Steer-by-wire steering system comprising a control signal for adjusting and method for operating a steer-by-wire steering system

Abstract

The present invention relates to a steer-by-wire system (1) for a motor vehicle, the system comprising: a steering shaft (3) connectable to a steering handle (2) for rotation with the steering handle; a feedback actuator (4) having an electric motor (5) acting on a rotor shaft (6); a gearbox (7) via which the rotor shaft (6) is connected to the steering shaft (3); and a first angle sensor (8) and a second angle sensor (9). A control unit (10) associated with the steering system (1) is configured to receive a first sensor signal (S1) provided by the first angle sensor (8), receive a second sensor signal (S2) provided by the second angle sensor (9), and provide a control signal (ST) to control the electric motor (5). The first angle sensor (8) is positioned at the steering shaft (3) to detect rotation of the steering shaft (3), and the second angle sensor (9) is positioned at the rotor shaft (6) to detect rotation of the rotor shaft (6). The control unit (10) is also designed to take into account the difference between the rotation of the steering shaft (3) and the corresponding transmitted rotation of the rotor shaft (6) based on the first sensor signal (S1) and the model (M) of the gearbox (7) stored in the control unit (10), and to adjust the control signal in consideration of said difference. The invention also relates to a method for operating a steer-by-wire system (1).

Description

[0001] This invention relates to a steer-by-wire system for motor vehicles, comprising: a steering shaft torsionally connected to a steering control device; a feedback actuator having an electric motor acting on a rotor shaft; a transmission mechanism connecting the rotor shaft to the steering shaft via the transmission mechanism; and a first angle sensor and a second angle sensor. A control unit assigned to the steering system is designed to receive a first sensor signal provided by the first angle sensor, receive a second sensor signal provided by the second angle sensor, and provide control signals for controlling the electric motor.

[0002] Furthermore, the present invention relates to a method for operating a steer-by-wire system, the steer-by-wire system comprising: a steering shaft torsionally connected to a steering control device; a feedback actuator having an electric motor for driving a rotor shaft; a transmission device by means of which the rotor shaft is connected to the steering shaft; a first angle sensor and a second angle sensor. A control unit assigned to the steering system receives a first sensor signal provided by the first angle sensor and a second sensor signal provided by the second angle sensor and provides a control signal for controlling the electric motor.

[0003] In the prior art, steer-by-wire systems are known. For example, DE 10 2019 204 857 A1 discloses a steer-by-wire system and a method for controlling such a system. In this case, the steering angle input by the driver via a steering mechanism is detected by an angle sensor arranged on the steering shaft and used by a control unit to control the steering actuator. The control unit is also used to control a feedback actuator taking into account the force detected at the steering actuator, so that the influence of the road surface can be transmitted to the driver via the steering mechanism. A steer-by-wire system is also known from WO2018 / 233846 A1, which includes a first angle sensor and a second angle sensor. To enable improved feedback on driving conditions to the driver via the steering mechanism, additional data for controlling the feedback actuator is received from a sensor device arranged on the wheel suspension, as described in DE 10 2018 126 337 A1. However, the additional sensors result in higher costs. Furthermore, the influence within the steering system has not been fully considered until now.

[0004] In this context, the object of the present invention is to improve steer-by-wire systems and methods for using steer-by-wire systems, particularly with respect to providing the driver with low-cost feedback on driving conditions via steering control devices.

[0005] To achieve this objective, a steer-by-wire system and a method for operating the steer-by-wire system are provided according to the present invention. Other advantageous embodiments of the invention are described in the specification and illustrated in the accompanying drawings.

[0006] The proposed solution provides a steer-by-wire system for motor vehicles, comprising: a steering shaft torsionally connected to a steering control device, particularly a steering wheel; a feedback actuator having an electric motor acting on a rotor shaft; a transmission connecting the rotor shaft to the steering shaft; and a first angle sensor and a second angle sensor. The first angle sensor is positioned on the steering shaft to detect rotation of the steering shaft and provides this rotation as an initial sensor signal. The second angle sensor is positioned on the rotor shaft to detect rotation of the rotor shaft and provides this rotation as a second sensor signal. A control unit assigned to the steering system is designed to receive the first sensor signal provided by the first angle sensor, receive the second sensor signal provided by the second angle sensor, and provide control signals for controlling the electric motor. The control unit is further designed to determine, based on the first and second sensor signals, the difference between the rotation of the steering shaft and the corresponding transmitted rotation of the rotor shaft, taking into account a model of the transmission stored in the control unit, and to adjust the control signals accordingly.

[0007] In an ideal steering system and transmission where the components, particularly the part between the two angle sensors, have infinite stiffness, the first and second angle sensors should provide the same value, considering the transmission ratio. If infinite stiffness does not exist in the ideal system, there will be some difference between the two measurement positions of the angle sensors, depending on the stiffness and torque or force between the two measurement points. Therefore, in practice, a deviation can be seen in the provided sensor signals. This invention is based on the understanding that the deviation, due to the different arrangement of the angle sensors, can be used to determine the difference between the rotation of the steering shaft and the corresponding transmitted rotation of the rotor shaft, and this difference can be used to improve the control of the feedback actuator. The behavior of the transmission, particularly its characteristics under different conditions, is advantageously stored as a model in the control unit, wherein this model specifically represents a simulation of the transmission implemented in software. In this way, the influence of the transmission, particularly frictional influences, can be advantageously reduced, and the absence of infinite stiffness in the transmission components can be particularly taken into account. Furthermore, it is advantageous that conclusions about the torque applied to the steering mechanism can be drawn based on the parameters stored in the control unit as a model of the transmission device and the sensor values ​​recorded on different axes, and these torques can be taken into account when controlling the feedback actuator, advantageously eliminating the need for external sensors.

[0008] Adjustments to the control signal advantageously induce interference compensation, particularly compensation for interference caused by friction. Furthermore, the control signal can be advantageously adjusted as needed to add additional motor torque to the original demand and / or modify the original motor torque demand through gain, so as to have more or less torque within the torque range, depending on the circumstances.

[0009] The control unit assigned to the steering system is, in particular, an electronic control unit (ECU), especially the ECU of a motor vehicle, which is preferably connected to the steering system via a suitably designed interface for signal transmission. Specifically, in cases where the control unit assigned to the steering system is not included in the steering system, the invention also provides a motor vehicle having a central control unit and a steering system designed according to the invention as a solution to this problem, wherein the central control unit of the motor vehicle is a control unit assigned to the steering column. However, particularly, as an advantageous design, it can also be configured such that the steering system includes its own control unit, wherein this control unit is a control unit assigned to the steering system.

[0010] An advantageous embodiment of the proposed steer-by-wire system is configured such that a model of the transmission stored in the control unit takes into account at least one of the following characteristics: transmission ratio; transmission stiffness; transmission inertia; transmission clearance; and transmission temperature. Specifically, for this purpose, corresponding parameters can be stored in the model. In particular, advantageous disturbance compensation can be achieved by considering one or more of these parameters. Parameters such as transmission temperature can be advantageously adjusted dynamically. Advantageously, sensors provide the corresponding parameter values. Assigning corresponding values ​​to different situations in a lookup table is also advantageous. In particular, empirical values ​​regarding transmission temperature can be stored for different temperature windows of ambient temperature and / or different usage intensities of the transmission.

[0011] According to another advantageous design of the steer-by-wire system, the values ​​of the differences are each assigned a factor specifically by means of a lookup table stored in the control unit. The control unit is advantageously designed to adjust the control signal by multiplying the control signal by the factor assigned to the determined differences. This advantageously provides easy adjustability of the control signal, which ultimately leads to an improved steering feel for the driver.

[0012] Another advantageous embodiment involves designing the control unit to determine the control signal based on the functional relationship, particularly a mathematical function stored in the model, taking into account the determined difference or the factors assigned to the determined difference in the functional relationship, and adjusting the control signal in particular with regard to the difference. Specifically, a linear relationship can be used as the basis, where the functional relationship is advantageously adjusted by factors, particularly by means of corresponding mathematical operations. However, depending on the actual characteristics of the transmission device, a nonlinear relationship can also be used as the basis.

[0013] According to another advantageous design of the steer-by-wire system, the first angle sensor is a single-turn sensor. Alternatively or additionally, it can be specifically configured that the second angle sensor is a single-turn sensor. The single-turn sensor is designed to cover only one full turn at a time and therefore cannot detect angles exceeding 360°. Such a sensor can be advantageously obtained at low cost.

[0014] It is also advantageous that the first angle sensor is a multi-turn sensor. Additionally or alternatively, the second angle sensor is advantageously a multi-turn sensor. The multi-turn sensor is advantageously designed to detect angles greater than 360°. The design of the first angle sensor being a multi-turn sensor and the second angle sensor being a single-turn sensor has proven advantageous.

[0015] Another advantageous design feature of steer-by-wire systems is that the transmission comprises only components and / or materials having characteristics that can be predicted and thus described, particularly by means of a model that can be stored in the control unit, when the transmission is used in the steering system. Specifically, the transmission can be configured to have a specific stiffness, and this stiffness advantageously has a specific value with specific characteristics that are advantageously already known. In particular, the stiffness of the transmission can be configured to behave linearly. If the stiffness of the transmission is non-linear, then the transmission will then have at least one known characteristic. The torque transmitted by the variable transmission is then advantageously calculated based on this information.

[0016] Specifically, the control unit can also be configured to adjust the control signal so that the torque provided by the electric motor increases when the difference is negative. It has been shown that this can produce a more realistic steering feel.

[0017] Regarding the method for operating a steer-by-wire system also proposed to achieve the aforementioned objectives, it is particularly proposed that the steer-by-wire system possesses the aforementioned features individually or in combination. Specifically, the proposed method provides a steer-by-wire system comprising: a steering shaft that is torsionally connected to a steering control device; a feedback actuator having an electric motor driving a rotor shaft; a transmission that connects the rotor shaft to the steering shaft; a first angle sensor and a second angle sensor. The proposed method further provides that the first angle sensor detects rotation of the steering shaft and provides this rotation as a first sensor signal, and the second angle sensor detects rotation of the rotor shaft and provides this rotation as a second sensor signal. A control unit assigned to the steering system receives the first sensor signal provided by the first angle sensor and the second sensor signal provided by the second angle sensor. The control unit also provides a control signal for controlling the electric motor of the feedback actuator, wherein the control unit, taking into account a model of the transmission stored in the control unit, determines the difference between the rotation of the steering shaft and the corresponding transmitted rotation of the rotor shaft based on the first and second sensor signals, and adjusts the control signal taking into account this difference. In this way, the effects of the transmission, particularly frictional effects, can be advantageously compensated. Furthermore, it is advantageous that conclusions regarding the torque applied to the steering mechanism are drawn based on parameters stored in the control unit as a model of the transmission device and sensor values ​​detected on different shafts, and these torques are taken into account when controlling the feedback actuator, advantageously eliminating the need for external sensors. Therefore, adjustments to the control signal advantageously result in interference compensation, particularly compensation for interference caused by friction. Additionally, the control signal is advantageously adjusted to suit the situation, such that additional motor torque is added to the original demand and / or the original motor torque demand is modified by gain to have more or less torque within the torque range, depending on the situation.

[0018] Advantageously, for the model of the transmission device, at least one of the following characteristics is considered: transmission ratio; transmission stiffness; transmission inertia; transmission clearance; transmission temperature. In particular, advantageous disturbance compensation can be achieved by considering one or more of these parameters.

[0019] Furthermore, advantageously, the values ​​of the differences are each assigned a factor, wherein the control unit adjusts the control signal by multiplying the control signal by this factor. This advantageously provides easy adjustability of the control signal, which ultimately leads to improved steering feel for the driver.

[0020] Another advantageous embodiment of this method involves the control unit determining the control signal based on a functional relationship, particularly a mathematical function. Advantageously, the determined difference, or a factor in the mathematical function that assigns a value to the determined difference, is taken into account in adjusting the control signal to account for that difference. Specifically, the functional relationship considers the behavior of at least one transmission characteristic, particularly the stiffness of the transmission.

[0021] Specifically, the control unit can be configured to adjust the control signal so that the torque provided by the electric motor increases when the determined difference is negative. Advantageously, this produces a more realistic steering feel.

[0022] Other advantageous details, features, and implementation details of the invention will be described in more detail with reference to the embodiments shown in the figures (Figures: accompanying drawings). In the figures:

[0023] Figure 1 An exemplary embodiment of the steer-by-wire system designed according to the present invention is shown in a simplified perspective view;

[0024] Figure 2 A simplified schematic diagram illustrates another exemplary embodiment of the steer-by-wire system designed according to the present invention; and

[0025] Figure 3 An exemplary embodiment of a control unit designed according to the present invention for performing a method developed according to the present invention is illustrated in schematic block diagram.

[0026] In different accompanying drawings, the same parts are often given the same reference numerals, and therefore sometimes only one of the accompanying drawings is used for illustration.

[0027] exist Figure 1 The image shows an exemplary embodiment of a steer-by-wire system 1. The steer-by-wire system 1 includes a steering shaft 3, on which a steering wheel, serving as a steering control device 2, is arranged. The system detects the driver's steering movements, and a control unit generates a steering actuator control signal based on the detected steering movements. The control unit may also be... Figure 1 The control unit 10 is shown in the diagram. The steering actuator control signal is then transmitted to the steering actuator 16 via cable 15. The steering actuator 16 controls the position of the steering wheel 18. The steering actuator 26 causes axial displacement of the rack 19 by means of a pinion 17. The steering wheel 18 is connected to the rack 19 via a tie rod 20.

[0028] Additionally, a feedback actuator 4 is arranged on the steering shaft 3 of the steering system 1. The feedback actuator 4 transmits torque to the steering control device 2 to provide the driver with feedback on the steering and handling behavior of the vehicle using the steering system 1. The feedback actuator 4 includes an electric motor 5, wherein the electric motor 5 acts only on... Figure 1 The rotor shaft 6 is indicated in the diagram. Specifically, the electric motor 5 can be configured to be a three-phase motor, particularly a synchronous motor, and even more particularly a permanent magnet synchronous motor. The rotor shaft 6 is connected to the steering shaft 3 via a transmission 7, wherein the transmission 7 comprises only components having the following characteristics: when used in the steering system 1, these characteristics are predictable and therefore deterministic.

[0029] Figure 1 The steer-by-wire system 1 shown also includes a first angle sensor 8 and a second angle sensor 9. In this exemplary embodiment, the first angle sensor 8 is a single-turn sensor, and the second angle sensor 9 is a multi-turn sensor. Angle sensors 8 and 9 are only... Figure 1 The diagram is schematically shown. It can be configured such that a first angle sensor 8 is positioned on the steering shaft 3 to detect rotation of the steering shaft 3 and provide it as a first sensor signal S1. Furthermore, it can be configured such that a second angle sensor 9 is positioned on the rotor shaft 6 to detect rotation of the rotor shaft 6 and provide it as a second sensor signal S2. A control unit 10 assigned to the steering system 1 receives the first sensor signal S1 and the second sensor signal S2. The control unit 10 can be specifically included in the steering system 1 and only... Figure 1 The diagram is schematically shown. Specifically, it can be configured that the control unit 10 receives other signals, particularly sensor signals related to the force acting on the steering actuator 16. The control unit 10 is designed to provide a control signal ST for controlling the electric motor 5 of the feedback actuator 4. Furthermore, the control unit 10 is designed to adjust the control signal ST based on the first sensor signal S1 and the second sensor signal S2, taking into account the model of the transmission 7 stored in the control unit. To make this adjustment, the control unit 10 is designed to determine the difference between the rotation of the steering shaft 3 and the rotation of the rotor shaft correspondingly transmitted based on the first sensor signal S1 and the second sensor signal S2, and to adjust the control signal ST in consideration of this difference, particularly increasing the torque provided by the electric motor 5 when the difference is negative. Specifically, the control unit 10 can also be configured as shown in reference... Figure 3 Designed as described.

[0030] exist Figure 2The diagram illustrates a steer-by-wire system 1 for a motor vehicle in a highly simplified manner. The steer-by-wire system 1 includes: a steering shaft 3, which is torsionally connected to a steering control device 2; and a feedback actuator 4, which has an action on a rotor shaft 6 (in...). Figure 2 The steering system 1 includes an electric motor 5 (not explicitly shown); a transmission 7, particularly a belt drive, by which a rotor shaft 6 is connected to a steering shaft 3; and a first angle sensor 8 and a second angle sensor 9. The first angle sensor 8 is positioned on the steering shaft 3 to detect rotation of the steering shaft 3 and provides this rotation as a first sensor signal S1. The second angle sensor 9 is positioned on the rotor shaft 6 to detect rotation of the rotor shaft 6 and provides this rotation as a second sensor signal S2. The steering system 1 also includes a control unit 10, which is designed to receive the first sensor signal S1 provided by the first angle sensor 8 and the second sensor signal S2 provided by the second angle sensor 9. The control unit 10 is also designed to take into account the model of the transmission 7 stored in the control unit 10, to determine the difference between the rotation of the steering shaft 3 and the corresponding transmitted rotation of the rotor shaft 6 based on the first sensor signal S1 and the second sensor signal S2, and to provide a control signal ST for adjusting the electric motor 5, taking into account this difference. Specifically, it can be configured such that the determined differences are each assigned a factor via a lookup table, wherein the control unit 10 is also designed to adjust the control signal ST by multiplying it by the factor assigned to the determined differences. Specifically, the control unit 10 can also be referred to as follows. Figure 3 Designed as described.

[0031] For special reference Figure 1 and Figure 2 As explained, in Figure 3 The control unit 10 for the steer-by-wire system 1 is schematically shown in the block diagram. In particular, the control unit 10 may be a suitably programmed microcontroller unit. Figure 3 The control unit 10 shown receives a first sensor signal S1 provided by a first angle sensor 8, which indicates the rotation of the steering shaft of the steering system. Additionally, the control unit 10 receives a second sensor signal S2 provided by a second angle sensor 9, which indicates the rotation of the rotor shaft driven by the electric motor of the feedback actuator. Furthermore, the control unit 10 may be configured to receive at least one other signal S#, particularly a signal indicating the torque acting on the steering shaft.

[0032] Signals S1, S2, and S# are fed to the evaluation unit 101 of the control unit 10. The evaluation unit 101 includes a difference forming unit 102 as a subunit. This difference forming unit 102 stores a model M of the transmission mechanism for the steer-by-wire system, by means of which the rotor shaft is mechanically connected to the steering shaft. The model M specifically considers the gear ratio and transmission stiffness. This model M is used by the control unit 10 to determine the difference D between the rotation of the steering shaft and the corresponding transmitted rotation of the rotor shaft based on the first sensor signal S1 and the second sensor signal S2. The evaluation unit 101 provides a corresponding signal D representing this difference. Furthermore, the evaluation unit 101 determines an unadjusted control signal ST*, which is specifically based on at least one detection signal S#, but may also be based on at least one of the sensor signals S1 and S2 of the angle sensor. The control signal ST* is in principle adapted to control the electric motor of the feedback actuator, allowing the driver to receive feedback on the current driving situation via the steering control mechanism of the steer-by-wire system.

[0033] However, if the electric motor is controlled using the control signal ST*, interference in steering may be significant, particularly due to systemic effects on the steering system and is undesirable. To avoid this, the unadjusted control signal ST* and a signal D representing the difference are fed to the control signal generation unit 103, where the unadjusted control signal ST* is adjusted considering the difference D, and thus a control signal ST is provided for controlling the electric motor. Specifically, the control signal ST is determined by the control signal generation unit 103 of the control unit 10 according to a mathematical function. This mathematical function assigns a factor to the determined difference D and multiplies this factor by the control signal ST* to adjust the control signal ST* in consideration of the difference D.

[0034] The exemplary embodiments illustrated and described in conjunction with the accompanying drawings are used to illustrate the invention, and are not intended to limit the invention.

[0035] List of reference numerals

[0036] 1. Steer-by-wire steering system

[0037] 2. Steering control device

[0038] 3. Steering Axle

[0039] 4 Feedback Actuator

[0040] 5 Electric motors

[0041] 6. Rotor shaft

[0042] 7. Transmission device

[0043] 8 First Angle Sensor

[0044] 9. Second Angle Sensor

[0045] 10 Control Unit

[0046] Evaluation unit of control unit (10) 101

[0047] 102 Difference Forming Unit of Control Unit (10)

[0048] 103 Control Signal Generation Unit

[0049] 15 Cables

[0050] 16 Steering actuator

[0051] 17 small gears

[0052] 18 rounds

[0053] 19. Gear rack

[0054] 20 pull rod

[0055] Model of M transmission device (7)

[0056] S1 First Sensor Signal

[0057] S2 Second Sensor Signal

[0058] S# at least one other signal

[0059] ST Adjusted control signal

[0060] ST* Unadjusted control signal

[0061] D Difference

Claims

1. A steer-by-wire system (1) for a motor vehicle, the steer-by-wire system (1) comprising: Steering shaft (3), which is torsionally connected to steering control device (2); Feedback actuator (4), the feedback actuator (4) having an electric motor (5) acting on a rotor shaft (6); Transmission device (7), the rotor shaft (6) is connected to the steering shaft (3) via the transmission device (7); and First angle sensor (8) and second angle sensor (9). The control unit (10) assigned to the steering system (1) is designed to receive a first sensor signal (S1) provided by the first angle sensor (8), receive a second sensor signal (S2) provided by the second angle sensor (9), and provide control signals for controlling the electric motor (5). Its features are, The first angle sensor (8) is positioned on the steering shaft (3) to detect the rotation of the steering shaft (3) and provide the rotation of the steering shaft (3) as a first sensor signal (S1). The second angle sensor (9) is positioned on the rotor shaft (6) to detect the rotation of the rotor shaft (6) and provide the rotation of the rotor shaft (6) as a second sensor signal (S2). The control unit (10) is also designed to take into account the model (M) of the transmission device (7) stored in the control unit (10) to determine the difference between the rotation of the steering shaft (3) and the corresponding transmitted rotation of the rotor shaft (6) based on the first sensor signal (S1) and the second sensor signal (S2), and to adjust the unadjusted control signal ST* in consideration of the difference.

2. The steer-by-wire system (1) according to claim 1, characterized in that, The model (M) of the transmission device (7) stored in the control unit (10) takes into account at least one of the following characteristics: gear ratio; transmission device stiffness; transmission device inertia; transmission device clearance; transmission device temperature.

3. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The values ​​of the differences are each assigned a factor, wherein the control unit (10) is also designed to adjust the unadjusted control signal ST* by multiplying it by the factor assigned to the determined differences.

4. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The control unit (10) is also designed to determine the adjusted control signal ST according to the functional relationship, taking into account the determined difference or the factor of the value assigned to the determined difference in the functional relationship, so as to adjust the unadjusted control signal ST* in consideration of the difference.

5. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The first angle sensor (8) and / or the second angle sensor (9) are single-turn sensors.

6. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The first angle sensor (8) and / or the second angle sensor (9) are multi-turn sensors.

7. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The transmission device (7) comprises only components and / or materials having the following characteristics: these characteristics are predictable when the transmission device (7) is used in the steering system (1).

8. The steer-by-wire system (1) according to any one of claims 1-2, characterized in that, The control unit (10) is also designed to adjust the unadjusted control signal ST* such that the torque provided by the electric motor (5) increases when the difference is negative.

9. A method for operating a steer-by-wire system (1), the steer-by-wire system (1) comprising: Steering shaft (3), which is torsionally connected to steering control device (2); Feedback actuator (4), the feedback actuator (4) having an electric motor (5) for driving rotor shaft (6); transmission device (7), the rotor shaft (6) being connected to steering shaft (3) via the transmission device (7); first angle sensor (8) and second angle sensor (9). The control unit (10) assigned to the steering system (1) receives a first sensor signal (S1) provided by the first angle sensor (8), receives a second sensor signal (S2) provided by the second angle sensor (9), and provides control signals for controlling the electric motor (5). Its features are, The first angle sensor (8) detects the rotation of the steering shaft (3) and provides the rotation of the steering shaft (3) as the first sensor signal (S1). The second angle sensor (9) detects the rotation of the rotor shaft (6) and provides the rotation of the rotor shaft (6) as the second sensor signal (S2). The control unit (10) takes into account the model (M) of the transmission device (7) stored in the control unit (10) and determines the difference between the rotation of the steering shaft (3) and the corresponding transmitted rotation of the rotor shaft (6) based on the first sensor signal (S1) and the second sensor signal (S2), and adjusts the unadjusted control signal ST* in consideration of the difference.

10. The method according to claim 9, characterized in that, For the model (M) of the transmission device (7), consider at least one of the following characteristics: transmission ratio; transmission device stiffness; transmission device inertia; transmission device clearance; transmission device temperature.

11. The method according to claim 9 or claim 10, characterized in that, The values ​​of the differences are each assigned a factor, wherein the control unit (10) adjusts the unadjusted control signal ST* by multiplying by the factor.

12. The method according to any one of claims 9 to 10, characterized in that, The control unit (10) determines the adjusted control signal ST according to the functional relationship, taking into account the determined difference or the factor assigned to the value of the determined difference in the functional relationship, so as to adjust the unadjusted control signal ST* in consideration of the difference.

13. The method according to any one of claims 9 to 10, characterized in that, The control unit (10) adjusts the unadjusted control signal ST* such that the torque provided by the electric motor (5) increases when the determined difference is negative.

14. The method according to any one of claims 9 to 10, characterized in that, The steer-by-wire system (1) is a steering system according to any one of claims 1 to 8.

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