Method for determining a maximum speed of a vehicle during a parking maneuver

Abstract

A method for determining a maximum speed of a vehicle during a parking maneuver, in which at least one surroundings condition is detected with the aid of at least one sensor unit and supplied to a control unit as an input variable.

Claims

1. A method for determining a maximum speed of a vehicle during a parking maneuver of a parking process, comprising the following steps: detecting at least one surroundings condition using at least one sensor unit; supply the detected at least one surroundings condition to a control unit as an input variable; ascertaining a maximum possible deceleration of at least one brake circuit of a braking system of the vehicle; and supplying the ascertained maximum possible deceleration to the control unit as another input variable to determine the maximum speed, the braking system including at least two actuators for actuating a braking element, the at least two actuators including a primary actuator and a secondary actuator, the secondary actuator being actuated at least in the event of a failure of the primary actuator, wherein the maximum possible deceleration is ascertained taking a performance capability of the secondary actuator into consideration.

2. The method as recited in claim 1, wherein the primary actuator is used to actuate the braking element as long as a performance capability of the primary actuator is greater than that of the secondary actuator.

3. The method as recited in claim 1, wherein a presently possible maximum deceleration of the at least one actuator is ascertained based on additional information.

4. The method as recited in claim 3, wherein the additional information includes brake wear and/or braking effect.

5. The method as recited in claim 1, wherein maximum possible decelerations of the primary and secondary actuators are predefined values which are stored in the control unit in the form of characteristic maps.

6. The method as recited in claim 1, wherein the at least one surroundings condition is an uphill grade and/or a friction coefficient and/or a distance from an obstacle.

7. The method as recited in claim 6, wherein the at least one surroundings condition is the uphill grade, the uphill grade being ascertained once at a start of the parking process or, in the case of multi-step parking maneuvers, at a start of each step of the multi-step parking maneuvers.

8. The method as recited in claim 6, wherein the at least one surroundings condition is the uphill grade, the uphill grade being continuously ascertained, taking odometry data into consideration.

9. The method as recited in claim 6, wherein in the at least one surroundings condition is the distance from an obstacle and when no obstacle is ascertained using a distance sensor, the range of the distance sensor is used as the distance.

10. The method as recited in claim 1, wherein the parking process is carried out as a fully automatic parking process.

11. The method as recited in claim 10, wherein the parking process is terminated when a defect of the primary actuator is identified by initiating a brake application with the maximum possible deceleration.

12. The method as recited in claim 1, wherein an accelerator characteristic curve is set as a function of the ascertained maximum possible speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a simplified illustration of a vehicle during a fully automatic parking process.

(2) FIG. 2 shows a block diagram to elucidate the calculation of a maximum speed during the parking process.

(3) FIG. 3 shows a chart to elucidate different accelerator characteristic curves, taking different maximum parking speeds into consideration.

(4) Identical elements and elements having identical functions are denoted by identical reference numerals in the figures.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(5) FIG. 1 shows a (fully) automated parking process of a vehicle 1 into a parking spot 2 in a highly simplified manner. Vehicle 1 is already situated within parking spot 2 at a distance a from a further vehicle 3 in the reverse driving direction of vehicle 1, vehicle 3 representing an obstacle. V.sub.max denotes the presently maximum driving speed of vehicle 1 in the direction toward further vehicle 3, which must not be exceeded to ensure safe stopping of vehicle 1 within distance a prior to a collision with further vehicle 3.

(6) Furthermore, it is assumed for the automatic parking process that the driver both specifies present driving speed V by a corresponding actuation of the accelerator pedal, and brings vehicle 1 to a standstill by an actuation of the brake. As an alternative, it may be provided that a control unit 10 of vehicle 1 carries out a fully automatic brake application of vehicle 1, should the driver not initiate a corresponding braking maneuver in a timely manner or actuate the brake pedal in such a way that a braking of vehicle 1 in front of further vehicle 3 is ensured.

(7) FIG. 2 shows a block diagram to elucidate the calculation of presently maximum possible speed V.sub.max of vehicle 1 during the parking process. It is assumed in the process that vehicle 1, in the conventional manner, includes a first sensor unit 11 for detecting distance a from an obstacle or from further vehicle 3 in the direction of the respective driving or parking direction. Vehicle 10 furthermore includes a second sensor unit 12 for detecting the driving direction or route 4. A third sensor unit 13 is designed to ascertain, for example based on an ascertained or a detected uphill grade of the roadway on which vehicle 1 is presently situated, the axle loads on the front axle and the rear axle of vehicle 1. Lastly, a fourth sensor unit 14 may optionally be provided, which is designed to ascertain a friction coefficient μ between the tire and the road or the roadway. If no fourth sensor unit 14 is provided, the corresponding data may also be ascertained based on other surroundings data, for example, or be stored as a predefined value in control unit 10.

(8) Furthermore, it is assumed that a braking system 20 of vehicle 1 includes a primary actuator 16 and a secondary actuator 17, which (automatically) takes effect instead of primary actuator 16 in the event of a defect of primary actuator 16. Both primary actuator 16 and secondary actuator 17 are an integral part of at least one brake circuit of braking system 20 of vehicle 1 and act on a braking element 24, for example on the brake disk(s) of vehicle 1.

(9) A first arrangement 18, which is assigned to primary actuator 16, are used to detect the present performance capability of primary actuator 16, for example taking the brake wear or the braking effect into consideration. Second arrangement 19 is assigned to secondary actuator 17 and, similarly to first arrangement 18, is used to ascertain the present performance capability of secondary actuator 17, in particular, the maximum possible braking force F.sub.Brake.

(10) FIG. 2 shows a first program block 21, which supplies predefined data of vehicle 1, for example position of center of gravity CG of vehicle 1 and mass M of vehicle 1, as input variables to an algorithm 25, which is an integral part of control unit 10. A friction coefficient μ between the tires of vehicle 1 and the roadway is ascertained within a second program block 23, or a corresponding value is predefined. Driving direction FR and uphill grade S of the roadway are also ascertained, each taking the present position of vehicle 1 into consideration.

(11) The values ascertained in second program block 23 are also supplied to algorithm 25 as input variables. In a step 26, algorithm 25 ascertains a maximum transmittable force F.sub.max, which may be transmitted from vehicle 1 onto the roadway, from the indicated input values.

(12) A third program block 32 relates to secondary actuator 17. In a step 33, the error recognition time is taken into consideration which elapses until control unit 10 of vehicle 1 recognizes that primary actuator 16 has failed or has a performance capability which is lower than the performance capability of secondary actuator 17. In step 34, the dead time is taken into consideration which is required for secondary actuator 17 to be activated instead of primary actuator 16. In a step 35, the present performance capability of secondary actuator 17, i.e., the transmittable braking force F.sub.Brake, is subsequently ascertained. This value is supplied to a fourth program block 43 as an input variable.

(13) In fourth program block 43, a possible deceleration VZ of secondary actuator 17 is ascertained, taking maximum transmittable force F.sub.max from step 26 into consideration.

(14) In a subsequent fifth program block 44, a stopping distance A may be ascertained based on present speed V and possible deceleration VZ with the aid of secondary actuator 17. This stopping distance A is subsequently used in a sixth program block 45 to ascertain maximum possible speed V.sub.max which vehicle 1 may presently have to enable safe stopping within available distance a from further vehicle 3.

(15) The ascertained maximum speed V.sub.max may be translated into a corresponding accelerator characteristic curve 51, 52 in accordance with the representation of FIG. 3. For elucidation, two accelerator characteristic curves 51, 52 for different maximum speeds V.sub.max 51 and V.sub.max 52 are shown against pedal travel PW in the illustration in FIG. 3. In particular, it is apparent that the driver himself or herself, with a maximally depressed accelerator pedal in each case, is at the most able to achieve the corresponding maximum speed V.sub.max 51 or V.sub.max 52, accelerator characteristic curve 51, 52, as elucidated above based on the illustration of FIG. 2, being adapted to the present performance capability of secondary actuator 17.

(16) The method described thus far may be altered or modified in a variety of ways, without departing from the inventive idea. For example, it is provided that the sensor range of first sensor unit 11 is assessed as a corresponding distance a in the event that first sensor unit 11 does not detect an obstacle or a further vehicle 3 in the driving direction.