WO2007030036A1

WO2007030036A1 - A method and a system for alerting a driver of a vehicle of a departure from a driving area in a lane

Info

Publication number: WO2007030036A1
Application number: PCT/SE2005/001290
Authority: WO
Inventors: Ingemar Dagh; Jörgen ANDERSSON
Original assignee: Volvo Lastvagnar Ab
Priority date: 2005-09-06
Filing date: 2005-09-06
Publication date: 2007-03-15

Abstract

The invention concerns a system and a method for alerting a driver of a vehicle of a departure from a driving area in a lane, comprising the steps of providing wheel vibrations measurements of at least one wheel on the vehicle, while the vehicle is being driven. Then using said wheel vibration measurements for detecting a periodic signal of a predetermined nature corresponding to a periodic lane marking; and in that case providing an attention signal in order to alert said driver of the lane deviation. In a preferred embodiment the periodic signal detection step comprises the steps of providing wheel speed measurements (v, ω); performing signal processing upon said wheel vibration measurements and said wheel speed measurements (v, ω) for a detection of such periodic signal of a predetermined nature. Contrary to prior art methods is provided a method which uses already available information directly, and not indirectly as when e.g. using optical sensors. The method provides a low-cost solution of lane deviation detection which can be mounted on any vehicle. The solution proposed by the present invention is based on the realisation and the taking advantage of the fact that when a vehicle is travelling on a road having lane or side markings, which are protruding from the lane and placed with periodic intervals a, the crossing of these creates vibrations in the wheels of the vehicle, which vibrations may be measured directly to detect such a lane deviation. Thus, the method uses already available indicators like the lane markings themselves and the wheel response to said lane markings for such lane deviation detection. Accordingly, an accurate detection is possible independently of the weather and road condition.

Description

20179Prioeng.doc

A METHOD AND A SYSTEM FOR ALERTING A DRIVER OF A VEHICLE OF A DEPARTURE FROM A DRIVING AREA IN A LANE

The present invention relates to a method and a system for alerting a driver of a vehicle departing from a driving area in a traffic lane.

By the present invention, the term "vehicle" is defined as a vehicle provided with at least one wheel and is capable of driving on a road, and which is being steered by a driver, which may be human or an automatic system, where said vehicle may preferably be a car or a truck, and may be in two or more parts, such as a tractor provided with one or more trailers. Other vehicles are conceivable, such as two wheeled vehicles, e.g. motorcycles.

Many traffic accidents occur when drivers accidentally, due to lack of attention or falling off to sleep, let their vehicle veer off the road, either into the side of the road and into obstacles like trees, or crosses over into the approaching traffic in the opposite side of the road. Accordingly, periodic lane markings have been provided, such as rumble strips on one or more sides of a lane, either to indicate an end side of the road by side lane markings or to indicate crossing over into a new lane by lane divider markings, the latter usually only being provided as rumble strips when roads combine. Such lane markings excite the chassis structure of a vehicle to create a loud rumbling noise and vibration, when the tyres of a vehicle are running over these in order to warn a driver that the vehicle has crossed over the rumble strips. However, the resulting rumbling noise and vibration may not be sensed at all by a driver. This applies in particular to drivers of large vehicles, such as trucks, which have wider tyres than cars, and have isolation provided to the chassis and the cab suspension system in order to increase driver comfort and to improve truck performance, which effectively blocks the rumble strip vibration signals from being sensed by a truck driver for example. Therefore, there is a need for alerting the driver when a vehicle is running over such lane markings at the incidence moment, such that he or she may correct the driving direction of the vehicle back on track, before the vehicle ends up outside the lane.

Several lane deviation warning systems have been conceived, where many comprise different types of optical sensors, such as infrared optical sensors, CCD-cameras, photo sensors, or vision systems for indication of a proximity to a lane marking, e.g. EP 1 035 509, GB 2,317,009, US5,568,137 and US 2002 042676. These all suffer from the fact that road visibility and condition is not always ideal, especially at night or during bad weather conditions, which reduces the efficiency of these systems.

A lane deviation warning system as disclosed in GB 2 232 518 comprises electrically conductive lane markings and detectors provided in the vehicle. However, this system requires the installation of conductive markings in the road, which makes this system expensive and time consuming to install.

Thus, it is the object of the present invention to provide a method and a system for alerting a driver, when his/her vehicle departs from a driving area in a lane, which alleviate the above mentioned disadvantages and safely and reliable warns a driver, when the vehicle is crossing such lane markings on the road, in particular when a resulting lane marking rumble is not sensed by a driver of a sound and vibration isolated large vehicle.

This object is achieved by a method and a system for performing such method for alerting a driver of a vehicle of a departure from a driving area in a lane, comprising the steps of performing wheel vibrations measurements of at least one wheel on the vehicle, while the vehicle is being driven; using said wheel vibration measurements for detecting a periodic signal of a predetermined nature corresponding to a periodic lane marking; and in that case providing an attention signal in order to alert said driver of the lane deviation.

Contrary to prior art methods is provided a method which uses already available information directly, and not indirectly as when e.g. using optical sensors. The method provides a low-cost solution of lane deviation detection which can be mounted on any vehicle. The solution proposed by the present invention is based on the realisation and the taking advantage of the fact that when a vehicle is travelling on a road having lane markings, which are protruding with a certain height from the lane and placed with constant increments a, i.e. periodically, the crossing of these creates vibrations in the wheels of the vehicle, which vibrations may be measured directly to detect such a lane deviation. Thus, the method uses already available indicators like the lane markings themselves and the wheel response to said lane markings for an effective lane deviation detection. Accordingly, an accurate detection is possible independently of the weather and road condition.

In a preferred embodiment, the periodic signal detection step of said method comprises the steps of providing wheel speed measurements (v, ω); performing signal processing upon said wheel vibration measurements and said wheel speed measurements (v, ω) for a detection of such periodic signal of a predetermined nature. Present signal processing devices, such as processors, have reached a processing rate capable of providing a fast and reliable response to reduced data input, such as is the case when alerting drivers of veering vehicles, where a reduced alerting time period is available for detection of a relatively low number of lane markings through the use of wheel vibrations. It is accordingly possible to employ the present method quickly and reliably by signal processing of the induced wheel vibrations. A reliable method is thus provided which results in a fast alert to a vehicle driver. The provision of a precise determination of wheel speed, preferably individual wheel speed, increases the reliability of the lane marking detection. In another preferred embodiment, the signal processing step comprises frequency domain analysis comprising peak detection, preferably within an adaptive interval around a frequency peak. Digital processing circuits are available commercially, which provide for such fast signal processing as frequency analysis is requiring, and is suitable for reducing road vibration noise and for providing a reliable detection of whether a lane marking of constant increment a, i.e. periodic, is present or not.

In a further embodiment of the method according to the invention, the signal processing step comprises FFT-analysis comprising peak detection. A fast indication of whether peaks are present indicating a lane marking is provided, using commercially available fast signal processing and filtering techniques.

In another preferred embodiment, the signal processing further comprises providing lane marking increment data (a), either in a first embodiment providing a set of predetermined increments (a = (ai, a₂, a₃, ..,a_n)), preferably being dependent upon geographical area, in which the vehicle is driving, and/or in a second embodiment adaptively adding increments (a = (a_ls a₂, a^, ..,a_n)) based on said frequency analysis.

The frequency peak being detected is a function of the lane marking increment a.

This increment a, expressed in a distance unit such as cm or mm, may thus either be known or unknown to the system, which is an advantage, considering how many different types of rumble strips are provided in the world having different increments a.

In the first embodiment, a given predetermined set of increments a is stored in a storage means, e.g. provided alongside the processor means. The set of increments a may be depending upon geographical area in the world, to which the vehicle is sold, in which case the frequency interval within which the peak detection is performed may advantageously be decreased. In the second embodiment, the frequency analysis is providing the increment data a adaptively, based on the wheel velocity measurements and the resulting detected peaks, which peaks are determined as corresponding to lane markings increments a. Thus, no predetermined input of increment data a is needed, because the system is able to "learn", which periodic wheel vibration signals are corresponding to the lane markings and which are not. Preferably, a frequency detection interval may be predetermined in order to reduce the peak detection time needed.

In a further embodiment of the method according to the present invention, noise in the wheel vibration measurements is reduced using a comparison between first and second wheel vibration measurements from a first wheel provided in one side of the vehicle and a second wheel provided opposed said first wheel on the other side of the vehicle, respectively. The lane surface and wheel condition may cause more or less wheel vibration noise, which in this way may be reduced significantly, providing a more reliable peak detection.

In yet a further embodiment of the method according to the present invention, said wheel vibrations measurements are performed on an end section of a vehicle axle supporting said at least one wheel. Here, close to the load line, the input excitations from the opposite wheel are reduced to a minimum, providing a reduced noise level influence from the rest of the vehicle, especially from the wheel opposite of the wheel being measured upon.

In another embodiment of the method according to the present invention, the wheel vibration measurement is performed for at least a vertical y-direction. Accordingly, since the vibrations induced into a wheel by driving over a plurality of lane markings having constant increment primarily is provided in the vertical direction or y- direction, the main part of such vibrations is available for detection by the present method. In a further embodiment of the method according to the present invention, at least the wheel vibration measuring step is performed continually. During driving of the vehicle periodic wheel vibration signals are being detected continuously, which ensures that no lane deviation is performed without the system being at least aware of this fact.

In a further embodiment of the method according to the present invention, the periodic wheel vibration signal is used to detect the lane marking increment and/or the relationship between the length of the lane markings and the distance between the lane markings. This is useful when the lane markings contain certain information, such as the actual speed limit.

In a further embodiment of the method according to the present invention, at least the attention signal is deactivated when the vehicle speed is outside a predefined speed interval, and/or when the vehicle is located within a predefined geographical area. Accordingly, an intelligent method and system is provided, where it is possible to distinguish between situations, e.g. when a driver wilfully drives across a rumble strip, or when the vehicle is in a country, where such lane deviation warning signals are prohibited by law, or when the driver is crossing e.g. a parking area, where there are provided lane markings, which are not in fact rumble strips, but may resemble these. A maximum vehicle speed limit is advantageously provided due to speed limitations in many countries, but also due to considerations of frequency analysis and corresponding warning reaction time limitations, when driving at these maximum speeds. A minimum speed limit is useful when the speed of the vehicle is not causing significant risk, e.g. at the time when the vehicle is starting up, and may be chosen dependent upon the total weight of the vehicle.

In a preferred embodiment of the method according to the present invention, said wheel speed measurement is provided by measuring the angular velocity of said at least one wheel with a wheel angular velocity measurement means, providing wheel radius data for said at least one wheel, and calculating the wheel speed being equal to the angular velocity multiplied by the wheel radius data. Thus, an accurate wheel speed calculation may be performed, independently of the wheel vibration measurement, providing data for a more accurate signal processing, and being independent of differing individual wheel speeds cause by e.g. skids and obstacles encountered by each wheel.

In another embodiment of the method according to the present invention, the wheel radius data is provided from a wheel data chip provided in said at least one wheel. Often, such a wheel data chip is available in tyres, giving a precise determination of wheel radius for a more accurate signal processing.

In a further embodiment of the method according to the present invention, the measurement of wheel angular velocity is provided from an ABS-system of the vehicle. Accordingly, data already present in several vehicles may be supplemented and used for this purpose as well, providing accurate data for a more precise signal processing.

In yet another embodiment of the method according to the present invention, the measurement of wheel angular velocity is provided from individual wheel speed angular velocity measurement means provided adjacent to said at least one wheel. These may be provided on the axle together with the wheel vibration measurement means or independently around the wheel, for an individual and thus more accurate determination of wheel angular velocity.

In yet a further embodiment of the method according to the present invention, the attention signal is selected from the group consisting of an audible signal, a visible signal, a tactile signal such as a vibration of the drivers seat, or any combination hereof. Thus, the attention signal may be provided from one or more sources, which may be sensed by a driver of the vehicle. In one embodiment the vehicle comprises a truck. In this case, even when providing a large truck, which is isolated from external noises such as a rumbling strip in action, the present invention provides an effective attention signal, which alerts a driver of any lane deviations.

In a preferred embodiment of the system according to the present invention, said wheel vibration measurement means comprise one or more one-, two, or three- dimensional accelerometers, which are provided on a non-rotating end section of the axle mounting said at least one wheel, adjacent to said wheel. By being provided on a non-rotating part of the axle, e.g. the wheel hub or on the axle end section adjacent to the wheel, interfering rotational vibrations in either direction is avoided. Accelerometers provide accurate wheel vibration measurement data, and may provide multi-dimensional data as well, providing further basis for an accurate detection of lane markings.

In another embodiment of the system according to the present invention, the wheel vibration measurement means, the wheel speed measurement means, the processing means, and/or optionally the means for providing lane marking increment data are provided in combination in a single unit. Thus, a system is provided, which eases installation after vehicle manufacture, and eases production of said system. Further, a chip-sized system is provided, which only requires connection to a warning system inside a driving compartment of the vehicle.

In another embodiment of the system according to the present invention, the system is arranged to communicate with a data system in said vehicle for a mutual exchange of data. Such data may advantageously comprise wheel radius data, vehicle speed indication, ABS system data provided to the system and for the vehicle data system it may comprise an alert signal, which is processed and communicated to a warning system inside said vehicle, such as e.g. a display showing alert conditions in said vehicle.

In yet another embodiment of the system according to the present invention, said at least one wheel is a front wheel of the vehicle. Thus, if a vehicle start to, drive off a lane, either into another lane or from the road, the first wheel to be driven over a lane marking is the front wheel. Thus, a fast alert signal may be provided from the system, warning the driver before the vehicle ends up outside the road.

In yet another embodiment of the system according to the present invention the system is used for alerting the driver of excessive transversal trailer oscillations, when said trailer is crossing over periodic lane markings, in which system are provided at least two wheel vibration measurement means along one side of the vehicle adjacent to the side lane markings along which the vehicle is driving for at least one first wheel of the towing vehicle and at least one second wheel of the trailer, respectively, and further comprises means for comparing the signals from said at least two wheel vibration measurement means for an indication of transversal trailer oscillations for the detection of the crossing of said at least one second wheel of the trailer of side markings, said comparing means preferably being part of the processing means. Accordingly, even vehicle oscillations on the rear side may be detected by the system according to the invention, which in an early stage of the oscillation may provide the driver with sufficient time to make corrective action to suppress these trailer oscillations. Advantageously, this only requires installation of wheel vibration measurement means in two wheels, i.e. the front wheels of the truck and trailer, respectively, in that side of the vehicle, which drives along the side of the road, which in continental Europe and the US is the right side of the vehicle's driving direction.

In the following, the invention is described with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of a truck provided with a system according the invention;

Fig. 2 is a schematic perspective view viewed at the front of an approaching truck, indicating the lane and lane markings in either side;

Fig. 3 is a schematic side view, greatly exaggerated in size, of an example of a lane marking line on a road;

Fig. 4 is a schematic view of a frequency analysis being performed by a preferred embodiment of the method according to the invention during driving of the truck; and Fig. 5 is a schematic view of a wheel approaching a lane marking having increment a.

Figure 1 shows a schematic side view of a relatively large truck 2 having a cab 22 and a covered loading area, where the truck 2 is provided with vibration isolating suspension system and broad tyres. This makes it difficult, if not impossible for a driver of the truck 2 to hear the noises created in the truck chassis, when the truck is crossing side lane markings 32 provided on a road lane 30 as shown in fig. 2. Accordingly, said truck 2 is provided with a system 1 according to a first embodiment of the present invention for performing the method according to the invention. The system 1 according to the invention is also suitable for installation in smaller vehicles, such as cars or automobiles, e.g. when the driving compartment is also isolated or the suspension system is very effective, or indeed, when the driver is physically impaired.

The system 1 generally comprises means 10 for measuring vibrations of at least one wheel, means 12, 12a, 14 for detecting a periodic signal of a predetermined nature, when the truck 2 is crossing lane markings 32, as shown in figure 2, having constant increment a, as shown in fig. 3, and driver attention means 16. Said means 12, 12a, 14 comprise wheel speed measurement means 12, 12a and processing means 14, respectively.

The wheel vibration measurement means 10 and the wheel speed measurement means 12, 12a are arranged near an axle end section, adjacent to the front left wheel 24, upon the inner side of the wheel 24. The wheel vibration measurement means 10 comprise an accelerometer for providing wheel vibration signals in the vertical or y- direction, as shown in figure 5. Accelerometers come in many varieties, including piezoelectric, potentiometric, reductive, strain gauge, piezoresistive, capacitive, and vibrating element accelerometers, which all share the characteristic of measuring a force in a given direction. Commercially available accelerometers may be delivered having one or more accelerometers in one unit measuring in the x-, y- and/or z- direction and have a size suitable for mounting inside small spaces, and may even be provided with communication means for delivering data with or without cords.

As shown in figure 5, the wheel speed measurement means 12, 12a comprise an angular velocity sensor 12 for detecting the angular velocity ω of said at least one wheel, and the system 1 is able to communicate with a wheel data chip 12a provided in the tyres upon the truck 2 by the time of tyre fabrication for the provision of wheel radius r of the tyre in question. Alternatively, the radius r of the wheel 24 may be approximated, or even be input by an operator of the system 1, e.g. maintenance personnel or the driver, or may be indicated to the system 1 in any other suitable way. Further, alternatively, the angular velocity may be provided from an ABS- system available on the truck. As a further alternative, a less reliable velocity of the vehicle as indicated by the available vehicle speed indicator may be provided to the system 1 for a rough determination of wheel speed.

As shown in figure 1, these sensors 10, 12, 12a are in communication with the processing means 14, which comprises a processor and a memory 14a for a continual signal processing of the measurements arriving from the accelerometer 10 and the wheel speed sensors 12, 12a. Based on said signal processing, the processing means 14 are arranged to alert a driver of the truck 2 of any lane crossing by actuating a visual signal device or indicator lamp 16. The system 1 further comprises a deactivation button 18 in communication with said processing means 14, which is useful e.g. in parking areas provided with periodic lane markings or in geographical areas, in which no such signal is allowed. Preferably, the attention signal is deactivated when the vehicle speed is outside a predefined speed interval, and/or when the vehicle is located within a predefined geographical area, e.g. Europe or the US, or even a parking area provided with rumble strips, where these are irrelevant to the driver of the vehicle.

In fig. 2 is shown a truck 2 with a tipper body, where the truck 2 is heading towards the side of the road 30 and thus running over side lane markings 32 provided upon it. The elongated side lane markings 32 are extending transversally of the driving direction on the lane, and are painted stripes having a periodic constant increment a, as seen in fig. 3, and a certain height, such that when a wheel of a vehicle is driving over it, vibrations are induced in the wheel, which are periodic and primarily vertically oriented along a y-axis or direction as shown in figure 5. Notice that the road 30 is further provided with lane divider markings 34, which are seen to have a longer increment a and may have a lesser height than the side lane markings 32.

The signal processing of the resulting wheel vibration measurements, which is performed in order to detect a peak, which indicates a periodic signal within a given frequency area, may be performed by using a whole range of different techniques, such as band pass filtering to reduce the signal to noise ration, and time domain analysis, such as Fast Fourier Transform or FFT analysis, and/or frequency domain analysis, and may be performed either given that lane marking increments a are predetermined or adaptively determined. Preferably, the signal processing is performed by frequency analysis, preferably directly upon the wheel speed and vibration measurements. In a preferred embodiment, as shown in fig. 4, frequency analysis is used to detect one or more peak frequencies, which indicates the presence of a periodic signal. A periodic vibration signal is induced into the vehicle wheel 24 due to the fact that the truck is crossing side lane markings 32 having a constant increment a. The periodic wheel vibration measurements registered by the accelerometer 10 at the wheel 24 may be represented as shown in figure 4, where the x-axis depicts the frequency and the y-axis depicts the acceleration registered by the accelerometers over a series of measurements, e.g. less than one revolution of the wheel, depending on wheel radius employed and increment a to be detected, while the wheel is turning along the road. Given that the wheel periphery is much larger than the increment distance a, approx. one whole revolution of a wheel is often sufficient for an accurate detection of a lane deviation. In figure 4 is shown a peak at the speed dependent frequency ft, which is equal to the angular velocity ω at the periphery of the wheel 24 divided by the constant increment a of the line markings in question.

The frequency analysis may preferably be performed by selecting an interval ft - Δf, fi +Δf around one or more such frequencies, where speed dependent frequency peaks are presumed to be located, each speed dependent frequency ft, f^, f₃... being equal to the wheel velocity divided by lane marking increments a_l5 a₂, a₃.... The surrounding frequency level of said interval ft - Δf, ft +Δf is also measured, and the peak level of the specific frequency is divided by the surrounding frequencies ft - Δf, ft +Δf to be able to detect, if the increase detected is a general noise increase or if the vibration signal is created by a lane marking, i.e. if ft/(ft - Δf) or ft/(ft + Δf) > x, where x is a predetermined level, the result of the detection of a lane marking is positive. The value x may be chosen arbitrarily, depending upon force imposed by the lane markings, which again depends on vehicle excitation characteristics, wheel performance, etc. The result from the previous quote is stored in the storage means 14a and compared to the result of the next analysis. Preferably, overtone analysis is performed for higher order harmonics as well in order to reconstruct such sine wave signal. In general frequencies in the order of 20 kHz are observed.

The lane markings 32 functioning as rumble strips may be provided by elongated strips of paint or plastic, or alternatively as grooves of a width parallel to travelled way of between 1 and 10 cm, placed with a constant distance between them, resulting in an increment a typically in the order of 2 to 15 cm. Often, regulations provide for a paved shoulder between such side lane marking and the longitudinal side end of the road, within which the driver is able take corrective action to avoid that the vehicle is ending up in the ditch. A set of data of different increments a is preferably stored in the storage means 14a, which preferably is provided in combination with the processing means, e.g. in the form of a microcontroller or embedded system. These different increments a may be provided in the form of a predetermined set a = (a_ls a₂, a₃, ..,a_n), which may depend upon the geographical areas in which the vehicle is intended to drive in, e.g. one set for Europe, one set for the US, one set for East Asia, etc. Alternatively, a frequency or time domain analysis is also able to adaptively provide increment data a = (a_l3 a₂, as, ..,a_n) given the wheel speed measurements and the results of the domain analysis. Thus, different increments a may be stored continuously, based on the system "learning" from previous experience.

The results of the digital signal processing may be stored continuously for further processing or registration purposes, and may be interchanged with an on-board vehicle data system.

Preferably, the system and method is adapted to also identify rumble strips provided across the lane, e.g. as indications to slow down speed in residential areas, and provide a driver attention signal for this situation as well, e.g. by providing different types of signals to distinguish between the two types of rumble strips. Further, the system can detect not only the interval of the lane marking, but also the relationship between the length of the lane markings and the distance between the lane markings. In this way, different information embedded in the lane markings or rumble strips can be identified by the system. This information can be e.g. the actual speed limit or a speed limit change coming up. The system can also be useful outside of e.g. schools which often has a reduced speed limit.

Noise in the wheel vibration measurements may advantageously be significantly reduced when using a comparison between first and second wheel vibration measurements from a first wheel provided in one side of the vehicle and a second wheel provided opposed said first wheel on the other side of the vehicle, respectively. This is due to the fact that in case of lane deviations over side lane markings as opposed to transversal rumble strips, the one opposed wheel is not experiencing vertical vibrations from these rumble strips, and accordingly the vibration measurement from this opposed wheel may advantageously be used to eliminate noise originating from the road surface, imbalances from the wheel and vibrations from the vehicle in general.

It has by the invention been realized, that the method and system can be used when performing wheel vibration measurements on wheels on towing vehicles as well as trailers to indicate e.g. oscillating transversal movements of the trailer, which is not otherwise noticed by the driver. Thus it is used for alerting the driver of excessive transversal trailer oscillations, when said trailer is crossing over periodic lane markings. In such a system are provided at least two wheel vibration measurement means along one side of the vehicle adjacent to the side lane markings along which the vehicle is driving for at least one first wheel of the towing vehicle and at least one second wheel of the trailer, respectively. Further, said system comprises means for comparing the signals from said at least two wheel vibration measurement means for an indication of transversal trailer oscillations for the detection of the crossing of said at least one second wheel of the trailer of side markings, said comparing means preferably being part of the processing means. Accordingly, even vehicle oscillations on the rear side may be detected by the system according to the invention, which in an early stage of the oscillation may provide the driver with sufficient time to make corrective action to suppress these trailer oscillations. Advantageously, this only requires installation of wheel vibration measurement means in two wheels, i.e. the front wheel of the truck and the back wheel of the trailer, respectively, in that side of the vehicle, which drives along the side of the road, which in continental Europe and the US is the right side of the vehicle's driving direction.

It has by the invention been realized, that the method and system also can be used to detect the divider lines between lanes in supplement to side lane markings, in which case a special lane divider crossing attention signal may chosen, e.g. one that is less noticeable than for when detecting side and transversal rumble strips. However, since the integration time is much larger for such divider line than for road side markings due to the lower frequency of the longer increments a, it may be difficult in tune to alert the driver by analyzing the periodic wheel vibration signals provided by the divider lines. Thus, these divider line detection measurements may be used for other purposes, e.g. registration purposes.

Claims

PATENT CLAIMS

1. A method for alerting a driver of a vehicle of a departure from a driving area in a lane, comprising the steps of: - providing wheel vibrations measurements of at least one wheel on the vehicle, while the vehicle is being driven;

- using said wheel vibration measurements for detecting a periodic signal of a predetermined nature corresponding to a periodic lane marking; and in that case

- providing an attention signal in order to alert said driver of the lane deviation.

2. A method according to claim 1, whereby the periodic signal detection step comprises the steps of

- providing wheel speed measurements (v, ω);

- performing signal processing upon said wheel vibration measurements and said wheel speed measurements (v, ω) for a detection of such periodic signal of a predetermined nature.

3. A method according to claim 2, whereby the signal processing step comprises frequency domain analysis comprising peak detection, preferably within an adaptive interval around a frequency peak.

4. A method according to claim 2, whereby the signal processing step comprises time domain analysis comprising peak detection, such as FFT-analysis.

5. A method according to any of the claims 2 to 4, whereby the signal processing further comprises providing lane marking increment data (a).

6. A method according to claim 5, wherein the providing of said lane marking increment data comprises providing a set of predetermined increments (a = (ai, a₂, a₃, ..,a_n)), preferably being dependent upon geographical area, in which the vehicle is driving.

7. A method according to claim 5 or 6, wherein the providing of lane marking increment data comprises adaptively adding increment data (a = (a_ls a₂, a₃, ..,a_n)) based on said frequency analysis.

8. A method according to any of the preceding claims, wherein noise in the wheel vibration measurements is reduced using a comparison between first and second wheel vibration measurements from a first wheel provided in one side of the vehicle and a second wheel provided opposed said first wheel on the other side of the vehicle, respectively.

9. A method according to any of the preceding claims, wherein said wheel vibrations measurements are performed on an end section of a vehicle axle supporting said at least one wheel.

10. A method according to any of the preceding claims, wherein the wheel vibration measurement is performed for at least a vertical y-direction.

11. A method according to any of the preceding claims, wherein at least the wheel vibration measuring step is performed continually.

12. A method according to any of the preceding claims, wherein at least the attention signal is deactivated when the vehicle speed is outside a predefined speed interval, and/or when the vehicle is located within a predefined geographical area.

13. A method according to any of the claims 2 to 12, wherein said wheel speed measurement is provided by the steps of - measuring the angular velocity (ω) of said at least one wheel with a wheel angular velocity measurement means;

- providing wheel radius data (r) for said at least one wheel; and

- calculating the wheel speed (v) being equal to the angular velocity (ω) multiplied by the wheel radius data (r).

14. A method according to claim 14, wherein the wheel radius data (r) is provided from a wheel data chip provided in said at least one wheel.

15. A method according to any of the claims 13 or 14, wherein the measurement of wheel angular velocity is provided from wheel speed angular velocity measurement means provided adjacent to said at least one wheel.

16. A method according to any of the claims 13 or 14, wherein the measurement of wheel angular velocity is provided from an ABS-system of the vehicle.

17. A method according to any of the preceding claims, wherein the attention signal is selected from the group consisting of an audible signal, a visible signal, a tactile signal such as a vibration of the drivers seat, or any combination hereof.

18. A method according to any of the preceding claims, wherein the vehicle comprises a truck.

19. A system for performing the method according to any of the claims 1 to 18 for alerting a driver of a vehicle of a departure from a driving area in a lane, said system

(1) comprising means (10) for providing wheel vibration measurements of said at least one wheel, while the vehicle is being driven; means (12, 12a, 14) for detecting a periodic signal of a predetermined nature corresponding to a lane marking, using said wheel vibration measurements; and means (16) for providing an attention signal to alert said driver of the lane deviation.

20. A system according to claim 19, wherein the wheel vibration measuring means comprises - wheel speed measurement means (12, 12a), which are arranged to provide wheel speed measurements (v) for said at least one wheel; and

- processing means (14) for performing signal processing upon said wheel vibration measurements and said wheel speed measurements for a detection of such periodic signal of a predetermined nature.

21. A system according to claim 20, where said processing means is arranged to perform frequency domain analysis comprising peak detection, preferably within an adaptive interval around a frequency peak.

22. A system according to claim 21, where said processing means is arranged to perform time domain analysis comprising peak detection, such as FFT-analysis.

23. A system according to any of the claims 19 to 22, further comprising means (14a) for providing lane marking increment data (a = (a_ls a₂, a₃, ..,an)), such as digital storage means.

24. A system according to claim 23, said digital storage means storing a predetermined set of lane marking increment data (a = (a_ls a₂, a₃, ..,a_n)).

25. A system according to claim 23 or 24, said digital storage means storing an adaptive set of lane marking increment data (a = (a_ls a₂, a₃, ..,a_n)) being provided by said signal processing.

26. A system according to any of the claims 19 to 25, where said wheel vibration measurement means (10) comprise one or more one-, two, or three-dimensional accelerometers, which are provided on a non-rotating end section of the axle mounting said at least one wheel, adjacent to said wheel.

27. A system according to any of the claims 19 to 26, where said wheel vibration measurement means are provided upon an inner side of said at least one wheel.

28. A system according to any of the claims 19 to 27, where said wheel vibration measurement means are provided in the bearings of said at least one wheel.

29. A system according to any of the claims 19 to 28, where said wheel vibration measurement means are wheel hub mountable.

30. A system according to any of the claims 19 to 29, where the wheel speed measurement means comprises wheel angular velocity measurement means and further is arranged to be provided with data concerning the wheel radius (r) of said at least one wheel, and said system is arranged to calculate the wheel speed by a multiplication of the wheel angular velocity (ω) and the wheel radius (r).

31. A system according to claim 30, in which said wheel angular velocity measurement means is provided adjacent to said at least one wheel.

32. A system according to claim 30, in which said wheel angular velocity measurement means is arranged to be provided with data from an ABS-system on the vehicle.

33. A system according to any of the claims 19 to 32, in which the wheel vibration measurement means (10), the wheel speed measurement means (12, 12a), the processing means (14), and/or optionally the means (14a) for providing lane marking increment data a are provided in combination in a single unit.

34. A system according any of the claims 19 to 33, which is able to communicate with a data system in said vehicle for a mutual exchange of data.

35. A system according to any of the claims 19 to 34, wherein said at least one wheel is a front wheel of the vehicle.

36. A system according to any of the claims 19 to 35, comprising first and second wheel vibration measurement means at least provided for a left front wheel and a right front wheel, respectively, on the vehicle for a comparison of such corresponding two wheel vibration measurements in order to reduce the wheel vibration signal noise level.

37. A system according to any of the claims 19 to 36 for alerting the driver of excessive transversal trailer oscillations, when said trailer is crossing over periodic lane markings, in which system are provided at least two wheel vibration measurement means along one side of the vehicle adjacent to the side lane markings along which the vehicle is driving for at least one first wheel of the towing vehicle and at least one second wheel of the trailer, respectively, and further comprises means for comparing the signals from said at least two wheel vibration measurement means for an indication of transversal trailer oscillations for the detection of the crossing of said at least one second wheel of the trailer of side markings, said comparing means preferably being part of the processing means (14).

38. A vehicle comprising a system according to any of the claims 19 to 37.