Vehicle control method with steering angle correction

Abstract

The invention relates to a vehicle control method (1), comprising: detecting (17) an unstable driving state (330) of a vehicle (300) in advance at least using an actual variable (9) and a target trajectory (TSoll); wherein, during the early detection (17), it is ascertained whether the unstable driving state (330) is an understeer (332) of the vehicle (300) or an oversteer (334) of the vehicle (300); and in response to the early detection (17): defining (40) a steering angle correction (41) for the target steering angle ([delta] Soll), the steering angle correction (41) comprising a steering angle limit ([delta] lim) for the available actual steering angle ([delta] Ist) if the unstable driving state (330) is an understeer (332) of the vehicle (300); and wherein, if the unstable driving state (330) of the vehicle (300) is an oversteering (334), the steering angle correction (41) comprises a reverse steering angle (cs) directed opposite the target steering angle ([delta] Soll); and steers (47) the vehicle (300) using the steering angle correction (41). The invention also relates to a vehicle control system (200), a vehicle (300) and a computer program product.

Description

Technical Field

[0001] The present invention relates to a vehicle control method for a vehicle having an electronically controllable steering unit, a vehicle control system, a vehicle and a computer program product. Background Art

[0002] Vehicle automation is one of the main areas of development in the modern automotive industry. Semi-autonomous vehicles take over some of the tasks involved in controlling the vehicle, while autonomous vehicles perform control completely without human intervention. Autonomous vehicles therefore control the lateral and longitudinal guidance of the vehicle completely independently of the human operator. In contrast, semi-autonomous vehicles only take over some of the tasks involved in controlling the vehicle. As vehicle automation continues to increase, vehicles are increasingly taking over steering tasks, such as lane keeping or distance control. Autonomous vehicles always have an electronically controllable steering system, but semi-autonomous vehicles can also include such a system, for example if the vehicle has a lane keeping assist system that can autonomously keep the vehicle within its lane. The electronically controllable steering system controls the vehicle at least partially based on electrical signals.

[0003] Thus, the autonomous control unit (also known as the virtual driver) can predetermine a steering request for the electronically controllable steering system, which then causes the vehicle to turn or steer. To steer, the virtual driver can predetermine a steering request (e.g., a steering angle) for the electronically controllable steering system or provide a target trajectory to the steering control system, which then infers the corresponding steering request based on this target trajectory. The target trajectory at least includes the driving path that the vehicle should follow. Furthermore, the target trajectory can include additional information, such as a speed profile that specifies a target speed for the vehicle at one or more points along the driving path. Furthermore, the target trajectory can include other target predefined parameters, such as the vehicle's orientation, particularly the heading angle, the yaw rate, and / or the steering angle associated with one or more points along the driving path.

[0004] Due to various influences, it may occur that the vehicle cannot follow the predetermined target trajectory or obtains a trajectory deviation. Then, the vehicle will not travel along the driving path included in the trajectory, but will travel in a staggered manner or with different orientations.

[0005] A virtual driver or the vehicle's steering controller (which can also be part of the virtual driver) attempts to compensate for track deviations using electronically controlled steering (also known as active steering). When cornering, if the vehicle drifts laterally toward the outside of the curve, the steering controller attempts to compensate for this lateral deviation by steering further inward (increasing the steering angle toward the inside of the curve). This approach fails under unfavorable road conditions because the vehicle does not react to the steering parameters as the steering controller intended. Consequently, under unfavorable road and / or weather conditions, the vehicle may be unable to navigate the desired curve because the lateral guiding forces built up between the vehicle's tires and the road surface are insufficient to guide the vehicle against inertia along the desired curvature of the driving path. In particular, if yaw instability is present, i.e., the vehicle is understeering or oversteering, track deviations may not be compensated by increasing the steering parameters. Known virtual drivers and / or steering controllers are not designed to safely control automated or autonomous vehicles in all situations. In situations where known traction controllers are unable to compensate for trajectory deviations, conventional stability control systems, such as the so-called Electronic Stability Control (ESC), must intervene. Due to the predetermined intervention thresholds of the stability control system, this intervention occurs only when the vehicle is severely unstable and therefore very late. This increases space requirements and the risk of accidents. Furthermore, in the event of an instability, the vehicle may no longer react to changes or modifications in the steering angle, and further inward steering by the traction controller, especially in the event of understeering, can even worsen vehicle stability. Furthermore, even in the event of oversteering, late and / or incorrect countersteering can further deteriorate vehicle stability.

[0006] DE 10 2020 117 322 A1 discloses a vehicle system for a vehicle with an electronically controllable steering unit. In the event of a failure of the electronic stability control during driving, the electronically controllable steering unit will implement a steering intervention for lateral stability in order to keep the vehicle within a tolerance corridor of a predetermined target trajectory of the vehicle. The steering intervention compensates for the wheel-specific braking that is no longer available on the axle-controlled axle due to the failure of the electronic stability control. The system provides a fallback level when the electronic stability control of the main system is no longer available. The disclosed system therefore relates to a fallback level for a conventional stability control system and enables non-premature stability intervention. In addition, the steering intervention is used to keep the vehicle within the tolerance corridor so that trajectory deviations are accepted. Summary of the Invention

[0007] There is a need for a vehicle control method that overcomes the aforementioned disadvantages. The object of the present invention is to specify a vehicle control method in which an instability is detected early and the vehicle is steered in a manner adapted to the situation.

[0008] The present invention solves this problem in a vehicle control method of the type mentioned at the outset, which comprises: determining a target trajectory of the vehicle; determining a target steering angle for driving along the target trajectory; identifying an unstable driving state of the vehicle in advance at least when using the target trajectory; wherein, when identifying in advance, it is determined whether the unstable driving state is vehicle understeering or vehicle oversteering; and, in response to the early identification of the unstable driving state, limiting a steering angle correction for the target steering angle, wherein, if the unstable driving state is vehicle understeering, the steering angle correction includes steering angle limitation of an actual steering angle that can be provided by an electronically controllable steering unit, and wherein, if the unstable driving state of the vehicle is oversteering, the steering angle correction includes a counter steering angle directed opposite to the target steering angle; and steering the vehicle when using the steering angle correction.

[0009] The present invention is based on the concept of enabling early detection of unstable driving states using a target trajectory and on the recognition that measures taken by the position controller and / or virtual driver to compensate for unstable driving states may not be sufficient to eliminate them. Early intervention can prevent dangerous situations. The steering angle correction corrects the steering angle associated with the target trajectory. This allows the vehicle to be stabilized and / or prevents steering interventions that could exacerbate unstable driving states.

[0010] The target trajectory is preferably provided by a unit for autonomous driving (particularly a virtual driver), for example via a vehicle bus. The vehicle control method preferably includes performing trajectory planning to obtain the target trajectory. The target steering angle is the steering angle of the vehicle predicted by the virtual driver or other autonomous unit in order to travel along the target trajectory, wherein the virtual driver assumes that the vehicle is in a stable driving behavior. Preferably, the target steering angle is included in the target trajectory. The target trajectory then includes not only the driving path to be traveled but also the target steering angle predicted for traveling along that driving path. Preferably, the target steering angle is determined based on a model. For example, when determining the target trajectory, the virtual driver can determine the target steering angle to be predetermined based on a vehicle model. The vehicle model can be a single-track model of the vehicle. The target steering angle can be determined using the vehicle's speed or speed profile while traveling along the target trajectory, wherein the speed and / or speed profile can be included in the target trajectory. Actual variables are variables that occur while traveling along the trajectory or in the driving state associated with the target trajectory.

[0011] The early detection of unstable driving states of the vehicle is carried out at least using actual variables and a target trajectory. In contrast to previously known methods, instability is not detected only when various vehicle sensors report significant actual deviations from predefined threshold values. According to the invention, the target trajectory is taken into account and allows instability to be detected in a manner adapted to the respective driving situation. Thus, for example, an unstable driving state can be detected early when the actual variables deviate from the target trajectory or variables derived from the target trajectory by more than a tolerance limit. An unstable driving state may be an oversteering or understeering of the vehicle. Oversteering and understeering are common terms for describing the driving behavior of a vehicle. Understeering means that the so-called self-steering gradient of the vehicle is greater than zero, so that a stronger steering is required to follow a curve than in the case of a vehicle in a neutral state. Oversteering of the vehicle is also often colloquially referred to as vehicle skidding.

[0012] Steering angle correction is limited in response to the early detection of unstable driving conditions. In the case of understeer, steering angle correction includes limiting the actual steering angle that can be provided. In the case of understeer, the vehicle deviates from the planned driving path toward the outside of the curve. The vehicle's position controller continuously increases the actual steering angle, i.e., steers the vehicle inward more strongly, in an effort to adhere to the planned driving path. The target steering angle required for stable driving is exceeded. However, this approach becomes ineffective if the lateral deviation of the front wheels exceeds a certain limit, as the tires can no longer exert any further lateral guiding force. This typically occurs when the adhesion between the tires and the road surface decreases, such as in wet or slippery conditions. If the adhesion between the tires and the road surface suddenly increases again when the actual steering angle is large, the steered wheels will suddenly build up a large lateral guiding force, potentially making the vehicle unmanageable. The method according to the present invention eliminates this risk by limiting the steering angle limit in the case of understeer. The vehicle steers using steering angle correction, so that the actual steering angle is never set beyond a reasonable or safe value. Thus, the steering angle limitation can, for example, limit the actual steering angle that can be provided by the electronically controllable steering to a maximum of 30°.

[0013] In the event of oversteering, the vehicle turns inward more strongly than would otherwise be required to follow the current driving path. In this case, the vehicle typically also leaves the planned driving path. However, in the event of oversteering, the positioning controller and / or autonomous driver do not allow the steering angle to return to the planned driving path based solely on the vehicle's misalignment from the planned driving path. Therefore, when the vehicle veers laterally to the outside of a curve, the actual steering angle, based solely on the positioning deviation, will increase further in the direction of the curve, thereby further exacerbating the oversteering. Instead, the vehicle's response should be adapted to the excessive yaw rate and appropriately dampened through countersteering. In the method according to the present invention, this is achieved by including a steering angle correction that includes a countersteering angle that is directed opposite to a target steering angle directed toward the inside of the curve. When the vehicle is steered using the steering angle correction, the countersteering angle counteracts the target steering angle and stabilizes the vehicle. The countersteering angle counteracting the target steering angle has an opposite sign to the actual steering angle. If the actual steering angle is positive (i.e., measured counterclockwise), the countersteering angle is negative (measured clockwise).

[0014] In a first preferred embodiment, the method further includes, in response to the early detection of an unstable driving state, wheel-specific deceleration of at least one wheel of the vehicle. In addition to steering angle correction, the method, in a preferred embodiment, also includes individual deceleration of at least one wheel of the commercial vehicle. This wheel-specific deceleration is preferably used to generate a yaw moment on the vehicle. Consequently, the yaw rate achievable through steering may be limited due to steering angle limitations or other factors (e.g., a low coefficient of friction between the vehicle and the road surface). Wheel-specific deceleration can compensate for the difference between the target yaw rate and the yaw rate that can be set by the steering. Preferably, brake slip is regulated at the wheel to be decelerated to decelerate the wheel. This can be achieved, for example, by applying brake pressure to a brake actuator associated with the wheel. However, the wheel to be decelerated can also be decelerated, for example, through recuperation. The wheel to be decelerated wheel-specifically is decelerated independently of the remaining wheels of the vehicle. However, provision can be made for two or more wheels of the vehicle to be decelerated simultaneously and to an equal degree. Thus, for example, all wheels of the vehicle oriented toward the center of the curve (i.e., all wheels on the inside of the curve) can be decelerated to the same degree. However, it is of course also possible to decelerate only a single wheel. Thus, when compensating for oversteer, for example, the front wheel on the outside of the curve can be decelerated to provide a yaw moment to counteract oversteer. The control variables required for deceleration and / or the selection of the correct wheel are preferably determined using a target trajectory and actual variables. Unlike conventional stability control (ESC), in which the degree of intervention is measured solely via the steering, the target variable is also taken into account. The wheel-specific deceleration preferably provides an additional yaw moment that acts in the direction of the steering angle correction. In the case of understeer, the steering angle correction or steering angle limitation acts in the direction of the target steering angle. Thus, the steering angle correction counteracts vehicle yaw toward the outside of the curve. In the case of oversteer, the counter-steering angle acts toward the outside of the curve, so that the yaw moment provided by the wheel-specific deceleration counteracts any unwanted rotation of the vehicle toward the inside of the curve. Preferably, the wheel-specific deceleration is not performed per axle. Therefore, the wheels of the commercial vehicle belonging to the same axle are preferably decelerated unequally.

[0015] Preferably, if the unstable driving state of the commercial vehicle is understeering, the at least one wheel of the vehicle is a wheel on the inside of the curve of the commercial vehicle, in particular a rear wheel on the inside of the curve of the commercial vehicle. If the unstable driving state of the commercial vehicle is oversteering, the at least one wheel of the commercial vehicle is preferably a wheel on the outside of the curve of the commercial vehicle, in particular a wheel on the outside of the curve on the front axle.

[0016] Furthermore, it is preferred that, if the unstable driving state is understeering of the vehicle, the steering angle limit preferably corresponds to the target steering angle plus a steering angle margin. By taking into account a fixed or variable steering angle margin, the steering angle limit can be defined particularly easily. The steering angle margin is preferably determined taking into account the target trajectory. Thus, in the case of a large curvature of the driving path or a high speed, the steering angle margin can be selected to be larger than in the case of a target trajectory corresponding to slow vehicle travel. The target steering angle is preferably an Ackermann steering angle, which is determined by the radius of curvature of the trajectory and the wheelbase of the vehicle. Preferably, the target steering angle can also take into account the force buildup of the tires. Thus, it can be provided that the target steering angle takes into account the contact patch of the tires when driving on a bend, which is necessary to build up lateral guiding forces in the contact surface between the tires and the road surface.

[0017] According to another preferred embodiment, the steering angle margin is determined using surface information of the road surface, which is preferably included in the target trajectory. The target trajectory may, for example, include surface information indicating a smooth road surface with significantly reduced friction. However, it is also possible to provide separate surface information. The optimal slip angle at which the vehicle's wheels can achieve maximum lateral guidance depends on the surface of the road surface or the coefficient of friction between the vehicle's wheels and the road surface on which the vehicle is traveling. The optimal slip angle has a lower value on icy surfaces than on rough, dry surfaces. Therefore, on icy surfaces, even at relatively low actual steering angles, no further lateral guiding force can be generated. Therefore, on icy surfaces, the steering angle limitation is preferably more severe, or the steering angle margin is lower, than on dry surfaces, because further increasing the steering angle is no longer meaningful at relatively small steering angles.

[0018] Preferably, the method further comprises: monitoring the vehicle's posture; determining the vehicle's trajectory deviation using the target trajectory and the monitored posture; and determining the rate of change of the trajectory deviation. When monitoring the vehicle's posture, the vehicle's posture is preferably determined continuously or at discrete time intervals. By monitoring the posture, changes in the vehicle's posture can be determined. The posture preferably includes the vehicle's position. Alternatively or additionally, the posture may also include the vehicle's orientation, particularly the heading angle. The heading angle refers to the angle between geographic north and the vehicle's target direction. For example, when a vehicle is traveling east, the vehicle moves at a heading angle of 90°. However, the heading angle may also be an angle in a coordinate system fixed relative to the vehicle. The trajectory deviation is the deviation of the vehicle's posture from the trajectory. The trajectory deviation preferably includes or includes the vehicle's position deviation between the vehicle's actual position on the driving path and the vehicle's target position. An example of a position deviation is the vehicle's lateral offset from the driving path, transverse to the direction of travel. However, the trajectory deviation may also include or include the vehicle's actual heading angle and the target heading angle. The trajectory deviation rate of change describes the temporal change of the trajectory deviation. The trajectory deviation rate of change preferably describes the change in trajectory deviation over a specific time period compared to the duration of the time period. The time period considered is preferably short. The duration of the time period is preferably 10 seconds or less, preferably 8 seconds or less, preferably 6 seconds or less, preferably 5 seconds or less, preferably 4 seconds or less, preferably 3 seconds or less, preferably 2 seconds or less, and preferably 1 second or less. A continuously increasing trajectory deviation is evidence of an unstable driving state. For example, an increasing trajectory deviation rate of change occurs when a vehicle understeers while navigating a curve, resulting in a continuously increasing lateral offset (i.e., the amount by which the vehicle is offset perpendicular to the driving path). Knowing the trajectory deviation rate of change makes it particularly easy to detect unstable driving states in advance. Thus, even a relatively small positioning deviation, based on the vehicle's state on the driving path, can cause an increasing trajectory deviation rate of change. Consequently, an unstable driving state can be identified even when the absolute trajectory deviation is small and / or when the virtual driver may not have yet initiated steering intervention. Conventional stability control systems react to steering interventions, so they only detect unstable driving conditions when steering is initiated. Therefore, unstable driving conditions can be detected significantly earlier than with conventional stability control systems using the trajectory deviation rate. However, it should be understood that determining the trajectory deviation rate is a preferred, but not essential, step for early detection of unstable driving conditions when using a target trajectory.

[0019] In a preferred refinement, the actual variable is an actual yaw rate, and early identification of an unstable driving state of the vehicle, at least using the actual variable and a target trajectory, includes: determining a target yaw rate of the vehicle using the target trajectory; determining the actual yaw rate of the vehicle; and detecting an unstable driving state if the actual yaw rate lies outside a yaw rate tolerance band around the target yaw rate. Preferably, determining the actual yaw rate is or includes measuring the actual yaw rate, preferably using a yaw rate sensor of the vehicle. However, determining the actual yaw rate may also be performed using a signal provided on a vehicle network (preferably a vehicle bus, particularly preferably a CAN bus). For example, and preferably, a stability control system, particularly an ESC control unit, may provide a signal representing the actual yaw rate of the vehicle on the vehicle network. The yaw rate tolerance band defines a range of values around the target yaw rate. The target yaw rate is a predicted yaw rate of the vehicle for the target trajectory. Preferably, a deceleration measure for decelerating at least one wheel is determined based on a measure of the deviation of the actual yaw rate from the target yaw rate. The deceleration metric is preferably a slip request for at least one wheel.

[0020] Preferably, if the absolute value of the actual yaw rate lies below a yaw rate tolerance band, understeering of the commercial vehicle is detected; if the absolute value of the actual yaw rate lies above the yaw rate tolerance band, oversteering of the vehicle is detected. If the absolute value of the actual yaw rate is less than the absolute value of the target yaw rate and the actual yaw rate is not within the yaw rate tolerance band, the actual yaw rate is detected to be below the yaw rate tolerance band. Similarly, if the absolute value of the actual yaw rate is greater than the absolute value of the target yaw rate and the actual yaw rate is not within the yaw rate tolerance band, the actual yaw rate is detected to be above the yaw rate tolerance band. The actual yaw rate and target yaw rate are preferably considered in absolute terms. If the absolute value of the actual yaw rate lies below the yaw rate tolerance band, the vehicle is understeering. Conversely, if the absolute value of the actual yaw rate lies above the yaw rate tolerance band, the vehicle is oversteering. Considering the actual yaw rate in absolute terms has the advantage that this method is applicable to both left-hand and right-hand curves.

[0021] In a preferred refinement, understeer or oversteer is detected only when the trajectory deviation change rate indicates an increasing trajectory deviation of the vehicle from the target trajectory. Thus, according to the preferred refinement, understeer is detected only when the actual yaw rate lies below the yaw rate tolerance band and the trajectory deviation is increasing. Similarly, in the preferred refinement, oversteer is detected only when the actual yaw rate lies above the yaw rate tolerance band and the trajectory deviation is increasing. This makes the detection of unstable driving states more robust and minimizes the risk of erroneous detection. This eliminates, for example, erroneous detections in situations where the vehicle enters a curve with a lateral deviation from the driving path within the target trajectory but then continues to steadily follow the curve with a constant lateral deviation.

[0022] Preferably, obtaining the target yaw rate of the vehicle using the target trajectory includes: obtaining the curvature of the target trajectory; obtaining the actual speed of the vehicle; and obtaining the target yaw rate using at least the curvature of the target trajectory and the actual speed of the vehicle.

[0023] Preferably, the yaw rate tolerance band has a width around the target yaw rate value of ±0.1° / s to ±10° / s, preferably ±0.1° / s to ±8° / s, preferably ±0.3° / s to ±8° / s, preferably ±0.3° / s to ±6° / s, preferably ±0.3° / s to ±5° / s, preferably ±0.3° / s to ±4° / s, preferably ±0.4° / s to ±4° / s, preferably ±0.5° / s to ±4° / s, preferably ±0.5° / s to ±3° / s, preferably ±0.5° / s to ±2° / s. Preferably, the yaw rate tolerance band has a width around the target yaw rate value of ±6° / s or less, preferably ±5° / s or less, preferably ±4° / s or less, preferably ±3° / s or less, preferably ±2° / s or less, particularly preferably ±1.5° / s or less. For example, if the target yaw rate has an absolute value of 10° / s and the yaw rate tolerance band has a width of ±1.5° / s, an unstable driving state is detected if the absolute value of the actual yaw rate is less than or equal to 8.5° / s (understeer) or the absolute value of the actual yaw rate is greater than or equal to 11.5° / s (oversteer). Preferably, the yaw rate tolerance band can also be determined dynamically. Therefore, the yaw rate tolerance band is preferably defined based on the curvature of the target trajectory, with greater curvature resulting in a wider yaw rate tolerance band and less curvature resulting in a narrower yaw rate tolerance band. Preferably, the yaw rate tolerance band has a minimum width that does not fall below this minimum width even when the target trajectory has no curvature (on a straight road).

[0024] In one variant, if the unstable driving state is oversteer, the countersteer angle is determined using the yaw rate deviation between the actual yaw rate and the target yaw rate. The yaw rate deviation is preferably determined based on the absolute value of the actual yaw rate and the absolute value of the target yaw rate. Therefore, the yaw rate deviation is independent of the direction of the curve. Using the yaw rate deviation to determine the countersteer angle is particularly effective in counteracting oversteer. A larger yaw rate deviation also results in a larger countersteer angle. Consequently, strong countersteer is also performed when the vehicle is experiencing a severe sideways slip.

[0025] According to a preferred embodiment, the actual variable is the actual steering angle, and early detection of an unstable driving state of the vehicle, at least using the actual variable and a target trajectory, includes: performing a target-actual comparison between the actual steering angle and a target steering angle; and early detection of an unstable driving state if a trajectory deviation is detected and the actual steering angle deviates from the target steering angle by at least a steering angle tolerance value. It should be understood that early detection of an unstable driving state can be based on both the actual steering angle and the actual yaw rate. Thus, an unstable driving state is detected only when the actual yaw rate lies outside the yaw rate tolerance band and the actual steering angle deviates from the target steering angle by the steering angle tolerance value. The deviation between the actual steering angle and the target steering angle is evidence that the vehicle's position control and / or virtual driver is attempting to compensate for the trajectory deviation. This advantageously allows for particularly early detection of an unstable driving state. Preferably, understeer and / or oversteer is detected only when the actual steering angle deviates from the target steering angle by at least the steering angle tolerance value in a direction that counteracts the trajectory deviation. When the actual steering angle is set to compensate for trajectory deviation, the actual steering angle deviates from the target steering angle in a direction that counteracts the trajectory deviation. If the vehicle understeers, the actual steering angle deviates in a direction that counteracts the trajectory deviation if the actual steering angle is greater than the target steering angle in absolute value and has the same sign. Due to the steering angle tolerance, an unstable driving state is only detected early if the actual steering angle deviates significantly from the target steering angle. This minimizes the risk of false positives, for example due to measurement errors in determining the actual steering angle. This makes the method more robust.

[0026] Preferably, if the actual steering angle deviates from the target steering angle by at least a steering angle tolerance value and a trajectory deviation is determined, early identification of an unstable driving state includes: early identification of vehicle understeer if the trajectory deviation includes a lateral offset and a directional error toward the outside of the curve; and early identification of vehicle oversteer if the trajectory deviation includes a directional error toward the inside of the curve. The trajectory deviation preferably includes the vehicle's lateral offset and / or directional error. The directional error is the angle between the vehicle's desired target direction of motion on the target trajectory and the vehicle's actual direction of motion. The directional error can be an error in the heading angle. Preferably, the directional error is determined when the deviation between the target direction of motion and the actual direction of motion is 2° or greater. The inside of a curve is the side of the curve where the center of the curve radius is located. The outside of a curve is the side opposite the inside of the curve. Preferably, if the unstable driving state is oversteer, the degree of deceleration of at least one wheel is determined based on the directional error and / or the lateral offset. In the case of oversteer, the degree of deceleration is also preferably determined based on the vehicle's slip angle. The slip angle can be determined, for example and preferably, by integration based on the temporal profile of the yaw rate and the direction of motion of the vehicle. Preferably, the slip angle is determined based on a yaw rate deviation, in particular by temporal integration of the yaw rate deviation.

[0027] In a preferred refinement, the countersteering angle is determined based on a directional error directed toward the inside of the curve. Alternatively or in addition, the countersteering angle can also be determined based on a sideslip angle.

[0028] Preferably, the vehicle is an at least partially autonomous vehicle, wherein the target steering angle is determined by the vehicle's position controller, and wherein, upon detection of an unstable driving state, the vehicle is steered by a control unit of the vehicle control system. Preferably, upon detection of an unstable driving state, the control unit of the vehicle control system takes over control of the electronically controllable steering from the position controller. However, it is also possible for the control unit to be part of or contained within the position controller. Furthermore, the control unit may also be the vehicle's steering control unit. When the control unit provides the control unit with a steering request, which is then implemented by the steering unit, the control unit takes over control of the electronically controllable steering. Preferably, this takeover can be accomplished by assigning corresponding priorities so that the steering request provided by the control unit is implemented with priority over the steering request of the position controller.

[0029] Preferably, the steering angle correction is defined by a control unit of the vehicle control system. In the event of an unstable driving state, the steering angle correction is defined by a unit that also steers the vehicle. This allows the method to be executed particularly quickly. Furthermore, it is ensured that the vehicle is steered using the steering angle correction. However, it is also possible to provide the steering angle correction to a positioning controller, which then steers the vehicle using the steering angle correction.

[0030] According to another preferred embodiment, the method further comprises: determining whether the vehicle has reached a stable driving state; and if or as soon as the vehicle has reached a stable driving state, transferring the electronically controllable steering of the vehicle from the control unit of the vehicle control system to the vehicle's position controller. Once an unstable driving state is detected, the control unit of the vehicle control system takes over steering of the vehicle. Before the unstable driving state is detected, the vehicle's steering is typically performed by the position controller. Therefore, if instability occurs, the control unit of the vehicle control system preferably takes over the position controller. Once the vehicle has reached a stable driving state again, according to a preferred embodiment, the control unit of the vehicle control system transfers the electronically controllable steering of the vehicle to the position controller. A stable driving state is reached when understeer or oversteer is no longer present and / or when the trajectory deviation is within a tolerance corridor around the target trajectory. Therefore, a stable driving state may also be reached when the vehicle is not understeer or oversteer but still has a lateral deviation from the driving path of the target trajectory.

[0031] Preferably, the method includes reducing the vehicle's engine torque in response to early detection of an unstable driving state. Engine torque is torque provided by the vehicle's drive engine. Reducing the engine torque stabilizes the vehicle, thereby facilitating the vehicle's return to a stable state when the engine torque is reduced.

[0032] Furthermore, the vehicle is preferably a vehicle combination comprising a towing vehicle and at least one trailer vehicle, wherein the method further comprises braking the trailer vehicle in response to an early detection of an unstable driving state, wherein the braking of the trailer vehicle is preferably performed based on the jackknifing angle between the towing vehicle and the trailer vehicle. Braking the trailer vehicle can stabilize the vehicle and prevent the trailer vehicle from jackknifing (also known as "jackknifing"). Preferably, the trailer vehicle is braked independently, thereby implementing anti-jackknifing braking. Preferably, the trailer vehicle can also be decelerated in an alternative or additional manner, for example by recovering energy in a regenerator of the trailer vehicle.

[0033] In a second aspect, the present invention achieves the aforementioned object by a vehicle control system for a vehicle, in particular a commercial vehicle, having a control unit configured to execute the method according to the first aspect of the invention. Preferably, the vehicle control system itself can also be configured to execute the method according to the first aspect of the invention.

[0034] In a third aspect, the present invention achieves the aforementioned object by a vehicle control system for a vehicle, in particular a commercial vehicle, comprising a control unit connectable to a virtual driver of the vehicle for determining a target trajectory of the vehicle and an interface for connecting to an electronically controllable steering system of the vehicle. The control unit is configured to determine a target steering angle for driving along the target trajectory, to determine actual vehicle variables and, at least using the actual variables and the target trajectory, to determine oversteering or understeering of the vehicle. The control unit is further configured to determine a steering angle correction for the target steering angle in response to an early detection of an unstable driving state and to provide a control variable based on the steering angle correction and the target steering angle to the interface for the vehicle steering. If the unstable driving state is understeering of the vehicle, the steering angle correction includes a steering angle limitation of the steering angle that can be provided by the electronically controllable steering system, and if the unstable driving state of the vehicle is oversteering, the steering angle correction includes a countersteering angle directed opposite to the target steering angle. Preferably, the target steering angle can also be included in the target trajectory.

[0035] It will be understood that the vehicle control method according to the first aspect of the invention and the vehicle control system according to the second aspect of the invention and / or the vehicle control system according to the third aspect of the invention have identical or similar sub-aspects, as they are particularly described in the dependent claims. In this respect, for the preferred embodiments of the vehicle control system according to the second aspect and / or the third aspect of the invention, the above description of the vehicle control method according to the first aspect of the invention is also fully referenced. In particular, the vehicle control system according to the second aspect of the invention and / or the vehicle control system according to the third aspect of the invention is configured to perform the steps of the vehicle control method according to the first aspect of the invention.

[0036] In a fourth aspect, the object stated at the outset is achieved by a vehicle, in particular a commercial vehicle, having an electronically controllable steering system, a virtual driver for carrying out trajectory planning to obtain a target trajectory for the vehicle, and a vehicle control system according to the second and / or third aspect of the invention.

[0037] According to a fifth aspect of the present invention, the object stated at the outset is achieved by a computer program product having a program code source stored on a computer-readable data medium, so that when the computer program product is executed on a computing unit, the method according to the first aspect of the present invention is implemented. Preferably, the computing unit is a computing unit of a vehicle control system according to the second and / or third aspects of the present invention, particularly preferably a control unit.

[0038] Embodiments of the present invention are described below with the aid of the accompanying drawings. These figures do not necessarily represent the embodiments to scale; rather, the figures used for illustrative purposes are schematic and / or slightly distorted. For additional information regarding the teachings directly inferred from the drawings, reference is made to the relevant prior art. It should be noted that various modifications and alterations to the form and details of the embodiments are possible without departing from the overall concept of the present invention. The features of the present invention disclosed in the description, drawings, and claims are significant for further developments of the present invention, both individually and in any combination. Furthermore, all combinations of at least two features disclosed in the description, drawings, and / or claims fall within the scope of the present invention. The overall concept of the present invention is not limited to the exact form or details of the preferred embodiments shown and described below, nor to subject matter that is limited in comparison to the subject matter claimed in the claims. With respect to the specified measuring ranges, values within the stated limits are also disclosed as limit values and may be used arbitrarily and protected by the relevant patents. For the sake of clarity, identical or similar parts or parts having identical or similar functions are denoted by the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further advantages, features and details of the present invention can be gathered from the following description of preferred embodiments and based on the accompanying drawings, in which:

[0040] Figure 1 A vehicle is shown;

[0041] Figure 2a shows a vehicle understeering while negotiating a curve;

[0042] Figure 2b shows a vehicle oversteering while negotiating a curve;

[0043] Figure 3 A schematic flow chart illustrating a first embodiment of a vehicle control method is shown;

[0044] Figure 4 A schematic flow chart illustrating a second embodiment of a vehicle control method is shown;

[0045] Figure 5A graph illustrating curves of a target steering angle, an actual steering angle, a curvature of a curve, a lateral offset of the vehicle, and a directional error of the vehicle along a driving path for understeering is shown;

[0046] Figure 6 A diagram illustrating the course of the target steering angle, the actual steering angle, the curvature of the curve, the lateral offset of the vehicle, and the directional error of the vehicle along the driving path in the event of oversteering is shown. DETAILED DESCRIPTION

[0047] Figure 1 Vehicle 300 is shown, which is configured here as a vehicle combination 302. Vehicle combination 302 is a commercial vehicle comprising a tractor vehicle 304, which tows a trailer vehicle 306. A virtual driver 308 is provided to control vehicle 300. The virtual driver is configured to perform trajectory planning in order to obtain a target trajectory TSoll for vehicle 300. Target trajectory TSoll includes a driving path FP to be traveled by vehicle 300, which vehicle 300 is to follow according to target trajectory TSoll.

[0048] Vehicle 300 also includes an electronically controllable steering system 310, a drive engine 312, and a braking system 314, which is configured to decelerate wheels 316 of commercial vehicle 300. To decelerate wheels 316, braking system 314 includes brake actuators 318 associated with wheels 316. Brake actuators 318 control a braking slip at wheels 316, which corresponds to a brake pressure pB supplied to brake actuators 318. Brake pressure pB is in turn provided by a brake modulator 320 of braking system 314. A virtual driver 308 of vehicle 300 is connected to brake modulator 320 and provides it with a brake signal SB. Brake modulator 320 receives brake signal SB from virtual driver 308 and controls a corresponding brake pressure pB for brake actuators 318. It should be understood that brake pressure pB at wheels 316 may vary. Therefore, the brake pressure pB acting on the left front wheel 316a may be different from the brake pressure pB provided at the brake actuator 318 assigned to the right front wheel 316b of the vehicle 300. In addition, the brake system 314 is also configured to decelerate the trailer vehicle 306, wherein Figure 1 Only the brake actuator 318 of the towing vehicle 304 is shown.

[0049] In addition to trajectory planning, Figure 1The virtual driver 308 of the vehicle 300 shown in FIG is also configured as a positioning controller 322. The virtual driver 308 controls the vehicle 300 to travel along the driving path FP contained in the target trajectory TSoll under normal driving conditions. To this end, the virtual driver 308 controls the drive engine 312, the brake system 314 and the electronically controllable steering unit 310 so that the vehicle 300 travels along the driving path PF at the target speed VSoll contained in the target trajectory TSoll, wherein the target speed VSoll may vary along the driving path PF or may represent a speed profile. The virtual driver 308, the electronically controllable steering unit 310, the engine control unit ( Figure 1 314) and brake modulator 320 of brake system 314 are connected via vehicle network 324. To control vehicle 300, virtual driver 308 provides signals on vehicle network 324, which can then be received by the remaining units of vehicle 300. Vehicle network 324 is a bus system, namely the CAN bus of commercial vehicle 300.

[0050] Electronically controllable steering unit 310 receives steering signals SL provided by virtual driver 308 and steers vehicle 300 based on these steering signals SL. To this end, during normal operation, electronically controllable steering unit 310 controls an actual steering angle δIst for front wheels 316a, 316b of towing vehicle 304, corresponding to steering signals SL provided by virtual driver 308. Simultaneously, virtual driver 308 controls the longitudinal acceleration of vehicle 300 by sending corresponding signals to drive motor 312 and brake system 314.

[0051] The tractor vehicle 304 and the trailer vehicle 306 are connected by a drawbar 326, wherein the trailer vehicle 306 does not have its own drive but is towed by the tractor vehicle 304. The trailer vehicle 306 follows the tractor vehicle 304, wherein a tuck angle γ is formed between the tractor vehicle 304 and the trailer vehicle 306. During steady travel in a straight direction, the tuck angle γ has a value of 0°, since the trailer vehicle 306 travels straight behind the tractor vehicle 304. Figure 1 FIG. 3 shows that the folding angle γ between the towing vehicle 304 and the trailer wheels 306 is greater than 0°.

[0052] During stable driving, the virtual driver 308 controls the Figure 1. However, under certain circumstances, it may happen that the vehicle 300 becomes unstable and does not exhibit the driving behavior assumed within the scope of trajectory planning. This usually occurs in the case of unfavorable loading of the vehicle 300 or in poor road conditions. For example, there is a situation of unfavorable loading when the trailer vehicle 306 is fully loaded and the tractor vehicle 304 is empty. In this case, the vehicle 300 tends to become unstable because the trailer vehicle 306 may push the tractor vehicle 304 from behind. In addition, there is a deviation between the assumed driving behavior and the actual driving behavior when the loading condition of the trailer vehicle 306, which is configured as a saddle trailer, leads to an increased load on the rear axle of the tractor vehicle 304, which is configured as a saddle tractor, and thus causes understeering driving behavior. In addition, poor road conditions, such as slippery roads due to oil stains, sand or gravel or reduced friction between the tires of the vehicle 300 and the driving surface 334 (see Figure 2a 、 Figure 2b ) may result in the vehicle 300 being unable to follow the path FP included in the target trajectory TSoll.

[0053] Two unstable driving states 330 that may occur while vehicle 300 is driving around a bend are understeering 332 and oversteering 334 of vehicle 300 . Figure 2a and Figure 2b These unstable driving states 330 are illustrated in conjunction with the simplified illustration of vehicle 300 driving through a curve 336 (left curve). Figure 2a The vehicle 300 is shown to be understeering 332, while Figure 2b Oversteer 334 of vehicle 300 is illustrated.

[0054] exist Figure 2a , vehicle 300 is traveling from right to left through curve 336. Thus, curve start 338 is shown near the right edge of the figure, while curve end 340 is shown near the left edge of the figure. Figure 2aVehicle 300 is shown in an unstable driving state 330, shown simultaneously with vehicle 300 in a stable driving state 342, in which vehicle 300 ideally follows target trajectory T Soll. Vehicle 300 is shown in stable driving state 342 with lower contrast than unstable driving state 330. When entering curve 336, stable driving state 342 and unstable driving state 330 remain the same. In this unstable state, vehicle 300 cannot follow the course of curve 336 or target trajectory T Soll. During understeering 332, vehicle 300 deviates from the planned driving path FP, which precisely corresponds to the course of curve 336, toward the outside 346 of the curve. The lateral offset Q of vehicle 300 relative to driving path FP or target trajectory T Soll increases continuously from curve starting point 338 to curve end point 340. The actual yaw rate ΨIst of vehicle 300 is less than the target yaw rate ΨSoll, so that vehicle 300 turns into curve 336 less sharply than if it were to follow target trajectory TSoll. The directional error between the orientation of vehicle 300 during understeering 332 and the orientation of vehicle 300 in stable driving is It increases continuously towards the end of the curve 340.

[0055] Figure 2b The vehicle 300 is illustrated as being oversteering. Here, the vehicle 300 in the oversteering state 334 is compared to the vehicle 300 in the stable driving state 342 ( Figure 2b 334) is also shown. In the event of oversteering 334, vehicle 300 turns inward more strongly than is necessary for the current driving path FP. Even if the actual steering angle δ of vehicle 300 is less than the target steering angle δSoll or even points in the opposite direction, the actual yaw rate ΨIst of vehicle 300 in the event of oversteering 334 exceeds the target yaw rate ΨSoll required for driving through driving curve 336. In the event of oversteering 334, the directional error From the curve start 338 to the curve end 340, the yaw rate also increases continuously, but with a different sign than understeer 332. Thus, in the case of oversteer 334, the front of vehicle 300 is directed further toward the inside 344 of the curve than in the stable driving state 342, while in the case of understeer 332, the front of vehicle 300 is directed further toward the outside 346 of the curve than in the stable driving state 342. Since the actual yaw rate Ψ is too high compared to the target yaw rate ΨSoll, the rear of vehicle 300 skids in the case of oversteer 334. Figure 2b In the embodiment of FIG. 3 , the lateral offset Q of the vehicle 300 also increases toward the outer side 346 of the curve.

[0056] The virtual driver 308 continuously monitors the posture 348 of the vehicle 300. The posture 348 includes not only the position of the vehicle but also its orientation. If the virtual driver 308 detects a trajectory deviation ΔT, the virtual driver 308 attempts to return the vehicle 300 to the driving path FP of the target trajectory T Soll by appropriate control intervention. If the method 1 according to the present invention is not used, the virtual driver 308 will not be able to return the vehicle 300 to the driving path FP of the target trajectory T Soll. Figure 2b ), the actual steering angle δIst of vehicle 300 is continuously increased to compensate for the lateral deviation Q of vehicle 300 toward the outside of curve 346. The greater the lateral deviation Q of vehicle 300, the faster virtual driver 308 increases the actual steering angle δIst. If the adjustment of actual steering angle δIst by virtual driver 308 exceeds a predefined rate of change (i.e., the change in actual steering angle δIst per unit time), stability control system 350 of commercial vehicle 300 initiates a stability intervention. Stability control system 350 is an electronic stability control system ESC (see [Electronic Stability Control System]) connected to vehicle network 324. Figure 1 The ESC provides brake signals SB to vehicle network 324, which cause brake system 314 of vehicle 300 to control brake pressure pB at brake actuator 318 associated with front wheel 316b of vehicle 300, which is located on the outside of the curve. Brake actuator 318 decelerates right front wheel 316b. Figure 1 This deceleration is illustrated by arrow 355 .

[0057] ESC is an emergency system that only intervenes in the driving operation of the commercial vehicle 300 in a regulatory manner when a very large instability occurs. It is necessary to avoid ESC intervention in a stable driving state 342 because ESC can seriously undermine the safety of the vehicle 300 and may cause an accident. Therefore, the intervention threshold of ESC is selected to be very high, so that ESC intervention only occurs when there is a large instability of the vehicle 300. The selection of a higher ESC intervention threshold means that ESC stability intervention is only performed when the driving path FP of the vehicle 300 relative to the target trajectory TSoll has a very large lateral offset Q. However, the subsequent intervention of ESC brings the risk of the vehicle leaving the driving surface 328 and / or colliding with an obstacle due to increased space requirements. In the case of oversteering 334, ESC also intervenes only subsequently because erroneous intervention caused by measurement errors, for example, must be avoided. If no other system is provided, the virtual driver 308 is responsible for compensating the trajectory deviation ΔT, which here is the lateral offset Q and the directional error. , which will bring the above-mentioned disadvantages.

[0058] Therefore, vehicle 300 also includes a vehicle control system 200 having a control unit 202, which is also connected to vehicle network 324. Control unit 202 is configured to provide a brake signal SB and a steering signal SL for brake system 314 on vehicle network 324. Control unit 202 of vehicle control system 200 also receives a target trajectory TSoll from vehicle network 324, wherein target trajectory TSoll is provided by virtual driver 308 on vehicle network 324. However, in alternative embodiments, vehicle control system 200 or its control unit 202 can also be part of virtual driver 308.

[0059] The vehicle control system 200 is configured to implement the following reference Figure 3 and Figure 4 Explained vehicle control method 1. In the first step of method 1, the vehicle control system 200 learns the target trajectory TSoll of the vehicle 300 within the scope of learning 3. Learning 3 is performed in the following manner: the vehicle control system 200 receives the target trajectory TSoll planned by the virtual driver 308 from the vehicle network 324. After learning 3 the target trajectory TSoll, the target steering angle δSoll is learned 5. Figure 1 In vehicle 300, target steering angle δSoll is included in target trajectory TSoll. However, it can also be provided that electronically controllable steering unit 310 determines target steering angle δSoll based on target trajectory TSoll, for example, by calculating target steering angle δSoll based on the curvature of driving path FP and pre-stored geometric dimensions of vehicle 300.

[0060] In a further step, at least one actual variable 9 ( Figure 3 and Figure 4 Acquisition 7 in the embodiment of vehicle control method 1 shown. The actual steering angle δIst and the actual yaw rate ΨIst of vehicle 300 are determined while navigating curve 336. Acquisition 7 of actual variable 9 is performed based on a signal S provided on vehicle network 324. For example, the ESC provides a signal S representing the actual yaw rate ΨIst on vehicle network 324, and control unit 302 of vehicle control system 200 determines the actual yaw rate ΨIst based on this signal within the scope of acquisition 7. However, it is also possible that vehicle control system 200 includes a yaw rate sensor and / or a steering angle sensor. In the embodiment shown, acquisitions 3, 5, and 7 are performed sequentially. However, it is also possible that acquisition 7 of actual variable 9, acquisition 3 of target trajectory TSoll, and / or acquisition 5 of the target steering angle are performed completely or partially simultaneously, or that acquisition 7 is performed before acquisition 5 or acquisition 3.

[0061] While the target trajectory TSoll, the target steering angle δSoll, and the actual variable 9 are being determined 3, 5, and 7, the posture 348 of the vehicle 300 is also monitored 11. The virtual driver 308 continuously monitors the posture 348 of the vehicle 300 and provides corresponding signals S on the vehicle network 324. The control unit 202 of the vehicle control system 200 receives these signals S, so that the information corresponding to the posture 348 can also be processed by the control unit 202. In addition, the virtual driver 308 of the vehicle 300 also determines the trajectory deviation ΔT ( Figure 3 and Figure 4 The trajectory deviation ΔT is also contained in the signal S and can be used by the control unit 202. However, it can also be provided that the control unit 202 performs the monitoring 11 of the posture 348 and / or the determination 13 of the trajectory deviation ΔT. The control unit 202 determines the trajectory deviation change rate ΔTR ( Figure 3 and Figure 4 (See 15). The trajectory deviation change rate ΔTR represents the change in trajectory deviation ΔT over time. If the trajectory deviation change rate ΔTR increases, the trajectory deviation ΔT between vehicle 300's posture 348 and target trajectory TSoll also increases. Conversely, if the trajectory deviation change rate ΔTR decreases, the trajectory deviation ΔT decreases, and in this case, vehicle 300 approaches target trajectory TSoll.

[0062] After determining 15 the trajectory deviation change rate ΔTR and determining 7 the actual variable 9, an unstable driving state 330 of vehicle 300 is subsequently detected 17 in advance. Figure 3 In the vehicle control method 1, the unstable driving state 300 is detected in advance 17 by means of a yaw rate-based scheme, and Figure 4 The steering angle-based approach of method 1 has been explained. However, method 1 preferably includes both approaches. As a result, unstable driving state 300 can be predicted particularly reliably using vehicle control method 1 .

[0063] In accordance with Figure 3 In the yaw rate-based approach, advance identification 17 first includes determining 19 the target yaw rate ΨSoll. Control unit 202 determines the target yaw rate ΨSoll based on target trajectory TSoll. To this end, control unit 202 first determines 21 the curvature κ of target trajectory TSoll, where curvature κ is the curvature κ of curve 336. Furthermore, control unit 202 determines the actual speed VIst (V) of vehicle 300 as it negotiates curve 336. Figure 3After knowing the curvatures κ and the actual speed VIst 21, 23, and 25, the control unit 202 knows the target yaw rate ΨSoll based on these parameters.

[0064] In a further step of the vehicle control method 1 ( Figure 3 In the determination 27 in the method 1 , the control unit 202 of the vehicle control system 200 also determines the yaw rate difference ΔΨ between the actual yaw rate ΨIst and the target yaw rate ΨSoll based on the target yaw rate ΨSoll determined using the target trajectory TSoll and the actual actual yaw rate ΨIst occurring when driving through the curve 336. The yaw rate difference ΔΨ is a measure for measuring the degree of the unstable driving state 330. Therefore, in the case of oversteering 334, when the vehicle 300 turns significantly faster than expected to the inside 344 of the curve, the yaw rate difference ΔΨ is particularly large. The yaw rate difference ΔΨ is used in subsequent steps of the method 1 to determine the degree of deceleration 43 of the wheels 16 of the vehicle 300, but does not necessarily need to be determined when the unstable driving state 330 is detected 17 in advance. In the illustrated embodiment of the method 1, the yaw rate difference ΔΨ is determined when the unstable driving state 330 is detected 17 in advance. Figure 3 In the determination 29 , whether the absolute value of the actual yaw rate ΨIst is within a yaw rate tolerance band ΨTol around the target yaw rate ΨSoll is determined. If the determination 29 indicates that the absolute value of the actual yaw rate ΨIst is outside the yaw rate tolerance band ΨTol and the absolute value of the actual yaw rate ΨIst is less than the absolute value of the target yaw rate ΨSoll, it can be determined 332 that the vehicle 300 is understeering. Conversely, if the absolute value of the actual yaw rate ΨIst is outside the yaw rate tolerance band ΨTol and the absolute value of the actual yaw rate ΨIst is greater than the absolute value of the target yaw rate ΨSoll, it can be determined 334 that the vehicle 300 is oversteering.

[0065] The early detection 17 of the unstable driving state 330 can be performed solely on the basis of the above-mentioned yaw rate-based approach. However, in order to increase the robustness of the method 1 and to avoid erroneous detection of the unstable driving state 330, Figure 3In an embodiment of the method, early detection 17 also takes into account the trajectory deviation change rate ΔTR. Therefore, simultaneously with the aforementioned steps 19, 21, 23, 25, 27, and 29, it is also determined 31 whether the trajectory deviation ΔTR is increasing. If this is the case, i.e., if the trajectory deviation ΔT of vehicle 300 from target trajectory TSoll increases during the course of curve 336, unstable driving state 330 is detected. By taking into account the trajectory deviation change rate ΔTR, unstable driving state 330 is detected in advance only if the trajectory deviation ΔT is caused by unstable driving state 330. If the trajectory deviation ΔT is caused by other reasons, it is detected that unstable driving state 330 is not present. This situation may occur, for example, if vehicle 330 is already laterally offset Q toward the outside 346 of the curve relative to target trajectory TSoll at curve starting point 338. In this situation, virtual driver 308 attempts to compensate for lateral offset Q by controlling an actual steering angle δIst between curve start point 338 and curve end point 340. This actual steering angle δIst is greater than the target steering angle δSoll determined from target trajectory TSoll. Consequently, compared to a normal situation where there is no lateral offset Q at curve start point 338, actual yaw rate ΨIst is also greater than the corresponding target yaw rate ΨSoll. Determination 29 indicates that vehicle 300 is oversteering 334 because the absolute value of actual yaw rate ΨIst is greater than the absolute value of target yaw rate ΨSoll. However, as vehicle 300 simultaneously approaches target trajectory TSoll or driving path FP, trajectory deviation ΔT decreases, and trajectory deviation change rate ΔTR indicates a continuous decrease in trajectory deviation ΔT. Therefore, in this particular situation, it is determined that oversteering 334 is not occurring. Similarly, even though the absolute value of actual yaw rate ΨIst is less than the absolute value of target yaw rate ΨSoll, if trajectory deviation ΔT continues to decrease, it is determined that understeer 332 is not present. This is particularly the case when vehicle 300 has already entered curve 336 with a lateral offset Q toward the inside 344 of the curve.

[0066] Figure 4 A steering angle-based approach for early detection 17 of unstable driving state 330 is described. In the steering angle-based approach, the actual steering angle δIst controlled by virtual driver 308 in vehicle 300 when driving through curve 336 is compared with the target steering angle δSoll previously determined based on target trajectory TSoll ( Figure 4If the actual steering angle δIst deviates from the target steering angle δSoll by more than the steering angle tolerance value δTol, an unstable driving state 330 can be detected in advance, because this indicates that the virtual driver 308 is trying to compensate for the trajectory deviation ΔT. The steering angle tolerance value δTol is used to ensure that the already minimal deviation of the actual steering angle δIst from the target steering angle δSoll does not lead to the early detection 17 of an unstable driving state 330. For the same reason, in the case of the Figure 3 In the first embodiment of method 1, a yaw rate tolerance band ΨTol is considered.

[0067] In accordance with Figure 4 In the second embodiment of method 1, comparison 33 is also performed based on absolute values. Therefore, when performing target-actual comparison 35 between actual steering angle δIst and target steering angle δSoll, it is determined whether the absolute value of actual steering angle δIst is greater than or less than the absolute value of target steering angle δSoll. The advantage of performing the comparison based on absolute values is that vehicle control method 1 can be used, preferably unchanged, for both left and right turns.

[0068] In the case of understeering 332 and oversteering 334 of the vehicle 300, the vehicle 300 may deviate from the curve 336 toward the outer side 346 of the curve, and thus a lateral offset Q of the vehicle 300 relative to the target trajectory TSoll directed toward the outer side 346 of the curve occurs. In order to compensate for this lateral offset Q, the virtual driver 308 attempts to increase the actual steering angle δIst above the target steering angle δSoll in both the case of understeering 332 and oversteering 334. In order to distinguish between oversteering 334 and understeering 332, the method 1 according to the second embodiment also uses the acquired trajectory deviation ΔT. The trajectory deviation ΔT includes the lateral offset Q of the vehicle 300 relative to the target trajectory TSoll directed toward the outer side 346 of the curve and the directional error directed toward the outer side 346 of the curve. out, it is recognized in advance that the vehicle 300 is understeering 332 ( Figure 4 However, if the directional error toward the inside 344 of the curve is known when the lateral offset Q of the vehicle 300 is directed toward the outside 346 of the curve in, then oversteer 334 is detected in advance. In the case of oversteer 334, vehicle 300 turns more strongly toward the inside of the curve 344 than expected, which results in a directional error toward the inside of the curve 344. in.

[0069] According to Figure 3 Similarly, in the first embodiment of the vehicle control method 1, Figure 4In the vehicle control method 1, the advance identification 37, 39 is also verified by the trajectory deviation change rate ΔTR. Figure 4 In the method, unstable driving state 330 is only detected in advance when the trajectory deviation change rate ΔTR indicates an increasing trajectory deviation ΔT.

[0070] After the early identification 17 of an unstable driving state 330, the two embodiments of the vehicle control method 1 are essentially identical. In response to the early identification 17 of an unstable driving state 330, in both embodiments of the vehicle control method 1 according to the invention, a steering angle correction 41 is defined 39. In the case of understeering 332 of the vehicle 300, the defined steering angle correction 41 is a steering angle limitation δlim of the actual steering angle δIst that can be provided by the electronically controllable steering unit 310. The steering angle limitation δlim thus limits the actual steering angle δIst that can be provided to a maximum value. Here, the steering angle limitation δlim corresponds to the target steering angle δSoll plus the steering angle margin δzu. In the case of oversteering 334 of the vehicle (in Figure 3 and Figure 4 In the case of a vehicle with a high instability (as clarified by definition 40b), the steering angle correction 41 is a counter-steering angle δcs. Counter-steering angle δcs is directed opposite to target steering angle δsoll and toward the outside of curve 346. The magnitude of counter-steering angle δcs is preferably defined based on the degree of unstable driving state 330. Thus, in the case of a severe instability, such as may be characterized by a large yaw rate difference ΔΨ and / or a large deviation between the actual steering angle δIst and the target steering angle δsoll, a larger counter-steering angle δcs is preferably defined, and vice versa.

[0071] The steering angle limit δlim is equivalent to the target steering angle δsoll plus the steering angle margin δzu. The steering angle margin δzu can be a pre-stored value. However, in the embodiment of method 1, the steering angle margin δzu is determined based on the road surface information OI. The road surface information OI is included in the target trajectory TSoll and represents the adhesion characteristics of the driving surface 328. The control unit 202 of the vehicle control system 200 receives the target trajectory TSoll and determines the road surface information OI accordingly. The control unit 202 then uses this road surface information OI when defining 40a the steering angle correction 40a in the case of understeer 332. Therefore, when the road surface information OI represents a driving surface 328 with low adhesion, the steering angle margin δzu is relatively small because, in these cases, a further increase in the actual steering angle δIst, while relatively small in absolute value, does not provide any further improvement in the lateral guidance force of the wheels 316 of the vehicle 300. On the contrary, when the road surface adhesion is good or there is corresponding road surface information OI, the steering angle margin δzu can be larger. This is because lateral guiding force can still be provided even when the actual steering angle δIst is large.

[0072] In both embodiments of method 1, a wheel-specific deceleration 43 of the wheels 316 of the vehicle 300 is performed in parallel with the definition 39 of the steering angle correction 41. The wheel-specific deceleration 43 serves to provide an additional yaw moment on the vehicle 300 in order to increase the actual yaw rate ΨIst of the vehicle 300 in the case of understeer 332 or to reduce the actual yaw rate in the case of oversteer 334. Preferably, in the case of understeer 332, the wheel-specific deceleration 43 takes place at the wheels of the vehicle 300 on the inside of the curve, i.e. for Figure 2a For the curve 336 shown in FIG, this occurs at the front wheel 316a or the rear wheel 316c. The deceleration 43 in the case of understeering 332 is illustrated by arrows 352 and 354. In the case of oversteering 334, the front wheel 316a on the outside of the curve is preferably decelerated in order to thereby provide a turning moment on the vehicle 300 that counteracts the excessively high actual yaw rate ΨIst. Figure 1 The arrow 355 illustrates the Figure 2bDeceleration 43 of outer front wheel 316b in left-hand turn 336 is shown. Wheel-specific deceleration 43 preferably occurs asymmetrically across the axles of vehicle 300, thereby exerting a yaw moment. Consequently, wheels 316 on axles of vehicle 300 are preferably decelerated to varying degrees. Thus, in the event of understeer 332, for example, wheel 316a may be decelerated while wheel 316b is not. The degree of deceleration 43 for at least one wheel 316 is determined based on yaw rate deviation ΔΨ and / or the deviation between actual steering angle δIst and target steering angle δSoll. Thus, for example, in the event of oversteer 324, a particularly high brake pressure pB may be applied to brake actuator 318 assigned to front wheel 318b on the outside of the curve (in the case of left-hand turn 336) when yaw rate deviation ΔΨ is large, while a lower brake pressure pB may be applied when yaw rate deviation ΔΨ is small.

[0073] Figure 5 The effect of the steering angle correction 41 and, in particular, the wheel-specific or axle-specific deceleration 43 on the vehicle 300 in the event of understeering 332 is illustrated in diagram form. The diagram illustrates the course of the curvature κ of the driving path FP, the target steering angle δSoll, the actual steering angle δIst, the lateral offset Q, and the directional error. Curve along the driving path, wherein the vehicle 300 travels along a straight road section 356 before and after the curve 336. In the straight road section 356 before the curve 336, the actual steering angle δIst and the target steering angle are both equal to zero. The lateral offset Q and the direction error of the vehicle 300 are shown in FIG. It is also approximately equal to zero in the straight road section 356 before the curve 336. The lateral offset Q and the direction error in the straight section 356 are Small fluctuations are caused by incorrectly determining attitude 348 and, if necessary, corrections by virtual driver 308. At curve start 338, actual steering angle δIst increases approximately uniformly with target steering angle δSoll. Virtual driver 308 uses electronically controllable steering system 310 to control actual steering angle δIst in order to guide vehicle 300 along curve 336. Figure 5 The understeering 332 of the vehicle 300 is illustrated. The actual steering angle δIst corresponding to the target steering angle δSoll is insufficient to guide the vehicle 300 along the curve 336. The lateral offset Q of the vehicle 300 toward the outside 346 of the curve and the directional error toward the outside 346 of the curve are shown. This can be seen in the Figure 5This can be seen in the two lower lines of the graph shown in . To compensate for the lateral offset Q, the virtual driver 308 further increases the actual steering angle δIst and exceeds the maximum amount of the target steering angle δSoll. However, in the embodiment shown, further increasing the actual steering angle δIst is not necessary to compensate for the lateral offset Q and the directional error. This is undesirable because, due to poor road conditions, the vehicle 300 or its wheels 316 are unable to provide further lateral guiding force. If the actual steering angle δIst is too large, a sudden improvement in road conditions will result in a sudden increase in lateral guiding force, potentially causing the vehicle 300 to spin out. To prevent this, a steering angle limit δlim is defined in Method 1. Figure 5 To illustrate, the actual steering angle δIst that can be provided by the active steering unit 310 is constrained to be slightly higher than the target steering angle δSoll due to the steering angle limit δlim. This eliminates the risk of sudden vehicle instability caused by changes in road conditions. When the steering angle limit δlim is reached, the wheel 316 on the inner side of the curve of the vehicle 300 is decelerated and thus provides a yaw moment, thereby turning the vehicle 300 toward the inner side 344 of the curve. Figure 5 This deceleration is illustrated in FIG. 3 by providing a braking pressure pB. The lateral offset Q of the vehicle 300 and its directional error At the curve end 340 , the actual steering angle δIst is reduced and the wheel-specific deceleration 43 can be ended. Instead of decelerating the individual wheels 316 , an axle-specific deceleration can also be performed in the case of understeering 332 .

[0074] The wheel-specific deceleration 43 and the steering angle correction 41 stabilize the vehicle 300 during the travel through the curve 336. In addition, in response to the early detection 17 of understeering 332, the engine torque Mmot of the drive engine 312 is reduced ( Figure 3 and Figure 4 45). This further stabilizes vehicle 300.

[0075] and Figure 5 similar, Figure 6 The curvature κ of the travel path FP, the lateral offset Q of the vehicle 300, and the direction error of the vehicle 300 are shown. , the target steering angle δSoll of the vehicle 300 when traveling through the curve 336, and the change curve of the target steering angle δSoll of the vehicle 300 obtained when using the target trajectory TSoll. Figure 5 The difference is, Figure 6The curves of these variables are shown for the vehicle 300 in the case of oversteering 334 when driving through a curve 336. In a straight road section 356, the steering angle δ Soll, δ Ist, the lateral offset Q and the direction error At the start point 338 of the curve, the virtual driver 308 increases the actual steering angle δIst substantially uniformly to the target steering angle δSoll. As the vehicle 300 understeers, the direction error The lateral offset Q of vehicle 300 increases continuously toward the inside 344 of the curve. Simultaneously, the lateral offset Q of vehicle 300 increases toward the outside 346 of the curve. To compensate for this lateral offset Q, virtual driver 308 further increases actual steering angle δIst toward the inside 344 of the curve, thereby also exacerbating oversteer 334. However, in vehicle control method 1, a countersteering angle δcs is defined as a steering angle correction 41 and superimposed on the target steering angle δSoll. Countersteering angle δcs points in the opposite direction to target steering angle δSoll, thus pointing toward the outside 346 of the curve. Countersteering angle δcs is significantly greater than target steering angle δSoll, resulting in an actual steering angle δIst that also points toward the outside 346 of the curve. This compensates for understeer 334 and stabilizes vehicle 300. In addition to countersteering angle δcs, steering angle correction 41 also includes a steering angle limit δlim in the event of oversteer 334. This steering angle limit δlim ensures that countersteering angle δcs does not exceed the mechanical limit of approximately 45° of steering angle δ. This ensures that the return of actual steering angle δIst in the direction of the inside of the curve 344 does not take too long and that the mechanical constraints of the electronically controllable steering system 310 are adhered to. As described above, in the event of oversteer 334, as an additional stabilization measure, the engine torque Mmot of the drive engine 312 is reduced 45, and at least one wheel 316 of the vehicle 300 (preferably the front wheel on the outside of the curve in the event of oversteer 334) is decelerated 43 on a wheel-by-wheel basis. Figure 6 In FIG. 4 , the deceleration 43 is also illustrated by the profile of the brake pressure pB.

[0076] according to Figure 5 and Figure 6 The diagram of FIG. 1 illustrates that, after the early detection 17 of an unstable driving state 330, the vehicle 300 is steered using a steering angle correction 41. This steering 47 is shown in the flowchart diagrams of the first and second exemplary embodiments of the method 1 (see FIG. 1 ). Figure 3 and Figure 4In vehicle 300, upon detecting an unstable driving state 330, control unit 202 of vehicle control system 200 takes over electronically controllable steering system 310 from virtual driver 308. To steer vehicle 300 47, control unit 202 provides a steering signal SL on vehicle network 324 and actuates electronically controllable steering system 310 using steering angle correction 41. However, it is also possible for control unit 202 to provide steering angle correction 41 to virtual driver 308, and for virtual driver 308 to steer vehicle 300 47 using steering angle correction 41.

[0077] In both variants, it is ensured that steering angle correction 41 is taken into account when vehicle 300 steers 47 , for example, by corresponding signal prioritization. When vehicle 300 is steered 47 by virtual driver 308 using steering angle correction 41 in response to an early detection of an unstable driving state 330 , control unit 202 of vehicle control system 200 can be designed to be relatively simple and inexpensive. However, when control unit 202 takes over steering 47 in response to an early detection of an unstable driving state 330 using steering angle correction 41 , the fail-safety of vehicle 300 is improved because both virtual driver 308 and control unit 200 are designed to control electronically controllable steering 310 . Furthermore, responsiveness is improved because steering angle correction 41 is directly defined by the unit steering vehicle 300 (control unit 202 ). However, it should be understood that control unit 202 can also be designed to steer 47 when virtual driver 308 is responsible for steering 47 in response to an early detection 17 . Thus, if virtual driver 308 fails, control unit 202 can steer vehicle 300 , for example, using steering angle correction 41 .

[0078] As described above, the control unit 202 reacts to the early detection 17 of the unstable driving state 330 by Figure 1 The control unit 202 controls the vehicle 300 through the curve 336 and stabilizes the vehicle 300 by means of a combination of steering 47, reduction 45 of the engine torque Mmot of the drive engine 312, and wheel-specific deceleration 43. In addition, the control unit 202 causes the brake system 314 of the vehicle 300 to brake the trailer vehicle 306 ( Figure 3 and Figure 4The braking 53 in the tug-in braking system is achieved. The anti-tuck-in braking between the tractor vehicle 304 and the trailer vehicle 306 prevents the trailer vehicle 306 from tuck-in. The degree of braking 53 is determined by the control unit 202, optionally using the tuck angle γ. Preferably, the trailer vehicle 306 is braked more strongly when the tuck angle γ is large, i.e., when the trailer vehicle 306 and the tractor vehicle 304 have a significantly different orientation. When the tuck angle γ is small, i.e., when the trailer vehicle 306 and the tractor vehicle 304 have substantially the same orientation, the brake pressure pB at the brake actuator of the trailer vehicle 306 can be reduced.

[0079] After the vehicle 300 has driven through the curve 336, it returns to the straight road section 356. There, the vehicle 300 appears stable. Therefore, in the vehicle control method 1, a stable driving state 342 of the vehicle 300 is determined 49. Based on this determination 49, the control unit 202 returns the electronically controllable steering 310 of the vehicle 300 to the virtual driver 308, which is also the position controller 322 ( Figure 3 and Figure 4 The handover 51 in FIG. 3 is performed by the virtual driver 308 until the next unstable driving state 330 is detected 17 in advance.

[0080] List of reference numerals (part of the description)

[0081] 1 Vehicle Control Method

[0082] 3. Obtaining the target trajectory

[0083] 5. Obtain the target steering angle

[0084] 7 Get the actual parameters

[0085] 9 Actual parameters

[0086] 11 Monitoring vehicle posture

[0087] 13. Obtaining trajectory deviation

[0088] 15 Obtain trajectory deviation change rate

[0089] 17 Early recognition of unstable driving conditions

[0090] 19 Get the target yaw rate

[0091] 21 Obtaining the curvature of the target trajectory

[0092] 23 Get target speed

[0093] 27 Obtaining the yaw rate difference

[0094] 29 Know whether the absolute value of the actual yaw rate is within the yaw rate tolerance band

[0095] 31 Know whether the trajectory deviation change rate is increasing

[0096] 33 Perform a comparison of the actual steering angle with the target steering angle

[0097] 35 Target-Actual Comparison

[0098] 37 Early detection of understeer

[0099] 39 Early detection of oversteer

[0100] 40 Limited steering angle correction

[0101] 40a Limited steering angle correction in understeer

[0102] 40b Limits steering angle correction in oversteer situations

[0103] 41 Steering angle correction

[0104] 43 Wheel-Specific Deceleration

[0105] 45 Reduce engine torque

[0106] 47 Turn

[0107] 49 Acquire stable driving status

[0108] 51 Handover of steering

[0109] 53 Braking of trailer vehicles

[0110] 200 Vehicle Control Systems

[0111] 202 control unit

[0112] 300 vehicles

[0113] 302 Vehicle Combination

[0114] 304 Towing Vehicle

[0115] 306 trailer vehicles

[0116] 308 Virtual Driver

[0117] 310 Electronically controlled steering

[0118] 312 drive engine

[0119] 314 Braking System

[0120] 316 wheels

[0121] 316a Left front wheel

[0122] 316b right front wheel

[0123] 316c left rear wheel

[0124] 318 brake actuator

[0125] 320 Brake Modulator

[0126] 322 Positioning Regulator

[0127] 324 Vehicle Network

[0128] 326 drawbar

[0129] 328 driving road

[0130] 330 Unstable driving state

[0131] 332 Understeer

[0132] 334 Oversteer

[0133] 336 Bend

[0134] 338 starting point of the curve

[0135] 340 End of the curve

[0136] 342 Stable driving state

[0137] 344 Inside the curve

[0138] 346 Outside of the curve

[0139] 348 Posture

[0140] 350 Stability Control System

[0141] 351 Arrows illustrating deceleration of the rear wheel on the inside of a curve

[0142] 352 Arrows illustrating deceleration of the rear wheel on the outside of a curve

[0143] 354 Arrows illustrating deceleration of the front wheel on the inside of a curve

[0144] 355 Arrow illustrating deceleration of the front wheel on the outside of a curve

[0145] 356 straight road sections

[0146] ESC Electronic Stability Control System

[0147] FP driving path

[0148] Mmot engine torque

[0149] OI road information

[0150] pB brake pressure

[0151] SB brake signal

[0152] SL turn signal

[0153] TSoll target trajectory

[0154] ΔT trajectory deviation

[0155] ΔTR trajectory deviation change rate

[0156] VSoll target speed

[0157] γ folding angle

[0158] δIst actual steering angle

[0159] δsoll target steering angle

[0160] κ curvature

[0161] ΨIst actual yaw rate

[0162] Ψsoll target yaw rate

[0163] ΔΨ Yaw rate difference

[0164] Direction error

[0165] in Direction error pointing toward the inside of the curve

[0166] out Direction error pointing toward the outside of the curve

Claims

1. A vehicle control method (1) for a vehicle (300) having an electronically controllable steering unit (310), wherein: The vehicle control method (1) comprises: - Obtain (3) the target trajectory (T) of the vehicle (300) Soll ); - Know (5) for following the target trajectory (T Soll ) target steering angle (δ Soll ); - obtaining (7) actual parameters (9) of the vehicle (300); - early detection (17) of an unstable driving state (330) of the vehicle (300) at least using the actual variable (9) and the target trajectory (TSoll); wherein, during the advance identification (17), it is known whether the unstable driving state (330) is understeering (332) of the vehicle (300) or oversteering (334) of the vehicle (300); and In response to the early detection (17) of an unstable driving state (330): - defining (40) a steering angle correction (41) for the target steering angle (δSoll), wherein, if the unstable driving state (330) is understeering (332) of the vehicle (300), the steering angle correction (41) comprises a steering angle limitation (δlim) of an actual steering angle (δIst) that can be provided by the electronically controllable steering unit (310), and wherein, if the unstable driving state (330) of the vehicle (300) is oversteering (334), the steering angle correction (41) comprises a countersteering angle (δIst) directed opposite to the target steering angle (δSoll). CS );and - steering (47) the vehicle (300) using the steering angle correction (41).

2. The method (1) according to claim 1, further comprising: reacting to an early detection (17) of an unstable driving state (330), - performing a wheel-specific deceleration (43) of at least one wheel (316) of the vehicle (300).

3. The method (1) according to any one of claims 1 or 2, wherein If the unstable driving state (330) is understeering (332) of the vehicle (300), the steering angle limit (δlim) corresponds to the target steering angle (δSoll) plus a steering angle margin (δzu).

4. The method (1) according to claim 3, wherein: The steering angle margin (δzu) is determined using road surface information (OI) of a driving road (328) contained in the target trajectory (TSoll).

5. The method (1) according to any one of claims 1 to 4, further comprising: - monitoring (11) the posture (348) of the vehicle (300); - determining (13) a trajectory deviation (ΔT) of the vehicle (300) using the target trajectory (TSoll) and the monitored posture (348); and - Obtain (15) the trajectory deviation change rate (ΔTR).

6. The method (1) according to any one of claims 1 to 5, wherein The actual variable (9) is an actual yaw rate (ΨIst), and early detection (17) of an unstable driving state (330) of the vehicle (300) at least using the actual variable (9) and the target trajectory (TSoll) comprises: - determining (19) a target yaw rate (ΨSoll) of the vehicle (300) using the target trajectory (TSoll); and If the actual yaw rate (ΨIst) lies outside a yaw rate tolerance band (ΨTol) around the target yaw rate (ΨTol), an unstable driving state is detected ( 330 ).

7. The method (1) according to claim 6, wherein If the absolute value of the actual yaw rate (ΨIst) is below the yaw rate tolerance band (ΨTol), it is determined that the vehicle (300) is understeering (332); if the absolute value of the actual yaw rate (ΨIst) is above the yaw rate tolerance band (ΨTol), it is determined that the vehicle (300) is oversteering (334).

8. The method according to claims 5 and 7, wherein: Only when the trajectory deviation change rate (ΔTR) indicates that the trajectory deviation (ΔT) of the vehicle (300) from the target trajectory (TSoll) continues to increase, is it known that the vehicle (300) is understeering (332) or oversteering (334).

9. The method (1) according to claim 8, wherein Determining (19) a target yaw rate (ΨSoll) of the vehicle (300) using the target trajectory (TSoll) includes: - obtaining the curvature (κ) of the target trajectory (TSoll) as described in (21); - obtaining (23) the actual speed (VIst) of the vehicle (300); The target yaw rate (ΨSoll) is determined using at least the curvature (κ) of the target trajectory (TSoll) and the actual speed (VIst) of the vehicle (300).

10. The method (1) according to any one of claims 6 to 9, wherein The yaw rate tolerance band (ΨTol) has a width of ±0.1° / s to ±10° / s, preferably ±0.5° / s to ±2° / s, around the target yaw rate (ΨSoll).

11. The method (1) according to any one of claims 6 to 10, wherein If the unstable driving state (330) is oversteering (334), the countersteering angle (δ CS ).

12. The method (1) according to claim 5, wherein: The actual variable (9) is the actual steering angle (δIst) and early detection (17) of an unstable driving state (330) of the vehicle (300) at least using the actual variable (9) and the target trajectory (TSoll) comprises: - performing (33) a target-actual comparison (35) between the actual steering angle (δIst) and the target steering angle (δSoll); and If a trajectory deviation (ΔT) is determined and the actual steering angle (δIst) deviates from the target steering angle (δSoll) by at least a steering angle tolerance value (δTol), an unstable driving state (300) is detected (17) in advance.

13. The method (1) according to claim 12, wherein: If the actual steering angle (δIst) deviates from the target steering angle (δSoll) by at least a steering angle tolerance value (δTol) and a trajectory deviation (ΔT) is determined, early recognition (17) of an unstable driving state (330) includes: - If the trajectory deviation (ΔT) includes a lateral offset (Q) pointing toward the outside of the curve (346) and a directional error ( ), then understeering (332) of the vehicle (300) is recognized (37) in advance; and - If the trajectory deviation (ΔT) includes a directional error ( ), then an oversteering (334) of the vehicle (300) is detected (39) in advance.

14. The method (1) according to claim 13, wherein: Only when the trajectory deviation change rate (ΔTR) indicates that the trajectory deviation (ΔT) of the vehicle (300) from the target trajectory (TSoll) is continuously increasing, an understeer (332) and / or an oversteer (334) is detected in advance (37).

15. The method (1) according to claim 13 or 14, wherein Based on the direction error pointing to the inside of the curve ( ) to obtain the reverse steering angle (δcs).

16. The method (1) according to any one of claims 1 to 15, wherein The vehicle (300) is an at least partially automated vehicle (300), the target steering angle (δSoll) is determined by a positioning controller (322) of the vehicle (300), and the steering (47) of the vehicle (300) is carried out by a control unit (202) of a vehicle control system (200) as soon as an unstable driving state (330) is detected.

17. The method (1) according to claim 16, wherein: The steering angle correction (41) is defined (40) by a control unit (202) of the vehicle control system (200).

18. The method (1) according to claim 16 or 17, further comprising: - knowing (49) whether the vehicle (300) has reached a stable driving state (342); and - If a stable driving state (342) of the vehicle (300) is reached, the electronically controllable steering (310) of the vehicle (300) is handed over (51) from the control unit (202) of the vehicle control system (200) to the positioning controller (322) of the vehicle (300).

19. The method (1) according to any one of claims 1 to 18, further comprising: reacting to an early detection (17) of an unstable driving state (330), - reducing (45) the engine torque (M) of the vehicle (300) Mot ).

20. The method (1) according to any one of claims 1 to 19, wherein The vehicle (300) is a vehicle combination (302) having a towing vehicle (304) and at least one trailer vehicle (306), wherein the method (1) further comprises: reacting to an early detection (17) of an unstable driving state (330), - braking (53) the trailer vehicle (306), wherein the braking (53) of the trailer vehicle (306) is preferably performed based on a folding angle (γ) between the tractor vehicle (304) and the trailer vehicle (306).

21. A vehicle control system (200) for a vehicle (300), comprising a control unit (202) configured to execute the method (1) according to any one of claims 1 to 20.

22. A vehicle (300) having an electronically controllable steering portion (310), a virtual driver (308) configured to perform trajectory planning to obtain a target trajectory (TSoll) of the vehicle (300), and a vehicle control system (200) according to claim 21.

23. A computer program product comprising a program code source stored on a computer-readable data medium in order to carry out the method (1) according to claim 1 when the computer program product is executed on a computer.

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