ADAPTIVE FILTERING OF THE SPEED OF A TARGET VEHICLE FOR ADAPTIVE CRUISE CONTROL OF THE HOST VEHICLE

Description

[0001] The present invention relates to devices for assisting in driving a motor vehicle, and more particularly to adaptive cruise control systems and motor vehicles equipped with such devices.

[0002] An adaptive cruise control (better known as "Adaptive Cruise Control" or ACC) automatically adjusts the speed of the carrier vehicle based on a reference speed and a reference inter-vehicle distance (or, equivalently, an inter-vehicle time) between the carrier vehicle and the vehicle in front of it on the same traffic lane used as a target vehicle. Thus, in the presence of a target vehicle, the speed regulation of the carrier vehicle is directly linked to the speed of the target vehicle. The adaptive cruise control, in fact, faithfully reproduces all variations in the speed of the target vehicle as long as it is lower than the reference speed of the carrier vehicle.

[0003] As a result, slight oscillations in the speed of the target vehicle (especially when it is in manual driving) also significantly generate these same oscillations in the speed of the carrier vehicle. A major disadvantage of such behavior of the adaptive cruise control is that it degrades the dynamic comfort of the carrier vehicle. The driver of the carrier vehicle does not really notice the slight slowdowns / accelerations of the target vehicle, but clearly feels those of his vehicle.

[0004] Furthermore, the state of the art is known from documents US2019 / 143971A1 and DE102018004027 A1.

[0005] An object of the present invention is to at least partially overcome the aforementioned drawbacks.

[0006] To this end, there is proposed, firstly, an adaptive cruise control for regulating the speed of a first motor vehicle, this adaptive cruise control being capable of determining the speed of a second motor vehicle traveling in front of the first motor vehicle on the same traffic lane and in the same direction of travel, the adaptive cruise control comprising a computer configured to calculating the gradient of the difference between the speed of the second motor vehicle and the speed of the first motor vehicle; smoothing the determined speed of the second motor vehicle with a smoothing coefficient associated with the calculated gradient, the adaptive cruise control being configured to regulate the speed of the first motor vehicle relative to the smoothed speed.

[0007] Secondly, a method for adaptively regulating the speed of a first motor vehicle is proposed, comprising the following steps: determining the speed of a second motor vehicle traveling in front of the first motor vehicle on the same traffic lane and in the same direction of travel; calculating the gradient of the difference between the speed of the second motor vehicle and the speed of the first motor vehicle; smoothing the determined speed of the second motor vehicle with a smoothing coefficient associated with the calculated gradient; regulating the speed of the first motor vehicle in relation to the smoothed speed.

[0008] Various additional features may be provided, alone or in combination: the smoothing coefficient is decreasing as a function of said gradient so that a smoothing associated with a gradient lower in absolute value than a first threshold value is greater than a smoothing associated with a gradient higher in absolute value than said first threshold value; when the calculated gradient is higher in absolute value than a second predefined threshold value, the smoothing coefficient is chosen so that the smoothed speed is substantially equal to the determined speed of the second motor vehicle; the smoothing coefficient is defined by a predefined affine function by interval of said gradient; the calculator is configured to smooth the determined speed of the second motor vehicle by a gradient limiter.

[0009] Thirdly, a motor vehicle is proposed including the adaptive cruise control presented above.

[0010] Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is given with reference to figure [ Fig.1 ] which schematically illustrates a motor vehicle provided with an adaptive cruise control according to various embodiments.

[0011] Referring to the figure 1 , adaptive cruise control is displayed 2 equipping a first vehicle 1 automobile (also called vehicle 1 carrier, host vehicle or ego-vehicle).

[0012] This adaptive cruise control 2 is able to detect the speed of a second vehicle 3 automobile (vehicle 3 target) circulating in front of the first vehicle 1 car on the same lane 4 of traffic and in the same direction 5of traffic. For this, the adaptive cruise control 2 includes a sensor (including, but not limited to, radar, camera, laser, or forward-looking lidar, or a vehicle-to-vehicle communication module) capable of detecting the presence of the vehicle 3 target and to determine the inter-vehicle distance and the speed of that vehicle 3 target.

[0013] In order to limit the impact of low magnitude oscillations / fluctuations in vehicle speed 3 target on longitudinal vehicle speed regulation 1 carrier, adaptive cruise control 2 includes a computer configured to perform adaptive filtering based on vehicle dynamics 3 target. This adaptive filtering aims to attenuate small oscillations in vehicle speed 3 target so that they are not taken into account by the adaptive cruise control2 in its regulation of the speed of the carrier vehicle. The speed of the vehicle 1 carrier is thus controlled by the filtered speed of the vehicle 3 target.

[0014] For this, the adaptive cruise control calculator 2 is configured for calculate the gradient of the vehicle's relative speed 3 target relative to the carrier vehicle 1, this relative speed being the difference between the speed of the vehicle 3 target is the vehicle speed 1 carrier; smooth the vehicle speed 3 target with a smoothing coefficient (i.e. a filtering level or an attenuation rate) associated with the gradient of the relative velocity.

[0015] The adaptive cruise control calculator 2 filters, in fact, the speed of the vehicle 3target as a function of the gradient of its relative speed. The gradient here refers to the rate of change per unit time of the relative speed of the vehicle 3 target. In one embodiment, the computer applies a smoothing filter (or a smoothing filter) or any other smoothing operator or function allowing the vehicle speed to be smoothed (smoothed or reduced in variations) 3 target with a predefined smoothing coefficient. This smoothing filter is, for example, a gradient limiter (better known as a gradient limiter or rate limiter). Adaptive cruise control 2 is configured to regulate the vehicle speed 1 carrier relative to the smoothed vehicle speed 3 target.

[0016] The smoothing coefficient is associated with the gradient of the relative speed of the vehicle 3target so as to adapt to the values ​​of the oscillations to be eliminated / filtered. In one embodiment, the smoothing coefficient is decreasing as a function of the gradient of the relative speed so that a smoothing associated with a gradient lower in absolute value than a first threshold value is greater (i.e. greater) than a smoothing associated with a gradient higher in absolute value than this first threshold value. The computer filters the speed of the vehicle 3 target by a smoothing filter dependent on the gradient of the relative velocity so that the smoothing is strong for weak gradients and weak (or even non-existent or zero) for strong gradients.

[0017] The smoothing coefficient is a function of the gradient of the relative speed so that to filter out vehicle speed fluctuations as much as possible 3target when the gradient of its relative speed is low, i.e. lower in absolute value than a first predefined threshold value (for example, a rate of variation or a gradient between 0 km / h and 4 km / h in absolute value). Such filtering advantageously improves the dynamic comfort of the vehicle 1 carrier; so that the smoothed speed is, when the gradient of the relative speed is greater in absolute value than a second predefined threshold value (for example, a rate of variation beyond 10 km / h), substantially equal to the determined speed of the vehicle 3 target (unsmoothed). In other words, the smoothing coefficient is chosen, when the gradient of the relative speed is estimated to be significant, so as to inhibit the filtering of the vehicle speed 3 target. This advantageously allows the responsiveness of the adaptive cruise control to be preserved 2 compared to a dynamic vehicle situation3 target translated by a significant gradient of its relative speed (for example, when the vehicle 3 target brakes).

[0018] In another embodiment, the adaptive cruise control computer 2 is configured to modulate the smoothing coefficient (or filtering level) of the vehicle speed 3 target as a function of the interval of the gradient of the relative speed (for example, a gradient comprised in absolute value between 0 and 4 km / h, between 4 and 10 km / h or greater than 10 km / h). More generally, the smoothing coefficient is, in one embodiment, defined by an affine function by interval of the gradient of the relative speed.

[0019] As associated with the gradient of the relative speed, the smoothing coefficient advantageously makes the adaptive cruise control 2 less responsive to small oscillations in vehicle speed 3target in order to gain comfort in the vehicle 1 carrier, without however degrading its responsiveness to dynamic vehicle situations 3 target.

Claims

1. An adaptive speed regulator (2) for regulating the speed of a first motor vehicle (1), this adaptive speed regulator (2) being capable of determining the speed of a second motor vehicle (3) traveling in front of the first motor vehicle (1) on the same road (4) and in the same direction (5) of travel, the adaptive speed regulator (2) being characterized in that it comprises a computer configured to - calculate the gradient of the difference between the speed of the second motor vehicle (3) and the speed of the first motor vehicle (1); - smoothing the determined speed of the second motor vehicle (3) with a smoothing coefficient associated with the calculated gradient, the adaptive speed regulator (2) being configured to regulate the speed of the first motor vehicle (1) by report with the smoothed speed.

2. Adaptive cruise control (2) according to the previous claim, wherein the smoothing coefficient is decreasing as a function of said gradient so that a smoothing associated with a lower absolute value gradient than a first threshold value is greater than a smoothing associated with a higher absolute value gradient than said first threshold value.

3. Adaptive cruise control (2) according to claim 1 or 2, wherein, when the calculated gradient is greater in absolute value than a second predefined threshold value, the smoothing coefficient is chosen so that the smoothed speed is substantially equal to the determined speed of the second motor vehicle (3).

4. Adaptive cruise control (2) according to any one of the previous claims, wherein the smoothing coefficient is defined by an affine function per predefined interval of said gradient.

5. Adaptive cruise control (2) according to any one of the previous claims, wherein the computer is configured to smooth the determined speed of the second motor vehicle (3) by a gradient limiter.

6. Method for adaptively regulating the speed of a first motor vehicle (1) comprising the following steps: - determining the speed of a second motor vehicle (3) traveling in front of the first motor vehicle (1) on a same road (4) and in a same direction (5) of traffic; - compute of the gradient of the difference between the speed of the second motor vehicle (3) and the speed of the first motor vehicle (1); - smoothing of the determined speed of the second motor vehicle (3) with a smoothing coefficient associated with the calculated gradient; - regulation of the speed of the first motor vehicle (1) by report to the smoothed speed.

7. The method according to the previous claim, wherein the smoothing coefficient is decreasing as a function of said gradient so that a smoothing associated with a gradient lower in absolute value than a first threshold value is higher than a smoothing associated with a gradient higher in absolute value than said first threshold value.

8. Method according to claim 6 or 7, wherein, when the gradient is greater than a second predefined threshold value, the smoothing coefficient is chosen so that the smoothed speed is substantially equal to the determined speed of the second motor vehicle (3).

9. Method according to any one of claims 6 to 8, characterized in that the smoothing coefficient is defined by an affine function per predefined interval of the said gradient.

10. Motor vehicle (1) comprising an adaptive cruise control (2) according to any one of claims 1 to 5.