Method and device for regulating the speed of an autonomous vehicle.

Abstract

The invention relates to a method and a device for regulating the speed of an autonomous vehicle in the presence of at least two target objects, respectively called the first object and the second object, said first object being upstream of a trajectory of said autonomous vehicle, said second object being upstream of a trajectory of said first object. The regulation (206) of the speed of said vehicle is a function of a determined regulation speed (205) from a first and a second speed (201), and of a time before contact (204). Figure to be published for the abstract: Figure 2

Description

Title of the invention: Method and device for regulating the speed of an autonomous vehicle. Technical field of the invention

[0001] The invention is in the field of autonomous vehicle driving assistance systems. In particular, the invention relates to a method and a device for regulating the speed of an autonomous vehicle in the presence of at least two target objects. State of the art

[0002] The term "vehicle" means any type of vehicle such as a motor vehicle, a moped, a motorcycle, a storage robot in a warehouse, etc. The term "autonomous driving" of an "autonomous vehicle" means any method capable of assisting the driving of the vehicle. The method may thus consist of partially or totally steering the vehicle or providing any type of assistance to a natural person driving the vehicle. The method thus covers all autonomous driving, from level 0 to level 5 in the OICA scale, for International Organization of Motor Vehicle Manufacturers.

[0003] Methods capable of assisting the driving of the vehicle are also called AD AS (from the English acronym "Advanced Driver Assistance Systems"), AD AS functions, AD AS systems or driving assistance systems. Among these AD AS systems, an adaptive cruise control is known.

[0004] Adaptive cruise control is also known as ACC (from the English acronym "Auto Cruise Control"). This system automatically maintains a vehicle speed, called the ego vehicle, at a value set by an occupant or driver of the vehicle, a value called the set speed, while respecting a safety distance from an object preceding the ego vehicle. For example, an object preceding the ego vehicle is a land vehicle, any type of obstacle, any disturbance, etc. The object is upstream of the ego vehicle, on a possible trajectory of the ego vehicle. The safety distance is determined from an inter-vehicle time, Tiv, set by the driver and from a speed of the ego vehicle.

[0005] An ACC generally uses a camera implanted at the top of a windshield of the ego vehicle and a radar implanted in a front bumper of the ego vehicle in order to detect and identify objects in an environment close to the vehicle. A vehicle equipped with an ACC is able to detect several objects in front of the ego vehicle, and is able to determine data associated with these objects such as a speed, a position, characteristics typing the object, ... An object is also called a target object if this object intervenes in the implementation of the ACC.

[0006] A set of maneuvers of an ACC is typically an activation of the ACC by the driver after having entered a set speed and an inter-vehicle time. In the absence of a target, the ACC regulates the speed of the vehicle to the set speed. When a target is detected, it is said that the ACC approaches the target: the speed of the vehicle is adapted according to the inter-vehicle distance and the set speed. When the target is no longer present, the speed is adapted according to whether or not a new target is detected.

[0007] Currently, a conventional ACC poorly manages the speed regulation of the ego vehicle in the presence of two distinct objects, the first object upstream of a trajectory of the ego vehicle, the second object upstream of a trajectory of the first object, in particular, when the speed of the first object is greater than the speed of the second object. If the ego vehicle, the first vehicle and the second vehicle are traveling on the same traffic lane, the first object will collide with the second object. In order to avoid the collision, the first object will certainly adopt abrupt behavior such as braking or changing lanes. A current ACC has difficulty anticipating the behavior of the first object in this situation. The ACC will brake sharply, and therefore uncomfortably for occupants of the ego vehicle, when the ego vehicle approaches the second object. Summary of the invention

[0008] An object of the present invention is to remedy the aforementioned problem, in particular to find a compromise over the whole of a maneuver by anticipating possible behaviors of the first object or vehicle and taking into account the second object. The speed of the vehicle is regulated more closely as a driver would.

[0009] To this end, a first aspect of the invention relates to a method for regulating a speed of an autonomous vehicle in the presence of at least two target objects, respectively called first object and second object, said first object being upstream of a trajectory of said autonomous vehicle, said second object being upstream of a trajectory of said first object, said method comprising the steps of: • Receiving a speed of said first target object, called first speed, and a speed of said second target object, called second speed; • If said first speed is greater than said second speed • Receiving a first distance and a second distance, said first distance being a distance between said vehicle autonomous vehicle and said first object, said second distance being a distance between said autonomous vehicle and said second object; • Determination of a time before contact between said first object and said second object; • Determination of a regulation speed from said first speed, said second speed and said time before contact; • Regulation of the speed of said vehicle according to said regulation speed.

[0010] Time to contact, or TOC, is the time, if the speeds of the first object and the second object do not change, that it takes for the first object to come into contact with the second object. If the first object and the second object are traveling on the same traffic lane, the first object will collide with the second object after the time to contact. Time to contact is an indicator of the dangerousness of a driving situation. The smaller the TOC, the more imminent contact is. The greater the difference between the speeds of the first object and the second object, and / or the higher the speed of the first object and / or the lower the speed of the second, the more abrupt the change in behavior of the first vehicle will be.

[0011] The regulation speed is determined by taking into account the important parameters, speed of the first object, speed of the second object, and time before contact between said first object and said second object. Since the speed regulator will use the determined regulation speed instead of the set speed, the invention then makes it possible to anticipate a behavior of the first object and the approach of the second object.

[0012] Advantageously, said regulation speed is determined using the formula VreS= V2+ ^^(TAC-TACjJ , where V reg is said regulation speed, V1 is said first speed, V 2 is said second speed, TAC is the determined time before contact, TA C h tet TA C lo are predetermined times before contact, TAC ht being strictly greater than TAC io.

[0013] Thus, the greater the risk of contact or collision (TAC is small), the lower the regularization speed is compared to the first speed. The vehicle will then move away from the first object in an anticipated manner. Conversely, the higher the TAC, the higher the regulation speed. However, the regulator maintains a safe distance from the first object based on the inter-vehicle time set by the driver. The regulator does not cause the speed of the ego vehicle to exceed the set speed. So, the regularization speed varies mainly between the second speed and the first speed depending on the time before contact between the first and second objects. This variation is continuous and without jerks as an attentive driver does. The speed variation of the ego vehicle is comfortable while anticipating the behavior of the first object and / or a future docking with the second object.

[0014] Advantageously, said regulation speed is saturated between said second speed and said first speed.

[0015] Thus, the regulation speed is at least equal to the speed of the second object, and is at most equal to the speed of the first object. The regulation speed varies continuously and smoothly between the second speed and the first speed. The variation in speed of the ego vehicle is then perceived comfortably by an occupant of the ego vehicle.

[0016] Advantageously, said regulation speed cannot be less than a safety speed, said safety speed being equal to said first speed subtracted from a predetermined value.

[0017] Thus, the regulation speed will be at least equal to the safety speed. In one operating mode, the regulation speed will be at least equal to a maximum between the safety speed and the second speed. The regulation speed still varies continuously and smoothly. The minimum speed remains "fairly close" to the first speed; in fact, the smaller the predetermined value, the closer the safety speed is to the first speed. This ensures that the regulation speed is not too far from the first speed and / or the set speed. This makes it possible to take into account the case where the first object is traveling at a high speed, close to a speed limit, for example on a highway. In this situation, the inter-vehicle distance between the vehicle and the first object is large.A driver naturally agrees to travel faster than a second object that he sees in the distance in front of the first object having at least one lane to escape from a possible future dangerous situation (for example, a second object in an accident, broken down, etc.).

[0018] Advantageously, said time before contact, TAC, is determined using the formula TAC = '°where DJ is said first distance, D2 is said second distance, VI is said first speed, and V 2 is said second speed.

[0019] The time before contact is determined in a very simple way. It is an estimate of a distance between the first object and the second object. It is not necessary to know a length in the longitudinal direction of the first object.

[0020] 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.

[0021] The invention also relates to a vehicle comprising the device.

[0022] 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 method according to the first aspect of the invention. Brief description of the figures

[0023] Other characteristics and advantages of the invention will emerge from the description of the non-limiting embodiments of the invention below, with reference to the appended figures, in which:

[0024] [Fig.l] schematically illustrates a device, according to a particular example of embodiment of the present invention.

[0025] [Fig.2] schematically illustrates a method for regulating the speed of an autonomous vehicle, according to a particular exemplary embodiment of the present invention. Detailed description of the invention

[0026] The invention is described below in its non-limiting application to the case of an autonomous motor vehicle traveling on a road or on a traffic lane. Other applications such as a robot in a storage warehouse or a motorcycle on a country road are also conceivable.

[0027] [Fig. 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 in charge of at least certain steps of the method described below with reference to [Fig. 2]. In one embodiment, it corresponds to an autonomous driving computer.

[0028] In the present invention, the device 101 is included in the vehicle.

[0029] This device 101 can take the form of a box comprising circuits printed, from any type of computer or even from a mobile phone (“smartphone”).

[0030] The device 101 comprises a random access memory 102 for storing instructions for the implementation by a processor 103 of at least one step of the method as described above. The device also comprises a mass memory 104 for storing data intended to be retained after the implementation of the method.

[0031] The device 101 may further comprise a digital signal processor (DSP) 105. This DSP 105 receives data to format, demodulate and amplify, in a manner known per se, this data.

[0032] The device 101 also comprises an input interface 106 for receiving the data implemented by the method according to the invention and an output interface 107 for transmitting the data implemented by the method according to the invention.

[0033] For example, the input interface 106 can receive the following data: position or geographical location of the vehicle, speed and / or acceleration of the vehicle, set or predetermined positions / speeds / accelerations, engine speed, position and / or travel of the clutch, brake and / or acceleration pedal, detection of other vehicles or objects, position or geographical location of the other vehicles or objects detected, speed and / or acceleration of the other vehicles or objects detected, operating states of sensors, confidence index of data originating from or processed by sensors and / or devices similar to the device 101. For example, the sensors capable of providing data are: GPS associated or not with mapping, tachometers, accelerometers, RADAR, LIDAR, lasers, ultrasound, camera, etc.Also, sensors not present in the vehicle can transmit this data via electromagnetic, light, or other waves and a communication protocol, and other sensors present in the vehicle are able to receive this data. For example, the input interface 106 may also receive time-to-contact data between a first and second object traveling upstream of a trajectory of the vehicle.

[0034] For example, the output interface 107 may transmit data similar to the data received by the input interface 106 or transmit data such as a regulation speed.

[0035] [Fig.2] schematically illustrates a method of regulating a speed of a autonomous vehicle, called ego vehicle, according to a particular embodiment of the present invention. At least two target objects, called respectively first object and second object, are present in an environment of the ego vehicle.

[0036] Sensors present in the vehicle or outside the vehicle, after data processing, are capable of detecting these objects and are capable of determining data relating to these objects. In particular, these sensors are capable of determining: - whether said first object is upstream of a trajectory of said autonomous vehicle, - if said second object is upstream of a trajectory of said first object, - a speed of the first object, a speed of the second object, - a distance between the ego vehicle and the first object, - a distance between the first object and the second object, ...

[0037] It is not necessary for the first object and / or the second object to travel on the same traffic lane as the vehicle. For example, if the first object and the second object are on a lane adjacent to the lane on which the ego vehicle is traveling, the aforementioned problem may be present when the ego vehicle changes lanes to travel on the lane on which the first object is traveling. Another example, if the ego vehicle is traveling on the same lane as the first object and the second object is traveling on an adjacent lane, the aforementioned problem may be present when the ego vehicle changes lanes to travel on the lane on which the second object is traveling.

[0038] Step 201, RxVl, V2, is a step of receiving a speed of said first target object, called first speed, and a speed of said second target object, called second speed. The speeds are received by the interface 106 of the device 101.

[0039] Step 202, V 1>V2 ?, is a test step to determine whether said first speed is greater than the said second speed. If so, we move on to step 203.

[0040] Step 203, RxD1, D2, is a step of receiving a first distance and a second distance, said first distance being a distance between said autonomous vehicle and said first object, said second distance being a distance between said autonomous vehicle and said second object. The distances are received by the interface 106 of the device 101.

[0041] Step 204, TAC, is a step of determining a time before contact between said first object and said second object. The time before contact can be determined in several ways. In one operating mode, said time before contact, TAC, is determined using the formula t AC — , where DI is said first distance, D2 is said second distance, VI is said first speed, and V 2 is said second speed. In another operating mode, the time before contact is smoothed, by digital filtering, over a predetermined time window. In another operating mode, the input interface receives data representative of a length of the first object and the time before contact is also a function of this length. In another operating mode, the input interface 106 receives the distance between the ego vehicle and the first object and a relative distance between the second object and the first object. Said relative distance is determined by said first object and / or a roadside means. This determination is transmitted by an electromagnetic wave, then received by the ego vehicle by a device similar to the device 101.

[0042] Step 205, Vreg, is a step of determining a regulation speed from said first speed, said second speed and said time before contact.

[0043] Time to contact, or TAC, is the time, if the speeds of the first object and the second object do not change, that it takes for the first object to come into contact with the second object. If the first object and the second object are traveling in the same lane, the first object will collide with the second object after the time to contact. The time to contact is an indicator of the dangerousness of a driving situation. The smaller the TAC, the more imminent contact is. The greater the difference between the speeds of the first object and the second object, and / or the higher the speed of the first object and / or the lower the speed of the second, the more abrupt the change in behavior of the first vehicle will be. If the first object and the second object are not traveling in the same lane, the smaller the time to contact, the more abrupt the collision with the second object will be.

[0044] The regulation speed is determined by taking into account the important parameters, speed of the first object, speed of the second object, and time before contact between said first object and said second object. Since the speed regulator will use the determined regulation speed instead of the set speed, the invention then makes it possible to anticipate the behavior of the first object and the approach of the second object.

[0045] Several methods allow this regulation speed to be calculated as a function of the time before contact between the first and second objects, as a function of the first speed and as a function of the second speed. For example, if the time before contact is greater than a threshold (for example 1 second, other values ​​are possible) the regulation speed is equal to the first speed, otherwise the regulation speed is equal to the second speed. The speed jump, between the first speed and the second speed, especially if the difference between these two speeds is large, can then be softened or smoothed using a digital filter.

[0046] Advantageously, said regulation speed is determined using the formula Vreg = V2 + TAc1^ac1o (TAC - TAClo) , where V reg is said regulation speed, V1 is said first speed, V 2 is said second speed, TAC is the determined time before contact, TA C h tet TA C lo are predetermined times before contact, TAC ht being strictly greater than TAC lo

[0047] Thus, the greater the risk of contact or collision (TAC is small), the lower the regularization speed is compared to the first speed. The vehicle will then move away from the first object in an anticipated manner. Conversely, the higher the TAC, the higher the regulation speed. However, the regulator maintains a safe distance from the first object based on the inter-vehicle time set by the driver. The regulator does not cause the speed of the ego vehicle to exceed the set speed. So, the regularization speed varies mainly between the second speed and the first speed depending on the time before contact between the first and second objects. This variation is continuous and without jerks as an attentive driver does. The speed variation of the vehicle ego is comfortable while anticipating a behavior of the first object and / or a future docking with the second object

[0048] The predetermined times before contact, TAC hi and TAC / o, are adjustment parameters. They are obtained, for example, using simulations, vehicle tests, etc. They make it possible to compensate for an error in measuring the time before contact if the length of the first object is not known. TAC io, "lo" for "low", from the English "bas", is less than TAC hi, "hi" for "high" from the English "haut".

[0049] For example, a value of TAC / o is between 0.2 and 1 second. Other values ​​are possible. If the time before contact becomes less than TAC / o, the first object is very close to the second object (approximately 5 meters, if Vl = 35 m / s, V2 = 25 m / s and TAC = 0.5 s), it will certainly perform an avoidance maneuver or sudden braking. The invention makes it possible to reduce the regulation speed progressively when the TAC decreases. The regulation speed will become lower than the second speed to limit the risks of a collision between the ego vehicle and the second vehicle in the case where the driver of the ego vehicle has not already taken control of the speed regulation.

[0050] For example, a value of TAC hi is between 2 and 15 seconds. Other values ​​are possible. If the time before contact becomes greater than TAC hi, the first object is at a comfortable distance from the second object (approximately 50 meters, if Vl=35 m / s, V2=25 m / s and TAC=10 s). This leaves more time and distance for the first object to perform an evasive maneuver or to perform progressive braking. The regulation speed will become greater than the first speed. However, the regulator also takes into account the set speed and the inter-vehicle time, therefore the inter-vehicle distance as well, between the ego vehicle and the first object. Naturally, the speed of the ego vehicle will tend towards the first speed, if the first speed is lower than the set speed. Thus, this also leaves time and distance for the driver of the ego vehicle to react.

[0051] Advantageously, said regulation speed is saturated between said second speed and said first speed. If the time before contact becomes less than TAC io, the regulation speed is equal to the second speed. The ego vehicle will move away from the first object which is traveling at the first speed greater than the second speed, thus leaving time and distance for the driver of the ego vehicle to react. The ego vehicle begins the docking with the second vehicle thus avoiding heavy braking. If the time before contact becomes greater than TAC hh the speed of regulation is equal to first gear. There is less risk of contact or collision, the vehicle maintains its distance from the first object.

[0052] Thus, the regulation speed is at least equal to the speed of the second object, and at most equal to the speed of the first object. The regulation speed varies continuously and smoothly between the second speed and the first speed. This avoids slowing down too much or accelerating too much. The variation in speed of the ego vehicle is then comfortably perceived by an occupant of the ego vehicle.

[0053] Advantageously, said regulation speed cannot be lower than a safety speed, said safety speed being equal to said first speed subtracted from a predetermined value. Thus, the regulation speed will be at least equal to the safety speed. In one operating mode, the regulation speed will be at least equal to a maximum between the safety speed and the second speed. The regulation speed still varies continuously and smoothly. The minimum speed remains “fairly close” to the first speed; in fact, the smaller the predetermined value, the closer the safety speed is to the first speed. This ensures that the regulation speed is not too far from the first speed and / or the set speed. This makes it possible to take into account the case where the first object is traveling at a high speed, close to a speed limit, for example on a motorway.In this situation, the inter-vehicle distance between the vehicle and the first object is large. A driver naturally agrees to travel faster than a second object that he sees in the distance in front of the first object having at least one lane to escape a possible future dangerous situation (for example, a second object in an accident, broken down, etc.).

[0054] For example, the predetermined value is between 4 and 10 m / s. Other values ​​are possible. Thus, for example on a motorway, if Vl=35 m / s, if V2=25 m / s, if the predetermined value is equal to 6 m / s, the regulation speed is not less than 29 m / s. The vehicle feels more sporty at high speed (around the speed limit on a motorway) than at lower speed (for example on a departmental road).

[0055] Step 206, reg, is a step of regulating the speed of said vehicle as a function of said regulation speed. An ACC takes into account the inter-vehicle time set by the driver, the set speed set by the driver and the regulation speed. The regulator will make it possible to converge the speed of the vehicle towards the regulation speed determined by the invention while respecting the driver's instructions, and thus obtain the aforementioned advantages of the invention.

[0056] The present invention is not limited to the embodiments described above as examples: it extends to other variants.

[0057] Thus, an embodiment has been described above in which the invention was described in the context of the application to adaptive speed regulation. The invention is not not limited to such an application and can be implemented for example for methods / devices for keeping in the lane or for decision-making for changing lanes, or other AD AS systems which use speed regulation.

[0058] An embodiment has also been described above in which two objects are detected. The invention is not limited to such an application and can be implemented for example when more than two objects are detected.

[0059] Equations and calculations have further been detailed. The invention is not limited to the form of these equations and calculations, and extends to any type of other mathematically equivalent form.

[0060] Furthermore, the steps described with reference to [Fig.2] have been done in a specific order. A different order is also possible. For example, step 203 can be performed before or simultaneously with step 201.

Claims

Claims

1. Method for regulating a speed of an autonomous vehicle in the presence of at least two target objects, respectively called first object and second object, said first object being upstream of a trajectory of said autonomous vehicle, said second object being upstream of a trajectory of said first object, said method comprising the steps of: - Receiving (201) a speed of said first target object, called first speed, and a speed of said second target object, called second speed; - If (202) said first speed is greater than said second speed • Receiving (203) a first distance and a second distance, said first distance being a distance between said autonomous vehicle and said first object, said second distance being a distance between said autonomous vehicle and said second object; • Determining (204) a time before contact between said first object and said second object;• Determination (205) of a regulation speed from said first speed, said second speed and said time before contact; • Regulation (206) of the speed of said vehicle as a function of said regulation speed, characterized in that said regulation speed is determined using the formula Vreÿ= V2+ta^acJTAC-TACIo), where V reg is said regulation speed, V1 is said first speed, V 2 is said second speed, TAC is the determined time before contact, TAC h tet TA C lo are predetermined times before contact, TAC hi being strictly greater than TA C to..;

2. The method of claim 1, wherein said regulating speed is saturated between said second speed and said first speed.

3. A method according to any preceding claim, wherein said regulating speed cannot be less than a safety speed, said safety speed being equal to said first speed subtracted from a predetermined value.

4. A method according to one of the preceding claims, wherein said time to contact, TAC, is determined using the formula TAC = , where DI is said first distance, D2 is said second distance, VI is said first speed, and V2 is said second speed.

5. 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.

6.

7. Vehicle comprising the device according to the preceding claim. Computer program comprising instructions which, when the program is executed by the device (101), cause the latter to implement the method according to one of claims 1 to 4.

Images