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

Abstract

The invention relates to a steering-by-wire system comprising a steering column module and a steering gear module, the steering gear module having a first and a second steering controller, a first and a second power electronics, and a first and a second electric actuator, the first steering controller, the power electronics and the electric actuator are supplied with electrical energy via a first voltage supply path, and the second steering controller, the power electronics and the electric actuator are supplied with electrical energy via a second voltage supply path, a support battery being arranged in the voltage supply paths, the steering column module has a force feedback actuator with an associated controller, and wherein the steering-by-wire system is configured to control the force feedback actuator when the first and second voltage supply paths fail so that only the support battery is available for electrical energy supply. The current gradient of the support battery is limited by a steering controller in the voltage supply path of the support battery and / or by a controller of the force feedback actuator, and a method.

Description

Technical Field

[0001] This invention relates to a steer-by-wire system and a method for operating the steer-by-wire system. Background Technology

[0002] A characteristic of steer-by-wire systems is the absence of mechanical penetration from the steering column module to the steering transmission module (or steering gear module, or Lenkgetriebe-Modul). The steering column module has steering actuation elements and at least one rotation angle or torque sensor, whose signals are electrically transmitted to the steering transmission module, where they are then converted, for example, into position and / or force at the rack or pushrod. Due to the lack of mechanical penetration, there are correspondingly high requirements for fail-safety. For this purpose, the steering transmission module has a first steering controller, a second steering controller, a first power electronics device, a second power electronics device, a first electric actuator, and a second electric actuator. The electric actuator is configured, for example, as an electric motor coupled to the rack or pushrod, wherein the rotational motion of the electric motor is converted into translational motion of the rack or pushrod to steer the wheels. Here, the first steering controller, the first power electronics device, and the first electric actuator are supplied with electrical energy through a first voltage supply path. Correspondingly, the second steering controller, the second power electronics device, and the second electric actuator are supplied with electrical energy through a second voltage supply path. The first and second voltage supply paths are independent of each other.

[0003] Such a voltage supply path is described, for example, in DE 10 2022 001 268 A1. A main battery, configured as a high-voltage battery, is provided here. Independent DC / DC converters are provided here, each applying the voltage of the high-voltage battery to its input. The DC / DC converters are configured as buck converters and convert the high-voltage voltage to a voltage suitable for a steering-by-wire system. A first DC / DC converter forms part of a first voltage supply path, while a second DC / DC converter forms part of a second voltage supply path. It is also suggested that a support battery be arranged in at least one voltage supply path.

[0004] The steering column module has at least one force feedback actuator with a corresponding controller. Preferably, the force feedback actuator with controller is also redundantly configured, wherein one or more force feedback actuators are used to generate a counter-torque at the steering input to provide the driver with the tactile feedback of conventional steering. Furthermore, the force feedback actuator is also used to return the steering input to the neutral position.

[0005] In an electronic vehicle electrical network as described in DE 10 2022 001 268 A1, voltage supply can therefore be achieved even if the high-voltage battery fails or both DC / DC converters fail. Summary of the Invention

[0006] This invention addresses the following technical problems, further improves the fail-safety of steer-by-wire systems, and provides a corresponding method for operating such steer-by-wire systems.

[0007] The solution to this technical problem is achieved through the steer-by-wire system according to the invention and the method according to the invention. Other advantageous designs of the invention are derived herein.

[0008] The steer-by-wire system includes a steering column module and a steering transmission module. The steering transmission module has a first steering controller, a first power electronics device, and a first electric actuator, all powered by a first voltage supply path. Furthermore, the steering transmission module also has a second steering controller, a second power electronics device, and a second electric actuator, all powered by a second voltage supply path. At least one support battery is arranged in at least one voltage supply path. Additionally, the steering column module has at least one force feedback actuator with a corresponding controller. The steer-by-wire system is configured such that when the first and second voltage supply paths fail, and only the support battery is available for power supply, the current gradient of the support battery is limited by the steering controller in the voltage supply path of the support battery and / or by the controller of the force feedback actuator. This prevents the voltage of the support battery from dropping below a threshold voltage that would cause the controller to shut off, thus preventing steering from becoming impossible. If the controller for the braking system is also connected to the voltage supply path, braking will also be impossible when the voltage drops. This is prevented by limiting the current gradient. This limitation is enforced even if another support battery or supercapacitor is arranged in another voltage supply path as a buffer.

[0009] In one embodiment, the steering controller is configured such that the associated electric actuator is operated with reduced dynamic control. For example, the electric actuator is operated such that the rack speed or pushrod speed and / or rack acceleration or pushrod acceleration is set below what is preset by input at the steering actuator.

[0010] The resulting short-term geometric offset between the steering wheel angle and the steering angle can be compensated by the steering transmission module with a certain time offset.

[0011] In another embodiment, the controller associated with the force feedback actuator is configured such that an increased reaction torque is generated at the steering actuation element of the steering column module. This increased reaction torque prevents rapid changes in rotational angle at the steering actuation element. Consequently, the steering transmission module receives a preset from the steering column module that does not require consideration of the high dynamics of the electric actuator, thereby indirectly limiting the current gradient through the steering actuation element.

[0012] Here, these two measures can also be implemented together. Alternatively, it can be configured to first apply an increased counter-torque at the steering actuator, wherein if this measure alone is insufficient, the steering controller additionally restricts the dynamics for the electric actuator in order to thereby reduce the current gradient supporting the battery.

[0013] In another embodiment, the steering column module has a first force feedback actuator, a second force feedback actuator, a first controller, and a second controller, wherein the first force feedback actuator and the first controller are connected to a first voltage supply path, and the second force feedback actuator and the second controller are connected to a second voltage supply path.

[0014] In another embodiment, the first voltage supply path has a first DC / DC converter, and the second voltage supply path has a second DC / DC converter, with both converters connected to a high-voltage battery on the input side. Here, the two DC / DC converters can be configured differently to reduce common failures due to the same fault. Alternatively, the two DC / DC converters can be configured identically and, for example, have two independent windings on a common core as secondary windings of a DC / DC converter with current isolation.

[0015] For the design of the methodology, please refer to the preceding explanation. Attached Figure Description

[0016] The present invention will now be described in detail with reference to preferred embodiments. The only accompanying drawing shows a schematic block diagram of a steer-by-wire system. Detailed Implementation

[0017] exist Figure 1 The diagram schematically illustrates a steer-by-wire system 1, which includes a steering column module 2 and a steering transmission module 3. The steering transmission module 3 has a first steering controller 4 and a second steering controller 5, which are data-connected to each other, indicated by bidirectional arrows. Furthermore, the steering transmission module 3 also has a first power electronics unit 6 and a second power electronics unit 7. Additionally, the steering transmission module 3 has a first electric actuator 8 and a second electric actuator 9. The first electric actuator 8 has a first stator winding 10, while the second electric actuator 9 has a second stator winding 11, both wound on a common stator. The two stator windings 10 and 11 perform work on a common rotor 12, whose rotor shaft 13 is coupled to a rack 14. The coupler could be, for example, a transmission.

[0018] The steering column module 2 has a steering actuation element 15 and a steering column 16, with at least one rotation angle sensor 17 arranged at the steering column. Furthermore, the steering column module 2 also has a first force feedback actuator 18 and a second force feedback actuator 19, as well as a first controller 20 and a second controller 21. The first controller 20 and the second controller 21 are data-connected, as indicated by a bidirectional arrow. The first controller 20 and the second controller 21 are data-technically connected to the rotation angle sensor 17. The steering column module 2 is redundantly data-technically connected to the steering transmission module 3 via two bus systems 22 and 23. Here, the first steering controller 4, the first power electronics 6, and the first electric actuator 8 are connected to a first voltage supply path U1, which has a first DC / DC converter 24 and a support battery 25. The support battery 25 has, for example, a rated voltage of 12V, 24V, or 48V. A high-voltage battery (not shown) is connected, for example, to the input side of the DC / DC converter 24. The first force feedback actuator 18 and the first controller 20 are also connected to the first voltage supply path U1. The second steering controller 5, the second power electronics 7, the second electric actuator 9, the second force feedback actuator 19, and the second controller 21 are connected to the second voltage supply path U2, which has a second DC / DC converter 26, which is connected on the input side, for example, to the same high-voltage battery as the first DC / DC converter 24.

[0019] In the event of a dual failure, such as when both DC / DC converters 24 and 26 fail or when the high-voltage battery fails, only the support battery 25 remains as the sole source of electrical power for emergency maneuvers. It is crucial to ensure that the voltage of the support battery 25 does not drop below the shutdown threshold for the first steering controller 4 due to an excessive current gradient. Various feasible methods exist for limiting the current gradient of the support battery 25. In a first embodiment, the first controller 20 detects that the second voltage supply path U2 is no longer available and that the first DC / DC converter 24 is no longer usable (e.g., via a status signal of the DC / DC converter 24 on the first bus system 22).

[0020] Then, the first controller 20 controls the first force feedback actuator 18 such that it generates an increased reaction torque at the steering element 15. While this increased reaction torque also requires energy from the supporting battery 25, this is not critical because the current is not very large. Due to the increased reaction torque, the driver can no longer generate a large rotational angular velocity at the steering element 15, thereby reducing the dynamic requirements on the first steering controller 4.

[0021] In one alternative embodiment, the first steering controller 4 is independent of the input limits at the steering actuator 15 for the dynamics of the first electric actuator 8. Empirically determined values ​​can be stored for this purpose, values ​​that must not be exceeded to prevent the voltage at the support battery 25 from dropping below a shutdown threshold. This short period results in asynchrony between the angular position of the steering actuator 15 and the wheel steering angle, but this is tolerable for safe emergency maneuvers. Specifically, the first steering controller 4 sets a smaller rack speed and rack acceleration than required by the driver via input at the steering actuator 15, but where the desired rack position is reached after a certain time. Alternatively, the first steering controller 4 can monitor parameters of the support battery 25 to match the dynamics. Finally, these two measures can be combined.

[0022] The first force feedback actuator 18 generates an increased counter torque at the steering actuator 15, preventing the driver from setting a high rotational angular velocity. This reduces the dynamic requirements of the first steering controller, thereby limiting the current gradient of the support battery 25. The steering angle set at the wheels by the steering transmission module 3 follows the driver's preset input at the steering actuator 15. If the driver subsequently makes a preset that would cause an excessive current gradient at the support battery 25, this preset is limited by the steering controller 4 to ensure the current gradient does not fall below a critical threshold. This ensures that the voltage of the support battery 25 does not drop below the shutdown threshold for the controller.

[0023] List of reference numerals 1. Steer-by-wire system 2 Steering column modules 3. Steering transmission mechanism module 4 First Steering Controller 5 Second Steering Controller 6 First Power Electronic Device 7 Second power electronic device 8 First electric actuator 9 Second electric actuator 10 First stator winding 11 Second stator winding 12 rotors 13 rotor shafts 14 racks 15 Steering Control Units 16-stroke steering column 17 Rotation Angle Sensor 18 First force feedback actuator 19 Second force feedback actuator 20 First Controller 21 Second Controller 22 First Bus System 23 Second Bus System 24 First DC / DC Converter 25 Support Battery 26 Second DC / DC Converter U1 First Voltage Supply Path U2 Second Voltage Supply Path.

Claims

1. A steer-by-wire steering system (1) comprising a steering column module (2) and a steering transmission module (3), wherein, The steering transmission module (3) has a first steering controller (4), a second steering controller (5), a first power electronics (6), a second power electronics (7), a first electric actuator (8) and a second electric actuator (9), wherein the first steering controller (4), the first power electronics (6) and the first electric actuator (8) are supplied with electrical energy by means of a first voltage supply path (Ul) and the second steering controller (5), the second power electronics (7) and the second electric actuator (9) are supplied with electrical energy by means of a second voltage supply path (U2), wherein at least one support battery (25) is arranged in at least one voltage supply path (Ul, U2), wherein the steering column module (2) has at least one force feedback actuator (18, 19) with an associated controller (20, 21), wherein the steer-by-wire system (1) is designed in such a way that, when the first voltage supply path (Ul) and the second voltage supply path (U2) fail, so that only the at least one support battery (25) can also provide for the electrical energy supply, the current gradient of the support battery (25) is limited by means of the steering controllers (4, 5) in the voltage supply path (Ul, U2) of the support battery (25) and / or by means of the controllers (20, 21) of the force feedback actuators (18, 19).

2. The steer-by-wire steering system of claim 1, wherein, The steering controllers (4, 5) are designed in such a way that the associated electric actuators (8, 9) are operated with reduced dynamics.

3. A steer-by-wire steering system according to claim 1 or 2, characterized in that The associated controllers (20, 21) of the force feedback actuators (18, 19) are designed in such a way that an increased counter torque is generated at the steering operating element (15) of the steering column module (2).

4. A steer-by-wire steering system according to any one of the preceding claims, characterized in that The steering column module (2) has a first force feedback actuator (18), a second force feedback actuator (19), a first controller (20) and a second controller (21), wherein the first force feedback actuator (18) and the first controller (20) are connected to the first voltage supply path (Ul) and the second force feedback actuator (19) and the second controller (21) are connected to the second voltage supply path (U2).

5. A steer-by-wire steering system according to any one of the preceding claims, characterized in that The first voltage supply path (Ul) has a first DC / DC converter (24) and the second voltage supply path (U2) has a second DC / DC converter (26), the first DC / DC converter and the second DC / DC converter being connected to a high-voltage battery on the input side.

6. A method for operating a steer-by-wire steering system (1) according to claim 1, characterized in that In the event of failure of the first voltage supply path (U1) and the second voltage supply path (U2), the current gradient of the support battery (25) is limited by a switchover controller (4, 5) in the voltage supply path (U1, U2) of the support battery (25) and / or by a controller (20, 21) of the force feedback actuator (18, 19) in such a way that only the at least one support battery (25) can also provide for the supply of electrical energy, so that an emergency maneuver can be carried out without the voltage of the support battery (25) falling below a critical shutdown threshold.

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