Steer-by-wire system with networked subsystem and method of operating steering-by-wire system

Abstract

The invention relates to a steer-by-wire system (1) for a motor vehicle, comprising a first subsystem (101) and a second subsystem (102), wherein the first subsystem (101) comprises a steering shaft (2), a steering handle (3) arranged in a rotationally fixed manner at one end of the steering shaft, a feedback actuator (5), an absolute angle sensor unit (7) for determining an absolute steering angle of the steering shaft (2), and a relative angle sensor unit (4) for determining a relative steering angle of the steering shaft (2), and the second subsystem (102) comprises a steering actuator unit (9), a coupling element (12), an absolute position sensor unit (15) for determining an absolute position of the coupling element (12), and a relative position sensor unit (16) for determining a relative position of the coupling element (12). In order to improve fault robustness, the first subsystem (101) and the second subsystem (102) are interconnected by a communication connection (20), where the communication connection (20) is configured to transmit sensor data (32) from the first subsystem (101) to the second subsystem (102) and to transmit sensor data (31) from the second subsystem (102) to the first subsystem (101). The invention further relates to a method for operating the steering-by-wire system.

Description

[0001] The present invention relates to a steer-by-wire system for a motor vehicle, comprising a first subsystem and a second subsystem. The first subsystem comprises a steering shaft, a steering handle arranged in a rotationally fixed manner at one end of the steering shaft, a feedback actuator, an absolute angle sensor unit for determining the absolute steering angle of the steering shaft, and a relative angle sensor unit for determining the relative steering angle of the steering shaft. The second subsystem comprises a steering actuator unit, a coupling element (particularly a gear rack), an absolute position sensor unit for determining the absolute position of the coupling element, and a relative position sensor unit for determining the relative position of the coupling element. Furthermore, the present invention relates to a method for operating such a steer-by-wire system.

[0002] Steer-by-wire systems are widely described in the prior art. For example, DE 10 2018 114 988 A1 discloses a steer-by-wire system having a steering handle, a feedback actuator, and a steering actuator, wherein a steering command can be specified via the steering handle, which is converted by the steering actuator into a steering movement of the steerable wheels of the motor vehicle. One challenge of steer-by-wire systems is to maintain controllability of the motor vehicle even in the event of a malfunction of the steer-by-wire system. To this end, DE 10 2020 100719 A1 proposes that, in the case of a motor vehicle with a front-axle steering system and a rear-axle steering system, the faulty steering system be switched off in the event of a malfunction of the front-axle or rear-axle steering system, and that the steering movement be activated via an automated driving mode or a target action derived therefrom.

[0003] Furthermore, DE 10 2019 217 588 A1 discloses that, when a vehicle collision causes the wheels on one or more axles to no longer be fully steerable or completely unsteerable, steering can be achieved via a functional steering axle, and a braking signal can be transmitted to a wheel connected to the steering axle. Furthermore, it is also known that components of a steer-by-wire system can be designed to be redundant so that, if a component fails, its corresponding function can be performed by a redundant component. For example, DE 10 2020 209 270 A1 discloses a redundantly designed control unit that can be used in a steer-by-wire system. US 2022 / 0001916 A1 also discloses a redundant design of steer-by-wire system components.

[0004] Furthermore, DE 10 2004 008 203 A1 discloses a system and method for initial wheel alignment of a motor vehicle steer-by-wire system. In this case, the steer-by-wire system includes a first subsystem having a steering shaft, a steering handle arranged on the steering shaft, a steering wheel actuator with an associated electromechanical output stage, an absolute angle sensor unit for determining the absolute steering angle of the steering shaft, a relative sensor unit for determining the relative steering angle of the steering shaft, and a steering wheel controller. Furthermore, the steer-by-wire system includes a second subsystem having steerable wheels that can be steered by wheel actuators associated with the respective steerable wheels, wherein the wheel actuators are controlled by the wheel controller via their respective electromechanical output stages. The second subsystem includes wheel sensors for determining the relative and absolute wheel angles. Sensor data can be transmitted between the steering wheel controller of the first subsystem and the wheel controller of the second subsystem.

[0005] A similar steer-by-wire system is described in DE 10 2004 030 685 A1. This steer-by-wire system is configured to support model-based fault detection, whereby redundancy is analyzed rather than additional hardware components to reduce costs and increase reliability.

[0006] On this basis, there is still a need to maintain controllability even when a fault occurs in or around the steer-by-wire system, thereby further reducing the risk of personal injury.

[0007] In view of the above, an object of the present invention is to further improve steer-by-wire systems and methods of operating the same, and in particular to provide a cost-effective method for eliminating potential errors when measuring essential parameters in steer-by-wire systems.

[0008] To achieve this object, a steer-by-wire system is provided as claimed in claim 1 and a method for operating a steer-by-wire system is provided as claimed in the other independent claim. Further advantageous embodiments of the invention are described in the dependent claims, the description and the drawings.

[0009] The proposed solution provides a steer-by-wire system for a motor vehicle, comprising a first subsystem and a second subsystem. The first subsystem includes a steering shaft, a steering handle, in particular a steering wheel, disposed rotationally fixedly at one end of the steering shaft, a feedback actuator, an absolute angle sensor unit for determining the absolute steering angle of the steering shaft, and a relative angle sensor unit for determining the relative steering angle of the steering shaft. In particular, a rotor position sensor unit associated with the electric motor of the feedback actuator serves as the relative angle sensor unit. The second subsystem includes a steering actuator unit, a coupling element, in particular a gear rack, an absolute position sensor unit for determining the absolute position of the coupling element, and a relative position sensor unit for determining the relative position of the coupling element. In particular, a rotor position sensor unit associated with the electric motor of the steering actuator unit serves as the relative position sensor unit. According to the present invention, in the steer-by-wire system, the first and second subsystems are connected to each other via a communication connection, wherein the communication connection is configured to transmit sensor data from the first subsystem to the second subsystem and vice versa. This design advantageously improves the exchange of sensor data between the subsystems. In particular, in the event of a failure in a subsystem, the sensor data can still be transferred to the remaining functional subsystem in an improved manner. In particular, the communication connection is designed to be redundant.

[0010] According to a particularly advantageous refinement, the steer-by-wire system includes a third subsystem, wherein the third subsystem includes an interface with a backup steering system, and the communication connection is advantageously configured to transmit sensor data from the first and / or second subsystems to the third subsystem. The interface is advantageously configured to transmit the sensor data transmitted to the third subsystem to the backup steering system. The backup steering system preferably comprises one or more vehicle assemblies that implement steering control by modifying their original functions. In particular, the backup steering system may include a correspondingly controlled braking system and / or a correspondingly controlled drive system and / or a correspondingly controlled active chassis system. When the steer-by-wire system fails and the backup steering system must be activated, the relevant sensor data for steering the motor vehicle can advantageously be transmitted to the third subsystem via the communication connection, and further to the backup steering system, thereby enhancing the functionality of the backup steering system. In particular, an overall steering system is provided, comprising a steer-by-wire system and a backup steering system. In this design, the third subsystem is incorporated into the overall steering system, particularly the backup steering system. The overall steering system can be particularly designed as a steer-by-wire system according to the present invention with a supplementary backup steering system.

[0011] One embodiment provides that each subsystem is associated with a control unit, in particular an ECU (Electronic Control Unit). In this case, each subsystem can include a control unit. However, an advantageous embodiment provides a central control unit, wherein control subunits of the central control unit are respectively assigned to the respective subsystems as control units.

[0012] An advantageous embodiment of the steer-by-wire system according to the present invention provides that the communication connection is implemented via the vehicle communication network, in particular via CAN (Controller Area Network) and / or via dedicated communication channels between the subsystems. In particular, the communication connection is designed as a high-level communication connection. In particular, the communication connection is implemented at least at Layer 2 of the ISO / OSI reference model. The communication connection is preferably implemented in a wired manner. However, according to one embodiment, a communication connection that is fully or partially wireless, in particular a radio connection, can also be provided.

[0013] Furthermore, it is particularly advantageous if the second subsystem of the steer-by-wire system, in particular the steering actuator unit of the second subsystem, is designed to receive the angle measurement values ​​provided by the absolute angle sensor unit included in the first subsystem, in particular via a first direct communication interface with the absolute angle sensor unit. The angle measurement values ​​acquired by the absolute angle sensor unit are advantageously transmitted directly to the second subsystem, in particular to the steering actuator unit, and in particular to a control unit associated with the steering actuator unit. In particular, the absolute angle sensor unit is directly connected to the second subsystem via a wired connection. Thus, the second subsystem is advantageously designed to directly receive the steering information used to set the correct wheel steering angle. In particular, as one embodiment, the first communication interface is not included in the communication connection, but is instead configured separately.

[0014] The second subsystem, in particular the steering actuator unit, is also preferably designed to supply the absolute angle sensor unit with the energy required for operation via a direct connection, in particular via the first direct communication interface. Advantageously, the required operating voltage is provided by the second subsystem in a controlled manner. Advantageously, the absolute angle sensor unit is independent of the energy supply of the first subsystem.

[0015] According to another advantageous embodiment of the steer-by-wire system, the first subsystem is designed to receive position measurement values ​​provided by an absolute position sensor unit, in particular via a second direct communication interface to the absolute position sensor unit. In particular, these position measurement values ​​determine the absolute position of the coupling element of the second subsystem and, therefore, the set wheel steering angle of the steered wheels of the motor vehicle. The position measurement values ​​acquired by the absolute position sensor unit are preferably transmitted directly to the first subsystem, in particular directly to the feedback actuator and, furthermore, directly to the control unit assigned to the first subsystem. In particular, the absolute position sensor unit is directly connected to the second subsystem via a wired connection. The first subsystem is therefore advantageously designed to directly receive position measurement values ​​regarding the specific position of the coupling element and, therefore, in particular, information regarding the set wheel steering angle. In particular, as a design variant, the second communication interface is not included in the communication connection, but is formed separately. Furthermore, in particular, the first communication interface and the second communication interface can be assigned to a common communication channel.

[0016] The first subsystem is designed to provide the absolute position sensor unit with the energy required for operation, preferably via a direct connection, in particular via the second direct communication interface. Advantageously, the voltage required for operation of the absolute position sensor unit is provided in a controlled manner by the first subsystem. The absolute position sensor unit is preferably independent of the energy supply of the second subsystem.

[0017] Another advantageous embodiment provides that the steer-by-wire system is designed to operate in different operating modes in a motor vehicle. In particular, the steer-by-wire system is configured for trouble-free operation of the steer-by-wire system in a first operating mode. This first operating mode is a normal operating mode in which the steer-by-wire system operates normally.

[0018] Furthermore, in particular, the steer-by-wire system is configured in a second operating mode to operate in the event of a failure, in particular a complete failure, of the first subsystem. This second operating mode preferably enables the steer-by-wire system to steer the motor vehicle via the second subsystem even in the event of a failure of the first subsystem.

[0019] In particular, the steer-by-wire system is also specifically designed with a third operating mode, which is activated in the event of a malfunction, particularly a complete failure, of the second subsystem, particularly its steering actuator unit. This third operating mode preferably allows the steer-by-wire system to steer the motor vehicle via the backup steering system in the event of a failure of the second subsystem, particularly the steering actuator unit. Sensor data acquired by sensors of the first and second subsystems, particularly information regarding the absolute angle of the steering axis and the absolute position of the coupling element, is advantageously provided to the backup steering system via the first subsystem.

[0020] The present invention also provides a method for operating a steer-by-wire system in a motor vehicle, in particular a steer-by-wire system configured as claimed in any one of claims 1 to 9, comprising the following steps: In a first operating mode configured for trouble-free operation, a second subsystem acquires angle measurement values ​​provided by an absolute angle sensor unit, converts the acquired angle measurement values ​​into corresponding angle information, and provides this angle information to the first subsystem via a communication connection. Furthermore, this angle information is preferably also provided to a third subsystem. The angle information is in particular sensor data within the meaning of the present invention. The first subsystem of the steer-by-wire system in this case particularly comprises a steering shaft, a steering handle arranged in a rotationally fixed manner at one end of the steering shaft, a feedback actuator, an absolute angle sensor unit for determining an absolute steering angle of the steering shaft, and a relative angle sensor unit for determining a relative steering angle of the steering shaft. The second subsystem particularly comprises a steering actuator unit, a coupling element, an absolute position sensor unit for determining an absolute position of the coupling element, and a relative position sensor unit for determining a relative position of the coupling element. The third subsystem specifically includes an interface with a backup steering system, wherein the backup steering system is implemented in particular by actuating active vehicle components, in particular brakes associated with the vehicle's wheels, drive units, and / or active chassis components. Because the second subsystem acquires the angle measurements provided by the absolute angle sensor unit, these angle measurements are available to the second subsystem even in the event of at least a partial failure of the first subsystem. During fault-free normal operation, the first subsystem preferably processes the angle information transmitted to the first subsystem via the communication connection.

[0021] In particular, it is provided that the first subsystem obtains angle information provided via the communication connection and determines the absolute steering axis angle based on the angle information and the relative steering axis angle obtained by the relative angle sensor unit. This determination of the absolute steering axis angle is preferably performed upon (re)startup to preliminarily determine the absolute steering axis angle. For subsequent operations, it is particularly provided that the determination of the absolute steering axis angle is also performed, at least optionally, based on consideration of the preliminarily determined absolute steering axis angle and the obtained relative steering axis angle.

[0022] According to a further advantageous embodiment, in a first operating mode configured for trouble-free operation, the first subsystem acquires position measurement values ​​provided by the absolute position sensor unit, wherein the first subsystem preferably converts the acquired position measurement values ​​into corresponding position information about the position of the coupling element, and the first subsystem preferably provides this position information to the second subsystem via a communication connection. Furthermore, this position information is preferably also provided to the third subsystem. Position information in this context is, in particular, sensor data within the meaning of the present invention. Thus, even if the second steering system at least partially fails, these position measurement values ​​can advantageously be used by the first subsystem and, in particular, can be provided as position information to the third subsystem and, in particular, to the backup steering system of the motor vehicle, so that, in the event of a failure of the second steering system, the motor vehicle can advantageously be steered in an improved manner by the backup steering system.

[0023] In particular, it is provided that the second subsystem, in particular the steering actuator unit of the second subsystem, more specifically the evaluation unit assigned to the steering actuator unit, receives position information provided via the communication connection and preferably determines the absolute position of the coupling element based on this position information and the relative position of the coupling element determined by the relative position sensor unit. This determination of the absolute coupling element position is preferably performed upon (re)starting the steer-by-wire system in order to initially determine the absolute coupling element position. For subsequent operations, it is particularly provided that the determination of the absolute coupling element position is also performed, at least optionally, based on the initially determined absolute coupling element position and the determined relative position of the coupling element.

[0024] According to an advantageous improvement of the method, it is provided that, in the third operating mode, due to an error in the second subsystem, the motor vehicle is steered by means of the backup steering system, the first subsystem determines the absolute angle of the steering axis based on the relative angle of the steering axis acquired by the relative angle sensor unit and the previously determined absolute angle of the steering axis, and the determined absolute angle is preferably provided to the third subsystem together with the converted position information, wherein the interface of the third subsystem preferably forwards the determined absolute angle and the position information to the backup steering system. The absolute angle of the steering axis is determined in particular during trouble-free operation. The information transmitted to the third subsystem, in particular the absolute angle and position information of the steering axis, is in particular sensor data in the sense of the present invention. With the aid of the sensor data transmitted in this way, the backup steering system can advantageously be configured in an improved manner for maneuvering the motor vehicle according to the steering command.

[0025] Another advantageous embodiment of the method provides that in the second operating mode, if the first subsystem fails and is unable to provide position information, the second subsystem determines the absolute coupling element position based on the relative position of the coupling element determined by the relative position sensor unit and the previously determined absolute position of the coupling element, wherein the information about the absolute angle of the steering axis is directly obtained by the absolute angle sensor unit. The absolute position of the coupling element is determined in this case, particularly during trouble-free operation. Thus, even in the event of a serious fault in the first subsystem, the motor vehicle can still be steered using the second subsystem.

[0026] According to a further embodiment, the proposed steer-by-wire system is also preferably designed to operate according to a method designed according to the present invention.

[0027] Other advantageous details, features and design details of the present invention will be described in more detail in conjunction with the embodiments shown in the accompanying drawings. In the drawings:

[0028] Figure 1 : Schematically showing an embodiment of a steer-by-wire system designed according to the present invention in a perspective view;

[0029] Figure 2 : Schematically illustrating another embodiment of a steer-by-wire system designed according to the present invention;

[0030] Figure 3 : An embodiment of a method for operating a steer-by-wire system designed according to the present invention is shown in the form of a block diagram.

[0031] In different figures, the same components are generally denoted by the same reference numerals and are therefore sometimes described only in one figure.

[0032] Figure 1 An embodiment of a steer-by-wire system 1 designed according to the present invention is shown, suitable for use in a motor vehicle having a first subsystem 101 and a second subsystem 102. The first subsystem 101 of the steer-by-wire system 1 comprises a steering column with a steering shaft 2 and a feedback actuator 5. A steering handle 3, configured as a steering wheel, is disposed rotationally fixedly at one end of the steering shaft 2. A vehicle user can specify steering commands via the steering handle 3. The feedback actuator 5 is designed to apply a torque or a steering resistance torque to the steering shaft 2, in particular to transmit a steering feel. This steering resistance torque is perceptible to the driver of the motor vehicle as steering resistance via the steering handle 3.

[0033] The steering handle 3 of the steer-by-wire system 1 can be rotated in a known manner, thereby inputting steering commands to the steering shaft 2, which are then captured by a sensor. To this end, the first subsystem 101 in this embodiment includes an absolute angle sensor unit 7, which is mounted on the steering shaft 2 and is designed to capture the angle set by the steering handle 3 as the absolute steering angle of the steering shaft 2. Furthermore, the motor 6 of the feedback actuator 5 of the first subsystem 101 is equipped with a relative angle sensor unit 4. In this embodiment, this relative angle sensor unit 4 is a rotor position sensor. The relative steering angle of the steering shaft 2 can be captured by this rotor position sensor.

[0034] The second subsystem 102 of the steer-by-wire system 1 includes the steering actuator unit 9. In the present embodiment, the steering actuator unit 9 includes a steering pinion 11 and an electric motor 10 that drives the steering pinion 11. The steering pinion 11 is driven by the electric motor 10 and, through actuation of the steering actuator unit 9, converts steering commands into steering movements of steerable wheels 14. The steering actuator unit 9, via the electric motor 10 and the steering pinion 11, acts on a coupling element 12, designed as a rack, thereby initiating steering movements of the motor vehicle's steerable wheels 14. These wheels 14 are connected to the coupling element 12, in particular, via tie rods 13. The tie rods 13 are themselves connected to the steerable wheels 14 in a known manner via steering knuckles. The second subsystem 102 also includes an absolute position sensor unit 15 for determining the absolute position of the coupling element 12 and a relative position sensor unit 16 for determining the relative position of the coupling element 12. In the present embodiment, the rotor position sensor of the electric motor 10 associated with the steering actuator unit 9 is used as the relative position sensor unit 16.

[0035] In this embodiment, the steering actuator unit 9 of the second subsystem 102 provides the required operating energy for the absolute angle sensor unit 7 included in the first subsystem 101 and directly receives the angle measurement values ​​output by the absolute angle sensor unit 7. To this end, the steering actuator unit 9 is connected to the absolute angle sensor unit 7 via a first direct communication interface 34 (which is included in the communication channel 18). SENT or SPC is preferably used as the communication protocol for transmitting the angle measurement values. These angle measurement values ​​are then converted into corresponding angle information by the second subsystem 102 or a control unit assigned to the second subsystem 102 and transmitted to the first subsystem 101 via the high-level communication connection 20. There, the first subsystem 101, and in particular the control unit assigned to it, combines the received angle information 31 with the measurement values ​​provided by the relative angle sensor unit 4 to determine the absolute steering axis angle.

[0036] Similarly, in this embodiment, the first subsystem 101, and in particular the feedback actuator 5 of the first subsystem 101, provides the energy required to operate the absolute position sensor unit 15 and directly receives the position measurement values ​​provided by the absolute position sensor unit 15. To this end, the feedback actuator 5 is connected to the absolute position sensor unit 7 via a second direct communication interface 35, which is also included in the communication channel 18. SENT or SPC is preferably used as the communication protocol for transmitting the angle measurement values. The position measurement values ​​are then converted by the first subsystem 101 or a control unit assigned to the first subsystem 101 into corresponding position information 32 and transmitted to the second subsystem 102 via the high-level communication connection 20.

[0037] The communication connection 20 thus connects the first subsystem 101 and the second subsystem 102 to one another, wherein in particular the position information 32 determined by the first subsystem 101 is transmitted to the second subsystem 102 via the communication connection 20 , while the angle information 31 determined by the second subsystem 102 is transmitted to the first subsystem 101 .

[0038] Figure 2 Another embodiment of a steer-by-wire system 1 designed according to the present invention is shown. The steer-by-wire system 1 includes a first subsystem 101, a second subsystem 102, and a third subsystem 103. The first subsystem 101 includes a steering shaft 2, a steering handle 3 disposed rotationally fixedly at one end of the steering shaft, a feedback actuator 5, an absolute angle sensor unit 7 for determining the absolute steering angle of the steering shaft 2, and a relative angle sensor unit 4 for determining the relative steering angle of the steering shaft 2. The second subsystem 102 includes a steering actuator unit 9, a coupling element 12, an absolute position sensor unit 15 for determining the absolute position of the coupling element 12, and a relative position sensor unit 16 for determining the relative position of the coupling element 12. The third subsystem 103 includes an interface 19 to a backup steering system 200, wherein the interface 19 is designed to transmit data to the backup steering system 200.

[0039] The backup steering system 200 includes a braking system 201, a driving system 202, and an active chassis system 203, wherein the backup steering system 200 enables the motor vehicle to perform the intended steering action by intentionally activating components in the systems 201, 202, and 203 when a failure occurs in the second subsystem 202.

[0040] Figure 2 The steering system shown can also be regarded as an integrated steering system 1 ′, wherein the integrated steering system 1 ′ includes the steer-by-wire system 1 and the backup steering system 200 , and thus includes a first subsystem 101 , a second subsystem 102 and a third subsystem 103 .

[0041] exist Figure 2In the illustrated embodiment, first subsystem 101, second subsystem 102, and third subsystem 103 are interconnected via a communication connection 20 for data exchange. This communication connection 20 can, in particular, be designed to be redundant. In this embodiment, communication connection 20 is designed to connect first subsystem 101 and second subsystem 102 via a dedicated communication channel 21. Furthermore, first subsystem 101, second subsystem 102, and third subsystem 103 are connected via a vehicle communication network 22. Therefore, communication connection 20 is provided at a level above layer 1 in the ISO / OSI model.

[0042] For proper operation, the steer-by-wire system 1 requires absolute values—values ​​relative to a fixed reference system. For example, the neutral position of the steering handle is defined as a steering angle of 0° at the steering shaft 2. In the absence of an absolute angle sensor unit 7, the feedback actuator 5 is designed to perform relative measurements, for example, by utilizing the servo motor's rotor position sensor as the relative angle sensor unit 4. However, to be able to use these relative values, an absolute angle sensor unit is still required for initial comparison. Once the offset between the absolute and relative angles is determined, the actuator can determine the change in the signal quantity based solely on the motor's movement. This means that after the initialization phase, the feedback actuator can determine the absolute angle even without an absolute angle sensor unit.

[0043] Therefore, since the absolute angle sensor unit 7 is only required during the initialization phase, particularly when starting the motor vehicle, in this embodiment, the absolute angle sensor unit 7 is decoupled from the first subsystem 101, particularly the feedback actuator 5, and is directly connected to the second subsystem 102, particularly the steering actuator unit 9 of the second subsystem 102, via the first communication interface 34. During the initialization phase, the second subsystem 102, particularly the steering actuator unit 9, transmits absolute measured values ​​for the initial comparison of the absolute angle with the relative angle to the first subsystem 101, particularly the feedback actuator 5, via the dedicated communication channel 21. If the feedback actuator 5 (which primarily provides the signal via the rotor position sensor as the relative angle sensor unit 4) fails, the steering actuator unit 9 continues to receive the required input signal directly from the absolute value generator, namely the absolute angle sensor unit 7.

[0044] This principle also applies to determining the position of the coupling element 12. Steering actuator units 9 that are not equipped with an absolute position sensor unit 15 are designed to perform relative measurements, for example, using the rotor position sensor of the servo motor as the relative position sensor unit 16. Here, too, an initial comparison with the absolute position sensor unit 15 is required to enable the use of the value from the relative position sensor unit 16. Once the offset between the absolute and relative positions of the coupling element 12 has been determined, the steering actuator unit can determine the change in position based solely on the movement of the motor. Therefore, after the initialization phase is complete, the steering actuator unit 9 is designed to determine the absolute position even without the absolute position sensor unit 15.

[0045] Therefore, since the absolute position sensor unit 15 is only required during the initialization phase, particularly when starting the motor vehicle, in this embodiment, the absolute position sensor unit 15 is decoupled from the second subsystem 102, particularly the steering actuator unit 9, and directly connected to the first subsystem 101, particularly the feedback actuator 5 of the first subsystem 101, via a second direct communication interface 35. During the initialization phase, the first subsystem 101, particularly the feedback actuator 5, transmits absolute measured values ​​for the initial comparison of absolute and relative positions to the second subsystem 102, particularly the steering actuator unit 9, via a dedicated communication channel 21. If the steering actuator unit 9 (which also provides the primary signal via the rotor position sensor, acting as the relative position sensor unit 16) fails, the first subsystem 101 continues to receive the required input signals directly from the absolute value generator, namely the absolute position sensor unit 15. Subsequently, to steer the motor vehicle, the required signals are preferably transmitted via the vehicle communication network 22 to the third subsystem 103 and, thereby, to the backup steering system 200.

[0046] When the wire-controlled steering system 1 operates normally and without faults, it is set as follows: the steering actuator unit 9 of the second subsystem 102 reads the absolute measurement value related to the steering shaft angle set by the steering handle from the absolute angle sensor unit 7, converts it into accurate angle information, and provides the result through the dedicated communication channel 21 and the vehicle communication network 22.

[0047] At the same time, the first subsystem 101 , in particular the feedback actuator 5 , reads the absolute measurement value related to the absolute position of the coupling element 12 from the absolute position sensor unit 15 , converts it into appropriate position information, and provides the result via the dedicated communication channel 21 and the vehicle communication network 22 .

[0048] The second subsystem 102, in particular the steering actuator unit 9, reads this absolute position information from the dedicated communication channel 21 and / or the vehicle communication network 22 and compares it with the relative position measurement performed by the second subsystem 102 based on the measurement values ​​of the rotor position sensor 16, thereby obtaining high-quality data about the absolute position of the coupling element, in particular data about the set wheel steering angle of the steerable wheel 14, thanks to the high resolution of the rotor position measurement.

[0049] The first subsystem 101, specifically the feedback actuator 5, reads the absolute angle information regarding the set steering angle of the steering shaft 2 via the dedicated communication channel 21 and / or the vehicle communication network 22, and compares this information with the relative angle value measured by the rotor position sensor (i.e., the relative angle sensor unit 4) configured by the first subsystem 101 for the motor 6 of the feedback actuator 5. In this way, the first subsystem is able to determine the absolute angle information regarding the set steering angle of the steering shaft 2 with higher quality, thanks to the high resolution of the rotor position measurement.

[0050] In this way, the first subsystem 101 and the second subsystem 102, in particular the feedback actuator 5 and the steering actuator unit 9, respectively obtain accurate absolute information about the angle of the steering shaft 2 or the position of the coupling element 12. As a result, the steering command can be set via the steering handle 3.

[0051] If a failure occurs in first subsystem 101, it will no longer be able to provide absolute steering wheel angle information. However, the second subsystem, particularly steering actuator unit 9, can continue to operate because the information required for its operation continues to be provided. The rotor position sensor, used as relative position sensor unit 16, provides absolute position information about the position of coupling element 12. The required comparison between absolute and relative position measurements is already completed during the startup phase of trouble-free operation. Furthermore, absolute angle information about steering shaft 2 is provided directly by absolute angle sensor unit 7. Therefore, the steering angle of steered wheel 14 can continue to be set according to the set specifications by steering actuator unit 9.

[0052] If the second subsystem 102 fails, and therefore the steering actuator unit 9 also fails, the steering specification can no longer be implemented by setting the wheel steering angles of the steerable wheels 14 using the steering actuator unit 9. The steering specification is then implemented by the backup steering system 200, in particular by steer- ing the motor vehicle by intentionally braking individual wheels and / or applying intentional drive torque to individual wheels and / or intentionally controlling active chassis components assigned to the wheels. To this end, the backup steering system 200 requires information about the position of the coupling element 12 and the angle of the steering shaft 2 to determine information about the steering handle 3. This information is provided by the first subsystem 101 to the third subsystem 103 via the vehicle communication network 22, where it is provided to the backup steering system 200, in particular, via the interface 19. The absolute angle of the steering shaft 2 can be provided to the first subsystem 101 based on the measurement results of the relative angle sensor unit 4, with the absolute and relative values ​​already being compared during the startup process for trouble-free operation. The first subsystem 101 continues to obtain measurement values ​​about the absolute position of the coupling element 12 through the absolute position sensor unit 15, and the first subsystem 101 converts the obtained measurement values ​​into absolute position information about the position of the coupling element 12, and also provides it as sensor data to the backup steering system 200 through the vehicle communication network 22 for use.

[0053] Another embodiment of the method for operating a steer-by-wire system according to the present invention can be particularly described as follows: Figure 2 The wire-controlled steer system shown in the figure will be combined with Figure 3 Provide explanation. Figure 3 A simplified block diagram is shown for this purpose.

[0054] The method provides that, in a first operating mode BM1 configured for trouble-free operation, the second subsystem 102 receives (A) angle measurement values ​​provided by the absolute angle sensor unit 7 via the first communication interface 34, converts (B) the received angle measurement values ​​into corresponding angle information 31, and provides (C) the angle information 31 to the first subsystem 101 via the communication connection 20. The first subsystem 101 receives (D) the angle information 31 provided via the communication connection 20 and determines (E) the absolute steering axis angle based on the angle information 31 and the relative angle of the steering axis 2 determined by the relative angle sensor unit 4. Furthermore, the first subsystem 101 receives (F) position measurement values ​​provided by the absolute position sensor unit 15 via the second communication interface 35, converts (G) the received position measurement values ​​into corresponding position information 32 regarding the position of the coupling element 12, and provides (H) the position information 32 to the second subsystem 102 via the communication connection 20. The second subsystem 102 acquires (K) the position information 32 provided via the communication connection 20 and determines (L) the absolute position of the coupling element based on the position information 32 and the relative position of the coupling element 12 acquired by the relative position sensor unit 16 .

[0055] If an error is detected in first subsystem 101, specifically if first subsystem 101 is unable to provide position information 32, the steer-by-wire system switches (M) to the second operating mode BM2. Second subsystem 102 determines (P) the absolute position of the coupling element based on the relative position of coupling element 12 determined by relative position sensor unit 16 and the previously determined absolute position of the coupling element. Furthermore, second subsystem 102 receives information about the absolute angle of steering shaft 2 directly from absolute angle sensor unit 7 via communication connection 20. Using this information, steering actuator unit 9 of second subsystem 102 is further actuated (R) to set the steering angle of steered wheel 14.

[0056] If, on the other hand, an error is detected in the second subsystem 102, making it no longer possible to set the wheel steering angle via the steering actuator unit 9, the steer-by-wire system switches (N) to the third operating mode BM3. In this third operating mode BM3, the first subsystem 101 determines (S) the absolute angle of the steering shaft 2 based on the relative angle of the steering shaft 2 determined by the relative angle sensor unit 4 and the previously determined absolute angle of the steering shaft. Furthermore, as in the first operating mode BM1, the first subsystem 101 acquires (F') the position measurement values ​​provided by the absolute position sensor unit 15 and converts (G') these acquired position measurement values ​​into corresponding position information 32 regarding the position of the coupling element 12. The first subsystem 101 then provides (T) the determined absolute angle 33 of the steering shaft 2 and the converted position information 32 to the third subsystem 103. The interface 19 of the third subsystem 103 forwards (U) the determined absolute angle 33 and position information 32 to the backup steering system 200, which controls the steering of the motor vehicle (V) based on the received information 32, 33.

[0057] The embodiments shown in the drawings and described in conjunction with the description serve to illustrate the invention and have no limiting effect.

[0058] Reference Signs List

[0059] 1. Steer-by-wire system

[0060] 1' integral steering system

[0061] 2 Steering axles

[0062] 3 Steering handle

[0063] 4 Relative angle sensor unit

[0064] 5 Feedback actuator

[0065] 6 Feedback actuator (5) motor

[0066] 7 Absolute angle sensor unit

[0067] 8 Steering gear

[0068] 9 Steering actuator unit

[0069] 10 Motor of steering actuator unit (9)

[0070] 11 Steering pinion

[0071] 12 Coupling elements

[0072] 13 tie rod

[0073] 14 steerable wheels

[0074] 15 Absolute position sensor unit

[0075] 16 Relative position sensor unit

[0076] 18 Direct Communication Channel

[0077] 19 Interface

[0078] 20 Communication Connections

[0079] 21 Dedicated communication channels

[0080] 22 Vehicle Communication Network

[0081] 31 Angle information

[0082] 32 Location Information

[0083] 33 The absolute angle determined

[0084] 34 First direct communication interface

[0085] 35 Second direct communication interface

[0086] 101 First Subsystem

[0087] 102 Second Subsystem

[0088] 103 Third Subsystem

[0089] 103' Third subsystem (with backup steering system 200)

[0090] 200 Backup Steering System

[0091] 201 Braking System

[0092] 202 drive system

[0093] 203 Active Chassis

[0094] BM1 / 2 / 3 first / second / third operation mode

[0095] A to V method steps

Claims

1. A steer-by-wire system (1) for a motor vehicle, comprising a first subsystem (101) and a second subsystem (102), wherein the first subsystem (101) comprises a steering shaft (2), a steering handle (3) arranged at one end of the steering shaft in a rotationally fixed manner, a feedback actuator (5), an absolute angle sensor unit (7) for determining an absolute steering angle of the steering shaft (2), and a relative angle sensor unit (4) for determining a relative steering angle of the steering shaft (2), and the second subsystem (102) comprises a steering actuator unit (9), a coupling element (12), an absolute position sensor unit (15) for determining an absolute position of the coupling element (12), and a relative position sensor unit (16) for determining a relative position of the coupling element (12), characterized in that The first subsystem (101) and the second subsystem (102) are connected to each other via a communication connection (20), wherein the communication connection (20) is configured to transmit sensor data (32) from the first subsystem (101) to the second subsystem (102), and to transmit sensor data (31) from the second subsystem (102) to the first subsystem (101).

2. The steer-by-wire system (1) according to claim 1, characterized in that A third subsystem (103) is provided, wherein the third subsystem (103) includes an interface (19) for a backup steering system (200), and the communication connection (20) is further configured to transmit sensor data (31, 32, 33) from the first subsystem (101) and / or the second subsystem (102) to the third subsystem (103), and the interface (19) is configured to transmit the sensor data (31, 32) transmitted to the third subsystem (103) to the backup steering system (200).

3. The steer-by-wire system (1) according to claim 1 or 2, characterized in that The communication connection (20) is realized via the vehicle communication network (22) and / or via a dedicated communication channel (21) between the subsystems (101, 102, 103).

4. A steer-by-wire system (1) according to any one of the preceding claims, characterised in that The second subsystem (102) is designed to receive angle measurement values ​​provided by the absolute angle sensor unit (7) via the first direct communication interface (34).

5. A steer-by-wire system (1) according to any one of the preceding claims, characterised in that The second subsystem (102) is designed to provide the absolute angle sensor unit (7) with energy required for operation, in particular via the first direct communication interface (34).

6. A steer-by-wire system (1) according to any one of the preceding claims, characterised in that The first subsystem (101) is designed to receive position measurement values ​​provided by the absolute position sensor unit (15) via a second direct communication interface (35).

7. A steer-by-wire system (1) according to any one of the preceding claims, characterised in that The first subsystem (101) is designed to provide the absolute position sensor unit (15) with energy required for operation, in particular via the second direct communication interface (35).

8. A steer-by-wire system (1) according to any one of the preceding claims, characterised in that A steer-by-wire system (1) is designed to operate in different operating modes (BM1, BM2, BM3) in a motor vehicle, wherein the steer-by-wire system (1) is configured to operate without failure in a first operating mode (BM1), is configured to operate in the event of a failure in a first subsystem (101) in a second operating mode (BM2), and is designed to operate in the event of a failure in a second subsystem (102) in a third operating mode (BM3).

9. Steer-by-wire system (1) according to any one of the preceding claims, characterized in that The steer-by-wire system (1) is designed to operate according to the method of any of the following claims.

10. Steer-by-wire system (1) according to any one of the preceding claims, characterized in that The communication connection (20) is designed to be redundant.

11. A method for operating a steer-by-wire system (1) according to any one of claims 1 to 10 in a motor vehicle, characterized in that In a first operating mode (BM1) configured for trouble-free operation, the second subsystem (102) acquires an angle measurement value provided by the absolute angle sensor unit (7), the second subsystem (102) converts the acquired angle measurement value into corresponding angle information (31), and the second subsystem (102) provides the angle information (31) to the first subsystem (101) via a communication connection (20).

12. The method according to claim 11, characterized in that The first subsystem (101) obtains angle information (31) provided via the communication connection (20) and determines an absolute steering shaft angle based on the angle information (31) and the relative angle of the steering shaft (2) obtained by the relative angle sensor unit (4).

13. The method according to claim 11 or 12, characterized in that In a first operating mode (BM1) configured for trouble-free operation, the first subsystem (101) acquires position measurement values ​​provided by the absolute position sensor unit (15), converts the acquired position measurement values ​​into corresponding position information (32) about the position of the coupling element (12), and provides the position information (32) to the second subsystem (102) via a communication connection (20).

14. The method according to claim 13, characterized in that The second subsystem (102) obtains position information (32) provided via the communication connection (20) and determines the absolute position of the coupling element based on the position information (32) and the relative position of the coupling element (12) obtained by the relative position sensor unit (16).

15. The method according to claim 13 or 14, characterized in that In a third operating mode (BM3), due to an error in the second subsystem (102), the motor vehicle is steered by means of a backup steering system (200), the first subsystem (101) determines the absolute angle (33) of the steering shaft (2) based on the relative angle of the steering shaft (2) obtained by the relative angle sensor unit (4) and the previously determined absolute steering shaft angle, the determined absolute angle (33) of the steering shaft (2) being provided together with the converted position data (32) to the third subsystem (103), wherein the interface (19) of the third subsystem (103) forwards the determined absolute angle (33) and the position information (32) to the backup steering system (200).

16. The method according to any one of claims 11 to 15, characterized in that In a second operating mode (BM2), when the first subsystem (101) is unable to provide position information (32) due to an error in the first subsystem (101), the second subsystem (102) determines the absolute coupling element position based on the relative position of the coupling element obtained by the relative position sensor unit (16) and the previously determined absolute position of the coupling element, wherein the information about the absolute angle of the steering shaft (2) is directly obtained by the absolute angle sensor unit (7).

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