VEHICLE CONTROL SYSTEM

Abstract

A vehicle control system with which different vehicle functions, such as a driving dynamics function and/or a component protection function, can be controlled, in which vehicle control system, in the case of onroad driving, an rpm-based vehicle speed determined by a wheel speed sensor forms a reference variable, on the basis of which the vehicle control system determines driving parameters and/or controls the vehicle function. The vehicle control system is assigned an evaluation unit which, in the presence of both offroad driving operation and a tire change signal, determines a GPS-based vehicle speed as a reference variable, on the basis of which the vehicle control system determines the driving operation parameters, such as an offroad tire diameter, and/or controls the vehicle functions.

Claims

1. A vehicle control system with which different vehicle functions, such as a driving dynamics function and/or a component protection function, can be controlled, in which vehicle control system in the case of onroad driving, an rpm-based vehicle speed determined by a wheel speed sensor forms a reference variable, on the basis of which the vehicle control system determines driving parameters and/or controls the vehicle function, wherein the vehicle control system is assigned an evaluation unit which, in the presence of both offroad driving operation and a tire change signal, which can be generated in particular in the event of a significant tire diameter deviation between offroad tires and standard tires, sets a GPS-based vehicle speed as a reference variable, on the basis of which the vehicle control system determines the driving operation parameters, such as an offroad tire diameter, and/or controls the vehicle functions.

2. The vehicle control system according to claim 1, wherein the vehicle control system determines the offroad tire diameter using the following formula, when both offroad driving and the tire change signal are present: $d_{\mathrm{offroad}}=\frac{V_{\mathrm{GPS}}.Math.1000}{.Math.n}.$

3. The vehicle control system according to claim 1, wherein the evaluation unit has a determination module which generates the tire change signal when there is a significant deviation of the rpm-based vehicle speed from the GPS-based vehicle speed.

4. The vehicle control system according to claim 3, wherein the determination module has a timer by which the determination module only generates the tire change signal when the speed difference is present over a predefined time interval.

5. The vehicle control system according to claim 1, wherein the vehicle control system has a DriveSelect mode with an offroad button that can be operated by the user and, when operated, the vehicle control system switches the vehicle functions to offroad driving mode, and/or that in particular the evaluation unit has a determination module which preferably recognizes offroad driving mode when the offroad button is operated and generates an offroad signal, and generates an onroad signal when the offroad button is not operated.

6. The vehicle control system according to claim 5, wherein in the determination module a current GPS vehicle position can be compared with a road map data set stored in the vehicle control system, and in particular the determination module generates an offroad signal or an onroad signal on the basis of the comparison or recognizes offroad driving or onroad driving operation.

7. The vehicle control system according to claim 5, wherein the evaluation unit has a provision module which, when both the offroad signal and the tire change signal are present, sets the GPS-based vehicle speed as the reference variable, and/or in that the provision module maintains the rpm-based vehicle speed as the reference variable when both the onroad signal and the tire change signal are present and/or generates a warning that the vehicle tires do not correspond to the approved specification.

8. The vehicle control system according to claim 7, wherein the evaluation unit informs the vehicle user of a liability exclusion and/or a warranty limitation when the tire change signal is present, and that in particular the vehicle user must acknowledge the liability exclusion and/or the warranty limitation in order to be able to continue driving.

9. The vehicle control system according to claim 2, wherein the evaluation unit has a determination module which generates the tire change signal when there is a significant deviation of the rpm-based vehicle speed from the GPS-based vehicle speed.

10. The vehicle control system according to claim 2, wherein the vehicle control system has a DriveSelect mode with an offroad button that can be operated by the user and, when operated, the vehicle control system switches the vehicle functions to offroad driving mode, and/or that in particular the evaluation unit has a determination module which preferably recognizes offroad driving mode when the offroad button is operated and generates an offroad signal, and generates an onroad signal when the offroad button is not operated.

11. The vehicle control system according to claim 3, wherein the vehicle control system has a DriveSelect mode with an offroad button that can be operated by the user and, when operated, the vehicle control system switches the vehicle functions to offroad driving mode, and/or that in particular the evaluation unit has a determination module which preferably recognizes offroad driving mode when the offroad button is operated and generates an offroad signal, and generates an onroad signal when the offroad button is not operated.

12. The vehicle control system according to claim 4, wherein the vehicle control system has a DriveSelect mode with an offroad button that can be operated by the user and, when operated, the vehicle control system switches the vehicle functions to offroad driving mode, and/or that in particular the evaluation unit has a determination module which preferably recognizes offroad driving mode when the offroad button is operated and generates an offroad signal, and generates an onroad signal when the offroad button is not operated.

13. The vehicle control system according to claim 6, wherein the evaluation unit has a provision module which, when both the offroad signal and the tire change signal are present, sets the GPS-based vehicle speed as the reference variable, and/or in that the provision module maintains the rpm-based vehicle speed as the reference variable when both the onroad signal and the tire change signal are present and/or generates a warning that the vehicle tires do not correspond to the approved specification.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0018] An exemplary embodiment of the invention is described in the following on the basis of the appended figures. In the figures:

[0019] FIG. 1 shows the structure and functioning of a vehicle control system in a block diagram.

[0020] FIG. 2 shows the structure and functioning of a vehicle control system in a block diagram.

[0021] FIG. 3 shows the structure and functioning of a vehicle control system in a block diagram.

DETAILED DESCRIPTION

[0022] In FIG. 1, the structure and the functioning of a vehicle control system 1 of a motor vehicle are indicated to the extent that it is necessary for understanding the invention. FIGS. 1 to 3 each show block diagrams the program modules of which do not reflect the actual software architecture of the vehicle control system 1 installed in the vehicle.

[0023] Thus, in FIG. 1, the vehicle control system 1 is in signal connection on the input side with an accelerator pedal 3 and a brake pedal 5. On the basis of the target specifications generated by the accelerator pedal 3 and/or the brake pedal 5, the vehicle control system 1 controls the wheel brakes 7 of a vehicle braking system and a drive unit 8 of the vehicle. An evaluation unit 9 is assigned to the vehicle control system 1. The evaluation unit 9 is in signal connection with wheel speed sensors 11, which are installed on both the front axle and the rear axle of the vehicle and detect the current wheel speed n. Based on the wheel speed n and the tire diameter d.sub.R of the standard tires 13 stored in the vehicle control system 1, the evaluation unit 9 determines a speed-based vehicle speed v(n) according to FIG. 3. In normal operation or onroad driving, the rpm-based vehicle speed v(n) forms a reference variable v.sub.reference, which is transmitted to the vehicle control system 1 in the block diagrams of FIG. 1 or 3. On the basis of the reference variable v.sub.reference, the vehicle control system 1 calculates manipulated variables with which different vehicle functions can be controlled. According to FIG. 2, such vehicle functions are an engine control, a transmission control, ABS, ESC, ASR, HillDescendControl and a component protection function, such as a drive/output shaft protection function.

[0024] The invention is based on the fact that the vehicle user, when using the motor vehicle on extreme offroad routes, changes the standard tires 13 to offroad tires 14, which are indicated by dashed lines on the front right vehicle wheel in FIG. 1. The onroad tires 14 have a significantly larger tire diameter (namely an onroad tire diameter d.sub.onroad) compared to the series tires 13, which results in a large tire diameter difference compared to the series tires 13. With such a large difference in tire diameter, the rpm-based vehicle speed v(n) determined based on the tire diameter d.sub.R (stored in the vehicle control system 1) of the standard tires 13 and based on the current wheel speed n deviates from the actual vehicle speed. Accordingly, the problem in the prior art is that the rpm-based vehicle speed v(n), which forms the reference variable, may not ensure optimal control of the vehicle functions.

[0025] Against this background, according to the invention, the evaluation unit 9 sets the GPS-based vehicle speed v.sub.GPS as the reference variable v.sub.reference instead of the rpm-based vehicle speed v(n), provided that both offroad driving and a tire change signal S.sub.U are present, which is generated when there is a significant tire diameter deviation between the offroad tires 14 and the standard tires 13.

[0026] The evaluation unit 9 operates with the program modules indicated in FIG. 3: Accordingly, a first determination module 15 is provided which compares a current GPS vehicle position with a road map data set 17 stored in the vehicle control system 1. On the basis of this comparison, the determination module 15 generates an offroad signal S.sub.offroad or an onroad signal S.sub.onroad. Alternatively and/or additionally, a user-operable offroad button 19 of a DriveSelect mode can be assigned to the first determination module 15. When the offroad button 19 is pressed, the vehicle control system 1 switches the vehicle functions to offroad driving mode. In addition, the first determination module 15 generates the offroad signal S.sub.offroad when the offroad button 19 is actuated, while the onroad signal S.sub.onroad is generated when the offroad button 19 is not actuated.

[0027] The evaluation unit 9 also has a second determination module 21. This generates the tire change signal S.sub.U if there is a significant speed difference v between the rpm-based vehicle speed v(n) and the GPS-based vehicle speed v.sub.GPS. The second determination module 21 is preceded by a calculation module 23 which calculates the rpm-based vehicle speed v(n) on the basis of the current wheel speed n and on the basis of the tire diameter d.sub.R of the standard tires 13 stored in the vehicle control system 1.

[0028] The two determination modules 15, 21 are in signal connection with a provision module 25, in which the following case distinction is made: If both an offroad signal S.sub.offroad and a tire change signal S.sub.U are present at the signal input of the provision module 25, the GPS-based vehicle speed v.sub.GPS is set as the reference variable v.sub.reference in the provision module 25. If an onroad signal S.sub.onroad and a tire change signal S.sub.U are present at the signal input of the provision module 25, the rpm-based vehicle speed v(n) is defined as the reference variable v.sub.reference. In addition, the vehicle user is informed via a display device 27 (FIG. 1) of a warning that the onroad vehicle tires do not comply with the approved specification.

[0029] If only an onroad signal S.sub.onroad is present at the signal input, but no tire change signal S.sub.U, the rpm-based vehicle speed v(n) is defined as the reference variable v.sub.reference. The same applies if only an offroad signal S.sub.offroad but no tire change signal S.sub.U is present at the provision module 25.

LIST OF REFERENCE NUMERALS

[0030] 1 vehicle control system [0031] 3 accelerator pedal [0032] 5 brake pedal [0033] 7 wheel brakes [0034] 8 drive unit [0035] 9 evaluation unit [0036] 11 wheel speed sensors [0037] 13 standard tires [0038] 14 offroad tires [0039] 15 first determination module [0040] 17 road map data-set [0041] 19 offroad button [0042] 21 second determination module [0043] 23 calculation module [0044] 25 provision module [0045] 37 display means [0046] v.sub.reference reference variable [0047] v(n) rpm-based vehicle speed [0048] v.sub.GPS GPS-based vehicle speed [0049] n current wheel speed [0050] S.sub.offroad offroad signal [0051] S.sub.onroad onroad signal [0052] S.sub.U tire change signal [0053] d.sub.R tire diameter of the standard tires 13 [0054] d.sub.offroad tire diameter of the offroad tires [0055] v speed difference [0056] FR direction of travel