METHOD FOR ADAPTING A BRAKING DECELERATION FOR A MOTOR VEHICLE

Abstract

A method for adapting a braking deceleration for a vehicle comprising a system for avoiding collisions, including an associated traffic sensor system and a force sensor system. An optimal braking deceleration is ascertained for the evasive maneuver. A current driving velocity of the motor vehicle is ascertained, and a value of a transverse acceleration of the motor vehicle is ascertained via the force sensor system. A setpoint value of a transverse acceleration-dependent braking deceleration is determined based on the value of the transverse acceleration. A velocity-dependent braking deceleration is determined based on the driving velocity. The optimal braking deceleration is ascertained based on the setpoint value of the transverse acceleration-dependent braking deceleration and the setpoint value of the velocity dependent braking deceleration such that the optimal braking deceleration has, as a mathematical function of the variables driving velocity and transverse acceleration, an opposite monotonicity with respect to these variables.

Claims

1. A method for adapting a braking deceleration for a motor vehicle, the motor vehicle comprising an emergency system for avoiding collisions, an associated traffic sensor system for capturing a traffic situation and a force sensor system for capturing forces acting in each case upon the motor vehicle and/or upon individual axles and/or wheels, the method comprising: initiating an evasive maneuver in response to a critical driving situation captured by the emergency system; ascertaining an optimal braking deceleration for the evasive maneuver; ascertaining a current driving velocity of the motor vehicle; ascertaining a value of a transverse acceleration of the motor vehicle via the force sensor system; determining a setpoint value of a transverse acceleration-dependent braking deceleration based on of the value of the transverse acceleration; determining a setpoint value of a velocity-dependent braking deceleration based on the driving velocity; and ascertaining the optimal braking deceleration based on the setpoint value of the transverse acceleration-dependent braking deceleration and the setpoint value of the velocity-dependent braking deceleration such that the optimal braking deceleration has, as a mathematical function of the variables driving velocity and transverse acceleration, an opposite monotonicity with respect to these variables.

2. The method according to claim 1, wherein the optimal braking deceleration is ascertained that it is at a maximum for a minimum absolute value of the transverse acceleration-dependent braking deceleration and/or at a minimum for a maximum absolute value of the transverse acceleration-dependent braking deceleration.

3. The method according to claim 1, wherein the optimal braking deceleration is ascertained as a convex function of the transverse acceleration-dependent braking deceleration and/or as a concave function of the velocity-dependent braking deceleration.

4. The method according to claim 1, wherein the optimal braking deceleration is ascertained based on: a weighted mean value; a p-norm; and/or an extreme value formation, into which at least the setpoint values of the transverse acceleration-dependent braking deceleration and the velocity-dependent braking deceleration are incorporated in each case.

5. The method according to claim 1, wherein the transverse acceleration-dependent braking deceleration is formed based on the square of the transverse acceleration and based on an initial value.

6. The method according to claim 1, wherein a distance to a critical object of the critical driving situation is captured with the aid of the traffic sensor system, wherein a setpoint value of a distance-dependent braking deceleration is ascertained on the basis of this distance, wherein the ascertainment of the optimal braking deceleration also takes place based on the setpoint value of the distance-dependent braking deceleration, and wherein the optimal braking deceleration has, as a mathematic function of the variable distance, the same monotonicity as with respect to the variable transverse acceleration.

7. The method according to claim 1, wherein an object acceleration of the or a critical object is ascertained with the aid of the traffic sensor system, wherein a setpoint value of an object-dependent braking deceleration is ascertained based on the object acceleration, wherein the ascertainment of the optimal braking deceleration also takes place on the basis of the setpoint value of the optimal object-dependent braking deceleration, and wherein the optimal braking deceleration has, as a mathematic function of the variable object acceleration, an opposite monotonicity with respect to the variable transverse acceleration.

8. The method according to claim 1, wherein a value of a friction for the motor vehicle on a road is ascertained with the aid of the force sensor system, wherein a setpoint value of a friction-dependent acceleration is ascertained based on the value of friction, wherein the ascertainment of the optimal braking deceleration also takes place based on the setpoint value of the friction-dependent braking deceleration, and wherein the optimal braking deceleration has, as a mathematic function of the variable friction, an opposite monotonicity as with respect to the variable transverse acceleration.

9. The method according to claim 8, wherein the optimal braking deceleration is formed on the basis of a maximum formed from: the setpoint value of the transverse acceleration-dependent braking deceleration; the setpoint value of the friction-dependent braking deceleration; and a further function, which, in turn, is formed basis on a minimum formed from the setpoint value of the distance-dependent braking deceleration, the setpoint value of the velocity-dependent braking deceleration, and the setpoint value of the object-dependent braking deceleration.

10. A motor vehicle comprising: an emergency system to avoid a collision, the emergency system comprising: an associated traffic sensor system to capture a traffic situation; and a force sensor system to capture forces acting in each case upon the motor vehicle and/or upon individual axles and/or wheels, wherein the emergency system is configured to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0041] FIG. 1 schematically shows a motor vehicle comprising an emergency system for avoiding collisions; and

[0042] FIG. 2 schematically shows individual braking decelerations dependent on different parameters, which are used in the emergency system according to FIG. 1 for an optimal braking deceleration in an evasive maneuver.

DETAILED DESCRIPTION

[0043] FIG. 1 schematically shows a motor vehicle 2 comprising an emergency system 4 for avoiding collisions 4. Emergency system 4 comprises a traffic sensor system 6, with the aid of which a traffic situation is captured, in which motor vehicle 2 is situated in each case. Traffic sensor system 6 has a number of front-facing cameras 7 and a number of rear-facing cameras 8. Viewing angles 10, 12 of front-facing cameras 7 and rear-facing cameras 8 are also illustrated schematically in FIG. 1. Traffic sensor system 6 additionally includes further sensors 9 for capturing distances and velocities of objects in the traffic situation, these sensors 9 being able to be constituted, for example, by radar and/or lidar sensors, and the objects being able to be constituted by other vehicles or other road users or also by obstacles or boundaries in the vicinity of a traffic lane.

[0044] Individual cameras 7, 8 and sensors 9 of traffic sensor system 6 are connected to an evaluation unit 14, which, on the one hand, specifically recognizes a traffic situation (and thus the associated objects, such as road alignment, vehicles, etc.) in the image data generated by front-facing and rear-facing cameras 7, 8, and, on the other hand, ascertains the velocities and accelerations of other objects, in particular other road users in the traffic situation, on the basis of data generated by sensors 9. Data 19 of the captured traffic situation are forwarded to a control unit 20 of emergency system 4, in which it is recognized whether a critical driving situation is present, i.e., whether, for example, a collision with another vehicle, with another road user, or with a boundary or an obstacle is imminent. If this is the case, control unit 20 automatically initiates an evasive maneuver, for which the driving velocity of motor vehicle 2 is also reduced by an optimal braking deceleration in a manner still to be described.

[0045] To carry out this method, emergency system 4 also comprises a force sensor system 15, which has a transverse acceleration sensor 16 as well as further wheel sensors 18. Transverse acceleration sensor 16 is configured to capture a transverse acceleration ay and forward it to the control unit. Wheel sensors 18 are configured to capture, among other things, a velocity v of motor vehicle 2 as well as further forces acting upon the wheels (such as slip and the like), so that control unit 20 may calculate, for example, a friction value from these forces.

[0046] A velocity-dependent braking deceleration axv, a transverse acceleration-dependent braking deceleration axy, a distance-dependent braking deceleration axd, a friction-dependent braking deceleration axu, and an object-dependent braking deceleration axo are each illustrated in a diagram in FIG. 2.

[0047] Velocity-dependent braking deceleration axv is illustrated as a function of a velocity v of motor vehicle 2 according to FIG. 1 and, in the present case, has the dependency (see above) defined in equation (iv); its absolute value is thus, for example, strictly monotonously increasing in velocity v. Transverse acceleration-dependent braking deceleration axy is illustrated as a function of transverse acceleration ay and, in the present case, has the dependency (see above) defined in equation (iii); its absolute value is thus strictly monotonously decreasing in transverse acceleration ay. Velocity v and transverse acceleration ay are captured by radar sensors 18 and transverse acceleration sensor 16, respectively, in particular in the manner described above.

[0048] Distance-dependent braking deceleration axd is illustrated as a function of a distance d to a critical object, which, in a critical driving situation, may be constituted, for example, by the object with which the collision is imminent, or by a further object with which a collision may also be about to happen, or which is to be taken into account in planning the optimal braking deceleration as a result of its proximity to the trajectory of motor vehicle 2. In the present case, distance-dependent braking deceleration axd is initially constant up to a distance value d1 for a vanishing distance d, starting from an initial value admax having a maximum absolute value of the braking deceleration. Between distance value d1 and a distance value d2>d1, the absolute value of distance-dependent braking deceleration |axd| decreases to a minimum absolute value at admin and is constant for distances d>d2. This profile take into account the circumstance that the selection of the absolute value of the braking deceleration is to be greater a priori the close the proximity to a critical object, although the braking deceleration should not exceed a maximum absolute value (which is defined by admax) for reasons of driving physics.

[0049] Friction-dependent braking deceleration ax is illustrated as a function of friction , and its absolute value is monotonously increasing in these variables. In the present case, friction-dependent braking deceleration ax is also zero for a vanishing friction =0 and surroundings u up to a minimum value ulo of the friction, which takes into account the circumstance that no significant braking force may be transferred to the roadway with a vanishing or very low friction. This is possible to a significant degree only starting at minimum value ulo. For friction values >lo, the absolute value of friction-dependent braking deceleration |ax| increases (linearly in the present case) until friction-dependent braking deceleration ax reaches and maintains its absolute value maximum at amax, starting at an upper limit hi of friction . This absolute value maximum may be defined, for example, by a maximum possible braking force transfer. The forces at the wheels ascertained by wheel sensors 18 of motor vehicle 2, for example, are used to ascertain the specific value of friction .

[0050] Object-dependent braking deceleration axo is illustrated as a function of an object acceleration aob of this critical object (i.e., for example, another vehicle), which is preferably ascertained by control unit 20 from data 19 of the traffic situation captured by traffic sensor system 6. Object-dependent braking deceleration axo essentially has a profile comparable to distance-dependent braking deceleration axd, but with the opposite monotonicity, which takes into account the circumstance that a critical driving situation becomes more critical as distance d of a critical object decreases (i.e., the danger of collision increases), and/or as acceleration aop of the critical object increases.

[0051] The optimal braking deceleration may now be ascertained from the variables specified here in the functional dependency already described above, in particular according to equation (v) (the maximum and minimum formations being expandable by suitable p-norms or comparable operations).

[0052] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.