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

Abstract

Steer-by-wire steering system (1) comprising a steering column module (2) and a steering gear (3), wherein the steering column module (2) has at least a steering wheel (4), a steering column (10), at least one rotation angle sensor (5), at least one actuator (8) for generating a counter-torque on the steering wheel (4) and at least one control unit (7) for controlling the actuator (8), wherein the control unit (7) has a microprocessor (11) and power electronics (12), wherein the control unit (7) is configured to determine a steering wheel angle (ηL) on the basis of the data from a rotor position sensor of the actuator (8), wherein the microprocessor (11) transmits the steering wheel angle (ηL) for the actuator (8) to a first vehicle bus (20) and the steering wheel angle (ηL)L) directly via a separate data line (18) to the steering gear (3), wherein the steering gear (3) is connected to the first vehicle bus (20), characterized in that a microprocessor (15) of the steering angle sensor (5) is arranged in the control unit (7), wherein the microprocessor (15) of the steering angle sensor (5) transmits the steering wheel angle (ΔL) via a direct data connection (16) to the microprocessor (11) for the actuator (8) and transmits it to the first vehicle bus (20).

Description

The invention relates to a steer-by-wire steering system, a control device and a method for operating a steer-by-wire steering system according to the preambles of independent claims 1, 7 and 8.Steer-by-wire steering systems have a steering column module and a steering gear which are mechanically decoupled. The steering column module typically comprises a steering wheel, a steering column, a rotational angle sensor, at least one actuator for generating a counter-torque on the steering wheel and at least one control unit for actuating the actuator. A steering wheel is generally understood to mean a steering handle. The actuator, which is also referred to as a force feedback actuator, is an electric motor which is coupled to the steering column, if appropriate, via a transmission. By means of the actuator, not only a counter torque is generated at the steering wheel, but also the steering wheel is turned back in the direction of a neutral position if no hand torque is applied to the steering wheel.From DE 10 2018 121 610 A1 a steering column module for a steer-by-wire steering system of a vehicle is known, comprising a force feedback actuator, a sensor unit for detecting an operating parameter of the vehicle and a control unit, wherein the steering column module can be fastened to the vehicle as a module that can be handled individually.It is desirable that the steering wheel angle is redundantly transmitted to the steering gear as a control signal for the steering gear, in order to improve the reliability of a steer-by-wire steering system.From the generic DE 10 2019 007 715 A1, a steer-by-wire system for a vehicle is known, comprising a first subsystem and a second subsystem, which are independent of one another and are each designed for detecting a steering handle angle of a steering handle of the vehicle by means of a steering handle angle sensor in each case and for steering the vehicle by setting a wheel angle of at least one wheel of the vehicle as a function of the detected steering handle angle by means of a steering actuator unit in each case. Furthermore, a third subsystem independent of the two subsystems is provided, which is designed to detect the steering handle angle of the steering handle of the vehicle by means of a third steering handle angle sensor and to steer the vehicle as a function of the detected steering handle angle by means of at least one transverse guidance influencing system independent of the first subsystem and the second subsystem. Preferably, the first subsystem and the second subsystem each comprise a force feedback actuator unit, wherein the steering handle angle is determined on the basis of a rotor position of an electric motor of the force feedback actuator unit.The invention is based on the technical problem of creating a steer-by-wire steering system in which the steering wheel angle can be transmitted redundantly to a steering gear. Another technical problem is the provision of a control device for an actuator and the provision of a suitable method for operating a steer-by-wire steering system.The solution of the technical problem is achieved by a steer-by-wire steering system having the features of claim 1, a control device having the features of claim 7 and a method having the features of claim 8.The steer-by-wire steering system includes a steering column module and a steering gear. The steering column module has at least one steering wheel, a steering column, at least one angle of rotation sensor, at least one actuator for generating a counter-torque on the steering wheel and at least one control unit for actuating the actuator. The control unit has a microprocessor and power electronics, wherein the control unit is designed to determine a steering wheel angle on the basis of the data of a rotor position sensor of the actuator. If the actuator is coupled to the steering column via a transmission, the microprocessor additionally requires the transmission ratio in order to draw conclusions about the steering wheel angle from the rotor position. Furthermore, the rotation angle sensor is assigned its own separate microprocessor, which is arranged in the control unit. The microprocessor for the angle-of-rotation sensor can be arranged on a separate printed circuit board. The microprocessor for the angle-of-rotation sensor is connected via a direct data connection to the microprocessor of the actuator, via which the microprocessor of the angle-of-rotation sensor transmits the steering wheel angle of rotation to the microprocessor for the actuator. Here, the steering wheel angle of the rotation angle sensor is an absolute steering wheel angle. Thus, the microprocessor for the actuator has two steering wheel angles, namely the steering wheel angle from the microprocessor of the angle of rotation sensor and a steering wheel angle on the basis of the rotor position of the actuator. In addition to the transmission ratio of a transmission which may be present, the microprocessor may also receive the data of an index sensor which specifies the number of complete revolutions. Furthermore, the steer-by-wire steering system is designed in such a way that both the microprocessor for the actuator and the microprocessor for the angle-of-rotation sensor can transmit the steering wheel angle to a first vehicle bus, wherein the steering gear is connected to the first vehicle bus. In addition, the microprocessor for the actuator transmits the steering wheel angle via a separate data line to the steering gear. The separate data line is, for example, a private CAN connection, wherein the transmission speed can be considerably higher than on the vehicle bus. The data transmission can also be encrypted. Since the microprocessor for the angle-of-rotation sensor is spatially very close to the microprocessor of the actuator, the data connection between them can likewise be very fast. Thus, the steering gear obtains the steering wheel angle redundantly via two independent data connections.In one embodiment, a second microprocessor and a second power electronics are arranged in the control unit, said second microprocessor actuating a second actuator for generating a counter-torque, wherein the first microprocessor and the second microprocessor are connected in terms of data, wherein the second microprocessor is designed to transmit the steering wheel angle to a second vehicle bus. This provides further redundancy. In this case, it can be provided that the second actuator is only actuated if the first actuator fails. However, it can also be provided that the two actuators are operated simultaneously.In a further embodiment, the microprocessor of the first actuator is designed to receive an index signal over full rotations of the steering wheel.In a further embodiment, the first actuator, the first microprocessor for the first actuator and the first power electronics are connected to a first voltage supply and the second actuator, the second microprocessor for the second actuator and the second power electronics are connected to a second voltage supply.In a further embodiment, the microprocessor for the angle of rotation sensor is connected via a decoupling element to the voltage supply of the first microprocessor for the first actuator, wherein a buffer store is arranged between decoupling element and microprocessor. The decoupling element is designed, for example, as a diode and the buffer memory as a capacitor.In a further embodiment, the steering column module has at least one torque sensor, by means of which the hand torque applied to the steering wheel is measured.With regard to the configuration of the control unit and the configuration according to the method, reference is made in full to the preceding explanations.The invention is explained in more detail below with reference to a preferred exemplary embodiment. The figures show: FIG. 1 is a schematic block diagram of a steer-by-wire steering system; and FIG. 2 shows a partial illustration of a voltage supply of a microprocessor of a rotation angle sensor.FIG. 1 shows a schematic block diagram of a steer-by-wire steering system 1 which has a steering column module 2 and a steering gear 3. The steering column module 2 has a steering wheel 4, a rotational angle sensor 5, a torque sensor 6, a control unit 7, a first actuator 8 and a second actuator 9 for generating a counter-torque at the steering wheel 4, and a steering column 10. The control unit 7 has a first microprocessor 11 and first power electronics 12 in order to actuate the first actuator 8. Furthermore, the control unit 7 has a second microprocessor 13 and second power electronics 14 in order to actuate the second actuator 9. Finally, the control device 7 also has a microprocessor 15 of the angle-of-rotation sensor 5, which converts the sensor signals of the angle-of-rotation sensor 5 into a steering wheel angle φ L. The microprocessor 15 is connected to the first microprocessor 11 via a direct data connection 16. Furthermore, the first microprocessor 11 and the second microprocessor 13 are connected to one another via a further, separate, direct data connection 17, via which the two microprocessors 11, 13 monitor one another, for example. It is also shown that the two actuators 8, 9 each transmit their rotor position angles φ R1 and φ R2 to the control unit 7. From the rotor position angles φ R1, φ R2 and a transmission ratio of a transmission, not shown in each case, between actuator 8 or 9 and steering column, the respective microprocessor 11, 13 then calculates a steering wheel angle. For this purpose, the microprocessors 11, 13 also receive an index signal I from an index sensor, not shown. The first microprocessor 11 is connected to the steering gear 3 via a separate direct data line 18. Furthermore, the first microprocessor 11 has a connection 19 to a first vehicle bus 20. The microprocessor 15 of the angle-of-rotation sensor 5 likewise has a connection 21 to the first vehicle bus 20. Correspondingly, the second microprocessor 13 has a connection 22 to a second vehicle bus 23. The steering gear 3 likewise has a connection 24 to the first vehicle bus 20 and a connection 25 for the second vehicle bus 23. In this case, the steering gear 3 can have two control units, wherein the first control unit is connected to the first vehicle bus and to the data line 18, wherein the second control unit is connected to the second vehicle bus 23. The steering gear 3 has a rotor 26 which is coupled to a toothed rack 27. The first microprocessor 11, the first power electronics 12, the first actuator 8 and the microprocessor 15 of the angle-of-rotation sensor 5 are connected to a first voltage supply U 1, whereas the second microprocessor 13, the second power electronics 14 and the second actuator 9 are connected to a second, independent voltage supply U 2. Accordingly, the redundant components of the steering gear are also supplied by the two voltage supplies U 1, U 2.When the motor vehicle is started, the microprocessor 15 determines the absolute steering wheel angle φ L and transmits it on the one hand to the first microprocessor 11 and transmits it to the first vehicle bus 20. The first microprocessor 11 then transmits the steering wheel angle φ L as a control signal to the steering gear 3 via the direct, separate data line 18. additionally, the first microprocessor 11 also transmits the steering wheel angle φ L to the first vehicle bus 20. Since the steering gear 3 additionally receives the steering wheel angle φ L from the second microprocessor 13 via the second vehicle bus 23, it is also ensured that, in the event of failure of the first voltage supply U 1, the steering gear 3 receives a steering wheel angle φ L. Finally, it should be noted that the data connections 16, 17, 18 are much faster than the two vehicle buses 20, 23.FIG. 2 shows how the first supply voltage U1 is fed via a decoupling element 28 in the form of a diode to the microprocessor 15 of the angle-of-rotation sensor 5, wherein a buffer memory 29 in the form of a capacitor is additionally provided. The microprocessor 15 can therefore still continue to operate for a certain time even in the event of a short circuit or failure of the first voltage supply U 1.List of reference characters1 Steer-by-wire steering system 2 Steering column module 3 Steering gear 4 Steering wheel 5 Angle of rotation sensor 6 Torque sensor 7 Control device 8 Actuator 9 Actuator 10 Steering column 11 Microprocessor 12 Power electronics 13 Microprocessor 14 Power electronics 15 Microprocessor 16 Data connection 17 Data connection 18 Data line 19 Connection 20 Vehicle bus 21 Connection 22 Connection 23 Vehicle bus 24 Connection 25 Connection 26 Rotor 27 Toothed rack 28 Decoupling element 29 Buffer spoke φ L Steering wheel angle φ R Rotor position angle U1 Voltage supply U2 Voltage supply

Claims

Steer-by-wire steering system (1) comprising a steering column module (2) and a steering gear (3), wherein the steering column module (2) has at least one steering wheel (4), a steering column (10), at least one angle of rotation sensor (5), at least one actuator (8) for generating a counter-torque on the steering wheel (4) and at least one control unit (7) for actuating the actuator (8), wherein the control unit (7) has a microprocessor (11) and power electronics (12), wherein the control unit (7) is designed in such a way that a steering wheel angle (φ L) is determined on the basis of the data of a rotor position sensor of the actuator (8), wherein the microprocessor (11) for the actuator (8) transmits the steering wheel angle (φ L) to a first vehicle bus (20) and transmits the steering wheel angle (φ L) directly via a separate data line (18) to the steering gear (3), wherein the steering gear (3) is connected to the first vehicle bus (20), characterized in that a microprocessor (15) of the angle of rotation sensor (5) is arranged in the control unit (7), wherein the microprocessor (15) of the angle of rotation sensor (5) transmits the steering wheel angle (φ L) via a direct data connection (16) to the microprocessor (11) for the actuator (8) and transmits it to the first vehicle bus (20).Steer-by-wire steering system (1), characterized in that a second microprocessor (13) and a second power electronics (14) are arranged in the control unit (7), said second microprocessor controlling a second actuator (9) for generating a counter-torque, wherein the first microprocessor (11) and the second microprocessor (13) are connected in terms of data, wherein the second microprocessor (13) is designed in such a way as to transmit the steering wheel angle (φ L) to a second vehicle bus (23).Steer-by-wire steering system (1) according to Claim 1 or 2, characterized in that the first microprocessor (13) of the first actuator (8) is designed in such a way that it receives an index signal (I) over full revolutions of the steering wheel (4).Steer-by-wire steering system (1) according to Claim 2 or Claims 2 and 3, characterized in that the first actuator (8), the first microprocessor (11) for the first actuator (8) and the first power electronics (12) are connected to a first voltage supply (U1), and the second actuator (9), the second microprocessor (13) for the second actuator (9) and the second power electronics (14) are connected to a second voltage supply (U2).Steer-by-wire steering system (1) according to one of the preceding claims, characterized in that the microprocessor (15) for the angle-of-rotation sensor (5) is connected via a decoupling element (28) to the voltage supply (U1) of the first microprocessor (11) for the first actuator (8), wherein a buffer memory (29) is arranged between decoupling element (28) and microprocessor (15).Steer-by-wire steering system (1) according to one of the preceding claims, characterized in that the steering column module (2) has at least one torque sensor (6).Control device (7) for a steer-by-wire steering system (1), wherein the control device (7) has a microprocessor (11) and power electronics (12), wherein the control device (7) is designed in such a way that a steering wheel angle (φ L) is determined on the basis of the data of a rotor position sensor of the actuator (8), the microprocessor (11) for the actuator (8) has a connection (19) for a first vehicle bus (20), wherein the microprocessor (11) for the actuator (8) additionally has a connection for a direct data line (18) to a steering gear (3), characterized in that a microprocessor (15) of a rotation angle sensor (5) is arranged in the control device (7), wherein the microprocessor (15) of the angle of rotation sensor (5) transmits the steering wheel angle (φ L) via a direct data connection (16) to the microprocessor (11) for the actuator (8), and the microprocessor (15) for the angle of rotation sensor (5) has a connection (21) for the first vehicle bus (20).Method for operating a 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 at least one steering wheel (4), a steering column (10), at least one angle of rotation sensor (5), at least one actuator (8) for generating a counter torque on the steering wheel (4) and at least one control unit (7) for actuating the actuator (8), wherein the control unit (7) has a microprocessor (11) and power electronics (12), wherein the control unit (7) determines a steering wheel angle (φ L) on the basis of the data of a rotor position sensor of the actuator (8), wherein the microprocessor (11) for the actuator (8) transmits the steering wheel angle (φ L) to a first vehicle bus (20) and the microprocessor (11) for the actuator (8) transmits the steering wheel angle (φ L) directly via a separate data line (18) to the steering gear (3), wherein the steering gear (3) is connected to a first vehicle bus (20), characterized in that a microprocessor (15) of the rotational angle sensor (5) is arranged in the control unit (7), wherein the microprocessor (15) of the rotational angle sensor (5) transmits the steering wheel angle (φ L) to the microprocessor (11) of the actuator (8) via a direct data connection (16), wherein the microprocessor (15) of the angle of rotation sensor (5) transmits the steering wheel angle (φ L) to the first vehicle bus (20).

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