Electromechanical steering device and method for controlling a steering device of this kind

Abstract

The invention relates to an electromechanical steering device for a vehicle, said steering device having a steering wheel (10), a steering shaft to which the steering wheel (10) is fastened, a steering wheel actuator (16) which generates a reaction torque in response to the steering movement and generates a restoring torque or a steering torque and is connected to the steering shaft (12), a drive unit (24) which is connected to a steering linkage (26) for generating a steering movement of wheels (22) of the vehicle, and a central control unit (20) via which the drive unit (24) can be controlled on the basis of a detected steering movement of the steering wheel (10), wherein for the continuous and validatable determination of the position of the steering wheel (10), it is proposed that at least one relative position sensor (32, 34) is arranged on the steering wheel actuator (16), via which relative position sensor a movement of the steering wheel actuator (16) can be detected, and a signal transmitter (28) is arranged on the steering wheel (10) or the steering shaft (12), which signal transmitter interacts with a sensor switch (30) which receives and switches a signal of the signal transmitter (28) in a neutral position of the steering wheel (10), wherein the at least one relative position sensor (32, 34) and the sensor switch (30) are connected to the control unit (20) for data transmission.

Description

[0001] PP34567WO / mg 10 / 17 / 2025 AVL List GmbH

[0002] Electromechanical steering device and method for controlling such a steering device

[0003] The invention relates to an electromechanical steering device comprising a steering wheel, a steering shaft to which the steering wheel is attached, a steering wheel actuator generating a reaction torque and a restoring torque and which is at least indirectly connected to the steering shaft, a drive unit connected to a steering linkage for generating a steering movement of the vehicle's wheels, a central control unit by which the drive unit can be controlled depending on a detected steering movement of the steering wheel, and a method for controlling such a steering device.

[0004] Electromechanical steering systems, also known as steer-by-wire systems, completely eliminate a direct mechanical connection between a vehicle's steering wheel and the steering linkage, and thus to the wheels. Instead, there is only a data-transmitting or electrical connection between a control unit and a steering wheel actuator and a drive unit, which indirectly steers the wheels. Accordingly, each steering wheel position must be unambiguously assigned to a specific position of the drive unit and / or the wheels.In vehicles where steering is performed by a driver, the steering wheel actuator contains an electric motor that generates a torque opposing the driver's steering input. Depending on the design, this torque typically increases with increasing steering angle to simulate the feel of a direct steering system. Furthermore, the steering drive returns the steering wheel to its neutral position when no torque or opposing force is applied by the driver, or, for example, when a lane keeping assist system is engaged, to a position specified by the control unit. In autonomous vehicles, the steering wheel is directly controlled by the steering actuator, which directly provides the steering torque.PP34567WO / mg 17.10.2025 AVL List GmbH.

[0005] German patent application DE 10 2022 213 233 A1 discloses a steering system in which the movement of the steering wheel is transmitted to a steering shaft and from there to a movable element, which is moved axially by the rotation of the steering shaft. Furthermore, the steering system has a first and a second stop on two opposite sides of the movable element. A counterforce, dependent on the steering angle, is generated by two elastic elements arranged between the movable element and the stops. Additionally, the steering system has a support element that is carried by the movable element to generate an axial frictional force when the movable element is moved. The steering angle of the steering wheel is detected by an angle sensor, while a control device controls the support element to adjust the frictional force as a function of the steering wheel's steering angle. The elastic elements and the support element together form the steering wheel actuator.

[0006] Furthermore, an electromechanical steering system is known from DE 102023201 425 A1 in which both the steering wheel actuator generating the counterforce and the drive unit transmitting the steering movement to the wheels are designed as an electric motor.

[0007] A problem with existing designs is that absolute angle sensors are required to reliably detect the steering wheel's position and ensure a correct correlation between the steering wheel angle and the wheel angle. However, such absolute angle sensors are relatively expensive and sensitive to external magnetic fields. Therefore, multiple absolute angle sensors must be used for reliable position feedback, resulting in high manufacturing effort and costs for such a steering system.

[0008] Furthermore, to increase driving safety in the future, the steering angle of the steering wheel will be limited to 180° in both directions, so that the driver will no longer need to reach across the steering wheel, even in sharp turns. PP34567WO / mg 17.10.2025 AVL List GmbH

[0009] The task is therefore to provide an electromechanical steering device and an associated method for controlling such a steering device, which, compared to known designs, can be manufactured as cost-effectively as possible when the steering angle of the steering wheel is limited to 180° in both directions, and which provides a continuously verifiable, correct position signal. To this end, the calibration effort should be reduced compared to known designs, and recurring verification of the signal should be enabled.

[0010] This problem is solved by an electromechanical steering device having the features of main claim 1 and a method for controlling such a steering device having the features of claim 11.

[0011] The electromechanical steering device according to the invention comprises a steering wheel which is attached to a steering shaft and rotates accordingly with it. Furthermore, the steering device includes a steering wheel actuator connected to the steering shaft. This steering wheel actuator either generates a reaction torque to a steering movement by the driver and a return torque to return the steering wheel, particularly to its neutral position, or it directly generates a steering torque, which is particularly necessary in autonomous vehicles or lane-keeping assist systems. The steering device also consists of a drive unit connected to a steering linkage for generating a steering movement of the vehicle's wheels, so that the actual steering of the vehicle is generated via this drive unit.To correctly control the drive unit, it is connected to a central control unit, which allows the drive unit to be controlled based on a detected steering movement of the steering wheel. According to the invention, to correctly detect the steering movement, at least one relative position sensor is arranged on the steering wheel actuator, allowing for the detection of movement of the steering wheel actuator. A signal transmitter is also arranged on the steering wheel or steering shaft, interacting with a sensor switch that receives and activates a signal from the signal transmitter when the steering wheel is in a neutral position. To utilize these signals, the at least one relative position sensor and the sensor switch are connected to PP34567WO / mg 17.10.2025 AVL List GmbH.

[0012] The control unit is connected for data transmission. Such a relative position sensor typically consists of a signal transmitter, which is located on or formed by a moving part of the steering wheel actuator, and a signal receiver that converts the detected signals into electrical pulses, which are counted. Therefore, a defined starting position is always required to determine an absolute steering angle. This starting position is easily determined by the sensor switch, which can, for example, be a Hall effect switch, interacting with a permanent magnet located on the steering wheel or steering shaft. Thus, the signals from the relative position sensor can always be determined relative to the neutral position of the steering wheel, from which the signals from the relative position sensor can be counted.This results in a consistently verifiable and accurate signal for the steering wheel position, which can then be transmitted to the drive unit to adjust the wheels. This generates a reliable and reproducible signal with minimal manufacturing effort and cost.

[0013] Preferably, the steering wheel actuator includes a steering wheel electric motor. This is particularly suitable for generating an adjustable reaction torque in response to the torque applied by the driver and also for ensuring the correct return of the steering wheel by means of a corresponding torque when the driver does not intervene. Furthermore, such an electric motor is suitable for use in autonomous vehicles to actuate the steering wheel according to the integrated software of the control unit.

[0014] In a further preferred embodiment, the steering wheel actuator includes a gearbox through which the steering wheel electric motor is connected to the steering shaft. Such a gearbox, which is particularly designed as a reduction gearbox, allows for even more precise control of the steering movements, since the adjustment angle of the steering wheel between successive signals from the relative position sensor is smaller.

[0015] It is particularly preferred if one or two mechanical stops are provided on the steering wheel or steering shaft, which prevent steering movement in both directions. PP34567WO / mg 17.10.2025 AVL List GmbH

[0016] Limit each steering direction to a maximum steering angle of 180°. This limitation ensures that the steering wheel is always in the neutral position when a signal is generated at the shift sensor. Therefore, it is unnecessary to count the shift sensor signals, as this position is clearly defined. Furthermore, this makes steering easier for the driver, as reaching across the steering wheel is no longer required.

[0017] Driver comfort is further enhanced when the control unit defines two virtual stops. These stops allow the steering movement in both directions to be limited by generating a maximum counter-torque at the steering wheel electric motor, within a definable limit angle between 80° and 179°. This allows, for example, a limitation of the steering wheel rotation angle of 90° in both directions. This also prevents mechanical overload of the mechanical stops, as they are only engaged if the counter-torque is insufficient.

[0018] Furthermore, it is advantageous to have two relative position sensors on the steering wheel actuator, which can detect two signals that are out of phase with each other. These out-of-phase signals enable the electric motor's direction of rotation to be detected. This eliminates the need for additional measures for direction detection, such as storing the electric motor's commutation in the control unit.

[0019] In a further embodiment, at least one relative position sensor is designed as an incremental encoder. These incremental encoders are simple and inexpensive to construct, insensitive to temperature fluctuations, and very energy-efficient.

[0020] In a further embodiment of the invention, an encoder disk is arranged on a rotor or shaft of the steering wheel electric motor, which acts as a signal transmitter for the incremental encoder. Such an encoder disk can be designed with high resolution and also allows the arrangement of two PP34567WO / mg 17.10.2025 AVL List GmbH

[0021] Signal series with phase-shifted signals, each of which can be assigned to a relative position sensor to enable direction detection.

[0022] In an alternative embodiment, at least one relative position sensor is designed as a Hall sensor or Hall switch, which directly detects the changing electromagnetic field of the rotor during rotation. Such a Hall switch enables relative position detection based on the changing magnetic field of the rotor as it moves, allowing the rotor poles to be counted by the Hall sensor. This eliminates the need for a signal transmitter in the form of additional magnets.

[0023] Furthermore, it is advantageous if the steering system has a mechanical steering lock that allows the steering wheel to be fixed in its neutral position. Such a lock can be engaged, for example, immediately before the vehicle is switched off and can thus serve as an anti-theft device. Most importantly, however, this mechanical steering lock ensures that the steering wheel cannot be operated when the vehicle is switched off and is therefore in the neutral position when the engine is started, so that the sensor initialization is always correct.

[0024] In the inventive method for controlling such an electromechanical steering device, the neutral position of the steering wheel is detected via the sensor switch on the steering wheel or steering shaft when the vehicle is switched on. This is used to initialize the at least one relative position sensor and, each time the sensor switch is passed over during operation, to validate the data of the at least one relative position sensor. This procedure ensures that the relative position sensors always measure from the correct starting position when the vehicle is started, thus enabling the calculation of an absolute angle. This angle can be checked again during vehicle operation, i.e., while driving, each time the sensor switch is passed over to ensure that no errors occur in determining the absolute position. When the vehicle is switched on, an electrical PP34567WO / mg 17.10.2025 AVL List GmbH

[0025] The term "power supply" refers to the electrical supply to the relevant circuit, which can be initiated, for example, by starting the vehicle's engine, unlocking a door, or similar actions. Crucially, the vehicle's electrical supply must be active and not interrupted again before the journey begins.

[0026] In a further embodiment of the method, when the vehicle is switched on, the steering wheel is in the neutral position detected by the sensor switch. At least one relative position sensor is initialized to this neutral position when the vehicle is switched on, for example, when the vehicle is unlocked or the vehicle's drive system is started, thus establishing the zero point from which measurements are taken. From this neutral position, the steering wheel is then rotated, before the vehicle is set in motion, to a position corresponding to the position of the steering linkage, using the signals from the relative position sensors and measured values ​​stored in the control unit when the vehicle is switched off. It would also be conceivable to use, for example, the position of the wheels.During operation, the relative position sensors transmit data for determining the steering wheel position in real time to the control unit for further processing. The control unit then sends corresponding control signals in real time to the drive unit, which in turn turns the wheels to a position corresponding to the steering wheel position. When the vehicle is switched off, the steering wheel returns to its neutral position. This return to neutral ensures a correct starting point for determining the absolute steering angle each time the vehicle is started. For this purpose, only the data from the steering motor, corresponding to the steering angle of the wheels, is stored in the control unit when the vehicle is switched off. Thus, a reliable and unambiguous correspondence between the steering wheel position and the wheel position is established using simple means.Switching off the vehicle also refers to the subsequent disconnection of the electrical circuit. This can be initiated by locking the vehicle or switching off the vehicle's drive system. The electrical circuit is only interrupted once the steering wheel and steering lock are in the correct positions. PP34567WO / mg 17.10.2025 AVL List GmbH.

[0027] Preferably, the control unit stores the number of signals and the direction of rotation of the steering wheel for returning it to its neutral position, or detects the position of the wheels and uses this to return the steering wheel to the position corresponding to the position of the steering linkage. The initialization and validation of the relative position sensors for the neutral position can thus be used to set a correct absolute steering angle.

[0028] It is particularly advantageous if, after the vehicle's engine is switched off and the steering wheel is returned to its neutral position, the steering wheel is locked in the neutral position by the mechanical steering lock. This prevents the steering wheel from being turned after the engine is switched off and before it is restarted, thus ensuring that the correct neutral position of the steering wheel is always used to initialize the relative position sensors.

[0029] In a more advanced training course, after the vehicle is switched on and the relative position sensor is initialized, the mechanical steering lock is released, allowing the vehicle to be used for operation. This prevents initialization while the steering wheel is being turned.

[0030] This invention provides an electromechanical steering device and a method for controlling such a steering device, with which a steering angle can be reliably detected without the need for costly absolute angle sensors. The steering device according to the invention enables very precise and sensitive steering with an electromechanical steering system that exhibits high reliability and eliminates the need for recalibration due to signal shifts, for example, caused by temperature fluctuations. Furthermore, continuous signal monitoring takes place during operation. PP34567WO / mg 17.10.2025 AVL List GmbH

[0031] A non-limiting embodiment of an electromechanical steering device according to the invention is shown in the figure and is described below, as is the associated control method.

[0032] The figure shows a schematic representation of an embodiment of an electromechanical steering device according to the invention.

[0033] The electromechanical steering device shown in the figure consists of a steering wheel 10, which is attached to a steering shaft 12. The steering shaft 12 is rotated by the steering wheel 10 when the steering wheel 10 is turned. The end of the steering shaft 12 is connected to a gearbox 14 of a steering wheel actuator 16, which can be driven by a steering wheel electric motor 18 or subjected to a torque.

[0034] When the steering wheel 10 is turned by the driver, the movement is transmitted via the steering shaft 12 and the gearbox 14 to the steering wheel electric motor 18, where a reaction torque is generated. Additionally, the steering wheel electric motor 18 is controlled by a central control unit 20 according to stored software to generate a return torque, which, depending on the software used, also increases, for example, with increasing steering angle or increasing torque applied by the driver. Furthermore, the steering wheel electric motor 18 returns the steering wheel 10 to a neutral position when no steering force is applied by the driver. The neutral position is a position of the steering wheel 10 in which it is straight and the vehicle's wheels 22 have no steering angle, so that a vehicle would move in a straight line during operation.

[0035] The central control unit 20 is additionally connected to a drive unit 24 via data transmission. This drive unit can actuate a steering linkage 26 of the vehicle, which is connected to the wheels 22, in order to generate a steering angle at the wheels 22. The drive unit 24 typically also includes an electric motor 25, which is controlled by the central control unit 20, and a downstream transmission. PP34567WO / mg 17.10.2025 AVL List GmbH

[0036] In order to control the drive unit 24 according to the steering angle generated via the steering wheel 10, it is necessary to detect the steering angle of the steering wheel 10 exactly, so that each steering angle of the steering wheel 10 can be uniquely assigned a steering angle of the wheels 22.

[0037] For this purpose, a signal transmitter 28 is attached to the steering wheel 10 or the steering shaft 12, which corresponds to a sensor switch 30 serving as a signal receiver. In the present embodiment, a permanent magnet is attached to the steering shaft 12 as the signal transmitter 28, the magnetic field of which is measured by a Hall effect switch mounted nearby, which serves as the sensor switch 30. As soon as the signal transmitter 28 is positioned opposite the sensor switch 30, an electrical signal is generated in the sensor switch 30 and transmitted to the control unit 20, whereby the control unit 20 detects a neutral position of the steering wheel 10.

[0038] Furthermore, two relative position sensors 32, 34 are arranged on the steering wheel actuator 16. In this case, these sensors are designed as incremental encoders 33, 35 and are formed by two Hall effect switches 36, 37 as signal receivers and an encoder disk 38 as a signal transmitter. The encoder disk is attached to the end of a shaft 39 of the steering wheel electric motor 18 and has two tracks 40, 42 arranged out of phase with each other. The first track 40 interacts with the first Hall effect switch 36, and the second track 42 interacts with the second Hall effect switch 37. The phase shift of the two tracks 40, 42 enables the detection of the direction of rotation of a rotor 44 of the steering wheel electric motor 18, and thus of the steering wheel 10 or the steering shaft 12.

[0039] Additionally, a mechanical steering lock 46 is provided on the steering shaft 12. In the present embodiment, this consists of an electromagnetic actuator 48, which has a retractable pin 50 that can be inserted into a corresponding bore 52 in the steering shaft 12 when the steering wheel 10 is in the neutral position.

[0040] Furthermore, a mechanical stop 54 is formed on the steering shaft 12, which is connected to a counter-stop 56 on a PP34567WO / mg 17.10.2025 AVL List GmbH

[0041] The housing interacts. In the neutral position of the steering wheel 10, this mechanical stop 54 is arranged offset by 180° to the counter-stop 56, so that the steering wheel 10 can only be rotated by these 180° in both directions of rotation before the mechanical stop 54 meets the counter-stop 56 and thus prevents further rotation of the steering wheel 10.

[0042] To prevent such stops during normal vehicle operation, the maximum steering angle is limited by two additional virtual stops. These virtual stops are created by a corresponding control of the steering wheel actuator 16. The control unit 20 maximizes the torque of the steering wheel actuator 16 acting against the steering wheel movement when a limit angle of, for example, 90° is exceeded, thus preventing the driver from turning the steering wheel 10 beyond this defined limit angle.

[0043] When the vehicle is switched off, immediately before the electrical circuit is interrupted, the steering wheel 10 is moved to its neutral position via the steering wheel actuator 16, which is identified by the signal from the sensor switch 30. The signals generated by the first and second relative position sensors 32, 34, as well as the resulting direction of rotation of the steering wheel actuator 16, are stored in the control unit 20. Once this has occurred, the mechanical steering lock 46 is engaged, so that the steering wheel 10 can no longer be moved and is fixed in its neutral position.As soon as the driver wants to put the vehicle back into operation, and the electrical circuits are switched on accordingly (which can be initiated, for example, by unlocking the vehicle or starting the engine), the position of the steering wheel is identified as being in the neutral position by the sensor switch 30, and the two relative position sensors 32 and 34 are initialized. This means that the current position serves as the starting point for counting subsequent signals. Once this has occurred, the mechanical steering lock 46 is released, so that the steering wheel 10 can be operated again. This operation is initially carried out via the steering wheel actuator 16, which, using the stored values ​​regarding the direction and angle of rotation from when the vehicle was switched off, returns the steering wheel 10 to the position specified in PP34567WO / mg 17.10 via the control unit 20.2025 AVL List GmbH, the position of the wheels 22 corresponding to the position when the vehicle is parked. During subsequent operation of the vehicle, a counter-torque corresponding to the driver's steering movement is always generated at the steering wheel actuator 16, and the position of the rotor 44 or the shaft 39 of the steering wheel electric motor 18 is continuously recorded, or the signals from the two relative position sensors 32, 34 are counted from the initialization point and transmitted in real time to the control unit 20. The control unit 20 processes this data and transmits a corresponding control signal in real time to the drive unit 24, such that a unique steering position of the wheels 22 can be assigned to each steering angle of the steering wheel 10.Each time the steering wheel 10 returns to the neutral position, or each time it passes beyond this neutral position, a signal from the sensor switch 30 is again received by the central control unit 20 and used to validate the relative position sensors 32 and 34, or the values ​​determined by the relative position sensors 32 and 34, and thus to check their accuracy. Accordingly, if necessary, the point in time when the steering wheel 10 passes beyond the neutral position, if there is a deviation from the position determined by the relative position sensors 32 and 34, can be used as a new initialization point. This allows errors in the counting of the two relative position sensors 32 and 34 to be either immediately eliminated or at least detected.When the journey ends and the engine is switched off or the vehicle is locked, the circuit initially remains open, allowing the steering wheel 10 to be turned back to its neutral position and the mechanical steering lock 46 to be re-engaged. The values ​​for the steering wheel 10's direction of rotation and the corresponding angle of rotation are then stored again in the central control unit 20 until the neutral position is reached. The circuit is then interrupted and the vehicle is switched off. When the journey resumes, the described steps are repeated.

[0044] The described electromechanical steering device and the associated method for controlling this steering device are suitable for both driver-operated and autonomous vehicles. The steering device is very simple and inexpensive to manufacture and exhibits high reliability. Errors due to signal shifts, such as those that can occur with absolute angle sensors due to temperature changes, are reliably avoided. Instead, the data from the relative position sensors is continuously monitored by comparing their data with the signals from the sensor switch when the vehicle passes over the neutral position.

[0045] It should be clear that, in addition to the described embodiment, other implementations of the invention are conceivable. In particular, sensors that function differently than the described sensors that react to a magnetic field can be used. For example, an optical switch can be used instead of a Hall effect switch. Furthermore, it is conceivable to use a Hall effect switch instead of the described incremental encoder, via which the signals from the movement of the permanent magnets of the steering wheel electric motor's rotor are used directly. Additionally, the stops and the steering lock can, of course, be designed differently. Various designs for controlling the steering wheel actuator are also known, but these can all typically be implemented with the described steering device.

Claims

PP34567WO / mg 17.10.2025 AVL List GmbH Patentansprüche 1. Electromechanical steering device for a vehicle comprising a steering wheel (10), a steering shaft to which the steering wheel (10) is attached, a steering wheel actuator (16) which generates a reaction torque to the steering movement and a return torque or a steering torque and which is connected to the steering shaft (12), a drive unit (24) which is connected to a steering linkage (26) for generating a steering movement of the wheels (22) of the vehicle, a central control unit (20) via which the drive unit (24) can be controlled depending on a detected steering movement of the steering wheel (10), characterized in that at least one relative position sensor (32, 34) is arranged on the steering wheel actuator (16) via which a movement of the steering wheel actuator (16) can be detected, and a signal transmitter (28) is arranged on the steering wheel (10) or the steering shaft (12) which interacts with a sensor switch (30).which receives and switches a signal from the signal generator (28) in a neutral position of the steering wheel (10), wherein at least one relative position sensor (32, 34) and the sensor switch (30) are connected to the control unit (20) for data transmission.

2. Electromechanical steering device according to claim 1, characterized in that the steering wheel actuator (16) has a steering wheel electric motor (18).

3. Electromechanical steering device according to claim 2, characterized in that the steering wheel actuator (16) has a transmission (14) via which the steering wheel electric motor (18) is connected to the steering shaft (12).

4. Electromechanical steering device according to one of the preceding claims, characterized in that PP34567WO / mg 17.10.2025 AVL List GmbH on the steering wheel (10) or on the steering shaft (12) one or two mechanical stops (56) are formed which limit a steering movement in both steering directions to a maximum steering angle of 180°.

5. Electromechanical steering device according to one of claims 2 to 4, characterized in that two virtual stops are defined in the control unit (20) via which the steering movement in both directions can be restricted by generating a maximum counter-torque at the steering wheel electric motor (18) over a definable limit angle between 80° and 179°.

6. Electromechanical steering device according to one of claims 2 to 5, characterized in that two relative position sensors (32, 34) are arranged on the steering wheel actuator (16), via which two signals that are phase-shifted relative to each other can be detected.

7. Electromechanical steering device according to one of the preceding claims, characterized in that the at least one relative position sensor (32, 34) is designed as an incremental encoder (33, 35).

8. Electromechanical steering device according to claim 7, characterized in that an encoder disk (38) is arranged on a rotor (44) or a shaft (39) of the steering wheel electric motor (18), which serves as a signal generator for the incremental encoder (33, 35).

9. Electromechanical steering device according to one of claims 2 to 6, characterized in that the at least one relative position sensor (32, 34) is designed as a Hall sensor, via which the electromagnetic field of the rotor (44) of the steering wheel electric motor (18) which changes during rotation can be detected directly. PP34567WO / mg 10 / 17 / 2025 AVL List GmbH 10. Electromechanical steering device according to one of the preceding claims, characterized in that the steering device has a mechanical steering lock (46) by which the steering wheel (10) can be fixed in its neutral position.

11. Method for controlling an electromechanical steering device according to one of the preceding claims, characterized in that the neutral position of the steering wheel (10) is detected via the sensor switch (30) on the steering wheel (10) or the steering shaft (12) when the vehicle is switched on and is used to initialize the at least one relative position sensor (32, 34) and is used to validate the data of the at least one relative position sensor (32, 34) each time the sensor switch (30) is passed over during operation.

12. Method for controlling an electromechanical steering device according to claim 11, characterized in that - when the vehicle is switched on, the steering wheel (10) is in the neutral position detected via the sensor switch (30), - which at least one relative position sensor (32, 34) is initialized to this neutral position when the vehicle is switched on, - from this neutral position the steering wheel (10) is turned into a position which corresponds to the position of the steering linkage (26) and the wheels (22) by using the signals from the relative position sensors (32, 34) and measured values ​​stored in the control unit (20) when the vehicle is switched off, by means of the control unit (20). - via the relative position sensors (32, 34) during vehicle operation, the data for determining the steering wheel position are transmitted in real time to the control unit (20) for further processing, and the control unit (20) transmits corresponding control signals to the drive unit (24), so that the wheels (22) are controlled in real time PP34567WO / mg 17.10.2025 AVL List GmbH via the drive unit (24) to be rotated into a position corresponding to the steering wheel position, - when the vehicle is switched off, the steering wheel (10) is turned back to its neutral position.

13. Method for controlling an electromechanical steering device according to one of claims 11 or 12, characterized in that the number of signals and the direction of rotation of the steering wheel (10) for returning the steering wheel (10) to its neutral position are stored in the control unit (20) and are used to return the steering wheel (10) to the position corresponding to the position of the steering linkage (26) and the wheels (22).

14. Method for controlling an electromechanical steering device according to one of claims 11 to 13, characterized in that after the vehicle is switched off and the steering wheel (10) is turned back to its neutral position, the steering wheel (10) is fixed in the neutral position by the mechanical steering lock (46).

15. Method for controlling an electromechanical steering device according to claim 14, characterized in that after switching on the vehicle and initializing the relative position sensor (32, 34) the mechanical steering lock (46) is released.

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