FR3112745A1 - Method for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle - Google Patents

Abstract

Method for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle The invention relates to a method (100) for assisting the driver for an autonomous vehicle when passing a bend located in front of the vehicle, comprising the following steps: determining a route and an entry point of the bend located in front of the vehicle, the definition of the bend entry point being carried out according to the determined bend route as well as a current proper speed and/or a current acceleration of the autonomous vehicle (101); determining a maximum authorized limit speed profile along the curve path (102); comparison between a predictable actual own speed and the maximum authorized limit speed profile along the curve profile (103), an adjustment to the determined prescribed own speed of the autonomous vehicle being carried out independently of the driver, from the point of defined turn entry, if the predicted actual airspeed exceeds a specified threshold speed value (104). Figure for the abstract: Figure 2

Description

Method for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle

The invention relates to a method and a device for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle.

Modern motor vehicles are often equipped with driving dynamics control systems, such as ESC (Electronic Stability Control), which can specifically influence the behavior of a motor vehicle. In this case, in order to maintain driving stability, i.e. to ensure that the vehicle obeys the driver's instructions, automatic braking forces can be generated for each wheel and/or the driving torque can be reduced. Control intervention is derived directly from driver instructions (steering, braking, accelerating) and is carried out in a reactive manner, with Driving Dynamics Control intervention taking place only when behavior deviates from a desired of the driver with a measurable value, calculated using a vehicle model. A driving dynamics control system is disclosed by patent EP 0 792 229 B1, for example.

Currently, approaches for early driver warning of potentially dangerous cornering situations are being investigated. Using digital maps, information about a bend in front of the vehicle is determined, such as the geometric characteristic, for example. In this case, the vehicle's own position ("ego" position) is determined solely using satellite navigation (GPS: Global Positioning System) or in association with inertial sensors or inertial navigation by a electronic control unit (IPC: Inertial and Position Cluster). This type of CSW systems warn the driver when approaching a curve at too high a speed.

When the vehicle speed significantly exceeds the speed limit, in particular, the driver may react too late and/or with hesitation. In this context, driver assistance or stabilization functions are known, such as the PreviewESC (ESC = electronic stability control), for example, which carry out driver-independent braking interventions and/or a torque reduction of training for decreasing movement speed. A method for improving the driving stability of a motor vehicle is for example disclosed by the patent DE102012212616A1, by which braking interventions independent of the driver are triggered when a critical driving situation is foreseeable, at the using route information and current vehicle position data. The momentary travel speed is reduced to the limit speed by carrying out braking interventions on two or more wheels of the motor vehicle and/or by reducing the drive torque. According to one embodiment, the braking forces applied are chosen according to the difference between the momentary travel speed and the limit speed and/or the distance to the point of the route with a minimum turn radius. This allows fast driving and avoids braking interventions with inappropriate force.

The system adapting by speed to the absolute turn radius has the disadvantage of a static and rigid control when passing through the turn so that it can happen that an intervention occurs too early or too late. In particular, when braking too late, the longitudinal force that can be reduced can be limited too strongly due to the existing lateral dynamics and therefore lead to destabilization of the vehicle. In addition, rigid control gives the feeling of arbitrary vehicle guidance to the driver. On the contrary, the driver wants safety-oriented vehicle guidance that is otherwise smooth and understandable.

The object of the invention is therefore to propose a method and a device which provide the driver of the vehicle with an improved feeling of driving during assistance during the passage of a bend located in front of the vehicle.

In accordance with the invention, this objective is achieved by a method for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle, comprising the following steps:

- Determination of a route and an entry point of the bend located in front of the vehicle, the definition of the bend entry point being carried out according to the determined bend route as well as a current own speed and/or a current acceleration of the autonomous vehicle,

- Determination of a profile of the maximum authorized speed limit along the bend path;

- Comparison between a foreseeable actual own speed and the maximum authorized limit speed profile along the curve profile, an adjustment to the determined prescribed own speed of the autonomous vehicle being carried out independently of the driver, from the entry point of defined turn, if the predicted actual airspeed exceeds a specified threshold speed value.

The object is also achieved by a computer program product for guiding an autonomous vehicle, the computer program product comprising instructions, which when executed on a control device or on a computer of the autonomous vehicle execute the process as defined above.

The objective is also achieved by a driver assistance device for an autonomous vehicle when passing a bend located in front of the vehicle, comprising

a processing facility for determining a route and an entry point of the bend located in front of the vehicle, the processing facility being formed to determine the entry point of the bend based on the determined bend route as well as a current own speed and/or a current acceleration of the autonomous vehicle;

the processing facility being trained to determine a maximum permitted speed limit profile along the bend path; and

the processing installation being trained in order to compare between them an actual predictable airspeed and the maximum speed limit authorized along the curve path;

with a control facility, which is formed to set the speed of the autonomous vehicle to a prescribed airspeed, from the determined turn entry point, if the predicted actual airspeed exceeds a specified threshold speed value.

The objective is also achieved by a vehicle with a device as defined above.

Preferred or advantageous embodiments of the invention are disclosed in the present text and by the figures.

A driver assistance method is proposed for an autonomous vehicle when passing a bend located in front of the vehicle. The method comprises the following steps: determining a route, that is to say a curvature profile, and an entry point of the bend located in front of the vehicle. The definition of the turn entry point is performed at least based on the determined turn path as well as a current self-speed and/or a current acceleration of the autonomous vehicle. In this context, the notion of acceleration also covers a negative acceleration of the autonomous vehicle. The current proper speed or the current acceleration represents in particular at least one detected value, for example in a determined time range or at a defined instant of the imminent entry of the autonomous vehicle into the bend. The time range or the instant can be determined in particular by a duration or by a distance to the bend located in front of the vehicle, for example to a determined apex of the bend.

Furthermore, a maximum authorized limit speed profile along the curve path is determined. The maximum authorized speed limit profile represents in particular the maximum possible speed or the maximum possible speeds of the autonomous vehicle along the curve profile, the exceeding of which could result in the autonomous vehicle skidding by oversteering or understeering.

A comparison is made between a predictable actual airspeed and the maximum allowable limit speed profile along the turn profile, particularly at least at the apex of the turn. The predicted actual airspeed is determined using an extrapolation of the self-driving vehicle airspeed detected at the instant of imminent entry, for example.

Furthermore, if the actual foreseeable own speed exceeds at least one, or precisely one, specified threshold speed value, an adjustment to a prescribed own speed of the determined autonomous vehicle is carried out independently of the driver, in particular a braking intervention, from the defined turn entry point. The prescribed airspeed is in particular one or more speed values defined along the curve path, with which the curve can be passed safely, thus being lower than the maximum authorized limit speed profile, therefore guaranteeing the maintenance of the maneuverability and directional stability. The at least one, or precisely one, specified threshold speed value may for example be a minimum value of the determined maximum authorized limit speed profile. The prescribed airspeed is determined, for example, by means of the curve path and a vehicle model.

A static, i.e. fixedly specified, turn entry point is not given by defining the turn entry point as a function of the determined turn path as well as the current airspeed or current acceleration, but is also determined by the prevailing vehicle dynamics of the autonomous vehicle prior to corner entry. In this way, the turn entry point may shift rearward in the path for a slower moving vehicle, while it shifts forward for a comparatively faster moving vehicle in the same turn. This results in smooth vehicle control, and therefore the feeling for vehicle occupants of comfortable, dynamic and comprehensible vehicle control, which is an essential benefit. Simultaneously, a corner entry point is determined by the correlation between the own speed and the corner path, which corner entry point allows a braking intervention adapted to the current traffic situation and consequently a driving stability. frequently improved compared to emergency braking in the event of excessive speed.

According to a preferred embodiment, a reference own speed of the autonomous vehicle is determined for a time range of passage of the bend route, with a view to defining the bend entry point. The reference airspeed is determined in particular by means of an empirically determined factor, which is multiplied by the actual airspeed foreseeable along the turn path. The speed limit profile is preferably determined with the aid of a determined curve path of the curve in front of the vehicle. Furthermore, provision is made in particular for a low point in the speed limit profile to be considered as a critical turning point. The critical turning point can be for example the apex and/or the greatest curvature of the turn. The waypoint (waypoint or personal point) of the speed limit profile for which a first negative overshoot of the reference airspeed between the start of the turn and the critical turn point occurs is defined in particular as the entry point of turn. The turn entry point is thus defined efficiently and reliably.

According to another preferred embodiment, a maximum possible deceleration to a detected critical turn point is determined, the turn entry point being defined as the waypoint (waypoint or personal point) corresponding essentially to the path of the determined maximum possible deceleration to the detected critical turn point. Within the meaning of the invention, the expression "essentially" means a deviation of a respective exact value of +/- 10%, preferably of +/- 5% and/or deviations in the form of negligible modifications for the function. The maximum possible deceleration path for the definition of the corner entry point can optionally be supplemented by a section, which offers additional robustness, to guarantee pleasant behavior for the driver also in the event of inaccuracies or deviations unexpected, for example. This embodiment also has the advantageous possibility of adapting the corner entry point as precisely as possible to the current traffic and vehicle dynamics conditions.

The speed limit profile for passing the bend is preferably determined on the basis of a specified lateral acceleration and the determined bend path of the bend in front of the vehicle. The specified transverse acceleration is determined by means of a mathematical model, for example.

For the determination of the specified transverse acceleration, a coefficient of friction is determined between a tire of the autonomous vehicle and the road surface, in particular. The determination of the coefficient of friction is carried out for example by means of a coefficient of friction estimator of the autonomous vehicle, that is to say in an on-board manner, alternatively or, optionally in a complementary manner, by a V2X communication device , therefore in particular by a cloud, which provides for example a map of friction coefficients.

As an exemplary alternative, the coefficient of friction is specified by a uniquely defined value, which also guarantees safe cornering in bad weather conditions. A preferred embodiment provides that the coefficient of friction is determined for example by the driver of the autonomous vehicle, using an input on a man-machine interface, known under the name of HMI. Particularly preferably, the coefficient of friction is determined by a selection of a driving mode made by the driver. Different transverse accelerations and therefore different coefficients of friction result from the selected driving mode. When selecting a comfort mode, for example, a lower lateral acceleration is desired than when selecting a sport mode. Furthermore, it is conceivable that an analysis device of the autonomous vehicle analyzes specific road or weather conditions, to which a corresponding coefficient of friction is assigned. The analysis device is formed, for example, to carry out the analysis of current road conditions and the determination of the coefficient of friction associated therewith by means of camera images from an in-vehicle camera device, by means of an activated windshield wiper or by other direct or indirect input by the driver of the vehicle. In this way, the specified transverse acceleration can be adapted to the current road conditions.

In accordance with a preferred embodiment, the course of the turn in front of the vehicle is determined using digital map material and/or using camera data from the autonomous vehicle's internal camera device.

Another object of the invention relates to a computer program product for guiding an autonomous vehicle, the computer program product comprising instructions, which, when executed on a control device or on a computer of the autonomous vehicle carry out the method according to the preceding description.

Another object of the invention relates to a device, in particular a driver assistance or stability device for assisting the driver for an autonomous vehicle when passing a bend located in front of the vehicle, comprising a processing installation for determining a route and an entry point of the bend located in front of the vehicle, the processing installation being formed in order to determine the entry point of the bend according to the determined bend route as well as a current self-speed and/or a current acceleration of the autonomous vehicle, the processing facility being trained to determine a maximum allowable limit speed profile along the turn path, and the processing facility being trained to compare between them a foreseeable actual airspeed and the maximum limit speed authorized along the course of the bend. The device includes a control facility, which is formed to adjust the speed of the autonomous vehicle to a prescribed self-speed independently of the driver, from the determined turn entry point, if the predicted actual self-speed exceeds a value specified threshold speed. The device is thus formed in particular in order to assist the driver preferably by braking intervention, before the autonomous vehicle can find itself in a situation of critical driving stability due to excessive speed.

Another object of the invention relates to a vehicle with a device according to the previous description.

In the following, the invention is described in more detail with the aid of suitable embodiment examples. The figures show:

a simplified schematic representation of a flowchart of the method according to the invention;

a turn plot having exemplary value, on the upper diagram, and a first exemplary embodiment of the determination of the corresponding turn entry point, on the lower diagram;

FIGS. 3-5 an exemplary turn layout, on the upper diagram, and a second example embodiment of the determination of the turn entry point, on the lower diagram.

The illustrates a simplified flowchart of the method 100 in accordance with the invention for assisting the driver of an autonomous vehicle when taking a bend located in front of the vehicle, with the following steps: determining a route and a entry point of the bend located in front of the vehicle, the definition of the bend entry point being carried out according to the determined bend route as well as a current own speed and/or a current acceleration of the autonomous vehicle 101. A maximum allowable limit speed profile along the turn pattern is determined 102. In the next step, a comparison is made between a predictable actual airspeed and the maximum allowable limit speed profile along the turn profile 103 , an adjustment to the determined prescribed own speed of the autonomous vehicle being carried out independently of the driver, from the defined turn entry point, if the foreseeable actual own speed exceeds a value specified threshold speed ur 104.

A first exemplary embodiment for determining the turn entry point is illustrated by means of a simplified diagram, on the . The shows by way of example a first diagram on which a plot of a bend to be passed by an autonomous vehicle is represented. The critical point is the most significant curvature of the bend. On the second diagram, located below, the limiting speed profile along the turn path and the predicted actual airspeed are shown, purely by way of example. The limit speed profile is for example determined using the determined bend route of the bend located in front of the vehicle, a low point in the limit speed profile being considered as a critical bend point. A reference natural speed of the autonomous vehicle is determined for a time range of passage of the bend route, for the definition of the bend entry point. The reference airspeed is determined using an empirically determined k-factor, which is multiplied by the actual airspeed predicted along the turn path. By multiplying the actual predictable own speed by the empirically determined factor k, it is guaranteed in particular that the autonomous vehicle is stable at the point of intersection of the curve path.

The waypoint (waypoint or personal point) of the speed limit profile for which a first undershoot of the reference airspeed between the start of the turn and the critical turn point occurs, indicated here by the point of intersection of the line plots of the limit speed and the reference speed, is defined as the turn entry point. The method according to the invention promotes a regular and controlled braking intervention force when going through the bend.

A second exemplary embodiment for determining the turn entry point is also illustrated by means of a simplified diagram, in FIGS. 3 to 5. shows a turn plot in a first diagram, as an example. In the second diagram of Figures 3 to 5, located below, the limiting speed profile along the turn path, the predicted actual airspeed and an airspeed profile at a maximum auto deceleration that can be reduced are shown. In this way, a maximum possible deceleration to a detected critical turning point can be determined, by means of a mathematical model, for example. The turn entry point is in particular defined as the waypoint (waypoint or personal point) essentially corresponding to the route of the determined maximum possible deceleration up to the detected critical turning point. Another safety path on this path can be taken into account as an option, in a complementary way, if a more moderate control is desired.

Due to the dominant transverse dynamics, only a given deceleration can be reduced, as shown by way of example in Figures 3 to 5 by the different eigenspeed profiles for a maximum automatic deceleration that can be reduced.

The maximum automatic deceleration that can be reduced can be limited by two different factors. On the one hand, by the design of the function, for example by a specified deceleration of less than 2.5 m/s2, as shown in figures 3 and 4. On the other hand, by the physical values of the dynamics of driving, as illustrated by the . In the latter case, this means that the smaller the difference between the predicted actual airspeed and the limiting speed, the smaller the circle of Kamm, which represents the idealized ratios between the longitudinal and lateral forces on the wheel of a vehicle, is exhausted, and therefore, the lower the deceleration that can be deducted.

Claims (10)

Method (100) for assisting the driver of an autonomous vehicle when passing a bend located in front of the vehicle, comprising the following steps:
- Determination of a route and an entry point of the bend located in front of the vehicle, the definition of the bend entry point being carried out according to the determined bend route as well as a current own speed and/or a current acceleration of the autonomous vehicle (101),
- Determination of a maximum authorized limit speed profile along the curve route (102);
- Comparison between a foreseeable actual own speed and the maximum authorized limit speed profile along the curve profile (103), an adjustment to the determined prescribed own speed of the autonomous vehicle being carried out independently of the driver, from the point of entering a defined turn, if the predicted actual airspeed exceeds a specified threshold speed value (104). Method according to claim 1, a reference own speed of the autonomous vehicle being determined for a time range of passage of the bend route, the limit speed profile being determined using a determined bend route of the bend located in front of the vehicle, a low point on the speed limit profile being considered as a critical turning point, and a waypoint of the speed limit profile for which a first exceeding of the reference airspeed between the start of the turn and the turning point critical occurs being defined as turn entry point. A method according to claim 1, wherein a maximum possible acceleration to a detected critical turn point is determined, the turn entry point being defined as the waypoint substantially corresponding to the path of the determined maximum possible acceleration to the critical turn point detected. Method according to one of the preceding claims, the limit speed profile for passing the bend being determined on the basis of a specified lateral acceleration and the determined bend path of the bend in front of the vehicle. A method according to claim 4, a coefficient of friction being determined for the determination of the specified transverse acceleration, the determination of the coefficient of friction being carried out by means of a coefficient of friction estimator or by an input by the driver, on a Human Machine Interface. Method according to claim 5, the coefficient of friction being determined by a selection of a driving mode made by the driver. Method according to one of the preceding claims, the course of the bend in front of the vehicle being determined by means of digital map material and/or by means of camera data. A computer program product for guiding an autonomous vehicle, the computer program product comprising instructions, which when executed on a control device or on a computer of the autonomous vehicle carry out the method (100) according to one of the preceding claims. Driver assistance device for an autonomous vehicle when passing a bend located in front of the vehicle, comprising
a processing facility for determining a route and an entry point of the bend located in front of the vehicle, the processing facility being formed to determine the entry point of the bend based on the determined bend route as well as a current own speed and/or a current acceleration of the autonomous vehicle;
the processing facility being trained to determine a maximum allowable limit speed profile along the turn path; and
the processing installation being formed in order to compare between them a foreseeable actual proper speed and the maximum limit speed authorized along the curve route;
with a control facility, which is formed to set the speed of the autonomous vehicle to a prescribed airspeed, from the determined corner entry point, if the predicted actual airspeed exceeds a specified threshold speed value. Vehicle with a device according to claim 9.