Method for operating a steer-by-wire steering system and sensor arrangement for a steer-by-wire steering system

Abstract

The invention relates to a method for operating a steer-by-wire steering system (1), wherein a first rotor position angle (16-1) of a rotor of an electric machine (8) of the steer-by-wire steering system (1) used for steering is detected by means of a first rotor position sensor (13-1), wherein a first number of revolutions (18-1) is determined on the basis of the detected first rotor position angle (16-1) by means of a first revolution counter (14-1), wherein a second rotor position angle (16-2) of the rotor is detected by means of a second rotor position sensor (13-2), wherein a second number of revolutions (18-2) is determined on the basis of the detected second rotor position angle (16-2) by means of a second revolution counter (14-2), and wherein in each case an absolute rotor position angle (19-x) is determined on the basis of the respectively detected rotor position angle (16-x) and the respectively determined number of revolutions (18-x) and is provided for controlling the steer-by-wire steering system (1).Furthermore, the invention relates to a sensor arrangement (11) for a steer-by-wire steering system (1).

Description

[0001] The invention relates to a method for operating a steer-by-wire steering system and a sensor arrangement for a steer-by-wire steering system.

[0002] Determining the rack position in a steer-by-wire steering system requires absolute position measurement (true power-on). Position determination must be significantly more precise than in conventional steering systems with a mechanical coupling to the steering wheel. This places special demands on the accuracy of the sensor technology and safety, and thus also represents a cost factor.

[0003] It is known to measure the rack position directly at the rack using a linear measurement method. Indirect measurement via a steering pinion that engages the rack is also known. This can be achieved, for example, using a rotary sensor. Due to the translation between the pinion angle and the rack, the sensor on the steering pinion requires high accuracy. Since the sensor must cover the entire steering stroke, a two-stage method using a reduction gear or the Vernier algorithm is used.

[0004] Steering systems are known, for example, from DE 10 2021 212 470 A1 and DE 600 24 692 T2.

[0005] The invention is based on the object of improving a method for operating a steer-by-wire steering system and a steer-by-wire steering system with regard to detecting a rack position, lifting rod position or push rod position.

[0006] The object is achieved according to the invention by a method having the features of patent claim 1 and a sensor arrangement for a steer-by-wire steering system having the features of patent claim 7. Advantageous embodiments of the invention emerge from the subclaims.

[0007] In particular, a method for operating a steer-by-wire steering system is provided, wherein a first rotor position angle of a rotor of an electric machine of the steer-by-wire steering system used for steering is detected by means of a first rotor position sensor, wherein a first number of revolutions is determined based on the detected first rotor position angle by means of a first revolution counter, wherein a second rotor position angle of the rotor is detected by means of a second rotor position sensor, wherein a second number of revolutions is determined based on the detected second rotor position angle by means of a second revolution counter, and wherein in each case an absolute rotor position angle is determined based on the respectively detected rotor position angle and the respectively determined number of revolutions and is provided for controlling the steer-by-wire steering system.

[0008] Furthermore, in particular, a sensor arrangement for a steer-by-wire steering system is created, comprising a first rotor position sensor which is configured to detect a first rotor position angle of a rotor of an electric machine of the steer-by-wire steering system used for steering, a first revolution counter which is configured to determine a first number of revolutions based on the detected first rotor position angle, a second rotor position sensor which is configured to detect a second rotor position angle of the rotor, a second revolution counter which is configured to determine a second number of revolutions based on the detected second rotor position angle, and in each case a control device, wherein the respective control device is configured to determine in each case an absolute rotor position angle based on the respectively detected rotor position angle and the respectively determined number of revolutions and to provide this for controlling the steer-by-wire steering system.

[0009] The method and the sensor arrangement make it possible to cost-effectively determine a rack position of a rack, a lifting rod position of a lifting rod, or a push rod position of a push rod of the steer-by-wire steering system. In particular, no additional gear or other moving parts are necessary for the method and the sensor arrangement. One of the basic ideas of the invention is that a high level of power supply availability must be ensured in any case in a steer-by-wire steering system. This can be used to simplify the detection of the rotor position angle of a rotor of an electrical machine used for steering and a rotor rotation speed. For this purpose, it is provided that the rotor position angle is detected in a redundant design and the rotation speed is determined based on the detected rotor position angle.For this purpose, a first rotor position sensor and a first revolution counter are provided in a first path, and a second rotor position sensor and a second revolution counter are provided in a second path, which operate in parallel and independently of one another. Based on the detected first rotor position angle and the first number of revolutions or the detected second rotor position angle and the second number of revolutions, the absolute rotor position angle can be determined. The absolute rotor position angle is in particular an angle that can be >360°, i.e. an angle at which the values ​​of several revolutions are accumulated. The rack position / lifting rod position / push rod position can then be determined from the absolute rotor position angle, in particular with the aid of a known transmission ratio between the rotor and the rack position / lifting rod position / push rod position.The determined absolute rotor position angle is then provided for controlling the steer-by-wire steering system. In particular, it is provided that a rack position / lifting rod position / push rod position determined on this basis is used to control a steering angle of at least one steerable wheel of the steer-by-wire steering system, which steering angle can be adjusted via the rack / lifting rod / push rod.

[0010] The steer-by-wire steering system is designed in a manner known per se and comprises, in particular, a steering module with the electric motor and a steering gear, and a steering wheel module with a sensor system for detecting a steering wheel angle and an actuator for applying a feedback torque (manual torque). The sensor arrangement is, in particular, part of the steering module. Apart from the sensor arrangement described in this disclosure, no position sensors (e.g., pinion stub sensor, linear sensor, etc.) are required, and in particular, they are not present on the electric motor and / or the rack / lifting rod / push rod.

[0011] The rotor position sensors and the revolution counters particularly meet Automotive Safety Integrity Level D (ASIL-D) with regard to providing the absolute rotor position angle.

[0012] A revolution counter (also referred to as a turn counter) is, in particular, a counter that counts the number of revolutions of the rotor. Counting takes place in both directions, i.e., depending on the direction in which the rotor is moving, the counter is increased or decreased by one. The revolution counter is controlled based on the sensor signals of at least one rotor position sensor. Provision can be made to count each full revolution of the rotor. Alternatively or additionally, provision can also be made to count half revolutions (180°, 360°) or quarter revolutions or quadrants (90°, 180°, 270°, 360°). Depending on the counting method, an absolute (or cumulative) rotor position angle can be determined from the value of the revolution counter and a value of the current rotor position angle (angle between 0° and 360°).From the absolute rotor position angle, a gear ratio can be used to determine the rack position / lifting rod position / push rod position and thus the steering angle. The revolution counters have a low current consumption, especially in idle or low-power mode (e.g., when the vehicle is in standby and / or not moving), especially <100 µA, preferably <80 µA.

[0013] The rotor position sensors can be designed, for example, as giant magnetoresistance (GMR) sensors, anisotropic magnetoresistance (AMR) sensors, or tunneling magnetoresistance (TMR) sensors. The rotor position sensors can also be designed as Hall sensors or inductive sensors.

[0014] Parts of the sensor arrangement, in particular the control devices, can be implemented individually or collectively as a combination of hardware and software, for example, as program code executed on a microcontroller or microprocessor. However, it can also be provided that parts are implemented individually or collectively as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA).

[0015] In one embodiment, a voltage supply for the first rotor position sensor and the first revolution counter is provided by a first on-board power supply, while a voltage supply for the second rotor position sensor and the second revolution counter is provided by a second on-board power supply. This increases robustness against a power failure. If one of the two on-board power supplies fails, the information on the number of revolutions is not lost and can continue to be provided.

[0016] In one embodiment of the sensor arrangement, it is accordingly provided that the first rotor position sensor and the first revolution counter on the one hand and the second rotor position sensor and the second revolution counter on the other hand have separate connections for the voltage supply, so that the first rotor position sensor and the first revolution counter can be supplied by means of a first on-board network and the second rotor position sensor and the second revolution counter can be supplied by means of a second on-board network.

[0017] In one embodiment, a voltage supply of the first rotor position sensor and the first revolution counter is supported by a first buffer capacitor in the event of a failure of the first on-board electrical system, and a voltage supply of the second rotor position sensor and the second revolution counter is supported by a second buffer capacitor in the event of a failure of the second on-board electrical system. This can further increase the robustness of the method and the sensor arrangement, since the information from the affected revolution counter can still be read out during the support period, so that the determination of the absolute rotor position angle remains possible.

[0018] In one embodiment of the sensor arrangement, it is accordingly provided that the sensor arrangement has a first buffer capacitor and a second buffer capacitor, wherein the first buffer capacitor is electrically connected to the first rotor position sensor and the first revolution counter for the voltage supply, wherein the second buffer capacitor is electrically connected to the second rotor position sensor and the second revolution counter for the voltage supply.

[0019] In one embodiment, it is provided that in a resting state of a vehicle having the steer-by-wire steering system, at least one of the vehicle electrical systems remains active in order to store a value of the first revolution counter and / or the second revolution counter. This can save energy because only one path needs to be operated. Nevertheless, a value for the number of revolutions can be made available to the steer-by-wire steering system after the vehicle is started. Together with a currently detected rotor position angle, the absolute rotor position angle (and from this the rack position / lift rod position / push rod position) can be determined, so that the steer-by-wire steering system is immediately ready for use.

[0020] In one embodiment, if only one active on-board electrical system fails and / or malfunctions in the foreseeable future, the other on-board electrical system is activated and a revolution number of the revolution counter fed by the other on-board electrical system is set to the value of the revolution number of the revolution counter fed by the failing on-board electrical system. This can ensure continued operation of the steer-by-wire steering system in the event of a failure. In particular, this can transfer the information on the revolution number from the failing path to the activated path. This is based on the idea that the failure of an on-board electrical system usually does not occur suddenly, but rather gradually.In particular, depending on the specific scenario, the voltage of the vehicle electrical system usually drops over several tens of milliseconds (short circuit, in particular buffered by a buffer capacitor), seconds, or even minutes (discharging when the vehicle is stationary, e.g., in winter). A trend in this drop can be used to estimate a point in time at which the supply to the consumers will no longer be sufficient. However, reading and setting the rotational speed is generally possible on timescales of a few tens to hundreds of microseconds. The measures described above in this embodiment are carried out particularly within this time, so that the information on the rotational speed is transferred to the revolution counter, which is supplied by the activated vehicle electrical system, within this time.

[0021] In one embodiment, if the revolution counts of both revolution counters are lost, the revolution count and / or the absolute rotor position angle of the steer-by-wire steering system are determined using a predefined determination method. This allows the steer-by-wire steering system to be made operational again. For example, there are several possibilities: a) During a workshop visit, the number of revolutions and / or the absolute rotor position angle are re-determined and determined in a conventional manner. b) It can be provided that a mechanical fixed point is provided on the steer-by-wire steering system (like the "TDC screw" in combustion engines). A mechanical fixed point allows a defined position in the steering system to be approached. To increase accuracy, this position can be saved for each component during production. For example, it can be provided that a screw provided for this purpose is fixed to a known Rack position / lifting rod position / push rod position. For this purpose, a threaded hole is provided at the designated position in the housing, into which a screw is screwed in case the number of revolutions and / or the absolute rotor position angle needs to be redetermined. A hole or recess etc. is provided in the rack / lifting rod / push rod at a predetermined position, into which the screw can engage. In this way, the rack / lifting rod / push rod can be moved to a precisely defined rack position / lifting rod position / push rod position, for example a center position. The number of revolutions can then be set to a corresponding value (e.g. 50 for 100 total revolutions) or the absolute rotor position angle can be set accordingly.The screw is then loosened again and the steer-by-wire steering system can operate normally again based on the speed and / or the absolute rotor position angle set in this way. c) The rotational speed and / or the absolute rotor position angle can also be determined using steering angles up to the end stops (reference run). In particular, the corresponding rotational speeds can be determined. Subsequently, based on the rotational speeds corresponding to the end stops, a rotational speed corresponding to a center position can be determined. For special vehicles (e.g., with all-wheel drive), a steering angle up to the end stops is sometimes not possible, so another of the described methods should be used. d) The number of revolutions and / or the absolute rotor position angle can also be determined solely from determining the number of revolutions of the rotor, without the need for steering angles up to the end stops. To do this, a driver is asked to steer to the center position of the steering system. Starting from a generally known number of total revolutions (e.g. ~100) that the rotor performs from one end stop to the other, the vehicle can now be steered step by step in both directions and a number of revolutions can be determined. Steering up to the end stops is avoided where possible by not exceeding maximum values ​​of the number of revolutions, which can be calculated from the number of total revolutions. e) In principle, it is also possible to use an additional sensor to determine a specific position based on steering angles, which can be used to determine the rotational speed and / or the absolute rotor position angle. For example, an index sensor, particularly on the ball screw drive, can be used for this purpose. Stiffness and belt stiffness can be taken into account by estimating the motor torque. f) Points c) to e) can be carried out in a workshop, by the driver of the vehicle or fully automatically.

[0022] In one embodiment, it is provided that a diagnostic state of at least the first revolution counter and the second revolution counter is read out, wherein the absolute rotor position angle is determined taking into account the respective diagnostic state. This allows the reliability (i.e., in particular, the trustworthiness) of the value detected in each case and provided by the revolution counters to be taken into account. In particular, the absolute rotor position angle can thereby be provided to ASIL-D. In particular, the revolution counters are designed and / or configured to independently perform a diagnosis. Such a diagnosis can, in particular, include whether a voltage supply to the revolution counter was always sufficient. If, for example, a supply voltage fell below a threshold value in the past, it may be that the number of revolutions provided by the revolution counter can no longer be trusted, etc.The revolution count provided by this revolution counter to the control device is then discarded, and the revolution count from the other revolution counter is used, provided its diagnostic status is OK. In the simplest case, the diagnostic status can be a diagnostic bit indicating error-free or faulty operation.

[0023] In one embodiment of the sensor arrangement, the first rotor position sensor, the first revolution counter, the second rotor position sensor, and the second revolution counter are arranged on a circuit board of the control device. This allows for an extremely compact design. In particular, the sensor arrangement can be installed simultaneously with the control device, thus saving production time and costs.

[0024] In one embodiment of the sensor arrangement, the first rotor position sensor, the first revolution counter, the second rotor position sensor, and the second revolution counter are arranged in a common package. This allows for an extremely compact design. Furthermore, the first rotor position sensor, the first revolution counter, the second rotor position sensor, and the second revolution counter can be arranged simultaneously on a circuit board, thus saving production time and costs.

[0025] It can be provided that the first revolution counter and / or the second revolution counter is designed as part of a power management IC (PMIC) or a respective rotor position sensor with integrated functionality.

[0026] Further features of the sensor arrangement will become apparent from the description of embodiments of the method. The advantages of the sensor arrangement are the same as those of the embodiments of the method.

[0027] Furthermore, a steer-by-wire steering system is also provided, comprising at least one sensor arrangement according to one of the described embodiments.

[0028] The invention will be explained in more detail below using preferred embodiments with reference to the figures. Fig. 1 a schematic representation to illustrate embodiments of the sensor arrangement; Fig. 2 a schematic representation to illustrate embodiments of the sensor arrangement; Fig. 3 a schematic flow diagram to illustrate an embodiment of the method.

[0029] The Fig. 1 shows a schematic representation to illustrate embodiments of the sensor arrangement 11. A steer-by-wire steering system 1 comprises, in a manner known per se, a steering wheel module 2, a steering module 3 and a communication connection 4 between the steering wheel module 2 and the steering module 3.

[0030] The steering wheel module 2 has a sensor 5 for detecting a steering wheel angle on a steering wheel 51 and an electric motor 6 for applying a feedback torque to the steering wheel 51. Furthermore, the steering wheel module 2 has a controller 7 for regulating the feedback torque.

[0031] The steering module 3 has an electric machine 8 for setting a steering angle on at least one steerable wheel 52. This is done, for example, via a steering gear 9, in which a rotation of a steering pinion is converted into a movement of a rack 53. As an alternative to the rack 53, a lifting rod or push rod can also be provided. The steering module 3 further has a control system 10 for regulating the steering angle. The sensor arrangement 11 is arranged on the electric machine 8. The method disclosed in this invention is implemented by means of the sensor arrangement 11.

[0032] The sensor arrangement 11 can be part of a control device 30 of the steering module 3. The sensor arrangement 11 has, in particular, a circuit board 12. Furthermore, the sensor arrangement 11 has a first rotor position sensor 13-1, a first revolution counter 14-1, a second rotor position sensor 13-2, and a second revolution counter 14-2. Furthermore, the sensor arrangement 11 has a control device 15-x for each of the paths. The control devices 15-x can also be formed as part of the rotor position sensors 13-x or the revolution counter 14-x.

[0033] The first rotor position sensor 13-1 is configured to detect a first rotor position angle 16-1 of a rotor 17 of the electric machine 8 used for steering. The second rotor position sensor 13-2 is configured to detect a second rotor position angle 16-2 of a rotor 17 of the electric machine 8 used for steering. For this purpose, the rotor position sensors 13-x are arranged near a permanent magnet 41 arranged on the rotor 17, so that a change in a magnetic field caused by the permanent magnet 41 caused by a rotation about a rotational axis 40 of the rotor 17 can be detected.

[0034] The first revolution counter 14-1 is configured to determine a first revolution number 18-1 based on the detected first rotor position angle 16-1. The second revolution counter 14-2 is configured to determine a second revolution number 18-2 based on the detected second rotor position angle 16-2.

[0035] The control device 15-1 is configured to determine an absolute rotor position angle 19-1 based on the detected first rotor position angle 16-1 and the determined first rotational speed 18-1 and to provide it for controlling the steer-by-wire steering system 1.

[0036] The control device 15-2 is configured to determine an absolute rotor position angle 19-2 based on the detected second rotor position angle 16-2 and the determined second rotational speed 18-2 and to provide it for controlling the steer-by-wire steering system 1.

[0037] Based on the absolute rotor position angles 19-x, a rack position of the rack 53 can be determined, since the absolute rotor position angles 19-x correspond to or are representative of the rack position of the rack 53. This can be done analogously for a lifting rod or a push rod. This can be done by means of one or both of the control devices 15-x or by another device, for example, the control device 30 of the steering module 3. One of the absolute rotor position angles 19-x can be used here. It can also be provided that both absolute rotor position angles 19-x are taken into account, for example by calculating an average value. Ideally, the values ​​of the detected rotor position angles 16-x and the determined rotational speeds 18-x are the same, so that the values ​​of the determined absolute rotor position angles 19-x are also the same.

[0038] It can be provided that in the case where the revolution numbers 18-x of both revolution counters 14-x have been lost, the revolution number 18-x and / or the absolute rotor position angle 19-x are determined by means of a predetermined determination method, as already described in the general description.

[0039] It can be provided that a diagnostic state 23-x of at least the first revolution counter 14-1 and the second revolution counter 14-2 is read out, wherein the absolute rotor position angle 19-x is determined taking into account the respective diagnostic state 23-x. The diagnostic state 23-x includes, in particular, information about how reliable the value provided by the revolution counter 14-x is. For example, it can be taken into account whether a voltage supply to the revolution counter 14-x has always been provided error-free in the past. In principle, such a diagnostic state can also be read out from the first rotor position sensor 13-1 and the second rotor position sensor 13-2 and taken into account when determining the absolute rotor position angle 19-x.

[0040] The Fig. 2 shows a schematic representation to illustrate embodiments of the sensor arrangement 11. For the sake of clarity, the control devices are not shown. In one embodiment, it is provided that the first rotor position sensor 13-1 and the first revolution counter 14-1, on the one hand, and the second rotor position sensor 13-2 and the second revolution counter 14-2, on the other hand, have separate connections 25-x for the voltage supply, so that the first rotor position sensor 13-1 and the first revolution counter 14-1 can be supplied by means of a first on-board electrical system 20-1, and the second rotor position sensor 13-2 and the second revolution counter 14-2 can be supplied by means of a second on-board electrical system 20-2. The on-board electrical systems 20-1, 20-2 each have a voltage bus VDC1, VDC2 and a ground conductor GND1, GND2.

[0041] It is thus provided that a voltage supply of the first rotor position sensor 13-1 and the first revolution counter 14-1 is provided by means of the first on-board network 20-1, and a voltage supply of the second rotor position sensor 13-1 and the second revolution counter 14-2 is provided by means of the second on-board network 20-2.

[0042] It can be provided that the sensor arrangement has a first buffer capacitor 21-1 and a second buffer capacitor 21-2, wherein the first buffer capacitor 21-1 is electrically connected to the first rotor position sensor 13-1 and the first revolution counter 14-1 for the voltage supply, and wherein the second buffer capacitor 21-2 is electrically connected to the second rotor position sensor 13-2 and the second revolution counter 14-2 for the voltage supply. In particular, the first buffer capacitor 21-1 is electrically connected to the first on-board electrical system 20-1, and the second buffer capacitor 21-2 is electrically connected to the second on-board electrical system 20-2.

[0043] It can be provided that the first rotor position sensor 13-1, the first revolution counter 14-1, the second rotor position sensor 13-2 and the second revolution counter 14-2 are arranged in a common package 22 (common housing), as shown schematically in the Fig. 2 is indicated.

[0044] It can be provided that in a rest state of a vehicle having the steer-by-wire steering system, at least one of the on-board networks 20-1, 20-2 remains active in order to keep a value of the first revolution counter 14-1 and / or the second revolution counter 14-2 stored.

[0045] The Fig. Figure 3 shows a schematic flow diagram illustrating one embodiment of the method. In this embodiment, it is provided that, in a rest state of a vehicle having the steer-by-wire steering system, one of the vehicle electrical systems remains active in order to store a value of the first revolution counter and / or the second revolution counter.

[0046] In action 100, a regular check is performed to determine whether the active on-board electrical system is operating correctly. For example, the check can determine a trend in a value of a provided supply voltage and check whether the value will fall below a specified minimum value in the foreseeable future, e.g., within the next 5, 10, or 30 minutes. If this is not the case, action 100 is repeated.

[0047] However, if this is the case, i.e. the supply voltage is expected to drop below the specified minimum value, the other, previously passive, on-board network is activated in a measure 101.

[0048] In a measure 102, a revolution number of the revolution counter, which is powered by the other, currently activated, on-board power supply, is set to the value of the revolution number of the revolution counter, which is powered by the failing on-board power supply. The activated on-board power supply can then provide the value for the revolution number even in the event of a failure of the faulty on-board power supply.

[0049] It may be provided that, in a measure 103, an error message is generated and provided that indicates the faulty state of the failing electrical system. For example, this error message can be displayed on a display to a user or transmitted to a workshop and / or a service provider. List of reference symbols 1 steer-by-wire steering system 2 steering wheel module 3 Steering module 4 Communication connection 5 Sensor (for steering wheel angle) 6 electric machine 7 Regulation 8 electric machine 9 Steering gear 10 Regulation 11 Sensor arrangement 12 circuit boards 13-1 first rotor position sensor 13-2 second rotor position sensor 14-1 first revolution counter 14-2 second revolution counter 15-x control device 16-1 first rotor position angle 16-2 second rotor position angle 17 Rotor 18-1 first revolution 18-2 second revolutions 19-1 first absolute rotor position angle 19-2 second absolute rotor position angle 20-1 first on-board network 20-2 second on-board network 21-1 first buffer capacitor 21-2 second buffer capacitor 22 joint package 23-x Diagnostic status 25-x connection 40 axis of rotation 41 Permanent magnet 51 Steering wheel 52 wheels 53 rack 100-103 Measures of the procedure QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 212 470 A1

[0004] DE 600 24 692 T2

[0004]

Claims

[1] Method for operating a steer-by-wire steering system (1), wherein a first rotor position angle (16-1) of a rotor of an electric machine (8) of the steer-by-wire steering system (1) used for steering is detected by means of a first rotor position sensor (13-1), wherein a first number of revolutions (18-1) is determined on the basis of the detected first rotor position angle (16-1) by means of a first revolution counter (14-1), wherein a second rotor position angle (16-2) of the rotor is detected by means of a second rotor position sensor (13-2), wherein a second number of revolutions (18-2) is determined from the detected second rotor position angle (16-2) by means of a second revolution counter (14-2), and wherein an absolute rotor position angle (19-x) is determined on the basis of the respectively detected rotor position angle (16-x) and the respectively determined number of revolutions (18-x) and is provided for controlling the steer-by-wire steering system (1). [2] Method according to claim 1, characterized by that a voltage supply of the first rotor position sensor (13-1) and the first revolution counter (14-1) is provided by means of a first on-board network (20-1), wherein a voltage supply of the second rotor position sensor (13-2) and the second revolution counter (14-2) is provided by means of a second on-board network (20-2). [3] Method according to claim 1 or 2, characterized by that a voltage supply of the first rotor position sensor (13-1) and the first revolution counter (14-1) is supported by means of a first buffer capacitor (21-1) in the event of a failure of the first on-board network (20-1), wherein a voltage supply of the second rotor position sensor (13-2) and the second revolution counter (14-2) is supported by means of a second buffer capacitor (21-2) in the event of a failure of the second on-board network (20-2). [4] Method according to one of the preceding claims, characterized bythat in a rest state of a vehicle having the steer-by-wire steering system (1), at least one of the on-board networks (21-x) remains active in order to keep a value of the first revolution counter (14-1) and / or the second revolution counter (14-2) stored. [5] Method according to one of the preceding claims, characterized by that if only one on-board network (20-x) is active and which fails in the foreseeable future and / or operates incorrectly, the other on-board network (20-x) is activated and a revolution number (18-x) of the revolution counter (14-x) which is fed by the other on-board network (20-x) is set to the value of the revolution number (18-x) of the revolution counter (14-x) which is fed by the failing on-board network (20-x). [6] Method according to one of the preceding claims, characterized bythat in the case where the revolution numbers (18-x) of both revolution counters (14-x) have been lost, the revolution number (18-x) and / or the absolute rotor position angle (19-x) is determined by means of a predetermined determination method. [7] Sensor arrangement (11) for a steer-by-wire steering system (1), comprising: a first rotor position sensor (13-1) configured to detect a first rotor position angle (16-1) of a rotor of an electric machine (8) of the steer-by-wire steering system (1) used for steering, a first revolution counter (14-1) configured to determine a first revolution number (18-1) based on the detected first rotor position angle (16-1), a second rotor position sensor (13-2) configured to detect a second rotor position angle (16-2) of the rotor, a second revolution counter (14-2) arranged to determine a second revolution number (18-2) based on the detected second rotor position angle (16-2), and each having a control device (15-x), wherein the respective control device (15-x) is configured to determine an absolute rotor position angle (19-x) based on the respectively detected rotor position angle (16-x) and the respectively determined first number of revolutions (18-x) and to provide it for controlling the steer-by-wire steering system (1). [8] Sensor arrangement (11) according to claim 7, characterized in that the first rotor position sensor (13-1) and the first revolution counter (14-1) on the one hand and the second rotor position sensor (13-2) and the second revolution counter (14-2) on the other hand have separate connections for the voltage supply, so that the first rotor position sensor (13-1) and the first revolution counter (14-1) can be supplied by means of a first on-board network (20-1) and the second rotor position sensor (13-2) and the second revolution counter (14-2) can be supplied by means of a second on-board network (20-2). [9] Sensor arrangement (11) according to claim 8, characterized bya first buffer capacitor (21-1) and / or a second buffer capacitor (21-2), wherein the first buffer capacitor (21-1) is electrically connected to the first rotor position sensor (13-1) and the first revolution counter (14-1) for supplying voltage, wherein the second buffer capacitor (21-2) is electrically connected to the second rotor position sensor (13-2) and the second revolution counter (14-2) for supplying voltage. [10] Steer-by-wire steering system comprising at least one sensor arrangement according to one of claims 7 to 9.

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