GB2506289A

GB2506289A - Enabling a vehicle lane departure warning system when road speed, steering angle and steering angle speed meet threshold criteria

Info

Publication number: GB2506289A
Application number: GB1320615.6A
Authority: GB
Inventors: Adam Gelencser; Alain Dunoyer
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2011-11-22
Filing date: 2011-12-03
Publication date: 2014-03-26
Also published as: GB2496975B; GB2496975A; WO2013076077A1; GB201220840D0; GB201320615D0; GB201120115D0

Abstract

A vehicle warning system 16 associated with lane departure compares road speed, steering angle and rate of change of steering angle to threshold values. If criteria of the comparison are satisfied for a pre-determined period, the warning system is enabled and it may be disabled if they do not. Vehicle speed 12, steering wheel angle 13 and rate of change thereof 14 may be obtained from vehicle CAN BUS 11; alternatively the rate of change of steering angle may be determined from the steering wheel angle and a clock signal. Lane departure warning or side-swipe warning systems may thus be selectively enabled based on a road classification which is actively determined from the vehicles operational parameters e.g. disabled on a tortuous road and automatically enabled on a straight highway.

Description

Warning System of a Vehicle

TECHNICAL FIELD

The present invention relates to a method and system of active determination of a classification of a road and to a vehicle warning system associated with lane departure, and a method of enabling such a warning system. Aspects of the invention relate to a system, to a controller, to a method and to a vehicle.

BACKGROUND

Determination of the classification of a road enables vehicle systems to be automatically optimized. Thus a highway may be broadly differentiated from a minor road by the extent and frequency of the bends and giadients thereof. Active monitoring from the vehicle permits the changing nature of a road to be accommodated so that, for example, the formal classification of a road by a highway authority is not important. Thus the nature of the road is sensed from the vehicle, and classified accordingly to pre-determined parameters, which may vary between vehicle types.

An alternative means of determining road classification is by reference to map information, for example via a GPS (Global Positioning Satellite) system. On-board active monitoring of road type avoids the need for mapIGPS data, and is appropriate where such data is not available or is not accurate.

Lane departure warning systems are well-known and comprise camera or other recognition apparatus for sensing departure of a vehicle from a lane. Such systems may for example use lane markings as a reference for sensing lane departure, and are usually automatically enabled above a reference speed appropriate for highway driving, typically 60 kph.

In operation such systems provide an audible and/or visual indicator to the driver to warn of unintentional lane departure. The main reason for lane departure warning is to alert a driver who may be sleepy or inattentive, and thus be allowing a vehicle to wander across the highway at speed. These systems have the greatest application in highway driving where roads tend to be relatively straight and featureless.

A related kind of lane departure warning system relates to imminent side-swipe conditions.

Rear facing vehicle cameras or other sensors monitor following vehicles Should a driver begin to change lanes, for example for overtaking, a warning will be given in the event that a following vehicle appears to be approaching in the lane to which movement is intended.

Side-swipe warning is useful in multi-lane highway driving, where significant differences in vehicle speed are common.

One problem with warning systems of this kind is the frequency with which false alerts may be sounded during intentional lane change. Such alerts can be a considerable annoyance on, for example, a twisting or switchback road, so that the tendency is for the vehicle driver to disable the system by switching it off. The benefit of such systems as an aid to safety is thereby negated. Where a vehicle is driven by several drivers, awareness of a disabled system may not be apparent. If disabled, a driver may neglect or forget to re-enable the system.

In one prior art lane departure warning system a warning is suppressed when steering inputs are high; nevertheless such a system gives a warning when the vehicle crosses a lane boundary in a straight line, for example when cutting a corner on a twisting road.

In one prior art side swipe warning system, a warning may be given on a twisting road if a following vehicle appears to be a potential threat as the vehicles cut corners and thereby cross a lane boundary.

Such nuisance warnings should be obviated if possible.

What is required is a means and method of active determination of a road classification from a vehicle, and of automatically enabling a vehicle warning system such as a lane departure warning system or a side-swipe warning system, when appropriate.

SUMMARY OF THE INVENTION

According to an aspect of the invention there is provided a vehicle warning system associated with lane departure, comprising a controller arranged to receive input signals indicative of road speed, steering angle and rate of change of steering angle and to enable or activate said warning system if said input signals satisfy predetermined threshold measures for a pre-determined period.

According to an aspect of the invention there is provided a method of operating a vehicle warning system associated with lane departure, the method comprising: Detection of a road speed parameter of the vehicle; Detection of a steering angle parameter of the vehicle; Detection of a rate of change of steering angle parameter, and; Enabling said warning system if said parameteis meet pie-determined thresholds for a pre-determined period.

In embodiments, the steering parameters may include a first condition whereby steering angle is within a pre-determined angular range; a second condition whereby the standard deviation of the moving average of changing rate of steering angle is less than a pre-determined numerical threshold; and a third condition whereby the rate of change of steering angle is less than a pre-determined rate threshold.

By steering angle may be meant an angle of the steering wheel, an angle of the steered The warning system may automatically enable after the pre-determined period, so as to confirm that the vehicle is within an envelope of speed and steering appropriate to highway driving. Should any of the parameters fall below a prescribed threshold, or fall outside a prescribed band, the warning system is in one embodiment immediately disabled to eliminate warnings.

The invention thus enables the warning system only when speed and steering conditions are satisfied. Accordingly such systems need not be enabled continuously, resulting in a potential savings in electronic processing demand and heat generation within the warning system devices.

In an embodiment the invention may provide a method and system of enabling a warning system associated with lane departure or lane change of a vehicle by determining continuous substantially straight line travel of the vehicle for a pre-determined period. In an embodiment, the warning system is immediately disabled should substantially straight line travel cease.

By substantially straight line travel we mean travel associated with highway dnving and major roads, in which grades and curves of the highway are modest and thus suitable for high speed travel. Such highway driving is typically associated with the highest road classification, and exemplified by multi-lane highways, motorways, auto routes and certain toll roads.

In contrast minor roads, town roads and rural roads of a generally single lane character would not tend to give substantially straight line travel. Such roads are of a lower classification.

In one embodiment a vehicle speed threshold must be exceeded in order to enable the warning system.

In one embodiment the pre-determined speed threshold is greater than 80 kph. In one embodiment the speed threshold is one of 90 kph or 100 kph. The speed threshold may be settable or fixed (embedded).

In one embodiment the steering angle is within a pre-determined angular range of ± 30° or ± 25° or ± 20° or ± 15°. The angular range may be normalized so as to indicate an angular range about the straight ahead condition of less than 20° or less than 15° or less than 10°; normalization takes into account a long highway curve where the steering angle may be maintained at a deviation from the centre position for a period of time. The period of time for which normalization is effected may be limited, for example less than 20 seconds. The pre-determined angular range may be fixed or settable.

In one embodiment the standard deviation of the moving average of changing steering wheel angle is less than 5, and may be less than 4 or less than 3 or less than 2. The standard deviation may be fixed or settable.

The period over which data is retained for calculation of the standard deviation may be limited, to for example 40, 30, 20, or 10 seconds. This period may be settable.

In one embodiment the rate of change of steering wheel angle (speed) may be less than 6° per second, or less than 5° per second, or less than 4° per second, or less than 3° per second or less than 2° per second; this rate of change may be fixed or settable.

In one embodiment the pre-determined waiting time period before enabling the system is 30 seconds, or 45 seconds, or 60 seconds or 90 seconds or 120 seconds. This pre-determined time period may be fixed or settable.

The pre-determined time period may also be referred to as analogue of time, for example an equivalent number of pulses of a clock signal of the vehicle electronic control system. Thus a 10Hz clock signal has 600 pulses in a period of 60 seconds.

An embodiment of the method of the invention permits the reference values quoted above to be held in a read only memory by reference to a look-up table, and different values may be assigned depending on, for example, the operating condition of the vehicle. An algorithm may be provided to calculate a reference value according to appropriate input parameters of, for example vehicle speed, gear ratio, gear range etc. Alternatively the reference values may be settable by the vehicle driver, or by a technician having appropriate skill and equipment.

Aspects of the invention may typically be embodied in a control system of the vehicle, for example an ECU comprising a processor and memory, and is repeatedly or continually refreshed at a suitable refresh rate, exceeding for example 10Hz.

According to embodiments of the invention the warning system is disabled if any input variable fails to meet the reference value when checked at the system refresh rate.

The warning system may be a lane departure warning system, or a side-swipe warning system, or another kind of warning system associated with change of lanes or lane departure. Such warning systems may be enabled separately or together in any combination.

Aspects of the invention also provide a vehicle having the control system described above, or a vehicle embodying the method as described above.

Other features of the invention will be apparent from the claims appended hereto.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-Fig. 1 is an embodiment of an algorithm for determining whether a lane departure warning system should be on or off.

Fig. 2 is a detailed schematic of inputs and reference values for the algorithm of Fig. 1.

DETAILED DESCRIPTION

With reference to Fig. 1 a vehicle CAN BUS is indicated by conduit (11) along which electrical signals pass. Such signals are indicative of many vehicle conditions, and are generated by suitable sensors. CAN (controller area network) systems are well-known and need not be further described here; they are widely used individually and in combination to control many aspects of vehicle operation.

Three generally universally available CAN signals are vehicle speed (12), steering wheel angle (13) and rate of change of steering wheel angle (14). The invention uses these three signals in an algorithm (15) to determine automatically whether or not to enable a lane departure warning (LDW) system (16). The algorithm is typically implemented in an electronic control unit associated with an LDW system.

With reference to Fig. 2, raw vehicle data is fed to the algorithm (1 5) from the CAN BUS, not shown for clarity. The algorithm (15) comprises a decision module (51), which determines whether or not to enable the LOW, based on inputs of vehicle speed (12), steering wheel angle (13) and rate of change of steering wheel angle (14). Raw vehicle speed signal (12) is provided to the algorithm in both filtered and unfiltered forms (31, 32). An electronic filter (21) of known kind smoothes the raw speed signal to reduce or eliminate transients, and thereby produced the filtered input (31).

The signal of steering wheel angle (13) is provided to the algorithm as a normalized and filtered input (33), and as moving average and filtered input (34).

Normalization (22) ensures that a steady departure of the steering wheel from the straight ahead position, for example during a high speed curve on a highway, is not interpreted as lane departure. Any suitable normalization technique may be applied, for example by comparing a raw signal with a filtered signal. The normalized signal is filtered at (23) to reduce or remove transients.

A moving average of steering wheel angle is determined at (25) for example over a period of seconds (as indicated in Fig. 2). This moving average is filtered at (26) to reduce or remove transients.

The signal (14) of rate of change of steering wheel angle is filtered at (27) to reduce or remove transients.

Reference inputs to the algorithm, for example retained in a memory of an electronic control unit, comprise minimum speed (41), live speed limit on' (42); live speed limit off' (43); speed off motorway (48); maximum steering wheel angle (44) in degrees; standard deviation (45) of steering wheel angle; speed of steering wheel (46) in degrees per second, and wait time (47) in seconds.

Typical values for each reference input are given in each box (41-48) as shown in Fig. 2, and may be fixed or settable according to the vehicle and/or requirements of the user. The inputs (31-35) and reference inputs are provided to the decision module (51) from which a binary on/off signal is provided to the LDW system (16).

Thus the settable variables of Fig. 2 comprise the period for determining the moving average of steering wheel angle (20 seconds); the minimum vehicle speed for enabling LDW (6Okph); the enabling speed for LDW (6Okph); the disabling speed for LDW (also 6okph); the maximum steering wheel angle for enabling LDW (10 degrees); the standard deviation associated with the moving average of steering wheel angle (3.9); the maximum speed of change of steering wheel angle (4.64 degrees per second) and the waiting time for enabling LDW (40 seconds).

The decision module tests for satisfaction of inputs associated with the reference values (41- 48), so that if all tests are satisfied, LDW is automatically enabled. Failure of any variable to satisfy the relevant test results in disabling of LDW.

Thus in an example installation LDW will have an on/off state which may be manually set by a vehicle driver. LDW may automatically be switched on each time the vehicle engine is started.

In the present, non-limiting embodiment, the tests for automatic enabling of LDW are: 1. Minimum vehicle speed must exceed input value (41) [6Okph]. For this purpose the filtered speed signal (31) is used to avoid repeated change of state at or about the trigger speed (41) as a result of slight variations in vehicle speed.

2. Vehicle speed must exceed input value (42) [6okph]. For this purpose the raw speed signal (32) is used.

3. Vehicle speed must not be at or below input value (43) [6Okph]. For this purpose the raw speed signal is used. Tests 2 and 3 permit different speeds to be set; thus the enabling speed of test 2 may be higher than the disabling speed of test 3.

4. Normalized steering wheel angle must be less than input value (44) [100] departure from the straight ahead condition; a greater angle would not be indicative of conditions for LDW.

5. Standard deviation of the moving average of steering wheel angle should not exceed input value (45) [3.9]. Thus settable value could be in the range 0-5 where 0 is indicative of no steering wheel movement, and 5 is still indicative of substantially straight line driving. A standard deviation greater than 5 could indicate conditions unsuitable for LDW.

6. Steering wheel speed should not exceed input value (46) [4.64 degrees per second].

The settable value could be in the range 0-5 degrees per second, and is indicative of non-violent movements in highway driving. Speeds greater than 5 degrees per second could indicate conditions unsuitable for LDW.

7. Conditions 1-6 should be continually satisfied during the wait time input value (47) of [40 seconds], and if so LDW is automatically enabled. The time period is settable, and may of course be defined by counting an alternative reference, such as the refresh rate of the algorithm.

In the event that any one of the conditions 1-6 fails to be met, and speed is below speed off motorway (48), LDW is automatically disabled, and not again enabled until conditions 1-6 and condition 7 are met. The time limit of condition 7 ensures not only that highway driving is detected with confidence, but that repeated enable/disable cannot occur very frequently.

In a refinement, the system can allow for a harsh movement of the steering wheel whilst LDW is enabled. Thus if condition 6 only is breached whilst LDW is enabled, a further test may determine if raw vehicle speed exceeds the speed off motorway (48). If so LDW, remains enabled so as to avoid sudden unnecessary disabling of LDW.

Likewise LDW requires a check of raw speed to ensure that enabling of LDW is appropriate.

Continual testing of the inputs is carried out at the selected refresh rate, which may be 10Hz or greater, to the intent that disabling of LDW is immediately upon detection of an input associated with non-highway driving.

This embodiment is described with refeience to a CAN signal of rate of change of steeling wheel position (14). It will however be appreciated that this input can also be derived from the CAN signal of steering wheel position (13) by reference to a clock signal. Typically the invention has a 10Hz refresh rate, which provides a clock signal at 0.1 second intervals; accordingly the wait time reference value (47) may be defined as a count of clock signals which in this example is 400 for a forty second delay.

Filters 21, 23, 26, 27 are piovided foi each input 31, 33, 34, 35 so as to smooth the electronic signal, both to deal with minor changes of the raw signal and to accommodate electronic noise and the like. It will of course be understood that the nature and effect of such filters is within the knowledge of the skilled person, and an appropriate filter and range will be selected according to characteristics of the raw signal. If, in any paiticular case, the raw signal is sufficiently smooth, it will be further understood that the respective filter may be dispensed with.

This aspect of the invention relates to a lane departure warning (LOW) system. Thus on a twisting or switchback road, the LDW system is automatically disabled so that ciossing a lane boundary, for example when cutting a corner, does not trigger a warning.

In the alternative of a side-swipe warning system, the same method may be used to obviate false warnings. Thus two cars following closely on a twisting road may occasionally depart from lanes whilst cutting corners. This may appear to a conventional side-swipe warning system as a threat, as the following vehicle appears to the side of the leading vehicle when the leading vehicle crosses a lane marking.

The present invention obviates such false warnings by using a combination of steering inputs to enable the side-swipe warning system only when conditions of substantially straight line travel are piesent foi a pre-deteimined peiiod.

The invention is described in relation to a lane departure warning system. However it will be undeistood that, in geneial, the system allows determination of a classification of road according to the frequency and late of steering input having regard to vehicle speed. Such classification may be useful in automatically placing the vehicle in an operating mode appropriate to the conditions of use, such as adapting different suspension settings for highway and countly ioad conditions.

Claims

Claims 1. A vehicle warning system associated with lane departure, comprising a controller arranged to receive input signals indicative of road speed, steering angle and rate of change of steering angle and to enable or activate said warning system if said input signals satisfy predetermined threshold measures for a pre-determined period.
2. A system according to claim 1 comprising a memory arranged to retain threshold measures of road speed, steering angle, a moving average of changing steering wheel angle, and rate of change of steering angle.
3. A system according to claim 1 or 2 wherein the controller is arranged to disable said lane departure warning system if any of said signals fail to satisfy said threshold measures.
4. A system according to any of claims 1 to 3 comprising a clock signal defining a refresh rate for testing said input signals against said threshold measures.
5. A system according to any of claims 1 to 4 wherein said threshold measures comprise numerical values.
6. A method of operating a vehicle warning system associated with lane departure, the method comprising: Detection of a road speed parameter of the vehicle; Detection of a steering angle parameter of the vehicle; Detection of a rate of change of steering angle parameter, and; Enabling said warning system if said parameters meet pre-determined thresholds for a pre-determined period.
7. A method according to claim 6 comprising the step of: Disabling said warning system if any of said parameters signals fail to meet said thresholds.
8. A vehicle adapted to perform a method as claimed in claim 6 or?, or having a system as claimed in any of claims 1 to 5.