Electric steering system with feedback and control methods

Abstract

An electric steering system comprises a controller, a steering wheel, and an associated steering wheel actuator. The steering wheel actuator applies a driver hand torque (resistance or movement perceptible to the driver at the steering wheel) to the steering wheel. The controller operates the steering wheel actuator via a control signal. This control signal includes a stochastic noise component.

Description

[0001] The invention relates to an electric steering system and a control method for such a system. In particular, the invention relates to an electric steering system with feedback to the driver and a method for generating this feedback.

[0002] In electric steering systems, also known as "steer-by-wire," the steering wheel is mechanically decoupled from the front axle steering gear, and a steering wheel actuator synthetically applies a driver's hand torque to the steering wheel. This typically includes, among other things, a simulation of the inertia, friction, and hysteresis of the steering system and an active return to straight-ahead driving. Furthermore, for example, to improve the feeling of connection to the road (a more responsive steering feel or a sense of connection to the road), the forces acting on the tie rods of the front axle steering can be simulated, with a distinction made between high- and low-frequency components. High frequency ranges (approximately between 5 and 80 Hz) represent unique, impulse-like excitations, while in the low frequency range (up to approximately 5 Hz), a distinction is made between useful and interference information.Interfering information primarily consists of periodic steering wheel vibrations, which originate from rotational imbalances in the axle system, and is distinguished from useful information about the current road and driving conditions.

[0003] Due to the mechanical decoupling of the steering wheel in a steer-by-wire system, there is a risk of a "numb" or unresponsive steering feel. However, methods known in the art for providing road feedback and thus a pleasant or responsive steering feel are complex and not always effective.

[0004] Against this background, the purpose of the present application is to provide a pleasant steering feel for the driver using simple means.

[0005] The solution to this problem can be found in the features of the attached independent claims. Possible embodiments are covered by the dependent claims.

[0006] According to one aspect of the present application, an electric steering system comprises a controller, a steering wheel, and an associated steering wheel actuator. The steering wheel actuator applies a driver hand torque (resistance or movement perceptible to the driver at the steering wheel) to the steering wheel. The controller operates the steering wheel actuator by means of a control signal. This control signal includes a stochastic noise component. This can have the advantage that a pleasant or responsive steering feel can be generated for the driver using simple means, without placing excessive demands on the vehicle's resources (data bus, computing power, etc.).

[0007] According to one aspect of the present application, the stochastic noise component of an electric steering system includes at least one type of red noise, pink noise, or white noise. This can have the advantage of creating a pleasant steering feel at the steering wheel using simple means.

[0008] According to one aspect of the present application, the stochastic noise component of an electric steering system is scaled depending on a vehicle state. The vehicle state can be, for example, a driving condition or a speed, or the stochastic noise component can be scaled depending on the speed. This can have the advantage of realistically conveying a pleasant steering feel to the driver.

[0009] According to one aspect of the present application, the scaling of a stochastic noise component in an electric steering system is proportional and / or frequency-dependent. This can have the advantage that the control signal can be precisely adjusted as desired and / or required.

[0010] According to one aspect of the present application, the frequency-dependent scaling in an electric steering system involves a Fourier transform. This can have the advantage that a control signal can be easily individualized.

[0011] According to one aspect of the present application, the proportional scaling in an electric steering system takes into account at least one factor of vehicle speed and instantaneous standard deviation of lateral acceleration. This can have the advantage that readily available vehicle data can be used to adapt the control signal.

[0012] According to one aspect of the present application, proportional scaling in an electric steering system is applied only to individual frequency ranges of the stochastic noise component. This can have the advantage that a control signal can be easily individualized.

[0013] According to one aspect of the present application, a control method for an electric steering system comprises the following steps: • Generating a control signal using a stochastic noise component; • Transmitting the control signal to a steering wheel actuator and controlling it based on the control signal. This can have the advantage of creating a pleasant or lively steering feel for the driver using simple means, without placing excessive strain on the vehicle's resources (data bus, computing power, etc.).

[0014] According to one aspect of the present application, generating a control signal in a control method involves scaling the stochastic noise component. This scaling can be dependent on the vehicle's driving state (e.g., speed-dependent). This can have the advantage of realistically conveying a pleasant steering feel to the driver.

[0015] According to one aspect of the present application, in a control method, the stochastic noise component in the generation step comprises at least one of the following: red noise, pink noise, or white noise. This can have the advantage that a pleasant steering feel at the steering wheel can be generated using simple means.

[0016] According to one aspect of the present application, in a control method, the stochastic noise component is scaled depending on a driving condition during the generation step. This can have the advantage that the control signal can be adapted more precisely as desired and / or required.

[0017] According to one aspect of the present application, scaling in a control method is proportional and / or frequency-dependent. This can have the advantage that the control signal can be easily adjusted as desired and / or required.

[0018] According to one aspect of the present application, the frequency-dependent scaling in a control method includes a Fourier transform. This can have the advantage that a control signal can be easily individualized.

[0019] According to one aspect of the present application, a control method takes into account the proportional scaling of at least one of the vehicle speed and the instantaneous standard deviation of a lateral acceleration. This can have the advantage that readily available data can be used for generating the control signal.

[0020] According to one aspect of the present application, in a control method, proportional scaling is applied only to individual frequency ranges of the stochastic noise component. This can have the advantage that a control signal can be easily individualized.

[0021] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those mentioned below in the description of the figures and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually. The features of the control method can be incorporated into the device claims and vice versa. Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the figures. In the figures, identical or (functionally) similar components are identified by the same reference numerals. The figures are all schematic, and dimensional relationships cannot be derived unless expressly stated. Fig. Figure 1 shows a schematic view of an electric steering system according to the invention. Fig. Figure 2 shows a flowchart of a control procedure. Fig. Figure 3 shows a process of dynamic scaling of a stochastic noise component.

[0022] Initially referring to Fig. Figure 1 schematically depicts an electric steering system 10, comprising a steering wheel 12, a steering wheel actuator 13, and a control unit 11. The steering wheel actuator 13 is connected to the steering wheel 12. The steering wheel actuator 13 applies a driver's hand torque (resistance or movement perceptible to the driver at the steering wheel 12) to the steering wheel 12. The control unit 11 controls the steering wheel actuator 13 by means of a control signal 14 which includes a stochastic noise component 15. The control signal 14 with the stochastic noise component 15 is Fig. 1 is symbolized by the arrow and is generated in control 11 (see below).

[0023] In Fig. Figure 2 shows a flowchart of a control procedure for an electric steering system 10. In a first step, a control signal 14 comprising a stochastic noise component 15 is generated. The generated control signal 14 is then transmitted to a steering wheel actuator 13, which is controlled by the control signal 14 and applies a driver hand torque (see above) to a steering wheel 12. The stochastic noise component 15 can be considered a third component, in addition to high- and low-frequency excitations (known) by the control signal 14. The stochastic noise component 15 can be distinguished by a wide frequency range (approximately between 10 Hz and 400 Hz) and its persistence across all driving states (except when the vehicle is stationary).

[0024] Stochastic noise component 15 differs from high-frequency excitations that simulate discrete events (e.g., excitation peaks when driving over cobblestones) by its lower moment amplitude and energy density, as well as its indirect synthetic generation via auxiliary quantities, such as by using at least one type of red noise, pink noise, or white noise. By design, periodic oscillations are avoided, and the stochastic noise component 15 can be scaled dynamically to meet different requirements and applications (e.g., differently tuned driving modes such as "Sport," "Comfort," etc.).

[0025] The stochastic noise component 15, which is encompassed by the control signal 14, can be dynamically scaled, as shown in the flowchart of the Fig. Figure 3 illustrates this. Here, a stochastic noise component 15 is scaled frequency-dependently using frequency ranges determined from a Fourier transform of vehicle dynamics parameters (see below). Furthermore, the (energy density of the) stochastic noise component 15 is scaled proportionally. Optionally, only one of the two scaling operations can be performed. The proportional scaling can also be performed on an easily obtainable vehicle dynamics parameter such as vehicle speed or lateral acceleration, or the instantaneous standard deviation of a lateral acceleration. Fig. 3. The instantaneous standard deviation of a lateral acceleration is used. The two scales then result in a dynamically scaled stochastic noise component 15. REFERENCE MARK LIST 10 electric steering system 11 Control 12 Steering wheel 13 Steering wheel actuator 14 Control signal 15 stochastic noise component

Claims

[1] Electric steering system (10) comprising a controller (11), a steering wheel (12) and an associated steering wheel actuator (13), wherein the steering wheel actuator applies a driver hand torque to the steering wheel and the controller controls the steering wheel actuator by means of a control signal (14), and wherein the control signal includes a stochastic noise component (15). [2] Electric steering system (10) according to claim 1, wherein the stochastic noise component (15) comprises at least one of red noise, pink noise or white noise. [3] Electric steering system (10) according to claim 1 or 2, wherein the stochastic noise component (15) is scaled depending on a vehicle state. [4] Electric steering system (10) according to claim 3, wherein the scaling is proportional and / or frequency-dependent. [5] Electric steering system (10) according to claim 4, wherein the frequency-dependent scaling comprises a Fourier transform. [6] Electric steering system (10) according to claim 4 or 5, wherein the proportional scaling takes into account at least one of vehicle speed and instantaneous standard deviation of a lateral acceleration. [7] Electric steering system (10) according to claim 6, wherein the proportional scaling is applied only to individual frequency ranges of the stochastic noise component (15). [8] Control method (100) for an electric steering system (10), comprising the steps: • Generating a control signal (14) using a stochastic noise component (15); • Transmitting the control signal to a steering wheel actuator (13). [9] Control method (100) according to claim 8, wherein the generation comprises scaling the stochastic noise component (15). [10] Control method (100) according to claim 8 or 9, wherein in the generation step the stochastic noise component (15) comprises at least one of red noise, pink noise or white noise. [11] Control method (100) according to one of claims 8 to 10, wherein in the generation step the stochastic noise component (15) is scaled depending on a driving state. [12] Control method (100) according to claim 11, wherein the scaling is proportional and / or frequency-dependent. [13] Control method (100) according to claim 12, wherein the frequency-dependent scaling comprises a Fourier transform. [14] Control method (100) according to claim 11 or 12, wherein the proportional scaling takes into account at least one of vehicle speed and instantaneous standard deviation of a lateral acceleration. [15] Control method (100) according to claim 14, wherein the proportional scaling is applied only to individual frequency ranges of the stochastic noise component (15).

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