WO2003068572A1

WO2003068572A1 - Preventing method for a vehicle

Info

Publication number: WO2003068572A1
Application number: PCT/SE2003/000131
Authority: WO
Inventors: Nils-Gunnar VÅGSTEDT
Original assignee: Scania Cv Ab (Publ)
Priority date: 2002-02-18
Filing date: 2003-01-27
Publication date: 2003-08-21
Also published as: DE10392288B4; AU2003206283A1; SE0200464D0; DE10392288T5

Abstract

The invention relates to a method for automatically controlling a position of a vehicle (1) relative to a road boundary (5a, 5b) extending along a road (2) on which the vehicle is driving. The method comprises the steps of determining a distance to the road boundary or an estimated time to the road boundary, determining if the distance to the road boundary is shorter than a predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time, and braking at least one wheel associated with a vehicle side turned away from the road boundary and activating a retarder, if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time. The invention also relates to a second method and two computer programs.

Description

Preventing method for a vehicle

Technical Field of the Invention

The present invention relates to two methods for automatically controlling a position of a vehicle. The invention also relates to two computer programs for a control unit in a vehicle.

Description of Related Art

Systems for detecting road lane boundaries are well known in the art of road vehicles. Such systems are sometimes comprised in LDW-systems (Lane Departure Warning systems), which are used for warning a driver of a road vehicle when the vehicle is driving too close to a lane boundary or outside of a designated lane. A typical way of warning the driver is by emitting sound-signals.

US-6170955-B1 discloses an optical assembly for detecting road/lane boundaries. The optical assembly is mounted on a vehicle and may be comprised in an LDW-system.

WO-01/50088-A1 discloses a GPS (Global Positioning System) based system to monitor a vehicle's location relative to road lane boundaries. Other systems for detecting road lane boundaries are also discussed, such as systems using standard GPS, Differential GPS, video cameras, magnetic sensors or radio frequency emitters for determining the position of the vehicle relative to road lane boundaries.

Although an LDW-system in most cases manages to warn the driver of the vehicle in time to avoid e.g. driving off the road, there are still some situations where the driver might fail to hear the warning from the LDW-system or is unable to correct the direction of travel of the vehicle. Such situations can occur if the driver, for example, falls asleep, is distracted with the radio or other vehicle system, or is struck by a sudden sharp pain or illness. Summary of the invention

It is therefore an object of the present invention to improve the functionality of an LDW-system.

It is another object of the invention to prevent a vehicle from undesired departure from a road or a lane.

It is also an object of the invention to decrease the kinetic energy of the vehicle if it passes over or comes too close to road or lane boundaries, such as lines or other road markers.

The invention relates to a first method for automatically controlling a position of a vehicle relative to a road boundary extending along a road on which the vehicle is driving, where the vehicle comprises a retarder, i.e. an hydraulic brake used for braking a first vehicle side directed towards the road boundary, a second vehicle side directed away from the road boundary, at least one wheel associated with the first vehicle side, and at least one wheel associated with the second vehicle side. The first and the second vehicle sides shall throughout this description and the claims be interpreted as the two main sides of the vehicle commonly known as the left and right side respectively of the vehicle when sitting properly on a seat inside the vehicle and looking in the direction of travel. These two sides are not to be mistaken for the sides of the vehicle that are commonly known as front, rear, underside and roof of a vehicle. Furthermore, the road boundary is to be understood as any invisible or visible road boundary or lane boundary of the road, such as snow strings and elongated snow banks along a road, road or lane markers in the form of painted side lines or road centre lines. The first method comprises the steps of: determining a distance from the vehicle to the road boundary or an estimated time for the vehicle to the road boundary, comparing the distance with a predetermined distance or the estimated time with a predetermined time, determining if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time, and braking the at least one wheel associated with the second vehicle side and activating the retarder if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time. Hereby is achieved that the vehicle is directed away from the road boundary, i.e. the method achieves substantially the same effect as if the driver had steered the vehicle away from the road boundary. It is also achieved that the vehicle is braked by the retarder, thus enabling a substantial decrease of the kinetic energy of the vehicle without having to apply a dangerous and sudden braking of the at least one wheel.

Such a sudden braking may cause slip and increased wear on the least one wheel and should therefore be avoided.

The first method may comprise the step of: starting a warning signal for a driver of the vehicle if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time. Hereby is achieved that the driver is warned that the vehicle is considered as too close to the road boundary or soon is about to cross the road boundary if the direction of the vehicle is not corrected.

The first method may also comprise the steps of counting the time from the starting of the warning signal until stopping of the warning signal, comparing continuously the time with a second predetermined time and performing the step of braking the at least one wheel associated with the second vehicle side and activating the retarder only when the time is longer than the second predetermined time. Hereby is achieved that the driver has the opportunity to steer the vehicle away from the boundary before the at least one wheel associated with the second vehicle side automatically is braked and the retarder is activated, thus avoiding an unnecessary decrease of the vehicle speed.

The first method may also comprise the step of: activating an exhaust brake comprised in the vehicle if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time. Hereby is achieved that an even faster decrease of the kinetic energy of the vehicle is enabled, without having to apply the wheel brakes.

The step of determining a distance from the vehicle to the road boundary or an estimated time for the vehicle to the road boundary may comprise the step of: receiving positioning data from a positioning system, such as a Global Positioning System or differential Global Positioning System, said positioning data comprising substantially instantaneous geographical coordinates for the vehicle. Hereby a positioning system used by other systems, such as a navigation system, can be used also for this method.

The invention also relates to a second method for controlling a position of a vehicle relative to a road boundary extending along a road on which the vehicle is driving. The second method comprises the step of: receiving a signal from a magnetic sensor means or a signal emitter means positioned adjacent to the road boundary, the signal indicating that the vehicle is considered as being too close to the road boundary, and braking the at least one wheel associated with the second vehicle side and activating a retarder after the signal has been received.

The second method may comprise the step of: starting a warning signal for a driver of the vehicle if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time.

The second method may also comprise the steps of counting the time from the starting of the warning signal until stopping of the warning signal, comparing continuously the time with a second predetermined time and performing the step of braking the at least one wheel associated with the second vehicle side and activating the retarder only when the time is longer than the second predetermined time.

The second method may also comprise the step of: activating an exhaust brake comprised in the vehicle after the signal has been received.

Furthermore the invention relates to a first computer program for causing a control unit in a vehicle to control a position of the vehicle relative to a road boundary extending along a road on which the vehicle is driving, the vehicle comprising a retarder, a first vehicle side directed towards the road boundary, a second vehicle side directed away from the road boundary, at least one wheel associated with the first vehicle side and at least one wheel associated with the second vehicle side. The first computer program comprises computer readable program code means for causing the control unit to determine or receive a distance from the vehicle to the road boundary or an estimated time for the vehicle to the road boundary, computer readable program code means for causing the control unit to determine if the distance to the road boundary is shorter than a predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time, and computer readable program code means for causing the control unit to send a brake signal that causes braking of the at least one wheel associated with the second vehicle side and activation of the retarder if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time.

The first computer program may comprise computer readable program code means for causing the control unit to send a warning signal to a driver of the vehicle through at least one warning means if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time.

The first computer program may also comprise computer readable program code means for causing the control unit to count the time from the starting of the warning signal until stopping of the warning signal, computer readable program code means for causing the control unit to continuously compare the time with a second predetermined time, and computer readable program code means for causing the control unit to brake the at least one wheel associated with the second vehicle side and activate the retarder only when the time is longer than the second predetermined time.

The first computer program may also comprise computer readable program code means for causing the control unit to adapt the brake signal to activate an exhaust brake comprised in the vehicle (1) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

The first computer program may also comprise computer readable program code means for causing the control unit to receive positioning data from a positioning system, such as a Global Positioning System or differential Global Positioning System, said positioning data comprising substantially instantaneous geographical coordinates for the vehicle. Moreover the invention relates to a second computer program for causing a control unit in a vehicle to control a position of the vehicle relative to a road boundary extending along a road on which the vehicle is driving, the vehicle comprising a retarder, a first vehicle side directed towards the road boundary, a second vehicle side directed away from the road boundary, at least one wheel associated with the first vehicle side, and at least one wheel associated with the second vehicle side. The second computer program comprises computer readable program code means for causing the control unit to receive a signal from a magnetic sensor means or a signal emitter means positioned adjacent to the road boundary, the signal indicating that the vehicle is considered as being too close to the road boundary, and computer readable program code means for causing the control unit to send a brake signal that causes braking of the at least one wheel associated with the second vehicle side and activation of the retarder after the signal has been received.

The second computer program may comprise computer readable program code means for causing the control unit to send a warning signal to a driver of the vehicle through at least one warning means if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than the predetermined time.

The second computer program may also comprise computer readable program code means for causing the control unit to count the time from the starting of the warning signal until stopping of the warning signal, computer readable program code means for causing the control unit to continuously compare the time with a second predetermined time, and computer readable program code means for causing the control unit to brake the at least one wheel associated with the second vehicle side and activate the retarder only when the time is longer than the second predetermined time. The second computer program may also comprise computer readable program code means for causing the control unit to adapt the brake signal to also cause activation of an exhaust brake after the signal has been received.

In addition the invention relates to a computer program product comprising a computer usable medium and the first or the second computer program, wherein the first or the second computer program is comprised in the computer usable medium. The computer program product may be any kind of product with a computer usable medium for storing a computer program, e.g. a hard disk, a floppy disc, a flash memory, a CD, a DVD, a ROM, and an EPROM.

Brief Description of the Drawings

The objects, advantages and effects as well as features of the present invention will be more readily understood from the following detailed description of some embodiments of a system, method and computer program, when read together with the accompanying drawings, in which:

Fig. 1 is a schematic view from above of a vehicle driving on a road, Fig.2 is a schematic block diagram showing different embodiments of a system according to the invention, ^*

Fig. 3 schematically shows a control unit according to the invention,

Fig.4 is a flow diagram of a first aspect of a method according to the invention, and

Fig.5 is a flow diagram of a second aspect of a method according to the invention.

Detailed Description of Embodiments

While the invention covers various modifications and alternative constructions, preferred embodiments of the invention are shown in the drawings and will hereinafter be described in detail. However, it is to be understood that the specific description and drawings are not intended to limit the invention to the specific forms disclosed. On the contrary, it is intended that the scope of the claimed invention includes all modifications and alternative constructions thereof falling within the spirit and scope of the invention as expressed in the appended claims to the full range of their equivalents.

Fig. 1 shows a schematic view of a vehicle 1 driving on a road 2. The vehicle has four wheels: a left front wheel 3a and a left rear wheel 3b associated with a second vehicle side 4a, in the description hereinafter called the left side of the vehicle, and a right front wheel 3c and a right rear wheel 3d associated with a first vehicle side 4b, which hereinafter in the description is called the right side of the vehicle 1. The vehicle 1 may of course be any kind of vehicle able to utilise the invention and, although not illustrated, may comprise fewer or more than four wheels. A typical example is however a truck or tractor vehicle. The left and the right side of the vehicle 1 shall be understood as the two main sides of the vehicle commonly known as the left and right side respectively of the vehicle when sitting properly on a seat inside the vehicle and looking in the direction of forward travel. The road 2 is in this case a right-hand traffic road with one lane in each of the two directions. In Fig. 1, the vehicle is illustrated as driving upwards along the paper in a right lane of the road. The right lane is provided with a left and a right road (lane) boundary, 5a and 5b, in the form of a centre line and a right side line for the road 2. Side lines and centre lines of a road are typically thick painted lines (road markers) visible to a driver of the vehicle for making it easy to observe and correct the vehicle's position on the road.

The vehicle 1 may receive positioning data from a positioning system in order to determine the position of the vehicle 1 in relation to the right and left lane boundary, 5a and 5b respectively. An example of a positioning system is GPS (Global

Positioning System), which here is illustrated with only one satellite 6. The use of GPS for determining a vehicle position is in itself known in the art, and will therefore not be described in detail. A differential GPS including fixed reference base stations, which calculate a range deviation to GPS satellites and wirelessly transmit corrections to the vehicle 1, may also be used. The fixed base stations are here illustrated with only one base station 7. This positioning system is also known in the art and is not described in detail. Furthermore, as is also known in the art, the positiomng system may interact with a dead-reckoning system so that at least two geographical coordinates may be estimated by the dead-reckoning system when the positioning system temporarily is unavailable, e.g. in cases when the vehicle 1 moves through underground or underwater tunnels causing shadow areas or among tall buildings causing disturbing reflections.

Other alternatives for determining the position of the vehicle 1 in relation to the right and left road boundary 5a, 5b is e.g. by receiving signals from magnetic sensors means 8 or active or passive signal emitters 9 embedded in the road 2 adjacent to the road boundaries 5a and 5b. This, as well as other alternatives will be described in more detail below in conjunction with Fig 2, which illustrates several embodiments of a system according to the invention. The system is installed in the vehicle 1 and comprises a control unit 10 in the form of a computer. A receiver 11 comprising at least one antenna for receiving positioning data from GPS satellites is adapted to send the positioning data to a signal processor 12, i.e. a special type of coprocessor designed for performing the mathematics involved in the processing of the data received from the satellites and/or the base stations. The signal processor 12 then processes the received positioning data and sends the processed positioning data to the control unit 10. The processed positioning data may typically comprise the instantaneous geographical three-dimensional coordinates for the vehicle 1. Although the receiver 11 and the signal processor 12 in Fig. 2 are illustrated as separate units outside the control unit 10, they may of course be integrated parts of the control unit 10. Also, the signal processor 12 is optional, since the control unit 10 may be provided with a powerful CPU (Central Processing Unit) capable of processing the data from the receiver 11 in addition to its all other tasks.

The position of the vehicle relative to the road boundaries, 5a, 5b, may alternatively or in addition to the positioning system be determined with the help of an optical system being comprised in one embodiment of the system. The optical system comprises at least one camera 13, an A/D converter (not shown) and an image processing unit 14. As is known in the art, an estimated time it would take for the vehicle to pass the nearest boundary can also be calculated with the help of the optical system and the instantaneous vehicle velocity. The camera 13 takes pictures of the road 2 in front of the vehicle 1 and an analogue signal from the camera 13 is converted to a digital signal by the A/D converter. The A/D converter, which of course may be integrated in the camera 13, sends the digital signal to the image processing unit 14, which processes the image data and monitors the course of the road/lane in front of the vehicle 1 and determines the distance to the nearest road boundary. Similarly to the signal processor 12, the image processing unit 14 may be excluded in case of a powerful CPU 15 (see Fig. 3) in the control unit 10 or be comprised in the control unit 10. The camera 13 may be any suitable camera, such as a CCD (charge-coupled device) camera. An optical system for following road boundaries is as such known in the art and is therefore not described more in detail.

A radar system may also be used for road boundary detection instead of or in addition to the optical road detection system and the positioning system. The radar system may be a conventional radar system for road vehicles having a radar antenna/dome 16 and an associated radar system hardware 17 mounted in the front of the vehicle 1 and a cable connecting the radar system hardware 17 to the control unit 10. The radar signal processing may be done by a processor in the radar system hardware 17 or by the CPU 15 of the control unit 10.

The system may also comprise at least one transceiver unit, but preferably two transceiver units, 18a and 18b, positioned adjacent to the left side and right side of the vehicle 1 respectively, for receiving alert signals from the magnetic sensor means 8 embedded in the road when one of the magnetic sensors detects the vehicle 1, i.e. when one of the transceiver units 18a, 18b, is present at a certain predetermined distance from one of the magnetic sensor means 8. These received alert signals are forwarded to the control unit 10. Alternatively, the transceiver units 18a, 18b, may be used for transmitting short range radio signals, which are supposed to be recognised by one of the signal emitters 9 if the vehicle comes too close to that one of the signal emitters. When a signal emitter 9 in this way registers the presence of the vehicle 1, the signal emitter 9 informs the closest one of the transceiver units 18a, 18b of the presence of the signal emitter. Preferably the signal emitters 9 are transponders, which may comprise e.g. a resonance circuit having a capacitor and a coil (not shown). The resonance circuit resonates with short range radio signals from the closest transceiver unit, 18a or 18b, and emits an alert signal which indicates the presence of the signal emitter. Preferably, each signal emitter 9 and each magnetic sensor means 8 are provided with an identification code stored in a memory in each magnetic sensor means 8 or signal emitter 9. The identification code is also transmitted to the vehicle 1, preferably as a part of the alert signal and may comprise the geographical coordinates of the magnetic sensor means or the signal emitter that transmits the alert signal.

The control unit 10 is also connected to other ECUs (Electronic Control Units), such as speed control means in the form of an engine control unit 19, a brake control unit 20 and a gearbox control unit 21, via e.g. a CAN (Control Area Network) bus. The ECUs are not described in detail, since e.g. automatic internal combustion engine control systems, automatic gearbox control systems and brake control systems as well as their general way of reducing the speed by controlUng an engine, hydraulic brakes, exhaust brakes, air compression brakes, drum brakes and/or disc brakes, are well known in the art. However, it must be understood that the brake control unit 20 in this embodiment is adapted for controlling at least one wheel brake unit on each side of the vehicle 1 separately from the corresponding wheel brake unit on the other side of the vehicle 1. In Fig. 2, the brake control unit 20 is depicted as being connected, through hydraulics, pneumatics or through electrical wires, to four separately controlled wheel brake units 22a-d, one for each of the wheels of the vehicle illustrated in Fig. 1. The brake control unit 20 is also connected to two auxiliary brakes in the form of a retarder 35 and an exhaust brake 36. Furthermore the control unit 10 is connected to at least one warning means 23 in the form of a loudspeaker.

Fig. 3 schematically illustrates the control unit 10, which comprises the CPU 15. The CPU 15 is connected to a first port 241 via a first bus 251 in order to communicate with the ECUs 19-21, a second port 242 via a second bus 252 for communication with the signal processor 12, a third port 243 via a third bus 253 for communication with the transceiver units 18a-b, a fourth port 244 via a fourth bus 254 for communication with the image processing unit 14, a fifth port 245 via a fifth bus 255 for communication with the radar system hardware 17, and a sixth port 246 via a sixth bus 256 for sending audio signals to the loudspeaker. The CPU 15 is also connected to a storing means 26, such as a hard disk, a flash memory and a ROM (Read-only memory) or any other computer readable computer program product, via a seventh bus 257. A computer program for monitoring and controlling the position of the vehicle relative to road/lane boundaries, is installed in the storing means 26. The computer program comprises a vehicle position module 27, i.e. a part of the computer program and an ECU communication interface module 28. In this embodiment, the vehicle position module 27 comprises a dead-reckoning sub-module for calculating/estimating the position of the vehicle 1 using any dead-reckoning technique known in the art. The vehicle position module 27 also comprises a reference map 271, which comprises the road on which the vehicle 1 is currently travelling. Through the positioning data received from either the signal processor 12 and the reference map 271, or the dead- reckoning sub-module and the reference map 271, the control unit 10 is able check the vehicle position in relation to the lane or the road 2.

Depending on different aspects of a method described further down, the computer program may comprise a program module for causing the control unit 10 to receive the processed data from the image processing unit 28, the signals from the radar system and the signals from the transceiver units 18a-b. Moreover, the computer program may comprise a distance evaluation module 29, a time evaluation module 30, an indication detecting module 31, a warning signal generating module 32, a wheel brake selecting module 33 and an alert signal detecting module 34. Each one or some of the different modules of the computer program may of course be separate computer programs installed on the same or different storing means, in or outside the control unit 10, as long as they are adapted for causing the control unit 10 (or any other connected ECU, such as the brake control unit 20) to perform the methods described below. Having disclosed different parts, which could be used in different embodiments of a system according to the invention, an aspect of a first method according to the invention will now be described in conjunction with Fig. 4. In a first step SI, the distance to the nearest road boundary, such as the left road boundary 5a or the right road boundary 5b, is determined with the help of any one, some or all of the positioning system, optical system and radar system. The very determination may either be performed by the control unit 10 through the distance evaluation module 29 or by the signal processor 12, image processing unit 14 and the radar system hardware 17 respectively. Such a determination is known in the art and therefore not disclosed in detail. Alternatively or in addition, the step SI comprises calculation of a time it would take the vehicle 1 to cross one of the road boundaries 5a-b. Therefore a time could be calculated for each, some or one of the detected side/lane lines and the shortest of the calculated times is chosen as the most relevant time. The estimated time for crossing one of the detected road boundaries is equal to the distance to that road boundary divided by the instantaneous vehicle speed perpendicular to that road boundary. The distance between the vehicle and the road boundaries may of course be calculated from the position of any number of chosen reference points on the vehicle, such as the centre of the vehicle 1.

In a subsequent second step S2, the distance and/or the time it would take the vehicle to cross one of the road boundaries 5a-b determined in step SI, is/are compared to a predetermined distance and/or predetermined time, which is/are comprised in the computer program. This determination is performed by the control unit 10 through the distance evaluation module 29 and the time evaluation module 30 respectively. The predetermined distance and time may of course be changed through a user interface (not shown) by an authorised person prior to the current use of the invention. Furthermore, the predetermined distance and predetermined time may be associated with different roads, e.g. through interaction with the reference map 271 in the vehicle position module 27 such that the predetermined distance and time is different for every or some of the roads in the reference map 271 or through a database where the predetermined distance and predetermined time depends on the width of the lane/road

2.

If the distance and/or time determined in step SI is equal or shorter than the predetermined distance and/or time respectively, the vehicle 1 is considered as being too close to one of the road boundaries 5a-b and the first method continues with a third step S3. If the distance and/or time determined in step SI is longer than the predetermined distance and/or time respectively, the vehicle 1 is considered as being at an acceptable distance from the road boundaries 5a-b. In the latter case a value of an alarm parameter (AP) is set to "0" and the method continues with a fourth step S4.

In step S3, it is determined if the driver of the vehicle 1 desires to cross one of the road boundaries 5a-b, thereby driving the vehicle 1 close to one of the road boundaries 5a- b. The driver may indicate this desire by e.g. use the turning indicator (not shown) or activating the brakes within a predetermined indication time before the moment when the vehicle 1 is considered as being too close to one of the road boundaries 5a-5b in step S2. The indication detecting module 31 causes the control unit 10 to monitor the status of the turning indicator of the vehicle 1 and the activation of the brakes by receiving information from other ECUs, such as the brake control unit 20. If either the turning indicator or some of the brakes are activated or some of the brakes have been activated within the indication time, the vehicle 1 is considered as being authorised to drive near and cross the road boundaries 5a-b. At the same time, the value of the AP is set to "0". If neither the turning indicator nor the brakes are activated or the brakes have not been activated within the indication time, the value of the AP is set to "1". After the AP has been set, the method continues with the fourth step S4.

In step S4, the warning signal generating module 32, causes the control unit 10 to check the value of the AP. If the value is "1", the control unit 10 sends a warning signal in the form of a sound-signal to the driver via the at least one loudspeaker. Other warning means for other forms of warnings, such as visual and tactile warnings known in the art, may also be generated instead of or in addition to the sound-signal. At the same time as the sound-signal is generated, a real-time clock circuit (not shown) in the control unit 10 starts to count the time from the start of the sound-signal and compare this time with a second predetermined time, which, for example, is 0.5 seconds. After the sound-signal has started, the method is repeated from step SI while the sound-signal continues to sound and the real-time clock circuit counts the time and compare it to the second predetermined time. On the other hand, in the case where the value of the alarm parameter is "0", nothing happens in step S4 in this case and the method returns and repeats step SI.

Once the sound signal has started, it will not stop before the control unit 10, through the warning signal generating module 32, detects that the value of the AP has been set to "0" in step S2 or S3 during a subsequent iteration of a loop that comprises steps Sl- S4.

Usually a driver manages to adjust the course of the vehicle 1 before the second predetermined time has passed. Hence the loop that repeats steps S1-S4 defines the most common steps of this aspect of the first method. However the first method continues with a fifth step S5 after step S4, if the sound-signal has been sounding for a longer time than the second predetermined time.

In step S5, the wheel brake selecting module 33 causes the control unit 10 to determine at least one, but preferably two, of all the wheels 3a-d on a vehicle 1 that is/are going to be braked automatically. The selected wheels belong to the side of the vehicle which is furthest away from the road boundary 5a-b that originally causes the sound- signal, i.e. either the left side or the right side. Returning to Fig. 1, looking in the direction of travel of the vehicle 1, the vehicle 1 is closest to the right side line, i.e. the right lane boundary 5b. In this case the wheel brake selecting module 33 would determine that the left front wheel 3a and the left rear wheel 3b will be braked.

In step S6, after the determination in step S5, the control unit 10 sends a brake signal to the brake control unit 20, which according to the selection in step S5, sends a signal to the retarder 35, the exhaust brake 36 and the wheel brake units corresponding to the selected wheels, i.e. the wheel brake units for the left front and rear wheels 3a-b in Fig. 1. The retarder 35 and the exhaust brake 36 is then acitvated in order to brake the vehicle 1 and selected wheels are braked. The retarder 35, the exhaust brake 36 and the braking of the left front and rear wheels 3a-b causes the kinetic energy of the vehicle 1 to decrease and automatically brings the vehicle 1 away from the right side line. The braking forces acting on the vehicle 1 makes the vehicle behave as if the driver had steered the vehicle away from the right side line and slowed down the speed. The vehicle may be braked as long as the distance or the estimated time to the road boundary is shorter than the predetermined distance and/or predetermined time.

An aspect of a second method according to the invention is described in conjunction with Fig. 5. In step SI 1, it is checked if one of the transceiver units 18a-b have received an alert signal from one of the magnetic sensor means 8 or one of the signal emitters 9. A received alert signal means that the vehicle 1 is considered as being too close to a road boundary. This checking is performed by the control unit 10 with the help of the alert signal detecting module 34, which also causes the control unit 10 to set the value of the AP to "1" if one of the transceiver units 18a-b has received the alert signal and transmitted data about this to the control unit 10. If none of the transceiver units 18a-b has not received any alert signal since the last time the control unit 10 checked for new alert signals, the value of the AP is set to "0". If the value of the AP is "0" after it has been set, the method continues with step S13 and if the value of the AP after it has been set is "1", the method continues with step S12. The position of the vehicle 1 may be calculated by comparing the geographical coordinates of the vehicle 1 (received from the positioning system) with the geographical coordinates of the magnetic sensor means 8 or the signal emitter 9 (received from an alert signal). Alternatively, if the vehicle 1 comprises at least one transceiver unit adjacent to the left side 4a and at least one adjacent to the right side 4b, the position may be estimated by determining which one of the transceiver units 18a-b that received the alert signal. For example, if the vehicle 1 in Fig. 1 is considered as being too close to the right side line, at least one signal emitter 9 adjacent to the right side line transmits an alert signal, which is received by a right transceiver unit adjacent to the right side of the vehicle 1. Thereby, the control unit is able to determine that the vehicle is too close to the right side line and that at least one left wheel ought to be braked.

All subsequent steps after step SI 1 correspond to the steps S3- S6 described above, i.e. step S12 correspond to step S3, step S13 correspond to step S4, step S14 correspond to step S5 and step S15 correspond to step S6.

Although the two last steps of the two aspects comprise the transmission of a brake signal to the brake control unit 20, which then transmits a signal to the auxiliary brakes and selected wheel brake units, it is of course also within the invention to directly send a brake signal to the selected wheel brake units and the auxiliary brakes. This would be the case when, e.g., the control unit 10 also incorporates all the functionality of the brake control unit 20. It is also within the invention to connect e.g. the retarder 35 and the exhaust brake 36 to the control unit 10 via e.g. the gearbox control unit 21.

Instead of only braking either the right wheels or the left wheels, all wheels or both right wheels and left wheels may be braked as long as wheels associated with one of the left and right side of the vehicle are braked more than the wheels associated with the other side. In situations where a specific lateral acceleration is created due to the braking of the vehicle 1, this third aspect applicable to both the methods enables the speed and hence the kinetic energy to be decreased even more rapidly than through the use of the aspects of the first and the second method described above. The method according to the invention may also be used for bringing the vehicle 1 to standstill. A speed sensor (not shown) may be used for monitoring the vehicle speed during the braking and causing vehicle exterior hazard lights to be activated when the vehicle 1 has been brought to a standstill. Alternatively the hazard lights may be activated as soon as the braking starts in order to rapidly warn other vehicles nearby.

Yet another aspect appHcable to the method is to brake the wheels on the side furthest away from the road boundary and to add traction torque on the driving wheel/wheels on the opposite side (i.e. the side facing the road boundary). This will create an increased steering moment away from the road boundary. Depending on the added traction torque, this aspect may lessen the reduction of the speed compared to the other aspects of the methods disclosed above.

Claims

1. A method for automatically controlling a position of a vehicle (1) relative to a road boundary (5a, 5b) extending along a road (2) on which the vehicle (1) is driving, the vehicle (1) comprising a retarder (35), a first vehicle side directed towards the road boundary (5a, 5b), a second vehicle side directed away from the road boundary (5a, 5b), at least one wheel associated with the first vehicle side, and at least one wheel associated with the second vehicle side, comprising the steps of: determining a distance from the vehicle (1) to the road boundary (5a, 5b) or an estimated time for the vehicle (1) to the road boundary (5a, 5b), comparing the distance with a predetermined distance or the estimated time with a predetermined time, determining if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time, and characterised by the step of: braking the at least one wheel associated with the second vehicle side and activating the retarder (35) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

2. A method according to claim 1, comprising the step of: starting a warning signal for a driver of the vehicle (1) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time.

3. A method according to claim 2, comprising the steps of counting the time from the starting of the warning signal until stopping of the warning signal, comparing continuously the time with a second predetermined time and performing the step of braking the at least one wheel associated with the second vehicle side and the activation of the retarder only when the time is longer than the second predetermined time.

4. A method according to any one of the preceding claims, comprising the step of: activating an exhaust brake (36) comprised in the vehicle (1) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

5. A method according to any one of the preceding claims, wherein the step of determining a distance from the vehicle (1) to the road boundary (5a, 5b) or an estimated time for the vehicle (1) to the road boundary (5a, 5b) comprises the step of: receiving positioning data from a positioning system, such as a Global Positioning System or differential Global Positioning System, said positioning data comprising substantially instantaneous geographical coordinates for the vehicle.

6. A method for controlling a position of a vehicle (1) relative to a road boundary (5a,

5b) extending along a road (2) on which the vehicle (1) is driving, the vehicle (1) comprising a retarder (35), a first vehicle side directed towards the road boundary (5a, 5b), a second vehicle side directed away from the road boundary (5a, 5b), at least one wheel associated with the first vehicle side, and at least one wheel associated with the second vehicle side, comprising the step of: receiving a signal from a magnetic sensor means (8) or a signal emitter means (9) positioned adjacent to the road boundary (5a, 5b), the signal indicating that the vehicle (1) is considered as being too close to the road boundary (5a, 5b), and characterised by the step of braking the at least one wheel associated with the second vehicle side and activating the retarder after the signal has been received.

7. A method according to claim 6, comprising the step of: starting a warning signal for a driver of the vehicle (1) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than a predetermined time.

8. A method according to claim 7, comprising the steps of counting the time from the starting of the warning signal until stopping of the warning signal, comparing continuously the time with a second predetermined time and performing the step of braking the at least one wheel associated with the second vehicle side and activating the retarder only when the time is longer than the second predetermined time.

9. A method according to any one of claims 6-8, comprising the step of: activating an exhaust brake (36) comprised in the vehicle (1) after the signal has been received.

10. A computer program for causing a control unit (10) in a vehicle (1) to control a position of the vehicle (1) relative to a road boundary (5a, 5b) extending along a road (2) on which the vehicle (1) is driving, the vehicle (1) comprising a retarder (35) and a first vehicle side directed towards the road boundary (5a, 5b), a second vehicle side directed away from the road boundary (5a, 5b), at least one wheel associated with the first vehicle side and at least one wheel associated with the second vehicle side, comprising computer readable program code means for causing the control unit (10) to determine or receiving a value of a distance from the vehicle (1) to the road boundary (5a, 5b) or an estimated time for the vehicle (1) to the road boundary (5a, 5b), computer readable program code means for causing the control unit (10) to determine if the distance to the road boundary (5a, 5b) is shorter than a predetermined distance or if the estimated time to the road boundary is shorter than a predetermined time, and characterised by computer readable program code means for causing the control unit (10) to send a brake signal that causes braking of the at least one wheel associated with the second vehicle side and activation of the retarder (35) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

11. A computer program according to claim 10, comprising computer readable program code means for causing the control unit (10) to send a warning signal to a driver of the vehicle through at least one warning means (23) if the distance to the road boundary is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

12. A computer program according to claim 11, comprising computer readable program code means for causing the control unit (10) to count the time from the starting of the warning signal until stopping of the warning signal, computer readable program code means for causing the control unit (10) to continuously compare the time with a second predetermined time, and computer readable program code means for causing the control unit (10) to perform the braking of the at least one wheel associated with the second vehicle side and activating the retarder (35) only when the time is longer than the second predetermined time.

13. A computer program according to any one of claims 10-12, comprising computer readable program code means for causing the control unit (10) to adapt the brake signal to activate an exhaust brake (36) comprised in the vehicle (1) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predetermined time.

14. A computer program according to any one of claims 10-13, comprising computer readable program code means for causing the control unit (10) to receive positioning data from a positioning system, such as a Global Positioning System or differential Global Positioning System, said positioning data comprising substantially instantaneous geographical coordinates for the vehicle.

15. A computer program for causing a control unit (10) in a vehicle (1) to control a position of the vehicle (1) relative to a road boundary (5a, 5b) extending along a road (2) on which the vehicle (1) is driving, the vehicle (1) comprising a retarder (35), a first vehicle side directed towards the road boundary (5a, 5b), a second vehicle side directed away from the road boundary (5a, 5b), at least one wheel associated with the first vehicle side, and at least one wheel associated with the second vehicle side, comprising computer readable program code means for causing the control unit (10) to receive a signal from a magnetic sensor means (8) or a signal emitter means (9) positioned adjacent to the road boundary (5a, 5b), the signal indicating that the vehicle (1) is considered as being too close to the road boundary (5a, 5b), and characterised by computer readable program code means for causing the control unit (10) to send a brake signal that causes braking of the at least one wheel associated with the second vehicle side and activation of the retarder (35) after the signal has been received.

16. A computer program according to claim 15, comprising computer readable program code means for causing the control unit to send a warning signal to a driver of the vehicle through at least one warning means (23) if the distance to the road boundary (5a, 5b) is shorter than the predetermined distance or if the estimated time to the road boundary (5a, 5b) is shorter than the predeterrmned time.

17. A computer program according to claim 15, comprising computer readable program code means for causing the control unit (10) to count the time from the starting of the warning signal until stopping of the warning signal, computer readable program code means for causing the control unit (10) to continuously compare the time with a second predetermined time, and computer readable program code means for causing the control unit (10) to perform the braking of the at least one wheel associated with the second vehicle side and activating the retarder (35) only when the time is longer than the second predetermined time.

18. A computer program according to any one of claims 15-17, comprising computer readable program code means for causing the control unit (10) to adapt the brake signal to also cause activation of an exhaust brake (36) after the signal has been received.

19. A computer program product (26) comprising a computer usable medium and a computer program according to claim 10 or 15, wherein the computer program is comprised in the computer usable medium.