Method for maintaining a vehicle in the centre of its traffic lane

Abstract

The invention relates to a method for steering a motor vehicle (10) driving on a road (30) which comprises at least one traffic lane (31), which method comprises the steps of: - detecting the edges of the traffic lane of the motor vehicle, - selecting, by a computer (11) of the motor vehicle, an activated or deactivated state of a function for automatically keeping the motor vehicle in the traffic lane, and - when the activated state is selected, controlling at least one steering actuator of the motor vehicle in order to keep it in the traffic lane. According to the invention: - in the detection step, a width (L) of the traffic lane is evaluated, and - in the selection step, the state of the function for automatically keeping the motor vehicle in the traffic lane is selected depending on the evaluated width.

Description

Description Title of the invention: Method for keeping a vehicle in the center of its lane Technical field of the invention

[0001] The present invention relates generally to driving aids for motor vehicles.

[0002] The invention relates more specifically to a method for controlling a motor vehicle traveling on a road which comprises at least one traffic lane, the method comprising steps of: - detection of the edges of the traffic lane taken by the motor vehicle, - selection by a computer of the motor vehicle of a state, activated or deactivated, of a function for automatically maintaining the motor vehicle in said traffic lane, then - when the activated state is selected, control of at least one actuator for steering the motor vehicle to keep the vehicle in said traffic lane.

[0003] It also relates to a motor vehicle suitable for implementing such a process. It applies more particularly to cars and other motorized vehicles traveling on roads. State of the art

[0004] In an effort to make motor vehicles safer, they are currently being equipped with driver assistance systems and even highly automated driving systems.

[0005] These are typically lane keeping systems, namely lane keeping or lane centering systems (better known by the English acronyms LKA for "Lane Keeping Assist" and LCA for "Lane Centering Assist").

[0006] To function, such a system needs to know the position of the edges of the traffic lane taken by the vehicle. Currently, it is known to use a sensor, such as a camera, which incorporates image processing means to determine the position of these lane edges.

[0007] It is understood that the detection of the edges of the traffic lane must be extremely reliable to prevent the vehicle from leaving it.

[0008] Unfortunately, this detection does not always give complete satisfaction.

[0009] The applicant was in fact able to observe that it happens, on certain narrow two-way secondary roads ("country roads"), that the two marking lines the edges of the roadway are considered as forming the edges of the traffic lane. It is understood that in this situation, the vehicle is then driven to center itself not in relation to its traffic lane, but in relation to the road, so that it finds itself straddling two lanes, which is not desirable (the driver, who has his hands on the steering wheel, then having to correct the trajectory of the vehicle). Presentation of the invention

[0010] In order to overcome the aforementioned drawback of the state of the art, the present invention proposes to rely on at least one parameter (the width of the detected traffic lane) to check that the data on which the function of automatically keeping the vehicle in the center of its traffic lane is based is reliable.

[0011] More particularly, the invention proposes a control method as defined in the introduction, in which: - in the detection step, a width of said traffic lane is evaluated, and

[0012] - in the selection step, the state of the automatic holding function is selected according to the evaluated width.

[0013] Thus, thanks to the invention, if the width of the traffic lane presents a value which is surprising in itself or surprising in relation to other parameters detected by the vehicle, it is possible to deactivate the function of automatically keeping the vehicle in the center of its traffic lane, in order to avoid the driver having to correct the trajectory of the vehicle imposed by actuators.

[0014] Other advantageous and non-limiting characteristics of the control method according to the invention, taken individually or in all technically possible combinations, are the following:

[0015] - a stage of measuring the quality of the road surface is planned; - at the selection stage, the state of the automatic holding function is selected according to the measured quality;

[0016] - a step is planned for acquiring a maximum authorized speed on the said road; - at the selection stage, the state of the automatic holding function is determined based on said acquired maximum authorized speed;

[0017] - a step is planned for acquiring a speed regulation instruction for the movement of the motor vehicle; - in the selection step, the state of the automatic holding function is selected according to said travel speed regulation instruction;

[0018] - if the evaluated width is less than a minimum threshold, the activated state is suitable for selection;

[0019] - if the evaluated width is greater than a maximum threshold, the disabled state is se- selected;

[0020] - if the evaluated width is between the minimum threshold and the maximum threshold, the state of the automatic holding function is selected differently depending on whether the evaluated width is between two intermediate thresholds which are between the minimum threshold and the maximum threshold, or whether the evaluated width is less than the smaller of the two intermediate thresholds, or whether the evaluated width is greater than the larger of the two intermediate thresholds;

[0021] - when the evaluated width is between the two intermediate thresholds: if the maximum authorized speed is higher than a speed threshold, the activated state is suitable for selection, but if the maximum authorized speed is lower than the speed threshold, the state of the automatic maintenance function is selected according to the measured quality;

[0022] - when the evaluated width is between the minimum threshold and the smaller of the two intermediate thresholds, if the measured quality is greater than a quality threshold, the activated state is suitable for selection, but if the measured quality is less than the quality threshold, the deactivated state is selected;

[0023] - if the evaluated width is between the largest of the two intermediate thresholds and the maximum threshold, the state of the automatic maintenance function is selected according to the measured quality and the maximum authorized speed.

[0024] The invention also relates to a motor vehicle comprising means for detecting the edges of a traffic lane of a road that it is using, at least one actuator for controlling the motor vehicle, and a computer programmed to implement a controlling method as mentioned above.

[0025] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0026] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0027] On the attached drawings:

[0028] [Fig.l] is a schematic view of a motor vehicle suitable for implementing a method in accordance with the present invention;

[0029] [Fig.2] is a block diagram illustrating various steps of a method according to the present invention.

[0030] In [Fig.l], a motor vehicle 10 is shown which is suitable for implementing the invention.

[0031] This is a car. Alternatively, it could be another type of vehicle (truck, motorcycle, etc.).

[0032] Here, this vehicle 10 conventionally comprises a passenger compartment in which there are in particular a seat for the driver 20 of the vehicle and a steering wheel 12.

[0033] This vehicle 10 comprises a powertrain, a braking system and a steering system for turning the vehicle (not visible in the figure). Conventionally, the steering system comprises an electronically controllable power steering actuator, the powertrain comprises an electronically controllable engine control actuator, and the braking system comprises an electronically controllable braking actuator.

[0034] The vehicle 10 also comprises an electronic and / or computer processing unit (hereinafter called computer 11) comprising at least one microprocessor, at least one memory and input and output interfaces.

[0035] Thanks to its input interfaces, the calculator 11 is adapted to receive different input data which come from sensors or third-party calculators.

[0036] Among these sensors, for example, a device such as a front camera and / or a RADAR remote sensor and / or a LIDAR remote sensor is provided, making it possible to locate the edges of the traffic lane taken by the motor vehicle 10.

[0037] Thanks to its output interfaces, the computer 11 is adapted to control F power steering actuator, F engine control actuator, and F brake actuator.

[0038] Thanks to its memory, the computer 11 stores a computer application, consisting of computer programs comprising instructions whose execution by the computer allows the implementation of a function for automatically keeping the vehicle in the center of its traffic lane (hereinafter called the LCA function), and of the method described below.

[0039] In [Fig.l], the motor vehicle 10 is shown in perspective, when it is traveling on a traffic lane 31 of a road 30.

[0040] A traffic lane is herein defined as the portion of a road on which only one vehicle is permitted to travel at a time. Such a traffic lane is generally delimited between marking lines. In [Fig.l], there are two lateral marking lines 32, 34 delimiting the road, and a central marking line 33 delimiting the two traffic lanes.

[0041] A road (or carriageway) is defined as a set of traffic lanes. In the example considered here for illustrative purposes, this road 30 therefore has two traffic lanes 31 on which vehicles can travel in opposite directions.

[0042] The objective is to determine whether, given data that the calculator can raise, the LCA function can be activated or on the contrary if it must be deactivated for safety.

[0043] The following process is then implemented in a loop, with a small time step (of the order of a tenth of a second, for example). It comprises three main stages.

[0044] During a first step, the computer acquires data including the position of the edges of the traffic lane 31 taken by the motor vehicle 10 (hereinafter simply called “traffic lane 31”).

[0045] In practice, the camera or remote sensor used includes a processor which makes it possible to process the data it receives and to provide the computer 11 with “line equations” which illustrate the positions and shapes of the edges of the traffic lane 31, expressed in a reference frame attached to the motor vehicle.

[0046] Of course, the computer could perform these data processing operations itself.

[0047] At this stage, it could be considered that the data received by the computer 11 are exact and that the two line equations received clearly illustrate the shapes and positions of the marking lines 32, 33 which border the traffic lane 31.

[0048] However, for example because the central marking line 33 is erased or not very visible, it may happen that the calculator receives, instead of these two equations, the equations of the lateral marking lines 32, 34 (those which border the road 30 and not the traffic lane 31). It is understood that in this situation, the LCA function would bring the vehicle to the center of the road 30, straddling the two traffic lanes, which would be potentially dangerous.

[0049] This is the reason why the present invention proposes to attempt to detect whether the vehicle 10 is in such a situation (called an “undesirable situation”) in order to then block or interrupt the LCA function.

[0050] The idea behind this is to rely on three parameters to detect whether vehicle 10 is potentially in this undesirable situation.

[0051] So, during the first step, the calculator acquires other data, namely: - the width L of traffic lane 31 detected (we understand that in the event of a detection problem, the width will be that of road 30), - the quality of the road surface on Route 30, and - the maximum speed authorized on traffic lane 31 or, if this data is not available, the vehicle's speed regulation instruction.

[0052] The quality of the road surface and the maximum authorized speed are in fact data which, taken in combination with the width L of the detected traffic lane, make it possible to distinguish a secondary road in which there is a risk of poor detection of the edges of the traffic lane from a main road (national road, motorway, etc.) where this risk is considered zero.

[0053] Indeed, a good surface condition of the road surface and a high maximum authorized speed are generally representative of a main road (i.e. a road where the risk of the vehicle finding itself in the undesirable situation identified above is zero).

[0054] In practice, the width L is evaluated on the basis of the equations of the lines received. This width can be calculated at the vehicle level, in front of the latter, or by an average over a section of track several meters long.

[0055] The quality of the road surface on Route 30 could be acquired in different ways. It could be read from a database, taking into account the vehicle's geo-localized position, but it will preferably be measured.

[0056] It could be measured based on variations in the vehicle's suspension travel. Here, it will be measured differently.

[0057] In a known manner, to determine the speed of the vehicle 10, the rotational speed of each of its four wheels is measured. By applying a high-pass filter to the measurement signal of at least one of these rotational speeds, it is possible to obtain high-frequency components which are linked to the state of the road.

[0058] Thus, when these components exceed a predetermined threshold Sg, we can consider that the quality of the road surface 30 is poor. In this case, the value "one" is assigned to a Boolean variable BRF which is representative of the quality of the surface and which is stored in the memory of the computer 11 (BRF=1).

[0059] Otherwise, the road quality is considered good, so this variable remains equal to zero (BRF = 0).

[0060] The maximum speed allowed on the said road 30 can be obtained in various ways, for example by automatically reading the signs along the road, or in navigation software, taking into account the geolocated position of the vehicle.

[0061] When this data is not known, it is possible to rely on another data, namely the speed regulation setpoint of the motor vehicle. Indeed, when the LCA function is activated, an automatic or adaptive speed regulation function of the vehicle is generally also activated, so the setpoint is known.

[0062] Whatever the data used (maximum authorized speed or speed instruction), this data will subsequently be called maximum speed TpSp.

[0063] Taking into account all of this information, the computer 11 determines during a second step whether the LCA function can be activated (or maintained in the activated state if it was already activated), or whether it must be deactivated (or remain inactivated if it was already deactivated).

[0064] Whether the LCA function is activated or kept activated will depend on the outcome of this second step, but it could also depend on other third-party data (Is the vehicle in a built-up area? Is the weather good? etc.).

[0065] Therefore, the calculator determines during this second step the value of a status indicator.

[0066] This status indicator can take two values: - an LCA_OK value, in which case the LCA function is considered suitable for activation or maintenance in the activated state (its activation will also depend on the aforementioned third-party data), and - an LCA_NOK value, in which case the LCA function is disabled or kept in the disabled state (regardless of the aforementioned third-party data).

[0067] In this second step, the value of the status indicator is selected according to the evaluated width L. Depending on this width, it can also be selected according to the measured quality of the coating (i.e. the value of the BRF variable) and the said maximum speed TpSp.

[0068] The method for selecting either the LCA_OK or LCA_NOK status indicator values ​​is illustrated in [Fig.2].

[0069] This method involves several successive sub-steps.

[0070] To begin, the calculator 11 determines whether the evaluated width L is less than or equal to a minimum threshold Smin.

[0071] This minimum threshold Smin is less than 3 meters. Here it is 2.8m.

[0072] If the evaluated width L is less than or equal to this minimum threshold Smin, the calculator 11 deduces that the LCA function can be activated (the LCA_OK value is selected).

[0073] In fact, in this situation, we can consider that the detected traffic lane is so narrow that it necessarily corresponds to a single traffic lane.

[0074] Otherwise, the calculator determines whether the evaluated width L is less than or equal to a first intermediate threshold SL

[0075] This first intermediate threshold SI is less than 3.5 meters. Here it is 3.2m.

[0076] If the evaluated width L is between the minimum threshold Smin and this first intermediate threshold SI, the calculator determines the state of the LCA function based solely on the measured quality of the road surface 30.

[0077] In fact, in this situation, the detected traffic lane 31 is narrow and probably corresponds to a traffic lane of a secondary road, but it is estimated that there is nevertheless a minor risk that it is formed by two traffic lanes of a secondary road.

[0078] Here, to determine whether we are in an undesirable situation, we do not consider the maximum speed TpSp since, taking into account the width of the detected traffic lane, this speed is probably low so that this parameter is not not discriminating.

[0079] In practice, if the coating is of poor quality (BRF=1), the LCA_NOK value of the status indicator is selected to block the LCA function. Otherwise, the computer considers that the LCA function can be activated (the LCA_OK value of the status indicator is selected).

[0080] If the evaluated width L is not between the minimum threshold Smin and the first intermediate threshold SI, the calculator determines whether this width L is less than a second intermediate threshold S2.

[0081] This second intermediate threshold S2 is preferably greater than 3.5m but less than 4m. Here it is 3.8m.

[0082] If the evaluated width L is between the two intermediate thresholds SI, S2, the calculator selects the value of the status indicator based at least on the maximum speed TpSp.

[0083] In fact, given the width L, it is likely that the vehicle is driving on a main road and we are trying to check this.

[0084] In practice, if the maximum speed TpSp is higher than a speed threshold Sv (here 100 km / h), the calculator considers that the LCA function can be activated. In fact, it is then considered that it is very likely that the road is a motorway.

[0085] Otherwise, since it is not known what type of road the vehicle 10 is driving on, the computer 11 takes into account the quality of the road surface. Thus, if the surface is of poor quality (BRF=1), the LCA_NOK value of the status indicator is selected. It is considered that there is a risk of being in the undesirable situation identified above. On the contrary, if it is of good quality (BRF=0), the computer considers that the LCA function can be activated (the LCA_OK value of the status indicator is selected).

[0086] If the evaluated width L is greater than the second intermediate threshold S2, the calculator 11 checks whether this width L is less than a maximum threshold Smax.

[0087] This maximum threshold Smax is here 4 m.

[0088] If the evaluated width L is between the second intermediate threshold S2 and the maximum threshold Smax, it is likely that we are in a dangerous situation of poor detection of the lane edge lines. It is indeed rare to find traffic lanes so wide.

[0089] In this situation, to authorize the activation or maintenance in the activated state of the LCA function, the computer will check that the quality of the road surface is good and that the maximum speed TpSp is high. Otherwise, if at least one of these two conditions is not met, it will be considered that it is likely that the vehicle is in an undesirable situation identified above.

[0090] In practice, the calculator 11 first checks the quality of the road surface. If this last one is not of good quality (BRF=1), the LCA_NOK value of the status indicator is selected.

[0091] Otherwise, the computer checks whether the road is fast. If the maximum speed TpSp is lower than the speed threshold Sv, the value LCA_NOK of the status indicator is selected.

[0092] Otherwise, the vehicle is considered to be on a particularly wide main road, and the computer selects the LCA_OK value to enable activation of the LCA function.

[0093] Finally, if the calculator determines that the evaluated width L is greater than the maximum threshold Smax, it is considered that there is necessarily a detection error since no traffic lane is more than 4 meters wide.

[0094] In this case, the LCA_NOK value of the status indicator is selected.

[0095] Following this step and taking into account the third-party data acquired (weather, etc.), the status of the KLA function can be determined.

[0096] If the LCA function is deactivated, the driver must take charge of controlling the vehicle's direction, using the steering wheel 12.

[0097] On the other hand, if the LCA function is activated, the computer 11 controls, during a third step, the steering actuator of the motor vehicle 10 to keep the latter in the center of its traffic lane 31, taking into account the equations of the acquired lane edge lines (which are then considered reliable).

[0098] It should be noted in this regard that in the context of the driving aids considered in this presentation, the driver must already keep his hands on the steering wheel even when the LCA function is activated (the driver must maintain control of the vehicle, in particular with his eyes on the road and his hands on the steering wheel).

[0099] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0100] In particular, several thresholds can be used to judge the quality of the road surface on Route 30. Thus, the quality of the surface can be judged to be good (below a first threshold), degraded (between two thresholds), or very degraded (above the second threshold).

[0101] In this variant, the process will then be implemented in the same way as above, but the threshold considered will depend on the vehicle speed. Indeed, at low speed (typically under 50 km / h), we can suspect that the vehicle is driving in a built-up area and we then want the LCA function to only activate if we are certain that the lane edge lines have been detected. Taking the lower threshold into account therefore allows us to be more demanding.

Claims

Claims

1. Method for controlling a motor vehicle (10) traveling on a road (30) which comprises at least one traffic lane (31), comprising steps of: - detection of the edges of the traffic lane (31) taken by the motor vehicle (10), - selection by a computer (11) of the motor vehicle (10) of a state, activated (LCA_OK) or deactivated (LCA_NOK), of an automatic maintenance function of the motor vehicle (10) in said traffic lane (31), and - when the activated state is selected, control of at least one actuator for steering the motor vehicle (10) to keep it in said traffic lane (31), characterized in that: - in the detection step, a width (L) of said traffic lane is evaluated, and - in the selection step, the state of the automatic holding function is selected according to the evaluated width (L).

2. A driving method according to claim 1, wherein a step of measuring a quality of road surface (30) is provided and wherein, in the selection step, the state of the automatic holding function is selected according to the measured quality.

3. A driving method according to claim 1 or 2, in which a step of acquiring a maximum authorized speed on said road (30) is provided and in which, in the selection step, the state of the automatic maintenance function is determined as a function of said acquired maximum authorized speed.

4. Control method according to one of claims 1 to 3, in which a step of acquiring a speed regulation instruction for the movement of the motor vehicle is provided and in which, in the selection step, the state of the automatic holding function is selected as a function of said speed regulation instruction.

5. Control method according to one of claims 1 to 4, in which, if the evaluated width (L) is less than a minimum threshold (Smin), the activated state (LCA_OK) is suitable for being selected.

6. A control method according to one of claims 1 to 5, wherein, if the evaluated width (L) is greater than a maximum threshold (Smax), the disabled state (LCA_NOK) is selected.

7. Control method according to claims 5 and 6, in which, if the width (L) evaluated is between the minimum threshold (Smin) and the maximum threshold (Smax), the state of the automatic holding function is selected differently depending on whether: - the width (L) evaluated is between two intermediate thresholds (SI, S2) which are between the minimum threshold (Smin) and the maximum threshold (Smax), or that - the width (L) evaluated is less than the smallest of the two intermediate thresholds (SI), or that - the width (L) evaluated is greater than the largest of the two intermediate thresholds (S2).

8. Control method according to claims 2, 3 and 7, in which, when the width (L) evaluated is between the two intermediate thresholds (SI, S2): - if the maximum authorized speed is higher than a speed threshold (Sv), the activated state (LCA_OK) is suitable to be selected, - if the maximum authorized speed is lower than the speed threshold (Sv), the state of the automatic holding function is selected according to the measured quality.

9. Control method according to claims 2 and 7 or 8, in which, if the width (L) evaluated is between the minimum threshold (Smin) and the smallest of the two intermediate thresholds (SI): - if the measured quality is higher than a quality threshold (Sq), the activated state (LCA_OK) is suitable to be selected, - if the measured quality is lower than the quality threshold (Sq), the disabled state (LCA_NOK) is selected.

10. A driving method according to claims 2, 3 and 7 or 8 or 9, in which, if the width (L) evaluated is between the largest of the two intermediate thresholds (S2) and the maximum threshold (Smax), the state of the automatic holding function is selected according to the measured quality and the maximum authorized speed.

11. Motor vehicle (10) comprising means for detecting the edges of a traffic lane (31) of a road (30) which it is using and at least one actuator for controlling the motor vehicle (10), characterized in that it comprises a computer (11) programmed to implement a control method in accordance with one of the claims previous instructions.

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