Adjustment of steering feel in steer-by-wire systems

Abstract

The invention relates to a method for adjusting the steering feel of a driver of a vehicle at an input element of the vehicle, wherein the vehicle has a steer-by-wire system. The method comprises the following steps: compiling a reference (7) for the steering feel and adapting (10) the steering feel by means of a scaling factor.

Description

Background Art

[0001] The invention relates to a method for adjusting a steering feel of a driver of a vehicle generated by an input element, in particular a steering wheel, wherein the steering system is a steer-by-wire system.

[0002] Steering feel here refers to the combination of driving feel (i.e. steering torque at the steering wheel), steering gear ratio (i.e. the gear ratio between the steering wheel and the wheel steering angle) and vehicle reaction (vehicle reaction reflects the feedback of steering input to the driver through the vehicle).

[0003] In the prior art, steering systems with a mechanical connection of a steering wheel to the wheel steering angle are known. It is also known that steer-by-wire systems are possible, wherein there is no mechanical connection between the steering wheel and the wheel to be steered. Summary of the invention

[0004] Current EPS steering systems have a continuous mechanical coupling from the steering wheel of the vehicle in question to the steering angle of the wheels. There is a mechanical coupling that results in a constant transmission ratio from the wheels to the steering wheel, or one that cannot be changed by software. Thus, for example, the steering ratio cannot be adjusted for a specific region. In contrast, there is no mechanical coupling for steer-by-wire. A steer-by-wire system is characterized in that there is no mechanical connection between the steering wheel and the steering angle of the steerable wheels. This makes it possible to move the steering wheel independently of the yaw, or to change the transmission ratio from the steerable wheels to the input element according to the region.

[0005] One object is therefore to provide a steering system for steer-by-wire, in which the steering feel of the driver at the steering wheel is adjusted in order to convey a suitable or appropriate steering feel via the steering wheel.

[0006] As a first specific embodiment of the invention, a method for adjusting the steering feel of a driver of a vehicle at an input element of the vehicle is provided, wherein the vehicle has a steer-by-wire system, the method comprising the steps of programming a reference for the steering feel and adapting the steering feel by means of a scaling factor.

[0007] Since the input element, in particular the steering wheel, is decoupled from the wheel steering angle, the steer-by-wire system provides the following possibilities: the steering feel can be adjusted arbitrarily according to the steering wheel. In particular, the steering feel can be adjusted in such a way that a high level of comfort and safety is generated for the driver of the vehicle concerned.

[0008] As a second specific embodiment of the present invention, a control unit of a steering system is provided, which has a computing unit for carrying out the method according to any one of claims 1 to 6 .

[0009] As a third embodiment of the present invention, a steering system having a controller according to claim 7 is provided.

[0010] Exemplary embodiments are described in the dependent claims.

[0011] According to an exemplary embodiment of the present invention, a method is provided, in which the reference includes the following elements: a basic steering torque with the input variables of rack force and vehicle speed and / or an active steering with the input variables of steering wheel angle, driver torque and vehicle speed and / or a damping with the input variables of steering wheel angle velocity, driver torque and vehicle speed and / or a hysteresis with the input variables of steering wheel angle velocity, driver torque and vehicle speed and / or an inertia with the input variables of steering wheel angle acceleration, driver torque and vehicle speed.

[0012] The elements of basic steering torque, active steering, damping, hysteresis and inertia represent the elements that are important for compiling a reference for the steering feel. However, there may also be other elements that can also be taken into account when calculating the reference.

[0013] According to a further exemplary embodiment of the present invention, a method is provided, in which the scaling factor is generated as follows: reference base steering torque / current base steering torque and / or reference active steering / current active steering and / or reference damping / current damping and / or reference hysteresis / current hysteresis and / or reference inertia / current inertia.

[0014] According to yet another embodiment of the present invention, a method is provided, wherein a target steering sensation is generated as follows:

[0015] Target steering feel = basic steering torque·scaling factor_1+active steering·scaling factor_2+damping·scaling factor_3+hysteresis·scaling factor_4+inertia·scaling factor_5.

[0016] In a further embodiment of the invention, a method is provided, in which the following is generated: scaling factor_1=reference basic steering torque / current basic steering torque and / or scaling factor_2=reference active steering / current active steering and / or scaling factor_3=reference damping / current damping and / or scaling factor_4=reference hysteresis / current hysteresis and / or scaling factor_5=reference inertia / current inertia.

[0017] According to a further exemplary embodiment of the present invention, a method is provided, in which the input element is a steering wheel.

[0018] In an alternative embodiment, the input element is a gear lever.

[0019] In a further embodiment of the invention, a steering system is provided, which is a central controller or a single wheel controller. For example, a corner module can be considered a single wheel controller, in which steering, braking and drive are integrated in one unit for each wheel. A central controller can differ from a single wheel controller in its design by an axially displaceable moving element which is conventionally designed as a rack.

[0020] According to yet another specific embodiment of the present invention, a steering system is provided, wherein the steering system is a central controller or an individual wheel controller.

[0021] One idea of ​​the present invention is to use the mechanical decoupling of the vehicle's wheel steering angle from the steering wheel to achieve an improved steering feel, in particular to achieve a steering movement of the steering wheel that represents for the relevant driver a suitable steering feel and appropriate assistance when steering the vehicle.

[0022] A further concept of the present invention is to adjust the scaling of the steering feel produced for the driver of the vehicle in such a way that it remains constant or its characteristics remain the same even with different steering ratios.

[0023] In particular for steer-by-wire systems with a central controller or individual wheel controllers, the decoupling of vehicle input elements, in particular the steering wheel, from the wheel steering angles should be used to provide scalability of the steering feel when varying the variable transmission ratio of the steering system.

[0024] This advantageously results in a reduction in the application overhead, since a limited number of application variants can be used. In addition, the use of a reference application can be achieved, wherein the reference application can be understood as the desired target application. In addition or as an alternative, one or more parameters can be introduced, which can adjust and scale the angle-dependent steering feel component by establishing a ratio. This results in additional control options for the input element, in particular the steering wheel.

[0025] Individual features can of course also be combined with one another, whereby advantageous effects can also partially occur which exceed the sum of the individual effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further details and advantages of the invention become clear with the aid of the exemplary embodiments shown in the accompanying drawings, in which:

[0027] Figure 1 a diagram showing elements of a steering feel application device; and

[0028] Figure 2 A flow chart shows the sequence according to the present invention for a steering feel application. DETAILED DESCRIPTION

[0029] Figure 1 A device for creating a steering feel for the driver of a vehicle of interest is shown, wherein the device can be composed of different components. For example, there is a first component 2 that provides a basic steering torque, a component 3 that applies an active turning torque, thereby producing a desired target turning characteristic of the steering wheel towards the center over the entire vehicle speed range. In addition, component 4 can produce damping, another component 5 produces hysteresis characteristics, and component 6 causes inertia.

[0030] The input variables of the component basic steering torque 2 can be the rack force and the vehicle speed. The input variables of the active swivel 3 can be the steering wheel steering angle, the driving torque and the vehicle speed. For the input variable of the current steering wheel angle, a suitable target swivel speed is predefined. This characteristic determines the vehicle reaction and the resetting of the axle towards the center. Therefore, in the case of a more direct transmission compared to the reference transmission ratio, there is a smaller steering wheel steering angle when the wheel position is the same and the swivel towards the center must be carried out more slowly accordingly. For an indirect transmission, the opposite occurs, so that the target swivel speed must be increased to obtain a characteristic similar to that in the reference application of the steering feel. The input variables of the damping 4 can be the steering wheel angle speed, the driving torque and the vehicle speed. When calculating the hysteresis 5, the input variables can be the steering wheel angle speed, the driving torque and the vehicle speed. The input variables of the component 6 can be the steering wheel acceleration, the driving torque and the vehicle speed.

[0031] For all elements, a corresponding scaling factor can be calculated for the steering wheel angle variable, which scaling factor results from the ratio of the reference transmission ratio to the current rotational ratio.

[0032] The corresponding formula for the scaling factor is generated as follows: Scaling Factor Steering Feel Applied = (Initial Gear Ratio Reference Applied) / (Current Gear Ratio).

[0033] Therefore, the scaling factor required for all modules is generated as a ratio of the reference transmission ratio to the current transmission ratio. The current transmission ratio depends on different situations, such as, for example, the speed of the relevant vehicle and / or the rack travel. The scaling factor resulting from the formation of the proportional number influences the steering angle, the angular velocity and / or the angular acceleration of the steering wheel. The scaling factor can additionally be adjusted, for example, depending on the driving situation or driving style of the driver.

[0034] Figure 2A flow chart for applying a steering feel to a steering wheel is shown, wherein in a first step a reference model 7 is compiled as a target value for a desired steering feel. The reference model can have five elements, namely basic steering torque, active steering, damping, hysteresis and inertia 8. If the current steering feel felt by the driver of the relevant vehicle at the steering wheel deviates from this desired steering feel 9, the steering characteristics, in particular the basic steering torque, active steering, damping, hysteresis and / or inertia, are adjusted accordingly 10 in order to maintain the characteristics of the steering feel.

[0035] It should be noted that the concept “comprising” does not exclude other elements or method steps, just like the concept “a” does not exclude multiple elements and steps.

[0036] The reference signs used serve only to improve the understanding and are not to be considered limiting in any way, wherein the scope of protection of the present invention is reflected by the claims.

Claims

1. A method for adjusting the steering feel of a driver of a vehicle at an input element of the vehicle, wherein the vehicle has a steer-by-wire system, the method comprising the following steps: Compiling the steering feel benchmark (7) and Adapting the steering feel by a scaling factor (10), wherein the scaling factor is selected in such a way that the steering feel remains constant or its characteristics remain the same even in the case of different steering ratios, The benchmarks include the following elements: Basic steering torque (2) with the input variables rack force and vehicle speed and / or active steering (3) with the input variables steering wheel angle, driver torque and vehicle speed and / or damping (4) with the input variables steering wheel angle velocity, driver torque and vehicle speed and / or hysteresis (5) with the input variables steering wheel angle velocity, driver torque and vehicle speed and / or inertia (6) with the input variables steering wheel angle acceleration, driver torque and vehicle speed, The scaling factor is generated as follows: Base steering torque / current base steering torque (2) and / or Baseline active slew / Current active slew (3) and / or Base Damping / Current Damping (4) and / or Baseline Lag / Current Lag (5) and / or Base inertia / Current inertia (6).

2. The method of claim 1, wherein the target steering sensation is generated as follows: Target steering feel = basic steering torque (2) · scaling factor_1 + active steering (3) · scaling factor_2 + damping (4) · scaling factor_3 + hysteresis (5) · scaling factor_4 + inertia (6) · scaling factor_5.

3. The method according to claim 2, wherein: Scaling factor_1 = reference base steering torque / current base steering torque (2) and / or Scaling factor_2 = reference active rotation / current active rotation (3) and / or Scaling factor_3 = base damping / current damping (4) and / or Scaling factor_4 = reference lag / current lag (5) and / or Scaling factor_5 = reference inertia / current inertia (6).

4. The method according to any one of claims 1 to 3, wherein the input element is a steering wheel. 5 . A control unit of a steering system having a computing unit for carrying out the method according to claim 1 .

6. A steering system having a controller according to claim 5.

7. The steering system according to claim 6, wherein the steering system comprises a central regulator or individual wheel regulators.

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