Granted Patent B2

US 12,263,901 · App. 17/783,435 · Granted Apr 1, 2025

Inventors: Martin Muenster (Munich, DE); Martin Sedlmayr (Wessobrunn, DE)

Assignee: Bayerische Motoren Werke Aktiengesellschaft

B62D6/002B62D5/046B62D15/021

Abstract

Claims (43)

1. A method for controlling a rear-axle steering system of a vehicle having a steerable rear axle, comprising:

determining a present physical state of the rear-axle steering system based on a detected present operating state (A act ) and a predetermined reference operating state (A norm ) of the rear-axle steering system;

specifying a maximum permissible value of a steering angle (L max ) of the rear-axle steering system as a function of an estimated physical state of the rear-axle steering system and as a function of at least one of operating parameters driving speed (Vx), the steering angle (L) of the rear-axle steering system, and steering angle speed (VL) of the vehicle; and

activating the rear-axle steering system so that the steering angle (L) of the rear-axle steering system does not exceed an assigned specified maximum permissible value of the steering angle (L max ) with the operating parameter(s) (Vx,VL) of the vehicle.

2. The method according to claim 1 , wherein

the determination of the present physical state of the rear-axle steering system is carried out based on the present utilization (A act ) of a specified operating range of an actuator of the rear-axle steering system provided for its actuation.

3. The method according to claim 2 , wherein:

the reference operating state defines a reference utilization (A norm ) of the operating range and the determination of the present physical state of the rear-axle steering system is carried out based on a comparison (A act ) of the detected present utilization of the operating range of the actuator to the reference utilization (A norm ); and

the present utilization and the reference utilization (A norm ) are each related to same operating parameter(s) (Vx, VL, L) of the rear-axle steering system and same values thereof.

4. The method according to claim 3 , wherein:

the reference utilization (A norm ) represents an operating point on a characteristic curve or a multidimensional characteristic curve surface for the utilization of the actuator, which is related to the operating range; and

for each operating point (Vx, VL, L) on this characteristic curve or characteristic curve surface, the actuator ensures a reset of the rear axle from a position corresponding to a steering angle (L) not equal to zero into a non-deflected position, while the actuator no longer ensures this for every utilization above this characteristic curve or this characteristic curve surface.

5. The method according to claim 1 , wherein

the determination of the present physical state of the rear-axle steering system is carried out via an automatic learning process based on a repeated determination of a respective present operating state of the rear-axle steering system at various operating times (t).

6. The method according to claim 5 , wherein the automatic learning process comprises at least one of the following steps:

(i) averaging over detected operating states at various operating times; or

(ii) a running maximum value formation, in which a present value of a physical state of the rear-axle steering system is set as a respective maximum value of at least two values.

7. The method according to claim 1 , wherein the maximum permissible value of the steering angle (L max ) of the rear-axle steering system for a speed corresponding to a standstill of the vehicle is set to a value greater than zero if, based on the determination of the present physical state of the rear-axle steering system, a result of the determination is that a return of the rear axle from a position corresponding to the steering angle, different from zero, to a non-deflected position is possible even when the vehicle is at the standstill.

8. The method according to claim 7 , wherein

the prediction based on the determination of the present physical state of the rear-axle steering system as to whether a reset of the rear axle from the position corresponding to the steering angle not equal to zero into a non-deflected position is also possible at a standstill of the vehicle is carried out based on a comparison of the estimated present physical state to a predefined limiting value, which corresponds to a best possible physical state or is below the best possible physical state.

9. The method according to claim 2 , wherein

the present utilization (A act ) of the rear-axle steering system is determined based on one of an actual current consumption (I act ), actual power consumption, actual supply voltage in comparison to a maximum possible current consumption, power consumption, or supply voltage.

10. The method according to claim 1 , wherein

restriction of the maximum permissible value of the steering angle (L max ) as a function of the present physical state of the rear-axle steering system only takes place for operating states of the rear-axle steering system from a selected partial range of an operating range, which corresponds to one or more of a vehicle speed (Vx), a steering angle speed (VL), the steering angle (L) of the rear-axle steering system, each below a predetermined associated limiting threshold.

11. The method according to claim 1 , wherein the maximum permissible steering angle of the rear-axle steering system is additionally specified in one of the following ways:

(i) as a function of a direction of change of the driving speed (Vx) of the vehicle, of a sign of the steering angle speed (VL), or as to whether a distance has already been covered since a last vehicle stop;

(ii) as a function of a detected present demand intensity (B) with respect to the steering of the vehicle; or

(iii) an operating parameter-dependent curve of the maximum permissible value of the steering angle (L max ) in the operating range corresponds to an iso-force characteristic curve with respect to an occurring steering force on the rear-axle steering system at the maximum permissible steering angle (L).

12. The method according to claim 1 , further comprising at least one of the following measures:

limiting of the steering angle (L) of the rear-axle steering system to the maximum permissible value of the steering angle (L max ) during the activation of the rear-axle steering system is only applied if the steering angle (L) of the rear-axle steering system exceeds a defined minimum deflection; or

specifying a maximum steering angle speed (VL) applied by the actuator for the rear-axle steering system as a function of the present driving speed (Vx) of the vehicle.

13. A device for controlling a rear-axle steering system of a vehicle having a steerable rear axle, comprising:

a processor-based control unit operatively configured to:

determine a present physical state of the rear-axle steering system based on a detected present operating state (A act ) and a predetermined reference operating state (A norm ) of the rear-axle steering system;

specify a maximum permissible value of the steering angle (L max ) of the rear-axle steering system as a function of an estimated physical state of the rear-axle steering system and as a function of at least one of operating parameters driving speed (Vx), steering angle (L), and steering angle speed (VL) of the vehicle; and

activate the rear-axle steering system so that the steering angle (L) of the rear-axle steering system does not exceed an assigned specified maximum permissible value of the steering angle (L max ) with the present operating parameter(s) (Vx, VL) of the vehicle.

14. A vehicle comprising:

a steerable rear axle; and

a device according to claim 13 for controlling the steerable rear axle.

15. A computer product comprising a non-transitory computer readable medium having stored thereon program code which, upon execution by a processor, carries out the acts of:

determining a present physical state of the rear-axle steering system based on a detected present operating state (A act ) and a predetermined reference operating state (A norm ) of the rear-axle steering system;

specifying a maximum permissible value of a steering angle (L max ) of the rear-axle steering system as a function of the estimated physical state of the rear-axle steering system and as a function of at least one of operating parameters driving speed (Vx), steering angle (L), and steering angle speed (VL) of the vehicle; and

activating the rear-axle steering system so that the steering angle (L) of the rear-axle steering system does not exceed an assigned specified maximum permissible value of the steering angle (L max ) with the present operating parameter(s) (Vx, VL) of the vehicle.

Assignments (1)

Priority Claims (1)

Continuity (1)

References Cited (34)