METHOD FOR CONTROLLING THE LONGITUDINAL SPEED OF A MOTOR VEHICLE

Description

[0001] The invention relates to a method for managing the longitudinal speed of a motor vehicle. The invention further relates to a device for managing the longitudinal speed of a motor vehicle. The invention also relates to a computer program implementing the aforementioned method. Finally, the invention relates to a recording medium on which such a program is recorded.

[0002] Automated speed management systems are commonly installed on current vehicles, and are evolving to incorporate new features.

[0003] One development involves the automated management of gear changes at a specific location, such as stopping a vehicle at a road sign, like a stop sign, or at a traffic light. This functionality requires precisely tracking the vehicle's position relative to the gear change location over time, for example, relative to the position of the road sign. Furthermore, this functionality must implement a speed profile that meets driving comfort criteria, including the application of maximum acceleration and jerk thresholds.

[0004] Document FR1913267 describes a method for achieving longitudinal position control of the vehicle over time, thus allowing the timing of the vehicle's passage at a precise point on the road to be controlled. However, this solution has drawbacks. In particular, it does not guarantee compliance with driving comfort criteria regarding the application of maximum acceleration and jerk thresholds. When the vehicle is supposed to stop at a specific location, existing systems show that the vehicle's positioning is not always correct. For example, the vehicle may stop too far before a stop line and have to accelerate or interrupt its braking to reach it. Conversely, the vehicle may generate sudden and unpleasant braking for passengers if a stop line is about to be crossed.

[0005] Furthermore, US patent 8924049B2 describes a method for defining a speed profile based on various route parameters, including a speed limit associated with each segment of the route. This method allows the vehicle's speed to be regulated relative to a speed limit determined by its position. However, this solution also has drawbacks; its accuracy and reliability could be improved.

[0006] Similarly, US2016121898A1 describes another method for managing the longitudinal speed of a motor vehicle.

[0007] The aim of the invention is to provide a method for managing the longitudinal speed of a motor vehicle that overcomes the aforementioned drawbacks and improves upon prior art methods for managing the longitudinal speed of motor vehicles. In particular, the invention enables the implementation of a simple and reliable method that allows for a comfortable speed profile and the application of a gear change at a precise position.

[0008] To this end, the invention relates to a method for managing the longitudinal speed of a motor vehicle, the motor vehicle traveling along a planned trajectory, the motor vehicle being equipped with at least one means for detecting the vehicle's environment and an odometry means.

[0009] The process includes the following steps: a detection step, based on data from at least one detection means, of a speed change point located on the given trajectory and in front of the motor vehicle, and of determining a speed limit applicable to the speed change point, then a second step of calculating a first speed setpoint for the motor vehicle, based on the speed limit and a first distance separating the motor vehicle from the speed change point, the first distance being calculated based on a planned speed profile, the first distance having a margin of error in distance compared to a second distance determined by the odometry means between the motor vehicle and the speed change point,then a third step comprising determining a second speed setpoint that compensates for the margin of error in distance generated in the second step and anticipates a phase delay generated in a fourth step of controlling the movement of the motor vehicle, then a fourth step of controlling the movement of the motor vehicle according to the second speed setpoint to reach the speed change point with a speed equal to the limit speed, the fourth step generating the phase delay between the receipt of the second speed setpoint and the movement of the vehicle according to the second speed setpoint.

[0010] The motor vehicle may be equipped with a means of measuring the instantaneous speed of the vehicle, and the fourth step may include determining a setpoint for the acceleration of the motor vehicle as being the sum of a first and a second acceleration component.

[0011] The first acceleration component can be calculated by applying a first-degree differentiator filter to the second speed setpoint.

[0012] The second acceleration component can be obtained by applying a first proportional gain regulator to the difference between an instantaneous vehicle speed determined by the speed measurement means and a filtered speed setpoint.

[0013] The filtered speed setpoint can be obtained by successively applying a first and second first-order filter to the second speed setpoint.

[0014] The first filter can apply a phase delay to the second speed setpoint so as to synchronize the second speed setpoint with the first acceleration component, and the second filter can be parameterized so that the filtered speed setpoint converges to a stable value.

[0015] The second speed command is the sum of a first and a second speed component.

[0016] The first speed component can be obtained by applying a first and second phase-lead filter to the first speed setpoint, and the second speed component can be obtained by applying a second proportional controller including a given gain to the margin of error in distance, the given gain being set so that the second speed component converges to a stable value.

[0017] The same time constant can be used to define the first phase-lead filter applied for calculating the second speed setpoint, the first-degree differentiator filter, and the first phase-lag filter applied for calculating the acceleration setpoint.

[0018] The same time constant can be used to define the second phase-lead filter applied for calculating the second speed setpoint, as well as the second phase-lag filter applied for calculating the acceleration setpoint.

[0019] The vehicle may include a human-machine interface allowing a user to set a fourth speed setting, and the third step may include a modification of the second speed setting as the minimum between the second speed setting and the fourth speed setting.

[0020] The vehicle may include a target tracking module determining a third speed setpoint, and the third step may include a modification of the second speed setpoint as being the minimum between the second speed setpoint, the third speed setpoint, and the fourth speed setpoint.

[0021] The speed limit can be zero.

[0022] The invention further relates to a device for managing the longitudinal speed of a motor vehicle, the vehicle being equipped with a torque controller.

[0023] The invention also relates to a computer program product comprising program code instructions stored on a computer-readable medium for implementing the steps of the process as defined above when said program is run on a computer. The invention further relates to a computer program product downloadable from a communication network and / or stored on a computer-readable and / or computer-executable data medium, comprising instructions which, when the program is executed by the computer, cause the computer to implement the process as defined above.

[0024] The invention further relates to a computer-readable data storage medium on which is stored a computer program comprising program code instructions for implementing the process as defined above. The invention further relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to implement the process as defined above.

[0025] The invention also relates to a signal from a data carrier, carrying the computer program product as defined above.

[0026] The attached drawing represents, by way of example, an embodiment of a device for managing the longitudinal speed of a motor vehicle according to the invention and an execution method of managing the longitudinal speed of a motor vehicle according to the invention. [ Fig. 1 ] There figure 1 represents a motor vehicle equipped with a device for managing the longitudinal speed of a motor vehicle. Fig. 2 ] There figure 2 is a flowchart of an execution method for a process of managing the longitudinal speed of a motor vehicle. Fig. 3 ] There figure 3 schematically represents the processes carried out in steps E2 to E4 of the longitudinal speed management process of a motor vehicle. Fig. 4 ] There figure 4 illustrates the effect of implementing the longitudinal speed management process of a motor vehicle.

[0027] An example of a motor vehicle 100 equipped with an embodiment of a longitudinal speed management device for an autonomous vehicle is described below with reference to the figure 1 .

[0028] The motor vehicle 100 can be any type of motor vehicle, including a passenger car, a commercial vehicle, a truck, or a public transport vehicle such as a bus or shuttle. According to the embodiment described, the motor vehicle 100 is an autonomous vehicle and will be referred to as "autonomous vehicle" in the remainder of this description.

[0029] This illustration is therefore not exhaustive. In particular, the motor vehicle could be a non-autonomous vehicle equipped with a driver assistance system, specifically a driver assistance system corresponding to a level of autonomy equal to or greater than level 2, i.e., corresponding to partial vehicle autonomy.

[0030] It is assumed that the autonomous vehicle 100 moves along a planned trajectory T passing through a speed change point P located at the front of the autonomous vehicle.

[0031] In the remainder of this document, the term "speed change point" is used to refer to a piece of road infrastructure that establishes a speed limit at or from the location of that piece of infrastructure. Depending on the type of speed change point, the speed limit may be a maximum speed. This is the case, for example, if the speed change point is a speed limit sign or a yield sign.

[0032] The gear change point can also be a signpost (for example a stop sign) or a traffic light that can command the autonomous vehicle to stop at the gear change point.

[0033] If there are multiple road signs or lights on the route in question, the speed change point is the one that the autonomous vehicle will reach first.

[0034] The longitudinal speed management system is particularly relevant to speed change points that involve a reduction in speed, or even a complete stop, of the autonomous vehicle. Indeed, in the case of a speed change point involving a reduction in speed, or more specifically a complete stop, maintaining the correct position of the speed change point can be crucial. In one embodiment, the longitudinal speed management system could only consider speed change points that involve a complete stop of the autonomous vehicle, or a reduction in speed below a given threshold.

[0035] The term "gear change position" refers to the position of the gear change point.

[0036] The autonomous vehicle 100 includes a management system 10 and a torque controller 7. The torque controller 7 receives acceleration commands generated by the management system 10. In order to implement a longitudinal movement of the autonomous vehicle 100, the torque controller 7 transforms each acceleration command into a first torque command intended for a powertrain of the vehicle and / or a second torque command intended for a brake actuator of the vehicle.

[0037] The management system 10 mainly comprises the following elements: at least one detection means 1, an odometry means 2, a means for measuring the instantaneous speed of the autonomous vehicle 3, or speed sensor 3, a target tracking module 4, a human-machine interface 5 and a computing unit 6 comprising a microprocessor 61, an electronic memory 62 and communication interfaces 63 enabling the microprocessor 61 to communicate with the detection means 1, the odometry means 2, the instantaneous speed measurement means 3, the target tracking module 4, and the human-machine interface 5.

[0038] The detection means 1 may include a GPS location means for the autonomous vehicle 100 on a standard definition map, or on a high definition map. In this embodiment, the range of the detection means 1 is on the order of several hundred meters and its accuracy is determined by the accuracy of the GPS location, which is on the order of a few meters.

[0039] From the mapping and data from the GPS, the detection means 1 is able to detect a speed change point located on the planned trajectory T of the autonomous vehicle 100, from a current position of the autonomous vehicle 100. The data from the detection means 1 thus makes it possible to determine the speed change position.

[0040] Advantageously, the detection means 1 may further include equipment with a precision exceeding that of GPS positioning. This equipment may be, for example, a front-facing camera and / or a lidar. In this embodiment, the images from the front-facing camera and / or the lidar enable the detection of the speed change position with an accuracy on the order of tens of centimeters.

[0041] The odometry means 2 evaluates a distance DP traveled by the vehicle from a given point, for example, from the starting point of a route. In one embodiment, the distance traveled DP can be obtained by integrating the speed of the autonomous vehicle 100. In an alternative embodiment, the odometry means 2 could include a means for high-precision positioning of the autonomous vehicle on a map, for example, by using a GPS sensor; from the vehicle's positioning, the odometry means could calculate the distance traveled DP.

[0042] The distance traveled DP is then used to estimate the curvilinear distance DM separating the autonomous vehicle 100 from the speed change point P.

[0043] Speed ​​sensor 3 provides the instantaneous speed of autonomous vehicle 100 at all times. Speed ​​sensor 3 may include, for example, wheel rotation sensors of autonomous vehicle 100.

[0044] The management system 10 determines a first and second speed setpoint CV1, CV2 which will be described later in this document.

[0045] Target tracking module 4 determines a third speed command CV3 to maintain a following distance between the autonomous vehicle 100 and one or more surrounding vehicles. In a preferred embodiment, at least one target is detected in the traffic ahead of the autonomous vehicle 100. In this embodiment, at least one target may be located in the autonomous vehicle's lane of travel; for example, at least one target may include a first vehicle located in front of the autonomous vehicle and in its lane of travel, as well as a second vehicle located in front of the first target vehicle and in the same lane of travel. Additionally, when the autonomous vehicle is traveling on a multi-lane road in the same direction, at least one target may also include one or more vehicles posing a risk of merging into the autonomous vehicle 100's lane of travel.Vehicles at risk of merging are detected in the lane(s) adjacent to the autonomous vehicle 100's lane of travel in the traffic ahead of the autonomous vehicle 100. They are located in front of the autonomous vehicle 100, which can include situations where a vehicle is overtaking the autonomous vehicle 100 or vice versa. In other words, a vehicle can be detected as being at risk of merging when it is traveling parallel to the autonomous vehicle 100. When no target is detected in the environment of the autonomous vehicle 100, the third speed command CV3 is undefined.

[0046] The human-machine interface 5 allows a user of the autonomous vehicle 100 to determine a fourth speed setting CV4. The human-machine interface 5 could, for example, be an input screen located on the dashboard of the autonomous vehicle 100. In a preferred embodiment (described later in this document), the fourth speed setting CV4 is always defined. In an alternative, undescribed embodiment, the fourth speed setting might not be defined.

[0047] In one embodiment, the microprocessor 61 allows the execution of software comprising the following modules, which collaborate with each other: a module 611 for detecting a gear change point and determining a speed limit applicable to the gear change point, which collaborates with at least one detection means 1, , a module 612 for calculating a first speed setpoint CV1, a module 613 for determining a second speed setpoint CV2, which collaborates with the odometry means 2, the target tracking module 4 and the human-machine interface 5, the determination of the second speed setpoint CV2 taking into account the second and third speed setpoints CV3, CV4 according to an arbitration strategy described later in this document, a module 614 for controlling the movement of the autonomous vehicle according to the second speed setpoint CV2, which collaborates with the speed sensor 3.

[0048] An execution method for the speed management process of an autonomous vehicle is described below with reference to the figure 2 The process comprises four steps, E1 to E4.

[0049] In step E1, a speed change point P, located on the planned trajectory T of the autonomous vehicle 100 and in front of the autonomous vehicle, is detected from the data from at least one detection means 1, and a speed limit VL applicable to the speed change point P is determined.

[0050] For this purpose, the data from the detection means 1 are compared to the planned trajectory T.

[0051] For example, in an embodiment where the detection means 1 is achieved by a GPS location of the autonomous vehicle on a map, the trajectory planning, vehicle position and mapping information are combined to search for the presence of a speed change point P on the portion of the route located in front of the autonomous vehicle 100 and within the range of the first detection means 1.

[0052] At a given time T0, at least one speed limit or stop sign is detected on this section of the route. If several signs are detected on this section of the route, the sign closest to the autonomous vehicle 100 will be identified as the speed change point P.

[0053] Mapping data allows a speed limit (VL) to be associated with a speed change point (P). For example, if the speed change point P is marked by a speed limit sign, the speed limit (VL) is the speed indicated on the speed limit sign. A speed change point can also be marked by a change in road type, such as the end of a section of expressway or motorway leading onto a different type of road, such as a section of national or departmental road. The speed limit (VL) is then determined by the regulations defined for that different type of road. A speed change point P can also be marked by a stop sign, in which case the speed limit (VL) is zero.In other situations where the speed change point P corresponds to an intersection where the autonomous vehicle 100 does not have priority, for example a roundabout or an intersection with traffic lights, the speed VL can be close to zero.

[0054] Then, following step E1, we iterate, on steps E2 to E4 until the autonomous vehicle 100 reaches the speed change point P.

[0055] Steps E2 to E4 are described below with reference to the figure 3 .

[0056] In the second step E2, we calculate a first speed setpoint CV1 of the autonomous vehicle 100, as a function of the speed limit VL and a first distance DT, planned as a function of time, separating the autonomous vehicle 100 from the speed change point P.

[0057] The first distance DT is a theoretical distance, meaning it will be calculated during each iteration of step E2 based on a predictive velocity profile PVP described below. In the remainder of this document, the first distance DT is referred to as the "theoretical distance DT".

[0058] During the first iteration of step E2, i.e. at time T0, the theoretical distance DT is equal to the initial curvilinear distance D0 calculated between the position of the autonomous vehicle 100 at time T0 and the position of the speed change point P.

[0059] During the first iteration of step E2, a predictive speed profile PVP is calculated on the portion of the route linking the position at time T0 of the autonomous vehicle 100 to the position of the speed change point P.

[0060] In the remainder of the document, the term "speed profile" refers to time evolution curves of longitudinal speed, longitudinal acceleration and longitudinal jerk of the autonomous vehicle 100, the longitudinal jerk being the derivative of the longitudinal acceleration of the autonomous vehicle 100.

[0061] The predictive speed profile PVP is calculated so that the autonomous vehicle 100 travels at VL speed when it reaches the speed change point P.

[0062] Furthermore, the predictive speed profile (PVP) is calculated to allow the autonomous vehicle 100 to travel along route T, between its position at time T0 and the speed change point P, according to comfort criteria required for vehicle users. These comfort criteria may include adherence to maximum acceleration and jerk thresholds.

[0063] Thus, at time T0, we determine the predictive speed profile PVP of the autonomous vehicle 100 from its position at time T0 until its arrival at the speed change point P. In particular, the speed profile includes a theoretical time evolution curve VT(t) of the autonomous vehicle 100.

[0064] During subsequent iterations of step E2, the autonomous vehicle 100 is assumed to move according to the predictive speed profile PVP established at time T0. Therefore, at each iteration time t of step E2, we can calculate a first speed instruction CV1=VT(t), and a theoretical distance DT(t) between the autonomous vehicle and the speed change point P, DT(t) evolving according to a decreasing curve between the value D0 at T0 and the value 0 at the time of arrival at the speed change point P.

[0065] The theoretical distance DT(t) between the autonomous vehicle and the speed change point P is calculated according to the following formula: DT t = D 0 − DPT t Or D0 is the distance calculated at time T0 between the autonomous vehicle 100 and the speed change point P, DPT(t) is the distance that has been theoretically traveled by autonomous vehicle 100 moving according to the predictive speed profile PVP between times T0 and t.

[0066] The first distance DT thus calculated being theoretical, it presents a margin of error in distance ΔD compared to a second distance DM determined by the odometry means 2 between the autonomous vehicle 100 and the speed change point P.

[0067] We then proceed to step E3. The third step E3 includes the determination of a second speed setpoint CV2 which compensates for the margin of error in distance ΔD generated in the second step E2 and which anticipates a delay ΔT generated in the fourth step E4 of commanding the movement of the autonomous vehicle 100.

[0068] Step E3 includes a determination at time t of an estimated distance DM(t) between the autonomous vehicle and the speed change point P, from the data from the odometry means 2.

[0069] The odometry method 2 evaluates a distance DP(t) traveled by the vehicle between the time T0 of detection of the speed change point and time t. In particular, the distance DP(t) can be obtained by integrating the speed of the autonomous vehicle 100 between times T0 and t. The estimated distance DM(t) between the autonomous vehicle 100 and the speed change point P is then equal to the difference between the initial distance D0 and the distance traveled DP(t).

[0070] Alternatively, the distance DM(t) could be estimated from images from a front camera, when the velocity change point P enters the detection zone of the front camera.

[0071] Step E3 further includes the calculation, at time t, of a second speed setpoint CV2(t) from the first speed setpoint CV1(t) and the difference between the theoretical distance DT(t) and the estimated distance DM(t).

[0072] The calculation of the second speed setpoint CV2(t) is defined to compensate for two factors inducing an inaccuracy in the temporal evolution of the position of the autonomous vehicle 100 along its trajectory T: a first factor of inaccuracy is linked to a difference between the theoretical distance DT(t) calculated according to the formula Math1 and the actual distance separating, at time t, the autonomous vehicle 100 from the speed change point P, a second factor of inaccuracy is linked to a phase delay ΔT induced by a feedback loop between speed and acceleration, this loop being implemented in the next step of the processing, i.e. in step E4.

[0073] To compensate for these inaccuracies, in step E3 two corrections F1 and F2 are implemented, correcting respectively the first and second inaccuracies. the first correction F1 is a distance regulation loop, taking as input the difference ΔD(t) between the theoretical distance DT(t) and the estimated distance DM(t), the second correction F2 includes two phase-lead filters applied between the first speed setpoint CV1 and the second speed setpoint CV2.

[0074] The first correction F1 aims to correct the initial speed setpoint CV1(t) proportionally to a distance deviation ΔD(t) measured relative to the predictive speed profile PVP. To achieve this, the first correction F1 applies a proportional controller F11, comprising a given gain KD, specifically a multiplicative gain KD, to the deviation ΔD(t) between the theoretical distance DT(t) calculated using formula Math1, and the estimated distance DM(t) between the autonomous vehicle and the speed change point P. The gain KD is dimensionally equivalent to the inverse of a second (s⁻¹ < 0.001); it allows for adjusting the dynamics of this correction. In one embodiment, it is determined empirically to satisfy a compromise between stability and setpoint tracking accuracy.

[0075] The second correction, F2, aims to compensate for the time delay ΔT related to the filters implemented in the subsequent step E4, specifically within a feedback loop B1 between the second speed setpoint CV2 and an acceleration setpoint CA. The second correction, F2, is therefore determined by the implementation of the feedback loop B1, which we describe later in this document. The second correction, F2, will be described further on, following the description of the feedback loop B1.

[0076] Thus, the second speed setpoint CV2 is the sum of a first and a second speed component CV21, CV22, the first speed component CV21 being obtained by applying two phase-lead filters to the first speed setpoint CV1, and the second speed component CV22 being obtained by applying a gain KD to the distance error margin ΔD.

[0077] As a note, the KD gain is set so that the second velocity component CV22 converges to a stable value.

[0078] In one embodiment of step E3, step E3 may further include the processing of a third speed setpoint CV3 determined by the target tracking module 4.

[0079] This situation occurs when step E1 runs at a time when no target is detected by the target tracking module 4, then a target is detected during the implementation, in E2 to E4, of the regulation of the autonomous vehicle's speed with respect to the distance of the vehicle to the speed change point P.

[0080] When a target is detected, a third speed command CV3 is calculated by the target tracking module 4 to maintain a given tracking distance between the autonomous vehicle 100 and said target.

[0081] The target is preferentially detected in the traffic located in front of the autonomous vehicle 100. In this case, it is necessary that the speed command applied by autonomous vehicle 100 be lower than the CV3 speed command, so that the autonomous vehicle 100 respects the given following distance with the target.

[0082] Therefore, for safety reasons, an arbitration strategy is applied between the two speed commands, CV2 and CV3. According to this strategy, the second speed command CV2 must be limited to the third speed command CV3.

[0083] In other words, the value of the second speed setpoint CV2 is updated as the minimum between the second speed setpoint CV2 and the third speed setpoint CV3.

[0084] In an alternative or complementary embodiment of step E3, step E3 may further include the processing of a fourth speed instruction CV4 defined by the vehicle user via the human-machine interface.

[0085] An arbitration strategy is therefore applied between the two speed commands, CV2 and CV4. According to this strategy, the second speed command CV2 must be bounded by the fourth speed command CV4. If a third speed command CV3 is defined, the second speed command CV2 must also be bounded by the third speed command CV3.

[0086] In other words, the value of the second speed setpoint CV2 is updated as being the minimum between the second speed setpoint CV2, the fourth speed setpoint CV4 and the third speed setpoint CV3, if the third setpoint CV3 is defined, otherwise the minimum between the second speed setpoint CV2 and the fourth speed setpoint CV4.

[0087] We then proceed to step E4. In one implementation of step E4 represented by the figure 2 , we implement a control loop B1 between the second speed setpoint CV2 calculated in step E3 and an acceleration setpoint CA.

[0088] For example, the B1 control loop can implement speed regulation generating two acceleration components CA1, CA2: a first acceleration component CA1 of FeedForward type is obtained by applying a first order differentiator filter F3 to the second speed setpoint CV2, a second acceleration component CA2 of Feedback type is obtained by applying a proportional regulator of gain F43 to a speed error ΔV, calculated between a measured speed VM of the motor vehicle 100 and a filtered speed setpoint CVF, the acceleration setpoint CA being the sum of the first and second acceleration components, CA1, CA2.

[0089] The proportional controller F43 applies a multiplicative gain Kv to the velocity error ΔV. The gain Kv is dimensionally equivalent to the inverse of a second (s⁻¹ < 0.001); it allows for adjusting the dynamics of this correction. In one embodiment, it is determined empirically to satisfy a compromise between stability, speed, and setpoint tracking efficiency. In particular, the gain Kv is defined so that the second acceleration component CA2 converges to a stable value.

[0090] The filtered speed setpoint CVF is obtained by applying two successive first-order filters, F41 and F42, to the second speed setpoint CV2. The first filter, F41, synchronizes the second speed setpoint CV2 with the first acceleration component, CA1, of the FeedForward type. The second filter, F42, takes into account the system dynamics.

[0091] The respective transfer functions H3, H41, H42 of the filters F3, F41, F42 are expressed respectively according to the formulas Math 2. H 3 = s 1 + τ FF s H 41 = 1 1 + τ FF s H 42 = 1 1 + τ ModFF s Or s is the Laplace variable homogeneous to the inverse of a second (s -1< ), t FF is a first time constant, whose value is on the order of several tenths of a second, for example 0.4 seconds, and t ModFF is a second time constant, whose value is on the order of a tenth of a second, for example 0.15 seconds.

[0092] The relatively high value of the first time constant t FF This has the advantage of filtering out any sudden changes in the speed setpoint, thus improving user comfort. These sudden changes are mainly due to a discontinuity in the derivative of the time evolution of the speed setpoint.

[0093] Nevertheless, the high value of t FFresults in a significant delay between the calculation of the autonomous vehicle's speed setpoint 100 and the implementation of this speed setpoint by the powertrain and / or brake actuator.

[0094] As previously explained, in step E3 a second correction F2 is applied so that the delay introduced by loop B1 does not penalize the ability of autonomous vehicle 100 to reach a precise point on its route at a given speed.

[0095] The second F2 correction includes a first phase-lead filter F21 which compensates in advance for the delay introduced by filter F41 and, a second phase-lead filter F22 which compensates in advance for the delay introduced by filter F42.

[0096] The respective transfer functions H21 and H22 of the filters F21 and F22 are expressed respectively according to the formulas Math 3. H 21 = 1 + τ FF s 1 + τ f s H 22 = 1 + τ ModFF s 1 + τ f s Or s is the Laplace variable homogeneous to the inverse of a second (s -1< ), t FF is the first time constant also used in the F41 phase-delay filter, t ModFF is the second time constant also used in the F42 phase delay filter. t f is a third time constant whose value is on the order of 50 milliseconds

[0097] With filters F21 and F22 defined in this way, the phase delay between the first speed setpoint CV1 and the acceleration setpoint CA is limited to the delay induced by the third time constant. This delay is therefore minimized, since it is on the order of 50 milliseconds.

[0098] The acceleration setpoint CA thus determined is transmitted to the torque controller 7 in order to implement a longitudinal movement of the autonomous vehicle 100.

[0099] There figure 4 illustrates the effect of implementing the invention: Graphs G11, G12, G13, G14 and G15 illustrate the movement of the autonomous vehicle towards a speed change point P without implementation of the invention, and graphs G21, G22, G23, G24 and G25 illustrate the movement of the autonomous vehicle towards a speed change point P with implementation of the invention.

[0100] The x-axis of graphs G11 to G15 and graphs G21 to G25 represents time in seconds.

[0101] Graphs G11 and G21 allow us to compare the temporal evolution of the speed (represented in km / h on the ordinate axis of graphs G11 and G21) of the autonomous vehicle respectively without and with implementation of the invention: on graph G11, without implementation of the invention, the applied speed 112 is behind the speed setpoint 111 from the predictive speed profile PVP, on graph G21, with implementation of the invention, the applied speed 212 is substantially closer to the speed setpoint 211 from the predictive speed profile PVP.

[0102] Graphs G12 and G22 allow comparison of the temporal evolution of a component of the speed setpoint (represented in m / s on the ordinate axis of graphs G12 and G22) corresponding to a distance correction respectively without and with implementation of the invention: on graph G12, this component is zero since, without implementation of the invention, no speed correction is applied, on graph G22, with implementation of the invention, this component CV22 evolves between 0 m / s and -0.15 m / s.

[0103] Graphs G13 and G23 allow comparison of the temporal evolution of the acceleration of the autonomous vehicle (represented in m / s² on the ordinate axis of graphs G13 and G23) respectively without and with implementation of the invention: on graph G13, without implementation of the invention, between times t=16s and t=28s we observe a significant difference between the acceleration 132 applied by the vehicle and the acceleration setpoint 131 from the predictive speed profile PVP, on graph G23, with implementation of the invention, between times t=16s and t=28s we observe a reduction of the difference between the acceleration 232 applied by the vehicle and the acceleration setpoint 231 from the predictive speed profile PVP.

[0104] Similarly, graphs G14 and G24 allow comparison of the temporal evolution of the jerk of the autonomous vehicle (represented in m / s³ on the ordinate axis of graphs G14 and G24) respectively without and with implementation of the invention: on graph G14, without implementation of the invention, at time t=28s a significant difference is observed between the jerk 142 applied by the vehicle and the jerk 141 determined by the predictive speed profile PVP, on graph G24, with implementation of the invention, the difference observed at time t=28s between the jerk 242 applied by the vehicle and the jerk 241 determined by the predictive speed profile PVP is considerably reduced.

[0105] Furthermore, graphs G15 and G25 allow comparison of the temporal evolution, respectively without and with implementation of the invention, of a distance error (represented in meters on the ordinate axis of graphs G15 and G25) measured at a given instant between the actual position of the autonomous vehicle and the theoretical position determined by the predictive speed profile PVP: on graph G15, without implementation of the invention, the distance error 151 increases significantly over time until it exceeds 6 meters, on graph G25, with implementation of the invention, the distance error 251 remains less than fifteen centimeters over the entire duration of the journey and stabilizes around 6 centimeters when approaching the speed change point P.

[0106] Thanks to the invention, the speeds, accelerations, and jerks implemented by the autonomous vehicle 100 remain close to the values ​​defined by the predictive speed profile (PVP) during the vehicle's movement towards the speed change point (P). The phase and distance corrections provided by the invention allow the autonomous vehicle 100, firstly, to move along its route while minimizing the distance between its actual position and a theoretical position determined by a movement according to its PSP profile, and thus ensure, in particular, the comfort of the vehicle's users and secondly, to reach the speed change point P with a speed close to the limit speed VL, and with an accuracy on the order of ten or a few tens of centimeters relative to the position of the speed change point P, and thus to ensure the accuracy of stopping or changing speed.

[0107] A key feature of the invention is its ability to regulate not only the autonomous vehicle's speed over time, but also the distance between the autonomous vehicle and the speed change point over time. This regulation of the distance between the autonomous vehicle and the speed change point allows for the correction of any positional deviation resulting from a deviation in the vehicle's speed from the setpoint. This feature is a key difference between the invention and US patent 8924049B2, cited in the prior art section.

[0108] Furthermore, a switching strategy is implemented between regulating the speed of the autonomous vehicle according to the invention and regulating the speed of the autonomous vehicle according to the target tracking module 4. Indeed, the speed regulation accuracy requirements differ significantly depending on whether the goal is to maintain a tracking distance between a target vehicle and the autonomous vehicle 100, or to precisely reach a speed change position for the autonomous vehicle, particularly a stopping position. In the case of target tracking, the speed of the autonomous vehicle is regulated relative to the target's speed to maintain a tracking distance corresponding to a minimum time, for example, 2 seconds, separating the two vehicles. For example, if the vehicle is traveling at 90 km / h, a tracking distance equivalent to a 2-second separation is 50 meters.The actual distance maintained between the autonomous vehicle and the target can then vary between 45 and 55 meters without impacting safety. However, in the case of speed regulation based on the autonomous vehicle's speed change position, and more specifically based on the autonomous vehicle's stopping position, the expected accuracy of the vehicle's position relative to the speed change point P is on the order of ten centimeters. Similarly, the target tracking speed can fluctuate slightly around a set tracking speed without affecting the maintenance of a safe distance between the two vehicles.On the other hand, in the case of speed regulation based on a stopping position of the autonomous vehicle, it is not acceptable for the vehicle speed to oscillate around 0 m / s when reaching the stopping point, because such oscillations mean that the vehicle moves forward and backward when it arrives at the stopping point.

[0109] In other words, the position and speed accuracy provided by the invention is very advantageous in the case where it is desired that the autonomous vehicle stop at a precise point (for example in front of a stop sign), but such accuracy is not required for target tracking.

[0110] On the contrary, the speed control according to the invention can generate discomfort if applied to a speed profile generated by the target tracking module 4. Indeed, a speed profile generated by the target tracking module may exhibit a discontinuous derivative, the discontinuities of which are filtered by the application of filters whose effect would be negated by the implementation of the invention. In other words, if speed control according to the invention were applied to a speed profile generated by the target tracking module, it would degrade the comfort of target tracking; in particular, the vehicle's speed would be jerky.

[0111] The switching strategy therefore consists of implementing the cruise control best suited to the current situation, which could be target following or a speed change at a precise position: in the case of speed regulation with respect to a change of speed at a precise position, the speed regulation will include the application of corrective filters (in step E3) upstream of a servo loop B1 between speed and acceleration (implemented in step E4), in the case of speed regulation with respect to target tracking, the speed regulation will include only the servo loop B1 between speed and acceleration (implemented in step E4).

[0112] Furthermore, situations where a target appears while speed regulation according to the invention is in progress are also addressed. In this case, a speed setpoint is determined by the target tracking module 4 while speed regulation based on a predictive speed profile is in progress. An arbitration strategy is then applied; it consists of determining the speed setpoint as the minimum between the second speed setpoint CV2 from the predictive speed profile and the third speed setpoint CV3 from the tracking module 4. This ensures that the target tracking distance is maintained in all cases; in cases where the second speed setpoint CV2 is lower than the target tracking speed setpoint, speed regulation according to the invention is maintained, i.e., speed regulation relative to a speed change point.

[0113] More generally, the arbitration strategy implemented in the invention consists of determining the speed setpoint as the minimum among the different defined speed setpoints: the CV4 setpoint from the human-machine interface 5, a possible CV3 setpoint from the target tracking module 4, and the CV2 speed setpoint from the predictive speed profile. In this way, it is ensured that the speed setpoint applied to the autonomous vehicle does not exceed the speed defined by the user and allows for maintaining a minimum tracking distance from a potential target.

Claims

1. Method for managing the longitudinal speed of a motor vehicle (100), the motor vehicle travelling on a planned trajectory (T), the motor vehicle being equipped with at least one detection means (1) for detecting the environment of the vehicle and with an odometry means (2), characterized in that it comprises - a step (E1) of detecting, based on data from the at least one detection means (1), a speed change point (P) located on the given trajectory (T) and ahead of the motor vehicle, and of determining a limit speed (VL) applicable at the speed change point (P), and then - a second step (E2) of computing a first speed setpoint (CV1) for the motor vehicle (100), as a function of the limit speed (VL) and of a first distance (DT) separating the motor vehicle (100) from the speed change point (P), the first distance (DT) being computed as a function of a planned speed profile (PVP), the first distance (DT) having a distance margin of error (ΔD) with respect to a second distance (DM) determined by the odometry means (2) between the motor vehicle (100) and the speed change point (P), and then - a third step (E3) comprising determining a second speed setpoint (CV2) that compensates for the distance margin of error (ΔD) generated in the second step (E2) and that anticipates a phase delay (ΔT) generated in a fourth step (E4) of controlling the movement of the motor vehicle (100), and then - a fourth step (E4) of controlling the movement of the motor vehicle (100) in accordance with the second speed setpoint (CV2) so as to reach the speed change point (P) with a speed equal to the limit speed (VL), the fourth step (E4) generating the phase delay (ΔT) between the reception of the second speed setpoint (CV2) and the movement of the vehicle in accordance with the second speed setpoint (CV2).

2. Management method according to the preceding claim, the motor vehicle (100) being equipped with a measuring means (3) for measuring the instantaneous speed of the vehicle, characterized in that the fourth step (E4) comprises determining an acceleration setpoint (CA) for the motor vehicle as being the sum of a first and a second acceleration component (CA1, CA2), - the first acceleration component (CA1) being computed by applying a first-degree differential filter (F3) to the second speed setpoint (CV2), and - the second acceleration component (CA2) being obtained by applying a first proportional gain controller (KV) to the difference between an instantaneous speed (VM) of the vehicle determined by the speed measuring means (3) and a filtered speed setpoint (CVF), the filtered speed setpoint (CVF) being obtained by successively applying a first and a second first-order filter (F41, F42) to the second speed setpoint (CV2), - the first filter (F41) applying a phase delay to the second speed setpoint (CV2) so as to synchronize the second speed setpoint (CV2) with the first acceleration component (CA1), and - the second filter (F42) being parameterized such that the filtered speed setpoint (CVF) converges on a stable value.

3. Management method according to either of the preceding claims, characterized in that the second speed setpoint (CV2) is the sum of a first and a second speed component (CV21, CV22), - the first speed component (CV21) being obtained by applying a first and a second phase advance filter (F21, F22) to the first speed setpoint (CV1), and - the second speed component (CV22) being obtained by applying a second proportional controller comprising a given gain (KD) to the distance margin of error (ΔD), the given gain being regulated so that the second speed component (CV22) converges on a stable value.

4. Management method according to Claims 2 and 3, characterized in that: - the same time constant (τFF) is used to define the first phase advance filter (F21) applied to compute the second speed setpoint (CV2), the first-degree differential filter (F3) and the first phase delay filter (F41) applied to compute the acceleration setpoint (CA), and in that - the same time constant (τModFF) is used to define the second phase advance filter (F22) applied to compute the second speed setpoint (CV2), and the second phase delay filter (F42) applied to compute the acceleration setpoint (CA).

5. Management method according to one of the preceding claims, the vehicle comprising a human-machine interface (5) allowing a user to define a fourth speed setpoint (CV4), characterized in that the third step (E3) comprises modifying the second speed setpoint (CV2) as being the minimum out of the second speed setpoint (CV2) and the fourth speed setpoint (CV4).

6. Management method according to the preceding claim, the vehicle comprising a target following module (4) that determines a third speed setpoint (CV3), characterized in that the third step (E3) comprises modifying the second speed setpoint (CV2) as being the minimum out of the second speed setpoint (CV2), the third speed setpoint (CV3) and the fourth speed setpoint (CV4).

7. Management method according to one of the preceding claims, characterized in that the limit speed (VL) is zero.

8. Computer program product comprising program code instructions recorded on a computer-readable medium implementing the steps of the method according to any one of Claims 1 to 7 when said program runs on a computer.