Device and method for coordinating target steering angles of a vehicle, the device comprising a vehicle

Abstract

Device and method for coordinating target steering angles of a vehicle, wherein a target value for a yaw moment, yaw rate or yaw acceleration of the vehicle is specified (302), wherein a first actual steering angle is influenced by a first target steering angle, wherein a second actual steering angle is influenced by a second target steering angle, wherein the first target steering angle is determined depending on the target value and the second actual steering angle (304), wherein the second target steering angle is determined depending on the target value and the first actual steering angle (304), wherein the first target steering angle is corrected with a specified first weighting factor (306), wherein the second target steering angle is corrected with a specified second weighting factor (306).

Description

State of the art

[0001] The invention relates to a device and a method for coordinating target steering angles of a vehicle and a vehicle comprising the device.

[0002] Modern vehicle dynamics control systems now offer the possibility of influencing the steering angle of the rear axle (RWS) using rear-axle steering and at the front axle using steer-by-wire (SbW); the same applies to individual wheel steering systems. Separate logic is used for SbW and RWS, as well as for individual wheel steering systems. Disclosure of the invention

[0003] A method for coordinating the target steering angles of a vehicle provides that a target value for a yaw moment, yaw rate, or yaw acceleration of the vehicle is specified, wherein a first actual steering angle is influenced by a first target steering angle, wherein a second actual steering angle is influenced by a second target steering angle, wherein the first target steering angle is determined depending on the target value and the second actual steering angle, wherein the second target steering angle is determined depending on the target value and the first actual steering angle, wherein the first target steering angle is corrected with a specified first weighting factor, and wherein the second target steering angle is corrected with a specified second weighting factor.

[0004] The targeted coordination enables simple, individual weighting between the vehicle's actuators that determine the target steering angles, without altering the physical effect, such as the vehicle's movement. Furthermore, the weighting can be applied to only one actuator if only one actuator is available or intended for use. This has the advantage that the same solution can be used for different steering concepts. For example, if only one actuator is available in some vehicle variants and only the other in others, the same software with the corresponding weighting can still be used.

[0005] In a vehicle with front-axle and rear-axle steering, it may be provided that the first target steering angle and the first actual steering angle are front-axle steering angles, with the second target steering angle and the second actual steering angle being rear-axle steering angles, or that the first target steering angle and the first actual steering angle are rear-axle steering angles, with the second target steering angle and the second actual steering angle being front-axle steering angles.

[0006] In a vehicle with independent wheel steering, it may be provided that the first target steering angle and the first actual steering angle are wheel steering angles of a first wheel of the independent wheel steering, wherein the second target steering angle and the second actual steering angle are wheel steering angles of a second wheel of the independent wheel steering.

[0007] In a vehicle where the independent steering system comprises two individually steered wheels on a front axle and two individually steered wheels on a rear axle, it may be provided that a third actual steering angle of a third wheel is influenced by a third target steering angle, wherein a fourth actual steering angle of a fourth wheel is influenced by a fourth target steering angle, wherein the first target steering angle is determined depending on the target value and the second actual steering angle, the third actual steering angle, and the fourth actual steering angle, wherein the second target steering angle is determined depending on the target value and the first actual steering angle, the third actual steering angle, and the fourth actual steering angle, wherein the third target steering angle is determined depending on the target value and the first actual steering angle, the second actual steering angle, and the fourth actual steering angle.wherein the fourth target steering angle is determined depending on the target value and the first actual steering angle, the second actual steering angle and the third actual steering angle, wherein the third target steering angle is corrected with a predetermined third weighting factor, wherein the fourth target steering angle is corrected with a predetermined fourth weighting factor.

[0008] For example, weighting factors between zero and one are determined or specified, with the sum of all weighting factors equaling one. Regardless of the weighting, this ensures that the vehicle behaves according to the target value as long as the steering angles are implemented as expected.

[0009] It may be possible to determine or change the weighting factors depending on the runtime and / or the situation. This means that the weighting is adapted situationally, e.g., depending on the currently available actuator potentials over the runtime or to the situation.

[0010] It may be intended that the target value is determined by the driver or an assistance system, depending on the driver's steering angle. For example, the assistance system could be a crosswind assist or a lane keeping assist.

[0011] It may be provided that a model is used to determine the actual value of the yaw moment, yaw rate, or yaw acceleration of the vehicle, depending on the actual steering angles and the target value, whereby the respective target steering angle is determined using the model inverted to calculate the respective target steering angle. Regardless of the type of model, this achieves vehicle behavior according to the target value as long as the steering angles are implemented as expected and the model is chosen with sufficient accuracy.

[0012] For example, the model includes a single-track model or a two-track model of the vehicle.

[0013] A device for coordinating target steering angles of a vehicle provides that the device is designed to execute the procedure.

[0014] A vehicle design includes the device for coordinating the vehicle's target steering angles.

[0015] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows: Fig. 1 a schematic representation of a vehicle, Fig. 2 a block diagram of a coordination of target steering angles of the vehicle, Fig. 3. A flowchart showing the steps of a procedure for coordinating the target steering angles of the vehicle.

[0016] In Fig. Figure 1 schematically depicts a vehicle 100 with a device 102 for coordinating the target steering angles of the vehicle 100. The device 102 is configured to execute a method for coordinating the target steering angles of the vehicle 100.

[0017] The device 102 is described using the example of the coordination between a first target steering angle δ FASoll for a front axle steering system 104 and a second target steering angle δ RASolldescribed for a rear axle steering system 106 of the vehicle 100.

[0018] In Fig. 2 is a block diagram of the coordination between the first target steering angle δ FASoll and the second target steering angle δ RASoll The block diagram schematically represents an exemplary structure of part of the device 102.

[0019] The coordination is based on a weighting of 202 between the first target steering angle δ FASoll and the second target steering angle δ RASoll As a result of the coordination, a coordinated first target steering angle δ is obtained. FAsoll,koord and a coordinated second target steering angle δ RASoll,koord issued.

[0020] The first target steering angle δ FASoll is determined with a first target steering angle δ FASoll first invert vehicle model 204 depending on a setpoint M ZSoll certainly.

[0021] The second target steering angle δ RASollis determined with a first target steering angle δ FASoll Invert vehicle model 206 depending on the target value M ZSoll certainly.

[0022] The target value M ZSoll In the example, a target driver model 208 is used, depending on a driver steering angle δ specified by a real driver 210. Drvr or determined by an assistance system 212. A switch between the setpoint M ZSoll from the driver target model 208 and the target value M ZSoll The assistance system 212 is activated, for example, by a switch 214.

[0023] The first inverted vehicle model 204 and the second inverted vehicle model 206, for example, are based on a vehicle model f v : Mz=fv(δFA,δRA) where M z the yaw moment of the vehicle about the vertical vehicle axis, δ FA the front axle steering angle, δ RA represents the rear axle steering angle. The vehicle model f vIt can be a single-track model or a dual-track model. The dual-track model allows for the consideration of disturbances caused by differing friction on the two wheels of the same axle of the vehicle.

[0024] The first inverted vehicle model 204 is, for example: δFAsoll=f1,v−1(MZsoll,δRAactual)

[0025] The second inverted vehicle model 206 is, for example: δRAset=f1,v−1(MZset,δFAactual) where M ZSoll a yaw moment, δ RAist the actual steering angle of the rear axle steering and δ FAist represents the actual steering angle of the front axle steering.

[0026] Instead of relying on the yaw moment, the vehicle model can f v also based on a yaw rate or yaw acceleration, which determines the yaw rate or yaw acceleration depending on the front axle steering angle and the rear axle steering angle.

[0027] In the case of independent wheel steering, it may be provided that the vehicle model f v the yaw moment, yaw rate or yaw acceleration is determined depending on the individual wheel steering angles.

[0028] If inverting a vehicle model is not possible, the model may be made invertible by simplifications (e.g., small-angle approximation), which have only minor effects and are negligible.

[0029] Weighting 202, for example, provides for a first weighting factor i and a second weighting factor (1 - i). For example, it is provided that the coordinated first target steering angle δ FASoll,koord is determined depending on the first weighting factor i. For example, the coordinated first target steering angle δ FASoll,koord as determined as follows: δFASoll,koord=δFASoll*i

[0030] For example, it is provided that the coordinated second target steering angle δFASoll,koord is determined depending on the second weighting factor (1 - i). For example, the coordinated second target steering angle δ RASoll,koord as determined as follows: δRASoll,koord=δRASoll*(1−i)

[0031] This means that the yaw response of vehicle 100 is the same regardless of the chosen weighting factor i, (1 - i) if the respective target steering angles are set precisely and the vehicle model f v exactly.

[0032] In the example, the weighting factors i, (1 - i) are chosen between zero and one.

[0033] In Fig. Figure 3 shows a flowchart with steps of a procedure for coordinating the target steering angles of the vehicle.

[0034] The procedure includes step 302.

[0035] In step 302, the target value is specified. The target value depends, for example, on the driver's steering angle δ. Drvrdetermined by the driver 210 or the assistance system 212.

[0036] The procedure includes step 304.

[0037] In step 304, the target steering angles are determined.

[0038] For example, the vehicle model f v provided. For example, the target steering angles are determined using a respective inverted vehicle model.

[0039] For the coordination between the front axle steering angle and the rear axle steering angle, the first target steering angle is determined based on the target value and the second on the actual steering angle. For the target yaw moment M ZSoll The front axle steering angle and the rear axle steering angle are determined, for example, as follows: δFASoll=f1,v−1(MZSoll,δRAactual) δRASoll=f1,v−1(MZSoll,δFAactual)

[0040] For the coordination between front axle steering angle and rear axle steering angle, the second target steering angle is determined depending on the target value and the first actual steering angle.

[0041] The coordination between individual wheel steering angles of the individual wheel steering system is carried out accordingly.

[0042] This is described using the example of two individually steered wheels on a front axle and two individually steered wheels on a rear axle: With independent wheel steering, a first actual steering angle of a first wheel is influenced by a first target steering angle, a second actual steering angle of a second wheel is influenced by a second target steering angle, a third actual steering angle of a third wheel is influenced by a third target steering angle, A fourth actual steering angle of a fourth wheel is influenced by a fourth target steering angle.

[0043] The first target steering angle is determined depending on the target value, the second actual steering angle, the third actual steering angle, and the fourth actual steering angle.

[0044] The second target steering angle is determined depending on the target value and the first actual steering angle, the third actual steering angle, and the fourth actual steering angle.

[0045] The third target steering angle is determined depending on the target value and the first actual steering angle, the second actual steering angle, and the fourth actual steering angle.

[0046] The fourth target steering angle is determined depending on the target value and the first actual steering angle, the second actual steering angle, and the third actual steering angle.

[0047] The procedure includes step 306.

[0048] In step 306, the target steering angles are corrected.

[0049] The first target steering angle δ is used for the coordination between the front axle steering angle and the rear axle steering angle. FASollwith the first weighting factor i and the second target steering angle δ RASoll corrected with the second weighting factor (1 - i).

[0050] For the coordination between individual wheel steering angles of the individual wheel steering system, the first target steering angle is corrected with a first weighting factor, the second target steering angle with a second weighting factor, the third target steering angle with a third weighting factor, and the fourth target steering angle with a fourth weighting factor.

[0051] The weighting factors are determined or specified, for example, between zero and one.

[0052] The weighting factors are determined or specified, for example, between zero and one, such that the sum of the weighting factors equals one.

[0053] It may be provided that the weighting factors are determined or changed depending on a duration and / or depending on a situation.

Claims

[1] Method for coordinating the target steering angles of a vehicle, characterized by , that a setpoint for a yaw moment, yaw rate or yaw acceleration of the vehicle is specified (302), wherein a first actual steering angle is influenced by a first setpoint steering angle, wherein a second actual steering angle is influenced by a second setpoint steering angle, wherein the first setpoint steering angle is determined depending on the setpoint and the second actual steering angle (304), wherein the second setpoint steering angle is determined depending on the setpoint and the first actual steering angle (304), wherein the first setpoint steering angle is corrected with a specified first weighting factor (306), wherein the second setpoint steering angle is corrected with a specified second weighting factor (306). [2] Method according to claim 1, characterized by, that the first target steering angle and the first actual steering angle are front axle steering angles, wherein the second target steering angle and the second actual steering angle are rear axle steering angles, or that the first target steering angle and the first actual steering angle are rear axle steering angles, wherein the second target steering angle and the second actual steering angle are front axle steering angles. [3] Method according to claim 1, characterized by , that the first target steering angle and the first actual steering angle are wheel steering angles of a first wheel of a single-wheel steering system, wherein the second target steering angle and the second actual steering angle are wheel steering angles of a second wheel of the single-wheel steering system. [4] Method according to claim 3, characterized by, that the individual wheel steering comprises two individually steered wheels on a front axle and two individually steered wheels on a rear axle, wherein a third actual steering angle of a third wheel is influenced by a third target steering angle, wherein a fourth actual steering angle of a fourth wheel is influenced by a fourth target steering angle, wherein the first target steering angle is determined depending on the target value and the second actual steering angle and the third actual steering angle and the fourth actual steering angle (304), wherein the second target steering angle is determined depending on the target value and the first actual steering angle and the third actual steering angle and the fourth actual steering angle (304), wherein the third target steering angle is determined depending on the target value and the first actual steering angle and the second actual steering angle and the fourth actual steering angle (304),wherein the fourth target steering angle is determined depending on the target value and the first actual steering angle and the second actual steering angle and the third actual steering angle (304), wherein the third target steering angle is corrected with a predetermined third weighting factor (306), wherein the fourth target steering angle is corrected with a predetermined fourth weighting factor (306). [5] Method according to any one of the preceding claims, characterized by , that the weighting factors are determined or specified between zero and one (306), where a sum of the weighting factors equals one. [6] Method according to any one of the preceding claims, characterized by , that the weighting factors are determined or changed depending on a duration and / or depending on a situation (306). [7] Method according to any of the preceding claims, characterized by, that the target value is determined by a driver or an assistance system depending on a driver steering angle (302). [8] Method according to any one of the preceding claims, characterized by , that a model is provided with which an actual value for the yaw moment, yaw rate or yaw acceleration of the vehicle can be determined depending on the actual steering angles and the target value, wherein the respective target steering angle is determined with the model inverted to calculate the respective target steering angle (304). [9] Method according to claim 8, characterized by that the model includes a single-track model or a two-track model of the vehicle. [10] Device (102) for coordinating target steering angles of a vehicle (100), characterized by , that the device (102) is configured to carry out the method according to any one of claims 1 to 9. [11] Vehicle (100), characterized by, that the vehicle (100) comprises the device (102) for coordinating target steering angles of the vehicle (100) according to claim 10.

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