STEER-BY-WIRE STEERING SYSTEM FOR A MOTOR VEHICLE

Abstract

A steer-by-wire steering system for a motor vehicle may include a rotatably supported steering spindle, a feedback actuator with a feedback motor for acting on the steering spindle, a steering actuator with a steering motor for acting on steered wheels of the motor vehicle based on rotation of the steering spindle, and two control units for controlling the feedback motor and the steering motor. A first control unit of the two control units and a second control unit of the two control units have different levels of complexity relative to each other, in particular such that the first control unit is more powerful than the second control unit. Also, a method can be utilized to operate such a steer-by-wire steering system, whereby the first control unit and the second control unit execute procedures of different complexity relative to each other.

Claims

1.-20. (canceled)

21. A steer-by-wire steering system for a motor vehicle, comprising: a steering spindle that is rotatably supported; a feedback actuator with a feedback motor for acting on the steering spindle; a steering actuator with a steering motor for acting on steered wheels of the motor vehicle based on rotation of the steering spindle; and control units for controlling the feedback motor and the steering motor, wherein a first control unit and a second control unit of the control units have different levels of complexity.

22. The steer-by-wire steering system of claim 21 wherein the first and second control units have different levels of software complexity and/or hardware complexity.

23. The steer-by-wire steering system of claim 21 wherein the first and second control units are connected to each other for exchanging signals.

24. The steer-by-wire steering system of claim 21 wherein the first control unit comprises more powerful hardware than the second control unit.

25. The steer-by-wire steering system of claim 24 wherein the first control unit comprises a first computing unit and the second control unit comprises a second computing unit, wherein the first computing unit is configured to perform more computing operations per unit of time than the second computing unit.

26. The steer-by-wire steering system of claim 21 wherein the first control unit is configured for executing high-level software and the second control unit is configured for executing low-level software.

27. The steer-by-wire steering system of claim 21 wherein the first control unit is incorporated into a determination of a motor control signal for controlling the feedback motor and the steering motor, wherein the second control unit is incorporated into a determination of a motor control signal for controlling the feedback motor or the steering motor.

28. The steer-by-wire steering system of claim 21 wherein the first control unit is configured to receive first sensor signals, to process the first sensor signals, and to determine a first motor control signal from the first sensor signals that have been processed, wherein the second control unit is configured to receive second sensor signals, to process the second sensor signals, and to forward the second sensor signals that have been processed to the first control unit, wherein the first control unit is configured to receive the second sensor signals that have been processed and to determine a second motor control signal from the second sensor signals that have been processed.

29. The steer-by-wire steering system of claim 28 wherein the first control unit is configured to forward the second motor control signal that has been determined to the second control unit.

30. The steer-by-wire steering system of claim 21 wherein the first control unit is configured to assume a function of the second control unit in an event of a failure of the second control unit.

31. The steer-by-wire steering system of claim 21 wherein the first control unit is configured to control the feedback motor and the second control unit is configured to control the steering motor.

32. The steer-by-wire steering system of claim 31 wherein the first control unit comprises feedback platform software, feedback application software, and steering application software, wherein the second control unit comprises steering platform software, wherein the feedback platform software and the steering platform software are each configured to implement hardware-oriented, user-remote instructions, wherein the feedback application software and the steering application software are each configured to implement hardware-remote, user-oriented instructions.

33. The steer-by-wire steering system of claim 21 wherein the first control unit is configured for controlling the steering motor and the second control unit is configured for controlling the feedback motor.

34. The steer-by-wire steering system of claim 33 wherein the first control unit comprises steering platform software, steering application software, and feedback application software, wherein the second control unit comprises feedback platform software, wherein the feedback platform software and the steering platform software are each configured to implement hardware-related, user-remote instructions, wherein the feedback application software and the steering application software are each configured to implement hardware-remote, user-oriented instructions.

35. The steer-by-wire steering system of claim 21 wherein the first control unit includes an interface for connecting the first control unit to a communication bus of a motor vehicle, wherein of the first control unit and the second control unit only the first control unit is configured to exchange signals via the communication bus.

36. A method for operating the steer-by-wire steering system of claim 21, the method comprising causing the first control unit and the second control unit to execute procedures of different complexity relative to each other.

37. The method of claim 36 wherein the first control unit performs all calculations for determining a first motor control signal and all calculations for determining a second motor control signal, wherein the first control unit forwards results of the calculations for determining the second motor control signal to the second control unit, wherein the second control unit does not perform these calculations, but receives the results of the calculations for determining the second motor control signal and provides the second motor control signal.

38. The method of claim 36 wherein the first control unit receives first sensor signals, processes the first sensor signals, and determines a first motor control signal from the first sensor signals that have been processed, wherein the second control unit receives second sensor signals, processes the second sensor signals, and forwards the second sensor signals that have been processed to the first control unit, wherein the first control unit receives the second sensor signals that have been processed and determines a second motor control signal from the second sensor signals that have been processed.

39. The method of claim 38 wherein the first control unit forwards the second motor control signal that has been determined to the second control unit.

40. The method of claim 38 wherein at least one of: the first control unit is assigned to the feedback actuator and the second control unit is assigned to the steering actuator, wherein the first motor control signal is a signal for controlling the feedback motor and the second motor control signal is a signal for controlling the steering motor; or the first control unit is assigned to the steering actuator and the second control unit is assigned to the feedback actuator, wherein the first motor control signal is a signal for controlling the steering motor and the second motor control signal is a signal for controlling the feedback motor.

Description

DESCRIPTION OF THE DRAWING

[0042] Advantageous embodiments and embodiment details of the invention are explained in more detail below on the basis of the figures (Fig.: Figure). In the figures in detail

[0043] FIG. 1 shows an embodiment of a steer-by-wire steering system according to the invention in a perspective, schematic representation,

[0044] FIG. 2 shows the steer-by-wire steering system from FIG. 1 in the form of a greatly simplified block diagram and

[0045] FIG. 3 a, b shows further embodiments of a steer-by-wire steering system according to the invention, each in the form of a greatly simplified block diagram.

ADVANTAGEOUS EMBODIMENTS OF THE INVENTION

[0046] In the different figures the same parts are always provided with the same reference signs and are therefore usually only named or mentioned once.

[0047] FIG. 1 shows an embodiment of a steer-by-wire steering system 1 designed according to the invention in a perspective, schematic representation from diagonally in front in the direction of vehicle travel, wherein non-essential components are not shown for the sake of an improved overview for the description of the invention.

[0048] The steer-by-wire steering system 1 suitable for a motor vehicle, in particular for a passenger car, comprises a steering column 2 in which a steering spindle 3 is rotatably supported, a feedback actuator 4 for acting on the steering spindle 3 and a steering actuator 5 for acting on the steered wheels 6 of the motor vehicle according to the rotation of the steering spindle 2. A steering wheel 7 for entering a driver's steering input is attached to the end of the steering spindle 3 facing towards the driver. The feedback actuator 4 has a feedback motor 8 and a feedback control unit 9 for controlling the feedback motor 8. The steering actuator 5 has a steering motor 10 and a steering control unit 11 for controlling the steering motor 10,

[0049] To enable data exchange between the feedback actuator 4, in particular the feedback control unit 9, and the steering actuator 5, in particular the steering control unit 11, a data transmission device 12 in the form of a data cable connects the feedback actuator 4 to the steering actuator 5. The data transmission device 12 transmits data bidirectionally, i.e. both starting from the feedback actuator 4 in the direction of the steering actuator 5 (direction of steering input) and—vice versa—starting from the steering actuator 5 in the direction of the feedback actuator 4 (feedback direction).

[0050] In the direction of the steering input, the driver's steering input can be detected by sensor on or in the steering column 2. The sensor data relates in particular to the steering angle and steering torque. The sensor data can be transmitted via the data transmission device 12 to the steering actuator 5 acting as a final control element.

[0051] A belt gear 13 is connected to the steering actuator 5 and arranged on it. The belt gear 13 comprises a belt drive wheel 14, a belt output wheel 15 and a drive belt 16 connecting, i.e. mechanically coupling, the belt drive wheel 14 to the belt output wheel 15. The drive belt 16 is a toothed belt, wherein other types of belts can also be used, such as flat belts or V-belts. The belt output wheel 15 is torsionally coupled to a screw gear for the translation of a rotational movement into a translational movement. The screw gear is a ball screw, wherein other types of screw gears can also be used

[0052] The steering motor 10 drives the belt drive wheel 14 rotationally, so that the belt drive wheel 14 sets the belt output wheel 15 in rotation via the drive belt 16, so that the belt output wheel 15 sets a coupling rod 17 in translation along its longitudinal axis via the screw gear. The coupling rod 17, which moves linearly along its longitudinal axis, is mechanically coupled to a tie rod 18 on both sides of the motor vehicle. The tie rods 18 are in turn mechanically coupled to the vehicle wheels 6. An introduced driver's steering input can be transferred to the vehicle wheels 6 due to the described electromechanical connection.

[0053] In the feedback direction, mechanical information can be detected by sensors on or in the steering actuator 5, the belt gearbox 13, the screw gearbox, the coupling rod 17, the tie rods 18 and/or the vehicle wheels 6. These may be, for example, vibrations on the aforementioned structures caused by corrugations, potholes and/or roughness of a road 19 while driving and a mechanical resistance generated by the road surface, the road inclination and/or by cornering during steering. The driver can be given an impression of the condition of the road surface by means of haptic or tactile feedback, i.e. by applying torques corresponding to the mechanical information (feedback torques) to the steering spindle 3.

[0054] The feedback control unit 9 and the steering control unit 11 have different levels of complexity relative to each other.

[0055] FIG. 2 shows the steer-by-wire steering system 1 from FIG. 1 in the form of a greatly simplified block diagram.

[0056] As described in connection with FIG. 1, the steer-by-wire steering system 1 comprises the feedback actuator 4 and the steering actuator 5, wherein the feedback actuator 4 comprises the feedback motor 8 and the feedback control unit 9, and wherein the steering actuator 5 comprises the steering motor 10 and the steering control unit 11

[0057] The feedback motor 8 is used to introduce feedback torques into the steering spindle 3, which is not shown in FIG. 2. The feedback actuator 4 also has a feedback inverter 20 and a feedback sensor 21. The feedback inverter 20 connects the feedback motor 8 and the feedback control unit 9 electrically to each other and serves as an intermediate power stage when the feedback motor 8 is controlled by the feedback control unit 9. The feedback sensor 21 is set up to monitor the status of the feedback motor 8 and to transmit information regarding the status of the feedback motor 8 to the feedback control unit 9.

[0058] The steering motor 10 is used to generate driver steering input torques, i.e. torques that correspond to the sensor-detected driver steering inputs. A generated driver's steering input torque is converted into a linear movement of the coupling rod 17 by the mechanical coupling of the belt drive wheel 14 to the coupling rod 17. Due to the mechanical coupling of the coupling rod 17 in turn to the steered wheels 6, the wheels 6 are steered according to the driver's steering input. The steering actuator 5 also has a steering inverter 22 and a steering sensor 23. The steering inverter 22 connects the steering motor 10 and the steering control unit 11 electrically to each other and serves as an intermediate power stage when the steering motor 10 is controlled by the steering control unit 11. The steering sensor 23 is set up to monitor the condition of the steering motor 10 and to transmit information regarding the condition of the steering motor 10 to the steering control unit 11.

[0059] The feedback control unit 9 and the steering control unit 11 are each designed to exchange information via an information interface 24. The feedback control unit 9 receives the first signals from a torque sensor that is not explicitly illustrated and a rotation angle sensor that is also not explicitly illustrated. The feedback control unit 9 processes these first signals and determines a control signal for the feedback motor 8 from the processed first signals. The steering control unit 11 receives second signals from a torque sensor that is also not explicitly illustrated and a rotation angle sensor that is also not explicitly illustrated. The steering control unit 11 processes the received second signals and forwards them via the information interface 24 to the feedback control unit 9. The feedback control unit 9 receives the processed second signals via the information interface 24 and determines from these a control signal for controlling the steering motor 10. The feedback control unit 9 forwards the control signal for controlling the steering motor 10 via the information interface 24 to the steering control unit 11, which receives the control signal for controlling the steering motor 10. The steering control unit 11 controls the steering motor 10 with the received control signal for controlling the steering motor 10. The feedback control unit 9 controls the feedback motor 8 with the determined control signal for the feedback motor 8. The steering control unit 11 has a lower level of complexity than the feedback control unit 9 in that the steering control unit 11 itself is not designed to determine the control signal for controlling the steering motor 10.

[0060] FIG. 3 a) shows a further embodiment of a steer-by-wire steering system 1 according to the invention in the form of a highly simplified block diagram.

[0061] As described in connection with FIG. 1 and FIG. 2, the steer-by-wire steering system 1 comprises the feedback control unit 9 and the steering control unit 11. The feedback control unit 9 and the steering control unit 11 are each designed to exchange information via the information interface 24.

[0062] In contrast to known steer-by-wire steering systems, in which the feedback control units and the steering control units are essentially identically complex in terms of design and function, in particular have an essentially identical software complexity, in particular both have both application software and platform software, the feedback control unit 9 and the steering control unit 11 have different software levels of complexity relative to each other. The feedback control unit 9 has a lower level of software complexity than the steering control unit 11. The feedback control unit 9 comprises a feedback platform software 25. The steering control unit 11, on the other hand, comprises both a steering application software 26 and a steering platform software 27. The feedback platform software 25 and the steering platform software 27 are each designed to implement hardware-related, user-remote instructions. For this purpose, the feedback platform software 25 and the steering platform software 27 are each designed to implement instructions of the steering application software 26. The steering application software 26 is designed to implement hardware-remote, user-oriented instructions. In particular, the steering application software 26 also includes the functions of feedback application software, so that advantageously a signal for controlling the feedback motor 8 is calculated by means of the steering application software 26. In contrast to known steer-by-wire steering systems, in which each control unit has its own application software adapted to the requirements of the respective control unit, the steering application software 26 acts as the common application software of the feedback actuator 4 and the steering actuator 5. Since the two control units 9, 11 are connected to each other via the information interface 24, only a single application software is required, namely in this version the steering application software 26.

[0063] FIG. 3 b) shows a further embodiment of a steer-by-wire steering system 1 according to the invention in the form of a highly simplified block diagram.

[0064] The feedback control unit 9 and the steering control unit 11 have different levels of software complexity relative to each other. The steering control unit 11 has a lower level of software complexity than the feedback control unit 9. The steering control unit 11 comprises a steering platform software 27. The feedback control unit 9, on the other hand, comprises both a feedback platform software 25 and a feedback application software 28. The feedback platform software 25 and the steering platform software 27 are each designed to implement hardware-related, user-remote instructions. For this purpose, the feedback platform software 25 and the steering platform software 27 are each designed to implement instructions of the feedback application software 28. The feedback application software 28 is designed to implement hardware-remote, user-oriented instructions. In particular, the feedback application software 28 also includes the functions of steering application software, so that advantageously a signal for controlling the steering motor 10 is calculated by means of the feedback application software 28. In contrast to known steer-by-wire steering systems, in which each control unit has its own application software adapted to the requirements of the respective control unit, the feedback application software 28 acts as the common application software of the feedback actuator 4 and the steering actuator 5. Since the two control units 9, 11 are connected to each other via the information interface 24, only a single application software is required, namely in this version the feedback application software 28.

LIST OF REFERENCE SIGNS

[0065] 1 Steer-by-wire steering system [0066] 2 Steering column [0067] 3 Steering spindle [0068] 4 Feedback actuator [0069] 5 Steering actuator [0070] 6 Vehicle wheel [0071] 7 Steering wheel [0072] 8 Feedback motor [0073] 9 Feedback control unit [0074] 10 Steering motor [0075] 11 Steering control unit [0076] 12 Data transmission device [0077] 13 Belt drive [0078] 14 Belt drive wheel [0079] 15 Belt output wheel [0080] 16 Drive belt [0081] 17 Coupling rod [0082] 18 Tie rod [0083] 19 Road [0084] 20 Feedback inverter [0085] 21 Feedback sensor [0086] 22 Steering inverter [0087] 23 Steering sensor [0088] 24 Information interface [0089] 25 Feedback platform software [0090] 26 Steering application software [0091] 27 Steering platform software [0092] 28 Feedback application software