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

Abstract

The invention relates to a method for operating a steering system (11) of a vehicle (10), the steering system (11) comprising a steering-by-wire module (12) for a main steering operation of the vehicle (10) and a braking steering module (13) for an auxiliary steering operation of the vehicle (10), comprising: monitoring a functional operation of the steering-by-wire module (12) during the main steering operation, an error indicator for an error in the steer-by-wire module (12) is identified during the main steering operation, and-at least one preparation measure is taken in dependence on the identified error indicator for possibly performing the auxiliary steering operation by means of the brake steering module (13). The invention also relates to a steering system (11) and to a computer program product (14) for carrying out the method and to a computer-readable storage medium (15) in which a computer program product (14) according to the invention is stored.

Description

[0001] The present invention relates to a method for operating a steering system of a vehicle having a steer-by-wire module. The present invention also relates to a steering system, a computer program product for executing the method, and a storage medium having the computer program product stored thereon.

[0002] In the event of a steering fault and a steering failure in a motor vehicle with steer-by-wire, the vehicle and in particular the driver may lose the ability to change the lateral translation and to influence the vehicle position by means of a rotational skidding movement. However, for various reasons, steer-by-wire systems are promising systems for the future. Steer-by-wire enables, for example, the folding and / or retraction of the steering wheel during fully automated driving. This creates more room for movement for the driver, who becomes a passenger during fully automated driving, for example to sleep, read a newspaper, and surf the Internet. Similarly, new interior space concepts are enabled by folding and retracting the steering wheel, for example with rotatable seats and foldable tables. In addition, the mechanical decoupling between the steering wheel and the steering actuator avoids unwanted misoperations during fully automated driving. Even if the steering wheel is not folded or retracted, an accidental deflection of the steering wheel does not result in an unwanted vehicle reaction. In conventional vehicles without an automated driving function, steer-by-wire also offers various advantages. For example, stabilization functions such as crosswind stabilization or trailer stabilization can be achieved by steer-by-wire, since the driver no longer perceives steering interventions at the steering wheel. In avoidance assistance, the driver can be overridden by steer-by-wire in an emergency.

[0003] In a steer-by-wire system, the mechanical connection between the steering wheel, the steering column module, and the steering gearing on the axle is interrupted and replaced by redundant data lines. The steering column twisted by the driver as a mechanical fallback level is dispensed with. Therefore, the overall system influencing the lateral dynamics (usually in particular the steering system) must meet certain safety and usability requirements. To meet these safety requirements, according to the prior art and legal regulations, a steer-by-wire system must be designed to be at least single redundant. Currently, this is achieved by means of double windings in the motor, dual standby control devices, dual power supplies, and dual data communication.

[0004] In current steer-by-wire systems, basically a dual redundancy or a second fallback level is desirable. Dual redundancy can be achieved, for example, by additional technologies such as triple standby control devices or triple-wound motors (as already used in aircraft).

[0005] The technical problem to be solved by the present invention is to improve the running safety of a steering system based on steer-by-wire, and to improve a method for operating such a steering system, especially in terms of higher running safety. The above technical problem is solved by the claims. In particular, the above technical problem is solved 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. Other advantages of the present invention can be derived from the dependent claims, the description and the drawings. The features described herein in connection with the method are of course also applicable to 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. Therefore, the disclosure of the various aspects of the invention can always be cross-referenced to each other.

[0006] According to a first aspect of the present invention, a method, especially a computer-implemented method, is proposed for operating a steering system of a vehicle, wherein the steering system includes a steer-by-wire module for the main steering operation of the vehicle and a Steer-by-Brake module for the auxiliary steering operation of the vehicle. The method has the following steps:

[0007] - Monitoring the functional operation of the steer-by-wire module during the main steering operation,

[0008] - Identifying an error indicator for an error in the steer-by-wire module during the main steering operation, and

[0009] - Taking at least one preparatory measure based on the identified error indicator for a possible execution of the auxiliary steering operation by the Steer-by-Brake module.

[0010] The Steer-by-Brake system or the corresponding module is basically known in the prior art. Steer-by-Brake has hitherto been used especially for multi-axle commercial vehicles, such as truck trailers, to achieve a curved driving of the truck trailer with lower tire wear. For commercial vehicles, Steer-by-Brake is an effective solution because a vehicle with a positive steering roll radius can be steered efficiently by braking the wheels on the inner side of the curve on the front axle. In contrast, a passenger car can have a negative or positive steering roll radius according to its design. In the case of a negative steering roll radius, the steering drive compensates for the side-slip moment from the selective braking of the wheels. Therefore, the lateral guidance only by the selective braking of the wheels on the front axle is not always an effective method for steering a passenger car.

[0011] However, within the framework of the present invention, it has now been recognized that the lateral guiding potential of the brake-steering module has a special use for an additional fallback level in a steer-by-wire based steering system. The method according to the present invention is now further improved by taking or performing at least one defined preparatory measure (i.e., still within the first fallback level) after identifying a first error indicator, for an auxiliary steering operation that may be required in the second fallback level. Compared to a conventional steering operation, the auxiliary steering operation by brake-steering can only achieve limited steering intervention, and it has thus been considered unsuitable for the second fallback level of the auxiliary steering operation so far. However, within the framework of the invention, it has now been found that the brake-steering operation can be achieved relatively effectively through appropriate preparatory measures. That is to say, through appropriate preparatory measures, sufficient vehicle controllability can be ensured through the brake-steering module in the event of a steer-by-wire module failure and / or malfunction, for example, to avoid accidents. Through the method according to the present invention, the operating safety in a steer-by-wire based steering operation can thus be reliably ensured or at least improved compared to known systems in a simple manner. The preparatory measures can be carried out in particular such that the driver and / or the vehicle only need to make as small a steering movement as possible in the event of a steer-by-wire module failure to master an emergency dangerous situation. If the driver and / or the vehicle only need to set a small steering angle, this can be effectively mapped by the brake-steering module. The vehicle thus remains controllable in the second fallback level.

[0012] The auxiliary steering operation that can be performed particularly by the brake-steering module can be understood as a steering operation that is carried out additionally or alternatively to the main steering operation. For example, if the steer-by-wire module is still partially available, the brake-steering module can be used for assistance. If the steer-by-wire module fails completely, for example, the driver can no longer steer the vehicle through the steering wheel, the steering operation can be completely taken over by the brake-steering module in the form of an auxiliary or emergency steering operation. If a controllable driving operation is now initiated through appropriate preparatory measures, accidents can be prevented in a simple and reliable manner at the same time.

[0013] An error indicator for an error can be understood as an error indicator for an error or a possible error. That is to say, whether there is an error or a functional failure in the steer-by-wire module can be identified through the error indicator, or whether there is a possibility that the steer-by-wire module has or still has an error. The identification of the error indicator can be performed by a suitable identification unit of the steering system and / or the vehicle. Such an identification unit can have a sensing device for identifying possible errors and / or a calculation unit for calculating possible errors especially based on the data determined by the sensing device. The sensing device can have a temperature sensor, a rotational speed sensor, a torque sensor, an angle sensor, a current sensor, a voltage sensor, and / or a pressure sensor. The calculation unit can be or be part of a vehicle control device. The calculation unit can be in a wired and / or wireless signal connection with the sensors. The monitoring of the functional operation can be carried out by a similar monitoring unit of the steering system and / or the vehicle. The monitoring unit can thus have a suitable sensing device and a suitable calculation unit to perform the desired monitoring.

[0014] Taking at least one preparatory measure based on the identified error indicator can be understood as that, based on the identified error indicator, at least one specific preparatory measure or different specific preparatory measures can be taken to specifically achieve or at least improve the execution of the assisted steering operation by the brake steer module. That is to say, the preparatory measures can be taken considering the possible assisted steering operation to be performed, so that the assisted steering operation can be executed as effectively as possible to avoid accidents when entering the second failure situation or the second backup level.

[0015] If a second failure situation occurs, the method can continue to execute, that is, during the main steering operation, another error indicator for another error in the steer-by-wire module is identified, and the assisted steering operation is executed based on this other error indicator especially to protect the vehicle and / or the vehicle occupants. The assisted steering operation can be carried out additionally or alternatively with respect to the main steering operation in this case.

[0016] The steer-by-wire module and the brake steer module can be understood as independent steering modules or steering systems, and it is feasible that the two steering modules have at least partially the same functional components and / or are used in the steering system.

[0017] According to another embodiment of the present invention, it is feasible that, in this method, at least one preparatory measure is taken when the vehicle is driving or expected to drive on a curve. Thus, it is feasible that at least one preparatory measure is taken only when an enabled or upcoming curve driving of the vehicle is recognized. The method can thus be carried out in a particularly energy-efficient and component-protecting manner, because at least one preparatory measure is taken only in selected potential dangerous situations or in situations with a relatively high tendency of danger. If the vehicle is driving on a straight road, it may additionally have a relatively low speed, and it is not possible to recognize that it will face a curve driving within a foreseeable time, then it may not be necessary to always put the brake steering module on alert preparation, but only to obtain a few milliseconds in the extremely unlikely case of a complete failure of the steer-by-wire module to prevent a possible accident. In order to evaluate whether the vehicle is driving or can be foreseen to drive on a curve, the steering system and / or the vehicle may have suitable sensing devices and / or suitable computing units, which can determine the current and future driving states and / or driving manners of the vehicle, for example based on the determinable route recognition and / or route prediction.

[0018] Furthermore, it is feasible that, in the method according to the present invention, at least one preparatory measure includes establishing a driving condition according to which the vehicle is allowed or should drive only within a defined inner lane area of the curve. In other words, according to the recognized error indicator, a driving condition can be established according to which the vehicle drives or should drive as far inside the curve as possible. To what extent the vehicle drives, is driven or should drive considering the established driving condition depends on how the vehicle moves. For example, if it concerns an autonomous vehicle, the vehicle can be automatically driven or driven within the desired inner lane area according to the established driving condition. In this case, it is possible to prevent the intervention of a human driver or there may be no possibility of a human driver intervening at all. If the vehicle is driven by a human driver, the established driving condition can be displayed to him, for example in the form of a driving instruction or a driving suggestion on a screen inside the vehicle, so that the driver complies as much as possible and does not drive too far outwards but drives as far as possible inside the curve. By establishing the driving condition, it is possible to proactively reduce the steering demand in a simple manner for possible failure situations in the steer-by-wire module during curve driving. If the vehicle is driving in the inner area of the curve, there is a relatively large range to the outer area of the curve in the event of a possible failure of the main steering operation, so that even a relatively small steering movement by the brake steering module can prevent a possible accident.

[0019] Furthermore, in the method according to the invention, it is feasible that at least one preparatory measure includes establishing braking force in the brake steering module for a possible execution of an assisted steering operation. Establishing braking force can in particular be understood as prophylactically and / or preparatorily establishing braking force in the steering system and / or the vehicle, in particular in the form of brake pressure, wherein the braking force or the brake pressure is established to actuate the vehicle brakes as delay-free as possible or to execute the assisted steering operation as delay-free as possible by means of the brake steering module. The braking force has to be established at a determined time in the vehicle. By means of the method according to the invention, it can be achieved that at least in the determined driving situations in which the corresponding preparatory measure in the form of prophylactically established braking force has been taken, this time is as short as possible and / or is shortened. In other words, the dead time for initiating a brake steering intervention can be shortened or minimized. The braking force can be established by increasing the fluid pressure in a hydraulic braking system. It is also feasible to shorten the dead time by, for example, mechanically reducing the air gap between the brake and the vehicle wheel in a brake steering module for electromechanical brakes as a preparatory measure.

[0020] It is also feasible in the method according to the invention that at least one preparatory measure includes a reduction in the speed of the vehicle, a setting of the maximum possible top speed of the vehicle and / or a perceptible display for the driver of the vehicle of the recommended top speed of the vehicle. Smaller corner radii can be achieved better at lower speeds than at higher or very high speeds. That is to say, by reducing the speed, the lateral guiding potential in the assisted steering operation by means of the brake steering module can be increased. The speed reduction can be initiated directly after recognition of an error indicator, in particular if it is additionally recognized that the vehicle is driving in a bend or can be foreseen to be driving in a bend or is about to enter a bend. To what extent at least one preparatory measure includes a reduction in the speed of the vehicle, a setting of the maximum possible top speed of the vehicle and / or a perceptible display for the driver of the vehicle of the recommended top speed of the vehicle depends on how the vehicle is moving and / or what type of vehicle is being moved. For example, if an autonomously driving vehicle that is currently moving autonomously is involved, the speed reduction can be carried out automatically, in particular depending on environmental conditions such as the road alignment and / or the current vehicle speed. In this case, it can be prevented that the human driver changes the vehicle speed or that it is not possible at all for the human driver to change the vehicle speed. If the vehicle is driven by a human driver, the recommended top speed can be displayed to him on a screen in the vehicle, so that the driver adheres to it as much as possible and accordingly brakes the vehicle or does not accelerate beyond the recommended top speed.

[0021] Furthermore, in the method according to the invention, it is feasible that at least one preparatory measure includes supplementing the main steering operation performed by means of the steer-by-wire module by means of an auxiliary steering operation performed by means of the brake steering module. For example, even without a steer-by-wire module or signs of a complete failure of the main steering operation at the axle, the steer-by-wire module can be supported in lane guidance, for example, by understeer intervention. Thus, the brake steering module can directly and without delay support the steer-by-wire module in all deviations from the trajectory predefined by the driver, for example, during cornering. Furthermore, it is helpful here that the steering must first be "aligned" in the case where the steering actuator fails and does not have its control force. With the alignment of the steering, the support by the brake steering module can be ramped up. To reduce the response time or dead time between the failure of the steer-by-wire module or the main steering operation and the intervention of the brake steering module or the start of the auxiliary steering operation, a watchdog timer can be used. In this way, initial steering support can be achieved by the brake steering module at the first signs of possible critical failures in the steer-by-wire module or the main steering operation.

[0022] According to another variant embodiment of the invention, it is feasible that at least one preparatory measure is taken according to environmental conditions in the vehicle environment. For example, preparatory measures can be taken according to whether it is raining and the lane is wet, whether it is snowing and the lane is accordingly covered with snow, and / or for example, whether fog is recognized and the corresponding line of sight is restricted thereby. The environmental conditions can in particular be understood as weather conditions, light conditions, and / or lane conditions. By taking into account the environmental conditions, the brake steering module that may be put into use can be operated or used particularly effectively.

[0023] On the other hand, the invention relates to a steering system for a vehicle, which has a steer-by-wire module for main steering operation and a brake steering module for auxiliary steering operation, wherein the steering system is configured and designed for:

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

[0025] - identifying error indicators for possible errors in the steer-by-wire module during the main steering operation, and

[0026] - taking at least one preparatory measure according to the identified error indicators for possible execution of an auxiliary steering operation by means of the brake steering module.

[0027] The steering system according to the invention brings the same advantages as detailed with reference to the method according to the invention.

[0028] In addition, within the scope of the present invention, a computer program product is also proposed, which contains instructions for causing the above-mentioned steering system to perform the above-mentioned method steps, and / or for performing the method steps in such a steering system. Additionally, the present invention relates to a computer-readable, in particular non-volatile, storage medium on which such a computer program product is stored.

[0029] The computer program product can be implemented as computer-readable instruction code in all suitable programming languages and / or machine languages, such as JAVA, C++, C#, and / or Python. The computer program product can be stored on a computer-readable storage medium, such as a data disk, a removable drive, a volatile or non-volatile memory, or an internal memory / processor. The instruction code can program a computer or other programmable device, such as a vehicle controller, to perform the desired functions. Additionally, the computer program product can be provided in a network, such as the Internet, and / or can be downloaded by a user from a network, such as the Internet, when needed. The computer program product can be implemented either by software or by one or more dedicated electronic circuits (i.e., hardware) or in any hybrid form (i.e., by software components and hardware components).

[0030] Other measures for improving the present invention are derived from the following description of different embodiments of the present invention, which are schematically shown in the drawings. All features and / or advantages derived from the claims, the description, or the drawings, including structural details and spatial arrangements, are essential to the present invention either individually or in various combinations.

[0031] Schematically respectively:

[0032] Figure 1 shows a vehicle having a steering system according to an embodiment of the present invention,

[0033] Figure 2 shows a storage medium having a computer program product stored thereon according to an embodiment of the present invention,

[0034] Figure 3 shows a flowchart for illustrating a method according to an embodiment of the present invention.

[0035] Figure 1 Schematically shows a vehicle 10 having a steering system 11, which steering system includes a steer-by-wire module 12 for primary steering operation and a brake steering module 13 for auxiliary steering operation. The steering system 11 also has a control device 16, which is signal-connected to the steer-by-wire module 12 and the brake steering module 13. The steering system 11 also includes (not shown) sensing means and actuators through which a desired steering operation can be achieved. The steering system 11 is configured and designed to perform the method steps described in connection with Figure 3 description.

[0036] Figure 2 shows a computer-readable and non-volatile storage medium 15 together with a computer program product 14 stored thereon. The computer program product 14 contains instructions that cause the steering system 11 to perform the method steps described in conjunction with Figure 3 the description. Figure 2 The illustrated computer program product 14 can be installed in Figure 1 the illustrated control device 16 to perform the method described below.

[0037] Figure 3 shows a flowchart of a method for illustrating the operation of Figure 1 the illustrated steering system 11. According to this method, in step S1, the functional operation of the steer-by-wire module 12 during the main steering operation is monitored. In particular, it is determined by appropriate sensing means and / or calculation steps whether there are signs of errors or functional failures 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 determined. In addition, in step S2, it is identified by appropriate sensing means and calculation steps whether the vehicle 10 is currently driving in a curve or will soon enter a curve. If a current or upcoming curve driving is recognized, then in a third step S3, selected preparatory measures are taken according to the recognized error indicator to prepare the vehicle specifically for a possible auxiliary steering operation performed by the brake steering module 13.

[0038] The preparatory measures can be taken in different ways according to the current driving situation, for example, according to the environmental conditions in the environment of the vehicle 10. In addition, the preparatory measures can be taken according to the type of the vehicle 10 and even according to the current driving mode of the vehicle 10, for example, according to the current vehicle speed and / or according to autonomous driving or manual driving. For example, if an autonomous vehicle 10 is involved, different preparatory measures can be taken compared to a vehicle 10 driven by a human driver.

[0039] According to the corresponding individual situation, the preparatory measures can include creating a driving condition according to which the vehicle 10 is allowed or should only drive within a defined inner lane area of the curve. In addition, the preparatory measures can include establishing a braking force in the brake steering module 13 for a possible execution of the auxiliary steering operation. In addition, the preparatory measures can include a reduction in the speed of the vehicle 10, setting the maximum possible highest speed of the vehicle 10 and / or displaying the recommended highest speed of the vehicle 10 perceptible to the driver of the vehicle 10. In addition, the preparatory measures can include supplementing the main steering operation performed by the steer-by-wire module 12 through an auxiliary steering operation performed by means of the brake steering module 13.

[0040] In addition to the illustrated embodiments, the present invention also allows for additional design principles. That is to say, the present invention should not be regarded as limited to the embodiments explained with reference to the accompanying drawings. For example, if the lateral acceleration or the steering effect corresponding to the initially set steering angle can no longer be presented by the brake steering module 13, then the maximum possible lateral guidance of the vehicle 10 by the brake steering module 13 can be pursued or implemented. At the same time, in such a case, in order to minimize the severity of the accident, the maximum speed reduction by the brake steering module 13 is pursued or implemented. Depending on the axle design of the vehicle 10, the maximum lateral acceleration can be achieved with increased slip or individual wheel locking, since the steering angles set by these wheels are no longer meaningful for vehicle guidance and only the decelerating force acts. Depending on the axle structure, a particularly large lateral acceleration can thus be achieved.

[0041] List of reference numerals

[0042] 10 Vehicle

[0043] 11 Steering system

[0044] 12 Steer-by-wire module

[0045] 13 Brake steering module

[0046] 14 Computer program product

[0047] 15 Storage medium

[0048] 16 Controller

Claims

1. A method for operating a steering system (11) of a vehicle (10), wherein, the steering system (11) includes a steer-by-wire module (12) for the main steering operation of the vehicle (10) and a brake-steering module (13) for the auxiliary steering operation of the vehicle (10), and the method has: - monitoring the functional operation of the steer-by-wire module (12) during the main steering operation, - identifying an error indicator for an error in the steer-by-wire module (12) during the main steering operation, and - taking at least one preparatory measure according to the identified error indicator for a possible execution of the auxiliary steering operation by the brake-steering module (13).

2. The method according to claim 1, characterized in that, the at least one preparatory measure is taken when the vehicle is driving or is expected to drive in a curve.

3. The method according to claim 2, characterized in that, the at least one preparatory measure includes establishing a driving condition according to which the vehicle (10) is allowed or should drive only within a defined inner lane area of the curve.

4. The method according to any one of the above claims, characterized in that, the at least one preparatory measure includes establishing a braking force in the brake-steering module (13) for a possible execution of the auxiliary steering operation.

5. The method according to any one of the above claims, characterized in that, the at least one preparatory measure may include reducing the speed of the vehicle, setting the maximum possible top speed of the vehicle and / or perceptibly displaying to the driver of the vehicle the recommended top speed of the vehicle.

6. The method according to any one of the above claims, characterized in that, the at least one preparatory measure includes supplementing the main steering operation performed by the steer-by-wire module (12) by an auxiliary steering operation performed by means of the brake-steering module (13).

7. The method according to any one of the above claims, characterized in that, the at least one preparatory measure is taken according to environmental conditions in the environment of the vehicle (10).

8. A steering system (11) for a vehicle (10), which has a steer-by-wire module (12) for the main steering operation and a brake-steering module (13) for the auxiliary steering operation, wherein, the steering system (11) is configured and designed for: - monitoring the functional operation of the steer-by-wire module (12) during the main steering operation, - identifying an error indicator for a possible error in the steer-by-wire module (12) during the main steering operation, and - taking at least one preparatory measure according to the identified error indicator for a possible execution of the auxiliary steering operation by the brake-steering module (13).

9. A computer program product, which includes instructions that cause the steering system (11) according to claim 8 to perform the method steps according to any one of claims 1 to 7.

10. A computer-readable storage medium (15), which has stored thereon the computer program product (14) according to claim 9.

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