FR3141909A1 - Method for controlling a motor vehicle in the center of its lane - Google Patents

Abstract

The invention relates to a method of assisting the piloting of a motor vehicle to keep it in the center of its lane, comprising steps of: - acquisition of parameter values relating to the dynamics of the motor vehicle and its position in its lane of travel, a first of said parameters being an integral function of a position datum of the motor vehicle in its lane of travel, - determination of a steering angle setpoint of the motor vehicle by means of a controller, in function of the acquired values and nominal reference values of said parameters. According to the invention, when the implementation of the control method has been suspended and then resumes, the steering angle is acquired and the reference value of said first parameter is modified so as to minimize the difference between the acquired steering angle and the steering angle setpoint. Figure for abstract: Fig.2

Description

Method of controlling a motor vehicle in the center of its lane Technical field of the invention

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

It applies more particularly to cars and other motorized vehicles traveling on roads, but also applies to other areas such as robotics.

The invention relates to a method of assisting the piloting of a motor vehicle to keep it in the center of its lane, comprising steps of:
- acquisition of parameter values relating to the dynamics of the motor vehicle and its position in its lane, a first of said parameters being an integral function, and
- determination of a steering angle setpoint for the motor vehicle by means of a controller, based on the acquired values and nominal reference values of said parameters.

It also relates to a motor vehicle adapted to implement such a control method.

State of the art

In order to make motor vehicles safer, they are currently equipped with driver assistance systems and even highly automated driving systems.

Among these systems, we find in particular lane centering systems (better known by the English acronym LCA for “Lane Centering Assist”).

To implement such an “LCA system”, the motor vehicle is equipped with a series of sensors making it possible to acquire data characterizing the state of the motor vehicle and its environment, and with software making it possible to analyze this data. in order to generate commands to steer the motor vehicle in order to keep it in the center of its lane.

The software is based on a regulator which takes the form of status feedback, for example. For example, it is possible to use a double regulation loop which includes:
- an open loop term which allows the curvature of the road to be taken into account, by calculating the steering wheel angle necessary to follow this curvature, and
- a closed loop term (like “state feedback”) which calculates the steering wheel angle necessary to maintain or align the vehicle relative to the center of its lane considering that it is a straight line .

The term closed loop uses a state vector that has the values of several parameters, one of which is an integral calculated based on previous states.

The LCA systems are designed to be activated particularly in the event of heavy traffic on the track (as part of driving aids in traffic). They are then designed in particular to be used within the framework of level 2 driving aids (within the meaning of the standard defined by the SAE – Society of American Automotive Engineers), that is to say aids requiring that the driver keeps his hands on the steering wheel.

We then understand that the driver must be able to easily regain control of the vehicle at any time. Therefore, the solution generally used consists of measuring the torque applied by the driver to the steering wheel, then, as soon as this torque exceeds a threshold, to deactivate this LCA system. The rest of the time, the torque exerted on the steering wheel is considered a simple disturbance.

We therefore understand that, as soon as a significant torque is exerted on the steering wheel, the driver is then forced to manually reactivate the LCA function. To avoid this when conditions permit (typically when the driver exerts moderate effort on the steering wheel in order to slightly and temporarily correct the trajectory of the vehicle), we want to allow the LCA system not to completely inactivate itself, but rather to 'interrupt momentarily.

The difficulty is then that when the LCA system is automatically reactivated, the calculated steering instruction is such that it can generate a strong jerk on the steering wheel.

The problem is in fact that the integral term of the state vector considered in the closed loop continued to be integrated so much so that it could significantly drift and no longer correspond to the situation.

A solution to reduce this problem could consist of freezing its value, but here again, this value would generally no longer correspond to the situation at the time of reactivation of the LCA system, which would still generate an uncomfortable shock for vehicle passengers. (and would slow down the vehicle's return to the center of its lane).

Presentation of the invention

In order to remedy the aforementioned drawback of the state of the art, the present invention proposes a solution to allow, at the moment when the LCA system is automatically reactivated, to guarantee comfortable and efficient steering of the vehicle towards the center of its lane. of circulation.

More particularly, according to the invention we propose a control method as defined in the introduction, in which, when the implementation of the control method has been suspended and then it resumes:
- the steering angle is acquired (preferably measured) and
- the reference value of said first parameter (the one which is an integral function) is modified so as to minimize the difference between the acquired steering angle and the steering angle setpoint.

Thus, thanks to the invention, at the time of resuming the LCA process, the integral term (which includes time t as an integration variable) is calculated not according to the previous states of the system, but in such a way that the steering angle instruction is equal to the instantaneous steering angle of the vehicle, which guarantees the absence of jerking at the steering wheel.

Thus, driving the motor vehicle at the time of reactivation of the LCA system can be smooth and efficient at the same time.

Preferably, the reference values of one or more other parameters are modified to correspond to the instantaneous values (measured or acquired) of these parameters. Thus, the regulation will not seek to directly bring the motor vehicle back towards the center of its lane but first of all to stabilize it on its current trajectory. By gradually returning the reference value(s) to its nominal value(s) (which correspond to the lane center), it is then possible to gradually bring the vehicle back toward the center of its lane.

Other advantageous and non-limiting characteristics of the * in accordance with the invention, taken individually or in all technically possible combinations, are as follows:

- at least a second of said parameters relates to the position of the motor vehicle in its lane;

- when the implementation of the control method resumes, the value of said at least one second parameter is acquired and is used as a reference value of said at least one second parameter, then, at subsequent times, the reference value of said at least a second parameter is modified so as to gradually return to its nominal reference value;

- when the implementation of the control method resumes, the values of the first two parameters are acquired and are used as reference values of said at least one second parameter, then these reference values are modified so as to gradually return to their value of nominal reference;

- said second parameter is a heading angle of the motor vehicle relative to its lane;

- said second parameter is a lateral distance between the motor vehicle and the center of its lane;

- to gradually return to its nominal reference value, the reference value of said at least one second parameter is calculated by means of a filtering function, preferably a low-pass filtering function;

- the first parameter is an integral function of position data of the motor vehicle in its lane, and preferably an integral function of a lateral distance between the motor vehicle and the center of its lane;

- the parameter values are acquired using a state observer;

- the steering angle setpoint of the motor vehicle is equal to the sum of a first component coming from said controller and a second component depending on the curvature of the traffic lane;

- it is planned to suspend the implementation of the control method as long as a driver of the motor vehicle exerts a torque on a steering wheel greater than a predetermined threshold.

The invention also proposes a motor vehicle comprising a power steering actuator and a computer adapted to control the power steering actuator, programmed to implement a control method as mentioned above.

Of course, the different characteristics, variants and embodiments of the invention can be associated with each other in various combinations as long as they are not incompatible or exclusive of each other.

Detailed description of the invention

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

On the attached drawings:

is a schematic top view of a motor vehicle traveling on a road;

represents a functional diagram of the calculations for implementing a method of controlling the motor vehicle of the ;

is a graph illustrating the variations over time of a nominal reference value, a modified reference value, and a real value of the lateral distance between the motor vehicle and the center of its lane;

illustrates the variations over time of four trajectory tracking parameters, in a particular situation.

On the , there is shown a motor vehicle 10 conventionally comprising a chassis, two front steering wheels 11, and two non-steering rear wheels 12. Alternatively, these two rear wheels could also be steered with an adaptation of the control law.

This motor vehicle 10 includes a conventional steering system making it possible to act on the orientation of the steering wheels so as to be able to turn the vehicle. This conventional steering system notably includes a steering wheel connected to rods in order to rotate the steering wheels. In the example considered, it also comprises at least one actuator making it possible to act on the orientation of the steering wheels as a function of the orientation of the steering wheel and/or as a function of a request received from a computer 13. This actuator power steering can, for this, act on the steering column of the vehicle (which is attached to the steering wheel) or on a rack (which connects the steering column to the steering wheels). Of course, the actuator could be arranged differently.

The computer 13 is then designed to control the power steering actuator. To this end, it comprises at least one processor, at least one memory and different input and output interfaces.

Thanks to its input interfaces, the computer 13 is adapted to receive input signals coming from different sensors.

Among these sensors, for example, a front camera is provided, making it possible to identify the position of the vehicle in relation to its lane.

An angle sensor is also provided to measure the steering angle of the steering wheels.

Thanks to its output interfaces, the computer 13 is adapted to transmit a setpoint to the power steering actuator.

Thanks to its memory, the computer 13 stores data used as part of the process described below. It stores in particular a computer application, made up of computer programs comprising instructions whose execution by the processor allows the implementation by the computer of the process described below.

This method allows the motor vehicle 10 to follow a reference trajectory corresponding to the central line T0 of its traffic lane 30 (which is here defined between a road edge and a discontinuous ground marking line).

Before describing the process according to the invention in more detail, we can introduce the different variables which will be used, some of which are illustrated in the .

The total mass of the motor vehicle will be denoted “m” and will be expressed in kg.

The center of gravity of the vehicle will be noted “CG”.

The mass of the vehicle which is exerted on the front set of wheels will be denoted “M _f ” and will be expressed in kg.

The mass of the vehicle which is exerted on the rear set of wheels will be denoted “M _r ” and will be expressed in kg.

The wheelbase of the vehicle, that is to say the distance between the axes of these two wheel sets, will be denoted “L” and will be expressed in meters.

The pneumatic rigidity of the rear wheels will be noted C _r and will be expressed in Newton/rad.

The pneumatic rigidity of the front wheels will be noted C _f and will be expressed in Newton/rad.

We can consider an orthogonal reference frame (CG, X, Y, Z) attached to the vehicle. Its origin is confused with the CG center of gravity. The X axis corresponds to the longitudinal axis of the vehicle facing the front of the vehicle. The Y axis corresponds to the side axis facing the left of the vehicle. 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.

The steering angle that the front steering wheels make with the longitudinal axis X of the motor vehicle 10 will be denoted “δ” and will be expressed in rad.

Note that the steering wheel angle and the steering angle δ are directly linked, with a gear ratio or even first or second order dynamics. We then consider in the following only the steering angle δ at the wheels.

The steering speed of the front wheels will be noted “dδ/dt”.

The longitudinal speed of the vehicle, along the X axis, will be noted v and will be expressed in m/s.

The relative heading angle between the axis

The yaw speed of vehicle 1, that is to say its rotation speed around the Z axis, will be noted “dψ/dt”.

The lateral position error, also called lateral deviation, between the center of gravity CG of the vehicle and the center line T0 will be noted y.

The lateral speed of the vehicle will be noted “dy/dt”.

At this stage, we can also introduce a notion of “position error integral”, which corresponds to the time integral of the lateral deviations y in relation to the central line T0. This error integral will be denoted “∫-y.dt”.

The curvature of the central line T0 of the taxiway is noted ρ (in m ^-1 ). This is the inverse of its radius of curvature, either at the vehicle or at a distance from it.

The method of controlling the motor vehicle 10 is designed to allow this vehicle to follow the central line T0 of its lane, in autonomous mode (without driver intervention).

This process is implemented when the system for keeping the vehicle in the center of its lane (hereinafter called LCA system) is activated.

How to activate this system and detect the center line T0 of the taxiway will not be described here.

However, we can briefly describe how the vehicle is kept in the center of its lane when the LCA system is activated and operates nominally. We will then describe how it works when it has been temporarily deactivated and then reactivates automatically.

Thus, we will distinguish a nominal operation of this system from a particular operation during its reactivation.

To establish the vehicle control law and thus regulate the steering angle δ of the motor vehicle 10 so that the latter remains in the center of its lane, this vehicle was modeled using a bicycle model.

In such a model, the two wheels of the front axle are considered to be the same, and the same goes for the two rear wheels. The chassis of the vehicle is modeled by a body which connects the two wheel models.

The dynamics of the motor vehicle 10 can then be represented by a state vector X, which is expressed here in the form:

We observe here that one of the terms of this state vector is an integral function depending on the previous states of the motor vehicle 10. This term corresponds here more precisely to the error integral introduced above.

According to the “bicycle” model used, the equation of this system is written in the following form:

In this equation, the term δ _FBK is a first component of the steering angle instruction δ which will be transmitted to the power steering actuator. As will appear more clearly below, this component makes it possible to keep the vehicle in the center of the traffic lane considering that the latter is straight.

A, C, B _δ and B _ρ are determined matrices and vectors.

The first of the Math2 equations then introduces two terms, including an open loop term B _ρ .ρ and a closed loop term B _δ .δ _FBK . The open loop term is intended to compensate for the steering angle δ taking into account the curvature of the center line T0. The closed loop term makes it possible to calculate the steering angle by considering that the traffic lane is straight.

Y represents the measurement vector, and it therefore depends on the state X.

The matrix A is expressed in the following form:

The matrix C is expressed in the following form:

The matrix B _δ is expressed in the following form:

The matrix B _ρ is expressed in the following form:

In reference to the , we have schematically represented by a block diagram the topology of an example of LCA system.

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

The function of the open loop 21 is to take into account the curvature of the road and to compensate for the effect of the turn on the states and the control.

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

We therefore find the two terms introduced above.

The terms resulting from these two loops, namely the components δ _FBK and δ _FFD , are added using an adder 27.

The steering angle δ to be transmitted to the front wheel so that the vehicle 1 moves in a bend presenting a known curvature ρ thus depends on the two previous components, so that we can write:

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

The open loop 21 comprises an anticipating element 24. This anticipating element 24 takes into account the curvature ρ of the traffic lane (calculated for example from the images obtained by the camera) in order to evaluate the component δ _FFD of the angle steering δ. This open loop is generally known by the Anglo-Saxon name “feed forward”.

Considering the bicycle model in steady state (with dX/dt = 0), and assuming the vehicle at the center of its lane (dy/dt = 0 and y=0) and in an established turn (dδ/dt=0), we can then write:

In this equation, ∇ _SV is the understeer gradient specific to the vehicle, which is classically defined by the following expression:

In other words, the component δ _FFD of the steering angle δ presents a term ρL which is determined according to the curvature of the turn and the architecture of the vehicle, and a term which allows the drift to be taken into account of the vehicle when turning.

The closed loop 25 includes an observer element 26 which makes it possible to observe the state X _obs of the motor vehicle 10.

It also includes a comparator 28 making it possible to differentiate between a reference state X _ref and this observed state X _obs . This difference forms an X _err error.

It finally includes a controller 20 which collects the signal delivered by the comparator 28 and generates the component δ _{F BK} of the steering angle δ.

This controller 20 in practice includes a gain Ks in the form of a vector which, once multiplied by the error X _err , makes it possible to calculate the component δ _{F BK} .

The state observer 26 collects a measurement vector Y _mes (comprising measured values, such as in particular the steering angle) and delivers the observed state X _obs .

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

This state observer 26 is used to estimate the unmeasured values of the model parameters. These unmeasured values are for example dy/dt and dδ/dt.

Note here that as a variant, we could do without this observer if all the values were measured.

Noting state vector estimation , the observer equation can be written as:

with L _P a gain value associated with the observer element 26.

As a general rule, the control implemented by the closed loop 25 aims to minimize the state vector X around a zero reference state X _ref corresponding to a straight line. In other words, the nominal reference values (under nominal driving conditions) are such that we can write:

In summary, when the LCA system is activated and operating at nominal speed, it is intended to measure the variables of the measurement vector Y _mes and the curvature ρ of the taxiway.

This curvature makes it possible to calculate the component δ _FFD .

The measured variables make it possible, thanks to the state observer 26, to determine the values X _{obs , i} of the parameters of the state vector X (also called state variables and denoted: ψ, dψ/dt, y, dy /dt, δ, dδ/dt, ∫-y.dt).

The vector X _err making the difference between these observed values X _{obs , i} and the _{corresponding nominal reference values} .

There are situations in which regulation at nominal speed must be temporarily interrupted.

This is for example the case when the driver exerts a torque on the steering wheel for a limited period of time which is greater than a simple disturbance but lower than a threshold beyond which the LCA system is completely deactivated.

Typically, this duration is 50ms and this threshold is 4Nm of torque at the wheel.

This is also the case in strong turns, when the steering angle or the lateral deviation exceeds a threshold.

This is also the case when the longitudinal speed of the vehicle becomes lower than a threshold (2 km/h for example).

Other situations could also be considered.

When the LCA system automatically reactivates (i.e. when the situation in question ceases), the error integral ∫-y.dt cannot be used (the cumulative value in the integral does not is generally not the right one).

When the LCA system reactivates automatically (hereinafter we will speak of reactivation instant) and in the seconds which follow (hereinafter we will speak of reactivation phase), the invention proposes to modify the algorithm presented above so that this recovery takes place without generating any jerks at the wheel. The nominal operation described above is planned to resume afterwards.

The idea consists, during the reactivation phase, of modifying the reference vector X _ref in order to take this particular situation into account.

Thus, at the instant of reactivation, the reference vector X _ref is modified to have at least two non-zero terms.

These terms are preferably the heading angle Ψ and the lateral deviation y. Note that the objective remains that the error integral ∫-y.dt tends towards 0.

Here, the two terms corresponding to the heading angle Ψ and the lateral deviation y are considered non-zero.

We can therefore write, at the moment of reactivation:

With Ψ _ref and y _ref not zero.

We can first explain what values are assigned to the terms X _ref,2 and X _ref,4 .

At the moment of reactivation, these two terms are chosen equal to their real (or estimated) values. These values are then, for example, measured on the images acquired by the front camera of the motor vehicle. Alternatively, they could be estimated differently.

The idea here is not to force the motor vehicle to return suddenly towards the central line T0, but to make it return gradually towards this line.

Then, throughout the reactivation phase, the values of these terms will gradually tend towards zero.

The reactivation phase preferably has a duration greater than one second, during which these two terms will remain non-zero.

The variation of these two terms will be continuous, which will allow a significant improvement in control (less oscillations, no overshoot, smoother regulation, etc.).

To vary these terms X _ref,2 and X _ref,4 , we can use any suitable continuous function.

Here, it is chosen to vary these two terms according to their values measured at the current time step t, and according to their values calculated at the previous time step t-1. We thus achieve a sort of smoothing by low-pass filtering.

This is more precisely a smoothing using an “exponential moving average”.

We can therefore write:

In each of these equations, the constant w is the weight given to each of the two terms of the equation. It is identical here in both equations but could differ.

It is preferably greater than 0.99. For example, it is chosen equal to 0.9975. This weight thus makes it possible to have a reactivation phase of reasonable convergence duration.

On the , curve C1 represents the nominal reference value X _ref,2 , that is to say the reference value of the lateral deviation y in nominal operating mode. We observe that this value remains zero.

Curve C3 corresponds to the real (measured) value of the lateral deviation y. We observe on this that at 42 seconds on the abscissa scale, the real lateral deviation y increases. This is due to wheel steering imposed by the driver.

Curve C2 represents the reference value X _ref,2 taken during the reactivation phase. We observe that this value takes on a non-zero value at the time of reactivation (at 60 seconds) equal to the real value, then that it returns towards zero in a continuous and continuously differentiable manner. The reactivation phase then lasts 20 seconds.

For information purposes, we note on this that at 72 seconds on the abscissa scale, the real lateral deviation y diverges momentarily. This is due to the fact that the vehicle is approaching a curve and deviates a little from the center of the traffic lane at the start of this curve.

At this stage, we can now describe how the term X _ref,7 , which corresponds to the reference value of the error integral ∫-y.dt, is calculated.

Here, the objective of this calculation is to ensure that this term compensates for the steering angle errors that could be made in order not to generate jerks to the steering wheel at the moment of reactivation.

To do this, the value δ _Measured of the steering angle is measured, then _the reference _value calculated at the previous time step).

Here, note that the measured value comes from a measurement of a steering wheel angle which, taking into account a reduction, makes it possible to obtain a steering angle of the wheels. Alternatively, this value could be obtained by calculation, for example using another observer.

So, we can write:

With

Or

In these equations, the Ks _i values correspond to the terms of the vector forming the gain Ks of the corrector.

Therefore, the initial value of the error integral is determined via the equation:

Note here that this calculation can be simplified.

Indeed, we can consider that the terms ΔX ₂ and ΔX ₄ are zero.

On the , to clearly illustrate the operation of the invention, the variations of four parameters have been represented in a particular situation, which is as follows.

The motor vehicle enters a bend at time t1. At time t2, the driver regains control so that the LCA system becomes inactivated. At time t3, the driver gives up control, so that the LCA system is automatically reactivated. Finally, at approximately time t4, the vehicle exits the turn.

Curve C10 represents the variation in the steering angle when calculated using the method according to the invention. Curve C11 represents this same parameter when it is calculated according to a method different from the invention, namely in the event where during reactivation, the reference vector X _ref remained zero and where, during the duration of deactivation , the value of the integral term X _obs,7 of the observed state was frozen. We note that thanks to the invention, at time t3, no sudden variation in the steering angle is expected.

Curve C12 represents the variation in the value of the integral term X _obs,7 when it is determined using the method according to the invention. Curve C13 represents this same parameter when it is determined according to the different method of the invention (when its value is frozen during the interruption of the LCA system).

Curve C14 represents the variation in the actual value of the lateral deviation y when it is determined using the method according to the invention. Curve C15 represents this same parameter when it is determined according to the different method of the invention. Here again, we observe that at time t3, the invention makes it possible to avoid any divergence of this lateral deviation y, but on the contrary a gentle and progressive convergence towards 0.

The present invention is in no way limited to the embodiment described and represented, but those skilled in the art will be able to make any variation conforming to the invention.

By way of example, in the embodiment described above, the parameter of the state vector which is an integral function ∫-y.dt and which is calculated according to the previous states corresponds to the integral of the lateral distance y between the motor vehicle and the center of its lane. Alternatively, the integral function could be relative to another parameter, typically to the relative heading angle between the vehicle and the traffic lane. More generally, the state vector parameters could be different from those presented above.

Claims (11)

Method of assisting the piloting of a motor vehicle (10) to keep it in the center of its lane (30), comprising steps of:
- acquisition of values (X _{obs , i} ) of parameters (ψ, dψ/dt, y, dy/dt, δ, dδ/dt, ∫-y.dt) relating to the dynamics of the motor vehicle (10) and its position in its lane (30), a first of said parameters (∫-y.dt) being an integral function,
- determination of a steering angle setpoint (δ) of the motor vehicle (10) by means of a controller (20), based on the values (X _{obs , i} ) acquired and reference values (X _{ref, i} ) nominal values of said parameters (ψ, dψ/dt, y, dy/dt, δ, dδ/dt, ∫-y.dt), characterized in that, when the implementation of the control method has been suspended then that 'it resumes, the steering angle (δ _Measured ) is acquired and the reference value (X _ref,7 ) of said first parameter (∫-y.dt) is modified so as to minimize the difference between the angle of steering angle (δ _Measured ) acquired and the steering angle reference (δ). Control method according to claim 1, in which, at least a second of said parameters (y, ψ) being relative to the position of the motor vehicle (10) in its lane (30),
- when the implementation of the control method resumes, the value of said at least one second parameter (y, ψ) is acquired and is used as a reference value (X _ref,2 , X _ref,4 ) of said at least one second parameter (y, ψ), then, at subsequent times,
- the reference value (X _ref,2 , X _ref,4 ) of said at least one second parameter (y, ψ) is modified so as to gradually return to its nominal reference value. Control method according to claim 2, in which, when the implementation of the control method resumes, the values of two first parameters (y, ψ) are acquired and are used as reference values (X _{ref, 2} , X _{ref ,4} ) of said at least one second parameter (y, ψ), then these reference values (X _ref,2 , X _ref,4 ) are modified so as to gradually return to their nominal reference value. Control method according to one of claims 2 and 3, in which said second parameter is a heading angle (ψ) of the motor vehicle (10) relative to its lane (30). Control method according to one of claims 2 to 4, in which said second parameter is a lateral distance (y) between the motor vehicle (10) and the center of its lane (30). Control method according to one of claims 2 to 5, in which, to gradually return to its nominal reference value, the reference value (X _ref,2 , X _ref,4 ) of said at least one second parameter (y, ψ) is calculated using a filtering function, preferably a low-pass filtering function. Control method according to one of claims 1 to 6, in which the first parameter (∫-y.dt) is an integral function of position data of the motor vehicle (10) in its lane (30), and preferably an integral function of a lateral distance (y) between the motor vehicle (10) and the center of its lane (30). Control method according to one of claims 1 to 7, in which the values (X _{obs , i} ) of the parameters (ψ, dψ/dt, y, dy/dt, δ, dδ/dt, ∫-y.dt) are acquired by means of a state observer (26). Control method according to one of claims 1 to 8, in which the steering angle setpoint (δ) of the motor vehicle (10) is equal to the sum of a first component (δ _FBK ) from said controller (20). ) and a second component (δ _{F FD} ) depending on the curvature (ρ) of the traffic lane (30). Control method according to one of claims 1 to 9, in which it is planned to suspend the implementation of the control method as long as a driver of the motor vehicle (10) exerts on a steering wheel a torque greater than a predetermined threshold . Motor vehicle (10) comprising a power steering actuator and a computer adapted to control the power steering actuator, characterized in that the actuator is programmed to implement a control method according to one of claims 1 to 10.