Method of steering a vehicle within its lane of travel

Abstract

The invention relates to a method for steering a motor vehicle (10) traveling in a lane (31) of a road (30), comprising the steps of: - acquiring the edge lines (33, 35) of said lane, - determining a centerline (T0), - acquiring a lateral deviation (y) between the motor vehicle and the centerline, - calculating a steering command for the motor vehicle, and - controlling a steering actuator of said vehicle by the computer (11). According to the invention, when two conditions are met, namely: - that a driver (40) of the vehicle exerts an action to command a deviation of the vehicle from said centerline and then ceases this action, and - that, at the moment of cessation of said action, the lateral deviation is greater than a deviation threshold, said steering command is determined so that the motor vehicle follows a lateral line offset laterally from the centerline. Figure for the abstract: Fig.1.

Description

Title of the invention: Method for steering a vehicle in its lane of travel 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 piloting a motor vehicle travelling on a lane of a road, comprising the steps of: - acquiring data relating to the edge lines of said lane, - determining a median line of said lane taking into account said data, - acquisition of a lateral deviation between the motor vehicle and the median line, - calculation, by a computer embedded in said motor vehicle, of a driving instruction for the motor vehicle as a function of said median line, and - control by the computer of a steering actuator of said motor vehicle, according to said control instruction.

[0003] The invention also relates to a motor vehicle adapted to implement such a method. It applies more particularly to cars and other motorized vehicles traveling on roads. State of the art

[0004] In order to improve the safety of motor vehicles, they are currently being equipped with driver assistance systems or even highly automated driving systems.

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

[0006] Such a system requires, in order to function, knowledge of the position of the edges of the lane traveled 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 each of the lane edge markings.

[0007] A computer on board the vehicle can then deduce the position of the median line of the lane being traveled, which allows it to automatically control the vehicle so that it follows this median line.

[0008] It may happen, for various reasons, that the driver uses the steering wheel to shift the vehicle away from this centerline. This is typically the case when he wants to move to the right of his lane because he is going to cross a particularly wide vehicle traveling in the opposite lane, to his left.

[0009] During such a shift, the LCA function allows the vehicle to shift and does not deactivate completely, except under certain conditions, for example if the vehicle leaves its lane of travel.

[0010] Thus, as soon as the driver stops turning the steering wheel to shift the vehicle, the LCA function is designed to reactivate and bring the vehicle back along the centerline.

[0011] However, this solution is not entirely satisfactory for the driver, particularly when the latter wishes the vehicle to remain offset from the median line for a longer period. Presentation of the invention

[0012] In order to remedy the aforementioned drawback of the prior art, the present invention proposes, under certain conditions, to allow the vehicle to automatically follow a trajectory offset from the median line (i.e. a trajectory parallel to this median line but offset by a non-zero distance).

[0013] More specifically, the invention proposes a method as defined in the introduction, in which it is further provided: - to verify if two conditions are met, namely: (i) that a driver of the motor vehicle exerts an action on an interface of the motor vehicle to command a shift of the motor vehicle from said centerline and then ceases this action, and ii) that, at the time he ceases said action, the lateral deviation is greater than a deviation threshold, then - if these conditions are met, to determine the said driving instruction in such a way that the motor vehicle follows a lateral line offset laterally from the median line.

[0014] Thus, thanks to the invention, when the driver exerts an action on the steering of the vehicle to shift it from the median line and this action can be interpreted as meaning that the driver wants the vehicle to remain shifted from the median line, the computer steers the vehicle to follow a line distant from the median line.

[0015] In other words, the vehicle does not immediately return to the centerline as soon as the driver releases their steering input. Thus, the driver is not forced to hold the steering wheel to keep the vehicle offset from the centerline.

[0016] Preferably, the computer is programmed to bring the vehicle back towards this median line later, after a predetermined duration of several seconds.

[0017] The offset trajectory that the vehicle follows during these few seconds is preferably determined according to the configuration of the traffic lane, so that it does not vary or varies little from one time to another, which gives the driver a feeling of confidence.

[0018] Therefore, when the driver shifts the vehicle from the median line so that it follows a first trajectory and then the computer takes over and follows a second trajectory offset from the median line, the two trajectories may be laterally offset from each other (the lateral differences between these trajectories and the median line may be different).

[0019] Other advantageous and non-limiting features of the piloting method according to the invention, taken individually or in all technically possible combinations, are as follows: - said driving instruction is determined so that the motor vehicle follows the lateral line only if said lateral deviation has remained, while the driver was performing said action, above said deviation threshold for a period exceeding a time threshold; - said threshold of deviation is determined according to an effective width of the traffic lane; - said threshold of deviation is determined according to a usable width of the traffic lane, said usable width being calculated according to the effective width, a width of the motor vehicle, and a safety margin; - said safety margin varies depending on the speed and / or acceleration of the motor vehicle; - when both conditions are met, the said driving instruction is determined so that the motor vehicle follows the lateral line for a determined time, then the said driving instruction is determined so that the motor vehicle returns towards the median line; - said determined duration has a reference value of several seconds; - said determined duration has a value that can be modified by the driver using an interface embedded in the motor vehicle; - when both conditions are not met, the said driving instruction is determined so that the motor vehicle follows the median line; - a step is planned to acquire values ​​for parameters relating to the dynamics of the motor vehicle and its position in said traffic lane, one of said parameters being the lateral deviation, then the steering command is calculated by means of a controller, depending on the acquired values ​​and reference values ​​of said parameters, the reference value of the lateral deviation being chosen to be zero so that the motor vehicle follows the median line, or non-zero so that the motor vehicle follows the lateral line.

[0020] The invention also relates to a motor vehicle comprising: - suitable acquisition methods for acquiring, when the motor vehicle is moving on a traffic lane, data relating to the edge lines of said traffic lane, - a steering actuator adapted to steer the motor vehicle, and - a computer programmed to implement a control process as described above.

[0021] Of course, the various features, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0023] On the attached drawings:

[0024] [Fig-1] is a schematic perspective view of a motor vehicle adapted to implement a process in accordance with the invention;

[0025] [Fig.2] is a schematic top view of the motor vehicle of [Fig.1] driving on a road;

[0026] [Fig.3] represents a functional diagram of the calculations for implementing a process piloting according to the invention;

[0027] [Fig.4] is a schematic top view of a traffic lane of the road [Fig.2];

[0028] [Fig.5] is a diagram illustrating steps in the implementation of the piloting process according to the invention;

[0029] [Fig.6] represents three graphs illustrating the variations over time of pa ramers used in the process of [Fig.5], in a first configuration;

[0030] [Fig.7] represents three graphs illustrating the variations over time of pa ramers used in the process of [Fig.5], in a second configuration.

[0031] In [Fig.1], a motor vehicle 10 adapted to implement the invention is shown.

[0032] This refers to a car. Alternatively, it could be another type of vehicle (truck, motorcycle...).

[0033] In this figure, the motor vehicle 10 is travelling on a traffic lane 31 of a road 30. It can be seen that the road 30 has two lateral marking lines 34, 35 (which delimit it) and a central marking line 33 delimiting two traffic lanes 31, 32.

[0034] A traffic lane is defined here as the part 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.

[0035] A road (or carriageway) is defined as a set of traffic lanes. In the example considered here for illustrative purposes, this road 30 therefore comprises two traffic lanes 31 on which vehicles can travel in the same direction.

[0036] The median line T0 of the traffic lane will be defined as the geometric curve extending along the center of the traffic lane 31, at an equal distance from the two lateral marking lines 34, 35.

[0037] As shown in [Fig.1], the motor vehicle 10 conventionally comprises a chassis, front steering wheels 13 and rear non-steering wheels 14, a passenger compartment in which there is in particular a seat for the driver 40 of the vehicle.

[0038] The passenger compartment also houses an interface allowing the driver to control the vehicle so that it turns from one side to the other. Typically, this interface could be a steering wheel, but alternatively, a joystick could be used.

[0039] This motor vehicle 10 conventionally comprises a powertrain, a braking system, and a steering system for turning the vehicle. Conventionally, the steering system comprises an electronically controlled power steering actuator, the powertrain comprises an electronically controlled engine control actuator, and the braking system comprises an electronically controlled brake actuator.

[0040] The motor vehicle 10 also includes 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.

[0041] Thanks to its input interfaces, the computer 11 is adapted to receive various input data which come from third-party sensors or computers.

[0042] Among these sensors, a front camera is provided, for example, to detect the edges of the traffic lane 31 being used. Sensors adapted to determine the values ​​of other parameters mentioned later, relating to the position of the vehicle in its traffic lane, the traffic lane itself, and the vehicle's dynamics are also provided.

[0043] Thanks to its output interfaces, the computer is adapted to control the power steering actuator, the engine control actuator, and the braking actuator.

[0044] Thanks to these interfaces, the computer can also communicate with a touch screen 15 in order to display data or to allow the driver 40 of the vehicle to enter information.

[0045] Thanks to its memory, the computer stores a computer application, consisting of computer programs including instructions whose execution by the computer allows the implementation of an automatic vehicle lane keeping function (hereafter referred to as LCA function), and more generally of the process described below.

[0046] Before describing this process in more detail, we can introduce the different variables that will be used, some of which are illustrated in [Fig.2].

[0047] The total mass of the motor vehicle shall be denoted “m” and shall be expressed in kg.

[0048] The center of gravity of the vehicle will be noted as "CG".

[0049] The mass of the vehicle acting on the front wheel assembly will be noted as "Mf" and will be expressed in kg.

[0050] The mass of the vehicle acting on the rear wheel assembly will be noted as "Mr" and will be expressed in kg.

[0051] The wheelbase of the vehicle, that is to say the distance between the axes of these two sets of wheels, shall be noted "L" and shall be expressed in meters.

[0052] The pneumatic rigidity of the rear wheels will be noted Cr and will be expressed in Newton / rad.

[0053] The pneumatic rigidity of the front wheels will be noted Cf and will be expressed in Newton / rad.

[0054] An orthogonal coordinate system (CG, X, Y, Z) attached to the vehicle can be considered. Its origin coincides with the center of gravity CG. The X-axis corresponds to the longitudinal axis of the vehicle. The Y-axis corresponds to the lateral axis of the vehicle, oriented to the left. When the vehicle is traveling on a horizontal road, the Z-axis corresponds to the vertical axis. More generally, this Z-axis is the axis normal to the road.

[0055] The steering angle that the front steering wheels make with the longitudinal axis X of the motor vehicle 10 will be noted "ô" and will be expressed in rad.

[0056] It should be noted that the steering wheel angle and the steering angle ô are directly related, with a gear ratio and even a first- or second-order dynamic. In the following, we will only consider the steering angle ô at the wheels.

[0057] The steering speed of the front wheels will be noted as “dô / dt”.

[0058] The longitudinal speed of the vehicle, along the X-axis, will be denoted v and will be expressed in m / s.

[0059] The relative angle of heading between the X-axis and the tangent to the median line T0 at the level of the The center of gravity CG will be denoted "W" and will be expressed in rad.

[0060] The yaw rate of vehicle 1, that is to say its rotational rate around the Z axis, shall be denoted “drp / dt”.

[0061] The lateral position error, also called lateral deviation, between the center of gravity CG of the vehicle and the midline T0 will be denoted y (see [Fig.4]).

[0062] The lateral speed of the vehicle will be noted as “dy / dt”.

[0063] At this stage, we can also introduce a notion of "position error integral", which corresponds to the time integral of the lateral deviations y with respect to the median line T0. This error integral will be denoted "Jy.dt".

[0064] The curvature of the median line is denoted p (in m')• This is the inverse of its radius of curvature at the center of gravity CG of the motor vehicle 10.

[0065] The method of piloting the motor vehicle 10 is intended to allow this vehicle to follow the median line T0 of the traffic lane, in autonomous mode (without intervention from the driver).

[0066] This process is implemented when the LCA function is activated.

[0067] The method of activating this function will not be described here.

[0068] On the other hand, it will be possible to describe how the vehicle is kept in its lane 31 when the LCA function is activated.

[0069] To establish the vehicle control law and thus regulate the steering angle ô of the motor vehicle 10 so that the latter remains centered on its median line T0, this vehicle was modeled through a bicycle model.

[0070] In such a model, the two wheels of the front axle are considered to be one and the same, and the same applies to the two rear wheels. The vehicle chassis is modeled by a body that connects the two wheel models.

[0071] The dynamics of the motor vehicle 10 are then represented by a state vector X, which is expressed here in the form:

[0072] [Math.l] tdy) I dt\ dy / dt dô / dt ô i I

[0073] It will be recalled here that the lateral deviation y corresponds to the distance between the centre of gravity CG of the vehicle and the median line T0.

[0074] The equation of this median line is in practice determined on the basis of the equations representing the marking lines 33, 35 which delimit this lane of traffic 31.

[0075] According to the "bicycle" model used, the equation of the system can be written in the following form:

[0076] [Math.2] X = AX + B & Oh f bk + Y-CX

[0077] In this equation, the term ôFBK is a first component of the steering angle command ô which will be transmitted to the power steering actuator. As will become clearer below, this component allows the vehicle to be kept in the center of the traffic lane 31, assuming that the lane is straight.

[0078] A, C, Bô and Bp are determined matrices and vectors.

[0079] The first of the Math2 equations then introduces two terms, one an open-loop term Bp.p and the other a closed-loop term Bô.ôfbk. The open-loop term is intended to compensate for the steering angle ô by taking into account the curvature of the median line T0. The closed-loop term allows the steering angle to be calculated assuming that the traffic lane is straight.

[0080] Y represents the measurement vector, and therefore depends on the state X.

[0081] With reference to [Fig.3], the topology of an example LCA system has been schematically represented by a block diagram.

[0082] This block diagram includes a closed loop 25 and an open loop 21.

[0083] The open loop 21a is designed to take into account the curvature of the road and to compensate for the effect of the turn on the states and the control.

[0084] The closed loop 25 has the function of keeping the vehicle in the center of its traffic lane when the latter is considered straight, that is to say rectilinear.

[0085] We therefore find the two terms introduced above.

[0086] The terms from these two loops, namely the components ôFBK and ôFFD, are added together by means of a summing 27.

[0087] The steering angle ô to be transmitted to the front wheel for the vehicle 1 to move in a turn having a known curvature p thus depends on the two preceding components, so that we can write:

[0088] [Math.3] Oh req — Op BK + S FFD

[0089] On [Fig.3], the state of vehicle 1 is represented by element 22. This element therefore represents the vehicle, with its sensors, its actuators... A set of measured data emerges from this element 22.

[0090] The open loop 21 includes a foresight element 24. This foresight element 24 takes into account the curvature p of the traffic lane (calculated for example at (from the images obtained by the camera) in order to evaluate the ôFFD component of the steering angle ô. This open loop is generally known by the Anglo-Saxon term "feed forward".

[0091] Considering the bicycle model in steady state (with dX / dt = 0), and assuming the vehicle is at the center of its lane (dy / dt = 0 and y=0) and in a set turn (dô / dt=0), we can then write:

[0092] [Math.4] &FFD = P ( L + V sv v 2 )

[0093] In this equation, Vsv is the understeer gradient specific to the vehicle, which is classically defined by the following expression:

[0094] [Math.5] v _ Mf Mr Cr

[0095] In other words, the ôFFD component of the steering angle ô has a term pL which is determined according to the curvature of the turn and the architecture of the vehicle, and a term which allows to take into account the drift of the vehicle in turn.

[0096] The closed loop 25 includes an observer element 26 which allows observation of the state Xobs of the motor vehicle 10.

[0097] It also includes a comparator 28 allowing the difference between a reference state Xref and this observed state Xobs. This difference forms an error XeiT.

[0098] It finally includes a controller 20 which collects the signal delivered by the comparator 28 and generates the ôFBK component of the steering angle ô.

[0099] This controller 20 in practice includes a gain Ks in the form of a vector which, once multiplied by the error Xeir, allows the calculation of the component ôFBK.

[0100] The state observer 26 collects a measurement vector Ymes (including measured values, such as the steering angle) and delivers the observed state Xobs.

[0101] The state representation implemented by the state observer 26 is based on the bicycle model of the vehicle.

[0102] This state observer 26 is used to estimate the unmeasured values ​​of the model parameters. These unmeasured values ​​are, for example, dy / dt and dô / dt.

[0103] It should be noted here that, as an alternative, this observer could be dispensed with if all the values ​​were measured.

[0104] Denoting x as the estimate of the state vector X, the observer equation can be written as:

[0105] [Math.6] X = (A-LpC)X + Bs5fsk + LpY

[0106] with LP a gain value associated with the observer element 26.

[0107] Generally, the control implemented by the closed loop 25 aims to minimize the state vector X around a zero reference state Xref corresponding to a straight line. In other words, the nominal reference values ​​(under nominal driving conditions) are such that we can write:

[0108] [Math.7] %ref —

[0109] In summary, when the LCA function is activated and is operating in nominal mode (without driver action on the steering wheel 12), it is intended to measure the variables of the measurement vector Ymes and the curvature p of the traffic lane.

[0110] This curvature allows the calculation of the ôFFD component.

[0111] The measured variables allow, thanks to the state observer 26, to determine the values ​​Xobs>i of the parameters of the state vector X (also called state variables and noted: rp, drp / dt, y, dy / dt, ô, dô / dt, Jy.dt).

[0112] The vector XeiT, which is the difference between these observed values ​​Xobs>i and the corresponding nominal reference values ​​Xref>i, then allows us to determine the component ôFBK, and therefore to deduce the steering angle setpoint ô.

[0113] However, it may happen that the driver wishes to temporarily shift the vehicle to one side or the other of the traffic lane 31, while remaining in the latter, in order to get closer to the marking lines 33, 35 delimiting this lane.

[0114] This is typically the case when a motorcycle overtakes vehicles on Route 31 by passing between two lanes of traffic. Other situations may also lead the driver to move their vehicle to the right or left (to overtake a cyclist, to let a very wide vehicle pass in the opposite direction, etc.).

[0115] In these situations, the driver 40 takes action to modify the vehicle's trajectory. This action consists of applying a moderate torque to the steering wheel 12 in the desired direction. It should be noted that this torque is below a threshold beyond which it is considered that the driver 40 wishes to take back control of the vehicle 10 (so that the computer deactivates the LCA function).

[0116] When applying this moderate torque, the driver therefore shifts the vehicle to the- tomobile 10 of the median line T0.

[0117] The invention then proposes a solution allowing the vehicle, when the driver ceases his action on the steering wheel, to continue to follow a trajectory offset from the median line T0.

[0118] For this reason, in this situation, the reference values ​​are modified so that we can write:

[0119] [Math. 8] ^ref / dt w, dy Jdt - ref 1 do re f[dt ^ref -V At ' J '' ref ( 0 0 ref 0 0 , with vf * 0 re f

[0120] The idea then consists of adjusting the reference value of the lateral deviation yref to a non-zero value but which guarantees the safety of the vehicle and the comfort of the driver.

[0121] The vehicle will therefore be piloted in such a way as to maintain a non-zero lateral deviation from the median line T0 for several seconds at least.

[0122] In practice, the vehicle will only be driven in this way if the driver has sufficiently deviated from the centerline T0 for several seconds. Indeed, a slight deviation should not be interpreted here as an intention on the part of the driver to shift the vehicle away from the centerline T0 for a prolonged period.

[0123] The lateral deviation y between the vehicle and the median line T0 is therefore determined at the moment when the driver ceases to exert a torque on the steering wheel 12, and is then compared to a threshold.

[0124] To understand how this threshold is constructed, the traffic lane 31 used by the motor vehicle 10 has been represented on [Fig.4].

[0125] This traffic lane 31 is divided into three lanes, including: - a central band 31C on which the motor vehicle 10 travels at nominal speed (with yref = 0), - a left-side band 31 G, and - a right-side band 31D.

[0126] The terms right and left are defined here taking into account the direction of travel of the motor vehicle 10.

[0127] The central band 31C is centered on the traffic lane and has the same width on both sides of the centerline T0. Thus, the width Le of the band The central area will allow us to characterize the widths of the other bands.

[0128] In practice, the three bands 31C, 31D, 31G will not extend over the full width L of the traffic lane 31, but rather over a smaller "usable width L31'" in order to take into account the width of the vehicle and a safety margin.

[0129] This usable width can be calculated using the following equation:

[0130] [Math.9] — E31-E1Q- 2jWs

[0131] In this equation, the variable L31 corresponds to the effective width of the traffic lane 31 at the level of the motor vehicle 10, the variable Li0 corresponds to the width of the motor vehicle 10, and the term Ms corresponds to the safety margin that we wish to preserve on both sides of the motor vehicle 10.

[0132] This safety margin Ms could be a predefined constant. However, preferably, it will be a variable that is at least a function of the longitudinal speed v of the motor vehicle 10, and possibly also of its lateral acceleration (along the Y axis).

[0133] It should be noted that this safety margin can be modified by the driver 40, for example by using a menu that can be displayed on the touch screen 15.

[0134] The width Le of the central band 31C will then be defined as a predefined percentage of this usable width L3i'.

[0135] Therefore, when the driver exerts an action on the steering wheel 12 such that the vehicle moves away from the centerline T0 while remaining in this center band 31C and then ceases this action, the computer will be programmed to bring the motor vehicle 10 back along the centerline T0.

[0136] On the other hand, when the driver exerts an action on the steering wheel 12 such that the vehicle moves away from the median line T0 by going into one of the lateral bands 31G, 31D for a significant period of time and then ceases this action, the computer will be programmed to bring the motor vehicle 10 back along an offset line TD, TG, laterally away from the median line T0 (along the Y axis).

[0137] The offset line TG, TD will be located in the lateral band 31G, 31D in which the motor vehicle 10 has been diverted by the driver 40. It may be located in the centre of this band, or further towards the median line T0.

[0138] Preferably, this offset line TG, TD will always have the same position in the traffic lane. Typically, the two offset lines may be located at one-quarter and three-quarters of the usable width L' of the traffic lane 31. Thus, the driver can become accustomed to this position, which will give him a feeling of confidence in the function.

[0139] We can now describe the process as it can be implemented by the vehicle's computer 11 when the LCA function is activated.

[0140] This process is implemented in loops, with a constant sampling step on the order of a tenth of a second for example.

[0141] As explained above, this process consists, when the driver 40 exerts an action on the steering wheel 12 to shift the vehicle from the median line T0 (while remaining in the traffic lane) and then ceases this action, of steering the vehicle so that it follows an offset line TD, TG if two conditions are met, or otherwise of bringing the vehicle back towards the median line T0.

[0142] The first condition is that the vehicle is sufficiently offset from the centerline at the end of the action performed by the driver 40 (if the offset by the driver was small, the vehicle returns directly to the center of the lane). The second condition is that the driver has offset the vehicle from the centerline for a significant duration (typically several seconds). Thus, if this offset was momentary, the vehicle returns directly to the center of the lane.

[0143] The various detailed steps for implementing this process are as follows.

[0144] During a preliminary step, the camera acquires an image of the environment at the front of the motor vehicle 10.

[0145] Based on this image, the computer (or a computer embedded in the camera) determines, by image recognition, the equations of the two marking lines 33, 35 which delimit the traffic lane 31. In the absence of such marking lines, the camera could be adapted to determine the positions of the edges of the traffic lane (barrier, edge of the roadway...).

[0146] The calculator can then simply deduce the equation of the median line T0.

[0147] In parallel, the computer acquires data enabling it to determine if the The driver exerts an action aimed at shifting the vehicle from the median line T0. In this case, he acquires the torque exerted by the driver 40 on the steering wheel 12.

[0148] More generally, the computer will determine whether an action is taken or not by the driver, via a torque sensor, a steering wheel pressure sensor or any other usable sensor.

[0149] As long as no action is taken (zero torque at the steering wheel), the computer controls the power steering actuator so that the vehicle follows this centerline T0. As specified above, it uses the nominal reference values ​​of equation Math.7 for this purpose.

[0150] On the other hand, as soon as an action is undertaken, the computer activates a sub-function of the LCA function, called the TMD function (from the English "Trajectory Modulation by Driver", i.e., trajectory modulation by the driver).

[0151] Figure 5 shows in more detail the steps involved in implementing this TMD function.

[0152] The first step E0 consists of checking whether the TMD function is activated.

[0153] When this is the case, i.e. when an action is undertaken by the driver 40, the computer implements a first Opl operation which aims to determine how long the motor vehicle 10 spends in the 31D, 31C, 31G lane of the traffic lane (the one used at the time the action undertaken ends).

[0154] In other words, this operation aims to quantify, when the driver 40 exerts a torque on the steering wheel, the time during which the motor vehicle 10 remains in one of the three bands 31D, 31C, 31G.

[0155] In practice, this operation includes a first step E10 which consists of resetting a TC counter to zero and then triggering it. This TC counter will remain activated as long as the action undertaken has not ended and the motor vehicle 10 remains in the same lane 31D, 31C, 31G of the traffic lane 31 without changing lanes.

[0156] For this, during a second step E12, the computer determines whether the action undertaken is still in progress (non-zero torque at the flywheel).

[0157] If so, during a third step E14, the computer determines whether the motor vehicle 10 is changing bands 31D, 31C, or 31G. If so, the process returns to step E10 to reset the counter. If not, the process continues in step E16, incrementing the TC counter, and then the process starts again, at the next time step, in step E12.

[0158] It should be noted that when, during step E12, the computer detects that the action undertaken has ended (zero torque at the flywheel), a second operation Op2 is initiated.

[0159] This second operation Op2 consists of determining whether the vehicle should be piloted along the median line T0 or along one of the offset lines TD, TG. It is implemented in several steps.

[0160] During a first step E20, the computer determines which lane the vehicle is on (at the time the action taken has ended).

[0161] If it is located on the center band 31C, the nominal control mode along the centerline T0 can be resumed. In this event, a fourth operation Op4 described below can then be implemented.

[0162] Conversely, if it is located on one of the side bands 31G, 31D, the computer checks, during a second step E22, whether the TC counter exceeds a predetermined time threshold STC. This threshold is greater than one second. For example, it is 3 seconds.

[0163] If this is the case, the automatic shift is validated (step E26) and the process continues during a third operation Op3 described below.

[0164] Otherwise, the automatic shift is not validated (step E24), notably because the vehicle has not remained off-center for a sufficient amount of time, which is interpreted as an intention on the part of the driver to remain on the same trajectory as before the action was initiated. The process then proceeds to step E28 which consists of determining whether, before undertaking this action, the vehicle was offset from the median line TO or not.

[0165] If, before the action was undertaken, the vehicle was following the median line TO, the fourth operation Op4 described below can then be directly implemented so as to gradually bring the motor vehicle back onto this median line TO.

[0166] Otherwise, the process continues with the third operation Op3 to bring the vehicle back to the offset line TD, TG that it was following before the action was taken.

[0167] The third operation aims to enable the vehicle to follow the offset line TD, TG for a specified duration.

[0168] During this third operation, the computer 11 applies a non-zero lateral deviation reference value yref, according to the formula Math.8, so as to keep the motor vehicle 10 along the chosen offset line TD, TG.

[0169] In parallel, during a first step E30, the control unit 11 resets another TCI counter and increments it at each new time step. During a second step E32, it checks whether this TCI counter exceeds a predetermined time threshold. As long as it does not, the lateral offset is maintained. However, when the TCI counter reaches this time threshold, the vehicle offset is designed to gradually cancel itself out automatically.

[0170] Alternatively, the lateral offset could be maintained unless the driver requests it (for example, by counter-steering the steering wheel 12). However, in this case, it is considered safer to bring the vehicle back to the center of its lane within a few seconds.

[0171] The time threshold could be predetermined (for example, equal to 10 seconds). Alternatively, it could be chosen based on various parameters (type of road, vehicle speed, presence of motorcycles nearby, presence of obstacles, etc.).

[0172] It should be noted here that the basic delay of 10 seconds can be modified by the driver 40 in a menu that can be displayed on the touch screen 15.

[0173] The fourth operation Op4 consists, when the 10-second delay is exceeded (or when after the second operation Op2, the computer considers that the vehicle must return to the median line T0), of progressively reducing the lateral gap y between the center of gravity CG of the motor vehicle 10 and the median line T0.

[0174] For this, we could directly apply a reference value of the lateral deviation yref of zero, according to the formula Math.7.

[0175] However, here, to make the vehicle's trajectory smoother, it is chosen to progressively reduce the reference value yref used in the Math.8 formula. This value is reduced here according to an affine slope function that is either predetermined, adjustable by the driver via a menu displayed on the touchscreen 15, or by depending on the driving mode used (sport, normal, eco...

[0176] Thus, at each time step, the computer 11 reduces the reference value yref during step E40 and then determines during step E42 whether this value has reached zero. As long as this is not the case, these two steps are repeated.

[0177] When this is the case, the process is complete.

[0178] Of course, if during operations Op3 or Op4 the driver undertook a new action, the process would stop and resume at step E0.

[0179] We can now describe several examples of implementation of the process described above.

[0180] Figures 6 and 7 relate to two distinct examples.

[0181] In these two figures, the top graph represents, viewed from above, the circular track culation 31 with the curves: - C1 and C2 which represent the edges of the traffic lane, - C3 and C4 which represent the edges of the central strip 31C, - T0 which represents the median line, - TD and TG, which represent the offset lines, and - C5 which represents the trajectory of the motor vehicle 10.

[0182] The graph below represents the TCI timing value.

[0183] The middle graph represents, by curve C6, the value of a Boolean variable which is equal to 0 when no action is taken by the driver and the value 1 otherwise. Curve C8 represents another Boolean variable which is equal to 1 when the TCI time delay is non-zero and equal to 0 otherwise.

[0184] On [Fig.6], the following situations can be observed.

[0185] When time t is equal to 95s, the driver has performed an action which has not caused the vehicle to leave the central band 31C, so that when the action taken by the driver ends, the vehicle is immediately brought back by the computer 11 to the midline T0.

[0186] When time t equals 15s, the driver exerted an action that caused the vehicle to move out of the central lane 31C to the left for a period of more than 3 seconds, such that when the action taken by the driver ends, the vehicle is brought back by the control unit 11 towards the offset line TG. The vehicle remains centered on this line for 10 seconds and is then brought back by the control unit 11 towards the median line T0 (with an affine progression).

[0187] It will be noted here that, as an alternative, there could be no 10-second delay, so that the vehicle would remain on the offset line TG until the driver undertakes a new action to bring the vehicle back into the central lane 31C.

[0188] When time t is equal to 65s, the driver exerted an action which caused the vehicle from the center line 31C to the right for a period of less than 3 seconds, so that when the action taken by the driver ends, the vehicle is brought back by the computer 11 towards the center line TO.

[0189] When time t equals 110 s, the driver has performed an action that has moved the vehicle out of the center lane 31C to the right for a period of more than 3 seconds, so that when the driver's action ends, the vehicle is brought back by the control unit 11 to the offset lane TD. The TCI counter then increments, but before it reaches 10 seconds, a new action is performed by the driver 40. At that point, the TCI counter is reset to zero. Since this new action is not intended to move the vehicle to a different lane 31D, when it ends, the vehicle is immediately brought back by the control unit 11 to the offset lane TD.

[0190] On [Fig.7], we can observe the following situation.

[0191] When time t equals 15 s, the driver exerted an action that caused the vehicle to move out of the central lane 31C to the left for a period of more than 3 seconds, such that when the driver's action ends, the vehicle is brought back by the control unit 11 to the offset line TG. The vehicle remains centered on this line for 10 seconds and is then brought back by the control unit 11 to the median line T0 (with an affine progression).

[0192] During this return, it is observed that at time t equal to 35s, the driver again exerts an action to bring the vehicle back towards the offset line TG from which it had begun to deviate. Therefore, when the action taken by the driver ends, the vehicle is brought back by the control unit 11 towards this offset line TG. The vehicle remains centered on this line for 10 seconds and is then brought back by the control unit 11 towards the median line T0 (with an affine progression).

[0193] During this return, it is observed that at time t equal to 48s, the driver again exerts an action, this time to bring the vehicle back towards the median line T0 faster than the computer 11 does. Therefore, when the action undertaken by the driver ends, the vehicle being on the central band 31C, the vehicle is brought back by the computer 11 towards this median line T0.

[0194] The present invention is in no way limited to the embodiment described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

Claims

Demands

1. A method for controlling a motor vehicle (10) traveling on a lane (31) of a road (30), comprising the steps of: - acquiring data relating to edge lines (33, 35) of said lane (31), - determining a centerline (T0) of said lane (31) taking into account said data, - acquiring a lateral deviation (y) between the motor vehicle (10) and the centerline (T0), - calculating, by a computer (11) on board said motor vehicle (10), a steering command for the motor vehicle (10) as a function of said centerline (T0), and - controlling, by the computer (11), a steering actuator of said motor vehicle (10), according to said steering command, wherein, when two conditions are met,namely: - that a driver (40) of the motor vehicle (10) exerts an action on an interface (12) of the motor vehicle (10) to command a shift of the motor vehicle (10) with respect to said median line (T0) and then ceases this action, and - that, at the moment when he ceases said action, the lateral deviation (y) is greater than a deviation threshold, said driving instruction is determined so that the motor vehicle (10) follows a lateral line (TD, TG) laterally offset from the median line (T0), characterized in that:, - a step is planned for acquiring values ​​(Xobs>i) of parameters (ip, drp / dt, y, dy / dt, ô, dô / dt, Jy.dt) relating to the dynamics of the motor vehicle (10) and its position in said traffic lane (31), one of said parameters being the lateral deviation (y), - the steering command is calculated by means of a controller (20), as a function of the acquired values ​​(Xobs>i) and reference values ​​(Xref>i) of said parameters (rp, drp / dt, y, dy / dt, ô, dô / dt, Jy.dt), the reference value of the lateral deviation (y) being chosen: H is zero when both conditions are not met, for the motor vehicle (10) to follow the median line (T0), or H is non-zero when both conditions are met for the motor vehicle (10) to follow the lateral line (TG, TD), and as a function of the configuration of the traffic lane so that the side line (TG, TD) always has the same position in the traffic lane.

2. A piloting method according to claim 1, wherein said piloting instruction is determined so that the motor vehicle follows the lateral line (TD, TG) only if said lateral deviation (y) has remained, while the driver was performing said action, above said deviation threshold for a duration greater than a time threshold.

3. A piloting method according to claim 2, wherein said deviation threshold is determined as a function of an effective width (L3i) of the traffic lane (31).

4. A piloting method according to claim 3, wherein said deviation threshold is determined as a function of a usable width of the traffic lane, said usable width being calculated as a function of the effective width (L3[), a width (Li0) of the motor vehicle (10), and a safety margin.

5. A piloting method according to claim 4, wherein said safety margin varies as a function of the speed and / or acceleration of the motor vehicle (10).

6. A piloting method according to any one of claims 1 to 5, wherein, when both conditions are met, said piloting instruction is determined so that the motor vehicle (10) follows the lateral line (TG, TD) for a determined time, and then said piloting instruction is determined so that the motor vehicle (10) returns to the median line (T0).

7. A piloting method according to claim 6, wherein said determined time has a reference value of several seconds.

8. A control method according to claim 6 or 7, wherein said determined time has a value that can be modified by the driver by means of an interface embedded in the motor vehicle (10).

9. A piloting method according to any one of claims 1 to 8, wherein, when both conditions are not met, said piloting instruction is determined so that the motor vehicle (10) follows the centerline (T0).

10. A motor vehicle (10) comprising: - acquisition means adapted to acquire, when the motor vehicle (10) is moving on a traffic lane (31), data relating to edge lines (33, 35) of said traffic lane (31), and - a steering actuator adapted to control the motor vehicle (10), characterized in that it further comprises a computer (11) programmed to implement a control method according to one of claims 1 to 9.

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