METHOD AND DEVICE FOR CONTROLLING THE SPEED OF AN AUTONOMOUS VEHICLE

Description

[0001] The invention is in the field of autonomous vehicle driving assistance systems. In particular, the invention relates to a method and method of controlling the speed of an autonomous vehicle, referred to as the ego vehicle, when approaching a target vehicle, said ego vehicle being equipped with adaptive cruise control.

[0002] The term "vehicle" refers to any type of vehicle, such as a car, moped, motorcycle, warehouse robot, etc. "Autonomous driving" of an "autonomous vehicle" refers to any process capable of assisting the driving of the vehicle. This process may consist of partially or fully controlling the vehicle or providing any type of assistance to a person driving the vehicle. The process thus covers all autonomous driving, from level 0 to level 5 in the OICA (International Organization of Motor Vehicle Manufacturers) scale.

[0003] The methods capable of assisting the driving of the vehicle are also called ADAS (from the English acronym "Advanced Driver Assistance Systems"), ADAS systems or driver assistance systems.

[0004] Adaptive cruise control, or ACC, is a well-known ADAS system. An EG vehicle's ACC is capable of detecting a vehicle, called the target vehicle, that is traveling in front of the EG vehicle. The target vehicle is traveling in the same lane as the EG vehicle.

[0005] Adaptive Cruise Control (ACC) can regulate the speed of the ego vehicle based on its measured speed, a measured speed of the target vehicle, a measured distance between vehicles, and a predetermined time between vehicles. The distance between vehicles is the distance between the rear of the target vehicle and the front of the ego vehicle. Using the ego vehicle's speed, a time between vehicles is determined from the distance between vehicles, and vice versa. For example, the time between vehicles can be a parameter predetermined by the driver or set by default according to current regulations (e.g., 2 seconds).

[0006] When the cruise control speed is changed to reach, for example, a set speed, several vehicle speed trajectories (the evolution of vehicle speed over time) are possible. Following a vehicle speed trajectory determines the vehicle's acceleration, and therefore its dynamic behavior. Some cruise control systems are configured to determine a potential acceleration, an average acceleration that the ego vehicle must have to reach the target vehicle's speed within a predetermined time while maintaining the predetermined inter-vehicle time. If the vehicle needs to brake, for example, to reduce speed and / or reach the predetermined inter-vehicle distance, the potential acceleration is negative.

[0007] The ego vehicle is said to be approaching a target vehicle when the ACC detects a new target vehicle, for example, when the ACC is activated and a target vehicle is present at a distance less than the predetermined distance, when a vehicle cuts into the lane in which the ego vehicle is traveling and is in front of the ego vehicle at a distance less than the predetermined distance, or when the ego vehicle is overtaking a target vehicle traveling at a lower speed than the ego vehicle. The ACC must then regulate the vehicle's speed according to the predetermined time between vehicles. A potential acceleration is then determined by the ACC.This potential acceleration is higher (in absolute value) when the inter-vehicle distance is less than the predetermined inter-vehicle distance and when the target vehicle's speed is lower than the ego vehicle's speed. High potential acceleration then generates dynamic discomfort: a strong deceleration that is poorly perceived by the passengers of the ego vehicle. However, this strong deceleration, although excessive, reassures (psychologically) the passengers of the ego vehicle by confirming that the ACC has correctly detected the target vehicle. Furthermore, the inter-vehicle distance will quickly approach the predetermined inter-vehicle distance, thus creating a feeling of security.

[0008] We know from US2016 / 236685 a device and a method of control so that a vehicle follows a preceding vehicle.

[0009] One object of the present invention is to remedy the aforementioned problem, in particular to ensure a good compromise between dynamic / psychological comfort and sufficient safety.

[0010] To this end, a first aspect of the invention relates to a method for controlling the speed of an autonomous vehicle, referred to as the ego vehicle, approaching a target vehicle, said ego vehicle comprising an adaptive speed regulator, said regulator determining a potential acceleration, A pot (t), at one moment tGiven, said potential acceleration being based on a measurement of the speed of the ego vehicle, on a measurement of an inter-vehicle distance and on a predetermined inter-vehicle distance, referred to as the predetermined distance, and / or on a predetermined inter-vehicle time, referred to as the predetermined time, said potential acceleration being negative and corresponding to a change in speed over a predetermined time theoretically applied to said ego vehicle so that said ego vehicle meets a criterion based on said predetermined distance and / or on said predetermined time, said controller controlling said speed of said ego vehicle based on said potential acceleration, said method comprising the steps of: Acquisition of said potential acceleration, A pot (t) Acquisition of instantaneous acceleration, at a given instant t given, of said vehicle ego, A égo (t) Determining a jerk, J Min (t), representing a variation in acceleration, based on said potential acceleration, on said instantaneous acceleration and a strictly negative predetermined initial jerk, j0, said jerk being less than or equal to the initial jerk, and said jerk being more negative the more negative the potential acceleration is; Determination of a corrected potential acceleration, A cor (t), based on said jerk, said jerk limiting the variation of potential acceleration; Regulation of said vehicle speed by said adaptive cruise control based on said corrected potential acceleration. said jerk, J min (t), is determined by the formula J min (t)= k1*(A pot (t)+max(0, A égo (t))) 2< +j0 Or k1 is a negative preset adjustment parameter, max(.) being the maximum function.

[0011] Thus, the deceleration of said ego vehicle will be limited by said cruise control, which is now based on said corrected potential acceleration. This corrected potential acceleration is limited by said jerk. The vehicle's deceleration will no longer be as strong in the initial moments of approach as it would be if said cruise control remained based on potential acceleration. This implies that said criterion based on said predetermined distance and / or predetermined time is not met in the initial moments of approach. With the invention, said ego vehicle approaches said target vehicle in the initial moments. Then, said ego vehicle will decelerate more and more as long as said criterion based on said predetermined distance and / or predetermined time is no longer met. However, the variation in acceleration will remain controlled and limited by the jerk.The corrected potential acceleration tends towards the value of the potential acceleration.

[0012] Taking initial acceleration into account when determining jerk makes it possible to avoid significant jolts in the event of a positive initial acceleration of the ego vehicle when the target vehicle merges into the lane in which the ego vehicle is traveling. The acceleration variation will remain controlled for all instantaneous accelerations of the ego vehicle.

[0013] As the ego vehicle decelerates, its speed will become lower than the target vehicle's speed. At this point, the target vehicle's criterion will be better met, its potential acceleration will decrease, and the change in potential acceleration will become less than the jerk. The corrected potential acceleration will gradually be replaced by the target vehicle's potential acceleration.

[0014] Therefore, the vehicle behaves similarly to a driver. Thanks to the invention, the acceleration pattern during docking is modified, achieving a good compromise between dynamic comfort (minimizing acceleration variations), physiological comfort (having minimal initial deceleration thanks to the jerk j0, allowing for proper consideration of the docking by the cruise control), and safety (having minimal acceleration and continuing to decelerate more and more as long as the speed of the ego vehicle is greater than the speed of the target vehicle).

[0015] Advantageously, the parameter k1 is determined by k1=k2 / DV, Or k2 is a predetermined parameter and DV is a parameter representing an average speed.

[0016] Advantageously, the corrected potential acceleration is determined by the formula A cor (t) = max(A pot (t), A cor (t-Δt)+J Min (t)*ΔT), ΔT being a sampling period, and A cor (t-Δt) being said corrected potential acceleration determined at the previous period.

[0017] Advantageously, the initial jerk j0 is a number between -0.1 and -1 m / s 3< in order to represent a release of foot, a variation in acceleration similar to engine braking in the absence of pressure on an accelerator pedal.

[0018] Advantageously, said jerk is greater than or equal to a potential jerk based on potential acceleration. A second aspect of the invention relates to a device comprising a memory associated with at least one processor configured to implement the method according to the first aspect of the invention.

[0019] The invention also relates to a vehicle incorporating the device.

[0020] The invention also relates to a computer program comprising instructions which, when the program is executed by the device according to the second aspect of the invention, lead the latter to implement the process according to the first aspect of the invention.

[0021] Other features and advantages of the invention will become apparent from the description of the non-limiting embodiments of the invention below, with reference to the accompanying figures, in which: [ Fig. 1 [ ] schematically illustrates a device, according to a particular embodiment of the present invention. ] Fig. 2 ] schematically illustrates a method of controlling the speed of an autonomous vehicle, according to a particular embodiment of the present invention.

[0022] The invention is described below in its non-limiting application to the case of an autonomous motor vehicle traveling on a road or traffic lane. Other applications, such as a robot in a warehouse or a motorcycle on a country road, are also conceivable.

[0023] There figure 1 represents an example of a device 101 included in the vehicle, in a network ("cloud") or in a server. This device 101 can be used as a centralized device responsible for at least some steps of the process described below with reference to the figure 2 In one embodiment, it corresponds to an autonomous driving computer.

[0024] In the present invention, the device 101 is included in the vehicle.

[0025] This 101 device can take the form of a case containing printed circuits, any type of computer or even a mobile phone (“smartphone”).

[0026] The device 101 includes a random access memory 102 for storing instructions for the implementation by a processor 103 of at least one step of the process as described above. The device also includes a mass storage 104 for storing data intended to be retained after the implementation of the process.

[0027] Device 101 may further include a digital signal processor (DSP) 105. This DSP 105 receives data to shape, demodulate and amplify, in a manner known per se, this data.

[0028] Device 101 also includes an input interface 106 for receiving data implemented by the method according to the invention and an output interface 107 for transmitting data implemented by the method according to the invention.

[0029] For example, the input interface 106 can receive the following data: vehicle position or geographic location, vehicle speed and / or acceleration, setpoint or predetermined positions / speeds / accelerations, engine speed, position and / or travel of the clutch, brake and / or accelerator pedal, detection of other vehicles or objects, position or geographic location of other vehicles or objects detected, speed and / or acceleration of other vehicles or objects detected, measured, determined and / or predetermined inter-vehicle distance, measured, determined and / or predetermined inter-vehicle time, sensor operating states, control variables such as potential acceleration, absolute time, relative time, control period, confidence index of data from or processed by sensors and / or devices similar to device 101.For example, sensors capable of providing data include: GPS associated or not with mapping, tachometers, accelerometers, RADAR, LIDAR, lasers, ultrasound, camera.

[0030] There figure 2 schematically illustrates a method for controlling the speed of an autonomous vehicle, according to a particular embodiment of the present invention. Said ego vehicle includes an adaptive cruise control system. Said cruise control determines a potential acceleration, A pot (t), at one moment tGiven. Said potential acceleration is based on a measurement of the vehicle's speed, a measurement of the inter-vehicle distance, and a predetermined inter-vehicle distance, referred to as the predetermined distance, and / or a predetermined inter-vehicle time, referred to as the predetermined time. Said potential acceleration corresponds to a change in speed over a predetermined period theoretically applied to said vehicle so that said vehicle meets a criterion based on said predetermined distance and / or said predetermined time, said controller controlling said vehicle's speed based on said potential acceleration.

[0031] Step 201, Apot, is a step for acquiring said potential acceleration, A pot (t). This potential acceleration is determined by the adaptive cruise control at each instant t. This potential acceleration is calculated by the ACC so that the ego vehicle, thanks to the regulation, reaches a certain speed within a predetermined time while maintaining a predetermined inter-vehicle time. For example, the potential acceleration is the average acceleration that the ego vehicle must have to reach the target vehicle's speed within a predetermined time while maintaining the predetermined inter-vehicle time.

[0032] Generally, the regulator is implemented by a device similar to device 101. The determination of the control setpoint is carried out periodically, for example at a sampling period. ΔT. A por (t-ΔT) is the potential acceleration of the previous period classically recorded in 104 type mass memory.

[0033] The potential acceleration is acquired by device 101 via its input interface 106. The potential acceleration is transmitted for example by the adaptive cruise control, by another device of type 101, by a programming interface called API, acronym for the English Application Program Interface.

[0034] Stage 202, Aego, is a stage of acquiring instantaneous acceleration, at a given instant t given, of said vehicle ego, A égo (t). The said instantaneous acceleration can be a measurement of the acceleration of the ego vehicle from a sensor (accelerometer, accelerometer data fusion, signal processing on speed measurements, ...) of said ego vehicle.

[0035] Instantaneous acceleration is acquired by device 101 via its input interface 106. Instantaneous acceleration is transmitted for example by a sensor of said vehicle, by the adaptive cruise control, by another device of type 101, by a programming interface called API, acronym for the English Application Program Interface.

[0036] Step 203, Jerk, is a step for determining a jerk, J Min (t). The jerk represents a change in acceleration. The determination of the jerk is based on the potential acceleration, the instantaneous acceleration, and a predetermined, strictly negative initial jerk. j0. The jerk is less than or equal to the initial jerk. The more negative the potential acceleration, the more negative the jerk.

[0037] Advantageously, the initial jerk j0is a number between -0.1 and -1 m / s³, preferably close to -0.5 m / s³. Other values ​​are acceptable. Thus, the initial jerk represents a release of the foot, a variation in acceleration similar to engine braking in the absence of pressure on an accelerator pedal, particularly during the first moments of docking.

[0038] Advantageously, said jerk is greater than or equal to a potential jerk based on the potential acceleration. For example, the potential jerk at an instant t is determined by the equation (A pot (t)- A pot (t-ΔT)) / ΔT or by a function based on the variation of the potential acceleration. Thus, a corrected potential acceleration, as described below, will be greater (less negative) than the potential acceleration. If the cruise control is based on the corrected setpoint acceleration, then the vehicle will brake less abruptly. The deceleration of said vehicle will be less severe.

[0039] In one operating mode, the jerk is equal to the initial jerk when the instantaneous acceleration is greater than or equal to the absolute value of the potential acceleration. Thus, thanks to the invention, the vehicle will decelerate more immediately. This deceleration, while not excessive, will be felt by the vehicle's passengers, who will understand that the ACC has indeed detected a target.

[0040] According to the invention, said Jerk, J min (t), is determined by the formula J Min (t)= k1*(A pot (t)+max(0, A égo (t))) 2< +j0 Or k1 is a negative preset adjustment parameter, max(.) being the maximum function.

[0041] Advantageously, the parameter k1 is determined by k1=k2 / DV, Or k2is a predetermined parameter, and DV is a parameter representing an average speed. For example, DV is the average of the differences between the speed of the ego vehicle and the speed of the target vehicle. Preferably, DV is a number greater than 0 and less than 100 km / h, and may be 50 km / h. k2 is a number determined from physical equations of a velocity trajectory over a predetermined time period. For example, k2 may be a number between -1 and -10, preferably close to -3.8. For example, k1 is a number between -0.001 and -1, preferably in the range of -0.06 to -0.9. k1 can also be viewed as a setting parameter that allows for the characterization of an adaptive cruise control based on the setpoint acceleration as described in the invention.

[0042] The jerk is more negative the more positive the acceleration of the ego vehicle is. Thus, if the ego vehicle was accelerating before the initial moments of docking, then the jerk will be more negative and the ego vehicle, with the invention, will be more responsive.

[0043] Step 204, Apot_cor, is a step for determining a corrected potential acceleration, A cor (t), based on said jerk, said jerk limiting the variation of the potential acceleration. Thus, thanks to the invention, the vehicle will decelerate less abruptly. Advantageously, said corrected potential acceleration is determined by the formula A cor (t) = max(A pot (t), A cor (t-Δt)+J Min (t)*ΔT), ΔT being a sampling period, and A cor (t-Δt)being said corrected potential acceleration determined at the previous period. Thus, the corrected potential acceleration will be the less negative acceleration between the potential acceleration and the corrected potential acceleration of the previous period plus a change in acceleration determined by said jerk. Naturally, after a few moments, on the order of a few tens or hundreds of sampling periods, the corrected potential acceleration will converge towards the potential acceleration determined by the state-of-the-art cruise control.

[0044] Step 205, Regul, is a step of regulating said vehicle speed by said adaptive cruise control based on said corrected potential acceleration.

[0045] Therefore, the vehicle behaves similarly to a driver. Thanks to the invention, the acceleration pattern during docking is modified, achieving a good compromise between dynamic comfort (minimizing acceleration variations), physiological comfort (having minimal initial deceleration thanks to the jerk j0, allowing for proper consideration of the docking by the cruise control), and safety (having minimal acceleration and continuing to decelerate more and more as long as the speed of the ego vehicle is greater than the speed of the target vehicle).

[0046] The present invention is not limited to the embodiments described above by way of example; it extends to other variants, within the limits of the attached claims.

[0047] Thus, we have described above an example of implementation with a certain order in the steps. Some steps can be carried out in parallel or in a different order while still achieving the same result.

[0048] Equations and calculations have also been detailed. The invention is not limited to the form of these equations and calculations, and extends to any other type of form, provided that these remain mathematically consistent with that set forth in the accompanying claims.

Claims

1. A method for controlling the speed of an autonomous vehicle, referred to as the ego vehicle, approaching a target vehicle, said ego vehicle having an adaptive cruise control, said cruise control determining a potential acceleration, Apot(t), at a given time t, said potential acceleration being based on a measurement of the speed of the ego vehicle, on a measurement of an inter-vehicle distance and on a predetermined inter-vehicle distance, referred to as the predetermined distance, and / or on a predetermined inter-vehicle time, referred to as the predetermined time, said potential acceleration being negative and corresponding to a change in speed over a predetermined time theoretically applied to said ego vehicle so that said ego vehicle meets a criterion based on said predetermined distance and / or on said predetermined time, said cruise control controlling said speed of said ego vehicle based on said potential acceleration, said method comprising the steps of: • Acquisition (201) of said potential acceleration, Apot(t); • Acquisition (202) of an instantaneous acceleration, at a given instant t, of said vehicle ego, Aégo(t); • Determination (203) of a jerk, JMin(t), representing a variation of acceleration, based on said potential acceleration, on said instantaneous acceleration and of a strictly negative predetermined initial jerk, j0 , said jerk being less than or equal to the initial jerk and said jerk being all the more negative as the potential acceleration is negative; • Determination (204) of a corrected potential acceleration, Acor(t), based on said jerk, said jerk limiting the variation of the potential acceleration; • Regulation (205) of said vehicle speed by said adaptive cruise control based on said corrected potential acceleration; characterized in that said Jerk, Jmin(t), is determined by the formula JMin(t)= k1*(Apor(t)+max(0, Aégo(t)))2+j0 where k1 is a predetermined negative tuning parameter, max(.) being the maximum function.

2. Method according to claim 1, wherein the parameter k1 is determined by k1=k2 / DV, where k2 is a predetermined parameter and DV is a parameter representing an average speed.

3. A method according to any one of the preceding claims, wherein said corrected potential acceleration is determined by the formula Acor(t) = max(Apot(t), Acor(t-Δt)+JMin(t)*ΔT), ΔT being a sampling period, and Acor(t-Δt) being said corrected potential acceleration determined at the previous period.

4. A method according to any one of the preceding claims, wherein the initial jerk j0 is a number between -0.1 and -1 m / s3 to represent a release of the foot, a variation in acceleration similar to engine braking in the absence of pressure on an accelerator pedal.

5. A method according to any one of the preceding claims, wherein said jerk is greater than or equal to a potential jerk based on potential acceleration.

6. Device (101) comprising a memory (102) associated with at least one processor (103) configured to implement the method according to one of the preceding claims.

7. Vehicle comprising the device according to the preceding claim.

8. Computer program comprising instructions which, when the program is executed by the device (101), cause the device to implement the method according to any one of claims 1 to 5.