Steer-by-wire steering system including networked subsystems and method for operating such a steer-by-wire steering system

Abstract

The present invention relates to a steer-by-wire steering 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) rotationally fixed to an 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 adjuster unit (9), a connecting element (12), an absolute position sensor unit (15) for determining an absolute position of the connecting element (12), and a relative position sensor unit (16) for determining a relative position of the connecting element (12). To increase robustness against failures, the first subsystem (101) and the second subsystem (102) are connected to each other via a communication connection (20), which is designed to transmit sensor data (32) from the first subsystem (101) to the second subsystem (102) and sensor data (31) from the second subsystem (102) to the first subsystem (101). The present invention further relates to a method for operating such a steer-by-wire steering system.

Description

[Technical Field]

[0001] The present invention relates to a steer-by-wire steering system for a motor vehicle having a first subsystem and a second subsystem, the first subsystem including a steering shaft, a steering handle arranged rotationally fixed 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, and the second subsystem including a steering actuator unit, a connecting element, in particular a rack, an absolute position sensor unit for determining an absolute position of the connecting element, and a relative position sensor unit for determining a relative position of the connecting element. Furthermore, the present invention relates to a method for operating such a steer-by-wire steering system. [Background technology]

[0002] Steer-by-wire steering systems have been widely described in the prior art. For example, German Patent Application Publication No. 102018114988 discloses a steer-by-wire steering system having a steering wheel, a feedback actuator, and a steering actuator, in which steering commands can be issued via the steering wheel and converted by the steering actuator into steering movements of the steerable wheels of the motor vehicle. One challenge in steer-by-wire steering systems is to keep the motor vehicle controllable even if a fault occurs in the steer-by-wire steering system. German Patent Application Publication No. 102020100719 proposes, for this purpose, that in a motor vehicle having a front-axle steering system and a rear-axle steering system, in the event of an error in the front-axle steering system or the rear-axle steering system, the failed steering system be switched off to enable steering operation in an automatic driving mode or by a derived setpoint movement. Furthermore, it is known from German Patent Application Publication No. 102019217588 that, after a vehicle collision, one or more wheels of a vehicle axle are no longer fully steerable or are no longer steerable, so that steering is performed by the functional steering axle and a braking signal is sent to one of the vehicle wheels connected to this steering axle. It is also known to design components of a steer-by-wire steering system redundantly, so that in the event of a component failure, the corresponding function of this component is performed by a redundant component. For example, German Patent Application Publication No. 102020209270 discloses a redundantly designed control unit that can be used in a steer-by-wire steering system. A redundant design of components of a steer-by-wire steering system is also disclosed in U.S. Patent Application Publication No. 2022 / 0001916.

[0003] Furthermore, German Patent Application Publication No. 102004008203 discloses a system and method for initial wheel alignment of a steer-by-wire steering system for a motor vehicle. The steer-by-wire steering system in this case includes a first subsystem having a steering shaft, a steering handle disposed on the steering shaft, a steering wheel actuator with an associated motor output stage, an absolute angle sensor unit for determining an absolute steering angle of the steering shaft, a relative sensor unit for determining a relative steering angle of the steering shaft, and a steering wheel controller. The steer-by-wire steering system further includes a second subsystem having steerable wheels that can be steered by wheel actuators associated with each steerable wheel, the wheel actuators being controlled by the wheel controller via their respective motor 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.

[0004] A similar steer-by-wire steering system is described in DE 102004030685 A1. The steer-by-wire steering system is here configured to allow model-based error recognition, and analytical redundancy is used instead of additional hardware components, thus reducing costs and increasing reliability.

[0005] This creates a further need to keep motor vehicles with steer-by-wire steering systems controllable in the event of an error in the steering system or in the steering system, thus further reducing the risk of personal injury. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102018114988 [Patent Document 2] German Patent Application Publication No. 102020100719 [Patent Document 3] German Patent Application Publication No. 102019217588 [Patent Document 4] German Patent Application Publication No. 102020209270 [Patent Document 5] US Patent Application Publication No. 2022 / 0001916 [Patent Document 6] German Patent Application Publication No. 102004008203 [Patent Document 7] German Patent Application Publication No. 102004030685 Summary of the Invention [Problem to be solved by the invention]

[0007] Against this background, the object of the present invention is to further improve steer-by-wire steering systems and methods for operating steer-by-wire steering systems, and in particular to find a cost-effective method for eliminating possible errors in measuring basic parameters in steer-by-wire systems. [Means for solving the problem]

[0008] To this end, a steer-by-wire steering system is proposed as set forth in claim 1, and a method for operating a steer-by-wire steering system as set forth in another independent claim. Further advantageous embodiments of the invention are set forth in the dependent claims and in the description and shown in the figures.

[0009] The proposed solution provides a steer-by-wire steering system for a motor vehicle having a first subsystem and a second subsystem. The first subsystem includes a steering shaft, a steering handle, in particular a steering wheel, arranged rotationally fixed 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 is provided as the relative angle sensor unit. The second subsystem includes a steering actuator unit, a connecting element, in particular a rack, an absolute position sensor unit for determining the absolute position of the connecting element, and a relative position sensor unit for determining the relative position of the connecting element. In particular, a rotor position sensor unit associated with the electric motor of the steering actuator unit is provided as the relative position sensor unit. According to the present invention, in a steer-by-wire steering system, a first subsystem and a second subsystem are connected to each other via a communication connection, the communication connection being configured to transmit sensor data from the first subsystem to the second subsystem and from the second subsystem to the first subsystem. The exchange of sensor data between the subsystems is advantageously improved by this design, and advantageously, in particular in the event of a failure of one of the subsystems, the sensor data can be provided in an improved manner to the subsystem that is still functioning. In particular, the communication connection is designed to be redundant.

[0010] According to a particularly advantageous refinement, the steer-by-wire steering system includes a third subsystem, the third subsystem including an interface with a backup steering system, and the communication connection is advantageously further configured to transmit sensor data from the first subsystem and / or from the second subsystem to the third subsystem. The interface is advantageously configured here to transmit the sensor data transmitted to the third subsystem to the backup steering system. The backup steering system is advantageously formed by one or preferably several vehicle assemblies used to deviate from their original task of implementing the steering specification. In particular, a correspondingly activated braking system and / or a correspondingly activated drive system and / or a correspondingly activated active chassis may be included in the backup steering system. In the event of a failure of the steer-by-wire steering system, the motorized vehicle needs to be steered by the backup steering system, and sensor data related to the steering of the motorized vehicle can here advantageously be transmitted via the communication connection to the third subsystem, and thus to the backup steering system, thereby improving the functionality of the backup steering system. In particular, an overall steering system is provided that includes a steer-by-wire steering system and a backup steering system, in which design a third subsystem is included in the overall steering system, in particular the backup steering system, which overall steering system can here in particular be designed as a steer-by-wire steering system according to the invention with a supplemented backup steering system.

[0011] One embodiment variant provides in particular that a control unit, in particular an ECU (Electronic Control Unit), is associated with each of the subsystems. Each subsystem may here comprise a control unit. However, an advantageous embodiment provides a central control unit, the control subunits of which are each assigned to a subsystem as a control unit.

[0012] An advantageous embodiment of the steer-by-wire steering system provides that the communication connection is implemented by a vehicle communication network, in particular a CAN (Controller Area Network) and / or by a private communication channel between the subsystems. In particular, a high-level communication connection is used as the communication connection. In particular, the communication connection is implemented at least at layer 2 level with respect to the ISO / OSI reference model. The communication connection is preferably implemented as a wired connection. However, according to an embodiment variant, a communication connection formed completely or partly wirelessly, in particular a wireless connection, is also provided.

[0013] Further advantageously, the second subsystem of the steer-by-wire steering system, in particular the steering actuator unit of the second subsystem, is designed to receive angle measurements provided by the absolute angle sensor unit included in the first subsystem, in particular via a first direct communication interface to the absolute angle sensor unit. The angle measurements captured by the absolute angle sensor unit are then advantageously transmitted directly to the second subsystem, in particular to the steering actuator unit, in particular to a control unit associated with the steering actuator unit. In particular, the absolute angle sensor unit is here directly wired to the second subsystem. Thus, the second subsystem is advantageously designed to directly receive steering information required to set the correct wheel steering angle. In particular, in a variant embodiment, it is provided that the first communication interface is not included in the communication connection but is formed separately.

[0014] The second subsystem, in particular the steering actuator unit, is advantageously further designed to provide the absolute angle sensor unit with the energy required for its operation, preferably via a direct connection, in particular via the first direct communication interface. Advantageously, the voltage required for the operation of the absolute angle sensor unit is provided in a manner controlled by the second subsystem. Advantageously, the absolute angle sensor unit does not depend on the energy supply from the first subsystem.

[0015] According to another advantageous embodiment of the steer-by-wire steering system, the first subsystem is designed to receive position measurements provided by the absolute position sensor unit, particularly via a second direct communication interface to the absolute position sensor unit. In particular, the absolute position of the second subsystem's connecting element, and thus ultimately the set wheel steering angle of the motor vehicle's steered wheels, is derived from these position measurements. The position measurements captured by the absolute position sensor unit are advantageously transmitted directly to the first subsystem, particularly to a feedback actuator, and more particularly to a control unit assigned to the first subsystem. In particular, the absolute position sensor unit is directly wired to the second subsystem. Thus, the first subsystem is advantageously designed to receive information regarding the direct position measurements for a specific position of the connecting element, and thus specifically the set wheel steering angle. In particular, a design variant is provided in which the second communication interface is not included in the communication connection but is rather 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 preferably designed to supply the absolute position sensor unit with the energy required for its operation, preferably via a direct connection, in particular via the second direct communication interface. In particular, the voltage required for the operation of the absolute position sensor unit is provided here in a manner controlled by the first subsystem. The absolute position sensor unit is preferably not dependent on the energy supply by the second subsystem.

[0017] A further advantageous embodiment provides that the steer-by-wire steering system is designed for operation in a motor vehicle in different operating modes, in particular, the steer-by-wire steering system is configured in a first operating mode for error-free operation of the steer-by-wire system, this first operating mode being herein a normal operating mode in which the steer-by-wire steering system is operated normally.

[0018] More particularly, the steer-by-wire steering system is configured with a second mode of operation for operation in the event of a failure, particularly a complete failure, of the first subsystem, which advantageously provides that the steer-by-wire steering system continues to steer the motor vehicle using the second subsystem even if the first subsystem fails.

[0019] Furthermore, in particular, the steer-by-wire steering system is designed in a third operating mode for operation in the event of a failure, in particular a complete failure, of the second subsystem, in particular the steering actuator unit of the second subsystem. This third operating mode advantageously provides for the steer-by-wire steering system to steer the motor vehicle using a backup steering system in the event of a failure of the second subsystem, in particular the steering actuator unit. Advantageously, sensor data captured by sensors of the first and second subsystems, in particular information regarding the absolute angle of the steering shaft and information regarding the absolute position of the connecting element, is provided to the backup steering system by the first subsystem.

[0020] A further proposed method for operating a steer-by-wire steering system in a motor vehicle, in particular a steer-by-wire steering system in a motor vehicle designed as claimed in any one of claims 1 to 9, provides that in a first operating mode configured for error-free operation, a second subsystem captures angle measurements provided by the absolute angle sensor unit, converts the captured angle measurements into corresponding angle information, and provides the angle information to the first subsystem via a communication connection. In addition, the angle information is advantageously also provided to a third subsystem. The angle information here is particularly sensor data within the meaning of the present invention. The first subsystem of the steer-by-wire steering system in particular in this case includes a steering shaft, a steering wheel arranged rotationally fixed 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 includes, among other things, a steering actuator unit, a coupling element, 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. The third subsystem includes, among other things, an interface to a backup steering system, which is implemented, among other things, by actuation of active vehicle components, in particular actuation of brakes assigned to the wheels of the motor vehicle, actuation of the drive unit, and / or actuation of active chassis components. In that the second subsystem captures angle measurements provided by the absolute angle sensor unit, these angle measurements are advantageously available to the second subsystem even in the event of at least a partial failure of the first subsystem. During normal operation without error, the first subsystem advantageously processes angle information transmitted to the first subsystem via the communication connection.

[0021] In particular, the first subsystem is to capture angle information provided via the communication connection and determine the absolute steering shaft angle from this angle information and the relative angle of the steering shaft captured by the relative angle sensor unit. This determination of the absolute steering shaft angle is advantageously performed upon (re)startup in order to initially determine the absolute steering shaft angle. For further operation, it is provided that the determination of the absolute steering shaft angle is also at least alternatively confirmed, in particular taking into account the initially determined absolute steering shaft angle and the captured relative angle of the steering shaft.

[0022] According to a further advantageous embodiment, in a first operating mode configured for error-free operation, the first subsystem captures position measurements provided by the absolute position sensor unit, advantageously converts the captured position measurements into corresponding position information regarding the position of the coupling element, and advantageously provides the position information to the second subsystem via the communication connection. In addition, the position information is advantageously also provided to the third subsystem. The position information is particularly sensor data in the sense of the present invention. Thus, the position measurements are advantageously available to the first subsystem even in the event of at least a partial failure of the second steering system, and can be made available as position information to the third subsystem, and thus to a backup steering system of the motor vehicle, in particular, thereby advantageously enabling improved steering of the motor vehicle using the backup steering system in the event of a failure of the second steering system.

[0023] In particular, it is provided that the second subsystem, in particular the steering actuator unit of the second subsystem, more particularly an evaluation unit assigned to the steering actuator unit, captures position information provided via the communication connection and advantageously determines an absolute position of the coupling element from this position information and the relative position of the coupling element captured by the relative position sensor unit. This determination of the absolute coupling element position is advantageously performed upon (re)startup of the steer-by-wire steering system in order to initially determine the absolute coupling element position. It is particularly provided that for further operation, the determination of the absolute coupling element position is at least alternatively confirmed taking into account the initially determined absolute coupling element position and the captured relative position of the coupling element.

[0024] According to an advantageous refinement of the method, in a third operating mode in which the motor vehicle is steered by the backup steering system due to an error in the second subsystem, the first subsystem determines an absolute steering shaft angle based on the relative steering shaft angle captured by the relative angle sensor unit and the previously determined absolute steering shaft angle. This determined absolute steering shaft angle is advantageously provided to the third subsystem together with the converted position information, and the interface of the third subsystem advantageously transfers the determined absolute angle and position information to the backup steering system. The absolute steering shaft angle is determined here, particularly during error-free operation. The information transmitted to the third subsystem, particularly the absolute steering shaft angle and position information, is particularly sensor data within the meaning of the present invention. Using the sensor data thus transmitted, the backup steering system is advantageously configured in an improved manner to steer the motor vehicle according to the steering specifications.

[0025] Another advantageous embodiment of the method provides that in a second operating mode in which the first subsystem is unable to provide position information due to an error within the first subsystem, the second subsystem determines an absolute linking element position based on the relative linking element positions captured by the relative position sensor unit and the previously determined absolute linking element position, and information regarding the absolute angle of the steering shaft is captured directly by the absolute angle sensor unit. Here, the absolute linking element position was determined during error-free operation, particularly. Thus, advantageously, the motor vehicle can remain steerable by the second subsystem even if a serious error occurs in the first subsystem.

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

[0027] Further advantageous details, features and design details of the present invention are described in more detail in conjunction with the exemplary embodiments shown in the drawings. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a simplified perspective view of an exemplary embodiment of a steer-by-wire steering system designed in accordance with the present invention. [Figure 2] FIG. 2 is a simplified schematic diagram of a further exemplary embodiment of a steer-by-wire steering system designed in accordance with the present invention. [Figure 3] FIG. 1 is a block diagram of an exemplary embodiment of a method designed in accordance with the present invention for operating a steer-by-wire steering system. DETAILED DESCRIPTION OF THE INVENTION

[0029] In the different figures, identical parts are generally provided with the same reference numerals and may therefore each be described only in conjunction with one of the figures.

[0030] FIG. 1 shows an exemplary embodiment of a steer-by-wire steering system 1 designed in accordance with the present invention for a motor vehicle having a first subsystem 101 and a second subsystem 102. The first subsystem 101 of the steer-by-wire steering system 1 includes a steering column having a steering shaft 2 and a feedback actuator 5. A steering handle 3, designed as a steering wheel, is arranged rotationally fixed 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 steering resistance torque, to the steering shaft 2, specifically to transmit a steering feel. This steering resistance torque is perceptible as steering resistance by a vehicle user of the motor vehicle via the steering handle 3.

[0031] The steering wheel 3 of the steer-by-wire steering system 1 can be rotated in a known manner to introduce a steering command to the steering shaft 2, which is captured by a sensor. For this purpose, the first subsystem 101 in this exemplary embodiment includes an absolute angle sensor unit 7 assigned to the steering shaft 2 and designed to capture the angle set by the steering wheel 3 as an absolute steering angle of the steering shaft 2. Furthermore, the electric motor 6 of the feedback actuator 5 of the first subsystem 101 is assigned a relative angle sensor unit 4, which in this exemplary embodiment is a rotor position sensor. The relative steering angle of the steering shaft 2 can be captured by the rotor position sensor.

[0032] The second subsystem 102 of the steer-by-wire steering system 1 includes a steering actuator unit 9. In this exemplary 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 converts steering commands into steering movements of the steerable wheels 14 by corresponding actuation of the steering actuator unit 9. The steering actuator unit 9 acts by the electric motor 10 via the steering pinion 11 on a connecting element 12, here designed as a rack, thus triggering steering movements of the steerable wheels 14 of the motor vehicle, which are connected to the connecting element 12, in particular, via tie rods 13. The tie rods 13 themselves are each connected to the steered wheels 14 via a steering knuckle in a known manner. The second subsystem 102 further includes an absolute position sensor unit 15 for determining the absolute position of the connecting element 12 and a relative position sensor unit 16 for determining the relative position of the connecting element 12. In this embodiment, a rotor position sensor assigned to the electric motor 10 of the steering actuator unit 9 is used as the relative position sensor unit 16.

[0033] In this exemplary embodiment, the steering actuator unit 9 of the second subsystem 102 supplies the energy required for the operation of the absolute angle sensor unit 7 included in the first subsystem 101 and directly receives the angle measurements provided by the absolute angle sensor unit 7. For this purpose, the steering actuator unit 9 is connected to the absolute angle sensor unit 7 via a first direct communication interface 34 included in the communication channel 18. SENT or SPC is advantageously used as a communication protocol for transmitting the angle measurements. The angle measurements are then converted by the second subsystem 102 or by a control unit assigned to the second subsystem 102 into corresponding angle information and transmitted to the first subsystem 101 via the high-level communication connection 20. The first subsystem 101, in particular the control unit assigned to the first subsystem 101, determines the received angle information 31 together with the measurements provided by the relative angle sensor unit 4 as the absolute steering shaft angle.

[0034] Similarly, in this exemplary embodiment, the first subsystem 101, and in particular the feedback actuator 5 of the first subsystem 101, provides the energy required for the operation of the absolute position sensor unit 15 and directly receives the position measurements provided by the absolute position sensor unit 15. For this purpose, the feedback actuator 5 is connected to the absolute angle sensor unit 7 via a second direct communication interface 35, which is also configured by a communication channel 18. SENT or SPC is advantageously used as the communication protocol for transmitting the position measurements. The position measurements are then converted by the first subsystem 101, or by 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.

[0035] Therefore, the communication connection unit 20 connects the first subsystem 101 and the second subsystem 102 to each other, and in particular, the position information 32 determined by the first subsystem 101 is transmitted to the second subsystem 102 via the communication connection unit 20, and the angle information 31 determined by the second subsystem 102 is transmitted to the first subsystem 101.

[0036] 2 shows a further exemplary embodiment of a steer-by-wire steering system 1 designed in accordance with the present invention. The steer-by-wire steering 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 wheel 3 arranged rotationally fixed 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 connecting element 12, an absolute position sensor unit 15 for determining the absolute position of the connecting element 12, and a relative position sensor unit 16 for determining the relative position of the connecting element 12. The third subsystem 103 includes an interface 19 with a backup steering system 200, which is designed to transmit data to the backup steering system 200.

[0037] The backup steering system 200 includes a braking system 201, a drive system 202, and an active chassis system 203, and the backup steering system 200 uses intentional actuation of the components of the systems 201, 202, and 203 to cause the motor vehicle to perform an intentional steering action in the event that the second subsystem 202 fails.

[0038] The steering system shown in FIG. 2 can also be viewed as the steering system 1′ as a whole, which includes the steer-by-wire steering system 1 and the backup steering system 200, and therefore includes a first subsystem 101, a second subsystem 102, and a third subsystem 103.

[0039] 2, the first subsystem 101, the second subsystem 102, and the third subsystem 103 are connected to one another for data exchange via a communication connection 20, which can be configured in a particularly redundant manner. In this exemplary embodiment, this communication connection 20 is designed in such a way that the first subsystem 101 and the second subsystem 102 are connected to one another via a private communication channel 21, and that the first subsystem 101, the second subsystem 102, and the third subsystem 103 are connected to one another via a vehicle communication network 22. The communication connection 20 is arranged above the first layer with respect to the ISO / OSI model.

[0040] The steer-by-wire steering system 1 requires absolute values ​​for accurate operation, i.e., values ​​related to the neutral position of the steering wheel as a fixed reference frame, e.g., a steering angle of 0° on the steering shaft 2. The feedback actuator 5 without the absolute angle sensor unit 7 is designed to perform relative measurements, for example, by using its sensor for the rotor position of a servo motor as the relative angle sensor unit 4. However, to be able to use these values, an absolute angle sensor unit is required for the initial comparison. As soon as the existing offset between the absolutely determined angle and the relatively determined angle is determined, the actuator can determine the change in the signal variable based solely on the motor movement. This means that the feedback actuator can determine the absolute angle without the absolute angle sensor unit after an initialization phase.

[0041] Therefore, since the absolute angle sensor unit 7 is only required for initialization, particularly at the start of the motor vehicle, the absolute angle sensor unit 7 is in this exemplary embodiment separated from the first subsystem 101, and in particular from the feedback actuator 5, and connected directly to the second subsystem 102, and in particular to the steering actuator unit 9 of the second subsystem 102, via the first communication interface 34. During the initialization phase, the second subsystem 102, and in particular the steering actuator unit 9, transmits measured absolute values ​​for an initial comparison between the absolute angle and the relative angle to the first subsystem 101, and in particular to the feedback actuator 5, via the private communication channel 21. In the event that the feedback actuator 5, which provides the main signal via its rotor position sensor as the relative angle sensor unit 4, fails, the steering actuator unit 9 continues to provide the necessary input directly from the absolute value generator, and therefore from the absolute angle sensor unit 7.

[0042] This also applies to determining the position of the connecting element 12. A steering actuator unit 9 without an absolute position sensor unit 15 is designed to perform relative measurements by using, for example, a sensor for the rotor position of a servo motor as the relative position sensor unit 16. It also applies here that the absolute position sensor unit 15 is required for an initial comparison to make the value of the relative position sensor unit 16 available. Once the existing offset between the absolutely determined position of the connecting element 12 and the relatively determined position of the connecting element 12 is determined, the steering actuator unit can determine the change in position based solely on the motor movement. Therefore, the steering actuator unit 9 is designed to determine the absolute position without the absolute position sensor unit 15 after an initialization phase.

[0043] Therefore, since absolute position sensor unit 15 is only required for initialization, particularly at start-up of the motor vehicle, absolute position sensor unit 15 is, in this exemplary embodiment, isolated from second subsystem 102, particularly steering actuator unit 9, and directly connected to first subsystem 101, particularly feedback actuator 5 of first subsystem 101, via second direct communication interface 35. During the initialization phase, first subsystem 101, particularly feedback actuator 5, transmits measured absolute values ​​for an initial comparison of absolute position with relative position to second subsystem 101, particularly steering actuator unit 9, via private communication channel 21. In the event of failure of steering actuator unit 9, which also provides the primary signal via its rotor position sensor as relative position sensor unit 16, first subsystem 101 continues to provide the necessary input directly from the absolute value generator, and thus absolute position sensor unit 15. The signals required for steering the motor vehicle are then advantageously transmitted via vehicle communication network 22 to third subsystem 103 and thus to backup steering system 200.

[0044] To operate the steer-by-wire steering system 1 in the error-free case, the steering actuator unit 9 of the second subsystem 102 reads absolute measurements of the steering shaft angle set by the steering handle from the absolute angle sensor unit 7, converts them into correct angle information and provides the results via the private communication channel 21 and the vehicle communication network 22.

[0045] Meanwhile, the first subsystem 101, in particular the feedback actuator 5, reads absolute measurements regarding the absolute position of the linking element 12 from the absolute position sensor unit 15, converts them into appropriate position information and provides the results via the private communication channel 21 and the vehicle communication network 22.

[0046] The second subsystem 102, in particular the steering actuator unit 9, reads the absolute position information from the private communication channel 21 and / or the vehicle communication network 22 and compares the relative position measurements executed by the second subsystem 102 and based on the measurements of the rotor position sensor 16, thus obtaining position data regarding the absolute position of the connecting element, and therefore in particular data regarding the set wheel steering angle of the steerable wheel 14, with better quality due to the high resolution of the rotor position measurements.

[0047] The first subsystem 101, in particular the feedback actuator 5, reads the absolute angle information relative to the set steering angle of the steering shaft 2 via the private communication channel 21 and / or the vehicle communication network 22 and compares this information with relative angle measurements performed by the first subsystem 101 and based on measurements taken by a rotor position sensor assigned to the electric motor 6 of the feedback actuator 5 as a relative angle sensor unit 4. In this way, the first subsystem determines the absolute angle information relative to the set steering angle of the steering shaft 2 with better quality due to the higher resolution of the rotor position measurements.

[0048] In this way, the first subsystem 101 and the second subsystem 102, in particular the feedback actuator 5 and the steering actuator unit 9, obtain the correct absolute information about the angle of the steering shaft 2 or the position of the connecting element 12. The steering specifications can then be set by the steering wheel 3.

[0049] If the first subsystem 101 fails, it can no longer provide absolute steering wheel angle information, but the second subsystem, in particular the steering actuator unit 9, can continue to operate because it can continue to provide the information necessary for operation. Therefore, absolute position information regarding the position of the connecting element 12 is available via the rotor position sensor used as the relative position sensor unit 16, and the necessary comparison between the absolute and relative position measurements was already performed during start-up and error-free operation. Furthermore, information regarding the absolute angle of the steering shaft 2 is provided directly by the absolute angle sensor unit 7. Therefore, the wheel steering angle of the steered wheels 14 can continue to be set by the steering actuator unit 9 according to the specifications.

[0050] In the event of a failure of the second subsystem 102, and thus of the steering actuator unit 9, the wheel steering angles of the steerable wheels 14 can no longer be set via the steering actuator unit 9 to implement the steering specification. The steering specification is then implemented by the backup steering system 200, in particular by intentional braking of individual wheels and / or intentional application of drive torque to individual wheels and / or intentional activation of active chassis components assigned to the wheels. For this purpose, the backup steering system 200 requires information about both the position of the connecting element 12 as well as information about the steering shaft 2 and thus the angle of the steering handle 3. This information is provided by the first subsystem 101 to the third subsystem 103 via the vehicle communication network 22, which in turn provides this information to the backup steering system 200 via the interface 19. The absolute angle of the steering shaft 2 can be provided to the first subsystem 101 based on measurements performed by the relative angle sensor unit 4, and a comparison of the absolute and relative measurements has already been performed during startup in error-free operation. The first subsystem 101 continues to capture measurements for the absolute position of the connecting element 12 via the absolute position sensor unit 15, and the first subsystem 101 converts the captured measurements into absolute position information for the position of the connecting element 12, and similarly provides this position information as sensor data via the vehicle communication network 22 for use by the backup steering system 200.

[0051] A further exemplary embodiment of a method designed in accordance with the present invention for operating a steer-by-wire steering system, in particular a steer-by-wire steering system that may be designed as shown in Figure 2, will now be described with reference to Figure 3, which shows a simplified block diagram for this purpose.

[0052] The method includes, in a first operating mode BM1 configured for error-free operation, the second subsystem 102 (A) captures angle measurements provided by the absolute angle sensor unit 7 via the first communication interface 34, (B) converts the captured angle measurements into corresponding angle information 31, and (C) provides the angle information 31 to the first subsystem 101 via the communication connection 20. The first subsystem 101 (D) captures the angle information 31 provided via the communication connection 20 and (E) determines an absolute steering shaft angle from the angle information 31 and the relative angle of the steering shaft 2 captured by the relative angle sensor unit 4. Furthermore, the first subsystem 101 (F) captures position measurements provided by the absolute position sensor unit 15 via the second communication interface 35, (G) converts the captured position measurements into corresponding position information 32 with respect to the position of the connecting element 12, and (H) provides the position information 32 to the second subsystem 102 via the communication connection 20. The second subsystem 102 (K) captures the position information 32 provided via the communication connection 20 and (L) determines the absolute linked element position from this position information 32 and the relative position of the linked element 12 captured by the relative position sensor unit 16.

[0053] If an error is detected in the first subsystem 101, particularly such that the first subsystem 101 is unable to provide position information 32, the steer-by-wire steering system changes to the (M) second operating mode BM2. The second subsystem 102 determines the absolute linking element position based on the relative position of the linking element 12 captured by the (P) relative position sensor unit 16 and the predetermined absolute linking element position. Additionally, the second subsystem 102 captures information regarding the absolute angle of the steering shaft 2 directly from the absolute angle sensor unit 7 via the communication connection 20. This information is used to continue to operate the steering actuator unit 9 of the (R) second subsystem 102 to set the wheel steering angle of the steered wheels 14.

[0054] In contrast, if an error is detected in the second subsystem 102 and the wheel steering angle can no longer be set by the steering actuator unit 9, the steer-by-wire steering system changes to the third operating mode (N) BM3. In this third operating mode (BM3), the first subsystem 101 determines the absolute angle of the steering shaft 2 based on the relative angle of the steering shaft 2 captured by the relative angle sensor unit 4 and a predetermined absolute steering shaft angle. Furthermore, similar to the first operating mode (BM1), the first subsystem 101 captures the position measurements provided by the absolute position sensor unit 15 (F') and converts the captured position measurements into corresponding position information 32 regarding the position of the connecting element 12 (G'). The first subsystem 101 then provides the determined absolute angle 33 of the steering shaft 2 and the converted position information 32 to the third subsystem 103 (T). The interface 19 of the third subsystem 103 (U) forwards the determined absolute angle 33 and position information 32 to the backup steering system (200), which (V) steers the motor vehicle taking into account the received information 32, 33.

[0055] The exemplary embodiments shown in and described in the drawings serve to illustrate the invention and are therefore not limiting. [Explanation of symbols]

[0056] 1 Steer-by-wire steering system 1' Overall steering system 2 steering shaft 3 Steering handle 4 Relative angle sensor unit 5 Feedback Actuator 6. Electric motor of feedback actuator (5) 7 Absolute angle sensor unit 8 Steering Gear 9 Steering Actuator Unit 10 Electric motor of steering actuator unit (9) 11 Steering pinion 12 Connected Elements 13 Tie rod 14 steerable wheels 15 Absolute position sensor unit 16 Relative position sensor unit 18 Direct Communication Channels 19 Interface 20 Communication connection 21 Private Communication Channels 22 Vehicle Communication Network 31 Angle Information 32 Location information 33 Determined absolute angle 34 First Direct Communication Interface 35 Second Direct Communication Interface 101 First Subsystem 102 Second Subsystem 103 Third Subsystem 103' Third subsystem (having backup steering system (200)) 200 Backup Steering System 201 Braking System 202 Drive System 203 Active Chassis BM1 / 2 / 3 1st / 2nd / 3rd operation modes Method steps A to V

Claims

1. A steer-by-wire steering system (1) for a motor vehicle having a first subsystem (101) and a second subsystem (102), the first subsystem (101) including a steering shaft (2), a steering handle (3) rotationally fixedly arranged 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) including a steering actuator unit (9). ), a connecting element (12), an absolute position sensor unit (15) for determining an absolute position of the connecting element (12), and a relative position sensor unit (16) for determining a relative position of the connecting element (12), wherein the first subsystem (101) and the second subsystem (102) are connected to each other via a communication connection (20), the communication connection (20) being 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. 2. The steer-by-wire steering system (1) of claim 1, characterized by a third subsystem (103), the third subsystem (103) including an interface (19) with a backup steering system (200), the communication connection (20) being further configured to transmit sensor data (31, 32, 33) from the first subsystem (101) and / or from the second subsystem (102) to the third subsystem (103), and the interface (19) being configured to transmit the sensor data (31, 32) transmitted to the third subsystem (103) to the backup steering system (200).

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

4. 4. The steer-by-wire steering system (1) according to claim 1, wherein the second subsystem (102) is designed to receive angle measurements provided by the absolute angle sensor unit (7) via a first direct communication interface (34).

5. 5. The steer-by-wire steering system (1) according to claim 1, characterized in that the second subsystem (102) is designed to supply the absolute angle sensor unit (7) with the energy required for its operation, in particular via the first direct communication interface (34).

6. 6. The steer-by-wire steering system (1) according to claim 1, characterized in that the first subsystem (101) is designed to receive position measurements provided by the absolute position sensor unit (15) via a second direct communication interface (35).

7. 7. The steer-by-wire steering system (1) according to claim 1, characterized in that the first subsystem (101) is designed to supply the absolute position sensor unit (15) with the energy required for its operation, in particular via the second direct communication interface (35).

8. 8. The steer-by-wire steering system (1) according to any one of claims 1 to 7, characterized in that the steer-by-wire steering system (1) is designed to operate in a motor vehicle in different operating modes (BM1, BM2, BM3), the steer-by-wire steering system (1) being configured in a first operating mode (BM1) for error-free operation, the steer-by-wire steering system (1) being configured in a second operating mode (BM2) for operation in the event of a failure of the first subsystem (101), and the steer-by-wire steering system (1) being designed in a third operating mode (BM3) for operation in the event of a failure of the second subsystem (102).

9. A steer-by-wire steering system (1) according to any one of claims 1 to 8, characterized in that the steer-by-wire steering system (1) is designed to operate according to a method according to any one of claims 11 to 16.

10. Steer-by-wire steering system (1) according to any one of claims 1 to 9, characterized in that the communication connections (20) are designed redundantly.

11. 11. A method for operating a steer-by-wire steering 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 error-free operation, the second subsystem (102) captures angle measurements provided by the absolute angle sensor unit (7), the second subsystem (102) converts the captured angle measurements into corresponding angle information (31), and the second subsystem (102) provides the angle information (31) to the first subsystem (101) via the communication connection (20).

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

13. 13. The method according to claim 11 or 12, characterized in that in the first operating mode (BM1) configured for error-free operation, the first subsystem (101) captures position measurements provided by the absolute position sensor unit (15), the first subsystem (101) converts the captured position measurements into corresponding position information (32) regarding the position of the connecting element (12), and the first subsystem (101) provides the position information (32) to the second subsystem (102) via the communication connection (20).

14. 14. The method of claim 13, wherein the second subsystem (102) captures the position information (32) provided via the communication connection (20) and determines an absolute linking element position from the position information (32) and the relative position of the linking element (12) captured by the relative position sensor unit (16).

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

16. 16. The method according to claim 11, wherein in a second operating mode (BM2) in which the first subsystem (101) is unable to provide position information (32) due to an error of the first subsystem (101), the second subsystem (102) determines the absolute linking element position based on the relative positions of the linking elements captured by the relative position sensor unit (16) and a previously determined absolute linking element position, and information about the absolute angle of the steering shaft (2) is captured directly by the absolute angle sensor unit (7).

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