Method for adjusting the lateral position of a vehicle - Patents.com

Abstract

1. A method for adjusting the lateral position of a vehicle (1) on a traffic lane (10), comprising: a step (E21) of calculating a reference state vector (Xref) of the vehicle; a step (E22) of calculating an observed state vector (Xobs) of the vehicle; a step (E23) of calculating a setpoint value for the steering angle (δc) of a steering wheel (2f) of the vehicle as a function of the difference (Xerr) between the reference state vector (Xref) and the observed state vector (Xobs); and an initialization step (E1) performed when the adjustment method is started, the initialization step comprising a substep (E11) of calculating a component (X07) of the initial observed state vector (X0) so that the setpoint value for the steering angle (δc) of the steering wheel is equal to the measured steering angle (δm) value of the steering wheel.

Description

[Technical field]

[0001] The present invention relates to a method for adjusting the lateral position of a vehicle, in particular an autonomous vehicle, on a traffic lane. The invention particularly relates to an initialization step performed at the start of the adjustment method. The invention also relates to a motor vehicle including hardware and / or software means for implementing such a method. [Background technology]

[0002] An autonomous vehicle typically includes a steering system controlled by a computer. The steering system controls the orientation of the vehicle's steered wheels so that the vehicle follows a given trajectory autonomously. The computer implements an adjustment process that allows the vehicle to be positioned laterally on a traffic lane. In particular, the computer may implement an adjustment process known as LCA (Lane Centering Assist), which allows the vehicle to remain centered in the vehicle's traffic lane.

[0003] When such a process is initiated during driving, the vehicle moves from a trajectory manually defined by the driver to an autonomously determined reference trajectory. This change in trajectory can, in certain specific cases, generate significant lateral accelerations of the vehicle. These lateral accelerations can cause anxiety to the rider and even instability or loss of grip of the vehicle.

[0004] In particular, it is noted that the lateral accelerations to which the vehicle is subjected at the time of the transition from manual control of the track to autonomous control of the track are particularly high in certain circumstances. In particular, these lateral accelerations are particularly high when the vehicle sensors, in particular the angle sensors at the steering wheels of the vehicle, are not calibrated or contain calibration deviations (i.e., differences between the values ​​measured by the sensors and the true values). These lateral accelerations are also particularly high when the vehicle is moving on a banked or cambered traffic lane, i.e., a traffic lane that is laterally inclined, at the time of this transition.

[0005] Presentation of the invention The object of the present invention is to provide a method for adjusting the position of a vehicle on a traffic lane, which obviates the above mentioned drawbacks and improves the adjustment methods known from the prior art.

[0006] More specifically, a first object of the present invention is a method for regulating the lateral position of a vehicle on a traffic lane that avoids excessive lateral acceleration of the vehicle during start-up.

[0007] A second object of the invention is a method for adjusting the position of a vehicle on a traffic lane, which allows limiting the maximum steering angle of the steered wheels of the vehicle. Summary of the Invention

[0008] The present invention relates to a method for adjusting a lateral position of a vehicle on a traffic lane, the method comprising: - calculating a reference state vector of the vehicle; - calculating an observed state vector of the vehicle; - calculating a steering angle setpoint for the steered wheels of the vehicle as a function of the difference between a reference state vector and an observed state vector; Including, The adjustment method includes an initialization step that is performed at the start of the adjustment method, the initialization step including a sub-step of calculating components of an initial observed state vector such that the steering angle set value of the steered wheels at the start of the adjustment method is equal to the measured steering angle value of the steered wheels at the start of the adjustment method.

[0009] The observed state vector is given by the following components: - the yaw rate of the vehicle, and / or - the vehicle's heading angle, and / or - the lateral speed of the vehicle, and / or - the lateral distance of the vehicle with respect to the reference track, and / or - the steering speed of the steered wheels of the vehicle, and / or - the steering angle of the steered wheels of the vehicle, and / or - integral of the lateral distance of the vehicle with respect to the reference track may include all or part of.

[0010] During the sub-step of calculating the components of the initial observed state vector, said components may be calculated as a function of the steering angle value measured at the time of initiation of the adjustment method.

[0011] The observed state vector may contain a component equal to the integral of the vehicle's lateral distance with respect to the reference trajectory, and an initial value of the integral of the lateral distance defined during the initialization step is calculated so that the steering angle setting value of the steered wheels at the time of starting the adjustment method is equal to the measured steering angle value of the steered wheels at the time of starting the adjustment method.

[0012] The step of calculating the steering angle set point may include multiplying the difference between the reference state vector and the observed state vector by an adjustment vector, the adjustment vector being dependent on the speed of the vehicle.

[0013] An initial value of the integral of the vehicle's lateral distance with respect to the reference trajectory can be calculated as a function of the components of the difference between the reference state vector and the observed state vector, as a function of the components of the adjustment vector, and as a function of the measured steering angle value at the start of the adjustment method.

[0014] The calculation of the observed state vector may be based on quantities measured by the vehicle's on-board sensors, constants characterizing the vehicle, the vehicle's speed, and the values ​​of the steering angle setpoints of the vehicle's steered wheels calculated during a previous iteration of the adjustment method.

[0015] The invention further relates to a computer program product comprising program code instructions stored on a computer readable support for implementing the steps of the adjustment method as defined above, when said program is run on a computer.

[0016] The invention further relates to a computer-readable data storage medium on which a computer program is stored, comprising program code instructions for implementing the adjustment method as defined above.

[0017] The invention further relates to a motor vehicle including hardware and / or software means for implementing a regulation method as defined above.

[0018] Figure presentation These objects, features and advantages of the present invention will be explained in detail in the following description of particular embodiments, given purely in a non-limiting manner in combination with the attached figures. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of a motor vehicle according to an embodiment of the present invention, viewed from above. [Diagram 2] FIG. 1 is a schematic view from above of a vehicle on a traffic lane. [Diagram 3]FIG. 1 is a schematic front view of a vehicle on a traffic lane. [Figure 4] FIG. 1 is a schematic overview of a regulation method according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic diagram of a regulator used in the regulation method. [Figure 6] 4 is a graph illustrating the performance of an adjustment method according to an embodiment of the present invention in comparison with an adjustment method according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 illustrates a schematic diagram of a motor vehicle 1 according to an embodiment of the present invention. The vehicle 1 may be of any type. In particular, the vehicle 1 may be, for example, a car, a utility vehicle, a truck, or a bus. The vehicle 1 has two steered front wheels 2f and two rear wheels 2r. The orientation of the steered wheels 2f may be controlled by a steering system 3. The steering system 3 includes a steering device 4 mechanically connected to the two front wheels 2f and a steering wheel 5 mechanically connected to the steering device 4. The steering system may further include a power-assisted steering module, for example integrated in the steering device 4. The steering system 3 further includes an electronic control unit 6 and a steering wheel angle sensor 7. The steering wheel angle sensor 7 is capable of measuring the orientation of the steering wheel 7. In particular, the steering wheel angle sensor 7 may measure the angular position of a steering column connected to the steering wheel 7. The orientation of the steering wheels 7 is proportional to the orientation of the steered wheels 2f, i.e. the steering angle of the steered wheels 2f. Controlling the steering angle of the steered wheels is therefore equivalent to controlling the angle at the steering wheels of the vehicle 1. Furthermore, the vehicle 1 may be equipped with other sensors, such as a yaw sensor and / or at least one wheel speed sensor, allowing the determination of the vehicle speed.

[0021] The electronic control unit 6 is electrically connected to the steering wheel angle sensor 7, to the steering device 4 and in some cases to other sensors of the vehicle. In particular, the electronic control unit 6 includes a memory, a microprocessor and an input / output interface for receiving data provided by other equipment of the vehicle 1 or for transmitting data for the attention of other equipment of the vehicle 1. The memory of the electronic control unit is a data storage medium in which a computer program is stored, which includes program code instructions for implementing a method according to an embodiment of the present invention. The microprocessor is capable of executing the method. In particular, the electronic control unit 6 is capable of sending a control command via the input / output interface of the electronic control unit 6 to the steering device 4 to steer, i.e. orient, the steered wheels by the calculated angle. The longitudinal axis X1 of the vehicle may be defined as the axis parallel to the direction in which the vehicle is traveling in a straight line.

[0022] The vehicle 1 further comprises means 8 for detecting the surroundings of the vehicle 1, for example a radar, a lidar or a camera. The detection means 8 are further connected to the electronic control unit 6. The vehicle 1 is an autonomous vehicle, i.e. the steering system can control the orientation of the steered wheels 2f without the driver operating the steering wheels 5. The vehicle 1 can therefore travel along a steering path and remain on said steering path without the intervention of the driver. The vehicle 1 can also be conventionally controlled by the driver moving the steering wheels. The vehicle 1 can therefore be used in two distinct functional modes: in a first mode, called manual mode, the orientation of the steered wheels is controlled by the driver. In a second mode, called autonomous mode, the orientation of the steered wheels is controlled by the electronic control unit, in particular by means of detection means 8 connected to said electronic control unit.

[0023] FIG. 2 illustrates a vehicle 1 traveling on a traffic lane 10. The traffic lane 10 is delimited to the left and right by two boundary lines 11 marked on the traffic lane in the form of solid or dashed lines, for example white or yellow in color. The detection means 8 are capable of identifying the boundary lines 11. The electronic control unit includes software means enabling the calculation of a reference trajectory 12 or a setpoint trajectory. The reference trajectory 12 is identified by a dotted line in FIG. 2. The reference trajectory 12 is a theoretical line that is not visible on the traffic lane 10. The reference trajectory 12 can be, for example, a line that is placed equidistant from the two boundary lines 11. As a variant, the reference trajectory 12 can be defined differently. It can be shifted more towards one or the other of the two boundary lines 11. It can even be calculated as a function of the detection of an obstacle or another vehicle present on the traffic lane or on a traffic lane adjacent to the traffic lane 10.

[0024] In this document, the longitudinal axis X is defined as the axis of the traffic lane parallel to the reference trajectory at the height of the vehicle 1. The lateral axis Y is the axis of the traffic lane perpendicular to the reference trajectory at the height of the vehicle 1. The axis Z is the axis perpendicular to the plane formed by the traffic lane. The axes X, Y and Z form an orthogonal reference system.

[0025] The traffic lane illustrated in FIG. 2 is a straight line. However, the invention can also be used when the traffic lane exhibits a curve or a bend. As FIG. 3 illustrates, the traffic lane 10 can be banked. The axis Z normal to the surface of the traffic lane 10 is therefore inclined by an angle A1 not equal to zero with respect to the vertical axis Z'. The angle A1 is oriented laterally. This means that the traffic lane slopes along the lateral axis Y. When a vehicle is traveling on such a traffic lane, the steered wheels must be steered slightly, generally towards the top of the slope, in order for the vehicle to maintain a straight trajectory. Spin may then occur at the interface between the steered wheels 2f and the road surface. In such a situation, the steered wheels are not perfectly aligned with the direction followed by the vehicle. The steering wheel angle measured by the steering wheel angle sensor therefore provides a value for the steering wheel angle that is offset with respect to the value that would be applied if the vehicle were to follow the same heading direction on a flat road surface. The described invention can advantageously be used on such banked traffic lanes, leading to smoother adjustment of the vehicle's position, in comparison with methods for adjusting the vehicle's position known from the prior art.

[0026] The invention may furthermore advantageously be used on traffic lanes with a camber in the lateral direction. On such roads, the part of the road surface in contact with the front left wheel is not parallel to the part of the road surface in contact with the front right wheel. In countries where traffic drives on the right, cambered traffic lanes may be constructed such that vehicles traveling on the road drift slightly towards the right hand side of the road. If the driver is inattentive, this will prevent him from colliding with a vehicle coming in the opposite direction and therefore traveling to his left. More generally, the invention will advantageously be used in all situations in which the steering angle of the steered wheels obtained by the steering wheel angle sensor does not correspond to the direction actually followed by the vehicle.

[0027] The state of a vehicle, i.e., its position on the traffic lane 10 and its trajectory, may be characterized by a set of physical quantities or state variables, some of which are illustrated in FIG. 2. In particular, a vehicle state may be characterized by: the yaw velocity dψ of the vehicle, and / or the heading angle ψ of the vehicle, and / or - the lateral speed dy of the vehicle, and / or - the lateral distance y of the vehicle with respect to the reference trajectory, and / or the steering speed dδ of the steered wheels of the vehicle, and / or the steering angle δ of the steered wheels of the vehicle, and / or - integral of the lateral distance of the vehicle with respect to the reference trajectory It can be characterized by:

[0028] The yaw velocity dψ is the rotational velocity of the vehicle around the axis Z. The yaw velocity can be measured, for example, by means of a yaw sensor. The heading angle ψ can be defined as the angle formed between the longitudinal axis X of the traffic lane 10, i.e. the axis tangent to the reference trajectory 12 at the height of the vehicle, and the longitudinal axis X1 of the vehicle. The lateral distance y can be defined as the distance separating a point of the vehicle (in particular its centre of gravity C) from the reference trajectory 12. As a variant, the lateral distance y may also be measured as the distance separating a point of the vehicle from the boundary line 11. The heading angle ψ and the lateral distance y can be calculated, for example, by the detection means 8 of the vehicle. The lateral velocity dy is the derivative of the lateral distance y with respect to time. The integral of the lateral distance ly can be calculated with respect to time and from an initial point in time corresponding to the point of initiation of the adjustment method.

[0029] The steering angle δ of the steered wheel may be defined as the angle formed between an axis X2 parallel to the direction of travel of the steered wheel and the longitudinal axis X1 of the vehicle. The steering angle δ is proportional to the steering wheel angle measured by the steering wheel angle sensor 7. It is noted that when the vehicle turns, the two steered wheels of the vehicle are generally steered at slightly different angles to take into account the different radii of the curves traced by each of the steered wheels. Advantageously, the state of the vehicle can be simplified using a so-called "bicycle" model, i.e., by considering a single steered wheel, the steering angle of which causes the vehicle to trace the same curve as with two steered wheels with different steering angles. The steering angle of the steered wheel using the "bicycle" model may be, for example, the average angle between the steering angle of the left steered wheel and the steering angle of the right steered wheel. The steering speed dδ of the steered wheels is the derivative of the steering angle δ with respect to time.

[0030] Using the state variables just described, a state vector X can be defined as follows: [Formula 1] TIFF0007634489000001.tif43170

[0031] The state vector X therefore comprises seven components. The state vector X allows the characterization of the position and trajectory of the vehicle 1 at a given instant. As a variant, the components of the state vector may be presented in a different order or may even comprise different variables instead of or in addition to the proposed ones. The following description will therefore be adapted accordingly. In general, the state vector may characterize the position, the speed and the acceleration of the vehicle at a given instant. The state vector is therefore a time-variable vector.

[0032] With reference to FIG. 4, the application will now describe a method for adjusting the lateral position of a vehicle 1 on a traffic lane 10. The method can be subdivided into two main steps E1 and E2. The first step E1 is an initialization step performed at the start of the adjustment method. In particular, the first step E1 can be performed during the transition of the vehicle 1 from a manual driving mode to an autonomous driving mode. The second step E2 is a step of adjusting the position of the vehicle 1, performed subsequently after the initialization step E1. The second step serves to calculate a steering angle setpoint δc for the steered wheels of the vehicle. The second step can therefore be repeated at a given frequency insofar as the vehicle 1 is autonomously controlled.

[0033] For a clear understanding of the invention, the present application will first describe the second step E2 and then the first step E1. The second step E2 is illustrated diagrammatically in Figure 5, which illustrates a closed-loop control system.

[0034] The second step E2 comprises a step E21 of calculating a reference state vector Xref of the vehicle, a step E22 of calculating an observed state vector Xobs of the vehicle, and a step E23 of calculating a steering angle setpoint δc of the steered wheels of the vehicle as a function of the difference Xerr between the reference state vector Xref and the observed state vector Xobs. The steering angle setpoint δc is then used to calculate the observed state vector Xobs during subsequent iterations of the second step E2.

[0035] During a calculation step E21, a reference state vector Xref is calculated, which indicates the position and the desired trajectory for the vehicle. This state vector may in particular be calculated as a function of the reference trajectory 12. Since the vehicle 1 undergoes various disturbances, for example resulting from factors external to or internal to the vehicle 1, the reference state vector Xref at a given instant may differ from the observed state vector Xobs of the vehicle.

[0036] During a calculation step E22, the observed state vector Xobs is calculated from the sensors on board the vehicle, a dynamic model of the vehicle (identified by 21 in FIG. 5) and the observer (identified by 22 in FIG. 5). The dynamic model 21 can be shown by the following equation: [Formula 2] dX=A.X+B1.δc+B2.ρ

[0037] In this formula, - dX is the derivative with respect to time of the state vector X. δc is the steering angle setpoint of the steered wheels calculated during the preceding iteration of the second step E2, - ρ is the curvature of the traffic lane. This value is zero when the traffic lane is straight. To simplify the rest of the description, it is considered that the traffic lane is in fact a straight line. The adjustment method according to the invention can, however, be transferred to the situation where the vehicle is driving around a curve. - A is a 7x7 matrix that will be defined as follows: B1 and B2 are vectors with seven components defined below.

[0038] The matrix A may be defined by the following formula: [Formula 3] TIFF0007634489000002.tif57170

[0039] In that formula, - cf indicates the drift stiffness of the vehicle's front wheelbase (train); - cr indicates the stiffness of the rear wheelbase of the vehicle; - lf indicates the distance between the center of gravity C of the vehicle and the front wheels, - lr indicates the distance between the center of gravity C of the vehicle and the rear wheels; - lz indicates the inertia of the vehicle, - m denotes the mass of the vehicle, - v indicates the speed of the vehicle, - ζ indicates the damping factor of the steering system, - ω indicates the natural frequency of the filter of the steering system.

[0040] The parameters cf, cr, lf, lr, m, ζ, and ω are therefore constants that characterize the vehicle and can be defined once and for all during the development of the vehicle and stored in the memory of the electronic control unit.

[0041] Vector B1 may be defined by the following formula: [Formula 4] TIFF0007634489000003.tif43170

[0042] In that equation, ω denotes the natural frequency of the filter of the steering system.

[0043] Vector B2 may be defined by the following formula: [Formula 5] TIFF0007634489000004.tif41170

[0044] In that equation, v indicates the speed of the vehicle.

[0045] Furthermore, the measurement vector Y may be defined by the following formula: [Formula 6] Y=CX

[0046] In that formula, C denotes a diagonal matrix that allows the separation of the state variables that compose the vector X, which are directly available thanks to the on-board sensors of the vehicle 1. The matrix C is therefore a matrix that depends on the measurements available on the vehicle.

[0047] On the basis of the dynamics model 21 presented above, the observed state vector Xobs can be calculated by means of an observer 22. The observer 22 allows the estimation of the unmeasured components of the observed state vector. In the case where the road curvature is zero, the observed state vector can therefore be calculated by means of the following equation: [Formula 7] dXobs=(A-Lp.C).Xobs+B1.δ+Lp.Y

[0048] In that formula, - Xobs denotes the observed state vector, - dXobs denotes the derivative with respect to time of the observed state vector, - Lp is a positive linear matrix that depends on the vehicle speed, A, B1, C, and δ are quantities defined above.

[0049] During a third calculation step E23, first the difference between the reference state vector Xref and the observed state vector Xobs is calculated. This difference gives a vector Xerr representing the error between the theoretical state of the vehicle and the actual state of the vehicle. The vector Xerr can therefore be defined by the following formula: [Formula 8] Xerr=Xref-Xobs

[0050] The steered wheel steering angle setpoint is then deduced from the vector Xerr by multiplying Xerr by an adjustment vector Ks, where Ks is a vector dependent on the vehicle speed. Thus, the steered wheel steering angle setpoint δc can be calculated using the following formula: [Formula 9] δc=Ks.Xerr+δvir

[0051] In that equation, δvir indicates the steering angle of the steered wheels required to follow the curvature of a possible curve the vehicle is traveling in. Assuming that the method is performed on a straight traffic lane, the term δvir will therefore be zero.

[0052] It is noted that the second step E2 uses a vector Ks and a matrix Lp, both defined as a function of the vehicle speed. The memory of the electronic control unit can therefore contain different values ​​for the vector Ks and the matrix Lp defined for predefined speed values. When the vehicle is actually traveling at an intermediate speed between two predefined speed values, the vector Ks and the matrix Lp can be extrapolated by weighting the stored vector Ks and matrix Lp, respectively, for speeds higher and lower than the actual speed of the vehicle.

[0053] Now the first step E1 will be described, during which the regulation method is initialized.

[0054] The initialization step E1 includes a sub-step E11 of calculating the components of the initial observed state vector X0 such that the steering angle setpoint δc of the steered wheels at the time of initiation of the adjustment method is equal to the measured steering angle δm of the steered wheels at the time of initiation of the adjustment method. The initial observed state vector X0 corresponds to the observed state vector at the moment of the transition between the manual driving mode and the autonomous driving mode, i.e. at the time of initialization of the adjustment method. Therefore, certain initial conditions are imposed on the observed state vector so as to achieve a smooth transition between the manual driving mode and the autonomous driving mode. The measured steering angle δm of the steered wheels is obtained using a steering wheel angle sensor by multiplying the steering wheel angle by a proportionality factor that depends on the steering device. Even if the steering wheel angle sensor 7 returns a measured value different from the real steering wheel angle (for example due to a deviation with respect to the real value), the steering angle setpoint is equal to this measured value. This avoids sudden fluctuations in the steering angle of the steered wheels during initialization.

[0055] The initial observed state vector X0, hereinafter more simply called vector X0, corresponds to the observed state vector at the time of the initialization step E1. The vector X0 may be defined by the following formula: [Formula 10] TIFF0007634489000005.tif48170

[0056] In that formula, - X01, X02, X03, X04, X05, X06, X07 denote the first, second, third, fourth, fifth, sixth, and seventh components, respectively, of vector X0; dψ0 is the yaw velocity of the vehicle measured or calculated at the current moment, i.e. at the time of initialization of the adjustment method, ψ0 is the heading angle of the vehicle, measured or calculated at the time of the initialization step E1, dy0 is the lateral speed dy of the vehicle, measured or calculated at the time of the initialization step E1, y0 is the lateral distance of the vehicle with respect to the reference trajectory, measured or calculated at the time of the initialization step E1, dδ0 is the steering speed of the steered wheels of the vehicle, measured or calculated at the time of the initialization step E1, δ0 is the steering angle of the steered wheels of the vehicle, measured or calculated at the time of the initialization step E1, - X07 is the seventh component of vector X0. X07 is calculated using the formula below. [Formula 11] TIFF0007634489000006.tif21170

[0057] In that formula, Ks,i denotes the component i of the adjustment vector Ks, Xerr,i indicates the component i of the difference between the reference vector and the vector X0 at the time of the initialization step E1, δm is the steering angle of the steered wheels of the vehicle measured at the time of the initialization step E1 and obtained using the steering wheel angle sensor, - δvir indicates the steering angle of the steered wheels required to follow the curvature of a possible curve in which the vehicle is turning.

[0058] The seventh component X07 is therefore calculated as a function of the value of the steering angle δm measured at the start of the adjustment method, but also as a function of the adjustment vector Ks.

[0059] By imposing such an initial value on the seventh component of the vector X0, in the first iteration of the calculation step E2, we obtain a steering angle setpoint δc for the steered wheels, which is equal to the measured steering angle δm of the steered wheels of the vehicle at the start of the adjustment method. Essentially, the seventh component of the reference vector Xref is zero during the first iteration of the calculation step E2, and the solution of the equation defined above, equation 9, therefore leads to δc=δm.

[0060] As a result, the seventh component X07 of the vector X0, which represents the initial value of the integral of the lateral distance of the vehicle with respect to the reference trajectory, ly, is defined such that the value of the steering angle setpoint of the steered wheels at the time of the start of the adjustment method is equal to the measured steering angle of the steered wheels at the time of the start of the adjustment method. The initial value of the integral of the lateral distance of the vehicle with respect to the reference trajectory is therefore not defined at a constant value, in particular, it is not defined at a zero value. Instead, it is calculated as a function of the measured value of the steering angle of the steered wheels at the time of the start of the adjustment method. Then, during the subsequent iterations of the calculation step E2, the integral of the lateral distance ly (i.e. the seventh component of the observed state vector Xobs) can be gradually increased or decreased depending on whether the vehicle is drifting laterally to the left or to the right due to the departure from this calculated initial value.

[0061] 6 is a graph that allows a comparison of the trajectory T1 followed by a vehicle 1 implementing an adjustment method according to an embodiment of the present invention with the trajectory T2 followed by a vehicle 1 implementing an adjustment method according to the prior art. To achieve this comparison, a deviation of 15° is applied to the value of the steering wheel angle issued by the steering wheel angle sensor. There is therefore a difference of 15° between the real steering wheel angle and the measured steering wheel angle. This situation illustrates an extreme case, in particular when the vehicle 1 is driving on a banked or cambered traffic lane or in the case of a calibration error of the steering wheel angle sensor. It is noted that such a calibration error may occur, for example, when the vehicle has left a manufacturing or repair shop and a calibration algorithm for the steering wheel angle sensor has not yet been executed. It is considered that the vehicle switches between the manual driving mode and the autonomous driving mode while moving on a straight line and that the real trajectory of the vehicle already substantially corresponds to the reference trajectory 12.

[0062] The graph can be subdivided into three parts P1, P2, P3, the horizontal axis being common to all three parts. The horizontal axis represents time expressed in seconds. It is considered that the vehicle switches from manual driving mode to autonomous driving mode at horizontal axis 0. Trajectory T2 is interrupted after a time span of approximately 1.7 seconds after the initiation of the adjustment method, because the driver had to interrupt the adjustment method and resume manual control of the vehicle.

[0063] The upper part P1 of the graph illustrates the steering wheel angle (expressed in degrees) for trajectory T1 and for trajectory T2. It is noted that trajectory T1 causes fluctuations in the steering wheel angle of at most plus or minus 5 degrees. Trajectory T2, however, causes larger fluctuations in the steering wheel angle. These fluctuations are even more than 10° over a time span of approximately 1 second. In fact, since the vehicle has already followed the reference trajectory 12, the steering angle set value calculated by the vehicle according to the prior art will be substantially equal to 0°. As a result, the steering wheel angle will suddenly switch from a value equal to the deviation (15° in this case) to a value equal to 0°, which will have the effect of a sudden large steering input.

[0064] The middle part P2 of the graph illustrates the lateral distance (expressed in meters) of the vehicle 1 with respect to the reference trajectory 12, relative to the trajectory T1 and relative to the trajectory T2.

[0065] The lower part P3 of the graph illustrates the lateral acceleration (expressed in m / s2) of vehicle 1 relative to trajectory T1 and relative to trajectory T2. The lateral acceleration imparted to the vehicle following trajectory T1 remains below approximately 0.7 m / s2. The lateral acceleration imparted to the vehicle following trajectory T2 is approximately 1.5 m / s2.

[0066] When the vehicle follows trajectory T2, the riders have the impression of a sudden steering input, which can disorient them and ruin their comfort. When the vehicle follows trajectory T1, the variations in steering wheel angle and lateral acceleration are more moderate. The riders' comfort is improved. The driver does not feel the need to resume control of vehicle 1.

[0067] Thanks to the invention, a method for adjusting the lateral position is achieved that does not cause any sudden steering inputs during the initiation of the method, even when the vehicle 1 is driving on a banked or cambered traffic lane, or even if the steering wheel angle sensor provides values ​​that differ by a deviation with respect to the actual value of the steering wheel angle. The method provides a comfortable and reassuring transition between manual and autonomous driving modes in all environments.

Claims

1. A method for adjusting a lateral position of a vehicle (1) on a traffic lane (10), said method comprising the steps of: A step (E21) of calculating a reference state vector (Xref) of the vehicle (1); a step (E22) of calculating an observed state vector (Xobs) of said vehicle (1); a step (E23) of calculating the steering angle setpoint (δc) of the steered wheels (2f) of the vehicle (1) as a function of the difference (Xerr) between the reference state vector (Xref) and the observed state vector (Xobs); Including, The adjustment method includes an initialization step (E1) that is executed at the start of the adjustment method, the initialization step (E1) including a substep (E11) of calculating a component (X07) of an initial observed state vector (X0) such that the steering angle set value (δc) of the steered wheels (2f) at the start of the adjustment method is equal to the measured steering angle value (δm) of the steered wheels (2f) at the start of the adjustment method, The observed state vector (Xobs) is made up of the following components: The yaw velocity (dψ) of the vehicle (1); The heading angle (ψ) of the vehicle (1); The lateral speed (dy) of the vehicle (1); the lateral distance (y) of the vehicle (1) with respect to a reference track (12); The steering speed (dδ) of the steered wheels (2f) of the vehicle (1); The steering angle (δ) of the steered wheels (2f) of the vehicle (1); the integral (ly) of the lateral distance of the vehicle (1) with respect to a reference trajectory (12); including all or part of 4. The method according to claim 3, wherein the observed state vector (Xobs) comprises a component equal to an integral (ly) of the lateral distance of the vehicle (1) with respect to a reference trajectory (12), and an initial value of the integral (ly) of the lateral distance defined during the initialization step (E1) is calculated such that the steering angle set value (δc) of the steered wheels (2f) at the time of initiation of the adjustment method is equal to the measured steering angle value (δm) of the steered wheels (2f) at the time of initiation of the adjustment method.

2. 2. The adjustment method according to claim 1, characterized in that during the substep (E11) of calculating a component (X07) of the initial observed state vector (X0), said component (X07) is calculated as a function of the measured steering angle value (δm) at the time of start of the adjustment method.

3. 3. The method according to claim 1 or 2, characterized in that the step (E23) of calculating the steering angle setpoint (δc) comprises multiplying the difference (Xerr) between the reference state vector (Xref) and the observed state vector (Xobs) by an adjustment vector (Ks), the adjustment vector (Ks) being dependent on the speed (v) of the vehicle (1).

4. 4. The adjustment method according to claim 3, characterized in that the initial value of the integral (ly) of the lateral distance of the vehicle (1) with respect to the reference trajectory (12) is calculated as a function of components of the difference (Xerr) between the reference state vector (Xref) and the observed state vector (Xobs), as a function of components of the adjustment vector (Ks), and as a function of the measured steering angle value (δm) at the time of starting the adjustment method.

5. 5. The adjustment method according to claim 3 or 4, characterized in that the calculation of the observed state vector (Xobs) is based on values ​​of quantities measured by on-board sensors (7) of the vehicle (1), constants characterizing the vehicle (cf, cr, lf, lr, lz, m, ζ, ω), the speed (v) of the vehicle (1) and a set value of the steering angle (δr) of the steered wheels (2f) of the vehicle (1) calculated during a previous iteration of the adjustment method.

6. A computer program product comprising program code instructions stored on a computer readable medium for implementing the steps of the adjustment method according to any one of claims 1 to 5, when said program is run on a computer.

7. A computer readable data storage medium having stored thereon a computer program comprising program code instructions for implementing the regulating method according to any one of claims 1 to 5.

8. A motor vehicle (1), characterized in that it comprises hardware and / or software means for implementing a regulating method according to any one of claims 1 to 5.

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