Limiting a target value for a control variable of a driver assistance system

Abstract

A driver assistance system is configured to determine or receive a setpoint value for a control variable of the motor vehicle, to determine or receive an actual value for the control variable of the motor vehicle, to determine a correction value for reducing a deviation between the setpoint value for the control variable and the actual value for the control variable depending on the deviation between the setpoint value for the control variable and the actual value for the control variable, to compare the correction value with a first threshold value, and at least to limit a future change in the setpoint value for the control variable which increases the deviation between the target value for the control variable and the actual value for the control variable depending on the comparison of the correction value with the first threshold value.

Claims

1. A system for controlling a motor vehicle, comprising: at least one controller configured to: determine or receive a setpoint value for a control variable of the motor vehicle, wherein the control variable relates to a speed of the motor vehicle and/or a steering angle of the motor vehicle, determine or receive an actual value for the control variable of the motor vehicle, determine, in a manner which is dependent on a deviation between the setpoint value for the control variable and the actual value for the control variable, a correction variable for decreasing the deviation between the setpoint value for the control variable and the actual value for the control variable, wherein the correction variable relates to an acceleration of the motor vehicle and/or a derivative of the steering angle of the motor vehicle with respect to time, compare the correction variable with a first threshold value, and enter a limiting mode to at least limit a future change of the setpoint value for the control variable, which future change increases the deviation between the setpoint value for the control variable and the actual value for the control variable, in a manner which is dependent on the comparison of the correction variable with the first threshold value, compare the correction variable with a second threshold value, at least partially cancel the limiting mode to allow the future change of the setpoint value for the control variable in a manner which is dependent on the comparison of the correction variable with the second threshold value, control the speed of the motor vehicle and/or the steering angle of the motor vehicle in accordance with the control variable, and control the acceleration and/or the derivative of the steering angle with respect to time in accordance with the correction variable.

2. The system according to claim 1, wherein the at least one controller is further configured to: enter into the limiting mode to at least limit the future change of the setpoint value for the control variable when: (i) the setpoint value for the control variable is greater than the actual value for the control variable, and (ii) the correction variable is greater than or greater than or equal to the first threshold value.

3. The system according to claim 1, wherein the at least one controller is further configured to: enter into the limiting mode to at least limit the future change of the setpoint value for the control variable in a manner which is dependent on the comparison of the correction variable with the first threshold value for a predefined time duration.

4. The system according to claim 1, wherein the magnitude of the first threshold value is greater than the magnitude of the second threshold value.

5. The system according to claim 1, wherein the at least one controller is further configured to: enter into the limiting mode to limit the future change of the setpoint value in such a way that the change of the setpoint value is prevented.

6. A method for controlling a motor vehicle, the method comprising the steps of: determining or receiving, by at least one controller, a setpoint value for a control variable of the motor vehicle, wherein the control variable relates to a speed of the motor vehicle and/or a steering angle of the motor vehicle; determining or receiving, by the at least one controller, an actual value for the control variable of the motor vehicle; determining, by the at least one controller, a correction variable for decreasing deviation between the setpoint value for the control variable and the actual value for the control variable in a manner which is dependent on a deviation between the setpoint value for the control variable and the actual value for the control variable, wherein the correction variable relates to an acceleration of the motor vehicle and/or a derivative of the steering angle of the motor vehicle with respect to time; comparing, by the at least one controller, the correction variable with a first threshold value; entering into a limiting mode to at least limit, by the at least one controller, a future change of the setpoint value for the control variable, which future change increases the deviation between the setpoint value for the control variable and the actual value for the control variable, in a manner which is dependent on the comparison of the correction variable with the first threshold value; comparing, by the at least one controller, the correction variable with a second threshold value, at least partially cancelling, by the at least one controller, the limiting mode to allow the future change of the setpoint value for the control variable in a manner which is dependent on the comparison of the correction variable with the second threshold value, controlling, by the at least one controller, the speed of the motor vehicle and/or the steering angle of the motor vehicle in accordance with the control variable, and controlling, by the at least one controller, the acceleration and/or the derivative of the steering angle with respect to time in accordance with the correction variable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows one exemplary embodiment of exemplary profiles of a setpoint speed v.sub.set and an actual speed v.sub.act as setpoint value and actual value of a control variable of the motor vehicle.

(2) FIG. 2 shows one exemplary embodiment of an exemplary profile of a vehicle acceleration a as correction variable.

(3) FIG. 3 shows a diagrammatic controller structure as one exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a time profile of a setpoint value v.sub.set for a control variable of the motor vehicle KFZ, which time profile has been determined or received by a driver assistance system FAS.

(5) Here, the control variable is characteristic, for example, of a speed of the motor vehicle KFZ (for example, the speed of the motor vehicle KFZ itself), and the correction variable is characteristic of an acceleration of the motor vehicle KFZ (for example, the acceleration of the motor vehicle KFZ itself).

(6) Moreover, FIG. 1 also shows a time profile of an actual value v.sub.set for the control variable of the motor vehicle KFZ, which time profile has likewise been determined or received by the driver assistance system FAS.

(7) Here, the driver assistance system FAS is set up to determine, in a manner which is dependent on a deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable, to determine a correction variable a for decreasing the deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable.

(8) Here, the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable are identical at the beginning of the exemplary embodiment for reasons of clarity. In practice, the two values are frequently different, solely on account of a time offset which can be due to the use of a controller.

(9) At time t0, the setpoint value v.sub.set for the control variable begins to rise, it also being possible for the actual value v.sub.act the control variable to follow at this time.

(10) At time t1, however, a deviation arises between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable. The magnitude of the deviation rises up to time t2 and then remains constant.

(11) FIG. 2 shows a time profile of the correction variable a for the timescale (shown in FIG. 1) of the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable.

(12) Since, up to time t1, the setpoint value v.sub.set for the control variable corresponds to the actual value v.sub.act for the control variable, the correction variable a has the value “zero” up to time t1.

(13) The correction variable a also rises, however, with the deviation which arises from time t1 between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable.

(14) Here, the driver assistance system FAS is set up to compare the correction variable a with a first threshold value sw, and to at least limit a future change of the setpoint value v.sub.set for the control variable, which future change increases the deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable, in a manner which is dependent on the comparison of the correction variable a with the first threshold value sw.

(15) In the present example, the correction variable a reaches the first threshold value sw at time t2. Therefore, from said time, a further increase of the setpoint value v.sub.set for the control variable is limited in such a way that the change of the setpoint value v.sub.set is prevented.

(16) Here, in particular, the driver assistance system FAS is set up to at least limit the future change of the setpoint value v.sub.set for the control variable if the setpoint value v.sub.set for the control variable is greater than the actual value v.sub.act for the control variable, and the correction variable a is greater than or greater than or equal to the first threshold value sw.

(17) Moreover, the driver assistance system FAS is set up to compare the correction variable a with a second threshold value aw, and to at least partially cancel the limiting of the future change of the setpoint value v.sub.set for the control variable in a manner which is dependent on the comparison of the correction variable a with the second threshold value aw.

(18) In the present case, the correction variable a begins to fall again at time t3, and reaches the second threshold value aw at time t4.

(19) Here, the magnitude of the first threshold value sw is greater than the magnitude of the second threshold value aw. Here, the basis is formed by the concept that, although the lower value of the second threshold value is still characteristic of a deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable, this can be, for example, a tolerable deviation.

(20) FIG. 3 shows a diagrammatic controller structure as one exemplary embodiment of the invention.

(21) Here, a setpoint value v.sub.set for a control variable of the motor vehicle KFZ is determined by a trajectory planning unit TP and is transferred to the driver assistance system FAS.

(22) Moreover, the driver assistance system FAS also receives an actual value v.sub.act for the control variable of the motor vehicle KFZ.

(23) In a manner which is dependent on a deviation which arises as a result of a disruptive influence s between the setpoint value v.sub.set for the control variable and the actual value v.sub.act to the control variable, the driver assistance system FAS determines a correction variable a in order to decrease the deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable. The correction variable a is, for example, a manipulated variable of a controller.

(24) Moreover, the driver assistance system is set up to compare the correction variable a with a first threshold value sw, and to at least limit a future change of the setpoint value v.sub.set for the control variable, which future change increases the deviation between the setpoint value v.sub.set for the control variable and the actual value v.sub.act for the control variable, in a manner which is dependent on the comparison of the correction variable a with the first threshold value sw, by a corresponding limiting signal b being transmitted to the trajectory planning unit.