METHOD FOR DETERMINING WHEN THE LONGITUDINAL SPEED CONTROL OF A MOTOR VEHICLE SHOULD BE ACTIVATED

Description

[0001] The present invention claims priority from French application 2201083 filed on 08.02.2022.

[0002] The present invention relates generally to the automotive field, and in particular to the field of driving assistance processes and systems also referred to as ADAS systems (Anglo-Saxon acronym for "Advanced Driver-Assistance System").

[0003] It relates more specifically to a method for determining the moment of activation of the longitudinal speed regulation of a motor vehicle following the detection of a speed limit zone, on the route of said vehicle, in front of the vehicle.

[0004] The vehicle is also referred to as the "host" vehicle, "ego vehicle", or simply "ego".

[0005] Adaptive cruise control (ACC) systems are known for continuously controlling the speed of the host vehicle according to a longitudinal control law. This law adjusts the host vehicle's speed based on a speed set by the driver and the presence of a vehicle ahead in the same lane, referred to as the target vehicle. This longitudinal control law can be used in various scenarios. For example, a host vehicle equipped with such a system can automatically adjust its speed to maintain a predetermined safe distance from the target vehicle. As soon as the lane is clear ahead, the host vehicle's acceleration automatically increases to reach the driver's selected speed, thus assisting the driver in their driving task.

[0006] Systems are also known that can predict the necessary speed adjustment to adapt the vehicle's speed based on speed limit information detected several kilometers ahead. These systems are designated by the acronym A-ISA (Anticipated Intelligent Speed ​​Adaptation) and utilize the vehicle's speed limiter and / or adaptive cruise control (ACC) using mapping data provided by a system known as an "e-horizon" or "electronic horizon," which allows the driver to extend their field of vision beyond what is immediately visible. The range of such a system is approximately 2 km.

[0007] DE102014215673 is known to be a driver assistance system in a motor vehicle. EP2712781 is known to be a vehicle speed control device.

[0008] Thus, upon detecting an upcoming speed limit zone, the A-ISA system informs the driver of this speed limit (offering an acknowledgment option) and then asks them to confirm (acknowledge) the new speed within a specified timeframe for it to be effectively applied by the vehicle's cruise control. This occurs well before the vehicle reaches the speed limit sign. The aim is to ensure the vehicle is at the correct speed when it approaches the speed limit sign.

[0009] Today, the point at which the driver is prompted to acknowledge the new speed information provided by the A-ISA system, and from which point the driver must acknowledge the new target speed, is determined empirically from driving tests and the following equation: T _ Proposition = Delta V a + b ∗ 1 − Delta V 2 ∗ V ego init + T _ confort _ A _ ISA

[0010] With : Delta V : difference between the "ego" speed and the speed of the sign V egoinit : “ego” speed a and b: constants determined from the tests.

[0011] T_confort_A_ISA: estimated time during which the driver must adjust the set speed to reach the speed limit indicated by the sign when the vehicle (ego) approaches the sign without sudden deceleration. This time is estimated at 5 seconds. Thus, if the driver adjusts the new set speed after 5 seconds, the vehicle will only reach the speed indicated by the sign after passing it. Furthermore, the vehicle's speed regulation control may, in order to reduce the vehicle's longitudinal speed, impose decelerations and jerks that are strongly perceived by the driver and other passengers during the journey, causing discomfort for the latter. It should be noted that a jerk is the derivative of acceleration (or deceleration), also commonly referred to as a "jerking" or "shock."

[0012] The present invention aims to overcome these drawbacks by proposing a solution to calculate the optimal time to start longitudinal speed regulation with a "comfortable" (smooth) deceleration throughout the journey up to the speed limit sign and potentially to automatically activate the A-ISA function on a specific type of journey that allows it, such as on a motorway.

[0013] To this end, the present invention has as its first object a method for determining the activation time of the longitudinal speed regulation of a motor vehicle, following the detection of the beginning of a speed limit zone located at a determined position in front of the vehicle, on the trajectory of said vehicle, said method consisting of determining the position of the beginning of this zone relative to the vehicle and the speed limit information of said zone and if the difference in speed between the current speed of the vehicle (ego) and the speed limit information is greater than a determined threshold, of constructing several deceleration profiles for different times of acknowledgment of the speed limit between a proposed acknowledgment time and a determined maximum acknowledgment time, bringing the speed of the vehicle to that of the speed limit by taking into account the longitudinal position, the longitudinal speed,the longitudinal acceleration and longitudinal jerk of the vehicle, to identify and retain from these profiles a specific deceleration profile meeting specific comfort constraints, with the shortest deceleration time, and from the selected profile, to determine the distance separating the vehicle positions between the beginning and end of said time, and to activate the vehicle's longitudinal speed control when the vehicle reaches said distance from the beginning of the speed limit zone.

[0014] According to the present invention, the comfort constraints are based on a determined deceleration value between determined minimum and maximum permissible values ​​and on a determined jerk value between determined minimum and maximum permissible values; the determined deceleration and jerk values ​​being considered over a determined maximum duration between the time of proposal of acknowledgment and the maximum time of acknowledgment.

[0015] According to the present invention, the method consists of considering a linear relationship between the maximum and minimum deceleration values ​​and the acknowledgment time after the acknowledgment proposal time and a linear relationship between the maximum and minimum Jerk values ​​and the maximum acknowledgment time determined after the acknowledgment proposal time.

[0016] According to another characteristic, the linear relationship between the maximum and minimum deceleration values ​​and the time of acknowledgment after the time of acknowledgment proposal is expressed by the following equation: D é c é l é ration maximale admissible = − 1 5 ∗ t − 1 2 The linear relationship between the maximum and minimum Jerk values ​​and the time of acknowledgment after the time of acknowledgment proposal is expressed by the following equation: Jerk maximal admissible = − 0,2 5 ∗ t − 0,6 .

[0017] According to another characteristic, a moment of acquittal after the proposal of acquittal to t = 0 , allowing the construction of deceleration profiles that meet comfort constraints, is chosen at t = 3,5 secondes.

[0018] According to another characteristic, deceleration profiles are constructed from kinematic equations of vehicle motion: Longitudinal position P(t) of the vehicle expressed in the form of a 5th-order polynomial: P ( t ) = C 5 * t 5< + C 4 * t 5< + C 3 * t 3< + C 2 * t 2< + C 1 * t + C 0 ; longitudinal velocity V ( t ) expressed as the derivative of the longitudinal position with respect to time P(t) : V(t) = 5 * C 5 * t 4< + 4 * C 4 * t 3< + 3 * C 3 * t 2< + 2 * C 2 * t + C 1 ; longitudinal acceleration A(t) expressed as the derivative of velocity with respect to time V ( t ) : A ( t ) = 20 * C 5 * t 3< + 12 * C 4 * t 2< + 9 * C 3 * t + 2 * C 2 ; the Jerk J ( t ) expressed as the derivative of the acceleration with respect to time A ( t ) : J ( t ) = 60 * C 5 * t 2< + 24 * C 4 * t + 6 * C 3 and in which C 0 , C 1 , C 2 , C 3 , C 4 , C 5 are coefficients determined from constraints defined at the beginning and end of the durations of the deceleration profiles.

[0019] According to another feature, the process consists of automatically acknowledging the regulation command when the type of traffic lane chosen allows it.

[0020] The present invention has as its second object a computer program product comprising instructions which, when the program is executed by a computer, lead the computer to implement the steps of the process as described above.

[0021] The present invention has as its third object, a motor vehicle comprising an adaptive cruise control implementing the method as described above.

[0022] According to one characteristic, the vehicle also includes a means of disseminating information capable of informing the driver of the vehicle that the longitudinal speed regulation of the vehicle is activated.

[0023] The present invention has the advantage of no longer relying on an empirical method to determine the activation time of the vehicle's longitudinal speed control and, furthermore, of determining this time to ensure smooth (jerky) deceleration. It also has the advantage of automatically triggering the activation of the control system when the type of road conditions permits.

[0024] Other advantages and features will become clearer from the following description, given solely as a non-limiting example and with reference to the drawings in which: [ Fig. 1 ] illustrates a flowchart of the main steps of the process according to the invention; [ Fig. 2 ] illustrates a graphical representation of the maximum permissible deceleration taken into account by the method according to the invention; [ Fig. 3 ] illustrates a graphical representation of the maximum permissible jerk taken into account by the method according to the invention; [ Fig. 4 ] illustrates a graphical representation of a first scenario for constructing a deceleration profile obtained by the method according to the invention; and [ Fig. 5 ] illustrates a graphical representation of a second scenario for constructing a deceleration profile obtained by the method according to the invention.

[0025] The method according to the invention implements an A-ISA type control function. This function is capable of anticipating speed limits displayed on speed limit signs located along the vehicle's route, in front of the vehicle. The A-ISA function uses map data provided by an e-horizon system to propose a new target speed to the driver, corresponding to the speed limit detected by the e-horizon system based on the sign's position. This target speed is then sent to the vehicle's cruise control, which applies a specific control law to gradually bring the vehicle's speed to the target speed well before the vehicle reaches the speed limit sign. The vehicle is therefore already traveling at the target speed when it approaches the sign.

[0026] We are considering here a speed limit sign, but we can equally consider a speed limit zone or even speed limit information provided by the road infrastructure and / or by another vehicle via vehicle-to-vehicle communication and / or communication between vehicles and the infrastructure. The main steps of the method according to the invention are described below with reference to the flowchart of the figure 1 After a sign detection step 100, the process involves filtering the data provided by the e-horizon 100 system (data that is provided to the vehicle when it is approximately 2 km from the sign). Not all speed limit signs are taken into account for use by the A-ISA function.

[0027] To achieve this, the method according to the invention first involves determining (step 200) the position of the sign relative to the vehicle and the speed limit information displayed on the sign. Speed ​​limit signs are then classified (step 300) as relevant or irrelevant as follows. When a speed limit sign is detected 2 km from the vehicle, the speed limit displayed on the sign is identified by the e-horizon system. If the difference in speed between the vehicle's current speed (ego) and the speed limit indicated on the sign (set speed) exceeds a predetermined threshold (based on the vehicle's current speed and the calculation time), then the speed limit is applied and becomes the new set speed for the vehicle's cruise control.

[0028] Otherwise, the process considers that the speed difference is not large enough to activate the A-ISA longitudinal speed control function (or A-ISA control).

[0029] When a speed limit sign is classified as relevant, it is still quite far away (approximately 2 km from the vehicle), and therefore the driver cannot be prompted to accept the new speed limit (the new target speed for the cruise control) as soon as the sign is detected. The concept of a "good" time to prompt the driver to accept the new target speed is then introduced. This "good" time allows the cruise control to reduce the vehicle's speed to the limit displayed on the speed limit sign by the time the vehicle reaches the sign, while also respecting certain comfort constraints.

[0030] If the sign is determined to be relevant by the process, and the vehicle is traveling for example at 100 km / h and the speed limit displayed on the sign is 70 km / h (new target speed), the process must command the vehicle to decelerate to go from a vehicle speed of 100 km / h to a vehicle speed of 70 km / h.

[0031] To do this, the process consists of constructing, (step 400), deceleration profiles for different acknowledgment times between t = 0 s (acknowledgment proposal time) and t = 5 s (maximum acknowledgment time) from the longitudinal speed of the vehicle Vego, the longitudinal acceleration of the vehicle (or deceleration which is the negative acceleration), the longitudinal position of the vehicle and the longitudinal jerk, at the time of the acknowledgment proposal t = 0 s.

[0032] The method according to the invention then consists of identifying and selecting (step 500), from among all the longitudinal deceleration profiles, the one offering the most comfortable deceleration according to predetermined criteria or constraints, specified below, and with the shortest deceleration time Dm. The method then consists, based on the selected deceleration profile, of determining (step 600) the vehicle's position at the end of the deceleration profile (end of the duration Dm). The difference in the vehicle's position between the beginning and the end of the duration Dm will then provide the distance in meters to be considered, starting from the sign, to determine the moment from which the method will command (step 700) the activation of the vehicle's longitudinal speed control until it reaches the sign. The method can be implemented automatically if the road type is suitable. This may be the case, for example, on a highway.Thus, if the selected road type is a motorway and the cruise control mode is chosen, for example, an A-ISA cruise control mode, then the system is automatically activated upon detection of a speed limit sign. In this automatic mode, and to avoid surprising the driver who might initially perceive a deceleration without any apparent cause, the system commands the dissemination of information from the start of the maneuver via the vehicle's information dissemination system, capable of informing the driver that cruise control is activated.

[0033] The comfort constraints used by the process according to the invention to retain the desired deceleration profile are defined below.

[0034] A first comfort constraint retained by the process according to the invention is defined based on a linear relationship between the maximum permissible deceleration / minimum permissible deceleration and the time of acknowledgment t = 5 s after the acknowledgment proposal t = 0 s. The maximum permissible deceleration is expressed by the following equation: D é c é l é ration maximale admissible = − 1 5 ∗ t − 1 2

[0035] This linear relationship between deceleration, expressed in m / s², and the acknowledgment time, expressed in seconds (s), is represented graphically on the figure 2 .

[0036] A second comfort constraint retained by the process according to the invention is defined based on a linear relationship between the maximum permissible jerk / minimum permissible jerk and the time of acknowledgment t = 5 s after the acknowledgment proposal t = 0 s. The maximum permissible jerk is expressed by the following equation: Jerk maximal admissible = − 0,2 5 ∗ t − 0,6

[0037] This linear relationship between the jerk, expressed in m / s, and the acknowledgment time, expressed in seconds (s), is graphically represented on the figure 3 .

[0038] Deceleration profiles are constructed from the kinematic equations of motion of the vehicle.

[0039] By exploiting these values ​​directly in the construction of Jerk profiles, we then free ourselves from the dependence between the time of acknowledgment and the notions of maximum permissible deceleration and maximum permissible Jerk.

[0040] To meet certain requirements, particularly in terms of computation time, and to optimize comfort, the process advantageously considers an acknowledgment time of t = 3.5 s. From this value, the process calculates the most comfortable maximum permissible deceleration and maximum permissible jerk using the preceding equations: D é c é l é ration max admissible la plus confortable = − 1 5 ∗ 3 , 5 − 1 2 = − 1 , 2 m / s 2 Jerk max admissible le plus confortable = − 0,2 5 ∗ 3,5 − 0,6 = − 0,74 m / s 3

[0041] The equation used to express the longitudinal position P(t) the vehicle's function can be written in the form of a 5th order polynomial: P t = C 5 ∗ t 5 + C 4 ∗ t 5 + C 3 ∗ t 3 + C 2 ∗ t 2 + C 1 ∗ t + C 0

[0042] And by the derivative of the position P(t) in relation to time V(t), We obtain the equation for the longitudinal velocity: V t = 5 ∗ C 5 ∗ t 4 + 4 ∗ C 4 ∗ t 3 + 3 ∗ C 3 ∗ t 2 + 2 ∗ C 2 ∗ t + C 1

[0043] We derive the speed V(t) with respect to time to obtain the equation for longitudinal acceleration A ( t ) : A t = 20 ∗ C 5 ∗ t 3 + 12 ∗ C 4 ∗ t 2 + 9 ∗ C 3 ∗ t + 2 ∗ C 2

[0044] And finally, we derive the acceleration equation A(t) compared to the time required to obtain the longitudinal jerk equation J ( t ) : J t = 60 ∗ C 5 ∗ t 2 + 24 ∗ C 4 ∗ t + 6 ∗ C 3

[0045] The coefficients C 5 , C 4 , C 3 , C 2 , C 1 , C 0 are determined according to constraints defined at t=0 and at t= end of maneuver.

[0046] They are calculated using the following equations: C 0 = 0 C 1 = V init = Vitesse initiale à t = 0 C 2 = A init 2 avec A init : Acc é l é ration initiale à t = 0 C 3 = J init 6 avec J init : Jerk initiale à t = 0 C 4 = V consigne − V init − A consigne − A init 4 ∗ D m − J init 4 ∗ D m 2 − A init ∗ D m D m 3 avec V consigne = vitesse limitée C 5 = − 3 ∗ V consigne − V init + A consigne − A init ∗ D m + J init 2 ∗ D m 2 + 3 ∗ A init ∗ D m 5 ∗ D m 4 with D m = duration of the maneuver between t = 0 and t = end of maneuver.

[0047] The preceding equations are implemented from a program made, for example, with MATLAB ™< .

[0048] MATLAB™, an acronym for "matrix laboratory," is a programming language emulated by an environment of the same name; it is used for numerical computation. Developed by MathWorks, MATLAB™ allows users to manipulate matrices, display curves and data, implement algorithms, create user interfaces, and interface with other languages ​​such as C, C++, Java, and Fortran.

[0049] The script for this program is given below as an example:

[0050] In the script above, the program tries several maneuver durations. D m and checks if the different declaration profiles comply with the maximum permissible deceleration / jerk constraints. The program keeps the shortest duration D m during which deceleration can be carried out with the constraints already explained.

[0051] There figure 4 graphically illustrates a first scenario of the selected deceleration profile with the duration D m the shortest, constructed with the following data: the vehicle is traveling at a speed of 100 km / h ( V init ) and a speed limit sign of 70 km / h (V consigne ) is detected 2 km ahead of him.

[0052] The upper curve represents the vehicle's speed (V) expressed in km / h as a function of time t, expressed in seconds (s), and the lower curve represents the vehicle's position (P) expressed in meters (m) as a function of time t, expressed in seconds (s), for the same duration. D m .

[0053] From the upper curve, we observe that to go from a speed of 100 km / h to a speed of 70 km / h, a time is required D m of 8 s. By transferring this duration to the lower curve, we graphically obtain the position of the vehicle at the end of the deceleration (maneuver), i.e. 198.02 m.

[0054] We therefore know that to go from 100 km / h to 70 km / h, a distance of 198.02 m will be required (with a maximum permissible deceleration < 1.2 and a maximum permissible jerk < 0.74)

[0055] This distance, measured to the height of the speed limit sign, determines the acknowledgment time and therefore the activation time of the A-ISA longitudinal speed control system. Thus, when the vehicle reaches 198.02 m from the speed limit sign, the A-ISA system will be activated and the vehicle will approach the speed limit sign at the correct speed (70 km / h).

[0056] There figure 5 graphically illustrates a second selected deceleration profile scenario with the duration D m The shortest route, using the same type of curves but with the following data: the vehicle is traveling at a speed of 120 km / h ( V init ) and a speed limit sign of 80 km / h ( V consigne ) is detected 2 km ahead of him.

[0057] From the upper curve, we observe that it takes 10 seconds to go from a speed of 120 km / h to a speed of 80 km / h. By plotting this time on the lower curve, we graphically obtain the vehicle's position at the end of the deceleration, which is 325.35 m.

[0058] We therefore know that to perform this deceleration profile between 120 km / h and 80 km / h, a distance of 325.35 m will be required (with a maximum permissible deceleration < 1.2 and a maximum permissible jerk < 0.74)

[0059] Thus, when the vehicle arrives at 325.35 m from the speed limit sign, the A-ISA regulation will be activated and the vehicle will arrive at the speed limit sign at the correct speed (80 km / h).

[0060] The process implements a computer program product containing instructions for executing the steps of the process described above.

[0061] This program is implemented for example by one or more computers (or processors) of the ADAS system (ADAS supervisor) of the vehicle in connection with one or more computers (or processors) of the IVI (In-Vehicle Infotainment) system which is the central organ of the vehicle dedicated to data processing and communication with the driver.

[0062] Such a program can be updated with the possibility of adding functions using an OTA (Over The Air) type update.

Claims

1. A method for determining the moment of activation of the longitudinal speed control of a motor vehicle, following the detection (100) of a speed limitation zone beginning at a determined position in front of the motor vehicle, on the trajectory of said motor vehicle, said method comprising determining (200) the position of the beginning of said zone by report to the motor vehicle and the speed limitation information of said threshold and if the speed difference between the current speed of the motor vehicle and the speed limitation information is greater than a determined profile (300), to be constructed (400) several positions deceleration zones for different instants of acknowledgement of the speed limit between a proposed acknowledgement instant (t = 0) and a determined maximum acknowledgement instant, bringing the speed of the vehicle to that of the speed limit by taking into account the longitudinal in, the longitudinal speed, the longitudinal acceleration and the longitudinal Jerk of the vehicle, to identify and retain (500) these profiles, a determined deceleration profile corresponding to determined comfort constraints, with the shortest deceleration time (Dm), and from the profile retained, to determine (600) the distance separating the positions of the vehicle between the beginning and the end of said period, and ordering (700) the activation of the longitudinal speed control of the vehicle when the vehicle arrives at said distance from the beginning of the speed limitation zone, method in which the comfort constraints are based on a determined deceleration value between determined minimum and maximum permissible values and on a determined Jerk value between determined minimum and maximum permissible values; the determined deceleration and jerk values being considered over a determined maximum period between the proposed acknowledgement time and the maximum acknowledgement time, that method consisting in considering a linear relationship between the maximum and minimum deceleration values and the acknowledgement instant after the acknowledgement proposal instant and a linear relationship between the maximum and minimum Jerk values and the maximum acknowledgement instant determined after the acknowledgement proposal instant.

2. Method according to the previous claim, wherein the linear relationship between the maximum and minimum deceleration values and the acknowledgement time after the acknowledgement suggestion time is expressed by the following equation: Maximum permissible deceleration =-1 / 5*t-1 / 2 , the linear relationship between the maximum and minimum Jerk values and the acknowledgement time after the acknowledgement suggestion time is expressed by the following equation: Maximum permissible Jerk =-(0,2) / 5*t-0,6 .

3. Method according to the previous claim, wherein an acknowledgement instant after the acknowledgement suggestion at t=0, making it possible to construct the deceleration profiles filling the comfort constraints, is chosen at t=3.5 seconds.

4. Method according to one of the previous claims, in which the deceleration profiles are constructed from kinematic equations of vehicle motion: the longitudinal position P(t) of the vehicle expressed as a polynomial of the 5th order: P(t) = C5 * t5 + C4 * t5 + C3 * t2 + C2 * t2+ C1 * t + C0 ; the longitudinal speed V(t) expressed as the derivative of the longitudinal position by report at time P(t): V(t) = 5 * C5 * t4 + 4 * C4 * t3 + 3 * C3 * t2 + 2 * C2 * t + C1 ; the longitudinal acceleration A(t) is the derivative of the report speed at time V(t): A(t) = 20 * C5 * t3 + 12 * C4 * t2 + 9 * C3 * t + 2 * C2 ; the Jerk J(t) is the derivative of the report acceleration at time A(t): J(t) = 60 * C5 * t2 + 24 * C4 * t + 6 * C3 and in which C0, C1, C2, C3, C4, C5 are coefficients determined from constraints defined at the beginning and at the end of the durations of deceleration profiles.

5. Method according to one of the previous claims, consisting in automatically paying the regulating order when the type of taxiway chosen so permits.

6. Computer plan product comprising instructions which, when the plan is executed by a computer, lead the latter to implement the steps of the method according to one of claims 1 to 5.

7. Motor vehicle comprising an adaptive cruise control; implementing the method according to any one of claims 1 to 5.

8. A vehicle according to the previous claim, further comprising an information diffusion means adapted to inform the driver of the vehicle that the regulation of the longitudinal speed of the vehicle is activated.