Method for securing change in variable steering gear ratio in steering system

Abstract

The invention relates to a method for securing a change in a variable steering gear ratio in a steering system (10), in particular during operation of the steering system (10) in a vehicle (12), wherein the steering system (10) is designed as a steer-by-wire system and comprises an operating unit (12) having at least one steering handle (14) and at least one wheel steering angle adjuster (18) operatively connected to the operating unit (12) for changing a wheel steering angle of at least one wheel (20), and wherein the variable steering gear ratio defines an adaptable transmission ratio between the steering specification on the steering handle (16) and the wheel steering angle of the wheel (20). According to the invention, a change in the variable steering gear ratio is limited by means of a dynamically ascertained change variable (40).

Description

Technical Field

[0001] This invention relates to a method for ensuring the variation of a variable steering ratio in a steering system. Furthermore, this invention relates to a computing unit for implementing such a method and a vehicle having such a computing unit. Background Technology

[0002] Vehicles with conventional steering systems are known from the prior art, where a steering handle, for example in the form of a steering wheel, is mechanically and fixedly connected via a steering column to a wheel steering angle adjuster, which is in the form of a steering transmission mechanism. Furthermore, vehicles with steer-by-wire systems are known, which are sufficient without a direct mechanical connection between the steering handle and the wheel being steered, and for which steering presets are transmitted solely electrically. Such steer-by-wire systems typically include an operating unit with a steering handle and a feedback actuator, and at least one wheel steering angle adjuster mechanically separate from the operating unit, which can be configured, for example, as a central adjuster or a single wheel adjuster.

[0003] The advantage of such a steer-by-wire system is that the transmission ratio, or the ratio between the steering gear preset on the steering handle and the wheel steering angle, can be changed depending on driving conditions, such as the steering angle and vehicle speed. Therefore, a more indirect transmission ratio can be achieved, for example, at higher vehicle speeds than at lower speeds, resulting in better driving performance. An example of such a steer-by-wire system with a variable steering ratio is described in DE 102017220803 B4.

[0004] However, one challenge lies in ensuring the stability of the variable steering ratio, as limiting it with fixed values ​​as currently used would introduce different problems. Summary of the Invention

[0005] From this perspective, the objective of this invention is particularly to provide a method for ensuring improved efficiency in response to variations in the variable steering ratio. This objective is achieved through the features of claims 1, 8, and 9, while advantageous designs and improvements of the invention can be gleaned from the dependent claims.

[0006] Disclosure of this invention

[0007] This invention begins with a method, particularly a computer-implemented method, for ensuring a variable steering ratio in a steering system, especially during operation of a steering system in a vehicle. The steering system is configured as a steer-by-wire system and includes an operating unit with at least one steering handle and at least one wheel steering angle adjuster operatively connected to the operating unit for changing the wheel steering angle of at least one wheel. The variable steering ratio defines a transmission ratio between a steering preset on the steering handle and the wheel steering angle, which is particularly dynamic and / or adaptable to driving conditions. The steering ratio can hereby be changed, for example, depending on the steering preset, particularly the dynamic and / or absolute value of the steering preset and / or depending on vehicle speed, and thus can be variably adapted.

[0008] It is proposed here that the variation of the variable steering ratio be limited by means of dynamically determined characteristic parameters. According to the invention, the characteristic parameters are thus variably configured and therefore dynamically adaptable. Particularly preferred is that the variation of the variable steering ratio is performed in this regard using a variation factor, wherein the variation factor is limited by means of the characteristic parameters. With this design, efficiency, especially power efficiency and / or operational efficiency, can be improved. In particular, the adaptable limitation of the variation of the steering ratio can improve operational reliability and simultaneously achieve improved effective power or performance. Furthermore, the situation-dependent adaptation of the characteristic parameters can particularly prevent wheel movement when the steering handle deflection remains constant and the variation factor changes, such as during vehicle acceleration or when the variation factor changes with respect to vehicle speed. Furthermore, it is advantageous to reliably and efficiently switch from a first steering ratio to a second steering ratio.

[0009] The steering system is currently configured as a steer-by-wire system, in which the driver's steering preset is advantageously transmitted to the wheels in a purely electric manner. A "wheel steering angle adjuster" should specifically refer to an adjustment unit mechanically separate from the operating unit and coupled to at least one wheel, which is configured to transmit the driver's steering preset, in particular, to the wheel through changes in the wheel steering angle of at least one wheel, thereby advantageously controlling at least the wheel's orientation and / or influencing the vehicle's direction of travel. For this purpose, the wheel steering angle adjuster advantageously includes at least one steering adjustment element, for example, in the form of a rack, and at least one steering actuator, for example, in the form of an electric motor, operatively connected to the steering adjustment element. The wheel steering angle adjuster can here be configured as a central adjuster and distributed to at least two wheels, particularly steerable and preferably front wheels. However, as an alternative, the wheel steering angle adjuster can also be configured as a single-wheel adjuster and distributed to exactly one wheel, particularly steerable and preferably front wheel. Furthermore, "steering ratio" should refer to a particularly virtual transmission ratio between the operating unit and the wheel steering angle adjuster, which defines the relationship between the steering preset on the steering handle and the wheel steering angle. Therefore, the steering ratio affects how the deflection or return of the steering handle affects the deflection or return of the wheels. Thus, a first steering ratio may provide, for example, a more direct or simpler steering performance, while a second steering ratio may provide, for example, a more indirect or less simple steering performance.

[0010] Furthermore, the vehicle includes at least one computing unit configured to implement methods for ensuring changes in the variable steering ratio. "Computing unit" should particularly refer to an electrical and / or electronic unit having an information input terminal, an information processing mechanism, and an information output terminal. Furthermore, the computing unit advantageously has at least one processor, at least one operating memory, at least one input and / or output device, at least one operating program, at least one control and / or regulation routine, at least one calculation routine, at least one determination routine, at least one adaptation routine, and / or at least one limiting routine. In particular, the computing unit is at least configured to limit changes in the variable steering ratio, particularly by means of a limiting routine, by means of dynamically determined changing characteristic parameters. Furthermore, the computing unit can be configured to determine changing characteristic parameters, particularly by means of a determination routine, and / or to change and / or modify the steering ratio between the operating unit and the wheel steering angle adjuster, particularly by means of an adaptation routine. Preferably, the computing unit is integrated into the vehicle's control equipment, such as a central vehicle control device or a steering system control device. "Configured" should particularly refer to being specifically programmed, designed, and / or equipped. "An object is set up for a specific function" should in particular mean that the object performs and / or executes such a specific function in at least one application and / or operating state.

[0011] Furthermore, it is advantageously suggested that the temporal gradient be used as a variable characteristic parameter. Preferably, the dynamically adaptable gradient is used to limit changes in the steering ratio, and particularly preferably to limit the variation factor. Thus, protection against changes in the variable steering ratio is achieved by means of limiting the variable temporal gradient. Consequently, protection against changes in the steering ratio can be achieved, which is advantageously easy from a controllable perspective.

[0012] Furthermore, it is recommended to dynamically identify and / or especially calculate the changing characteristic parameters, relying on the current steering preset on the steering handle, particularly the dynamic and / or absolute values ​​of the steering preset. When the steering wheel is used as a steering handle, the dynamics of the steering preset can correspond particularly to the steering speed or steering angular velocity of the steering handle. When the steering wheel is used as a steering handle, the absolute value of the steering preset can correspond particularly to the deflection or steering angle of the steering handle. Thus, it is particularly possible to advantageously and dynamically identify the changing characteristic parameters, or to do so in a context-dependent manner.

[0013] Especially high performance and / or operational reliability can be achieved if the variable characteristic parameter is determined by relying on at least two sub-characteristic parameters, wherein the first sub-characteristic parameter is determined by the steering handle deflection and the second sub-characteristic parameter is determined by at least the steering handle speed. Preferably, in this case, the variable characteristic parameter is determined by the maximum value of the first and second sub-characteristic parameters. In principle, the maximum value can also be directly used as the variable characteristic parameter. Furthermore, the steering handle deflection can also be taken into account when determining the second sub-characteristic parameter if necessary. Currently, the second sub-characteristic parameter can thus preferably be determined by relying solely on the steering handle speed or by relying on both the steering handle deflection and the steering handle speed. If the temporal gradient is used as the variable characteristic parameter, the first sub-characteristic parameter can also advantageously correspond to the minimum gradient, while the second sub-characteristic parameter can correspond to the maximum gradient.

[0014] As an alternative, it is suggested that, when using a characteristic field, the varying characteristic parameters be identified, which describes the steering wheel deflection at least with respect to the steering speed of the steering wheel. This characteristic field can preferably be applied in advance and, for example, stored in the vehicle's runtime memory. If the temporal gradient is used as the varying characteristic parameter, then the 3D characteristic field can be advantageously used for gradient constraint.

[0015] This allows for the advantageous and easy identification of changing characteristic parameters. Furthermore, it reduces the required computational resources.

[0016] The method for ensuring the variation of the variable steering ratio and the vehicle described herein should not be limited to the applications and implementations described above. In particular, the method for ensuring the variation of the variable steering ratio and the vehicle described herein can have a different number of individual elements, components, and units than those described herein in order to fulfill the operating principle described herein. Attached Figure Description

[0017] Other advantages will become apparent from the following description of the accompanying drawings. One embodiment of the invention is illustrated in the drawings.

[0018] in:

[0019] Figure 1a -b illustrates a vehicle with a steering system configured as a steer-by-wire system in a simplified diagram;

[0020] Figure 2 A signal flow diagram is shown to ensure the variation of the variable steering ratio in the steering system; and

[0021] Figure 3An exemplary flowchart is shown, illustrating the main method steps of a method for ensuring the variation of the variable steering ratio in a steering system. Detailed Implementation

[0022] Figure 1a and 1b A simplified illustration shows a vehicle 12, exemplaryly constructed as a sedan, having a plurality of wheels 20 and a steering system 10. The steering system 10 is operatively connected to the wheels 20 and configured to influence the direction of travel of the vehicle 12. Furthermore, the steering system 10 is currently configured as a steer-by-wire system, for which steering is electrically transmitted to the wheels 20 in at least one operating state.

[0023] The steering system 10 has an operating unit 14, which is particularly operable by the driver and / or occupants. The operating unit 14 includes, for example, a steering handle 16 in the form of a steering wheel and a feedback actuator 24 mechanically coupled to the steering handle 16. The feedback actuator 24 is configured to provide a feedback torque and thereby generate steering resistance and / or a restoring torque acting on the steering handle 16. Alternatively, the steering handle can also be configured as a lever, steering column, and / or steering ball, etc.

[0024] Furthermore, the steering system 10 includes a wheel steering angle adjuster 18. The wheel steering angle adjuster 18 is mechanically separate from the operating unit 14. The wheel steering angle adjuster 18 is electrically connected to the operating unit 14. Furthermore, the wheel steering angle adjuster 18 is currently configured as a central adjuster. The wheel steering angle adjuster 18 has an operative connection with at least two wheels of the wheels 20, particularly the two front wheels, and is configured to convert a steering preset into steering motion of the wheels 20. For this purpose, the wheel steering angle adjuster 18 includes a steering adjustment element 26, particularly in the form of a rack, and a steering actuator 28, particularly in the form of an electric motor, that cooperates with the steering adjustment element 26. In principle, the steering system can also include multiple wheel steering angle adjusters, particularly configured as single-wheel adjusters. Furthermore, the steering actuator can be configured as a linear drive and / or include multiple electric motors.

[0025] Furthermore, vehicle 12 has a control device 30. In its current form, control device 30 is configured as a steering control device and is therefore part of steering system 10. Control device 30 has an electrical connection to wheel steering angle adjuster 18. Control device 30 also has an electrical connection to operating unit 14. Control device 30 is at least configured to control the operation of steering system 10. For this purpose, control device 30 includes a computing unit 22. Computing unit 22 includes at least one processor (not shown), for example, in the form of a microprocessor, and at least one runtime memory (not shown). Furthermore, computing unit 22 includes at least one running program stored in runtime memory, the running program having at least one control routine, at least one calculation routine, at least one detection routine, at least one adaptation routine, and at least one restriction routine. However, in principle, the control device can also differ from the steering control device and, for example, be configured as a single, central vehicle control device with a central computing unit. Furthermore, it is conceivable to provide separate control devices and / or computing units for wheel steering angle adjusters and operating units and to connect them communicatively to each other.

[0026] The advantage of the current steering system 10 is that the transmission ratio between the steering gear ratio, or the steering preset on the steering handle 16, and the wheel steering angle of the wheel 20, can be changed according to driving conditions, such as the deflection of the steering handle 16 and the vehicle speed. This variable steering gear ratio is a degree of freedom that does not exist in conventional steering systems. Therefore, a more indirect gear ratio can be achieved, for example, at higher vehicle speeds than at lower vehicle speeds, resulting in better driving performance.

[0027] At the same time, it is necessary to ensure that the variable steering ratio can be varied by a corresponding factor. To this end, for example, the variation of the variable steering ratio or factor can be limited by a characteristic parameter that varies in the form of a fixed, time-varying gradient.

[0028] However, limiting the steering ratio using a fixed time gradient has the following drawback: to ensure the factor, this gradient must be chosen very low. This reliably low gradient so drastically reduces the performance of the variable steering ratio that a high gradient cannot be achieved depending on the deflection of the steering handle 16. Furthermore, by using a fixed time gradient, it is impossible to prevent the movement of the wheels 20 when the deflection of the steering handle 16 remains constant but the factor changes, such as when the factor changes with respect to vehicle speed.

[0029] Therefore, to improve efficiency, an improved method for ensuring the variation of the variable steering ratio in the steering system 10 is proposed below. Currently, in particular, the computing unit 22 is configured to execute the method and has a computer program with corresponding program code segments for this purpose. However, in principle, other computing units, such as the computing unit of a central vehicle control device, can also be configured to implement the method.

[0030] According to the present invention, instead of using a fixed value, the variation of the variable steering ratio is limited by a dynamically determined characteristic parameter 40 (especially referring to...). Figure 3 The preferred variation of the variable steering ratio is performed using variation factors 42 and 42', which are constrained by means of a variation characteristic parameter 40. Currently, the calculation unit 22 includes a constraint block 54 to which unconstrained variation factors 42 and dynamically determined variation characteristic parameters 40 are fed, and the constraint block determines, from the fed parameters, a dynamically constrained variation factor 42' for the variable steering ratio. Therefore, the variation characteristic parameter 40 is variably configured and can be dynamically adapted, for example, depending on the current driving and / or steering conditions.

[0031] In the current case, the temporal gradient is used as the variation feature parameter 40, so that the dynamically adaptable temporal gradient constraint is used to limit the variation of the steering gear ratio and, in particular, to limit the variation factors 42, 42'.

[0032] Furthermore, the changing characteristic parameter 40 is dynamically calculated based on the current steering preset on the steering handle 16, and in the current case, particularly on the deflection 50 and steering speed 52 of the steering handle 16. Here, for example, the changing characteristic parameter 40 can be determined using two sub-characteristic parameters 46 and 48. The first sub-characteristic parameter 46 is determined by means of the first calculation block 56 and based on the deflection 50 of the steering handle 16, while the second sub-characteristic parameter 48 is determined by means of the second calculation block 58 and based at least on the steering speed 52 of the steering handle 16. The first sub-characteristic parameter 46 advantageously corresponds to the minimum gradient, while the second sub-characteristic parameter 48 uses the maximum gradient. The two sub-characteristic parameters 46 and 48 are then fed to the conversion block 60, which determines the changing characteristic parameter 40 based on the maximum value of the first sub-characteristic parameter 46 and the second sub-characteristic parameter 48. In the current case, the maximum value is used directly for time-based gradient constraints, as exemplarily. However, in principle, the second sub-feature parameter can also be determined based on the steering handle deflection and steering speed. Furthermore, it is conceivable that, alternatively, the varying feature parameter can be determined using a characteristic curve field that at least depicts the steering handle deflection with respect to the steering handle's steering speed, thus allowing the 3D characteristic curve field to be used for gradient constraints in principle.

[0033] at last, Figure 3 An exemplary flowchart is shown, which has the main method steps for ensuring the variation of the variable steering gear ratio.

[0034] In method step 70, for example, the variable characteristic parameter 40 is determined by relying on the deflection 50 of the steering handle 16 and the steering speed 52 of the steering handle 16.

[0035] In method step 72, the variation of the variable steering ratio is limited by means of dynamically determined characteristic parameter 40, and currently, in particular, the variation factors 42 and 42' used for this purpose are limited. This improves operational reliability, especially when the variation factors 42 and 42' are provided by a third party or by external sensing devices and / or external control equipment, and simultaneously achieves improved effective power or performance. Furthermore, by adapting the characteristic parameter 40 to specific scenarios, wheel 20 movement can be prevented during acceleration, especially when the variation factors 42 and 42' change in such driving conditions.

[0036] Figure 3The flowchart in the document should merely exemplify one method for ensuring the variation of the variable steering ratio. In particular, the individual method steps can be varied and additional method steps can be added. For example, it is conceivable that the variation characteristic parameter 40 is determined based on at least two sub-characteristic parameters 46, 48, wherein the first sub-characteristic parameter 46 of the sub-characteristic parameters 46, 48 is determined based on the deflection 50 of the steering handle 16 and the second sub-characteristic parameter 48 of the sub-characteristic parameters 46, 48 is determined based at least on the steering speed 52 of the steering handle 16, or the variation characteristic parameter is determined using a characteristic curve field depicting at least the deflection of the steering handle with respect to the steering speed of the steering handle.

Claims

1. A method for ensuring a variable steering ratio change in a steering system (10) during operation, particularly in a vehicle (12), wherein the steering system (10) is configured as a steer-by-wire system and includes an operating unit (12) with at least one steering handle (14) and at least one wheel steering angle adjuster (18) operatively connected to the operating unit (12) for changing the wheel steering angle of at least one wheel (20), and wherein the variable steering ratio defines an adaptable transmission ratio between a steering preset on the steering handle (16) and the wheel steering angle of the wheel (20), characterized in that, The variation of the variable steering ratio is limited by using dynamically determined characteristic parameters (40).

2. The method according to claim 1, characterized in that, The variable steering ratio is changed using a variation factor (42, 42') and the variation factor (42, 42') is limited by a variation characteristic parameter (40).

3. The method according to claim 1 or 2, characterized in that, The temporal gradient is used as a characteristic parameter (40).

4. The method according to any one of the preceding claims, characterized in that, The changing characteristic parameter (40) is dynamically determined by relying on the steering preset on the steering handle (16), especially the dynamic and / or absolute value of the steering preset.

5. The method according to any one of the preceding claims, characterized in that, The variable characteristic parameter is determined by at least two sub-characteristic parameters (46, 48), wherein the first sub-characteristic parameter (46) of the sub-characteristic parameters (46, 48) is determined by the deflection (50) of the steering handle (16), and the second sub-characteristic parameter (48) of the sub-characteristic parameters (46, 48) is determined by at least the steering speed (52) of the steering handle (16).

6. The method according to claim 5, characterized in that, The variable feature parameter (40) is determined by the maximum value of the first sub-feature parameter (46) and the second sub-feature parameter (48).

7. The method according to any one of claims 1 to 4, characterized in that, The changing characteristic parameters are identified using a field that at least depicts the characteristic curve of the steering handle deflection with respect to the steering speed of the steering handle.

8. A computing unit (22) for implementing the method according to any one of the preceding claims.

9. A vehicle (12), particularly a motor vehicle, comprising: a steering system (10) configured as a steer-by-wire system, the steering system including an operating unit (14) having at least one steering handle (16) and at least one wheel steering angle adjuster (18) operatively connected to the operating unit (16) for changing the wheel steering angle of at least one wheel (20); and a calculation unit (22) according to claim 8.

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