch (106) being controlled by a vehicle control system on the basis of the position of said driver manoeuvrable means (118) in said movement region(A-B). The method includes, when detecting a to and fro motion of said driver manoeuvrable means (118): - determining whether said to and fro motion at least partially depends on a motion of said vehicle (100), and - when it is determined that said to and fro motion at least partially depends on a motion of said vehicle (100), at least partially disregarding said to and fro motion when controlling said clutch (106).

Fig. 2 1 METHOD AND SYSTEM FOR CONTROLLING A CLUTCH OF A VEHICLE Field of the invention The present invention relates to vehicles, and in particular to a method and system for controlling a clutch of a vehicle.

The present invention also relates to a vehicle, as well as a computer program and a computer program product that implement the method according to the invention.

Background of the invention There exist various kinds of vehicle powertrains. For example, vehicle transmissions can be of a fully automatic kind, where a vehicle control system controls completely gear shifting operations. The gearboxes being used in these systems can, for example, consist of conventional automatic transmissions, but can also consist of automated manual transmissions where the vehicle control system automatically controls gear shifting in "manual" gearboxes. There also exist manual transmissions where the vehicle driver is in control of the gear shifting operation. Gear shifting in manual transmissions is often performed by the use of a driver controllable clutch, oftentimes through the use of a clutch pedal, which is used to disengage the powertrain during the change of gear and when starting/stopping the vehicle.

A clutch can also be used in automated manual transmissions, in which case clutch operation is controlled by the vehicle control system and not by the driver. In principle, the clutch pedal need not be present in systems of this kind. However, in some systems having automated manual transmissions, driver controllable means such as a clutch pedal is still present and used e.g. when starting the vehicle from standstill. For example, the clutch can be used to set the vehicle in motion in precisely the preferred manner according to the driver. 2 When the vehicle has been set in motion, use of the clutch in subsequent gear changes can be controlled completely by the vehicle control system without driver interaction. There also exist systems where the clutch is used solely by the driver, and where gear change performed by the vehicle control system is carried out without the use of the clutch. Consequently, e.g. a clutch pedal can be used both in vehicles having manual transmissions and also in vehicles having at least some kinds of automatic transmissions.

There exist situations, however, in particular when starting a vehicle from standstill or when manoeuvring at low vehicle speeds, where an unfavourable course of action with regard to the vehicle start may occur as a result of the driver operation of the clutch.

Summary of the invention It is an object of the present invention to provide a method and system that facilitates clutch operation in particular when starting a vehicle from standstill and in situations when operating the clutch at low vehicle speeds. This object is achieved by a method according to claim 1.

According to the present invention, it is provided a method for controlling a clutch of a vehicle, the vehicle including a clutch for selectively transmitting torque to and/or from a first power source, said vehicle further including driver manoeuvrable means for manoeuvring said clutch, said driver manoeuvrable means being movable in a movement region between a first end position and a second end position, where opening and closing of said clutch is controlled by a vehicle control system on the basis of the position of said driver manoeuvrable means in said movement region. The method includes, when detecting a to and fro motion of said driver 3 manoeuvrable means: determining whether said to and fro motion at least partially depends on a motion of said vehicle, and when it is determined that said to and fro motion at least partially depends on a motion of said vehicle, at least partially disregarding said to and fro motion when controlling said clutch. The driver manoeuvrable means can, for example, be a clutch pedal.

As mentioned above there exists various kinds of vehicle powertrains, where sometimes a clutch is used, and sometimes not. The present invention relates to powertrains where a clutch is used, and in particular to powertrains having a driver controllable clutch. Oftentimes the operation of the clutch, such as, for example, the manoeuvring of a clutch friction element, and hence the magnitude of the transmittable torque over the clutch, is controlled by driver manoeuvrable means such as a clutch pedal that is mechanically linked to the clutch movable elements. This means that the clutch operation always is essentially the same, subject to wear etc.

The present invention, however, relates to systems where the driver manoeuvrable means is not used to control the clutch directly through the use of a mechanical linkage, but, instead, clutch-by-wire systems. In clutch-by-wire systems an electrical signal representing e.g. a clutch pedal position is translated into a corresponding clutch movement. For example, a position sensor or other suitable means can be used to detect a position of the driver manoeuvrable means, such as e.g. the position of a clutch pedal. An electrical signal representing this position is then translated into a corresponding driver request regarding clutch operation, and the vehicle control system then controls the actual clutch movement on the basis of the signal representing the position 4 of the clutch pedal. The actual clutch movement, consequently, is not mechanically linked to movements of the driver manoeuvrable means.

In general, from a driver perspective, a clutch-by-wire system behaves in a manner similar to systems having a mechanical linkage according to the above, but clutches of this kind can also be controlled fully automatically by the vehicle control system, e.g. in automated manual transmissions (AMT). Further, clutches may be of various designs, and the particular design, e.g. whether the clutch is a friction clutch or not, is not of relevance to the present invention. The invention is applicable in any clutch-by-wire system.

The use of a driver manoeuvrable clutch, however, may, in some situations, result in undesired and unintended vehicle behaviour. For example, if the vehicle encounters an irregularity, such as a hole or an elevation in the surface upon which the vehicle is travelling or being set in motion from standstill when the clutch is closing, the irregularity may cause an impact on the acceleration of the vehicle that results in a rocking motion. This, in turn, may translate into an unintended and unfavourable manoeuvring of the driver manoeuvrable means, which may exhibit a to and fro movement, e.g. a backwards and forwards motion, that alternately increases and decreases the transmittable torque of the clutch. This may have the result that, due to a resonant behaviour, the vehicle start, or already ongoing motion, becomes so uncontrolled by the changes in transmittable, and thereby transmitted torque by the clutch, that the vehicle e.g. must be stopped completely and the vehicle be started from standstill once again. Further, situations of this kind do not arise only due to irregularities according to the above, but can, for example, arise also e.g. when starting heavily loaded truck-trailer combinations, heavily loaded vehicles in general and in particular when starting a vehicle in an uphill slope. Also, the situation may arise when travelling on bumpy roads and/or in rough terrain.

According to the present invention, situations of this kind are identified and actions being taken to alleviate the behaviour such that the vehicle is started in a controlled manner. According to the present invention, this is accomplished through the use of a method in which, when detecting a to and fro motion of said driver manoeuvrable means, it is determined whether the to and fro motion at least partially depends on a motion of said vehicle. When this is the case, the detected to and fro motion is at least partially disregarded by the vehicle control system when controlling said clutch. In this way an undesired motion of the vehicle, such as a rocking motion, will not be amplified, or worsened, by changes in drive wheel torque caused by opening and closing of the clutch due to the to and fro motion that, in turn, is caused by the rocking of the vehicle.

Further, apart from the advantage in providing increased possibilities with regard to controlling the clutch, clutchby-wire systems may allow further advantages with regard to driver experience. For example, clutch pedals often have a certain stroke length which e.g. can depend on the mechanical design of the clutch system. This means that the clutch pedal stroke length may necessarily need to have a stroke length of a certain magnitude in order to provide the desired clutch operation. Furthermore, the force being required to depress the clutch pedal may, again due to the mechanical design, also be a force of a system defined and relatively high magnitude.

However, both stroke length and magnitude of the force being required to depress the clutch pedal oftentimes differ from 6 driver preferences should the driver be able to freely choose the characteristics of the clutch pedal.

For example, it might be desirable to have a clutch pedal that can be manoeuvred using less force. It might also be desirable to have a pedal having a shorter stroke length. It is possible to realize such clutch pedals in clutch-by-wire systems of the above described kind, since only a clutch pedal position is required in order to appropriately control the torque.

However, the use of clutch pedals having shorter stroke length, and/or where less force is necessary to operate the clutch, may increase further the risk for undesired scenarios according to the above when starting the vehicle. The present invention alleviates the possible negative effects that can be introduced by such "driver friendly" clutch pedals by filtering out clutch motions that may be occurring more frequent e.g. when using clutch pedals having shorter stroke length or where less force is required for operation.

The undesired vehicle motion according to the above occurs, in general, when starting from standstill or when operating the clutch at low vehicle speeds, and according to one embodiment, the present invention is utilized for vehicle speeds being lower than a first speed e.g. 30 km/h, 10 km/h, 5 km/h or 2 km/h, and the invention can be arranged to be used only for vehicle speeds below a suitable speed in any of the stated ranges. The invention is equally applicable irrespective of whether the vehicle is moving backwards or forwards.

The driver controllable means for controlling a clutch is in general movable in a movement region between a first end position and a second end position, where the opening/closing of the clutch is dependent on the position of said driver controllable means. The to and fro motion can be determined by 7 determining a to and fro motion of said driver controllable means in said movement region, e.g. by the use of a suitable sensor.

Further characteristics of the present invention and advantages thereof are indicated in the detailed description of exemplary embodiments set out below and the attached drawings.

Brief description of the drawings Fig. 1A illustrates a powertrain of an exemplary vehicle; Fig. 1B illustrates an example of a control unit in a vehicle control system; Fig. 1C illustrates a clutch pedal of the exemplary vehicle of Fig. 1A.

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

Fig. 3A-D illustrates a situation where the present invention can be utilised.

Fig. 4A-D illustrates the situation of fig. 3A-D when the present invention is utilised.

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 for any kind of driver controllable means for controlling a clutch where a to and fro motion may arise due to motions in the vehicle.

Fig. 1A schematically depicts a powertrain of an exemplary vehicle 100. The powertrain comprises a power source, in the present example a combustion engine 101, which, in a 8 conventional manner, is connected via an output shaft of the combustion engine 101, normally via a flywheel 102, to a gearbox 103 via a clutch 106. An output shaft 107 from the gearbox 103 propels drive wheels 113, 114 via a final drive 108, such as a common differential, and drive axles 104, 10 connected to said final drive 108.

The combustion engine 101 is controlled by the vehicle control system via a control unit 117. The clutch 106 and gearbox 103 are also controlled by the vehicle control system by means of a control unit 116. According to the present example, the clutch consists of a dry clutch where a friction element (disc) 110 is connected to, and rotates with, a first gearbox element, e.g. an input shaft 109 of the gearbox 103. The friction element 110 selectively engages the flywheel 102, or any 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 components downstream 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 engine flywheel 102 is controlled by means of a pressure plate 111 by means 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 be mechanically linked to the lever arm 112 in order to directly control movement of the friction element 110. It is to be understood, however, that the exemplified clutch is merely an example, and that clutches, irrespective of whether the clutch constitutes part of a clutch-by-wire system or is controlled mechanically by driver controllable means, may be of various 9 designs. For example, the clutch actuator may be arranged coaxially with the gearbox input shaft 109.

According to the disclosed system, opening and closing of the clutch 106 is still controlled by the driver using a clutch pedal 118, however with the difference that the influence of the clutch actuator 115 on the lever arm 112 is controlled 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 longer mechanically linked to the clutch pedal 118. This means, in turn, that the clutch pedal 118 position, instead, is used as a request for a particular clutch operation, which is then, by means of the vehicle control system, translated into an actual clutch movement via the clutch actuator 115. Still, the positioning 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 is 118 movable within a movement region defined by two end positions A, B, in the present example defining an angular range a. The clutch pedal 118 position in said movement region can be determined, e.g. by means of a suitable sensor, such as, for example, an angle sensor 119 or any other suitable kind of sensor which determines the current position of the clutch pedal 118 in the movement region in which the clutch pedal is movable.

According to the present invention, motions of the clutch pedal that are detriment to the propulsion of the vehicle, and which in general are not intentional, are detected and disregarded when the control commands given by the driver by means of the clutch pedal are translated into actual clutch movement. An exemplary method 200 of the present invention is 10 shown in fig. 2, which method can be implemented at least partly e.g. in the control unit 116 for controlling the clutch 106 and gearbox 103. As indicated above, the functions of a vehicle are, in general, controlled by a number of control units, and control systems in vehicles of the disclosed kind generally comprise a communication bus system consisting of one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a 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 units 116-117, but vehicles 100 of the illustrated kind are often provided with significantly more control units, as one skilled in the art will appreciate. Control units 116-117 are arranged to communicate with one another and various components via said communication bus system and other wiring, partly indicated by interconnecting lines in fig. 1A.

The present invention can be implemented in any suitable control unit in the vehicle and hence not necessarily in the control unit 116. The control of the clutch 106 according to the present invention will usually depend on signals being received from other control units and/or vehicle components, and it is generally the case that control units of the disclosed type are normally adapted to receive sensor signals from various parts of the vehicle 100. The control unit 116 will, for example, receive signals from clutch pedal position sensor 119 and clutch actuator 115. Further, the control unit will receive signals representing a vehicle motion, or signals from which a vehicle motion, such as e.g. a rocking motion, can be determined. This vehicle motion can, for example, be determined using sensors of the vehicle suspension system, a 11 gyro, an accelerometer or any other suitable means. Control units of the illustrated type are also usually adapted to deliver control signals to various parts and components of the vehicle, e.g. to control the clutch actuator 115.

Control of this kind is often accomplished by programmed instructions. The programmed instructions typically consist of a computer program which, when executed in a computer or control unit, causes the computer/control unit to exercise the desired control, such as method steps according to the present invention. The computer program usually constitutes a part of a computer program product, wherein said computer program product 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 manner on said storage medium. The digital storage medium 121 can, for example, consist of any of the group comprising: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit etc, and be arranged in or in connection with the control unit, whereupon the computer program is executed by the control unit. The behaviour of the vehicle 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 shown schematically in Fig. 1B, wherein the control unit can comprise a processing unit 120, which can consist of, for example, any suitable type of processor or microcomputer, such as a circuit for digital signal processing (Digital Signal Processor, DSP) or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The processing unit 120 is connected to a memory unit 121, which provides the processing unit 120, with e.g. the stored program 12 code 126 and/or the stored data that the processing unit 120 requires to be able to perform calculations. The processing unit 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 devices 122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals can comprise waveforms, pulses or other attributes that the devices 122, 125 for receiving input signals can detect as information for processing by the processing unit 120. The devices 123, 124 for transmitting output signals are arranged so as to convert calculation results from the processing unit 120 into output signals for transfer to other parts of the vehicle control system and/or the component (s) for which the signals are intended. Each and every one of the connections to the devices for receiving and transmitting respective input and output signals can consist of one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST 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, where it is determined whether there is an ongoing clutch pedal movement. This can, for example, be determined by determining whether there is a movement indicated by the position sensor 119. For example, it can be determined whether there is a clutch movement exceeding some suitable portion of the movement region of the clutch pedal.

According to one embodiment, it is determined not only whether there is a movement in the clutch pedal, but also whether there is movement in a direction from the clutch-open position (at least partially depressed clutch pedal) towards clutch- 13 closed position, that is, it is determined whether the driver is about to at least partially close the clutch. Oftentimes problems of the kind addressed by the present invention arise from situations starting by a closing of the clutch where the transmittable, and thereby usually the transmitted, torque increases. That is, in situations when increasingly more power is applied to the vehicle drive wheels, such as e.g. when the vehicle starts from standstill. However, as was mentioned, according to one embodiment it is only determined whether there is a clutch pedal movement. For as long as there is no clutch pedal movement that triggers the present invention, the method remains in step 201. When it is determined that there is a movement of the clutch pedal triggering the method according to the invention, the method continues to step 202.

The transition from step 201 to step 202 can also be arranged to depend on further criteria. For example, the vehicle speed Vvehide can be determined, and the transition from step 201 to step 202 be arranged to be carried out only if the vehicle speed Vvehjcle is below the speed limit viim. The speed limit viim can be any suitable speed limit, e.g. in the any of the ranges 0-30 km/h, 0-10 km/h, 0-5 km/h or 0-2 km/h. According to one embodiment, the method can be performed for any vehicle speed. The vehicle behaviour being compensated for according to the present invention oftentimes occurs when the vehicle is travelling at low speeds, or when the vehicle speed is increased from substantially zero. Therefore, according to one embodiment, the transition from step 201 to step 202 is carried out when a clutch pedal movement initiated at vehicle standstill is detected.

In step 202 it is determined whether there is a to and fro motion of the clutch pedal, i.e. whether the clutch pedal 14 moving backwards and forwards, or vice versa, in the movement region. A to and fro movement of the clutch pedal will result in corresponding variations in transmittable torque over the clutch which may result in corresponding variations in applied torque on the vehicle drive wheels 113, 114, i.e. the applied torque will alternately increase/decrease. As was mentioned above, scenarios of this kind may result in a vehicle behaviour that cannot be controlled without opening the clutch in order to stop the vehicle. An example of a situation of this kind is illustrated in figs. 3 A-D.

Fig. 3A illustrates the clutch pedal position as a function of time t. In the figure, the clutch pedal position varies between arbitrary pedal positions, and hence not necessarily between a fully released and a fully depressed clutch pedal.

The position "A" on the y-axis represents a position were less torque is transmittable over the clutch, i.e. a more depressed clutch pedal, in relation to the position "B", which represents a position where more torque can be transmitted, i.e. a more released clutch pedal 118. Figs. 3A-D illustrates a situation e.g. during a vehicle start, where at time t1 the driver is closing the clutch by relatively slowly releasing the clutch pedal in a conventional manner. This is illustrated in fig. 3A. This results in an increase in transmittable torque of the clutch. This is illustrated in FIG. 3B, which shows changes in clutch engagement corresponding to the changes in pedal position of FIG. 3A. The y-axis represents transmittable torque, where the "0"-level represents less transmittable torque, while the level "C" represents a more closed clutch, where a larger amount of torque can be transmitted by the clutch.

Fig. 3C illustrates the corresponding changes in drive wheel torque Tdriv„ i.e. the torque that is transmitted from the combustion engine via the clutch, gearbox etc. to the vehicle drive wheels 113, 114, which varies with the transmittable torque of the clutch. The drive wheel torque, in turn, results in a vehicle acceleration, see fig 3D. In fig. 3D, the zero level represents no acceleration, while a positive acceleration increases the vehicle speed and a negative acceleration decelerates the vehicle and hence reduces the vehicle speed.

At time t2 the clutch pedal has been manoeuvred to position B, with the result that a powertrain torque TD is transmitted over the clutch. The applied drive wheel torque, in turn, results in a vehicle acceleration, see fig. 3D.

If the vehicle start would succeed in an expected manner, the clutch could, for example, be closed substantially according to the dash/dotted line 301, with continued applied and usually increased torque, e.g. due to the driver depressing an accelerator, and the vehicle continuously accelerating to the desired speed. Alternatively, the driver may not be performing a vehicle start from standstill, but can, for example, be manoeuvring the vehicle using a slipping clutch.

According to the present example, the expected manoeuvring of the vehicle is disturbed by an irregularity such as e.g. a hole or elevation in the surface upon which the vehicle is present when set in motion. Vehicles, and heavy vehicles in particular, are often well suspended in order to account for irregularities in the surface upon which the vehicle is travelling. For example, heavy vehicles oftentimes are provided with a cab where the driver is seated, where the cab is suspended in relation to the vehicle chassis.

Furthermore, again in particular with regard to heavy vehicles, the driver's seat is often equipped with a 16 suspension system of its own to further reduce the impact of irregularities in the road as experienced by the driver. When the vehicle encounters an irregularity in the road, this can have an impact on the vehicle acceleration, in particular a decelerating effect, which, at least partly due to the vehicle suspension system, may give rise to a vehicle rocking motion. This rocking motion may transplant into a corresponding motion of the cab and/or driver's seat. When the cab and/or driver's seat is suspended in the relation to the vehicle chassis, the motion of the driver's seat will, due to the nature of suspension systems be delayed with respect to the motion of the vehicle chassis, and hence be out of phase with the motion of the vehicle.

This means that when the vehicle chassis is moving upwards the cab/driver's seat may be in a downward motion and hence moving in relation to the vehicle chassis. This, in turn, has the result that the driver foot/leg that operates the clutch pedal may also exhibit a rocking motion in relation to the vehicle chassis that, since the vehicle may be moving "upwards" while the seat is moving "downwards" may give rise to a depressing and releasing of the clutch pedal that is completely unintentional. For example, the driver's seat and thereby the driver's leg can be in a downward motion while simultaneously the vehicle chassis is in an upward motion. The situation may arise also when the driver's seat is not suspended in relation to the cab/chassis. This is because the natural frequency of the driver's leg and clutch pedal oftentimes is similar to, or in the vicinity of, the natural frequency of the vehicle chassis and/or the suspension of the vehicle cab in relation to the vehicle chassis. Because of this, the resonant behaviour may arise irrespective of whether the driver's seat is suspended or not. 17 The undesired motion will result in the clutch pedal again being depressed, exemplified at time t2 in fig. 3A-D, with a following associated decrease in transmittable torque and vehicle acceleration. Conversely, when the vehicle chassis is instead in a downward motion the driver's seat may be in an upward motion, the driver foot thereby releasing the clutch pedal, e.g. as starting from time t3 in fig. 3A, with an increase in transmittable torque over the clutch and vehicle acceleration as result. These accelerations and decelerations will worsen the rocking motion of the vehicle, and the driver's seat, which in turn will further increase oscillating changes in drive wheel torque since the clutch pedal position and hence clutch engagement, and thereby transmittable torque, will exhibit substantially the same oscillating motion. This will oftentimes cause the vehicle to alternately accelerate and decelerate in a manner that amplifies the rocking motion and worsens the course of events.

Situations of the kind shown in figs. 3A-D are therefore oftentimes resonant in its behaviour, and progressing fast.

The vehicle is often uncontrollable within seconds, and the only way of stopping the rocking motion being depressing the clutch pedal to stop the vehicle. This is illustrated in figs 3A-D, where the driver at time 15 is in an 'impossible" situation and fully depresses the clutch pedal to completely open the clutch, possibly by also operating e.g. a brake pedal. The start of the vehicle can then be commenced all over again from vehicle standstill.

According to the present invention, situations of this kind are avoided by a method where the risk for situations of the kind in figs. 3A-D is identified at an early stage and compensated for. 18 This is illustrated in fig. 4A-D, which figures correspond to figs. 3A-D, i.e. fig. 4A shows clutch pedal position, Fig. 4B the presently transmittable torque etc. Figs. 4A-D discloses a vehicle start in a situation being similar to the situation in figs 3A-D. Consequently, from a time t=tA, corresponding to time t1 in fig. 3A-D, there is a closing of the clutch 106 by slowly releasing the clutch pedal 118 in a conventional manner. Similar to Figs. 3A-D, the clutch closes up to point tB at which, due to e.g. an encountered irregularity between time tA and time tB, the driver's seat starts moving out of phase with the vehicle chassis at time tp. The irregularity is represented by the vehicle acceleration in fig. 4D starting to decrease already at time tA,, which due to the delays in the suspension systems causes the driver's seat to start moving out of phase with the vehicle chassis at time tp. This has the result that an opening of the clutch is commenced.

In step 202 it is determined whether there is alternately a clutch opening and a clutch closing motion, respectively, i.e. a to and fro motion of the clutch pedal. This motion can be detected, for example, by analysing signals from the position/angle sensor 119, and when it is determined that there is an ongoing to and fro motion, e.g. at some time after the time tB, such as e.g. at time tc in fig. 4A, or at some other suitable time after the time -LB the method continues to step 203. If no such to and fro motion is detected the method returns to step 201. In step 203 it is determined whether the to and fro motion of the clutch 106 is likely to depend on motions of the vehicle.

The determination in step 203 can be accomplished, for example, by monitoring the vehicle acceleration, where a sudden change either in magnitude of the acceleration or whether the acceleration transitions into deceleration such as 19 between time tB and time tc in fig. 4D. The determination in step 203 can also be performed, for example, by means of some suitable acceleration sensor, a gyro or any other suitable means. For example, it can be determined whether the vehicle is undergoing a first acceleration followed by a second acceleration, where the second acceleration is different from the first acceleration in magnitude and/or direction. Consequently there can be different accelerations in a same direction, or accelerations in different directions, such as upwards/downwards or backwards/forwards.

Further, sensors in the vehicle suspension system can also be used to establish whether there is a rocking motion of the vehicle in relation to the ground upon which it is travelling. The determination in step 203 can also be arranged to compare, for example, the frequency f1 of the to and fro motion of the clutch pedal with the frequency f2 of the vehicle motion. If the frequencies f1, f2 are in a similar range it can be established that the clutch motion is likely dependent on the vehicle motion. According to one embodiment, it is determined whether frequency of the to and fro motion of the clutch pedal is in a first frequency range 0-5 Hz, or 0,1-5 Hz, where it can be determined that a detected to and fro motion is relevant to the present invention only when the frequency fl is within said first frequency range. This determination, can, for example be performed in step 202 above. According to one embodiment, it is determined whether both said first frequency f1 and said second frequency f2 are within said first frequency range.

When it is determined in step 203 that the clutch motion does not depend on vehicle motions, the method returns to step 201.

On the other hand, when it is determined that the clutch motion likely depends on vehicle motions the method continues to step 204. In step 204, a clutch control is commenced by the vehicle control system, where the clutch pedal motions are at least partially disregarded. This clutch control may follow different strategies. For example, a closing of the clutch may be commenced irrespective of the current clutch motions. This is illustrated in fig. 4A, in which the clutch is operated towards a closed position between time tp and time tE. When closing the clutch, the closing of the clutch can be accomplished according to any suitable characteristic. For example, the clutch can be closed slowly as indicated in FIG. 4A-ID by dashed lines 401-404 in order to ensure that the vehicle does not suddenly behave in a manner that is completely unexpected by the vehicle driver. A relatively slow closing of the clutch may further be advantageous when it comes to dampening the motions of the vehicle. The present invention, consequently, provides a method that may allow e.g. a vehicle start to be completed in situations where the vehicle start otherwise would likely have to be aborted.

Further, the control of the clutch need not necessarily close the clutch, but the clutch may, perhaps advantageously, be controlled according to various other strategies instead. For example, the clutch may be controlled such that the clutch is controlled to be maintained at some suitable position between open and fully closed position, e.g. at a position where some suitable torque is transmitted by the clutch, or the prevailing position of the clutch when the undesired motion begins. Further, according to one embodiment, the to and fro motions of the clutch pedal are suppressed to an extent where the undesired vehicle behaviour is overcome, but where some to and fro motion may still remain in the control system control of the clutch. It is also possible to estimate the impact of the vehicle motion on the clutch pedal motion, so that this 21 impact can be subtracted from the actual clutch pedal motion to obtain the actual clutch pedal motion intended by the driver. This is illustrated by dash dotted lines 405-408 in figs. 4A-D.

In step 205 it is determined whether clutch control is still to be maintained by the vehicle control system, e.g. because the clutch pedal motion is still detrimentally influenced by vehicle motion, and for as long as this is the case, the method returns to step 204. When it is determined in step 20 that the clutch again can be controlled according to the clutch pedal motion, the method returns to step 201 or is ended.

Finally, the present invention has been described above for a particular example of a vehicle, but is applicable for any vehicle in which driver manoeuvrable means are used to control a clutch, the clutch being any kind of suitable clutch comprising any kind of elements, and hence not necessarily a clutch of the kind exemplified above, for as long as the manoeuvring of the clutch can be accomplished independently from the manoeuvring of the driver manoeuvrable means. 22

Claims (18)

Claims 1. Method for controlling a clutch of a vehicle (100), the vehicle (100) including a clutch (106) for selectively transmitting torque to and/or from a first power source (101), said vehicle (100) further including driver manoeuvrable means (118) for manoeuvring a clutch (106), said driver manoeuvrable means (118) being movable in a movement region (A-B) between a first end position (A) and a second end position (B), opening and closing of said clutch (106) being controlled by a vehicle control system on the basis of the position of said driver manoeuvrable means (118) in said movement region (A-B), the method being characterised in, when detecting a to and fro motion of said driver manoeuvrable means (118) in said movement region (A-B): 1. determining whether said to and fro motion at least partially depends on a motion of said vehicle (100), and 2. when it is determined that said to and fro motion at least partially depends on a motion of said vehicle (100), at least partially disregarding said to and fro motion when controlling said clutch (106). 2. Method according to claim 1, wherein said vehicle motion is a first acceleration followed by a second acceleration being different in magnitude and/or direction in relation to said first acceleration. 3. Method according to claim 2, wherein said first acceleration is an acceleration at least partially in a direction of travel of said vehicle and said second direction being a direction at least partially opposite said direction of travel of said vehicle. 23 4. Method according to any one of the claims 1-3, wherein said vehicle motion is a rocking motion. 5. Method according to any one of the claims 1-4, further including: - determining a first frequency (fl) of said to and fro motion, and 1. at least partly disregarding said to and fro motion when said first frequency (fl) is within a first frequency range. 6. Method according to claim 5, further including: 1. determining a second frequency (f2) of said motion of said vehicle (100), 2. at least partly disregarding said to and fro motion when said first frequency (fl) and said second frequency (f2) is within a first frequency range. 7. Method according to claim 6 or 7, wherein said first frequency range is 0-5 Hz, or 0,1-5 Hz. 8. Method according to any of the preceding claims, wherein said to and fro motion is a motion that in a first direction of motion requests an increase in transmittable torque of said clutch (106) and in a second direction of motion requests a decrease in transmittable torque of said clutch (106). 9. Method according to any one of the preceding claims, further including: 1. at least partially disregarding said to and fro motion when controlling said clutch (106) by reducing the impact of said to and fro motion on the controlling of said clutch. 10. Method according to any one of the preceding claims, further including: 24 1. when at least partially disregarding said to and fro motion when controlling said clutch (106), closing said clutch (106) irrespective of the position of said driver manoeuvrable means (118). 11. Method according to any one of the preceding claims, further including: 1. estimating an impact of said motion of said vehicle (100) on the motion of said driver controllable means (118), and - when controlling said clutch (106), subtracting said impact of said motion of said vehicle (100) from the motion of said driver controllable means (118) when controlling said clutch according to the motion of said driver controllable means (118). 12. Method according to any one of the preceding claims, further including: 1. when at least partially disregarding said to and fro motion when controlling said clutch (106), controlling said clutch such that substantially a first torque is transmitted over said clutch (106). 13. Method according to any one of the preceding claims, further including: 1. determining a speed (vvehiad of said vehicle (100), and 2. disregarding said to and fro motion when controlling said clutch (106) when the speed (1 ''vehicle) of said vehicle (100) is below a first speed limit (viim). 14. Method according to claim 13, wherein said speed limit ( viim;vjmi) is in the range 0-30 km/h, 0-10 km/h, 0-5 km/h or 0-2 km/h. 15. Computer program comprising program code that, when said program code is executed in a computer, causes said computer to carry out the method according to any of claims 1-14. 16. Computer program product comprising a computer-readable medium and a computer program according to claim 15, wherein said computer program is contained in said computer-readable medium. 17. System for controlling a clutch of a vehicle (100), the vehicle (100) including a clutch (106) for selectively transmitting torque to and/or from a first power source (101), said vehicle (100) further including driver manoeuvrable means (118) for manoeuvring a clutch (106), said driver manoeuvrable means (118) being movable in a movement region (A-B) between a first end position (A) and a second end position (B), opening and closing of said clutch (106) being controlled by a vehicle control system on the basis of the position of said driver manoeuvrable means (118) in said movement region(A-B), the system being characterised in means for, when detecting a to and fro motion of said driver manoeuvrable means (118): - determining whether said to and fro motion at least partially depends on a motion of said vehicle (100), and - when it is determined that said to and fro motion at least partially depends on a motion of said vehicle (100), at least partially disregarding said to and fro motion when controlling said clutch (106). 18. Vehicle, characterised in that it comprises a system according to claim 17. 1. 'Old 90 1,-`-' 901. ----' 911- POI.' C 1-1,--/ VI. 'Old 901. 014, 601. \ I- H. L1.1.1.01. ZO 1.91, I,

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