MANAGEMENT OF A MOTOR VEHICLE'S SPEED IN A CURVE

Abstract

The invention relates to a method for managing the speed of a motor vehicle in a curve. The invention also relates to a device (100) for carrying out such a method and to a motor vehicle comprising such a device.

Description

DESCRIPTION TITLE: Managing the speed of a motor vehicle in a bend The present invention claims priority from French application 2211781 filed on 14.11.2022, the content of which (text, drawings and claims) is incorporated herein by reference. Technical field of the invention

[0001] The present invention relates to the field of autonomous vehicles, in particular that of autonomous cars. The invention relates in particular to a method for managing the speed of a motor vehicle in a bend by means of a computer device on board the vehicle. The invention also relates to a device implementing such a method as well as a motor vehicle comprising such a device. The invention applies to motor vehicles such as land motor vehicles, in particular cars. State of the prior art

[0002] It is known that some current motor vehicle driver assistance systems, for example those fitted to certain cars, provide functionalities that enable the support of autonomous vehicle guidance in certain particular driving environments. It is also known that a driver tends to slow down when entering a bend, to modulate the speed of the vehicle in the bend according to the curvature of the bend and to gradually increase the speed of the vehicle as it approaches the exit of the bend. Indeed, for both safety and comfort reasons, a driver will generally maintain a relatively low lateral acceleration throughout the bend, of the order of 3 m. s 2 . Thus, to faithfully reproduce the behavior of a driver, a driving assistance system of a motor vehicle must manage the speed of a vehicle in a bend so as to slow down at the entrance to the bend, to modulate the vehicle's speed in the bend according to the curvature of the bend and to increase the vehicle's speed as it approaches the exit of the bend. To achieve this, the driver assistance system must be able to determine how to modulate the vehicle's speed throughout the bend. Summary of the invention

[0003] The invention aims to satisfy this need. The invention aims in particular to provide a method and a device that allow a driver assistance system to faithfully reproduce the behavior of a driver in a bend, in particular in terms of controlling the speed of the vehicle throughout the bend. The invention also aims to provide a solution that is capable of limiting the computing resources required for its implementation. By this means, the invention aims to improve both the comfort and the safety of vehicles equipped with driver assistance systems that assume autonomous guidance of the vehicles, in particular in bends.

[0004] In order to achieve these aims, the invention relates, according to a first aspect, to a method for managing the speed of a motor vehicle in a bend by means of a computer device on board the vehicle, the method comprising the steps of: i) obtaining, by interacting with a navigation system of the vehicle, data characterizing the evolution of the curvature of the roadway as a function of the distance traveled; ii) determining, on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a first location, said first location being situated towards the entrance of the bend; iii) determining, on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a second location, said second location being located towards the exit of the bend; iv) determining, on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a third location, said third location being located at a point where the curvature of the roadway is maximum; v) determining data characterizing a fourth location, said fourth location being located upstream of the third location and downstream of the first location; vi) determining data characterizing a fifth location, said fifth location being located downstream of the third location and upstream of the second location;and (vii) cause the vehicle speed to be managed based on data characterizing a first location, data characterizing a second location, data characterizing a fourth location and data characterizing a fifth location.;

[0005] Alternatively, step vii) may include causing the vehicle speed to decrease constantly between the first location and the fourth location, maintaining a constant speed between the fourth location and the fifth location, and increasing the speed constantly between the fifth location and the second location.

[0006] Alternatively, data characterizing a minimum curvature threshold value may be used in steps ii) and iii).

[0007] According to yet another variant, during step v), data characterizing the maximum slope of an affine function linking the curvature of the roadway at the first location and the curvature of the roadway at another location upstream of the third location can be determined, based on which data characterizing a fourth location are determined.

[0008] According to yet another variant, during step vi), data characterizing the minimum slope of an affine function linking the curvature of the roadway at the second location and the curvature of the roadway at another location downstream of the third location can be determined, based on which the data characterizing a fifth location are determined.

[0009] According to a second aspect, the invention relates to a device for managing the speed of a motor vehicle in a bend, the device comprising at least one information processing unit, comprising at least one processor, and a data storage medium configured to implement a method as described above.

[0010] According to a third aspect, the invention relates to a computer program comprising program code instructions for executing the steps of a method as described above when said program is executed by at least one processor.

[0011] According to a fourth aspect, the invention relates to a medium usable in a computer on which a program as described above is recorded.

[0012] According to a fifth aspect, the invention relates to a motor vehicle comprising a device as described above. Brief description of the figures

[0013] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0014] [Fig- 1] is a diagram of the context of the implementation of a method according to the invention;

[0015] [Fig. 2] is a functional diagram of a device according to the invention; and

[0016] [Fig. 3] is a flowchart of the steps of a method according to the invention;

[0017] [Fig. 4] is a graph illustrating at least one step of the method according to the invention;

[0018] [Fig. 5] is a graph illustrating at least one step of the method according to the invention;

[0019] [Fig. 6] is a graph illustrating the evolution of the speed of a motor vehicle according to the invention in a bend. Detailed description of the invention

[0020] Figure 1 schematically illustrates the context of the implementation of a method for managing the speed of a motor vehicle in a bend according to the invention described below by a device 100 for managing the speed of a vehicle in a bend according to the invention described below which is on board a motor vehicle equipped with a driving assistance system capable of autonomously managing the guidance of the vehicle. When implementing the method according to the invention, data characterizing the evolution of the curvature of the roadway in front of the vehicle as a function of the distance traveled are obtained, such as those illustrated by the graph in Figure 1. These data include a certain number of locations in front of the vehicle, corresponding on the graph to points where the curvature of the roadway is known. On the basis of these data, the device 100 according to the invention determines an estimate of an envelope minimalist of the road contour in each bend (vl, v2, v3), such an envelope having a trapezoidal shape, and it then causes an adaptation of the vehicle speed using this estimate. The vehicle's driver assistance system is thus able to manage the vehicle's speed in bends in a safe and comfortable manner, while minimizing the time it must spend and the computing resources it must use to enable this.

[0021] A device 100 for managing the speed of a motor vehicle in a bend according to the invention is illustrated in Figure 2. It is a computer device, which comprises at least one information processing unit 101, comprising one or more processors, a data storage medium 102, on which is recorded in particular a program which comprises program code instructions for the execution of the steps of the method according to the invention described below, and an input and output interface 103 allowing the reception and transmission of data.

[0022] According to one embodiment of the invention, the device 100 according to the invention is hosted on one or more computers or other electronic control units of the vehicle. According to the preferred embodiment, the device 100 according to the invention is hosted on an independent computer and it interacts via its input and output interface 103 and by means of a wired communication network of the vehicle (e.g. CAN, Ethernet) with a computer of the driving assistance system of the vehicle, which, according to the invention, provides at least one autonomous driving functionality. According to another embodiment, the device 100 according to the invention is an integral part of a computer of the driving assistance system.

[0023] Thus, whatever the embodiment, the device 100 according to the invention is always able to interact, by means of its interface input and output 103, not only with the vehicle's driving assistance system, but also, via the latter, with any other equipment which equips and / or interacts with the driving assistance system. However, according to the invention, the vehicle's driving assistance system interacts in particular with a vehicle navigation system (e.g. GPS), which, at a minimum, is able to provide data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, and therefore of the bends which it delimits. Thus, by being an integral part of or by interacting with such a driving assistance system, the device 100 according to the invention is advantageously able, in particular, to obtain data characterizing the evolution of the curvature of the roadway as a function of the distance traveled.

[0024] According to the invention, all the elements described above contribute to enabling the implementation on board a motor vehicle of a method for managing the speed of a motor vehicle in a bend according to the invention, as described below in connection with figures 3-7.

[0025] According to a first step 201 of the method according to the invention, the device 100 according to the invention obtains data characterizing the evolution of the curvature of the roadway as a function of the distance traveled. Preferably, this data is obtained by interacting with a navigation system of the vehicle, for example a navigation system which itself receives this data from an intelligent transport system by means of conventional wireless communication networks and protocols. Thus, at the end of this first step of the method according to the invention, data are for example obtained which determine the graph illustrated in FIG. 4, which forms a representation of a bend on the roadway in an orthogonal reference frame.

[0026] Then, according to a second step 202 of the method according to the invention, the device 100 according to the invention uses the data characterizing the evolution of the curvature according to the distance traveled to determine data characterizing a first location located towards the entrance of the bend. In other words, the device 100 according to the invention is busy at this stage determining a first point that it considers to mark the start of the bend (Pstart). Preferably, it uses to do this data characterizing a minimum curvature threshold value (par_C), considering the first point whose curvature exceeds the minimum curvature threshold value as marking the start of the bend. The device 100 according to the invention deduces therefrom the distance at which the first location is located (Dstart).

[0027] Similarly, according to a third step 203 of the method according to the invention, the device 100 according to the invention uses the data characterizing the evolution of the curvature according to the distance traveled to determine data characterizing a second location located towards the exit of the bend, more specifically the point that it considers to mark the end of the bend (Pfin), by selecting in this case the last point for which the curvature of the roadway remains greater than the minimum curvature threshold value (par_C). It deduces therefrom the distance at which the second location is located (Dfin).

[0028] Then, according to a fourth step 204 of the method according to the invention, the device 100 according to the invention uses the data characterizing the evolution of the curvature according to the distance traveled to determine data characterizing a third location located at a place where the curvature of the roadway is maximum (Pcmax), from which it deduces the distance at which this third location is located (Dcmax).

[0029] Then, according to a fifth step 205 of the method according to the invention, the device 100 according to the invention determines data characterizing a fourth location located upstream of the third location and downstream of the first location. At this stage, the device 100 according to the invention therefore seeks to form the minimalist envelope of the bend around the heart of the bend, where the curvature of the roadway is maximum. To do this, in order to determine the fourth location, a first vertex of the trapezoid illustrated in Figure 5, the device 100 according to the invention determines data characterizing the maximum slope of an affine function linking the curvature of the roadway to the first location (Pdebut), the one considered as marking the start of the bend, and the curvature of the roadway to another location upstream of the third location (Pcmax), based on which it then determines the data characterizing a fourth location, and therefore a first vertex of the trapezoid.Indeed, by using the first point (Pdebut) and each point prior to the point where the curvature of the roadway is maximum (each point prior to Pcmax), the device 100 according to the invention determines the maximum slope of an affine function connecting the first point to another point, which it then uses to deduce the distance at which the fourth location is located (Dliml). Mathematically, the device 100 according to the invention will here determine the coordinates of a first limiting point Pliml(Dliml, Cmax), and it achieves this by successively solving the equations:. Tmax=max(Tp_idebut+l,...,Tp_icmax) with Tp_n=(Cn-Cdebut) / (Dn-Dedut) and Dliml= (Cmax-Cdebut) / Tmax+Ddebut.

[0030] Similarly, according to a sixth step 206 of the method according to the invention, the device 100 according to the invention determines data characterizing a fifth location located downstream of the third location and upstream of the second location. At this stage, the device 100 according to the invention therefore seeks to complete the minimalist envelope of the bend around the heart of the bend. To do this, in order to determine the fifth location, a second vertex of the trapezium, the device 100 according to the invention this time determines data characterizing the minimum slope of an affine function connecting the curvature of the roadway at the second location (Pfin), the one considered as marking the end of the bend, and the curvature of the roadway at another location downstream of the third location, based on which it then determines the data characterizing a fifth location, and therefore a second vertex of the trapezoid. Indeed, by using the last point (Pfin) and each point after the point where the curvature of the roadway is maximum (each point after Pcmax), the device 100 according to the invention determines the minimum slope of an affine function connecting the last point to another point, which it then uses to deduce the distance to the fifth location (Dlim2). Mathematically, the device 100 according to the invention will here determine the coordinates of a second limiting point Plim2(Dlim2, Cmax), and it achieves this by successively solving the equations: Tmin=min(Tp_icmax,...,Tp_ifin-l) with Tp_n=(Cfin-Cn) / (Dfin-Dn) and Dlim2=(Cmax-Cfin) / Tmin+Dfin.

[0031] Finally, according to a seventh step 207 of the method according to the invention, the device 100 according to the invention causes the management of the speed of the vehicle as a function of the data characterizing a first location, the data characterizing a second location, the data characterizing a fourth location and the data characterizing a fifth location. In other words, at this stage of the method, the device 100 according to the invention instructs the vehicle driving assistance system to manage the speed of the vehicle as a function of the points which form the trapezoid illustrated in Figure 5, namely Pstart, Plim1, Plim2 and Pfin.Preferably, as illustrated in Figure 6, the device 100 according to the invention then causes a constant reduction in the speed of the vehicle between the first location (D start) and the fourth location (Dliml), the maintenance of a constant speed between the fourth location (Dliml) and the fifth location (DLim2) and the constant increase in speed between the fifth location (Dlim2) and the second location (Dfin).

[0032] Thus, thanks to the method and the device according to the invention described above, a solution is provided to enable a driving assistance system of a motor vehicle to faithfully reproduce the behavior of a driver in a bend, in particular in terms of controlling the speed of the vehicle throughout the bend. In this way, the invention contributes to improving both the comfort and the safety of vehicles equipped with driving assistance systems which assume the autonomous guidance of vehicles, in particular in bends.

Claims

CLAIMS:

1. Method for managing the speed of a motor vehicle in a bend by means of a computer device (100) on board the vehicle, characterized in that the method comprises the steps of: i) obtaining (201), by interacting with a navigation system of the vehicle, data characterizing the evolution of the curvature of the roadway as a function of the distance traveled; ii) determining (202), on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a first location, said first location being located towards the entrance of the bend; iii) determining (203), on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a second location, said second location being located towards the exit of the bend;iv) determining (204), on the basis of the data characterizing the evolution of the curvature of the roadway as a function of the distance traveled, data characterizing a third location, said third location being located at a place where the curvature of the roadway is maximum; v) determining (205) data characterizing a fourth location, said fourth location being located upstream of the third location and downstream of the first location; vi) determining (206) data characterizing a fifth location, said fifth location being located downstream of the third location and upstream of the second location; and vii) causing (207) the management of the speed of the vehicle as a function of the data characterizing a first location, the data characterizing a second location, the data characterizing a fourth location and the data characterizing a fifth location.; Method according to claim 1, characterized in that step vii) consists of causing a constant decrease in the speed of the vehicle between the first location and the fourth location, maintaining a constant speed between the fourth location and the fifth location and constantly increasing the speed between the fifth location and the second location. Method according to one of the preceding claims, characterized in that data characterizing a minimum curvature threshold value are used during steps ii) and iii). Method according to one of the preceding claims, characterized in that, during step v), data characterizing the maximum slope of an affine function linking the curvature of the roadway at the first location and the curvature of the roadway at another location upstream of the third location are determined, on the basis of which data characterizing a fourth location are determined.Method according to one of the preceding claims, characterized in that, during step vi), data characterizing the minimum slope of an affine function linking the curvature of the roadway at the second location and the curvature of the roadway at another location downstream of the third location are determined, as a function of which the data characterizing a fifth location are determined. Device (100) for managing the speed of a motor vehicle in a bend, characterized in that the device comprises at least one information processing unit (101), comprising at least one processor, and a data storage medium (102) configured to implement a method according to any one of the preceding claims. Computer program comprising program code instructions for executing the steps of a method according to any one of claims 1 to 5 when said program is executed by at least one processor. Medium usable in a computer, characterized in that a program according to claim 7 is recorded therein. Motor vehicle, characterized in that it comprises a device (100) according to claim 6.