Steer-by-wire steering system, and method for operating a steer-by-wire steering system

Abstract

The invention relates to a steer-by-wire steering system (1), the steer-by-wire steering system (1) comprising a steering column module (2) and a steering gear (3), the steering column module (2) comprising a first sensor module (6) and a second sensor module (7) which each sense at least one steering wheel angle (φ), the steering column module (2) also comprising a steering wheel (4), a steering column (5), at least one actuator (8) for generating a counter-torque on the steering column (5), and two control devices (11, 12) for the at least one actuator (8) for generating the counter-torque, the steering gear (3) having at least two control devices (15, 16), the first control device (11) for the at least one actuator (8) being connected to a first control device (15) of the steering gear (3) via at least one bus connection (25, 26), and the second control device (12) for the at least one actuator (8) being connected to a second control device (16) of the steering gear (3) via at least one bus connection (27), the first sensor unit (6) being directly connected to the first control device (15) of the steering gear (3) via a sensor interface (24), and the second sensor unit (7) being directly connected to the first control device (11) for the at least one actuator (8) via a sensor interface (14).

Description

[0001] Description

[0002] Steer-by-wire steering system and method for operating a steer-by-wire steering system

[0003] The invention relates to a steer-by-wire steering system and a method for operating a steer-by-wire steering system.

[0004] Steer-by-wire steering systems are typically designed with a steering column module and a steering gear that are mechanically decoupled and electrically connected. A steering wheel angle is detected and transmitted to a steering gear control unit to determine a target steering angle, which is then adjusted using a steering actuator. The steering actuator is typically an electric motor that deflects a rack to adjust the target steering angle at the wheels. An actuator is mounted on the steering column to generate a counter-torque, giving the driver a steering feel similar to that experienced with conventional steering systems. It is also common practice to design many of these components redundantly to ensure fail-safe operation. A wide variety of concepts exist for ensuring this redundancy or fallback capability.

[0005] From US 2021 / 0009202 A1, a method for controlling an actuator to generate a counter torque on a steering wheel of a steer-by-wire steering system is known.

[0006] The invention is based on the technical problem of creating a steer-by-wire steering system that has improved reliability and of providing a corresponding method.

[0007] The solution to the technical problem is provided by a steering system having the features of claim 1 and a method having the features of claim 7. Further advantageous embodiments of the invention emerge from the subclaims.

[0008] The steer-by-wire steering system has a steering column module and a steering gear. The steering column module has a first sensor module and a second sensor module, each of which detects at least one steering wheel angle. The steering column module also has a steering wheel, a steering column, at least one actuator for generating a counter-torque on the steering column, and at least two control units for the at least one actuator for generating the counter-torque. Steering wheel is generally understood here as a steering handle for specifying a desired steering angle. Furthermore, the first control unit for the at least one actuator is connected to a first control unit of the steering gear via at least one bus connection. The second control unit for the at least one actuator is connected to a second control unit of the steering gear via at least one second bus connection.Furthermore, the first sensor unit is connected directly to the first control unit of the steering gear via a sensor interface, and the second sensor unit is connected directly to the first control unit for the at least one actuator via a sensor interface. The sensor interface is preferably designed as a SENT (Single Edge Nibble Transmission) interface. The steer-by-wire steering system is designed such that, during fault-free operation, the first control unit of the at least one actuator transmits a transmission ratio to the first control unit of the steering gear, and the first sensor unit transmits a steering wheel angle directly to the first control unit of the steering gear. These signals are then used to calculate the target steering angle.In the event of a fault in the first sensor unit and / or the sensor interface, the steering wheel angle and the gear ratio of the first control unit of the actuator are transmitted to the first control unit of the steering gear and used to calculate the target steering angle. The first sensor module and the first control unit of the steering gear have a common power supply. This improves overall reliability because the steering wheel angle is transmitted via two different transmission paths, namely via a sensor interface and via a bus connection. Due to the shared power supply of the first sensor module and the first control unit of the steering gear, the first sensor module continues to function even if the power supply of the first control unit of the at least one actuator fails. A further advantage is the extremely fast data transmission of the steering wheel angle via the sensor interface.This allows the steer-by-wire steering system to respond much more dynamically overall. Since the gear ratio isn't subject to such dynamic changes, the somewhat slower transmission via the bus system isn't critical.

[0009] In one embodiment, the first and second sensor modules are designed to additionally detect a hand torque.

[0010] In a further embodiment, the at least one actuator for generating a counter torque is designed as an electric motor with a first set and a second set of windings that are independent of one another, wherein the first set of windings is controlled by the first control unit for the actuator and the second set of windings is controlled by the second control unit. This enables a very simple and cost-effective implementation of a redundant actuator. For example, each set has three windings. Since the first and second control units preferably have different power supplies and the rotor of the electric motor is very robust and fail-safe, the actuator is functional despite a wide variety of individual faults.

[0011] In a further embodiment, the first control unit of the actuator and the first control unit of the steering gear are connected to each other via a first bus system and a second bus system, wherein the first bus system is designed as an exclusive bus system (e.g., private CAN) via which the steering wheel angle and the transmission ratio are transmitted. The advantage is the very fast data transmission compared to other vehicle bus systems. If the exclusive bus system fails, the second bus system can then be used.

[0012] In a further embodiment, the first control unit and the second control unit of the at least one actuator have a communication connection, wherein the steer-by-wire steering system is configured such that the first control unit transmits at least one steering wheel angle starting value to the second control unit. Preferably, the communication takes place continuously, so that the second control unit knows the current steering wheel angle and the gear ratio. The communication connection can also be configured as an exclusive bus connection (e.g., private CAN).

[0013] In a further embodiment, the second control unit of the actuator is designed to determine an absolute steering wheel angle by means of a rotor angle of the steering gear.

[0014] With regard to the procedural details, reference is made in full to the preceding statements.

[0015] The invention is explained in more detail below using a preferred embodiment. The sole figure shows a schematic block diagram of a steer-by-wire steering system.

[0016] Fig. 1 schematically shows a steer-by-wire steering system 1. The steer-by-wire steering system 1 has a steering column module 2 and a steering gear 3. The steering column module 2 has a steering wheel 4 and a steering column 5. A first sensor module 6 and a second sensor module 7 are arranged on the steering column 5, wherein the first sensor module 6 and the second sensor module 7 are designed to detect a steering wheel angle (p) and a manual torque on the steering wheel 4. The steering column module 2 also has an actuator 8 for generating a counter-torque on the steering wheel 4, wherein the actuator 8 is designed as an electric motor with a first set 9 and a second set 10 of windings, wherein the first set 9 of windings is controlled by a first control unit 11 and the second set 10 of windings is controlled by a second control unit 12, wherein the associated power electronics are not shown for reasons of clarity.The first control unit 11 and the second control unit 12 are connected to one another via a communication connection 13. The second sensor module 7 is connected to the first control unit 11 for the actuator 8 via a sensor interface 14. The steering gear 3 has a first control unit 15 and a second control unit 16. The steering gear 3 also has two power electronics units 17, 18, each of which controls a half-motor 19, 20. The two half-motors 19, 20 operate on a common rotor 21, which is connected to a rack 22 via a gear (not shown). The two control units 15, 16 control the power electronics units 17, 18. As shown, one control unit 15, 16 can control both power electronics units 17, 18, or one control unit 15, 16 can control one power electronics unit 17, 18. Furthermore, a communication connection 23 between the first control unit 15 and the second control unit 16 is shown.The first sensor module 6 is directly connected to the first control unit 15 of the steering gear 3 via a sensor interface 24. The first control unit 11 of the actuator 8 is connected to the first control unit 15 of the steering gear 3 via a first bus system 25 and a second bus system 26. The first bus system 25 is designed as an exclusive bus system, whereas the second bus system 26 is designed as a vehicle bus system on which other control units also communicate, as indicated by the outgoing line. Via the first bus system 25, the control unit 11 transmits the steering wheel angle (p) of the second sensor module 7 and the gear ratio ü to the first control unit 15 of the steering gear 3. Furthermore, the second control unit 12 of the actuator 8 is connected to the second control unit 16 of the steering gear 3 via a further bus system 27, which is also designed as a vehicle bus system, for example.It is further shown that a rotor angle q>R is transmitted to the second control unit 16, which can alternatively or additionally also be supplied to the first control unit 15. The power supplies are not shown; redundant elements each have a different power supply. It can further be provided that the steering column module 2 has a first and second power supply, and the steering gear 3 has a first and second power supply, which can be the same or independent of one another. The power supply of the first sensor module 6 is the same as that for the first control unit 15 of the steering gear 3.

[0017] During fault-free operation, the first control unit 11 transmits the gear ratio ü to the first control unit 15 of the steering gear 3 via the bus system 25, and the first sensor unit 6 transmits a steering angle (p) to the first control unit 15 of the steering gear 3, which then determines a target steering angle therefrom and controls the power electronics 17, 18 accordingly. It should be noted that the first control unit 11 can also additionally transmit a steering wheel angle (p), which, however, is then ignored by the first control unit 15 of the steering gear 3 when calculating the target steering angle during fault-free operation. In the event of a failure of the first sensor unit 6 and / or the sensor interface 24, the first control unit 15 of the steering gear 3 then uses the transmitted steering wheel angle (p) and the gear ratio ü from the first control unit 11 of the actuator.If the first control unit 11 of the actuator 8 also fails, the steering wheel angle and the transmission ratio are transmitted from the second control unit 12 of the actuator 8 to the second control unit 16 of the steering gear 3. If the first control unit 11 of the actuator 8 fails, with the first sensor unit 6 intact, the first control unit 15 of the steering gear 3 receives the transmission ratio ü from another control unit (e.g., from the second control unit 12 of the actuator 8). In terms of data transmission speed, transmission via sensor interfaces is the fastest, followed by exclusive bus systems, whereas vehicle bus systems are the slowest.

[0018] List of reference symbols ) Steer-by-Wire steering system ) Steering column module ) Steering gear ) Steering wheel ) Steering column ) First sensor module ) Second sensor module ) Actuator ) First set of windings 0) Second set of windings 1) First control unit for the actuator 2) Second control unit for the actuator 3) Communication link 4) Sensor interface 5) First control unit for steering gear 6) Second control unit for steering gear 7) Power electronics 8) Power electronics 9) Half-motor 0) Half-motor 1) Common rotor 2) Rack 3) Communication link 4) Sensor interface 25) First bus system

[0019] 26) second bus system

[0020] 27) additional bus system

[0021] (p) Steering wheel angle ü) Gear ratio

[0022] (p R ) Rotor angle

Claims

Claims Steer-by-wire steering system (1), wherein the steer-by-wire steering system (1) has a steering column module (2) and a steering gear (3), wherein the steering column module (2) has a first sensor module (6) and a second sensor module (7), each of which detects at least one steering wheel angle (cp), wherein the steering column module (2) further has a steering wheel (4), a steering column (5), at least one actuator (8) for generating a counter-torque on the steering column (5) and two control units (11, 12) for the at least one actuator (8) for generating the counter-torque, wherein the steering gear (3) has at least two control units (15, 16), wherein the first control unit (11) for the at least one actuator (8) is connected to a first control unit (15) of the steering gear (3) via at least one bus connection (25, 26) and the second control unit (12) for the at least one Actuator (8) is connected to a second control unit (16) of the steering gear (3) via at least one bus connection (27),wherein the first sensor unit (6) is connected via a sensor interface (24) directly to the first control unit (15) of the steering gear (3) and the second sensor unit (7) is connected via a sensor interface (14) directly to the first control unit (11) for the at least one actuator (8), wherein the steer-by-wire steering system (1) is designed such that, in fault-free operation, the first control unit (11) of the actuator (8) transmits a transmission ratio (ü) to the first control unit (15) of the steering gear (3) and the first sensor unit (6) transmits a steering wheel angle (cp) directly to the first control unit (15) of the steering gear (3), which are then used to calculate a target steering angle, wherein in the event of a fault in the first sensor unit (6) and / or the sensor interface (24), the steering wheel angle (cp) and the transmission ratio (ü) of the first control unit (11) are transmitted to the first control unit (15) of the steering gear (3) and used to calculate the target steering angle,wherein the first sensor module (6) and the first control unit (15) of the steering gear (3) have a common power supply. Steer-by-wire steering system according to claim 1, characterized in that the first sensor module (6) and the second sensor module (7) are configured to additionally detect a manual torque. Steer-by-wire steering system according to one of the preceding claims, characterized in that the at least one actuator (8) for generating a counter-torque is designed as an electric motor with a first set (9) and a second set (10) of windings which are independent of one another, wherein the first set (9) of windings from the first control unit (11) for the actuator (8) and the second set (10) of windings is controlled by the second control unit (12). Steer-by-wire steering system according to one of the preceding claims, characterized in that the first control unit (11) of the actuator (8) and the first control unit (15) of the steering gear (3) are connected to one another via a first bus system (25) and a second bus system (28), wherein the first bus system (25) is designed as an exclusive bus system via which the steering wheel angle (φ) and the transmission ratio (φ) are transmitted. Steer-by-wire steering system according to one of the preceding claims, characterized in that the first control unit (11) and the second control unit (12) of the at least one actuator (8) have a communication connection (13), wherein the steer-by-wire steering system (1) is designed such that the first control unit (11) transmits at least one steering wheel angle start value to the second control unit (12).Steer-by-wire steering system according to claim 5, characterized in that the second control unit (12) is designed such that by means of a rotor angle ( <PR) des Lenkgetriebes einen absoluten Lenkradwinkel zu bestimmen.Method for operating a steer-by-wire steering system, wherein the steer-by-wire steering system (1) has a steering column module (2) and a steering gear (3), wherein the steering column module (2) has a first sensor module (6) and a second sensor module (7), each of which detects at least one steering wheel angle (cp), wherein the steering column module (2) further has a steering wheel (4), a steering column (5), at least one actuator (8) for generating a counter-torque on the steering column (5) and two control units (11, 12) for the at least one actuator (8) for generating the counter-torque, wherein the steering gear (3) has at least two control units (15, 16), wherein the first control unit (11) for the at least one actuator (8) is connected to a first control unit (15) of the steering gear (3) via at least one bus connection (25, 26) and the second control unit (12) for the at least one Actuator (8) with a second control unit (16) of the steering gear (3) via at least one bus connection (27).is connected, wherein the first sensor unit (6) is connected via a sensor interface (24) directly to the first control unit (15) of the steering gear (3) and the second sensor unit (7) is connected via a sensor interface (14) directly to the first control unit (11) for the at least one actuator (8), wherein, in fault-free operation, the first control unit (11) of the actuator (8) transmits a transmission ratio (ü) to the first control unit (15) of the steering gear (3) and the first sensor unit (6) transmits a steering wheel angle (cp) directly to the first control unit (15) of the steering gear (3), which are then used to calculate a target steering angle, wherein, in the event of a fault in the first sensor unit (6) and / or the sensor interface (24), the steering wheel angle (cp) and the transmission ratio (ü) of the first control unit (11) are transmitted to the first control unit (15) of the steering gear (3) and used to calculate the target steering angle,wherein the first sensor module (6) and the first control unit (15) of the steering gear (3) have a common power supply. Method according to claim 7, characterized in that the first sensor module (6) and the second sensor module (7) additionally detect a manual torque. Method according to claim 7 or 8, characterized in that the first control unit (11) of the actuator (8) and the first control unit (15) of the steering gear (3) are connected to one another via a first bus system (25) and a second bus system (28), wherein the first bus system (25) is designed as an exclusive bus system via which the steering wheel angle (φ) and the transmission ratio (φ) are transmitted. Method according to one of claims 7 to 9, characterized in that the first control unit (11) and the second control unit (12) of the at least one actuator (8) have a communication connection (13).wherein the first control unit (11) transmits at least one steering wheel angle start value to the second control unit (12).

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