Method and device for operating a motor vehicle

Abstract

A method for operating a motor vehicle, the motor vehicle being automatically accelerated and decelerated as a function of an instantaneous position and a predefinable target location, so that it comes to a standstill at the target location, including the following steps: a) accelerating the motor vehicle, in particular from a standstill, to a predefined setpoint velocity; b) up to a predefined first distance of the motor vehicle to the target location, decelerating the motor vehicle to a predefined rolling velocity; c) starting at a predefined second distance of the motor vehicle to the target location, decelerating the motor vehicle to a standstill, the second distance to the target location being smaller than the first distance.

Claims

1. A method for operating a motor vehicle, the method comprising: a) automatically accelerating the motor vehicle from a standstill, to a predefined setpoint velocity; b) automatically decelerating, up to a predefined first distance of the motor vehicle to a target location, the motor vehicle to a predefined rolling velocity, wherein the motor vehicle is automatically accelerated and decelerated as a function of an instantaneous position and a predefinable target location; and c) starting at a predefined second distance of the motor vehicle to the target location, decelerating the motor vehicle to a standstill, the second distance to the predefinable target location being smaller than the first distance, wherein the motor vehicle comes to a standstill at the target location; wherein the motor vehicle is initially decelerated to the rolling velocity, where the rolling velocity is maintained until the second distance to the target location is reached, wherein only then is a deceleration of the motor vehicle carried out to the point of stopping, wherein in a rolling phase, the motor vehicle is moved by using the rolling velocity so that the motor vehicle does not stop prematurely, and wherein before reaching the target location, which is the second distance, the motor vehicle transitions into a planning phase which provides a vanishing velocity at the target location, and wherein an instantaneous driving velocity falls below the predefined rolling velocity during the deceleration results in the setpoint velocity or a setpoint rolling velocity being adjusted or set to a minimum of an undershoot velocity, so that in the case of undershooting, the vehicle is no longer accelerated back to the setpoint rolling velocity, so as to reduce jolt as brake application is increased, and so that a last brake phase is not initiated directly from an acceleration phase, wherein the instantaneous driving velocity is compared with the rolling velocity, the rolling velocity then being set to a minimum of the driving velocity when the driving velocity falls below the rolling velocity immediately prior to c), wherein the rolling velocity is predefined to be greater than or equal to a predefined minimum velocity, so that during undershooting, the rolling velocity is prevented from falling below a predefined minimum velocity, so that the minimum velocity is selected so that the rolling velocity falls below a predefined minimum value, and so that the minimum velocity is selected so that a premature stopping of the motor vehicle due to a target velocity that is too low is prevented, wherein at a third distance to the target location, which is smaller than the second distance, the motor vehicle is constantly decelerated up to the target location, so that no successive trajectories must be planned, wherein a velocity is already reduced prior to reaching the first distance, in order to have reached the rolling velocity upon reaching the first distance, and wherein the predefined minimum value is above zero, since the rolling velocity cannot fall below the predefined minimum value.

2. The method as recited in claim 1, wherein a point in time of the deceleration in b) is determined as a function of a setpoint deceleration so that the motor vehicle continues to be moved at the rolling velocity starting at the first distance.

3. The method as recited in claim 1, wherein the setpoint deceleration is predefined between 0.1 m/s.sup.2 through 1 m/s.sup.2.

4. The method as recited in claim 1, wherein, if a total distance to reach the target location is smaller than the first distance, then the motor vehicle is accelerated to the minimum velocity in a).

5. The method as recited in claim 1, wherein the target velocity is predefined to be between 0.5 km/h and 20 km/h.

6. The method as recited in claim 5, wherein the target velocity is predefined to be between 1 km/h and 10 km/h.

7. The method as recited in claim 1, wherein the rolling velocity is predefined to be between 0.1 km/h and 1 km/h.

8. The method as recited in claim 7, wherein the rolling velocity is predefined to be between 0.2 km/h and 0.6 km/h.

9. The method as recited in claim 1, wherein the minimum velocity is predefined to be between 0.05 km/h and 0.7 km/h.

10. The method as recited in claim 9, wherein the minimum velocity is predefined to be between 0.1 km/h through 0.4 km/h.

11. The method as recited in claim 1, wherein a predefined first distance is predefined to be between 30 cm and 250 cm.

12. The method as recited in claim 11, wherein the predefined first distance is predefined to be between 70 cm and 150 cm.

13. The method as recited in claim 1, wherein a predefined second distance is predefined to be between 20 cm and 120 cm.

14. The method as recited in claim 13, wherein the predefined second distance is predefined to be between 40 cm and 80 cm.

15. The method as recited in claim 1, wherein a predefined third distance is predefined to be between 5 cm and 60 cm.

16. The method as recited in claim 15, wherein the predefined third distance is predefined to be between 10 cm and 30 cm.

17. The method as recited in claim 4, wherein a predefined total distance is predefined to be between 1 cm and 2000 cm.

18. The method as recited in claim 17, wherein the predefined total distance is predefined to be between 5 cm and 1000 cm.

19. A device for operating a motor vehicle, which includes a controllable drive unit and a controllable braking system, comprising: a control unit for operating the motor vehicle, and being configured to perform the following: a) automatically accelerating the motor vehicle from a standstill, to a predefined setpoint velocity; b) automatically decelerating, up to a predefined first distance of the motor vehicle to a target location, the motor vehicle to a predefined rolling velocity, wherein the motor vehicle is automatically accelerated and decelerated as a function of an instantaneous position and a predefinable target location; and c) starting at a predefined second distance of the motor vehicle to the target location, decelerate the motor vehicle to a standstill, the second distance to the target location being smaller than the first distance, wherein the motor vehicle comes to a standstill at the target location; wherein the motor vehicle is initially decelerated to the rolling velocity, where the rolling velocity is maintained until the second distance to the target location is reached, wherein only then is a deceleration of the motor vehicle carried out to the point of stopping, wherein in a rolling phase, the motor vehicle is moved by using the rolling velocity so that the motor vehicle does not stop prematurely, and wherein before reaching the target location, which is the second distance, the motor vehicle transitions into a planning phase which provides a vanishing velocity at the target location, and wherein an instantaneous driving velocity falling below the predefined rolling velocity during the deceleration results in the setpoint velocity or a setpoint rolling velocity being adjusted or set to a minimum of an undershoot velocity, so that in the case of undershooting, the vehicle is no longer accelerated back to the setpoint rolling velocity, so as to reduce jolt as brake application is increased, and so that a last brake phase is not initiated directly from an acceleration phase, wherein the instantaneous driving velocity is compared with the rolling velocity, the rolling velocity then being set to a minimum of the driving velocity when the driving velocity falls below the rolling velocity immediately prior to c), wherein the rolling velocity is predefined to be greater than or equal to a predefined minimum velocity, so that during undershooting, the rolling velocity is prevented from falling below a predefined minimum velocity, so that the minimum velocity is selected so that the rolling velocity falls below a predefined minimum value, and so that the minimum velocity is selected so that a premature stopping of the motor vehicle due to a target velocity that is too low is prevented, wherein at a third distance to the target location, which is smaller than the second distance, the motor vehicle is constantly decelerated up to the target location, so that no successive must be planned, wherein a velocity is already reduced prior to reaching the first distance, in order to have reached the rolling velocity upon reaching the first distance, and wherein the predefined minimum value is above zero, since the rolling velocity cannot fall below the predefined minimum value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a motor vehicle in a simplified representation.

(2) FIG. 2 shows a flow chart for explaining one advantageous method for operating the motor vehicle.

(3) FIG. 3 shows a diagram for explaining the method.

(4) FIG. 4 shows one exemplary embodiment of the method.

(5) FIG. 5 shows another exemplary embodiment of the method.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) FIG. 1 shows a simplified representation of a motor vehicle 1, which is located on solid ground, for example, a parking lot 2, at a position A. Motor vehicle 1 has a drive unit 3, which includes, for example, an internal combustion engine and/or at least an electric machine, which is connected or connectable to the wheels of the motor vehicle directly or via a transmission. Furthermore, motor vehicle 1 includes a braking system 4, which may exert a brake force as needed on at least one wheel of motor vehicle 1 to decelerate motor vehicle 1. In particular, if drive unit 3 includes one or multiple electric machines, then these may also be used by braking system 4 for decelerating or braking motor vehicle 1. Otherwise, braking system 4 preferably includes one or multiple wheel brakes which interact mechanically, for example, through friction, with the wheels of the motor vehicle. Furthermore, motor vehicle 1 includes a control unit 5 which is designed to control drive unit 3 and braking system 4 in such a way that an autonomous or automated longitudinal guiding of motor vehicle 1 to reach target location B is enabled. For example, target location B is a parking space on parking lot 2 into which motor vehicle 1 is to be moved.

(7) One advantageous method for operating motor vehicle 1 is explained below by way of the flow chart in FIG. 2, the method being carried out in particular by control unit 5.

(8) In a first step S1, the method is initialized, for example, in that the driver of motor vehicle 1 predefines or selects target location B and starts an automated parking operation/driving operation. In a subsequent step S2, control unit 5 calculates the travel path d.sub.total from instantaneous position A to target position B, which must be traveled by motor vehicle 1 to arrive at target location B.

(9) Depending on the travel path established in step S2, a trajectory is determined in subsequent step S3, which represents the acceleration progression of motor vehicle 1 to reach target location B, so that motor vehicle 1 comes to a standstill at target location B. In the present case, it is thereby assumed that vehicle 1 is likewise stopped at instantaneous location A.

(10) During the trajectory formation, three trajectory segments are advantageously formed which are a function of the total distance d.sub.total. Initially in a step S4, a setpoint velocity v.sub.tar is predefined, up to which motor vehicle 1 is to be accelerated starting from point of departure A. The time is also established within which the target velocity is to be maintained.

(11) The time is thereby determined by a distance d.sub.roll to target location B, as is shown in FIG. 1. In step S5, in addition to distance d.sub.roll, a rolling velocity v.sub.roll is also determined, which motor vehicle 1 is to have reached upon reaching distance d.sub.roll.

(12) In this context, FIG. 3 shows in a diagram the velocity progression of motor vehicle 1, which arises from the method described according to FIG. 2 and FIG. 1. It is thereby apparent that if the motor vehicle is to already have reached rolling velocity v.sub.roll at distance d.sub.roll, then the velocity of the motor vehicle must be reduced at a preceding point in time or at distance d.sub.v. In the present case, distance d.sub.v, which is greater than distance d.sub.roll to target location B, is preferably selected as a function of a setpoint deceleration. In particular, a setpoint deceleration in the range of 0.1 m/s.sup.2 through 1 m/s.sup.2 is assumed here. Distance d.sub.v is thus selected as a function of setpoint velocity v.sub.tar and distance d.sub.roll. The rolling velocity is maintained until the distance to target location B is reduced to a distance d.sub.end.

(13) Upon reaching distance d.sub.end, a deceleration is determined in step S6 due to which motor vehicle 1 provides a vanishing velocity or arrives at a standstill at target location B (distance=0).

(14) In a step S7, the actuators or drive unit 3 and braking system 4 are controlled to follow the trajectory according to FIG. 3. The trajectory being able to be checked and adjusted while the method is being carried out or already during the movement operation. In particular, the instantaneous position of motor vehicle 1 is constantly monitored in a step S8 and compared with an expected position or setpoint position predicted according to the trajectory. If the instantaneous position does not correspond to the expected position, or the position of the motor vehicle upon standstill does not correspond to end position B (n), then the method is carried out again in a step S3, if necessary with a new trajectory planning. If motor vehicle 1 follows the predefined trajectory, then the method is carried out again until motor vehicle 1 comes to a standstill at target location B. If the instantaneous position then corresponds to desired end position (j), then the method is ended in step S9.

(15) FIG. 4 shows another exemplary embodiment of the previously described method, an enlarged detail of the diagram from FIG. 3 being shown in FIG. 4, which relates to the end area of the movement of the motor vehicle. According to this exemplary embodiment, it is provided that, when the instantaneous driving velocity falls below the predefined rolling velocity v.sub.roll during the deceleration to d.sub.roll, the setpoint velocity or the setpoint rolling velocity V.sub.roll,tar is adjusted or set to the minimum of undershoot v.sub.roll,min. This has the advantage that, in the case of undershooting, it is no longer accelerated back to the setpoint rolling velocity. This reduces the jolt and the comfort of the brake application is increased. The stopping accuracy is also improved thereby since the last brake phase starting at d.sub.end is not initiated directly from an acceleration phase.

(16) Target rolling velocity v.sub.roll,tar is preferably always set as greater than or equal to minimum velocity v.sub.roll,min, so that in particular a premature stopping of motor vehicle 1 due to a target velocity that is too low is prevented. The minimum velocity may thereby be adjusted, for example, as a function of an instantaneous roadway incline.

(17) FIG. 5 shows another exemplary embodiment that differs from the previous exemplary embodiments in that, starting at distance d.sub.ramp, which is smaller than distance d.sub.end, a constant deceleration is used up to the target location. This has the advantage that no chronologically short trajectories need to be planned, whereby the stopping accuracy is improved.

(18) In the case that total distance d.sub.total is less than distance d.sub.roll, minimum velocity v.sub.roll,min is used as the target velocity for the controller, which means, for example, in contrast to long moves, a target velocity requested by another control unit is ignored. This has the advantage, that no unnecessarily strong accelerations are used for short movements or motions, thus the comfort and stopping accuracy are improved.

(19) In the following, preferred variables for target velocity v.sub.tar, rolling velocity v.sub.roll, and minimum velocity v.sub.roll,min and as well for the various distances are indicated, the absolute value being indicated with regard to the distances, even if the distances appear as negatives in the figures.

(20) v.sub.tar: 0.5 km/h through 20 km/h, preferably 1 km/h through 10 km/h

(21) v.sub.roll: 0.1 km/h through 1 km/h, preferably 0.2 km/h through 0.6 km/h

(22) V.sub.roll,min: 0.05 km/h through 0.7 km/h, preferably 0.1 km/h through 0.4 km/h

(23) d.sub.ramp: 5 cm through 60 cm, preferably 10 cm through 30 cm

(24) d.sub.end: 20 cm through 120 cm, preferably 40 cm through 80 cm

(25) d.sub.roll: 30 cm through 250 cm, preferably 70 cm through 150 cm

(26) d.sub.total: 1 cm through 2000 cm, preferably 5 cm through 1000 cm