Degraded concept for steer-by-wire systems
By introducing a controller and evaluation device into the steering system, the system can switch to the appropriate operating mode in case of a fault, ensuring safe vehicle control and solving the safety control problem of the steer-by-wire system in case of a fault.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- THYSSENKRUPP PRESTA AG
- Filing Date
- 2020-04-20
- Publication Date
- 2026-08-04
AI Technical Summary
Existing steer-by-wire systems in motor vehicles and steering systems in autonomous vehicles are difficult to maintain safe control when malfunctions occur, leading to an increased risk of safety emergencies.
Design a steering system controller with a normal operating mode and at least two degraded modes. Evaluate the performance degradation status through an evaluation device and switch to the appropriate operating mode based on the evaluation results to ensure that the system can still safely control the vehicle trajectory in the event of a fault.
Even when the steering system performance is impaired, the driver or vehicle can still control the vehicle's trajectory in a safe manner, avoiding any safety emergencies.
Smart Images
Figure CN115667050B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a steer-by-wire system for motor vehicles or a steering system for autonomous motor vehicles as described in the preamble of claim 1. Background Technology
[0002] In motor vehicles with electromechanical steering systems, degradation is possible and permitted. For safety-critical steering systems and / or steer-by-wire systems in autonomous vehicles, the requirements and structure differ. One key requirement is that the steering system must be fault-tolerant, meaning that if a failure occurs, the steering system must continue to operate to provide its primary functions. Summary of the Invention
[0003] The purpose of this invention is to provide a steer-by-wire system for motor vehicles or a steering system for autonomous motor vehicles, wherein the steering system can control the vehicle's trajectory even after a degrade, thereby avoiding safety emergencies.
[0004] This objective is achieved by a steer-by-wire system for motor vehicles or a steering system for autonomous motor vehicles having the features of claim 1.
[0005] Therefore, a steer-by-wire system for a motor vehicle or a steering system for an autonomous motor vehicle is provided, the steering system having a controller, wherein the controller controls the steering of steerable wheels based on input from a driver or an autonomous driving unit, and wherein the controller has a normal operating mode with full steering functionality and no quality issues. Furthermore, the controller has at least two degradation modes for degraded operation of the steering system, wherein the steering system includes an evaluation device that evaluates the performance degradation state of the steering system and sets the operating mode of the controller based on the evaluation results.
[0006] Essentially, this degradation concept can be applied to steering systems where the existence of the system's operation is critical to safety. Preferably, the steering system is fault-tolerant. If the system is not fault-tolerant, but the probability of the first failure is acceptablely low, this concept can also be applied to that type of steering system.
[0007] Even after the steering system experiences some performance degradation, the driver or the vehicle itself can still safely control its trajectory. Therefore, dangerous situations can be avoided.
[0008] Preferably, the operating mode is defined by a range limited by the performance limits of the steering system. An example of range selection is given below.
[0009] In a preferred embodiment, the normal operating mode is located between 100% of the available performance of the steering system and a first lower limit, wherein the first lower limit is located between 90% and 99% of the available performance of the steering system, preferably around 95% of the available performance of the steering system.
[0010] Preferably, the first degradation mode of at least two degradation modes lies within a range between a first upper limit and a second lower limit, wherein the first upper limit lies between 90% and 99% of the steering system's availability, and the second lower limit lies between 60% and 90% of the steering system's availability. Advantageously, the first upper limit is 95% of the steering system's availability and / or the second lower limit is 70% of the steering system's availability.
[0011] The first downgrade mode preferably provides full steering functionality. Quality issues may arise.
[0012] Furthermore, preferably, if the second degradation mode of at least two degradation modes is located between a second upper limit and a third lower limit, wherein the second upper limit is located between 60% and 90% of the available performance of the steering system, and the third lower limit is located between 30% and 70% of the available performance of the steering system.
[0013] Preferably, the second upper limit is 70% of the available performance of the steering system and / or the third lower limit is 50% of the available performance of the steering system.
[0014] The second downgraded mode preferably provides full steering functionality, wherein the controller of the steering system provides a speed limit to the vehicle drive controller, wherein the speed limit is within a preset range.
[0015] In addition, there may be a third degradation mode among the last two degradation modes, which is preferably located in the range between the third upper limit and the zero availability of the steering system, wherein the third upper limit is located in the range between 30% and 70% of the availability of the steering system, particularly around 50% of the availability of the steering system.
[0016] The third downgrade mode preferably does not provide steering functionality, wherein the controller of the steering system provides a speed limit to the vehicle drive controller, wherein the speed limit is within a preset range.
[0017] The degradation concept may only include the three modes mentioned above. However, it is advantageous if the controller has a total of four operating modes, and the first lower limit equals the first upper limit, the second lower limit equals the second upper limit, and the third lower limit equals the third upper limit.
[0018] Preferably, the controller of the steering system is designed to send its status to an information output unit that notifies the driver to perform a downgrade operation. The notification can be specific to each downgrade mode. The information output unit preferably controls at least one notification device, which can be a vehicle display, vehicle speaker, or steering mechanism. The notification device can provide notification through vibration, or by modifying the virtual gear ratio of the steer-by-wire system, increasing the feedback from the steer-by-wire system's feedback actuator, or reducing the assistance force in the EPAS system. It is also possible to use more than one notification device to notify the driver of the steering system downgrade.
[0019] Furthermore, a method is provided for controlling a steer-by-wire system of a motor vehicle or a steering system of an autonomous motor vehicle, wherein the steering system has the aforementioned controller, the controller controlling the steering of the steerable wheels according to input from a driver or an autonomous driving unit, wherein the controller has a normal operating mode with complete steering function and no quality problems, and wherein the controller has at least two degraded operating modes for the degraded operation of the steering system, wherein the method includes the following method steps:
[0020] The performance degradation status of the steering system is assessed through evaluation.
[0021] Based on the evaluation results, set the controller to normal mode or at least one of two degraded modes.
[0022] Preferably, at least two degradation modes include one degradation mode in which the performance of the steering system is sufficient to perform all steering maneuvers, and a degradation mode in which the performance of the steering system is too low to perform steering maneuvers, and a speed limit is applied.
[0023] The operating mode is preferably defined by the range limited by the performance limits of the steering system. The characteristics of the limits and the operating mode are as described above. Attached Figure Description
[0024] Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:
[0025] Figure 1 This is a schematic diagram of the electromechanical steering system; and
[0026] Figure 2This is a performance degradation diagram of the steering system. Detailed Implementation
[0027] Figure 1 A schematic diagram of an electromechanical power steering mechanism 1 is shown. A steering shaft 2 is connected to a steering wheel 3 for driver operation. The steering shaft 2 is coupled to a steering rack 4 via a pinion 5. A steering rack 6 is connected to the steering rack 4 and the steering wheels 7 of the vehicle. Rotation of the steering shaft 2 causes axial displacement of the steering rack 4 via the pinion 5, which is connected to the steering shaft 2 in an anti-torsion manner. Assist force is applied to the steering mechanism via a drive motor. The electromechanical power steering mechanism 1 can be of the column-assisted, rack-assisted, or pinion-assisted type. A column-assisted EPAS (electric power steering) system has a motor connected to the steering column 2. A rack-assisted EPAS system has a motor connected to the steering rack 4. A pinion-assisted EPAS system has a motor connected to the pinion 5. Figure 1 All three types of assistance are shown, of which typically only one is implemented. EPAS systems are part of road vehicles with automatic steering. The vehicle can be fully autonomous or offer an automatic mode, such as for parking or long-distance travel. Such EPAS systems must have a high level of safety measures and are therefore safety-critical.
[0028] Safety-critical steering systems also include steer-by-wire systems, in which there is no mechanical connection between the steering wheel and the steerable wheels. Furthermore, there must be no mechanical coupling between the steerable wheels themselves for synchronized steering.
[0029] These safety-critical steering systems all include a controller with four operating modes: a normal mode (AB) and three degraded modes (BC, CD, DE). An evaluation device assesses the performance degradation state of the steering system. Based on the evaluation results, the controller's operating mode is set.
[0030] Figure 2 The controller of the safety-critical steering system is shown to operate in four modes (AB, BC, CD, DE) in terms of the availability performance of the steering system.
[0031] A, B, C, D, and E represent the limits of available performance. AB, BC, CD, and DE represent various operating modes, each defined by a portion between the performance limits.
[0032] Operating modes AB represent the normal mode. The steering system offers very high availability, allowing for all driving maneuvers without restriction. A represents 100% availability, while B falls between 90% and 99% availability, preferably at 95%.
[0033] Operating mode BC is the first degraded mode with degraded operation; all driving maneuvers are possible, but a quality issue may occur, namely, the driver can feel a slight delay in vehicle movement compared to steering wheel movement, which is not a safety issue. C is located in the range of 60% to 90% of available performance, preferably 70%.
[0034] An information output unit is used to notify the driver to perform a downgrade operation. The information output unit controls at least one notification device. This notification device may represent, for example, a vehicle display or a speaker. The steering wheel can also be used to provide feedback, for example, through vibration, by modifying the virtual gear ratio of the steer-by-wire system, or by increasing the feedback actuator of the steer-by-wire system. The aforementioned notification devices can also be combined with each other.
[0035] As a result, the driver will be alerted by the notification device and can then decide to stop immediately and call a tow truck or drive to the workshop to resolve the issue.
[0036] Operating mode CD is a second degraded mode with degraded operation; all driving maneuvers are possible, but quality issues may occur. D is located between 30% and 70% of the steering system's available performance. To maintain full vehicle controllability, the vehicle is forced to operate within a predetermined speed range with speed limits.
[0037] Such moderate vehicle speeds allow for preparation for further degradation of the steering system, such as the loss of wheel actuator functionality.
[0038] As described above, feedback is provided to the driver to inform the steering system of the degraded operating mode.
[0039] The fourth operating mode, DE, is the third degraded mode operating as an emergency mode. E equals zero availability. Steering function is lost because performance is too low to provide steering capability. The vehicle is forced to travel within a predetermined speed range, the speed limit of which allows for safe stopping without steering. Further, the system can provide information about the degraded state related to the system, and external actuators at the vehicle level (such as the drivetrain and / or brakes) can assist in controlling the vehicle's lateral movement.
[0040] Provide feedback to the driver to notify the steering system of the emergency mode. This feedback can be provided as described above.
[0041] The concepts of the described operating modes can be applied to all steering systems where system operation is critical to safety. Fault tolerance is not required for these operations. This concept can also be used if the system is not fault-tolerant, but the probability of the first failure is very low and acceptable from a safety perspective.
Claims
1. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle (1), the steering system having a controller that controls the steering of steerable wheels based on input from a driver or an automated driving unit, wherein, The controller is provided with a normal operating mode (AB) with complete steering function and no quality problems. The controller is characterized in that it has at least two degradation modes (BC, CD, DE) for the degradation operation of the steering system. The steering system includes an evaluation device that evaluates the performance degradation state of the steering system and sets the operating mode of the controller according to the evaluation results. The at least two degraded modes (BC, CD, DE) include: a degraded mode in which the performance of the steering system is sufficient to complete all steering maneuvers, and a degraded mode in which the performance of the steering system is too low to complete steering maneuvers, and a speed limit is applied.
2. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 1, characterized in that, The operating modes (AB, BC, CD, DE) are defined by the range of limits imposed by the performance limits of the steering system.
3. The steer-by-wire system for a motor vehicle or the steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The normal operating mode (AB) is located between 100% of the available performance of the steering system and a first lower limit (B), wherein the first lower limit is located between 90% and 99% of the available performance of the steering system.
4. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 3, characterized in that, The first lower limit (B) is 95% of the available performance of the steering system.
5. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The first degradation mode (BC) of the at least two degradation modes is located between a first upper limit (B) and a second lower limit (C), wherein the first upper limit (B) is located between 90% and 99% of the available performance of the steering system, and the second lower limit (C) is located between 60% and 90% of the available performance of the steering system.
6. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 5, characterized in that, The first upper limit (B) is 95% of the available performance of the steering system and / or the second lower limit (C) is 70% of the available performance of the steering system.
7. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 5 or 6, characterized in that, The first downgrade mode (BC) provides full steering functionality.
8. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The second degradation mode (CD) of the at least two degradation modes is located between the second upper limit (C) and the third lower limit (D), wherein the second upper limit (C) is located between 60% and 90% of the available performance of the steering system, and the third lower limit (D) is located between 30% and 70% of the available performance of the steering system.
9. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 8, characterized in that, The second upper limit (C) is 70% of the available performance of the steering system and / or the third lower limit (D) is 50% of the available performance of the steering system.
10. The steer-by-wire system for a motor vehicle or the steering system for an automated motor vehicle according to claim 8 or 9, characterized in that, The second degraded mode (CD) provides full steering functionality, wherein the steering system controller provides speed limits to the vehicle drive controller.
11. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The third degradation mode (DE) of the last two degradation modes is located between the third upper limit (D) and the zero availability of the steering system, wherein the third upper limit (D) is located between 30% and 70% of the availability of the steering system.
12. The steer-by-wire system for motor vehicles or the steering system for automated motor vehicles according to claim 11, characterized in that, The third upper limit (D) is 50% of the available performance of the steering system.
13. The steer-by-wire system for a motor vehicle or the steering system for an automated motor vehicle according to claim 11 or 12, characterized in that, The third degraded mode (DE) cannot provide sufficient performance for the steering function, wherein the steering system controller provides a speed limit to the vehicle drive controller.
14. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The controller has a total of four operating modes (AB, BC, CD, DE), and the first lower limit (B) is equal to the first upper limit (B), the second lower limit (C) is equal to the second upper limit (C), and the third lower limit (D) is equal to the third upper limit (D).
15. A steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle according to any one of the preceding claims, characterized in that, The controller of the steering system is designed to send its status to an information output unit that can notify the driver to perform a downgrade operation.
16. The steer-by-wire system for a motor vehicle or the steering system for an automated motor vehicle according to claim 15, characterized in that, The information output unit controls at least one notification device, wherein the notification device is a vehicle display, a vehicle speaker, or a steering device, and the notification device is capable of vibration to notify, or can be implemented by modifying the virtual gear ratio of the steer-by-wire system or by increasing the feedback given by the feedback actuator of the steer-by-wire system.
17. A method for controlling a steer-by-wire system for a motor vehicle or a steering system for an automated motor vehicle (1), wherein, The steering system has a controller that controls the steering of the steerable wheels based on input from the driver or an automatic driving unit. The controller has a normal operating mode (AB) with complete steering functionality and no quality issues. The system is characterized by having at least two degraded operation modes (BC, CD, DE) for the degraded operation of the steering system. The method includes the following steps: The performance degradation status of the steering system is assessed through evaluation. Based on the evaluation results, the controller is set to normal mode (AB) or one of the at least two degraded modes (BC, CD, DE); The first degradation mode (BC) of the at least two degradation modes is located between a first upper limit (B) and a second lower limit (C), wherein the first upper limit (B) is located between 90% and 99% of the available performance of the steering system, and the second lower limit (C) is located between 60% and 90% of the available performance of the steering system. The method includes the following steps: The controller is set to the first degraded mode (BC), and the controller provides full steering functionality.
18. The method according to claim 17, characterized in that, The operating modes (AB, BC, CD, DE) are defined by the range of limits imposed by the performance limits of the steering system.
19. The method according to claim 17 or 18, characterized in that, The normal operating mode (AB) is located between 100% of the available performance of the steering system and a first lower limit (B), which is located between 90% and 99% of the available performance of the steering system.
20. The method according to claim 19, characterized in that, The first lower limit (B) is 95% of the available performance of the steering system.
21. The method according to claim 17, characterized in that, The first upper limit (B) is 95% of the available performance of the steering system and / or the second lower limit (C) is 70% of the available performance of the steering system.
22. The method according to any one of claims 17 to 21, characterized in that, The second degradation mode (CD) of at least two degradation modes is located between the second upper limit (C) and the third lower limit (D), wherein the second upper limit (C) is located between 60% and 90% of the available performance of the steering system, and the third lower limit (D) is located between 30% and 70% of the available performance of the steering system.
23. The method according to claim 22, characterized in that, The second upper limit (C) is 70% of the available performance of the steering system, and / or the third lower limit (D) is 50% of the available performance of the steering system.
24. The method according to claim 22 or 23, characterized in that, The method includes the following steps: The controller is set to the second degraded mode (CD), whereby the controller provides full steering functionality and the controller of the steering system provides a speed limit to the vehicle drive controller, wherein the speed limit is within the range of 40 km / h and 130 km / h.
25. The method according to any one of claims 17 to 24, characterized in that, The third degradation mode (DE) of the last two degradation modes is located between the third upper limit (D) and the zero availability of the steering system, wherein the third upper limit (D) is located between 30% and 70% of the availability of the steering system.
26. The method according to claim 25, characterized in that, The third upper limit (D) is 50% of the available performance of the steering system.
27. The method according to claim 25 or 26, characterized in that, The method includes the following steps: The controller is set to the third degraded mode (DE), in which the steering system controller provides insufficient steering performance and speed limits to the vehicle drive controller.
28. The method according to any one of claims 17 to 27, characterized in that, The controller has a total of four operating modes (AB, BC, CD, DE), and the first lower limit (B) is equal to the first upper limit (B), the second lower limit (C) is equal to the second upper limit (C), and the third lower limit (D) is equal to the third upper limit (D).