Method for operating a steering system of a vehicle, steering system, computer program product and storage medium

Abstract

The present invention relates to a method for operating a steering system (11) of a vehicle (10), wherein the steering system (11) has a steer-by-wire module (12) for a main steering operation of the vehicle (10) and a steer-by-brake module (13) for an auxiliary steering operation of the vehicle (10), the method comprising: monitoring a functional operation of the steer-by-wire module (12) during the main steering operation, detecting a fault indicator of a fault in the steer-by-wire module (12) during the main steering operation, and implementing at least one preparatory measure on the basis of the detected fault indicator for possibly carrying out the auxiliary steering operation by means of the steer-by-brake module (13). The invention further relates to a steering system (11) and to a computer program product (14) for carrying out the method, as well as to a computer-readable storage medium (15) on which a computer program product (14) according to the invention is stored.

Description

[0001] Description

[0002] Method for operating a steering system of a vehicle, steering system, computer program product and storage medium

[0003] The present invention relates to a method for operating a steering system of a vehicle with a steer-by-wire module. The invention further relates to a steering system and a computer program product for implementing such a method, as well as a storage medium on which such a computer program product is stored.

[0004] In the event of steering errors or steering failures in motor vehicles with steer-by-wire steering, a vehicle, and in particular the driver, can lose the ability to change the vehicle's position laterally and to influence it rotationally through yaw. Steer-by-wire systems nevertheless represent a promising system for the future for a variety of reasons. For example, steer-by-wire enables the steering wheel to be folded away and / or retracted during fully automated driving. This creates more space for the driver, who becomes a passenger during fully automated driving, to engage in activities such as sleeping, reading the newspaper, and surfing the internet. Folding and retracting the steering wheel also enables new interior concepts, such as those featuring rotating seats and fold-out tables.In addition, the mechanical decoupling between the steering wheel and the steering actuator prevents unintentional misoperation during fully automated driving. Even if the steering wheel is not folded away or retracted, accidental steering movement does not result in an unwanted vehicle reaction. Steer-by-wire also offers various advantages in conventional vehicles without automatic driving functions. Steer-by-wire can be used to implement stabilization functions such as crosswind stabilization or trailer stabilization, as the driver no longer perceives the steering intervention at the steering wheel. With an evasive steering assist system, the driver can be overridden in an emergency using steer-by-wire.

[0005] In steer-by-wire systems, the mechanical connection between the steering wheel, steering column module, and steering gear at the axle is broken and replaced by a redundant data line. The steering column, which can be rotated by the driver as a mechanical fallback, is eliminated. The overall system influencing lateral dynamics, usually the steering system in particular, must therefore meet certain safety and availability requirements. To meet these safety requirements, the steer-by-wire system must be designed with at least single redundancy according to the current state of the art and legal requirements. This is currently achieved by using double windings in the motor, a double control unit, a double electrical power supply, and double data communication.

[0006] In current steer-by-wire systems, double redundancy or a second fallback level is generally desirable. Double redundancy could be achieved, for example, through additional technology such as a triple-relay control unit or a triple-winding motor, as is already used in aircraft.

[0007] The object of the present invention is to improve the operational reliability of a steer-by-wire-based steering system and a method for operating such a steering system, particularly with regard to increased operational reliability. The above object is achieved by the patent claims. In particular, the above object is achieved by the method according to claim 1, the steering system according to claim 8, the computer program product according to claim 9, and the storage medium according to claim 10. Further advantages of the invention emerge from the subclaims, the description, and the figures.In this case, features that are described in connection with the method naturally also apply in connection with the steering system according to the invention, the computer program product according to the invention, the storage medium according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is and / or can always be made mutually.

[0008] According to a first aspect of the present invention, a method, in particular a computer-implemented method, for operating a steering system of a vehicle is proposed, wherein the steering system comprises a steer-by-wire module for a main steering operation of the vehicle and a steer-by-brake module for an auxiliary steering operation of the vehicle. The method comprises the following steps:

[0009] Monitoring a functional operation of the steer-by-wire module during the main steering operation, detecting a fault indicator for a fault in the steer-by-wire module during the main steering operation, and taking at least one preparatory measure based on the detected fault indicator for a possible implementation of the auxiliary steering operation by means of the steer-by-brake module.

[0010] Steer-by-brake systems and corresponding modules are generally known in the state of the art. To date, steer-by-brake has primarily been used for multi-axle commercial vehicles such as truck trailers to enable cornering of the truck trailer with reduced tire wear. Steer-by-brake is a particularly effective solution for commercial vehicles because vehicles with a positive steering roll radius can be steered efficiently by braking the inside wheels on the front axle. Passenger cars, on the other hand, can have both a negative and a positive steering roll radius depending on their design. With a negative steering roll radius, the steering actuation would compensate for the yaw moment from wheel-selective braking. Lateral guidance solely through wheel-selective braking on the front axle is therefore not always an effective approach to steering a passenger car.

[0011] Within the scope of the present invention, however, the specific benefit of the lateral guidance potential of a steer-by-brake module for a further fallback level in a steer-by-wire-based steering system has now been recognized. The method according to the invention has now been further developed such that, after the first error indicator has been detected, at least one specific preparatory measure is taken or carried out for the possibly necessary auxiliary steering operation in the second fallback level, i.e., still in a first fallback level. Compared to conventional steering operation, only limited steering interventions are possible with auxiliary steering operation using steer-by-brake, which is why these interventions have not previously been considered suitable for a second fallback level of auxiliary steering operation. Within the scope of the invention, however, it has now been discovered that a steer-by-brake steering process can be implemented relatively effectively with suitable preparatory measures.This means that with appropriate preparatory measures, it is possible to ensure sufficient controllability of the vehicle using the steer-by-brake module in the event of a fault and / or failure of the steer-by-wire module, for example, to prevent an accident. The method according to the invention can therefore easily and reliably ensure operational safety in steer-by-wire-based steering mode, or at least improve it compared to known systems.

[0012] Preparatory measures can be taken, in particular, to ensure that in the event of a steer-by-wire module failure, the driver and / or the vehicle only need to make the smallest possible steering movements to cope with the acutely dangerous situation. If the driver and / or the vehicle only need to make small steering angles, these can be effectively implemented by the steer-by-brake module. This way, the vehicle remains controllable in the second fallback level.

[0013] Auxiliary steering mode, which can be implemented particularly using the steer-by-brake module, can be understood as steering mode that is performed in addition to the main steering mode or instead of the main steering mode. If, for example, the steer-by-wire module is still partially usable, the steer-by-brake module can be used in a supporting capacity. If the steer-by-wire module has completely failed, so that the driver can no longer steer the vehicle using the steering wheel, for example, the steering mode can be completely taken over by the steer-by-brake module in the form of auxiliary or emergency steering mode. If controllable ferry operation is now established through suitable preparatory measures, an accident can be prevented in a simple and reliable manner.

[0014] An error indicator for an error can be understood as an error indicator for an error or a potential error. This means that the error indicator can be used to detect whether the steer-by-wire module has an error or malfunction, or whether there is a possibility that the steer-by-wire module has or will have an error. The error indicator can be detected using a suitable detection unit of the steering system and / or the vehicle. Such a detection unit can have sensors for detecting possible errors and / or a computing unit for calculating possible errors, in particular based on data determined by the sensors. The sensors can have temperature sensors, speed sensors, torque sensors, angle sensors, current sensors, voltage sensors, and / or pressure sensors.The computing unit can comprise a vehicle control unit or be configured as part of the vehicle control unit. The computing unit can be connected to the sensors via wired and / or wireless signals. Monitoring of the functional operation can be performed using a comparable monitoring unit of the steering system and / or the vehicle. The monitoring unit can therefore comprise suitable sensors and a suitable computing unit for performing the desired monitoring.

[0015] Taking at least one preparatory measure based on the detected error indicator can be understood to mean that, based on the detected error indicator, at least one specific preparatory measure or various specific preparatory measures can be taken to specifically enable or at least improve the execution of the auxiliary steering operation using the steer-by-brake module. This means that the preparatory measures can be taken taking into account the auxiliary steering operation that may be performed in order to subsequently execute the auxiliary steering operation as effectively as possible in the event of a second error or when the second fallback level occurs to avoid an accident.

[0016] If a second fault occurs, the process can be continued by detecting a further fault indicator for a further fault in the steer-by-wire module during the main steering mode. Based on the further fault indicator, the auxiliary steering mode is performed, particularly to protect the vehicle and / or its occupants. In this case, the auxiliary steering mode can also be performed in addition to the main steering mode or as an alternative to the main steering mode.

[0017] The steer-by-wire module and the steer-by-brake module can be understood as separate steering modules or steering systems, whereby it is possible that the two steering modules have at least some of the same functional components and / or use them in the steering system.

[0018] According to a further embodiment of the present invention, it is possible for the at least one preparatory measure to be taken in a method when the vehicle is cornering or is predictably about to corner. Accordingly, it is possible for the at least one preparatory measure to be taken only when active or impending cornering of the vehicle is detected. In this way, the method can be carried out in a particularly energy-efficient and component-friendly manner, since the at least one preparatory measure is taken only in a selected potentially hazardous situation or in a situation with a potentially higher hazard potential.If the vehicle is traveling on a straight road, perhaps at a relatively low speed, and there is no indication that a curve is imminent, it may not be necessary to constantly alert the steer-by-brake module just to gain milliseconds to prevent a potential accident in the extremely unlikely event of a total failure of the steer-by-wire module. To assess whether the vehicle is cornering or will predictably corner, the steering system and / or the vehicle may have suitable sensors and / or a suitable computing unit that can determine the current and future driving state and / or driving style of the vehicle, for example, based on a determinable route recognition and / or route prediction.Furthermore, it is possible for the at least one preparatory measure in a method according to the invention to comprise the creation of a driving condition according to which the vehicle may or should only drive in a defined inner lane area of ​​the curve. In other words, based on the detected error indicator, a driving condition can be created according to which the vehicle drives or should drive as far inside the curve as possible. The extent to which the vehicle drives, is driven, or should drive taking into account the created driving condition depends on the manner in which the vehicle is moved. For example, if the vehicle is autonomously driving, the vehicle can be driven or drive automatically in the desired inner lane area based on the created driving condition. In this case, the intervention of a human driver can be prevented or not possible at all.If the vehicle is driven by a human driver, the created driving condition can be displayed to the driver on a screen inside the vehicle, for example in the form of a driving instruction or a driving suggestion, so that the driver adheres to it as best as possible and takes the corner as far inside as possible, rather than too far to the outside. By creating the driving condition, a proactive reduction of steering requirements can be easily achieved in the event of a fault in the steer-by-wire module while cornering. If the vehicle is driving on the inside of the corner, there is a relatively large margin of maneuver to the outside of the corner in the event of a possible failure of the main steering system, meaning that a potential accident can be prevented even with a relatively small steering movement using the steer-by-brake module.

[0019] Furthermore, in a method according to the present invention, it is possible for the at least one preparatory measure to comprise the buildup of a braking force in the steer-by-brake module for the possible implementation of the auxiliary steering operation. The buildup of a braking force can be understood in particular as the precautionary and / or preparatory buildup of a braking force, in particular in the form of a braking pressure, in the steering system and / or in the vehicle, wherein the braking force or braking pressure is built up to actuate the vehicle's brakes with as little delay as possible or to implement the auxiliary steering operation with as little delay as possible by means of the steer-by-brake module. The buildup of braking force takes a certain amount of time in the vehicle.The method according to the invention can ensure that this time is as short as possible and / or is shortened, at least in certain driving situations in which the corresponding preparatory measure in the form of the precautionary build-up of braking force has been taken. In other words, dead times for initiating a steer-by-brake intervention can be shortened or minimized. The braking force can be built up by increasing the fluid pressure in a hydraulic braking system. To shorten dead times, it is also possible, for example in a steer-by-brake module for electromechanical brakes, to mechanically reduce the air gap between the brake and the vehicle's wheel as a preparatory measure.

[0020] In a method according to the invention, it is also possible for the at least one preparatory measure to comprise a reduction in the speed of the vehicle, the setting of a maximum possible top speed of the vehicle and / or the display of a recommended top speed of the vehicle in a manner perceptible to a driver of the vehicle. Small curve radii can be implemented better at low speeds than at high or higher speeds. This means that by reducing the speed, the lateral guidance potential in an auxiliary steering mode using a steer-by-brake module can be increased. The speed reduction can be initiated directly after the error indicator is detected, in particular if it is also detected that the vehicle is cornering or will foreseeably corner or will enter a corner shortly.The extent to which the at least one preparatory measure includes reducing the vehicle's speed, setting a maximum possible top speed for the vehicle, and / or displaying a recommended top speed for the vehicle in a manner perceptible to a driver of the vehicle depends on how the vehicle is being moved and / or what type of vehicle is being moved. For example, if the vehicle is autonomously driving and is currently being moved autonomously, a speed reduction can be carried out automatically, in particular depending on environmental conditions such as the course of the road and / or the current vehicle speed. In this case, changing the vehicle's speed by a human driver can be prevented or even made impossible.If the vehicle is driven by a human driver, a recommended maximum speed can be displayed on a screen inside the vehicle so that the driver adheres to it as much as possible and brakes the vehicle accordingly or does not accelerate above the recommended maximum speed.

[0021] Furthermore, in a method according to the present invention, it is possible for the at least one preparatory measure to comprise supplementing a main steering operation carried out by means of a steer-by-wire module with an auxiliary steering operation carried out by means of a steer-by-brake module. For example, the steer-by-wire module can be assisted in lane guidance even without any indication of a total failure of the steer-by-wire module or of the main steering operation on a vehicle axle, for example due to understeer interventions. For example, the steer-by-brake module can directly and without delay assist the steer-by-wire module in the event of any deviation from a trajectory specified by the driver when cornering. Another helpful feature is that in the event of a steering actuator failure, the steering system first has to "straighten itself out" without the actuator's actuating forces. As the steering is straightened out, the assistance from the steer-by-brake module can ramp up.A watchdog can be used to reduce the response time or dead time between the failure of the steer-by-wire module or the main steering mode and the intervention of the steer-by-brake module or the start of auxiliary steering mode. This allows initial steering assistance to be provided by the steer-by-brake module as soon as the first indications of a critical potential fault in the steer-by-wire module or the main steering mode are detected.

[0022] According to a further embodiment of the present invention, it is possible for the at least one preparatory measure to be taken depending on ambient conditions in the vicinity of the vehicle. For example, the preparatory measure can be taken depending on whether it is raining and the road is wet, whether it is snowing and the road may be covered with snow, and / or whether, for example, fog and thus correspondingly restricted visibility are detected. The ambient conditions can therefore be understood to include, in particular, weather conditions, lighting conditions, and / or road conditions. Taking the ambient conditions into account, the steer-by-brake module that may be used can be operated or used particularly effectively.

[0023] A further aspect of the invention relates to a steering system for a vehicle, comprising a steer-by-wire module for a main steering operation and a steer-by-brake module for an auxiliary steering operation, wherein the steering system is configured and designed to:

[0024] Monitoring the functional operation of the steer-by-wire module during main steering operation,

[0025] Detecting a fault indicator for a possible fault in the steer-by-wire module during main steering operation, and

[0026] Taking at least one preparatory measure based on the detected error indicator for the possible implementation of the auxiliary steering operation using the steer-by-brake module.

[0027] The steering system according to the invention thus provides the same advantages as those described in detail with reference to the method according to the invention. Furthermore, within the scope of the invention, a computer program product is proposed that includes instructions that cause the steering system described above to execute the method steps also described above and / or that the described method steps are executed in such a steering system. Furthermore, the invention relates to a computer-readable, in particular non-volatile, storage medium on which such a computer program product is stored.

[0028] The computer program product may be implemented as computer-readable instruction code in any suitable programming language and / or machine language, such as JAVA, C++, C#, and / or Python. The computer program product may be stored on a computer-readable storage medium, such as a data disk, a removable drive, volatile or non-volatile memory, or a built-in memory / processor. The instruction code may program a computer or other programmable device, such as a vehicle control unit, to perform the desired functions. Furthermore, the computer program product may be provided and / or be provided on a network, such as the Internet, from which it can be downloaded by a user as needed.The computer program product can be and / or be implemented by means of software as well as by means of one or more special electronic circuits, i.e. in hardware or in any hybrid form, i.e. by means of software components and hardware components.

[0029] Further measures improving the invention will become apparent from the following description of various exemplary embodiments of the invention, which are schematically illustrated in the figures. All features and / or advantages apparent from the claims, the description, or the figures, including structural details and spatial arrangements, may be essential to the invention both individually and in various combinations.

[0030] They show schematically:

[0031] Figure 1 shows a vehicle with a steering system according to an embodiment of the present invention,

[0032] Figure 2 shows a storage medium with a computer program product stored thereon according to an embodiment of the present invention, and Figure 3 shows a flowchart for explaining a method according to an embodiment of the present invention.

[0033] Fig. 1 schematically shows a vehicle 10 with a steering system 11, which has a steer-by-wire module 12 for main steering operation and a steer-by-brake module 13 for auxiliary steering operation. The steering system 11 further comprises a control unit 16, which is in signal communication with the steer-by-wire module 12 and the steer-by-brake module 13. The steering system 11 further comprises (not shown) a sensor system and an actuator system, by means of which the desired steering operation can be implemented. The steering system 11 is configured and designed to carry out the method steps described with reference to Fig. 3.

[0034] Fig. 2 shows a computer-readable and non-volatile storage medium 15 with a computer program product 14 stored thereon. The computer program product 14 includes instructions that cause the steering system 11 to execute the method steps described with reference to Fig. 3. The computer program product 14 shown in Fig. 2 could be installed in the control unit 16 shown in Fig. 1 to execute the method described below.

[0035] Fig. 3 shows a flowchart for explaining a method for operating the steering system 11 shown in Fig. 1. According to the method, in a step S1, the functional operation of the steer-by-wire module 12 is monitored during the main steering operation. In particular, it is determined using suitable sensors and / or computational steps whether there are any signs of errors or malfunctions in the steer-by-wire module 12. In step S2, an error indicator for an error in the steer-by-wire module 12 during the main steering operation is now determined. Furthermore, in step S2, it is detected using suitable sensors and computational steps whether the vehicle 10 is currently cornering or will predictably corner or will soon enter a corner.If a current or imminent cornering is detected, in a third step S3 selected preparatory measures are taken based on the detected error indicator in order to specifically prepare the vehicle for a possible imminent implementation of the auxiliary steering operation by means of the steer-by-brake module 13.

[0036] The preparatory measures can be taken differently depending on the current driving situation, for example, depending on the ambient conditions surrounding the vehicle 10. Furthermore, the preparatory measures can be taken depending on the type of vehicle 10 and also depending on the current driving style of the vehicle 10, for example, depending on the current vehicle speed and / or depending on whether the vehicle is being driven autonomously or by a human. For example, if the vehicle 10 is autonomously driving, different preparatory measures can be taken than in a vehicle 10 driven by a human driver.

[0037] Depending on the specific case, the preparatory measures may include creating a driving condition according to which the vehicle 10 may or should only drive in a defined inner lane area of ​​the curve. Furthermore, the preparatory measures may include building up a braking force in the steer-by-brake module 13 to potentially perform the auxiliary steering operation. Furthermore, the preparatory measures may include reducing the speed of the vehicle 10, setting a maximum possible top speed of the vehicle 10, and / or displaying a recommended top speed of the vehicle 10 in a manner perceptible to a driver of the vehicle 10. Furthermore, the preparatory measures may include supplementing a main steering operation performed by means of the steer-by-wire module 12 with an auxiliary steering operation performed by means of the steer-by-brake module 13.

[0038] In addition to the illustrated embodiments, the invention permits further design principles. This means that the invention should not be considered limited to the exemplary embodiments explained with reference to the figures. For example, if the lateral acceleration or steering effect corresponding to an originally set steering angle can no longer be realized by the steer-by-brake module 13, it is possible to achieve or implement the maximum possible lateral guidance of the vehicle 10 using the steer-by-brake module 13. At the same time, in this case, to minimize the severity of the accident, a maximum speed reduction is achieved or implemented using the steer-by-brake module 13.Depending on the axle concept of the vehicle 10, maximum lateral acceleration can be achieved with increased slip or locking of individual wheels, since the steering angles set with these wheels are no longer significant for vehicle control and only a deceleration force acts. Depending on the axle design, this can result in particularly high lateral acceleration. Reference symbols: Vehicle Steering system Steer-by-wire module Steer-by-brake module Computer program product Storage medium Control unit.

Claims

Patent claims Method for operating a steering system (11) of a vehicle (10), wherein the steering system (11) comprises a steer-by-wire module (12) for a main steering operation of the vehicle (10) and a steer-by-brake module (13) for an auxiliary steering operation of the vehicle (10), comprising: Monitoring a functional operation of the steer-by-wire module (12) during the main steering operation, Detecting a fault indicator for a fault in the steer-by-wire module (12) during main steering operation, and Taking at least one preparatory measure based on the detected error indicator for a possible implementation of the auxiliary steering operation by means of the steer-by-brake module (13). Method according to claim 1, characterized in that the at least one preparatory measure is taken when the vehicle (10) is negotiating a curve or is predictably about to negotiating a curve. Method according to claim 2, characterized in that the at least one preparatory measure comprises creating a driving condition according to which the vehicle (10) may or should only drive in a defined inner lane area of ​​the curve. Method according to one of the preceding claims, characterized in that the at least one preparatory measure comprises building up a braking force in the steer-by-brake module (13) for the possible implementation of the auxiliary steering operation.Method according to one of the preceding claims, characterized in that the at least one preparatory measure comprises a speed reduction of the vehicle (10), the setting of a maximum possible top speed of the. Vehicle (10) and / or the display of a recommended maximum speed of the vehicle (10) perceptible to a driver of the vehicle (10). Method according to one of the preceding claims, characterized in that the at least one preparatory measure comprises supplementing a main steering operation carried out by means of a steer-by-wire module (12) with an auxiliary steering operation carried out by means of a steer-by-brake module (13). Method according to one of the preceding claims, characterized in that the at least one preparatory measure is taken depending on ambient conditions in an environment of the vehicle (10). Steering system (11) for a vehicle (10), comprising a steer-by-wire module (12) for a main steering operation and a steer-by-brake module (13) for an auxiliary steering operation, wherein the steering system (11) is configured and designed to: Monitoring a functional operation of the steer-by-wire module (12) during the main steering operation, Detecting a fault indicator for a possible fault in the steer-by-wire module (12) during main steering operation, and Taking at least one preparatory measure based on the detected error indicator for potentially performing the auxiliary steering operation by means of the steer-by-brake module (13). A computer program product (14) comprising commands that cause the steering system (11) according to claim 8 to execute the method steps according to any one of claims 1 to 7. A computer-readable storage medium (15) having a computer program product (14) according to claim 9 stored thereon.

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