Method for maintaining a vehicle in the center of its lane of travel - Patents.com

Abstract

The present invention relates to a method for steering a motor vehicle (10) traveling on a road (30) having at least one travel lane (31), the method comprising the steps of: detecting the side edges of the travel lane of the motor vehicle; selecting, by a computer (11) of the motor vehicle, an active or inactive state of a function for automatically keeping the motor vehicle in the travel lane; and, when the active state is selected, controlling at least one steering actuator of the motor vehicle to keep the motor vehicle in the travel lane. According to the present invention, in the detection step, a width (L) of the travel lane is determined; and in the selection step, the state of the function for automatically keeping the motor vehicle in the travel lane is selected depending on the determined width.

Description

[Technical Field]

[0001] The present invention relates generally to driver assistance systems for motor vehicles.

[0002] The invention more precisely relates to a method for steering a motor vehicle traveling on a road comprising at least one driving lane, comprising: - detecting the side edges of a travel lane used by the motor vehicle; - selecting, using a computer of the motor vehicle, an activation or deactivation state of a feature for automatically maintaining the motor vehicle within the driving lane; and then - when an active state is selected, controlling at least one steering actuator of the motor vehicle to maintain the vehicle within the travel lane; The present invention relates to a method comprising:

[0003] The invention further relates to a motor vehicle adapted to carry out said method.The invention applies more particularly to cars and other motor vehicles travelling on roads. [Background technology]

[0004] To increase the safety of motor vehicles, they are now being equipped with driver assistance systems and even systems for highly automated driving.

[0005] These systems are typically systems for keeping the vehicle in its lane, i.e., systems for keeping the vehicle within the confines of the lane or keeping the vehicle in the center of the lane (more commonly known by the acronym LKA for Lane Keeping Assist or LCA for Lane Centering Assist).

[0006] To operate, such systems need to know the location of the side edge of the travel lane that the vehicle is using. Currently, it is known to accomplish this by using sensors, such as cameras, that incorporate image processing means to determine the location of this lane edge.

[0007] It can be seen that detection of the side edges of the travel lane needs to be extremely reliable in order to prevent the vehicle from leaving the lane.

[0008] Unfortunately, the above detection is not always entirely sufficient.

[0009] In fact, applicant has been able to determine that on some narrow, two-way, secondary roads ("country roads"), the two lines marking the side edges of the roadway are classified as forming the side edges of the travel lanes. In this situation, it can be seen that a vehicle will be steered not toward its own travel lane but toward the center of the road itself, to the extent that it straddles the two lanes, which is undesirable (because the driver must put their hands on the steering wheel to correct the vehicle's trajectory). Summary of the Invention

[0010] In order to overcome the aforementioned drawbacks of the prior art, the present invention proposes to rely on at least one parameter (the detected width of the driving lane) to check that the data on which the function for automatically keeping the vehicle in the center of the driving lane relies is reliable.

[0011] More particularly, the invention proposes a steering method as defined in the preamble, - in the detection step, a width of the travel lane is determined; In a selection step, the state of a function for automatically keeping the vehicle within the driving lane is selected according to the determined width.

[0012] This allows the invention to contribute to deactivating the function that automatically keeps the vehicle in the center of the driving lane if the width of the driving lane has a value that is unexpected in itself or taking into account other parameters collected by the vehicle, in order to prevent the driver from having to correct the vehicle's trajectory imposed by the actuators.

[0013] Other advantageous, non-limiting features of the steering method according to the invention, taken individually or in any technically possible combination, are the following: - measuring the surface quality of the road; - in a selection step, a state of a function for automatically keeping the motor vehicle within a driving lane is selected according to the measured quality; - obtaining a maximum permitted speed for said road; - in a selection step, a state of a function for automatically keeping the motor vehicle in a driving lane is determined according to the obtained maximum permissible speed; - obtaining a travel speed limit set point for the motor vehicle; - in a selection step, a state of a function for automatically maintaining the motor vehicle within a driving lane is selected in accordance with the driving speed limit setpoint; - if the determined width is less than the minimum threshold, the operating state is suitable for selection; If the determined width exceeds the maximum threshold, the inactive state is selected; - if the determined width is between the minimum and maximum thresholds, the state of the function for automatically keeping the motor vehicle within the driving lane is selected depending on whether the determined width is between two intermediate thresholds between the minimum and maximum thresholds, whether the determined width is less than the lower of the two intermediate thresholds, or whether the determined width is greater than the higher of the two intermediate thresholds; - if the determined width is between two intermediate thresholds, an operating state is suitable for selection if the maximum permissible speed exceeds the speed threshold, but if the maximum permissible speed is below the speed threshold, the state of the function for automatically keeping the motor vehicle in the driving lane is selected according to the measured quality; - when the determined width is between the minimum threshold and the lower of two intermediate thresholds, if the measured quality exceeds the quality threshold, the active state is suitable for selection, but if the measured quality is lower than the quality threshold, the inactive state is selected; - if the determined width is between the higher of the two intermediate thresholds and the maximum threshold, the state of the function for automatically keeping the motor vehicle in the driving lane is selected according to the measured quality and the maximum permissible speed.

[0014] The invention further relates to a motor vehicle comprising means for detecting the side edges of the driving lane of the road in use, at least one steering actuator of the motor vehicle, and a computer programmed to carry out the above-mentioned steering method.

[0015] Of course, the various features, variations, and embodiments of the invention can be combined with one another in various combinations, unless they are inconsistent or mutually exclusive.

[0016] The following description, with reference to the accompanying drawings given as non-limiting examples, clearly explains the essence of the invention and how it can be put into practice. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a motor vehicle suitable for carrying out the method according to the invention; [Figure 2] 1 is a block diagram showing the various steps of the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 illustrates a motor vehicle 10 suitable for implementing the present invention.

[0019] Here, the motor vehicle is a passenger car. Alternatively, the motor vehicle may be another type of vehicle (truck, motorcycle, etc.).

[0020] In this case, the vehicle 10 is conventionally provided with a passenger compartment, which in particular houses a seat for a driver 20 of the vehicle and a steering wheel 12 .

[0021] The vehicle 10 includes a powertrain, a braking system, and a steering system (not shown) that can be used to turn the vehicle. Typically, the steering system includes an electrically controlled assisted steering actuator, the powertrain includes an electrically controlled engine control actuator, and the braking system includes an electrically controlled brake actuator.

[0022] The vehicle 10 further comprises an electronic and / or computer processing unit (hereinafter referred to as computer 11) comprising at least one microprocessor, at least one memory and input and output interfaces.

[0023] By means of the input interface, the computer 11 is adapted to receive various input data coming from sensors or external computers.

[0024] Among these sensors are provided, for example, devices such as forward-facing cameras, radar remote sensors, and / or lidar remote sensors that are used to determine the location of the side edges of the travel lane used by the motor vehicle 10.

[0025] By means of the output interface, the computer 11 is adapted to control assisted steering actuators, engine control actuators and braking actuators.

[0026] The memory allows the computer 11 to store a computer application consisting of a computer program including instructions that, when executed by the computer, enable the computer to perform a function for automatically keeping the vehicle in the center of the driving lane (hereinafter referred to as the LCA function) and the method described below.

[0027] FIG. 1 shows a perspective view of a motor vehicle 10 traveling in a driving lane 31 of a road 30 .

[0028] A travel lane is defined as a section of road where only one vehicle can travel at a time. Such a travel lane is generally defined between marker lines. In Figure 1, there are two side marker lines 32, 34 that define the road, and one center marker line 33 that defines the two travel lanes.

[0029] A road (or roadway) is itself configured as a set of travel lanes. Thus, in the example considered here as illustrative, the road 30 comprises two travel lanes 31 along which vehicles can travel in opposite directions.

[0030] The objective is to take into account the data that the computer can collect and determine whether the LCA function can be activated or, conversely, whether it needs to be deactivated for safety reasons.

[0031] So the following method is performed in a continuous loop with reduced time steps (for example on the order of a tenth of a second): The method comprises three main steps.

[0032] In a first step, the computer obtains data including the positions of the side edges of the driving lane 31 used by the motor vehicle 10 (hereinafter simply referred to as "driving lane 31").

[0033] In practice, the camera or remote sensor used will have a processor that is used to process the data received and provide the computer 11 with a "line equation" that describes the position and shape of the side edge of the travel lane 31, the line equation being expressed in a coordinate system associated with the motor vehicle.

[0034] Of course, a computer can also perform these data processing tasks itself.

[0035] At this stage, the data received by the computer 11 can be considered accurate, and the two received linear equations can be considered to accurately represent the shape and position of the marking lines 32, 33 that border the driving lane 31.

[0036] However, instead of those two equations, the computer may receive equations for the side marking lines 32, 34 (the side marking lines that border the road 30, but not the driving lane 31), for example because the center marking line 33 is faded or poorly visible. In this situation, the LCA function will bring the vehicle to the center of the road 30, which straddles the two driving lanes, which it knows is potentially dangerous.

[0037] To that end, the present invention proposes to try to detect whether the vehicle 10 is in such a situation (called an "unfavorable situation") and to prevent or interrupt the LCA function in the event of an unfavorable situation.

[0038] The idea here is to rely on three parameters to detect whether the vehicle 10 is potentially in this undesirable situation.

[0039] Thus, in a first step, the computer acquires other data, namely: the width L of the detected driving lane 31 (in the case of a detection abnormality, it turns out that the width is the width of the road 30); - Surface quality of road 30, and - The maximum permitted speed in the travel lane 31, or if this data is not available, the vehicle's speed limit set point. is.

[0040] This is because the road surface quality and maximum permissible speed, combined with the detected travel lane width L, provide data that can be used to distinguish secondary roads, where there is a risk of insufficient travel lane edge detection, from major roads (national highways, freeways, etc.), where this risk is considered to be zero.

[0041] This is because good surface conditions and high maximum permitted speeds generally represent highways (ie roads where there is no risk of a vehicle encountering the unfavourable conditions defined above).

[0042] In practice, the width L is determined based on the linear equation received: this width can be calculated at the vehicle's position, in front of the vehicle, or as an average over a section of the lane several meters in length.

[0043] The surface quality of the road 30 can be obtained in various ways: it can be read from a database taking into account the geolocated position of the vehicle, but is preferably measured.

[0044] The surface quality can be measured by the change in the throw of the vehicle's suspension, where the surface quality is measured in another way.

[0045] In known manner, the rotational speed of each of the vehicle's four wheels is measured to determine the speed of the vehicle 10. By applying a high-pass filter to the measurement signal of at least one of these rotational speeds, high frequency components related to the road conditions can be obtained.

[0046] Thereby, when these components exceed a predetermined threshold Sg, the surface quality of the road 30 can be considered to be below average, in which case the value "1" is assigned to the Boolean value BRF representing the surface quality, and this value is stored in the memory of the computer 11 (BRF=1).

[0047] Otherwise, the road quality is evaluated as good, and as a result this variable remains zero (BRF=0).

[0048] The maximum permitted speed for the road 30 may itself be obtained in various ways, for example by automatically reading signs lining the road, or by navigation software taking into account the vehicle's geolocated position.

[0049] If this data is not known, it is possible to rely on another data, namely the vehicle's speed limit set point, since activating the LCA function typically also activates a function that automatically or adaptively limits the vehicle's speed, and thus the set point is known.

[0050] Whatever data is used (maximum allowable speed or speed set point), this data will be referred to hereafter as maximum speed TpSp.

[0051] Taking all this information into account, in a second step the computer 11 decides whether the LCA function can be activated (or if it is already activated, whether to keep it activated) or whether the LCA function needs to be deactivated (or if it is already deactivated, whether to keep it deactivated).

[0052] Whether the LCA function is activated or kept activated depends on the outcome of this second step, but may also depend on other external data (is the vehicle in a city? Is the weather clear? etc.).

[0053] As a result, the computer determines the value of the condition indicator in this second step.

[0054] This status indicator has two values: - the value LCA_OK, in which case the LCA function is considered suitable for activation or for being kept activated (the activation of the LCA function also depends on the aforementioned external data), - the value LCA_NOK, in which case the LCA function is deactivated or kept deactivated (regardless of the external data mentioned above) Take.

[0055] In this second step, the value of the condition index is selected according to the determined width L. Depending on this width, its value may also be selected according to the measured quality of the surface (i.e. the value of the variable BRF) and the maximum speed TpSp.

[0056] The method for selecting one or the other of the status indicator values ​​LCA_OK and LCA_NOK is shown in FIG.

[0057] The method comprises a number of successive sub-steps.

[0058] First, the computer 11 determines whether the obtained width L is equal to or smaller than the minimum threshold value Smin.

[0059] This minimum threshold Smin is less than 3 meters. Here, the minimum threshold is 2.8 m.

[0060] If the determined width L is less than or equal to this minimum threshold Smin, the computer 11 presumes that the LCA function can be activated (the value LCA_OK is selected).

[0061] This is because in this situation the detected driving lane can be considered narrow enough to necessarily correspond to a single driving lane.

[0062] If not, the computer determines whether the determined width L is less than or equal to a first intermediate threshold value S1.

[0063] This first intermediate threshold S1 is less than 3.5 meters, here the threshold is 3.2 m.

[0064] If the determined width L is between the minimum threshold Smin and this first intermediate threshold S1, the computer determines that the state of the LCA function depends solely on the measured quality of the road 30 surface.

[0065] This is because in this situation the detected driving lane 31 is narrow and probably corresponds to one driving lane of a secondary road, however there is a slight risk that the driving lane 31 is formed by two driving lanes of a secondary road.

[0066] In this case, the maximum speed TpSp is not taken into account to determine whether the vehicle is in an unfavorable situation, since, taking into account the width of the detected driving lane, this speed is likely to be low and therefore cannot be determined by this parameter.

[0067] In practice, if the surface is of insufficient quality (BRF=1), the condition indicator value LCA_NOK is selected to prevent the LCA function, otherwise the computer considers that the LCA function can be activated (condition indicator value LCA_OK is selected).

[0068] If the determined width L is not between the minimum threshold Smin and the first intermediate threshold S1, the computer determines whether the width L is less than a second intermediate threshold S2.

[0069] This second intermediate threshold S2 is preferably greater than 3.5 m but less than 4 m, here the threshold is 3.8 m.

[0070] If the determined width L is between the two intermediate thresholds S1 and S2, the computer first selects the value of the state index according to the maximum speed TpSp.

[0071] This is because, considering the width L, it is highly likely that the vehicle is traveling on a main road, and this is what we want to verify.

[0072] In fact, if the maximum speed TpSp exceeds the speed threshold Sv (here 100 km / h), the computer considers that the LCA function can be activated, since in that case there is a high probability that the road is a freeway.

[0073] Otherwise, since the type of road on which the vehicle 10 is traveling is unknown, the computer 11 takes into account the surface quality of the road. If the surface is of insufficient quality (BRF=1), then the condition indicator value LCA_NOK is selected, since it is considered that the vehicle is at risk of being in an unfavorable situation as defined above. Conversely, if the surface is of good quality (BRF=0), the computer considers that the LCA function can be activated (the condition indicator value LCA_OK is selected).

[0074] If the determined width L exceeds the second intermediate threshold S2, the computer 11 checks whether this width L is less than the maximum threshold Smax.

[0075] Here, this maximum threshold is 4m.

[0076] If the determined width L is between the second intermediate threshold S2 and the maximum threshold Smax, the vehicle may be in a dangerous situation related to insufficient detection of the lane side edge lines, since such wide driving lanes are rarely encountered.

[0077] In this situation, to allow the LCA function to be activated or kept activated, the computer checks that the roadway quality is good and the maximum speed TpSp is high. Otherwise, if at least one of these two conditions is not met, it is considered that the vehicle may be in an unfavorable situation as defined above.

[0078] In practice, the computer 11 first checks the quality of the roadway: if the roadway is not of good quality (BRF=1), the condition indicator value LCA_NOK is selected.

[0079] If not, the computer checks whether the vehicle is on a highway. If the maximum speed TpSp is less than the speed threshold Sv, the state indicator value LCA_NOK is selected.

[0080] Otherwise, the vehicle is considered to be on a particularly wide highway and the computer selects the value LCA_OK which allows the LCA function to be activated.

[0081] Finally, if the computer determines that the determined width L exceeds the maximum threshold Smax, then it can infer that there must be a detection error, since no driving lane is wider than 4 meters.

[0082] In that case, the state indicator value LCA_NOK is selected.

[0083] Following this step, the state of the LKA function can be determined taking into account acquired external data (weather, etc.).

[0084] When the LCA function is disabled, the driver must take responsibility for controlling the steering of the vehicle using the steering wheel 12.

[0085] On the other hand, if the LCA function is activated, in a third step, the computer 11 takes into account the obtained lane side edge line equation (in which case the equation is deemed reliable) and controls the steering actuator of the vehicle in order to keep the vehicle 10 in the center of its driving lane 31.

[0086] In this regard, it should be noted that within the scope of the driving assistance envisaged in this description, even when activating the LCA function, the driver must keep his hands on the steering wheel beforehand (the driver must in particular keep his eyes on the road and his hands on the steering wheel to maintain control of the vehicle).

[0087] The invention is in no way limited to the embodiments described and shown, but those skilled in the art can introduce any of the variants according to the invention into the invention.

[0088] In particular, it is possible to use multiple thresholds to assess the quality of the surface of the road 30. That is, the surface quality could be assessed as good (below a first threshold), degraded (between two thresholds) or very degraded (above a second threshold).

[0089] In this variant, the method is carried out in the same way as above, but the threshold value considered depends on the speed of the vehicle, since at low speeds (usually below 50 km / h) it is possible to detect that the vehicle is driving in a city area, and in that case it is desirable to activate the LCA function only if it is certain that the lane side edge lines have been correctly detected. Considering a minimum threshold value allows more demands to be made.

Claims

1. A method for steering a motor vehicle (10) traveling on a road (30) having at least one travel lane (31), comprising: - detecting the side edges of the lane of travel (31) used by the motor vehicle (10); - selecting, by means of a computer (11) of said motor vehicle (10), an activated state (LCA_OK) or deactivated state (LCA_NOK) of a function for automatically keeping said motor vehicle (10) in said driving lane (31); - when said operating state is selected, controlling at least one steering actuator of said motor vehicle (10) to keep said motor vehicle within said travel lane (31); In a method comprising: In the detection step, the width (L) of the driving lane is determined, In the selection step, the state of the function for automatically maintaining the motor vehicle within the driving lane is selected according to the determined width (L). A steering method comprising:

2. 2. The steering method of claim 1, further comprising the step of measuring a surface quality of the road (30), wherein in the selecting step, the state of the function for automatically maintaining the motor vehicle within the driving lane is selected in accordance with the measured quality.

3. 3. The steering method according to claim 1, further comprising the step of obtaining a maximum permissible speed on the road (30), wherein in the selecting step, the state of the function for automatically maintaining the motor vehicle within the driving lane is determined in accordance with the obtained maximum permissible speed.

4. 4. The steering method according to claim 1, further comprising the step of obtaining a driving speed limit set point for the motor vehicle, wherein in the selecting step, the state of the function for automatically maintaining the motor vehicle within the driving lane is selected in accordance with the driving speed limit set point.

5. 5. Steering method according to any one of claims 1 to 4, wherein the operating state (LCA_OK) is suitable for selection if the determined width (L) is less than a minimum threshold value (Smin).

6. 6. Steering method according to any one of claims 1 to 5, wherein the inactive state (LCA_NOK) is selected if the determined width (L) exceeds a maximum threshold value (Smax).

7. If the determined width (L) is between the minimum threshold (Smin) and the maximum threshold (Smax), the state of the function for automatically maintaining the motor vehicle within the driving lane is: whether the determined width (L) is between two intermediate thresholds (S1, S2) between the minimum threshold (Smin) and the maximum threshold (Smax), or whether said determined width (L) is less than the lower of said two intermediate thresholds (S1); or - whether the determined width (L) exceeds the higher of the two intermediate thresholds (S2); 7. The steering method according to claim 5, wherein the steering is selected depending on the condition.

8. When the determined width (L) is between the two intermediate thresholds (S1, S2), - if said maximum permissible speed exceeds a speed threshold (Sv), said operating state (LCA_OK) is suitable for selection, if the maximum permissible speed is below the speed threshold (Sv), the state of the function for automatically keeping the motor vehicle in the driving lane is selected according to the measured quality; A steering method according to claim 2, 3 or 7.

9. If the determined width (L) is between the minimum threshold (Smin) and the lower of the two intermediate thresholds (S1), - if the measured quality exceeds a quality threshold (Sq), the operating state (LCA_OK) is suitable for selection, If the measured quality is lower than the quality threshold (Sq), the inactive state (LCA_NOK) is selected, 9. A steering method according to claim 2, 7 or 8.

10. 10. A steering method according to claim 2, 3, 7, 8 or 9, wherein if the determined width (L) is between the higher of the two intermediate thresholds (S2) and the maximum threshold (Smax), the state of the function for automatically keeping the motor vehicle within the driving lane is selected in accordance with the measured quality and the maximum permissible speed.

11. A motor vehicle (10) comprising means for detecting the side edge of a driving lane (31) of a road (30) in use and at least one steering actuator of the motor vehicle (10), characterized in that the motor vehicle (10) comprises a computer (11) programmed to carry out the steering method according to any one of claims 1 to 10.

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