Method and control unit for operating vehicle with defective single-wheel steering regulator

Abstract

The invention relates to a method for operating a vehicle (100) with a single-wheel steering controller (102) having a defect (106), in which an avoidance direction (112) for a steering intervention for avoiding a collision is determined on the basis of the speed of the vehicle (100) and on the side of the defect (106).

Description

Technical Field

[0001] The invention relates to a method for operating a vehicle having a defective wheel steering controller, a corresponding control unit and a corresponding computer program product. Background Art

[0002] The vehicle may have an emergency brake assist system. The emergency brake assist system can trigger emergency braking of the vehicle by automatic brake intervention if the vehicle is in danger of hitting an obstacle and colliding, for example, if the vehicle driver ignores the end of a traffic jam and thus could cause a collision with at least one vehicle at the end of the traffic jam.

[0003] Advanced Emergency Brake Assist can also trigger evasive maneuvers by automatically steering the vehicle to sideways around obstacles and prevent an otherwise unavoidable collision, or reduce braking effort. For example, Advanced Emergency Brake Assist can steer the vehicle into a free lane at the end of a traffic jam, thereby preventing a collision. Summary of the invention

[0004] Against this background, a method for operating a vehicle with a defective wheel steering controller, a corresponding control unit and a corresponding computer program product are described with the method described herein according to the independent claim. Further developments and improvements of the method described herein are derived from the description and are described in the dependent claims.

[0005] Advantages of the present invention

[0006] On a double-track vehicle, two wheels are usually arranged on the same axle, each of which can be steered. Each wheel is usually assigned a separate wheel steering controller. Therefore, the vehicle usually has two single-wheel steering controllers that can be operated and controlled independently of each other.

[0007] If a single-wheel steering regulator of a vehicle is defective, the vehicle's steering capabilities may be limited. For example, the vehicle may steer less in one direction than in another. As a result, unrestricted evasive maneuvers to avoid a collision may no longer be possible.

[0008] The method presented in this paper exploits the fact that, depending on the speed at which the vehicle is traveling, it is easier for the vehicle to steer towards or away from the defect. Therefore, in the method presented in this paper, the defect is recorded and considered together with the vehicle speed in the trajectory planning of the vehicle.

[0009] The method described in this article can be used to predetermine an evasion direction that matches the current speed. This can prevent the planned evasion trajectory from being unachievable. If the speed changes, the evasion direction will also change.

[0010] A method for operating a vehicle with a defective wheel steering controller is described, wherein an avoidance direction for a steering intervention to avoid a collision is determined as a function of the vehicle's speed and / or lateral acceleration and the side of the defect.

[0011] Concepts related to embodiments of the present invention may be considered to be based, among others, on the ideas and cognitions described below.

[0012] A vehicle with a single-wheel steering controller can have a right-hand single-wheel steering controller and a left-hand single-wheel steering controller on the steering axle. The vehicle can also have single-wheel steering controllers on multiple axles. Each single-wheel steering controller acts on a single steerable wheel of the vehicle. The single-wheel steering controllers or the wheels of the steering axle are not mechanically coupled to each other or to the steering wheel of the vehicle in terms of steering. The single-wheel steering controllers are controlled by a central encoder on the steering wheel or the vehicle's steering column via a data signal.

[0013] If one of the single-wheel steering regulators is defective, the other single-wheel steering regulator is usually not affected. If defective, the single-wheel steering regulator may fail completely or have only limited functionality. If the single-wheel steering regulator fails completely, it cannot apply a steering torque to the wheel or only applies a minimal steering torque. A defective single-wheel steering regulator may also apply a small restraining torque to the wheel. If the function of the single-wheel steering regulator is limited, it may, for example, apply a smaller steering torque to the wheel and / or a smaller control speed.

[0014] If one of the single-wheel steering controllers is defective, then essentially only the wheel coupled to the other single-wheel steering controller can still be actively steered. If the vehicle is rolling and the wheel with the defective single-wheel steering controller is rolling freely or only a small torque is acting on the wheel, the wheel with the defective single-wheel steering controller can be centered by its own inertia, i.e., its angle is essentially adapted to the direction of movement of the vehicle. If an external torque, such as a drive torque or a braking torque on the wheel with the defective single-wheel steering controller, exceeds the self-centering torque and / or the damping torque of the defective single-wheel steering controller, or if the steering angle is set too high by the intact controller when the centering force is too low, the wheel will tuck in and its angle will deviate from the direction of movement of the vehicle, i.e., be oriented obliquely or transversely to the direction of movement.

[0015] When the vehicle is moving and the wheels are steered in a manner coupled to a functioning single-wheel steering controller, for example, a narrow turning radius in order to avoid an obstacle to prevent a collision can be steered better to the side of the defective single-wheel steering controller or to the side of the functioning single-wheel steering controller, depending on the speed of the vehicle. Thus, the avoidance direction can be selected depending on the speed. Even if there is no situation in which the vehicle must evade, the avoidance direction can be continuously determined as a preferred avoidance direction depending on the speed. The avoidance direction can, for example, be stored in a memory and read out when an avoidance maneuver is required. The stored avoidance direction can be changed depending on the speed.

[0016] The avoidance direction can also be determined based on the distance to the collision object. The collision object can be, for example, a stationary or slow-moving vehicle on the lane or vehicle track. The collision object can be, for example, a vehicle at the end of a traffic jam in front of the vehicle. The vehicle can also be a vehicle that suddenly slows down, for example due to unexpected braking or an accident. The distance to the collision object determines the required curve radius for a successful avoidance. The smaller the distance, the smaller or narrower the curve radius must be when avoiding. The collision object can also be a potential collision object, i.e. a vehicle traveling in front. The avoidance direction can be stored in a memory for use when avoiding.

[0017] The avoidance direction can be determined as away from the defective side when the speed is below a threshold. In addition, the avoidance direction can also be determined as away from the defective side when the distance is greater than a distance value. "Defective side" or "side with a defective single-wheel steering regulator" should be understood as the side of the vehicle where the defective single-wheel steering regulator is located. At low speeds and large curve radii, i.e. small dynamic avoidance maneuvers, the wheels on the inside of the curve determine the lane (spurbestimmend), i.e. where the vehicle is going. The wheels on the outside of the curve can follow by their inertial motion. If the distance is large enough, it is possible to avoid using a larger curve radius. For example, if it is above the threshold and / or below the distance value, the lateral acceleration can exceed 4m / s 2 .

[0018] The avoidance direction can be determined as being towards the defect side when the speed is greater than a threshold value. Alternatively or additionally, the avoidance direction can also be determined as being towards the defect side when the distance is less than a distance value. At higher speeds and smaller curve radii, i.e. during highly dynamic avoidance maneuvers, the vehicle begins to wanken, the wheels on the outside of the curve are loaded, and the wheels on the inside of the curve are unloaded. As a result, the wheels on the outside of the curve can transfer a greater lateral guiding force to the ground than the wheels on the inside of the curve. Therefore, the wheels on the outside of the curve determine the lane during highly dynamic avoidance maneuvers and determine where the vehicle is traveling.

[0019] If the required avoidance space in the preferred avoidance direction is occupied, the steering intervention can be classified as inappropriate. The avoidance space for the evasive maneuver can be located on the right or left side of the collision object. In particular, the avoidance space can be located in a lane or an emergency stop lane to the right or left of the collision object. The sensor system of the vehicle can monitor the environment around the vehicle. The sensor system can monitor the avoidance space. If another vehicle or another obstacle is detected in the avoidance space, the vehicle can cause a further collision when it avoids into the avoidance space before the collision object. If another vehicle or another obstacle is detected in the avoidance space, it can be detected that the avoidance space is occupied. In this way, a further collision can be prevented. The monitoring of the avoidance space can be carried out continuously and the avoidance space can be stored in a memory as currently occupied or currently free.

[0020] Furthermore, an intervention distance for a braking intervention to avoid a collision can be set as a function of speed, available avoidance space and the side of the defect. The intervention distance can be the distance to the collision object from which an automatic braking intervention to avoid a collision is triggered. If a defect is detected, the intervention distance can be increased. The intervention distance can increase with increasing speed. If an occupied avoidance space is detected, the intervention distance can be further increased in order to prevent or at least mitigate a collision, even without avoiding it.

[0021] The method is preferably computer-implemented and can be implemented, for example, in software or hardware or in a hybrid form of software and hardware, for example in a driver assistance system.

[0022] The method described herein also creates a controller, wherein the controller is designed to execute, control or implement the variant steps of the method described herein in a corresponding device.

[0023] A controller can be an electrical device with at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading in or outputting data embedded in a communication protocol. For example, the computing unit can be a signal processor, a so-called system ASIC or a microcontroller for processing sensor signals and outputting data signals as a function of the sensor signals. The storage unit can be, for example, a flash memory, an EPROM or a magnetic storage unit. The interface can be configured as a sensor interface for reading in sensor signals from a sensor and / or an actuator interface for outputting data signals and / or control signals to an actuator. The communication interface can be configured to read in or output data wirelessly and / or wired. For example, the interface can also be a software module present on a microcontroller together with other software modules.

[0024] A computer program product or computer program with program code, which can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, hard disk storage or optical storage, is also advantageous for executing, realizing and / or controlling the method steps according to one of the above-described embodiments, in particular if the program product or the program is implemented in a computer, a controller or a device.

[0025] It should be noted that some possible features and advantages of the present invention are described herein with reference to different embodiments. It will be appreciated by those skilled in the art that the features of the controller and the method may be appropriately combined, adjusted or interchanged to achieve other embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The embodiments of the present invention are described below with reference to the accompanying drawings, but the drawings and the description shall not be interpreted as limiting the present invention.

[0027] Figure 1 and Figure 2 A diagram of a vehicle is shown with a defective single-wheel steering controller and at different speeds when initiating an evasive maneuver using a method according to an exemplary embodiment.

[0028] The figures are schematic only and are not drawn to scale. Identical reference numerals denote identical or identically acting features. DETAILED DESCRIPTION

[0029] Figure 1 A diagram of a vehicle 100 is shown, which has a defective single-wheel steering controller 102 and is at a low speed when initiating an evasive maneuver using a method according to one embodiment.

[0030] Figure 2 A diagram of a vehicle 100 is shown, which has a defective wheel steering controller 102 and is at a high speed when initiating an evasive maneuver using a method according to an exemplary embodiment.

[0031] In these two figures, the vehicle 100 has front wheels 104, each of which is steered via a single-wheel steering regulator 102. In the example shown, the left single-wheel steering regulator 102 has a defect 106. The right single-wheel steering regulator 102 is fully functional without restriction. The defective single-wheel steering regulator 102 cannot apply any steering torque to the left front wheel 104. Alternatively, due to the defect 106, the single-wheel steering brake can only provide a reduced steering torque. Here, the defective single-wheel steering regulator 102 can only apply a small holding torque to the left front wheel 104. Therefore, when the vehicle 100 rolls, the left front wheel 104 can adapt its steering angle to the direction of motion of the vehicle 100 through its inertial operation, if the torque generated by the inertial operation is greater than the holding torque and the external torque generated by braking or driving the front wheel 104.

[0032] In both figures, vehicle 100 is traveling towards a collision object 108 or an obstacle. Collision object 108 is, for example, a stationary truck (LKW) here. If vehicle 100 does not brake and / or evade, it will collide with collision object 108. The available braking distance to collision object 108 may already be so short that a collision may still occur despite emergency braking intervention. By evading into an evasion space 110 next to collision object 108, a collision can be prevented, and since evasion space 110 provides an extended braking distance, emergency braking intervention can be performed with a reduced braking torque.

[0033] exist Figure 1 The vehicle 100 is traveling at a lower speed. The dynamic avoidance maneuver is smaller due to the lower speed, and in this case, the weight of the vehicle 100 is only slightly transferred to the wheel on the outside of the curve. Therefore, the front wheel 104 on the inside of the curve determines the lane at a lower speed.

[0034] exist Figure 2 The vehicle 100 is traveling at an increased speed. The increased speed results in a dynamic evasive maneuver in which a large portion of the weight of the vehicle 100 is transferred to the front wheels 104 on the outside of the curve, while the front wheels 104 on the inside of the curve are unloaded. Therefore, the front wheels 104 on the outside of the curve determine the lane when the speed increases.

[0035] Since the speed determines which side determines the lane, in the method presented here, the side of the defect 106 and the speed are used to determine the evasion direction 112 of the evasive maneuver. The evasion direction 112 is determined in such a way that the fully functional single-wheel steering controller 102 is located on the lane-determining side, while the single-wheel steering controller 102 with the defect 106 is located on the non-lane-determining side. The evasion direction 112 can be determined continuously and called up when a collision risk is detected. This saves the time required for the determination.

[0036] In one embodiment, when the speed is lower than a threshold, it is assumed that the wheels on the inner side of the curve determine the lane, and when the speed is higher than the threshold, it is assumed that the wheels on the outer side of the curve determine the lane. Therefore, the avoidance direction 112 is determined to be away from the defect 106 when the speed is lower than the threshold, and is determined to be toward the defect 106 when the speed is higher than the threshold.

[0037] In one embodiment, the avoidance direction 112 is determined using the distance to the collision object 108. When a collision risk is identified, the closer the distance between the vehicle 100 and the collision object 108 is, the more dynamic the avoidance action must be to succeed. For example, the speed threshold may decrease as the distance decreases.

[0038] In one embodiment, the avoidance direction 112 is determined only when the avoidance space 110 in the avoidance direction 112 is free. If the avoidance space 110 in the avoidance direction 112 is occupied, the avoidance direction 112 is not stored, and if there is a risk of collision, emergency braking is performed without avoidance.

[0039] In one embodiment, the intervention distance of the evasive maneuver is set depending on the side of the defect 106, the speed and the available evasive space 110. For example, if the evasive space 110 is only available on the side opposite the defect 106, no dynamic evasive maneuver can be performed on the side of the defect 106. In order to be able to take an evasive action anyway, a smaller dynamic evasive maneuver must be performed on the side away from the defect 106. Only when the distance to the collision object 108 increases, i.e. the intervention distance increases, can a smaller dynamic evasive maneuver be performed. When the evasive space 110 on the side of the defect 106 is free again, the intervention distance can be reduced again.

[0040] Possible embodiments of the invention will be summarized again below or described in slightly different wording.

[0041] An operating strategy for speed-dependent control of a single-wheel steering actuator in the event of a steering actuator failure or degradation is presented.

[0042] Today's cars are equipped with an electromechanical steering system that is connected to both wheels. The development of steering systems is increasingly moving towards drive-by-wire systems, in which the mechanical coupling between the drive-by-wire system and the driver is removed. This eliminates the traditional mechanical connection between the driver and the wheels via the steering wheel. When steering, the corresponding drive is purely realized by one or more actuators. Centralized and decentralized drive-by-wire actuators are currently installed on the rear axle. The first prototypes with individual drive-by-wire wheel steering actuators are known for the front axle, such as the SpeedE research vehicle.

[0043] The Automatic Collision Avoidance (ACA) driver assistance function provides support in dangerous situations, such as when the driver realizes the end of a traffic jam too late. Unlike conventional emergency braking, the system automatically swerves the vehicle into a free lane if there is not enough space for emergency braking in the current lane. If the distance to the end of the traffic jam is large enough, the assistance system uses conventional emergency braking to stop the car. On highways at speeds up to 130 km / h, the automatic collision avoidance system supports the driver.

[0044] In the future, NCAP tests will include requirements for automatic avoidance.

[0045] Until now, there has been no optimal steering strategy for evasive maneuvers in the event of a controller failure for single-wheel steering controllers. In the event of a single-wheel steering controller failure, the strategy for handling the drive and braking can take into account a partial reduction in the braking capacity on the side of the failed steering controller, which can make evasive maneuvers more important, since the reduced braking capacity is intended to prevent the vehicle with the defective controller from folding in / out.

[0046] The method presented here makes use of the fact that, depending on the speed or lateral acceleration and the associated transfer of wheel loads, different optimal actuations of the remaining wheel steering controllers result.

[0047] When the lateral acceleration is less than 4m / s 2 In less dynamic driving, due to the steering geometry design close to Ackermann, the inner wheel dominates the lane (spurdominant) when turning, that is, it plays a decisive role in the driving trajectory.

[0048] At relatively high speeds or small curve radii, the wheel on the outside of the curve is in the dominant lane due to the dynamic wheel load transfer (sway).

[0049] This means, for example, that when approaching the end of a traffic jam, swerving to one side (left or right at the end of the traffic jam) could result in a collision, depending on which side the regulator is faulty, whereas swerving to the other side would not. In addition, this could leave more room for initiating further measures, e.g. due to the narrower radius of the bend.

[0050] This information can be provided to the emergency brake assist system using the method described in this article, so that it knows from what point in time only full braking can be performed and on which side evasion can still be performed. These measures can be used to determine the remaining time to approach the obstacle and input this into the emergency brake assist system.

[0051] If the distance is sufficient, evasion and braking are possible in both directions.

[0052] If the distance is too short, evasion and braking are only possible in one direction. The side on which the steering brake fails is taken into account.

[0053] If only emergency braking is possible, the operating strategy presented here improves the residual performance in the event of a system failure and thus increases safety.

[0054] Applied to a single-wheel steering controller, this means, for example, that if the left steering controller fails, when approaching a stationary obstacle in the range of lower speeds or lateral accelerations, steering to the right is advantageous due to the purely kinematic steering effect without wheel load transfer, because the remaining right wheel can achieve stronger steering on the inside of the curve. When the speed or lateral acceleration increases, turning to the left has advantages in terms of the achievable curve radius, because the wheel on the outside of the curve dominates the lane guidance.

[0055] Furthermore, the information from surrounding sensors can be incorporated into the functions described here in order to determine the correspondingly permissible evasive trajectory and to determine the minimum necessary but maximum possible dynamics. If the ideal evasive direction is not possible, for example due to traffic conditions ahead or behind, a non-preferred direction can be selected or the evasive maneuver can be abandoned in favor of maximum deceleration braking. In addition, braking measures can be initiated in advance.

[0056] Taking the passive failure of the left regulator as an example, it avoids to the right under lower speed / lateral acceleration conditions and to the left under higher speed / lateral acceleration conditions.

[0057] The operating strategy presented in this article can also be used for a single-wheel steering regulator with reduced performance, for example, if the steering torque is insufficient to dynamically apply the target steering angle when 50% of the steering torque remains.

[0058] In addition, the operating strategy introduced in this paper can also be used for steer-by-wire and EPS central controllers.

[0059] Finally, it should be pointed out that the terms "having", "comprising" etc. do not exclude other elements or steps, and the terms "a (eine)" or "an (ein)" do not exclude a plurality. Reference signs in the claims should not be considered limiting.

Claims

1. A method for operating a vehicle (100) having a defective (106) single-wheel steering regulator (102), wherein: An avoidance direction (112) for a steering intervention to avoid a collision is determined as a function of the speed of the vehicle (100) and the side of the defect (106).

2. The method according to claim 1, wherein: The avoidance direction (112) is also determined based on the distance to the collision object (108).

3. A method according to any one of the preceding claims, wherein: The avoidance direction (112) is determined to be away from the side of the defect (106) when the speed is less than a threshold value and / or the distance is greater than a distance value.

4. A method according to any one of the preceding claims, wherein: The avoidance direction (112) is determined to be toward the defect (106) when the speed is greater than a threshold value and / or the distance is less than a distance value.

5. A method according to any one of the preceding claims, wherein: If the required avoidance space (110) is occupied in the preferred avoidance direction (112), the steering intervention is classified as inappropriate.

6. A method according to any one of the preceding claims, wherein: An intervention distance for a braking intervention to avoid a collision is also set as a function of the speed, the available avoidance space (110) and the side of the defect (106).

7. The method according to claims 5 and 6, wherein: When the avoidance space (110) is occupied, the intervention distance increases.

8. A controller, wherein: The control unit is designed to execute, carry out and / or control the method according to one of the preceding claims in a corresponding device. 9 . A computer program product, which is configured to instruct a processor to execute, carry out and / or control the method according to claim 1 when the computer program product is executed.

10. A machine-readable storage medium on which the computer program product according to claim 9 is stored.

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