Steering-by-wire system and method for operating steering-by-wire system

Abstract

The invention relates to a steering-by-wire system having a steering column module and a steering gear, the steering column module having 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 two control devices for the at least one actuator for generating a counter torque, the steering gear having at least two control devices, a first control device for the at least one actuator is connected to a first control device of the steering gear via at least one bus connection, and a second control device for the at least one actuator is connected to a second control device of the steering gear via at least one bus connection.

Description

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

[0002] Steer-by-wire systems are usually designed with a mechanically decoupled and electrically connected steering column module and steering gear. The steering wheel angle is detected and transmitted to the control device of the steering gear in order to determine the target steering angle, which is then set by the steering actuator. The steering actuator is usually an electric motor, which deflects the rack to set the target steering angle at the wheel. An actuator for generating a counter torque is arranged on the steering column so that the motor vehicle driver gets the steering feel he knows from conventional steering systems. It is also known to design many of the structural units described redundantly in order to ensure fail-safety. Various solutions are known to ensure corresponding redundancy or backup levels.

[0003] Patent document US 2021 / 0009202 A1 discloses a method for controlling an actuator to generate a counter torque on a steering wheel of a steer-by-wire system.

[0004] The object of the present invention is to provide a steer-by-wire system with improved fail-safety and a corresponding method.

[0005] The solution to the above-mentioned object is achieved by a steering system having the features of claim 1 and a method having the features of claim 8. Further advantageous embodiments of the invention are disclosed in the dependent claims.

[0006] The wire control steering system has a steering column module and a steering transmission. The steering column module has a first sensor module and a second sensor module, which respectively detect at least one steering wheel angle. In addition, the steering column module 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 devices for at least one actuator for generating the counter torque. The steering wheel is generally understood here as a steering handle for presetting a desired steering angle. In addition, a first control device for at least one actuator is connected to a first control device of the steering transmission via at least one bus connection. A second control device for at least one actuator is connected to a second control device of the steering transmission via at least one second bus connection. In addition, a first sensor unit is directly connected to the first control device of the steering transmission via a sensor interface, and a second sensor unit is directly connected to the first control device for 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 system is designed such that, in fault-free operation, the first control device of at least one actuator transmits the steering wheel angle and the transmission ratio to the first control device of the steering transmission, which is then used to calculate the target steering angle. In the event of a fault in at least the first control device of at least one actuator, the steering wheel angle transmitted via the sensor interface is used by the first control device of the steering transmission to calculate the target steering angle. The first sensor module and the first control device of the steering transmission have a common voltage supply. This increases overall fault safety because the steering wheel angle is transmitted via two different transmission paths, namely one via the bus connection and one via the sensor interface. The common voltage supply of the first sensor module and the first control device of the steering transmission allows the first sensor module to continue to operate even if the voltage supply of the first control device of at least one actuator fails. The transmission ratio can then be provided to the first control device from another unit in the event of a fault, and it uses the last transmitted transmission ratio.

[0007] In a first embodiment, the steer-by-wire system is designed such that only in the event of a failure of the first control device and the second control device for the at least one actuator, the steering wheel angle transmitted from the first sensor module to the first control device of the steering gear via the sensor interface is used to calculate the target steering angle. This has the advantage that the target steering angle and the counter torque are better coordinated if the control device of the at least one actuator still operates without failure, wherein the steering wheel angle of the sensor interface is used only in the event of a double failure or a complete failure of the steering column module.

[0008] In another embodiment, the first and second sensor modules are designed to additionally detect hand torques.

[0009] In another embodiment, at least one actuator for generating the counter torque is designed as an electric motor with a first and a second set of windings that are independent of one another, wherein the first set of windings is controlled by a first control device for the actuator and the second set of windings is controlled by a second control device. This enables a very simple and cost-effective implementation of redundant actuators. For example, one set each comprises three windings. Since the first and second control devices preferably have different voltage supplies and the rotor of the electric motor is very robust and fail-safe, the actuator can operate in the event of various individual faults.

[0010] In another embodiment, the first control device of the actuator and the first control device 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 a dedicated bus system (e.g. a dedicated CAN) via which the steering wheel angle and the transmission ratio are transmitted. The advantage is that the data transmission is very fast compared to other vehicle bus systems. In the event of a failure of the dedicated bus system, the second bus system can be used.

[0011] In another embodiment, the first control device and the second control device of the at least one actuator have a communication connection, wherein the steer-by-wire system is designed such that the first control device transmits at least one steering wheel angle starting value to the second control device. Preferably, the communication takes place continuously so that the second control device knows the current steering wheel angle and the transmission ratio. The communication connection can also be designed as a dedicated bus connection (e.g. a dedicated CAN).

[0012] In a further specific embodiment, the second control device of the actuator is designed to determine the absolute steering wheel angle via the rotor angle of the steering gear.

[0013] The design scheme in terms of method completely refers to the above design scheme.

[0014] The present invention is further explained below based on preferred embodiments: The single figure shows a schematic block diagram of a steer-by-wire system.

[0015] Figure 1Schematically shown in FIG. 1 is a steer-by-wire system 1. The steer-by-wire 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 φ and a hand torque on the steering wheel 4. In addition, the steering column module 2 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 group 9 and a second group 10 of windings, wherein the first group 9 of windings is controlled by a first control device 11 and the second group 10 of windings is controlled by a second control device 12, wherein the associated power electronics are not shown for the sake of clarity. The first control device 11 and the second control device 12 are connected to each other via a communication connection 13. The second sensor module 7 is connected to the first control device 11 for the actuator 8 via a sensor interface 14. The steering gear 3 has a first control device 15 and a second control device 16. Furthermore, the steering gear 3 has two power electronics 17, 18, which respectively control half motors 19, 20. The two half motors 19, 20 operate on a common rotor 21, which is connected to a rack 22 via a gear mechanism (not shown). Two control devices 15, 16 control the power electronics 17, 18. As shown in the figure, one control device 15, 16 can control both power electronics 17, 18, or one control device 15, 16 can control one power electronics 17, 18. A communication connection 23 between the first control device 15 and the second control device 16 is also shown. The first sensor module 6 is directly connected to the first control device 15 of the steering gear 3 via a sensor interface 24. The first control device 11 of the actuator 8 is connected to the first control device 15 of the steering gear 3 via a first bus system 25 and a second bus system 26. Here, the first bus system 25 is designed as a dedicated bus system, while the second bus system 26 is designed as a vehicle bus system, on which other control devices also communicate, as indicated by the outgoing lines. The control device 11 transmits the steering wheel angle φ and the transmission ratio ü of the second sensor module 7 to the first control device 15 of the steering gear 3 via the first bus system 25. In addition, the second control device 12 of the actuator 8 is connected to the second control device 16 of the steering gear 3 via a further bus system 27, which is also designed as a vehicle bus system, for example. The rotor angle φ is also shown. Ris transmitted to the second control device 16, but can alternatively or additionally also be supplied to the first control device 15. The voltage supply is not shown, whereby it is applicable that the redundant elements each have a different voltage supply. It can also be provided that the steering column module 2 has a first and a second voltage supply, and the steering gear 3 has a first and a second voltage supply, wherein these voltage supplies can be identical or independent of one another. In this case, the voltage supply of the first sensor module 6 is identical to that of the first control device 15 for the steering gear 3.

[0016] In fault-free operation, the first control device 11 transmits the steering wheel angle φ and the transmission ratio ü to the first control device 15 of the steering gear 3 via the bus system 25, and the first control device then determines the target steering angle and controls the power electronics 17, 18 accordingly. In the event of a fault in the first control device 11, the steering wheel angle φ and the transmission ratio ü can be transmitted from the second control device 12 to the second control device 16 of the steering gear 3, wherein, when the transmission ratio ü is known, the rotor angle φ can be determined. R Determine the steering wheel angle φ. If the second control device 12 also fails, the first control device 15 still obtains the steering wheel angle φ from the first sensor module 6 and can calculate the corresponding target steering angle. In this case, the first control device 15 can also obtain the transmission ratio ü from other control devices. In terms of data transmission speed, the transmission via the sensor interface is the fastest, followed by the dedicated bus system, and the vehicle bus system is the slowest.

[0017] List of reference numerals:

[0018] 1) Steer-by-wire system

[0019] 2) Steering column module

[0020] 3) Steering transmission

[0021] 4) Steering wheel

[0022] 5) Steering column

[0023] 6) First sensor module

[0024] 7) Second sensor module

[0025] 8) Actuator

[0026] 9) The first winding

[0027] 10) The second winding

[0028] 11) First control device for actuator

[0029] 12) Second control device for actuator

[0030] 13) Communication connection

[0031] 14) Sensor interface

[0032] 15) First control device for steering transmission

[0033] 16) Second control device for steering transmission

[0034] 17) Power electronic devices

[0035] 18) Power electronic devices

[0036] 19) Half motor

[0037] 20) Half motor

[0038] 21) Common rotor

[0039] 22) Rack

[0040] 23) Communication connection

[0041] 24) Sensor interface

[0042] 25) First bus system

[0043] 26) Second bus system

[0044] 27) Other bus systems

[0045] φ) Steering wheel angle

[0046] ü) Transmission ratio

[0047] φ R )Rotor angle

Claims

1. A steer-by-wire system (1), wherein: The steer-by-wire system (1) comprises a steering column module (2) and a steering transmission (3), wherein the steering column module (2) comprises a first sensor module (6) and a second sensor module (7), wherein the first sensor module and the second sensor module respectively detect at least one steering wheel angle (φ), wherein the steering column module (2) further comprises 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, wherein the steering transmission (3) comprises at least two control devices (15, 16), wherein a first control device (11) for the at least one actuator (8) is connected to a first control device (15) of the steering transmission (3) via at least one bus connection (25, 26), and a second control device (12) for the at least one actuator (8) is connected to a second control device (15) of the steering transmission (3) via at least one bus connection (25, 26). (16) are connected via at least one bus connection (27), wherein the first sensor unit (6) is directly connected to the first control device (15) of the steering transmission (3) via the sensor interface (24), and the second sensor unit (7) is directly connected to the first control device (11) for at least one actuator (8) via the sensor interface (14), wherein the wire-controlled steering system (1) is constructed so that, in fault-free operation, the first control device (11) transmits the steering wheel angle (φ) and the transmission ratio (ü) to the first control device (15) of the steering transmission (3) and then uses them to calculate the target steering angle, wherein, when at least the first control device (11) of at least one actuator (8) fails, the steering wheel angle (φ) transmitted via the sensor interface (24) is used by the first control device (15) of the steering transmission (3) to calculate the target steering angle, wherein the first sensor module (6) and the first control device (15) of the steering transmission (3) have a common voltage supply device.

2. The steer-by-wire system according to claim 1, characterized in that: The steer-by-wire system (1) is designed such that only when a first control device (11) and a second control device (12) for at least one actuator (8) fail, a steering wheel angle (φ) transmitted from a first sensor module (6) to a first control device (15) of a steering transmission (3) via a sensor interface (24) is used to calculate a target steering angle.

3. The steer-by-wire system according to claim 1 or 2, characterized in that: The first sensor module (6) and the second sensor module (7) are designed to additionally detect hand torque.

4. A steer-by-wire system according to any one of the preceding claims, characterized in that At least one actuator (8) for generating a counter torque is designed as an electric motor having a first group (9) of windings and a second group (10) of windings which are independent of each other, wherein the first group (9) of windings is controlled by a first control device (11) for the actuator (8) and the second group (10) of windings is controlled by a second control device (12).

5. The steer-by-wire system according to any one of the preceding claims, characterized in that A first control device (11) of an actuator (8) and a first control device (15) of a steering transmission (3) are connected to each other via a first bus system (25) and a second bus system (28), wherein the first bus system (25) is designed as a dedicated bus system through which a steering wheel angle (φ) and a transmission ratio (ü) are transmitted.

6. A steer-by-wire system according to any one of the preceding claims, characterized in that A first control device (11) and a second control device (12) of at least one actuator (8) have a communication connection (13), wherein the steer-by-wire system (1) is designed such that the first control device (11) transmits at least one steering wheel angle starting value to the second control device (12).

7. The steer-by-wire system according to claim 6, characterized in that: The second control device (12) is configured to control the rotor angle (φ) of the steering gear R ) determines the absolute steering wheel angle.

8. A method for operating a steer-by-wire system, wherein: The steering-by-wire system (1) comprises a steering column module (2) and a steering transmission (3), wherein the steering column module (2) comprises a first sensor module (6) and a second sensor module (7), wherein the first sensor module and the second sensor module respectively detect at least one steering wheel angle (φ), wherein the steering column module (2) also comprises 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, wherein the steering transmission (3) comprises at least two control devices (15, 16), wherein a first control device (11) for the at least one actuator (8) is connected to a first control device (15) of the steering transmission (3) via at least one bus connection (25, 26), and a second control device (12) for the at least one actuator (8) is connected to the steering transmission (3) via at least one bus connection (25, 26). A second control device (16) of the steering gear (3) is connected via at least one bus connection (27), wherein the first sensor module (6) is directly connected to the first control device (15) of the steering gear (3) via a sensor interface (24), and the second sensor unit (7) is directly connected to the first control device (11) for at least one actuator (8) via the sensor interface (14), wherein in fault-free operation, the first control device (11) transmits a steering wheel angle (φ) and a transmission ratio (ü) to the first control device (15) of the steering gear (3), which are then used to calculate a target steering angle, wherein in the event of a fault in at least the first control device (11) of at least one actuator (8), the steering wheel angle (φ) transmitted via the sensor interface (24) is used by the first control device (15) of the steering gear (3) to calculate the target steering angle, wherein the first sensor module (6) and the first control device (15) of the steering gear (3) have a common voltage supply.

9. The method according to claim 8, characterized in that Only when a first control device (11) and a second control device (12) for at least one actuator (8) fail, a steering wheel angle (φ) transmitted from a first sensor module (6) via a sensor interface (24) to a first control device (15) of a steering gear (3) is used to calculate a target steering angle.

10. The method according to claim 8 or 9, characterized in that The first sensor module (6) and the second sensor module (7) additionally detect hand torque.

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