Method for programming a route planner for a motor vehicle, and vehicle implementing the method

Abstract

The invention relates to a method for programming a route planner configured to generate a nonlinear longitudinal speed profile from a target speed and a distance at which that speed is to be reached, as well as a vehicle implementing the method. The method comprises: determining (101) a target speed equal to a setpoint speed, and a target distance from the target speed and a time horizon; calculating (102) a predicted distance to a target vehicle at the end of the time horizon, and when this distance is greater than a safety distance, using a predicted speed of the target vehicle as the target speed, and adding the predicted distance less the safety distance to the target distance; programming (103) the route planner with the target speed and the target distance. Figure for the abstract: Fig. 1

Description

Title of the invention: Method for programming a route planner for a motor vehicle, and vehicle implementing the method technical field

[0001] The invention is in the field of driver assistance technologies for motor vehicles, and relates more particularly to a method of programming a route planner for a motor vehicle, in particular in the context of automatic adaptation of the vehicle's speed. Previous technique

[0002] Motor vehicles are now equipped with advanced driver assistance systems, in English "Advanced Driver Assistance Systems" or AD AS.

[0003] ADAS include a wide range of driver assistance technologies, such as ACC (Adaptive Cruise Control), automatic emergency braking, lane keeping assist, collision warnings, parking sensors, etc. Their common goal is to improve safety and driving comfort by helping drivers better control their vehicle and avoid road accidents.

[0004] Adaptive cruise control is a system that maintains a constant vehicle speed while automatically adjusting the distance to vehicles in front. This makes driving easier and therefore reduces driver fatigue, while ensuring that safe distances are maintained.

[0005] ACC relies on another ADAS device called a "path planner." This is an algorithm that generates an optimal trajectory for a vehicle, based on various parameters such as speed, obstacle position, etc. The path planner works in conjunction with other ADAS system components, such as sensors, computers, and actuators, to ensure safe and precise driving. In particular, the path planner determines the longitudinal speed profile that the vehicle uses as a reference to follow.

[0006] This longitudinal velocity varies according to different parameters: - the target speed set by the driver, - the presence of contextual elements related to the road (speed signs, bends, roundabouts, etc.), - the presence of other vehicles or objects on the trajectory of the ego vehicle (the ego vehicle is the vehicle controlled by the trajectory planner).

[0007] The trajectory planner generally has two main operating modes for ACC: - Cruise mode (also known as "cruise" mode) - Following mode (also known as "following" mode)

[0008] Cruise mode corresponds to the case where there is no vehicle in front of the ego vehicle, or where the vehicles preceding the ego vehicle are traveling at a higher speed. In this case, the speed of the ego vehicle is controlled by a set speed. This speed can be set by the vehicle's driver or derived from the road conditions.

[0009] The pursuit mode corresponds to the case where one or more vehicles are present in the path of the ego vehicle. Subsequently, the vehicle preceding the ego vehicle is designated as the target vehicle. In this case, the speed of the ego vehicle is adjusted so that the distance to the target vehicle is equal to a given safety distance, while being less than or equal to the set speed.

[0010] In both cases, speed control is done according to a closed loop, and speed variations (for example in the case of a change in the speed setpoint in cruise mode) follow an acceleration profile bounded in acceleration and jerk, the jerk being the square of the vehicle's acceleration.

[0011] Recent trajectory planners, such as the one described in patent application FR3,104,519 Bl, are capable of generating nonlinear longitudinal velocity profiles. Developing these nonlinear longitudinal velocity profiles involves optimizing the vehicle's acceleration and jerk, minimizing jerk and making acceleration gradual, with the goal of reaching the target speed after a given distance. This optimization provides increased driving comfort for vehicle occupants, as acceleration is less abrupt.

[0012] Today, nonlinear longitudinal speed profiles are used in contextual ACC in cruise mode to adapt the vehicle's speed in response to a known contextual element occurring at a known location (e.g., a change in speed limit, an intersection, a curve, etc.). They are not used in cruise mode when the set speed changes unrelated to a contextual element, or in pursuit mode, because these modes do not have a concept of distance at which the target speed must be reached.

[0013] An object of the invention is therefore to allow the use of nonlinear velocity profile generators in the other modes of the trajectory planner, namely Cruise mode in case the driver changes the set speed, and pursuit mode. The use of a non-linear speed profile for these trajectory planner operating modes improves vehicle user comfort because it also optimizes vehicle jerk and acceleration. Summary of the invention

[0014] To this end, the present invention describes a method for programming a route planner for a motor vehicle, referred to as the ego vehicle. The route planner is configured to generate a non-linear longitudinal speed profile from a target speed and a distance at which said target speed must be reached.

[0015] The method according to the invention comprises: - a step of determining a target speed equal to a setpoint speed L, and of determining a target distance da at which the vehicle ego must reach the target speed vo, from the target speed v» and a predefined time horizon TH; - a step implemented when a vehicle, called the target vehicle, is in front of the ego vehicle, of calculating a predicted distance between the ego vehicle and the target vehicle at the end of the time horizon TH, and when the predicted distance is greater than a safety distance dref, of using a predicted speed vt of the target vehicle at the end of the time horizon TH as the target speed and of adding the predicted distance j minus the safety distance dref to the target distance d0; - a step of programming the route planner using the target speed v<> as the speed setpoint and the target distance (^as the distance at which the target speed v» must be reached.

[0016] Advantageously, the non-linear longitudinal velocity profile is generated in such a way as to optimize the acceleration and jerk of the ego vehicle.

[0017] According to one embodiment of the invention, the route planner comprises at least one operating mode, referred to as cruise mode, in which the longitudinal speed of the vehicle is controlled by a speed setpoint, and an operating mode, referred to as pursuit mode, in which the longitudinal speed of the vehicle is adjusted to maintain a safe distance from a target vehicle while remaining less than or equal to a speed setpoint. The method for programming a route planner for a motor vehicle according to the invention is then implemented when the route planner is in cruise mode and the speed setpoint changes and / or when the route planner is in pursuit mode.

[0018] In this embodiment, when the route planner is in cruise operating mode and the predicted distance j is greater than the safety distance dref during the second step of the process, the route planner switches to pursuit operating mode.

[0019] Advantageously, the method according to the invention further comprises a step positioned between the second step and the third step and implemented when the route planner is in pursuit mode, of adding a speed increment vpid to the target speed Vu so as to control the distance drel between the ego vehicle and the target vehicle on the safety distance dref.

[0020] According to one embodiment of the invention, the speed increment vpid is provided by a Proportional, Integral, Derivative controller, configured to control the relative distance error drel on the safety distance dref.

[0021] Advantageously, the time horizon TH depends on at least one parameter among the speed r of the vehicle ego, a difference between the speed v of the vehicle ego and the set speed and the type of road on which the vehicle travels.

[0022] Advantageously, the safety distance dref depends on at least one parameter among the speed r of the vehicle ego, the set speed vt of the target vehicle, and the type of road on which the vehicle travels.

[0023] The invention also relates to a motor vehicle comprising a route planner configured to generate a non-linear longitudinal speed profile from a target speed and a distance at which the target speed must be reached, the motor vehicle comprising computing means configured to implement the steps of a method for programming a route planner according to the invention.

[0024] Finally, the invention relates to a computer program product comprising program code instructions recorded on a computer-readable medium, to implement the steps of the process according to the invention when said computer program is executed on a computer.

[0025] Computer-readable recording medium on which is recorded a computer program comprising program code instructions for implementing the steps of the process according to the invention. Brief description of the drawings

[0026] The invention will be better understood and other features, details and advantages will become clearer from the following description, given by way of non-limiting reason, and from the accompanying figures, given by way of example.

[0027] [Fig.1] Fig.1 schematically describes the steps of the process according to the invention.

[0028] [Fig.2] Fig.2 illustrates the implementation of the method, in the case where the vehicle The target is sufficiently far from the ego vehicle.

[0029] [Fig.3] Fig.3 illustrates the implementation of the process, in the case where the target vehicle is close to the ego vehicle.

[0030] [Fig.4] Figure 4 illustrates the performance obtained by implementing the process according to the invention, in a particular application case when the trajectory planner is in pursuit mode

[0031] Identical references may be used in different figures when they refer to identical or comparable elements. Description of the implementation methods

[0032] In the following description, the following mathematical symbols will be used: - Th; duration of a predefined time horizon; - L; setpoint speed; - : target speed, used to generate the longitudinal speed profile linear; - do: target distance, used to generate the non-linear longitudinal velocity profile, and which corresponds to the distance at which the target velocity must be reached; - drel; current relative distance between the ego vehicle and the target vehicle; - j: prediction of the relative distance between the ego vehicle and the vehicle target at the end of the time horizon TH; - dxc; minimum desired relative distance between the ego vehicle and the target vehicle, or safety distance; - v: current speed of the vehicle ego; - vt: current speed of the target vehicle; - at: current acceleration of the target vehicle; - vt: prediction of the speed of the target vehicle at the end of the time horizon TH; - dt; distance between the ego vehicle and the target vehicle.

[0033] The method according to the invention is intended to be implemented on a vehicle comprising ADAS driver assistance devices providing it with information such as the vehicle's speed v, and information on surrounding vehicles, for example through a model of the vehicle's situation in its environment, such as a "world model". Such a model represents the current state of the vehicle's driving environment, including the position, speed, and acceleration of surrounding vehicles, pedestrians, road signs, etc. This model is established from information gathered by the various The vehicle's sensors are used by driver assistance systems to make real-time decisions, such as adapting speed, keeping in lane, overtaking, or emergency braking. The vehicle therefore has, in particular, the distance dre( to the vehicle in front of it (target vehicle), as well as the speed vt and acceleration at of the target vehicle.

[0034] The duration TH of the time horizon is predetermined. It can be fixed or depend on the conditions under which the vehicle is operating. For example, it can depend on the vehicle's speed v ego, the difference between the vehicle's speed ego and the set speed for the type of road on which the vehicle is traveling, etc. This value is typically in the range of 1 to 10 seconds.

[0035] The distance dsec corresponds to a safety distance to be maintained with the target vehicle. This distance is generally a function of the speed of the vehicle ego, current or target, but could equivalently be a function of another parameter, such as for example the set speed vc, the speed vt of the target vehicle, the type of road on which the vehicle is traveling, or be fixed.

[0036] The method according to the invention therefore relates to a method for programming a planner for a motor vehicle configured to generate a non-linear longitudinal speed profile, and for applying it to the vehicle. Such a non-linear profile aims to optimize the acceleration and jerk constraints, and for this purpose must be programmed with a target speed vo, and the distance at which this target speed must be reached (target distance d^).

[0037] Fig. 1 schematically describes the steps of the process according to the invention.

[0038] It includes a first step 101 of determining the target speed and the target distance do. In this first step, the target speed v» is set as equal to a setpoint speed vc imposed by the vehicle driver or by the on-board computer. The target distance d0 corresponds to the distance traveled by the vehicle while traveling at speed C over a predefined time horizon TH: dQ - V(*TH.

[0039] This step provides a first approximation of the target speed and distance do, valid in cruise mode when there are no vehicles in front of vehicle ego. However, this first approximation does not take into account the presence of vehicles in front of vehicle ego, which could end up at a distance less than the safe following distance dæc at the end of the time horizon TH. Therefore, the method according to the invention includes a second step 102, implemented when a vehicle is in front of vehicle ego. This second step comprises calculating a predicted distance j between vehicle ego and the target vehicle at the end of the time horizon TH, as illustrated in Figures 2 and 3.

[0040] These figures schematically represent the ego vehicle 201 and the target vehicle 202 at the moment when the method according to the invention is implemented. They also represent, in dotted lines, the positions of the ego vehicle 203 and the target vehicle 204 predicted at the end of the time horizon TH.

[0041] Predicting the position of the vehicle ego is simple since, considering that the initial position of the vehicle ego is the position xo, the predicted position of the vehicle ego is *o + ^o-

[0042] The predicted position xt of the target vehicle at the end of the time horizon TH is calculated assuming its acceleration is constant. It can thus be obtained using the formula v — v + d a- v'J T^r'

[0043] These two positions allow the calculation of a predicted relative distance j between the ego vehicle and the target vehicle at the end of the time horizon TH, with drei = xt-(xQ + d^

[0044] If the relative distance $ is greater than the safety distance dsec, as is the case in Figure 2, the method according to the invention implements a third step 103 of programming the route planner using the target speed v° as the speed setpoint and the target distance rfo as the distance at which said target speed must be reached.

[0045] If the relative distance ; is greater than the safety distance d^, as is the case in [Fig. 3], then the vehicle ego will be too close to the target vehicle at the end of the time horizon. The method according to the invention then adjusts the speed and distance commands as follows: • the target speed is equal to the predicted speed vt of the target vehicle at the end of the time horizon, considering its speed as constant, i.e. L> = ^ + atTH; • The target distance dQ is equal to the target distance d0 calculated in the first step 101 of the process according to the invention, less the difference between the predicted relative distance and the safety distance d^c, i.e. do do "F $rel " ^sec

[0046] In addition, if the ego vehicle's trajectory planner was in cruise mode, it switches to pursuit mode.

[0047] Finally, the method according to the invention implements the third step 103 of programming the route planner using the target speed as the speed setpoint and the target distance rfo as the distance at which said target speed must be reached.

[0048] In this way, at the end of the time horizon, the speed of the ego vehicle is equal to the speed of the target vehicle, and the distance between the ego vehicle and the target vehicle corresponds to the required safety distance, which is the situation sought for a trajectory planner operating in pursuit mode.

[0049] In summary, the method for programming a route planner for a motor vehicle according to the invention defines a time horizon and projects itself onto the situation at the end of this time horizon to determine the speed and distance to be applied as input commands for the route planner. It thus allows the use, for the cruise and pursuit modes, of the same nonlinear speed profile generator as for the contextual mode of the trajectory planner. However, the calculations presented above approximate that the vehicle ego moves at the set speed L during the time horizon TH, which is not the case. This approximation is necessary because the speed profile is unknown when the method is implemented.

[0050] Thus, when the vehicle is in pursuit mode, at the end of the time horizon Th, the ego vehicle and the target vehicle are indeed at the same speed, but the two vehicles are separated by a gap drel equal to dsec+ A, A being a residual related to the approximations made during the calculations.

[0051] The method according to the invention may then include an optional step 104 positioned between steps 102 and 103 when the route planner is in tracking mode, for adding a speed increment vpid to the speed in order to minimize the deviation A. The vpid increment can be calculated by a PID controller (acronym for Proportional, Integral, Derivative) configured to control the relative distance error drei on the safety distance. A PID controller is a control system that improves the performance of a closed-loop system or process. Such controllers are well known to those skilled in the art.

[0052] The method of programming a route planner for a motor vehicle according to the invention makes it possible to generate a non-linear longitudinal speed profile when the route planner is in cruise mode and a change in speed setpoint is requested (either by the driver or by the on-board computer), or continuously when the route planner is in pursuit mode.

[0053] Figure 4 illustrates the performance obtained by implementing the method according to the invention, in a particular application case where the trajectory planner is in pursuit mode.

[0054] Graph 410 represents the evolution over time of the speed of a target vehicle 411 (bold solid line), an ego vehicle 412 equipped with a state-of-the-art trajectory planner (dashed line), and an ego vehicle 413 equipped with a trajectory planner configured to generate a non-linear longitudinal velocity profile and implementing the method according to the invention in fine continuous line.

[0055] It is observed that the ego vehicle and the target vehicle are both traveling at the same speed, then the target vehicle suddenly reduces its speed by 5 m / s. Curves 412 and 413 show that the speed of the ego vehicle adjusts accordingly, with or without implementation of the invention. However, curve 413 shows that implementing the invention results in a more gradual decrease in speed.

[0056] Graph 420 represents the deviation from the safe distance d^c between the target vehicle and the ego vehicle. Curve 421 shows the performance for a prior art trajectory planner, and curve 422 shows the performance when implementing the method according to the invention. In both cases, the error from the safe distance converges to zero, which means that the method according to the invention does indeed generate a speed profile that cancels the relative speed and relative distance errors. It can be seen that implementing the invention results in a longer convergence time than without implementing the invention.

[0057] Graphs 430 and 440 respectively represent acceleration and jerk without implementing the invention (curves 431 and 441) and with implementing the invention (curves 432 and 442). It can be seen that implementing the invention makes it possible to control the acceleration and jerk of the speed profile, which was not the case without implementing the invention. This results in a greater sense of comfort for the passengers.

[0058] In practice, the acceleration and jerk peaks observed in Figures 430 and 440 can exceed the kinematic limits of the ACC, and the trajectory planner must then compensate by limiting the vehicle's acceleration and jerk, which reduces its speed and therefore its ability to reject disturbances. This is no longer the case when the method according to the invention is implemented, since the system's kinematic limits in acceleration and jerk are respected.

[0059] The invention relates to a method of programming a route planner, but also to a computer program comprising program code instructions recorded on a computer-readable recording medium enabling it to execute the steps of the described method, as well as to the recording medium itself.

[0060] It also relates to a motor vehicle, of whatever type (car, truck, motorcycle, etc.), comprising a route planner configured to generate a non-linear longitudinal speed profile from a target speed and a distance at which the target speed must be reached, and comprising computing means, for example a microprocessor, a computer, or any equivalent means, configured to perform at least steps 101 to 103 of the method of The programming described above is used to generate a non-linear velocity profile for controlling the vehicle's longitudinal speed. The computational resources can be shared with other algorithmic blocks implemented on the vehicle, such as the route planner.

Claims

Demands

1. Method of programming a route planner for a motor vehicle, said vehicle ego, said route planner being configured to generate a nonlinear longitudinal speed profile from a target speed and a distance at which said target speed must be reached, the method being characterized in that it comprises: - a step (101) of determining a target speed v' equal to a setpoint speed vc, and of determining a target distance at which the vehicle ego must reach the target speed from the target speed vo and a predefined time horizon TH;- a step (102) implemented when a vehicle, called the target vehicle, is in front of the ego vehicle, of calculating a predicted distance between the ego vehicle and the target vehicle at the end of the time horizon Tfh and when the predicted distance j is greater than a safety distance dref, of using a predicted speed vt of the target vehicle at the end of the time horizon TH as the target speed \ and of adding the predicted distance less the safety distance drej to the target distance do; - a step (103) of programming the route planner using the target speed as the speed setpoint and the target distance rfa as the distance at which said target speed must be reached.

2. A method for programming a route planner according to claim 1, wherein the nonlinear longitudinal velocity profile is generated so as to optimize the acceleration and jerk of the ego vehicle.

3. A method for programming a route planner according to any one of claims 1 and 2, wherein the route planner comprises at least one operating mode called cruise in which the longitudinal speed of the vehicle is controlled by a speed setpoint, and an operating mode called pursuit in which the longitudinal speed of the vehicle is adjusted to maintain a safe distance from a vehicle target while being less than or equal to a speed setpoint, the process of programming a trip planner for motor vehicle being implemented when the trip planner is in cruise mode and the speed setpoint changes and / or when the trip planner is in pursuit mode.

4. Method of programming a route planner according to claim 3, in which, when the route planner is in cruise operating mode and the predicted distance j is greater than the safety distance dref during the second step (102) of the method, the route planner switches to pursuit operating mode.

5. A method for programming a route planner according to any one of claims 3 to 4, further comprising a step (104), positioned between the second step (102) and the third step (103) and implemented when the route planner is in pursuit mode, of adding a speed increment vpid to the target speed so as to control the distance drej between the ego vehicle and the target vehicle on the safety distance dref

6. A method for programming a route planner according to claim 5, wherein the speed increment vpid is provided by a Proportional, Integral, Derivative controller configured to control the relative distance error dre! on the safety distance dref

7. A method for programming a route planner according to any one of the preceding claims, wherein the time horizon TH depends on at least one parameter among the speed v of the vehicle ego, a difference between the speed r of the vehicle ego and the set speed \ and the type of road on which the vehicle travels.

8. A method for programming a route planner according to any one of the preceding claims, wherein the safety distance drej depends on at least one parameter among the speed v of the vehicle ego, the set speed vt of the target vehicle, and the type of road on which the vehicle is traveling.

9. A motor vehicle comprising a route planner configured to generate a nonlinear longitudinal speed profile from a target speed and a distance at which said target speed is to be reached, characterized in that the motor vehicle comprises computing means configured to implement the steps of a method for programming a route planner according to any one of claims 1 to 8.

10. Product computer program comprising program code instructions recorded on a computer-readable medium, to carry out the steps of the process according to any one of claims 1 to 8 when said computer program is executed on a computer.

11. A computer-readable recording medium on which is recorded a computer program comprising program code instructions for carrying out the steps of the process according to any one of claims 1 to 8.