Vehicle control method with steering angle correction

Abstract

The invention relates to a vehicle control method (1) having the steps of: carrying out an early detection (17) of an unstable driving state (330) of a vehicle (300) 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 understeering (332) of the vehicle (300) or an oversteering (334) of the vehicle (300), and in response to the early detection (17): defining (40) a steering angle correction (41) for a target steering angle (δSoll), said steering angle correction (41) comprising a steering angle limitation (δlim) of an actual steering angle (δlst), which can be provided, if the unstable driving state (330) is an understeering (232) of the vehicle (300) and a counter steering angle (öcs), which is directed opposite the target steering angle (δSoll), if the unstable driving state (330) of the vehicle (300) is an oversteering (334); and steering (47) the vehicle (300) using the steering angle correction (41). The invention additionally relates to a vehicle control system (200), to a vehicle (300), and to a computer program product.

Description

[0001] Hanover, January 13, 2023 IP, Bergmann, Fegers / MM SR 2023P00015DE 2022E00014DE

[0002] Vehicle control method with steering angle correction

[0003] The invention relates to a vehicle control method for a vehicle with electronically controllable steering. Furthermore, the invention relates to a vehicle control system, a vehicle, and a computer program product.

[0004] The autonomization of vehicles is one of the key areas of development in the modern automotive industry. Semi-autonomous vehicles take on partial tasks in controlling the vehicle, while autonomous vehicles are controlled entirely without human intervention. Autonomous vehicles control the lateral and longitudinal guidance of the vehicle completely independently of a human user. Semi-autonomous vehicles, on the other hand, only take on partial tasks in controlling the vehicle. As vehicles become increasingly autonomous, they are increasingly also taking on steering tasks, such as lane keeping or distance control. While autonomous vehicles always have electronically controlled steering, such steering can also be provided in semi-autonomous vehicles, for example, if the vehicle has a lane keeping assistant that automatically keeps the vehicle within a lane.An electronically controlled steering system controls the vehicle at least partially based on electrical signals.

[0005] For example, an autonomous control unit, also referred to as a virtual driver, can specify a steering request to the electronically controlled steering system, which then causes the vehicle to corner or steer the vehicle. For steering, the virtual driver can specify a steering request (e.g., a steering angle) to the electronically controlled steering system or provide a target trajectory to a steering controller, from which the steering controller then derives a corresponding steering request. The target trajectory includes at least the travel path that the vehicle is to follow. Furthermore, the target trajectory can also include other information, such as a speed profile, which specifies a target vehicle speed for one or more points along the travel path.Furthermore, the target trajectory can also include further target specifications, such as an orientation of the vehicle, in particular a heading angle, a yaw rate assigned to one or more points of the travel path and / or a steering angle.

[0006] Due to various influences, it may happen that the vehicle does not follow the specified target trajectory or that a trajectory deviation occurs. In this case, the vehicle does not move along the path encompassed by the trajectory, but rather offset from it or with a different orientation.

[0007] The virtual driver or a position controller of the vehicle, which can also be part of the virtual driver, attempts to compensate for a trajectory deviation using the electronically controllable steering, which can also be referred to as active steering. When cornering, if the vehicle veers laterally towards the outside of the curve, the position controller will attempt to compensate for this lateral deviation by turning more sharply (increasing the steering angle towards the inside of the curve). In the case of unfavorable road conditions, this will not succeed, as the vehicle does not respond to steering inputs as the position controller expects. For example, in unfavorable road and / or weather conditions, the vehicle may not be able to negotiate a given curve because the lateral forces built up between the vehicle's tires and the road surface are insufficient to guide the vehicle along the required curvature of the travel path against inertia.Particularly if yaw instability is already present, i.e., understeering or oversteering of the vehicle, the trajectory deviation may not be able to be compensated by increasing the steering input. Known virtual drivers and / or position controllers are not trained to safely control automated or autonomous vehicles in all situations. In cases where a known position controller cannot compensate for the trajectory deviation, the intervention of a conventional stability control system, such as Electronic Stability Control (ESC), is necessary. Due to the predefined intervention thresholds of stability control systems, such intervention only occurs when the vehicle exhibits significant instability and therefore very late. This increases the space required and increases the risk of accidents.Furthermore, in the event of instability, the vehicle may no longer respond to a change or variation in the steering angle, and further steering by the position controller may even worsen the vehicle's stability, especially in the case of understeering. Furthermore, countersteering too late and / or incorrectly, even in the case of an oversteering vehicle, can further worsen the vehicle's stability.

[0008] DE 10 2020 117 322 A1 discloses a vehicle system for a vehicle with an electronically controllable steering system. In the event of an electronic stability control system failing while driving, the electronically controllable steering system executes transverse-stabilizing steering interventions to keep the vehicle within a tolerance corridor of a predefined target trajectory. The steering interventions compensate for the loss of individual wheel braking on axles that are now controlled axle-by-axle due to the failure of the electronic stability control system. The system provides a fallback level if an electronic stability control system of a primary system is no longer available. The disclosed system thus relates to a fallback level for a conventional stability control system and does not allow for early stabilizing interventions.Furthermore, the steering interventions serve to keep the vehicle within a tolerance corridor so that a trajectory deviation is accepted.

[0009] There is a need for vehicle control methods that overcome the aforementioned disadvantages. The object of the present invention is to provide a vehicle control method in which instabilities are detected early and the vehicle is steered appropriately to the situation.

[0010] The invention solves the problem with a vehicle control method of the type mentioned above, comprising: determining a target trajectory for the vehicle; determining a target steering angle for traveling along the target trajectory; early detection of an unstable driving condition of the vehicle at least using the target trajectory; wherein, during the early detection, it is determined whether the unstable driving condition is understeering of the vehicle or oversteering of the vehicle; and in response to the early detection of the unstable driving condition: defining a steering angle correction for the target steering angle, wherein the steering angle correction comprises a steering angle limitation of an actual steering angle that can be provided by the electronically controllable steering system if the unstable driving condition is understeering of the vehicle, and wherein the steering angle correction comprises a countersteering angle opposite to the target steering angle if the unstable driving condition of the vehicle is oversteering.and steering the vehicle using the steering angle correction. The invention is based, on the one hand, on the idea that unstable driving conditions can be detected early using the target trajectory, and, on the other hand, on the recognition that the measures taken by a position controller and / or virtual driver to compensate for an unstable driving condition may be unsuitable for resolving the unstable driving condition. Dangerous situations can be prevented through early intervention. The steering angle correction corrects the steering angle associated with the target trajectory. As a result of the steering angle correction, the vehicle can be stabilized and / or the steering angle correction prevents steering interventions that promote the unstable driving condition.

[0011] The target trajectory is preferably provided by a unit for autonomous driving, in particular a virtual driver, for example via a vehicle bus. The vehicle control method preferably comprises carrying out trajectory planning to obtain the target trajectory. The target steering angle is the steering angle of the vehicle that the virtual driver or another autonomous unit predicts for traveling the target trajectory, wherein the virtual driver assumes stable driving behavior of the vehicle. The target steering angle is preferably included in the target trajectory. The target trajectory then includes not only the path to be traveled, but also the target steering angle predicted for traveling this path. The target steering angle is preferably determined on a model-based basis. For example, when determining the target trajectory, the virtual driver can determine a predefined target steering angle 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 a vehicle speed or a vehicle speed profile while traveling along the target trajectory, whereby the speed and / or the speed profile can be included in the target trajectory. The actual variable is a variable that occurs while traveling along the trajectory or in the driving situation to which the target trajectory belongs.

[0012] The early detection of an unstable driving condition of the vehicle occurs at least using the actual variable and the desired trajectory. In contrast to previously known methods, instabilities can thus be detected not only when various vehicle sensors report significant actual deviations from predefined threshold values. The desired trajectory is taken into account according to the invention and allows the detection of instability adapted to the respective driving situation. For example, an unstable driving condition can be detected early, for example, when the actual variable deviates by more than a tolerance value from the desired trajectory or from a variable derived from the desired trajectory. The unstable driving condition can be oversteering or understeering of the vehicle. Oversteering and understeering are common terms used to describe the driving behavior of vehicles.When understeering, the vehicle's self-steering gradient is greater than zero, meaning it requires more steering effort to follow a curve than with a neutral vehicle. Oversteer is often colloquially referred to as a vehicle skidding.

[0013] The steering angle correction is defined in response to the early detection of unstable driving conditions. In the event of understeer, the steering angle correction includes a steering angle limitation of the available actual steering angle. In the event of understeer, the vehicle deviates from the planned driving path on the outside of bends. In an effort to follow the planned driving path, the vehicle's position controller will continuously increase the actual steering angle, i.e. turn more sharply. The target steering angle, which would be necessary for stable driving, is exceeded. Above a certain limit for the slip of the front wheels, however, this is no longer useful because the tires can no longer generate any further lateral guidance forces. This is often the case when the grip between the tires and the road surface is reduced, for example in wet or slippery conditions.If the grip between the tires and the road surface suddenly increases again at a large actual steering angle, the steered wheels suddenly build up high lateral forces, and the vehicle can become uncontrollable. The method according to the invention defines a steering angle limitation in the event of understeer, thus eliminating this risk. The vehicle is steered using the steering angle correction, so that no actual steering angle can be specified that exceeds a sensible or safe value. For example, the steering angle limitation can be a limitation of the maximum actual steering angle that can be provided by the electronically controlled steering system to 30°.

[0014] In the event of oversteer, the vehicle turns more sharply than necessary to follow the current path. In doing so, the vehicle usually also deviates from the planned path. However, the position controller and / or autonomous driver must not primarily orient the steering angle of the oversteering vehicle based on the vehicle's offset from the planned path in order to return to it. For example, if the vehicle veers sideways towards the outside of a bend, orienting itself solely on the position deviation would result in the actual steering angle being increased further in the direction of the bend, which would further intensify the oversteer. Instead, the vehicle's reaction should be adapted to the excessive yaw rate and appropriately dampened by countersteering. In the method according to the invention, this is achieved by the steering angle correction comprising a countersteering angle that is opposite to the target steering angle, which is directed towards the inside of bends.When steering the vehicle using steering angle correction, the countersteering angle counteracts the target steering angle, stabilizing the vehicle. The countersteering angle counteracting the target steering angle has a sign opposite to the actual steering angle. For example, if the actual steering angle is positive (measured counterclockwise), the countersteering angle is a negative angle (measured clockwise).

[0015] In a first preferred embodiment, the method, in response to the early detection of the unstable driving condition, further comprises: wheel-specific deceleration of at least one wheel of the vehicle. In addition to the steering angle correction, the method in the preferred embodiment therefore additionally comprises individual deceleration of at least one wheel of the commercial vehicle. This wheel-specific deceleration preferably serves to provide a yaw moment on the vehicle. Thus, as a result of the steering angle limitation or other factors, such as a low coefficient of friction between the vehicle and the road surface, the yaw rate of the vehicle that can be achieved by steering can be limited. The wheel-specific deceleration can compensate for a difference between a target yaw rate and the yaw rate adjustable by the steering system. To decelerate the wheel, brake slip is preferably applied to the wheel to be decelerated.This can be done, for example, by providing brake pressure to a brake actuator assigned to the wheel. However, the wheel to be decelerated can also be decelerated by recuperation, for example. A wheel decelerated individually is decelerated independently of the other wheels of the vehicle. However, it can be provided that two or more wheels of the vehicle are decelerated simultaneously to the same extent. For example, all wheels oriented towards a curve center (i.e. all wheels on the inside of the curve) of a vehicle can be decelerated to the same extent. Of course, only a single wheel can be decelerated. For example, to compensate for oversteer, an outer front wheel of the vehicle on the curve can be decelerated in order to provide a yaw moment to counteract the oversteer. The necessary manipulated variable for deceleration and / or the selection of the correct wheel is preferably carried out using the target trajectory and the actual variable.Unlike conventional stability control (ESC), where the strength of intervention is controlled solely by the steering, a target value is also taken into account. Wheel-specific deceleration preferably provides an additional yaw moment that acts in the direction of the steering angle correction. In the event of understeer, the steering angle correction or steering angle limitation acts in the direction of the target steering angle. The steering angle correction therefore counteracts the vehicle yawing outwards when cornering. In the event of oversteer, the countersteering angle acts outwards so that the yaw moment provided by wheel-specific deceleration counteracts excessive vehicle rotation when cornering inwards. Wheel-specific deceleration is preferably not applied axle by axle. Wheels of the commercial vehicle belonging to the same axle are therefore preferably not decelerated uniformly.

[0016] Preferably, the at least one wheel of the vehicle is an inside wheel of the commercial vehicle, in particular the inside rear wheel of the commercial vehicle, if the unstable driving condition of the commercial vehicle is understeering. The at least one wheel of the commercial vehicle is preferably an outside wheel of the commercial vehicle, in particular an outside wheel on the front axle, if the unstable driving condition of the commercial vehicle is oversteering.

[0017] Furthermore, it is preferred that the steering angle limitation corresponds to the target steering angle plus a steering angle allowance if the unstable driving condition is vehicle understeering. By considering a fixed or variable steering angle allowance, the steering angle limitation can be defined particularly easily. The steering angle allowance is preferably determined taking the target trajectory into account. Thus, the steering angle allowance can be selected to be larger for a steeply curved driving path or high speeds than for a target trajectory that corresponds to slow vehicle travel. The target steering angle is preferably an Ackermann steering angle, which is determined from a radius of curvature of the trajectory and a wheelbase of the vehicle. The target steering angle can preferably also take into account a force buildup of the tires.It can therefore be provided that the target steering angle takes into account a run-in distance of the tire when cornering, which is required to build up the lateral guidance forces in the contact area between the tire and the road surface.

[0018] According to a further preferred embodiment, the steering angle supplement is determined using surface information of a roadway, which is preferably included in the target trajectory. The target trajectory can, for example, include surface information that characterizes a slippery roadway with a significantly reduced coefficient of friction. However, it can also be provided that the surface information is provided separately. An optimal slip angle, at which the vehicle's wheels can achieve maximum lateral guidance of the vehicle, depends on the surface of the roadway or a coefficient of friction between the vehicle's wheels and the roadway traveled by the vehicle. On icy roads, the optimal slip angle has a lower value than on a rough, dry roadway. Thus, on icy roads, no further lateral guidance forces can be built up even at low actual steering angles.The steering angle limitation is therefore preferably stronger on icy roads and the steering angle supplement is lower than on dry roads, since a further increase in the steering angle may no longer be sensible even at comparatively small steering angles.

[0019] The method preferably further comprises: monitoring a position of the vehicle; determining a trajectory deviation of the vehicle using the desired trajectory and the monitored position; and determining a trajectory deviation change rate. When monitoring the position of the vehicle, the position of the vehicle is preferably determined continuously or at discrete time intervals. By monitoring the position, a change in the position of the vehicle can be determined. The position preferably comprises the position of the vehicle. Furthermore, the position can alternatively or additionally also comprise an orientation of the vehicle, in particular a heading angle. The heading angle refers to an angle between the geographical north direction and the target direction of the vehicle. For example, if the vehicle is traveling east, the vehicle moves at a heading angle of 90°. However, the heading angle can also be an angle in a vehicle-fixed coordinate system.The trajectory deviation is a deviation of the vehicle's position from the trajectory. The trajectory deviation is or preferably includes a position deviation of the vehicle between an actual position of the vehicle and a desired position of the vehicle on the travel path. An example of a position deviation is a transverse offset of the vehicle from the travel path transverse to the direction of travel. However, the trajectory deviation can also be or include a course angle deviation between an actual course angle of the vehicle and a desired course angle. The trajectory deviation change rate indicates the temporal change of the trajectory deviation. The trajectory deviation change rate preferably describes the change in the trajectory deviation over a specific period of time in relation to the duration of this period. The period under consideration is preferably short.The duration of the period is preferably 10 s (seconds) or less, preferably 8 s or less, preferably 6 s or less, preferably 5 s or less, preferably 4 s or less, preferably 3 s or less, preferably 2 s or less, preferably 1 s or less. An increasing trajectory deviation is an indication that an unstable driving condition exists. An increasing trajectory deviation change rate occurs, for example, when the vehicle understeers when cornering and, as a result, a transverse offset of the vehicle (i.e. an offset of the vehicle transverse to the travel path) steadily increases. Determining the trajectory deviation change rate allows particularly simple early detection of the unstable driving condition. Thus, starting from a condition in which the vehicle is traveling on the travel path, the occurrence of even a small position deviation causes an increasing trajectory deviation change rate.Thus, an unstable driving condition can be detected even with small absolute trajectory deviations and / or when a virtual driver may not have yet intervened in the steering. Conventional stability control systems react to steering interventions, meaning that these stability control systems can only detect unstable driving conditions once steering is initiated. Unstable driving conditions can therefore be detected considerably earlier using a trajectory deviation change rate than with conventional stability control systems. However, it should be understood that determining a trajectory deviation change rate is a preferred and not a necessary step in the early detection of an unstable driving condition using the desired trajectory.

[0020] In a preferred development, the actual variable is an actual yaw rate, and the early detection of an unstable driving state of the vehicle, at least using the actual variable and the desired trajectory, comprises: determining a desired yaw rate for the vehicle using the desired trajectory; determining an actual yaw rate for the vehicle; and determining an unstable driving state if the actual yaw rate lies outside a yaw rate tolerance band around the desired yaw rate. Preferably, determining an 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 can also be determining the actual yaw rate using signals provided on a vehicle network, preferably a vehicle bus, particularly preferably a CAN bus.For example, and preferably, a stability control system, in particular an ESC control unit, can provide signals representing the actual yaw rate of the vehicle to the vehicle network. The yaw rate tolerance band defines a value range around the target yaw rate. The target yaw rate is a yaw rate of the vehicle that is predicted for the target trajectory. Preferably, a deceleration measure for decelerating the 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 measure is preferably a slip request for the at least one wheel.

[0021] Preferably, understeering of the commercial vehicle is determined if the magnitude of the actual yaw rate lies below the yaw rate tolerance band, and oversteering of the vehicle is determined if the magnitude of the actual yaw rate lies above the yaw rate tolerance band. The actual yaw rate lies below the yaw rate tolerance band if the magnitude of the actual yaw rate is less than the magnitude of the target yaw rate and the actual yaw rate is not within the yaw rate tolerance band. Analogously, the actual yaw rate lies above the yaw rate tolerance band if the magnitude of the actual yaw rate is greater than the magnitude of the target yaw rate and the actual yaw rate is not within the yaw rate tolerance band. The actual yaw rate and the target yaw rate are preferably considered in terms of their magnitude. If the magnitude of the actual yaw rate is below the yaw rate tolerance band, the vehicle is understeering. If, on the other hand, the magnitude of the actual yaw rate is above the yaw rate tolerance band, the vehicle is oversteering.The advantage of the quantitative analysis is that the method is applicable to left and right turns.

[0022] In a preferred development, understeer or oversteer is only detected if the trajectory deviation change rate indicates an increasing trajectory deviation of the vehicle from the target trajectory. According to the preferred development, understeer is therefore only detected if the actual yaw rate is below the yaw rate tolerance band and the trajectory deviation is increasing. Similarly, in the preferred development, oversteer is only detected if the actual yaw rate is above the yaw rate tolerance band and the trajectory deviation is increasing. This makes the detection of an unstable driving condition more robust, and the risk of incorrect detection is minimized.For example, error averaging can be excluded in cases where the vehicle already enters a curve with a lateral deviation from the path covered by the target trajectory, but then follows the curve stably with a constant lateral deviation.

[0023] Preferably, determining the target yaw rate for the vehicle using the target trajectory comprises: determining a curvature of the target trajectory; determining an actual speed of the vehicle; and determining the target yaw rate using at least the curvature of the target trajectory and the actual speed of the vehicle.

[0024] The yaw rate tolerance band preferably has a width of ± 0.1 7s to ± 10 7s, preferably ± 0.1 ° / s to ± 8° / s, preferably ± 0.3° / s to ± 8° / s, preferably ± 0.3° / s to ± 67s, preferably ± 0.3° / s to ± 57s, 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 ± 37s, preferably ± 0.5° / s to ± 27s, around the value of the desired yaw rate. Preferably, the yaw rate tolerance band has a width 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 ± 1.57s or less, around the value of the desired yaw rate.If, for example, the target yaw rate has a magnitude of 107s and the yaw rate tolerance band has a width of ±1.57s, then an unstable driving condition is determined if the magnitude of the actual yaw rate is less than or equal to 8.57s (understeer) or if the magnitude of the actual yaw rate is greater than or equal to 11.57s (oversteer). Preferably, the yaw rate tolerance band can also be determined dynamically. For example, the yaw rate tolerance band can preferably be defined as a function of the curvature of the target trajectory, with a large curvature resulting in a wide yaw rate tolerance band and a small curvature resulting in a narrow yaw rate tolerance band. Preferably, the yaw rate tolerance band has a minimum width which is not undercut even if the target trajectory has no curvature (on a straight stretch).In one variant, the countersteer angle is determined using a yaw rate deviation between the actual yaw rate and the target yaw rate if the unstable driving condition is oversteer. The yaw rate deviation is preferably determined from the magnitude of the actual yaw rate and the magnitude of the target yaw rate. The yaw rate deviation is then independent of the cornering direction. By using the yaw rate deviation to determine the countersteer angle, oversteer can be counteracted particularly effectively. A large yaw rate deviation then also requires a large countersteer angle. For example, if the vehicle skids sharply, strong countersteering is also applied.

[0025] According to a preferred embodiment, the actual variable is the actual steering angle, and the early detection of an unstable driving condition of the vehicle, at least using the actual variable and the desired trajectory, comprises: performing a desired-actual comparison between the actual steering angle and the desired steering angle; and early detection of the unstable driving condition if a trajectory deviation is determined and the actual steering angle deviates from the desired steering angle by at least a steering angle tolerance value. It should be understood that the early detection of an unstable driving condition can be based on the actual steering angle and on the actual yaw rate. For example, an unstable driving condition can only be determined if the actual yaw rate lies outside the yaw rate tolerance band and the actual steering angle deviates from the desired steering angle by the steering angle tolerance value.A deviation between the actual steering angle and the target steering angle is an indication that the position controller and / or virtual driver of the vehicle is attempting to compensate for a trajectory deviation. In this way, an unstable driving condition can advantageously be detected particularly early. Preferably, early detection of understeer and / or oversteer only occurs when the actual steering angle deviates from the target steering angle by at least a steering angle tolerance value in a direction counteracting the trajectory deviation. The actual steering angle deviates from the target steering angle in a direction counteracting the trajectory deviation if the actual steering angle is intended to compensate for the trajectory deviation. When the vehicle understeers, the actual steering angle deviates in a direction counteracting the trajectory deviation if the actual steering angle is greater in magnitude than the target steering angle and has the same sign.Thanks to the steering angle tolerance value, only significant deviations between the actual steering angle and the target steering angle lead to early detection of the unstable driving condition. This minimizes the risk of false detections, for example, due to measurement errors when determining the actual steering angle. The process becomes more robust.

[0026] Preferably, the early detection of the unstable driving condition, 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, comprises: early detection of understeering of the vehicle if the trajectory deviation includes a lateral deviation directed outwards towards curves and a directional error directed outwards towards curves; and early detection of oversteering of the vehicle if the trajectory deviation includes a directional error directed inwards towards curves. The trajectory deviation preferably includes a lateral deviation of the vehicle and / or a directional error of the vehicle. The directional error is an angle between a required target direction of movement of the vehicle on the target trajectory and an actual direction of movement of the vehicle. The directional error can be an error in the heading angle.The directional error is preferably determined if the deviation between the desired direction of movement and the actual direction of movement is 2° or more. The inside of a curve is that side of a curve on which the center of the curve radius of the curve lies. The outside of a curve is the side opposite the inside of the curve. The degree of deceleration of the at least one wheel is preferably determined based on the directional error and / or the lateral offset if the unstable driving condition is oversteering. In the event of oversteering, the degree of deceleration can preferably also be determined based on a sideslip angle of the vehicle. The sideslip angle can, for example and preferably, be determined by integration based on a time profile of the yaw rate and a direction of movement of the vehicle. The sideslip angle is preferably determined based on the yaw rate deviation, in particular by temporal integration of the yaw rate deviation.

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

[0028] Preferably, the vehicle is an at least partially autonomous vehicle, wherein the target steering angle is determined by a position controller of the vehicle, and wherein the steering of the vehicle is performed by a control unit of a vehicle control system as soon as an unstable driving condition is detected. Preferably, the control unit of the vehicle control system takes over the electronically controllable steering from the position controller as soon as an unstable driving condition is detected. However, it can also be provided that the control unit is part of the position controller or is included in the position controller. Furthermore, the control unit can also be a steering control unit of the vehicle. The control unit takes over the electronically controllable steering when it provides steering requests to the controller, which are then executed by the steering system.The takeover can preferably be carried out by assigning a corresponding priority so that steering requests provided by the control unit are executed preferentially to steering requests of the position controller.

[0029] Preferably, the steering angle correction is defined by the control unit of the vehicle control system. In the event of an unstable driving condition, the steering angle correction is then defined by the unit that also steers the vehicle. This allows the method to be carried out particularly quickly. Furthermore, it is ensured that the vehicle is steered using the steering angle correction. However, it can also be provided that the steering angle correction is provided to the position controller, and the position controller steers the vehicle using the steering angle correction.

[0030] According to a further preferred embodiment, the method further comprises: determining whether a stable driving state of the vehicle has been reached, and transferring the electronically controllable steering of the vehicle from the control unit of the vehicle control system to the position controller of the vehicle if or as soon as a stable driving state of the vehicle is reached. The control unit of the vehicle control system takes over steering the vehicle as soon as an unstable driving state is detected. Before the unstable driving state is detected, the vehicle is generally steered by the position controller. The control unit of the vehicle control system therefore preferably replaces the position controller of the vehicle as soon as instability occurs. As soon as the vehicle reaches a stable driving state again, the control unit of the vehicle control system, according to the preferred embodiment, transfers the electronically controllable steering of the vehicle to the position controller.A stable driving condition is achieved when understeer or oversteer no longer exists and / or when a trajectory deviation lies within a tolerance corridor around the target trajectory. For example, a stable driving condition may not yet be achieved even if the vehicle is not understeering or oversteering but still exhibits a transverse deviation from the target trajectory.

[0031] Preferably, the method comprises reducing the vehicle's engine torque in response to the early detection of the unstable driving condition. The engine torque is a torque provided by a drive motor of the vehicle. Reducing the engine torque has a stabilizing effect on the vehicle, thus facilitating the return of the vehicle to a stable state with reduced engine torque.

[0032] Furthermore, it is preferred that the vehicle is a vehicle combination with a towing vehicle and at least one trailer vehicle, wherein the method, in response to the early detection of the unstable driving condition, further comprises: braking the trailer vehicle, wherein the braking of the trailer vehicle is preferably carried out based on an articulation angle between the towing vehicle and the trailer vehicle. Braking the trailer vehicle stabilizes the vehicle and jackknifing of the trailer vehicle, which is also referred to as jackknifing, can be prevented. Preferably, the trailer vehicle is braked in isolation, such that stretch braking is carried out. Preferably, the trailer vehicle can also be decelerated in an alternative or supplementary manner, for example by recovering energy in a recuperator of the trailer vehicle.

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

[0034] In a third aspect, the object mentioned at the outset is achieved by a vehicle control system for a vehicle, in particular a commercial vehicle, comprising a control unit which can be connected to a virtual driver of the vehicle in order to determine a desired trajectory for the vehicle and which has an interface for connection to an electronically controllable steering system of the vehicle; wherein the control unit is designed to: determine a desired steering angle for traveling along the desired trajectory; determine an actual variable of the vehicle and determine oversteering or understeering of the vehicle at least using the actual variable and the desired trajectory;wherein the control unit is further configured, in response to the early detection of the unstable driving condition, to determine a steering angle correction for the target steering angle and to provide a control variable based on the steering angle correction and the target steering angle at the interface for steering the vehicle. The steering angle correction comprises a steering angle limitation of the steering angle that can be provided by the electronically controllable steering system if the unstable driving condition is understeering of the vehicle, and the steering angle correction comprises a countersteering angle opposite to the target steering angle if the unstable driving condition of the vehicle is oversteering. The target steering angle can preferably also be included in the target trajectory.

[0035] It should be understood that the vehicle control method according to the first aspect of the invention as well as 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 the same or similar sub-aspects, as set out in particular in the dependent claims. In this respect, for preferred embodiments of the vehicle control system according to the second and / or third aspect of the invention, reference is made in full to the above description of the vehicle control method according to the first aspect of the invention. 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 designed to carry out the steps of the vehicle control method according to the first aspect of the invention.

[0036] In a fourth aspect, the object mentioned above is achieved by a vehicle, in particular a commercial vehicle, having an electronically controllable steering system, a virtual driver configured to carry out trajectory planning to obtain a desired trajectory for the vehicle, and a vehicle control system according to the second aspect of the invention and / or according to the third aspect of the invention. According to a fifth aspect of the invention, the object mentioned above is achieved by a computer program product having program code means stored on a computer-readable data carrier for executing the method according to the first aspect of the invention when the computer program product is executed on a computing unit. Preferably, the computing unit is a computing unit, particularly preferably the control unit, of a vehicle control system according to the second and / or third aspect of the invention.

[0037] Embodiments of the invention will now be described below with reference to the drawings. These are not necessarily intended to represent the embodiments to scale; rather, the drawings are schematic and / or slightly distorted where this is useful for explanation. With regard to additions to the teachings immediately apparent from the drawings, reference is made to the relevant prior art. It should be noted that numerous modifications and changes to the form and detail of an embodiment can be made without deviating from the general idea of ​​the invention. The features of the invention disclosed in the description, in the drawings and in the claims can be essential for the further development of the invention, both individually and in any combination.Furthermore, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of ​​the invention is not limited to the exact form or detail of the preferred embodiments shown and described below, or limited to an object that would be more limited than the object claimed in the claims. For specified dimensioning ranges, values ​​within the stated limits are also intended to be disclosed as limit values ​​and to be used and claimed as desired. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar functions.

[0038] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings, which show: Fig. 1 a vehicle;

[0039] Fig. 2a shows a vehicle understeering when negotiating a curve;

[0040] Fig. 2b shows a vehicle oversteering when negotiating a curve;

[0041] Fig. 3 is a schematic flowchart illustrating a first embodiment of a vehicle control method;

[0042] Fig. 4 is a schematic flowchart illustrating a second embodiment of a vehicle control method;

[0043] Fig. 5 is a diagram showing the course of a target for understeer.

[0044] 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 travel path; and in

[0045] Fig. 6 is a diagram illustrating the course of the target steering angle, the actual steering angle, the curvature of the curve, the lateral deviation of the vehicle and the directional error of the vehicle along the travel path for an oversteer.

[0046] Fig. 1 shows a vehicle 300, which is embodied here as a vehicle combination 302. The vehicle combination 302, which is a commercial vehicle, comprises a towing vehicle 304 that pulls a trailer vehicle 306. A virtual driver 308 is provided to control the vehicle 300. The virtual driver 308 is configured to perform trajectory planning to obtain a target trajectory Ttarget for the vehicle 300. The target trajectory Ttarget comprises the travel path FP to be traveled by the vehicle 300, which the vehicle 300 is to follow according to the target trajectory Ttarget.

[0047] The vehicle 300 further includes an electronically controllable steering system 310, a drive motor 312, and a braking system 314 provided for decelerating wheels 316 of the commercial vehicle 300. To decelerate the wheels 316, the braking system 314 has brake actuators 318 assigned to the wheels 316. The brake actuators 318 control a brake slip of the wheels 316, which corresponds to a brake pressure pB provided to the brake actuators 318. The brake pressure pB is in turn provided by a brake modulator 320 of the braking system 314. The virtual driver 308 of the vehicle 300 is connected to the brake modulator 320 and provides braking signals SB thereto. The brake modulator 320 receives the brake signals SB from the virtual driver 308 and controls corresponding brake pressures pB for the brake actuators 318. It should be understood that the brake pressures pB of the wheels 316 can vary.A brake pressure pB at a left front wheel 316a may therefore be different from a brake pressure pB provided at the brake actuator 318 associated with a right front wheel 316b of the vehicle 300. Furthermore, the braking system 314 is also provided for decelerating the trailer vehicle 306, although only brake actuators 318 of the towing vehicle 304 are shown in Fig. 1.

[0048] In addition to trajectory planning, the virtual driver 308 of the vehicle 300 shown in Fig. 1 is configured as a position controller 322. The virtual driver 308 controls the vehicle 300 in a regular driving situation along the travel path FP encompassed by the desired trajectory Tdesired. To this end, the virtual driver 308 controls the drive motor 312, the braking system 314, and the electronically controllable steering system 310 such that the vehicle 300 follows the travel path PF at a desired speed Vdesired encompassed by the desired trajectory Tdesired. The desired speed Vdesired can vary along the travel path PF or can represent a speed profile. The virtual driver 308, the electronically controllable steering 310, an engine control unit of the drive motor 312 (not shown in Fig. 1) and the brake modulator 320 of the brake system 314 are connected by means of a vehicle network 324.To control the vehicle 300, the virtual driver 308 provides signals on the vehicle network 324, which can then be received by the other units of the vehicle 300. The vehicle network 324 is a bus system, namely a CAN bus of the commercial vehicle 300.

[0049] The electronically controlled steering system 310 receives steering signals SL provided by the virtual driver 308 and steers the vehicle 300 according to these steering signals SL. To this end, the electronically controlled steering system 310, in normal operation, controls an actual steering angle ölst at the front wheels 316a, 316b of the towing vehicle 304 that corresponds to the steering signals SL provided by the virtual driver 308. Simultaneously, the virtual driver 308 controls the longitudinal acceleration of the vehicle 300 by sending corresponding signals to the drive motor 312 and the braking system 314.

[0050] The towing vehicle 304 and the trailer vehicle 306 are connected by means of a drawbar 326, wherein the trailer vehicle 306 does not have its own drive and is pulled by the towing vehicle 304. The trailer vehicle 306 follows the towing vehicle 304, whereby a bending angle y is established between the towing vehicle 304 and the trailer vehicle 306. During stationary travel in a straight direction, the bending angle y has a value of 0°, since the trailer vehicle 306 is traveling directly behind the towing vehicle 304. In Fig. 1, a bending angle y of greater than 0° is shown between the towing vehicle 304 and the trailer vehicle 306.

[0051] During stable driving, the virtual driver 308 alone controls the fully autonomous vehicle 300 shown in Fig. 1. In certain situations, however, the vehicle 300 may become unstable and not exhibit the driving behavior assumed during trajectory planning. This is often the case when the vehicle 300 is unfavorably loaded or when road conditions are poor. An unfavorable load occurs, for example, when the trailer vehicle 306 is fully loaded while the towing vehicle 304 is empty. In this case, the vehicle 300 is prone to instability because the trailer vehicle 306 can push the towing vehicle 304 from behind.Furthermore, a deviation between the assumed driving behavior and actual driving behavior may occur, for example, if a loading situation of a trailer vehicle 306 configured as a semi-trailer leads to an increased rear axle load of a towing vehicle 304 configured as a tractor unit, thus causing understeering. Furthermore, poor road conditions, such as slippery roads or reduced friction between the tires of the vehicle 300 and a roadway 328 (cf. Fig. 2a, 2b) due to an oil slick, sand, or loose chippings, may result in the vehicle 300 being unable to follow the driving path FP encompassed by the target trajectory Ttarget.

[0052] Two unstable driving conditions 330 that can occur during cornering of the vehicle 300 are understeer 332 and oversteer 334 of the vehicle 300. Fig. 2a and Fig. 2b illustrate these unstable driving conditions 330 using a simplified representation of the vehicle 300 negotiating a curve 336 (left turn). Fig. 2a shows understeer 332 of the vehicle 300, while Fig. 2b illustrates oversteer 334 of the vehicle 300.

[0053] In Fig. 2a, vehicle 300 travels through curve 336 from right to left. A curve start 338 is therefore shown near the right edge of the image, while a curve end 340 is located near the left edge of the image. Fig. 2a shows vehicle 300 in the unstable driving state 330, which is superimposed on vehicle 300 in a stable driving state 342, in which vehicle 300 ideally follows the target trajectory Ttarget. In the stable driving state 342, vehicle 300 is shown with lower contrast compared to the unstable driving state 330. When entering curve 336, the stable driving state 342 and the unstable driving state 330 are still identical. In the unstable case, vehicle 300 cannot follow the course of curve 336 or the target trajectory Ttarget. During understeer 332, the vehicle 300 deviates to the outside 346 of the curve from the planned travel path FP, which corresponds exactly to the course of the curve 336. A lateral offset Q of the vehicle 300 to the travel path FP orto the desired trajectory TSoll increases continuously from the curve entry 338 to the curve exit 340. An actual yaw rate 'T'actual of the vehicle 300 is less than a desired yaw rate ^Soll, so that the vehicle 300 turns less into the curve 336 than desired to follow the desired trajectory TSoll. A directional error cp between the orientation of the vehicle 300 during understeer 332 and the stable vehicle 300 increases towards the curve exit 340.

[0054] Fig. 2b illustrates an oversteering vehicle 300. Here, the vehicle 300 during oversteer 334 is also superimposed on a vehicle 300 in a stable driving state 342 (shown with lower contrast in Fig. 2b). During oversteer 334, the vehicle 300 turns more sharply than would be necessary for the current driving path FP. Even if the actual steering angle θ of the vehicle 300 is smaller than a desired steering angle θdesired, or even points in the opposite direction, the actual yaw rate 'T'actual of the vehicle 300 during oversteer 334 exceeds the desired yaw rate ^desired, which would be required to negotiate the curve 336. The directional error cp also increases continuously during oversteer 334 from the corner entry 338 to the corner exit 340, but has a different sign compared to understeer 332.Thus, during oversteering 334, a front of the vehicle 300 points further towards the inside 344 of the curve than in the stable driving state 342, whereas during understeering 332 the front of the vehicle 300 is directed further towards the outside 346 of the curve than in the stable driving state 342. This is due to the actual yaw rate being excessive compared to the desired yaw rate M^desired. the rear of the vehicle 300 breaks out during oversteer 334. In the embodiment according to Fig. 2b, a transverse offset Q of the vehicle 300 towards the outside of the curve 346 also increases.

[0055] The virtual driver 308 continuously monitors a position 348 of the vehicle 300. The position 348 includes both a position and an orientation of the vehicle. As soon as the virtual driver 308 detects a trajectory deviation AT, the virtual driver 308 attempts to return the vehicle 300 to the travel path FP of the desired trajectory TSoll by means of appropriate control interventions. Without the method 1 according to the invention, the virtual driver 308 would continuously increase the actual steering angle ölst of the vehicle 300 during oversteering 332 (Fig. 2b) in order to compensate for the lateral deviation Q of the vehicle 300 towards the outside 346 of the curve. The greater the lateral deviation Q of the vehicle 300 becomes, the faster the virtual driver 308 would increase the actual steering angle ölst. As soon as this adjustment of the actual steering angle ölst by the virtual driver 308 reaches a predefined rate of change (ieIf the actual steering angle exceeds the change in the actual steering angle ölst per unit of time, a stability control system 350 of the commercial vehicle 300 intervenes to stabilize the vehicle. The stability control system 350 here is an Electronic Stability Control ESC that is connected to the vehicle network 324 (see Fig. 1). The ESC provides brake signals SB on the vehicle network 324, which cause the brake system 314 of the vehicle 300 to apply a brake pressure pB to the brake actuator 318 assigned to the outer front wheel 316b of the vehicle 300 on the curve. The brake actuator 318 decelerates the right front wheel 316b. This deceleration is illustrated in Fig. 1 by the arrow 355.

[0056] The ESC is an emergency system that only intervenes in the driving operation of the commercial vehicle 300 when very large instabilities occur. ESC interventions in the stable driving state 342 must be avoided, as these would significantly impair the safety of the vehicle 300 and could lead to accidents. The ESC intervention threshold is therefore selected very high, so that only large instabilities of the vehicle 300 lead to ESC intervention. The high ESC intervention thresholds mean that stabilizing intervention by the ESC only occurs late, for example when the vehicle 300 already has a very large transverse deviation Q from the travel path FP of the target trajectory TSet. However, the late intervention of the ESC entails the risk that the vehicle will leave the roadway 328 and / or collide with an obstacle due to the increased space requirement.The ESC also intervenes late in the event of oversteer 334, as incorrect interventions, which could result, for example, from measurement errors, must be avoided. If no other system is provided, it is the responsibility of the virtual driver 308 to compensate for a trajectory deviation AT, which in this case is the lateral offset Q and the directional error cp, which entails the aforementioned disadvantages.

[0057] The vehicle 300 therefore additionally comprises a vehicle control system 200, which has a control unit 202, which is also connected to the vehicle network 324. The control unit 202 is configured to provide braking signals SB for the braking system 314 and steering signals SL on the vehicle network 324. Furthermore, the control unit 202 of the vehicle control system 200 receives the target trajectory T from the vehicle network 324, wherein the target trajectory T is provided by the virtual driver 308 on the vehicle network 324. In alternative variants, the vehicle control system 200 or its control unit 202 can also be part of the virtual driver 308.

[0058] The vehicle control system 200 is designed to carry out the vehicle control method 1 explained below with reference to Fig. 3 and Fig. 4. In a first step of the method 1, the vehicle control system 200 determines the target trajectory TSoll for the vehicle 300 as part of a determination 3. Here, the determination 3 takes place in that the vehicle control system 200 receives the target trajectory TSoll planned by the virtual driver 308 from the vehicle network 324. Following the determination 3 of the target trajectory TSoll, the target steering angle öSoll is determined 5. In the vehicle 300 according to Fig. 1, the target steering angle öSoll is included in the target trajectory TSoll.However, it can also be provided that the electrically controllable steering system 310 determines the desired steering angle öSoll from the desired trajectory TSoll, for example by the electrically controllable steering system 310 calculating the desired steering angle öSoll from the curvature of the travel path FP and pre-stored geometric dimensions of the vehicle 300.

[0059] In a further step, at least one actual variable 9 is determined (determination 7 in Fig. 3 and Fig. 4). In the illustrated embodiment of the vehicle control method 1, the actual steering angle ölst and the actual yaw rate '4 Jactual of the vehicle 300 when negotiating the curve 336. The determination 7 of the actual variables 9 is carried out here based on signals S provided on the vehicle network 324. For example, the ESC provides a signal S representing the actual yaw rate Ist on the vehicle network 324, from which the control unit 302 of the vehicle control system 200 determines the actual yaw rate '- actual as part of the determination 7. However, it can also be provided that the vehicle control system 200 has a yaw rate sensor and / or a steering angle sensor. In the exemplary embodiment shown, the determination steps 3, 5, 7 take place sequentially. However, it can also be provided that the determination 7 of the actual variable 9, the determination 3 of the target trajectory TSoll and / or the determination 5 of the target steering angle take place entirely or partially simultaneously, or that the determination 7 takes place before the determination 5 or the determination 3.

[0060] Simultaneously with the determination 3, 5, 7 of the desired trajectory TSoll, the desired steering angle θSoll, and the actual variables 9, the position 348 of the vehicle 300 is monitored 11. The virtual driver 308 continuously monitors the position 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 information corresponding to the position 348 can also be processed by the control unit 202. In addition, the virtual driver 308 of the vehicle 300 determines the trajectory deviation ΔT of the vehicle 300 from the desired trajectory TSoll using the desired trajectory TSoll and the position 348 (determination 13 in Fig. 3 and Fig. 4). The trajectory deviation AT is also included in the signals S and is available at the control unit 202.However, it can also be provided that the control unit 202 carries out the monitoring 11 of the position 348 and / or the determination 13 of the trajectory deviation AT. Using the trajectory deviation AT, the control unit 202 determines a trajectory deviation change rate ATR (determination 15 in Fig. 3 and Fig. 4). The trajectory deviation change rate ATR characterizes the temporal change of the trajectory deviation AT. If the trajectory deviation change rate ATR increases, the trajectory deviation AT of the position 348 of the vehicle 300 from the desired trajectory Tdesired increases. In contrast, if the trajectory deviation change rate ATR decreases, the trajectory deviation AT decreases, so that the vehicle 300 in this case approaches the desired trajectory Tdesired. Following the determination 15 of the trajectory deviation change rate ATR and the determination 7 of the actual variables 9, an early detection 17 of an unstable driving state 330 of the vehicle 300 takes place.In the vehicle control method 1 according to Fig. 3, the early detection 17 of the unstable driving condition 300 is carried out using a yaw rate-based approach, while Fig. 4 illustrates a steering angle-based approach of the method 1. However, the method 1 preferably includes both approaches. This allows an unstable driving condition 300 to be predicted particularly reliably using the vehicle control method 1.

[0061] In the yaw rate-based approach according to Fig. 3, the early detection 17 initially comprises determining 19 a target yaw rate '4 J Target. The control unit 202 determines the target yaw rate M JThe target value here is based on the target trajectory T. For this purpose, the control unit 202 first determines 21 a curvature K of the target trajectory T, where the curvature K here is the curvature K of the curve 336. Furthermore, the control unit 202 determines an actual speed Vlst at which the vehicle 300 travels through the curve 336 (determination 23 in Fig. 3). After determining 21, 23, 25 the curvature K and the actual speed Vlst, the control unit 202 determines the target yaw rate MJSoll from these variables.

[0062] From the target yaw rate M determined using the target trajectory TSoll J Target and the real actual yaw rate 'T'lst occurring when driving through the curve 336, the control unit 202 of the vehicle control system 200 determines in a further step of the vehicle control method 1 (determination 27 in Fig. 3) a yaw rate difference A'T' between the actual yaw rate 'T'lst and the target yaw rate M JDesired. The yaw rate difference A'T' is a measure of the severity of the unstable driving condition 330. Thus, the yaw rate difference A'T' is particularly large during oversteering 334 when the vehicle 300 turns significantly faster 344 on the inside of curves than desired. The yaw rate difference A'T' is used in a later step of method 1 to determine the severity of a deceleration 43 of a wheel 16 of the vehicle 300, but does not necessarily have to be determined for the early detection 17 of the unstable driving condition 330. In the illustrated embodiment of method 1, for the early detection 17 of the unstable driving condition 330, it is determined (determination 29 in Fig. 3) whether the magnitude of the actual yaw rate 'T'actual lies within a yaw rate tolerance band 'T'Tol around the desired yaw rate MJdesired. If the determination 29 shows that the amount of the actual yaw rate 'T'lst is outside the yaw rate tolerance band 'T'Tol, and that the amount of the actual yaw rate '- lst is smaller than the amount of the target yaw rate '4J Target, then an understeer 332 of the vehicle 300 can be determined. If the amount of the actual yaw rate '4 J is outside the yaw rate tolerance band M J Tol and the amount of the actual yaw rate ' J lst is greater than the magnitude of the target yaw rate '4 J However, if desired, an oversteer 334 of the vehicle 300 can be determined.

[0063] The early detection 17 of the unstable driving state 330 could be based solely on the yaw rate-based approach described above. However, in order to increase the robustness of method 1 and avoid false detections of unstable driving states 330, the early detection 17 in the exemplary embodiment of the method according to Fig. 3 also takes into account the trajectory deviation change rate ATR. Thus, simultaneously with the previously described steps 19, 21, 23, 25, 27, 29, a determination 31 is also made as to whether the trajectory deviation ATR is increasing. If this is the case, i.e., if a trajectory deviation AT of the vehicle 300 from the desired trajectory Tdesired increases over the course of the curve 336, an unstable driving state 330 is detected. By taking into account the trajectory deviation change rate ATR, unstable driving conditions 330 are only detected early if a trajectory deviation AT results from an unstable driving condition 330.If, however, the trajectory deviation AT is due to other causes, then no unstable driving condition 330 is detected. This is the case, for example, if the vehicle 330 already has a lateral offset Q from the desired trajectory Tdesired to the outside of the curve 346 at the beginning of the curve 338. In such a situation, the virtual driver 308 will attempt to compensate for the lateral offset Q by controlling an actual steering angle ölst between the beginning of the curve 338 and the end of the curve 340 that is greater than the desired steering angle ödesired determined from the desired trajectory Tdesired. As a result, the actual yaw rate 'T'actual is also greater than the corresponding desired yaw rate 'T'desired compared to the normal case without lateral offset Q at the beginning of the curve 338. The determination 29 indicates an oversteer 334 of the vehicle 300, since the magnitude of the actual yaw rate 'T' actual is greater than the magnitude of the desired yaw rate 'T' desired. However, since the vehicle 300 simultaneously follows the desired trajectory T desired orAs the vehicle approaches the travel path FP, the trajectory deviation AT decreases, and the trajectory deviation change rate ATR indicates a decreasing trajectory deviation AT. In this special case, therefore, no oversteer 334 is determined. Similarly, despite an absolute value of the actual yaw rate 'T' actual being less than an absolute value of the desired yaw rate 'T' desired, no understeer 332 is determined if the trajectory deviation AT decreases. This is particularly the case if the vehicle 300 is already entering the curve 336 with a lateral offset Q to the inside 344 of the curve.

[0064] Fig. 4 illustrates the steering angle-based approach for the early detection 17 of an unstable driving condition 330. In the steering angle-based approach, a comparison is made between the actual steering angle ölst, which is controlled by the virtual driver 308 on the vehicle 300 when negotiating the curve 336, and the target steering angle öSoll previously determined based on the target trajectory TSoll (step 33 in Fig. 4). If the actual steering angle ölst deviates from the target steering angle öSoll by more than a steering angle tolerance value öTol, an unstable driving condition 330 can be detected early, since this indicates that the virtual driver 308 is attempting to compensate for a trajectory deviation ΔT. The steering angle tolerance value ÖTol serves to ensure that even the smallest deviations of the actual steering angle ölst from the target steering angle öSoll do not lead to early detection 17 of an unstable driving condition 330. For the same reason, in the first embodiment of method 1 according to Fig.3 the yaw rate tolerance band 'T'Tol is taken into account.

[0065] In the second exemplary embodiment of method 1 according to Fig. 4, the comparison 33 is also based on the magnitude. Thus, when performing the target-actual comparison 35 between the actual steering angle ölst and the target steering angle öSoll, it is determined whether the magnitude of the actual steering angle ölst is greater or smaller than the magnitude of the target steering angle öSoll. The magnitude-based comparison offers the advantage that the vehicle control method 1 can be used for both left-hand and right-hand bends, preferably without modification.

[0066] In both the case of understeer 332 and oversteer 334 of the vehicle 300, it is likely that the vehicle 300 will be carried out of the curve 336 to the outside 346 of the curve, resulting in a lateral deviation Q of the vehicle 300 from the desired trajectory Tdesired, which is directed towards the outside 346 of the curve. To compensate for this lateral deviation Q, the virtual driver 308 will attempt, in both the case of understeer 332 and oversteer 334, to increase the actual steering angle ölst beyond the desired steering angle ödesired. To distinguish between oversteer 334 and understeer 332, method 1 according to the second exemplary embodiment further uses the determined trajectory deviation AT.In the event that the trajectory deviation AT includes a transverse deviation Q of the vehicle 300 directed towards the outside 346 of the curve from the desired trajectory TSoll and a directional error (pout) directed towards the outside 346 of the curve, an understeer 332 of the vehicle 300 is detected early (early detection 37 in Fig. 4). If, however, a directional error (pin) towards the inside 344 of the curve is determined when the vehicle 300 is transversely deviated from the outside 346 of the curve, an early detection 39 of an oversteer 334 occurs. During oversteer 334, the vehicle 300 turns more strongly towards the inside 344 of the curve than desired, which results in the directional error (pin) directed towards the inside 344 of the curve.

[0067] Analogous to the first exemplary embodiment of the vehicle control method 1 according to Fig. 3, the early detection 37, 39 is also verified by the trajectory deviation change rate ATR in the vehicle control method 1 according to Fig. 4. Thus, in the method according to Fig. 4, an unstable driving condition 330 is also only detected early if the trajectory deviation change rate ATR indicates an increasing trajectory deviation AT.

[0068] Following the early detection 17 of an unstable driving condition 330, the two exemplary embodiments of the vehicle control method 1 are essentially identical. In response to the early detection 17 of the unstable driving condition 330, a steering angle correction 41 is defined 39 in both exemplary embodiments of the vehicle control method 1 according to the invention. In the event of understeer 332 of the vehicle 300, the defined steering angle correction 41 is a steering angle limitation ölim of the actual steering angle ölst that can be provided by the electronically controllable steering system 310. The steering angle limitation ölim thus limits the available actual steering angle ölst to a maximum value. The steering angle limitation ölim here corresponds to the desired steering angle öSoll plus a steering angle allowance özu. In the case of oversteer 334 of the vehicle (illustrated in Fig. 3 and Fig. 4 as defining 40b), the steering angle correction 41 is a countersteering angle öcs.The countersteering angle öcs is directed opposite the desired steering angle öSoll and points outwards 346 of the curve. The magnitude of the countersteering angle öcs is preferably defined based on the severity of the unstable driving condition 330. Thus, in the case of severe instability, which may be characterized, for example, by a large yaw rate difference A^P and / or by a large deviation between the actual steering angle ölst and the desired steering angle öSoll, a large countersteering angle öcs is preferably defined, and vice versa. The steering angle limitation ölim corresponds to the desired steering angle öSoll plus the steering angle allowance özu. The steering angle allowance özu can be a pre-stored value. In the exemplary embodiments of method 1, however, the steering angle allowance özu is determined based on surface information Ol. The surface information Ol is included in the desired trajectory TSoll and represents grip properties of the road surface 328.The control unit 202 of the vehicle control system 200 receives the desired trajectory TSoll and determines therefrom the surface information Ol.

[0069] The control unit 202 then uses this surface information Ol when defining 40a the steering angle correction 40a in the case of understeer 332. Thus, the steering angle supplement özu is comparatively small if the surface information Ol represents a road surface 328 with low grip, since in such cases a further increase in the actual steering angle ölst does not provide a further increase in the cornering forces of the wheels 316 of the vehicle 300, even with comparatively small absolute values. However, with a well-adhering road surface or corresponding surface information Ol, the steering angle supplement özu can be large, since cornering forces can still be provided even with large actual steering angles ölst.

[0070] In parallel with the definition 39 of the steering angle correction 41, in both embodiments of method 1, a wheel-specific deceleration 43 of a wheel 316 of the vehicle 300 takes place. The wheel-specific deceleration 43 serves to provide an additional yaw moment on the vehicle 300 in order to increase the actual yaw rate 'T'lst of the vehicle 300 in the case of understeer 332 or to reduce it in the case of oversteer 334.

[0071] Preferably, the wheel-specific deceleration 43 during understeer 332 occurs at an inside wheel of the vehicle 300, i.e., for the curve 336 shown in Fig. 2a, the front wheel 316a or the rear wheel 316c. The deceleration 43 during understeer 332 is illustrated by arrows 352, 354. During oversteer 334, however, the outside front wheel 316a is preferably decelerated in order to provide a reverse torque on the vehicle 300 that counteracts the excessive actual yaw rate 'T'lst. The deceleration 43 of the outside front wheel 316b in the left-hand curve 336 according to Fig. 2b is illustrated by arrow 355 in Fig. 1. The wheel-individual deceleration 43 preferably occurs asymmetrically on the axles of the vehicle 300, so that a yaw moment is applied. Wheels 316 of the axles of the vehicle 300 are therefore preferably decelerated to different degrees. For example, during understeer 332, wheel 316a can be decelerated while wheel 316b is not.The degree of deceleration 43 of at least one wheel 316 is determined based on the yaw rate deviation A^P and / or based on the deviation of the actual steering angle ölst from the target steering angle öSoll. For example, during oversteer 324 at the brake actuator 318, which is assigned to the outer front wheel 318b (in the case of a left turn 336), a particularly large brake pressure pB can be applied when the yaw rate deviation A^P is large, while a small brake pressure pB is applied when the yaw rate deviation A^P is small.

[0072] Fig. 5 illustrates the influence of the steering angle correction 41 and the deceleration 43, which is implemented in particular on a wheel-by-wheel or axle-by-axle basis, on the vehicle 300 during understeer 332 in a diagram. The diagram illustrates the course of the curvature K of the travel path FP, the desired steering angle öDesired, the actual steering angle ölst, the lateral deviation Q, and the directional error cp along the travel path, with the vehicle 300 traveling along a straight section 356 before and after the curve 336. In the straight section 356 before the curve 336, the actual steering angle ölst and the desired steering angle are zero. The lateral deviation Q and the directional error cp of the vehicle 300 are also approximately zero in the straight section 356 before the curve 336. Small fluctuations in the transverse deviation Q and the directional error cp in the straight section 356 result from incorrect determinations of the position 348 and, if necessary, corrections by the virtual driver 308.At the beginning of the curve 338, the actual steering angle ölst increases approximately uniformly with the desired steering angle öSoll. The virtual driver 308 controls the actual steering angle ölst using the electronically controllable steering system 310 in order to guide the vehicle 300 along the curve 336. Fig. 5 illustrates an understeer 332 of the vehicle 300. An actual steering angle ölst corresponding to the desired steering angle öSoll is not sufficient to guide the vehicle 300 along the curve 336. The lateral deviation Q towards the outside of the curve 346 and the directional error cp of the vehicle 300 towards the outside of the curve 346 increase, which can be seen in the two lower lines of the diagram shown in Fig. 5. In order to compensate for the transverse offset Q, the virtual driver 308 increases the actual steering angle ölst further and beyond a maximum of the target steering angle öSoll.In the exemplary embodiment shown, however, a further increase in the actual steering angle ölst is not expedient in order to compensate for the lateral offset Q and the directional error cp, since the vehicle 300 or its wheels 316 cannot provide any further lateral guidance forces due to poor road conditions. A sudden improvement in the road conditions would lead to a sudden buildup of large lateral guidance forces with an excessively large actual steering angle ölst, which could cause the vehicle 300 to skid. To prevent this, the steering angle limitation ölim is defined in method 1. Fig. 5 illustrates that the actual steering angle ölst that can be provided at the active steering system 310 is limited to a value that is slightly higher than the target steering angle öSoll due to the steering angle limitation ölim. The risk of sudden instability of the vehicle due to a change in road conditions is thus eliminated.To compensate for the lateral deviation Q and the directional error cp, an inner wheel 316 of the vehicle 300 is decelerated at the same time as the steering angle limitation ölim, thus providing a yaw moment, causing the vehicle 300 to turn inward 344. The deceleration is illustrated in Fig. 5 by the provision of a brake pressure pB. The lateral deviation Q of the vehicle 300 and its directional error cp decrease again. At the end of the curve 340, the actual steering angle ölst is reduced, and the wheel-specific deceleration 43 can be terminated. Instead of decelerating an individual wheel 316, axle-by-axle deceleration can also occur in the event of understeer 332.

[0073] The wheel-specific deceleration 43 and the steering angle correction 41 stabilize the vehicle 300 while negotiating the curve 336. Additionally, in response to the early detection 17 of understeer 332, an engine torque Mmot of the drive motor 312 is reduced (reduction 45 in Fig. 3 and Fig. 4). This further stabilizes the vehicle 300.

[0074] Fig. 6 shows, analogously to Fig. 5, a profile of the curvature K of the travel path FP, the lateral deviation Q of the vehicle 300, the directional error cp of the vehicle 300, the target steering angle öSoll of the vehicle 300 when driving through the curve 336 and the target steering angle öSoll of the vehicle 300 determined using the target trajectory TSoll. Unlike Fig. 5, however, Fig. 6 illustrates the profiles of these variables for an oversteer 334 of the vehicle 300 when driving through the curve 336. In the straight section 356, the steering angles öSoll, ölst, the lateral deviation Q and the directional error cp are again essentially equal to zero. At the beginning of the curve 338, the virtual driver 308 increases the actual steering angle ölst essentially uniformly to the target steering angle öSoll. Since the vehicle 300 understeers, the directional error cp increases toward the inside of the curve 344. At the same time, the lateral offset Q of the vehicle 300 increases toward the outside of the curve 346.To compensate for this lateral deviation Q, the virtual driver 308 would increase the actual steering angle ölst further in the direction of the inside 344 of the curve, thus further intensifying the oversteer 334. In vehicle control method 1, however, the countersteering angle öcs is defined as the steering angle correction 41 and is superimposed on the target steering angle öSoll. The countersteering angle öcs is opposite to the target steering angle öSoll, and therefore points towards the outside 346 of the curve. The countersteering angle öcs is significantly greater here than the target steering angle öSoll, so that an actual steering angle ölst is established that also points towards the outside 346 of the curve. This compensates for the understeer 334 and stabilizes the vehicle 300. In addition to the countersteering angle öcs, the steering angle correction 41 during oversteer 334 includes a steering angle limitation ölim. This steering angle limitation ölim ensures that the counter steering angle öcs does not exceed a mechanical limitation of the steering angle ö of approximately 45°.This ensures that resetting the actual steering angle ölst in the direction of the inside curve 344 does not take too long, and that mechanical limitations of the electronically controllable steering system 310 are observed. As described above, additional stabilizing measures also occur during oversteering 334, namely a reduction 45 of the engine torque Mmot of the drive motor 312 and a wheel-specific deceleration 43 of at least one wheel 316 (preferably the outer front wheel during oversteering 334) of the vehicle 300. The deceleration 43 is also illustrated in Fig. 6 by a curve of the brake pressure pB.

[0075] The diagrams according to Fig. 5 and Fig. 6 illustrate that the vehicle 300 is steered using the steering angle correction 41 after the early detection 17 of an unstable driving condition 330. This steering 47 is shown in the flowcharts for the first and second exemplary embodiments of method 1 (see Fig. 3 and Fig. 4). In the vehicle 300, the control unit 202 of the vehicle control system 200 takes over the electronically controllable steering 310 from the virtual driver 308 as soon as an unstable driving condition 330 has been detected early. To steer 47 the vehicle 300, the control unit 202 then provides steering signals SL on the vehicle network 324 and controls the electronically controllable steering 310 using the steering angle correction 41.However, it can also be provided that the control unit 202 provides the steering angle correction 41 to the virtual driver 308, and the virtual driver 308 performs the steering 47 of the vehicle 300 using the steering angle correction 41. In both variants, consideration of the steering angle correction 41 during the steering 47 of the vehicle 300 can be ensured, for example, by appropriate signal priorities. If the steering 47 of the vehicle 300 is performed using the steering angle correction 41 in response to the early detection 17 of an unstable driving condition 330 by the virtual driver 308, the control unit 202 of the vehicle control system 200 can be designed to be comparatively simple and cost-effective.If, however, the control unit 202 takes over the steering 47 using the steering angle correction 41 in response to the early determination 17 of an unstable driving condition 330, then the reliability of the vehicle 300 is increased because both the virtual driver 308 and the control unit 200 are configured to control the electronically controllable steering 310. Furthermore, responsiveness can be increased because the steering angle correction 41 is defined directly by the unit steering the vehicle 300 (the control unit 202). It should be understood that the control unit 202 can also be configured for steering 47 if the steering 47 is performed by the virtual driver 308 in response to the early determination 17. For example, the control unit 202 can steer the vehicle 300 using the steering angle correction 41 if the virtual driver 308 is making an error.

[0076] As explained above, the control unit 202 steers the vehicle 300 according to Fig. 1 in response to the early detection 17 of an unstable driving condition 330. The control unit 202 steers the vehicle 300 through the curve 336 and stabilizes the vehicle 300 through the interaction of steering 47, reducing 45 the engine torque Mmot of the drive motor 312 and by decelerating 43 for each wheel. Furthermore, the control unit 202 causes the braking system 314 of the vehicle 300 to brake the trailer vehicle 306 (brakes 53 in Fig. 3 and Fig. 4). The resulting stretch braking between towing vehicle 304 and trailer vehicle 306 prevents the trailer vehicle 306 from buckling. The strength of the braking 53 is optionally determined by the control unit 202 using the buckling angle y.Preferably, the trailer vehicle 306 is braked sharply at a large articulation angle y, i.e., when the trailer vehicle 306 has an alignment that differs significantly from the towing vehicle 304. At a small articulation angle y, i.e., when the trailer vehicle 306 is aligned essentially identically to the towing vehicle 304, a brake pressure pB at the brake actuators of the trailer vehicle 306 can be reduced. After the vehicle 300 has negotiated the curve 336, it returns to a straight section 356. There, the vehicle 300 behaves stably. In vehicle control method 1, therefore, a determination 49 of a stable driving state 342 of the vehicle 300 takes place. As a result of this determination 49, the control unit 202 transfers the electronically controllable steering 310 of the vehicle 300 back to the virtual driver 308, which here is also the position controller 322 of the vehicle 300 (transfer 51 in Fig. 3 and Fig. 4).Until the next early detection 17 of an unstable driving condition 330, the steering remains with the virtual driver 308.

[0077] Reference symbol (part of the description)

[0078] Vehicle tax procedure

[0079] Determining a target trajectory

[0080] Determining a target steering angle

[0081] Determining an actual size

[0082] Actual size

[0083] Monitoring the position of the vehicle

[0084] Determining a trajectory deviation

[0085] Determining a trajectory deviation change rate

[0086] Early detection of unstable driving conditions

[0087] Determining a target yaw rate

[0088] Determining a curvature of the target trajectory

[0089] Determining a target speed

[0090] Determining a yaw rate difference

[0091] Determine whether the magnitude of the actual yaw rate in a

[0092] Yaw rate tolerance band is

[0093] Determine whether the trajectory deviation change rate is increasing

[0094] Perform a comparison of the actual steering angle and the target

[0095] Steering angle

[0096] Target-actual comparison

[0097] Early detection of understeer

[0098] Early detection of oversteer

[0099] Defining a steering angle correction a Defining a steering angle correction for understeer b Defining a steering angle correction for oversteer

[0100] Steering angle correction wheel-specific deceleration

[0101] Reducing engine torque

[0102] Steering

[0103] Determining a stable driving condition

[0104] Handing over the steering

[0105] Braking a trailer vehicle vehicle control system

[0106] Control unit

[0107] vehicle

[0108] vehicle train

[0109] towing vehicle

[0110] Trailer vehicle virtual driver electronically controlled steering

[0111] drive motor

[0112] braking system

[0113] Wheels a left front wheel b right front wheel c left rear wheel

[0114] brake actuator

[0115] Brake modulator

[0116] Position controller

[0117] Vehicle network

[0118] drawbar

[0119] Road unstable driving condition

[0120] Understeer

[0121] Oversteer

[0122] curve

[0123] beginning of curve

[0124] End of curve stable driving condition

[0125] Inside curves

[0126] Outside curves

[0127] Position

[0128] Stability control system

[0129] Deceleration of a curve inside rear wheel illustrating

[0130] Arrow

[0131] Deceleration of a curve outer rear wheel illustrating

[0132] Arrow 354 Deceleration of a curve inside front wheel illustrative arrow

[0133] 355 Deceleration of a curve outer front wheel illustrating

[0134] Arrow

[0135] 356 straight section ESC Electronic Stability Control FP driving path

[0136] Mmot engine torque

[0137] 01 Surface information

[0138] PB brake pressure

[0139] SB brake signals

[0140] SL steering signals

[0141] TSoll Target trajectory

[0142] AT Trajectory deviation ATR Trajectory deviation change rate VSet Target speed

[0143] Y articulation angle ölst actual steering angle ösoll desired steering angle

[0144] K Curvature

[0145] M^lst actual yaw rate

[0146] 'T' Target yaw rate

[0147] AM^ Yaw rate difference P Directional error (pin inward direction error after turns (pout outward direction error after turns

Claims

Patent claims 1 . Vehicle control method (1 ) for a vehicle (300) with an electronically controllable steering system (310), the vehicle control method (1 ) comprising: Determining (3) a target trajectory (Tsoii) for the vehicle (300); Determining (5) a target steering angle (ösoii) for driving the target trajectory (Tsoii); Determining (7) an actual size (9) of the vehicle (300); Early detection (17) of an unstable driving condition (330) of the vehicle (300) at least using the actual variable (9) and the desired trajectory (TSoll); wherein during the early detection (17) it is determined whether the unstable driving condition (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) of the unstable driving condition (330): Defining (40) a steering angle correction (41) for the desired steering angle (öSoll), wherein the steering angle correction (41) comprises a steering angle limitation (ölim) of an actual steering angle (ölst) that can be provided by the electronically controllable steering system (310) if the unstable driving state (330) is understeering (332) of the vehicle (300), and wherein the steering angle correction (41) comprises a countersteering angle (öcs) directed opposite to the desired steering angle (öSoll) if the unstable driving state (330) of the vehicle (300) is oversteering (334); and Steering (47) of the vehicle (300) using the steering angle correction (41).

2. Method (1) according to claim 1, in response to the early detection (17) of the unstable driving condition (330) further comprising: Wheel-individual deceleration (43) of at least one wheel (316) of the vehicle (300).

3. Method (1) according to one of claims 1 or 2, wherein the steering angle limitation (ölim) corresponds to the desired steering angle (öSoll) plus a steering angle supplement (özu) if the unstable driving condition (330) is an understeer (332) of the vehicle (300).

4. Method (1) according to claim 3, wherein the steering angle supplement (özu) is determined using surface information (Ol) of a roadway (328) which is included in the desired trajectory (TSoll).

5. The method (1) according to any one of claims 1 to 4, further comprising: monitoring (11) a position (348) of the vehicle (300); Determining (13) a trajectory deviation (AT) of the vehicle (300) using the desired trajectory (TSolli) and the monitored position (348); and Determining (15) a trajectory deviation change rate (ATR).

6. Method (1) according to one of claims 1 to 5, wherein the actual variable (9) is an actual yaw rate (M Jlst) and the early detection (17) of an unstable driving condition (330) of the vehicle (300) at least using the actual variable (9) and the desired trajectory (TSoll), comprises: Determining (19) a target yaw rate ('T'Soll) for the vehicle (300) using the target trajectory (TSoll); and Determining an unstable driving condition (330) if the actual yaw rate ( ( 4 J lst) is outside a yaw rate tolerance band ('T'Tol) around the target yaw rate ('T'Tol) 7. The method (1) according to claim 6, wherein understeering (332) of the vehicle (300) is determined if the amount of the actual yaw rate ('+' Ist) is below the yaw rate tolerance band ('T'Tol), and wherein oversteering (334) of the vehicle (300) is determined if the amount of the actual yaw rate (M J lst) is above the yaw rate tolerance band (M^Tol).

8. The method according to claim 5 and 7, wherein understeering (332) or oversteering (334) of the vehicle (300) is only determined if the trajectory deviation change rate (ATR) indicates an increasing trajectory deviation (AT) of the vehicle (300) from the desired trajectory (TSoll).

9. The method (1) according to claim 8, wherein determining (19) the target yaw rate (M^Soll) for the vehicle (300) using the target trajectory (TSoll) comprises: Determining (21) a curvature (K) of the target trajectory (TSoll); Determining (23) an actual speed (Vlst) of the vehicle (300); Determining the target yaw rate ('- Soll) using at least the curvature (K) of the target trajectory (TSoll) and the actual speed (Vlst) of the vehicle (300).

10. Method (1 ) according to one of claims 6 to 9, wherein the yaw rate tolerance band (M JTol) a width of ± 0.1 ° / s to ± 10 ° / s, preferably ± 0.5° / s to ± 2° / s, to achieve the desired yaw rate (' J Target).

11. Method (1) according to one of claims 6 to 10, wherein the counter-steering angle (öcs) is determined using a yaw rate deviation between the actual yaw rate (M J lst) and the desired yaw rate (H-'Soll) is determined if the unstable driving condition (330) is an oversteer (334).

12. Method (1) according to claim 5, wherein the actual value (9) is the actual steering angle (ölst) and the early detection (17) of an unstable driving condition (330) of the vehicle (300) at least using the actual value (9) and the desired trajectory (TSoll), comprises: Carrying out (33) a target-actual comparison (35) between the actual steering angle (ölst) and the target steering angle (öSoll); and Early detection (17) of the unstable driving condition (300) if a trajectory deviation (AT) is determined and the actual steering angle (ölst) deviates from the target steering angle (öSoll) by at least one steering angle tolerance value (öTol).

13. The method (1) according to claim 12, wherein the early detection (17) of the unstable driving condition (330) if the actual steering angle (ölst) deviates from the desired steering angle (öSoll) by at least one steering angle tolerance value (ÖTol) and a trajectory deviation (AT) is determined, comprises: Early detection (37) of understeer (332) of the vehicle (300) if the trajectory deviation (AT) comprises a lateral deviation (Q) directed outwards (346) towards the curve and a directional error (cp) directed outwards (346) towards the curve; and Early detection (39) of an oversteer (334) of the vehicle (300) if the trajectory deviation (AT) indicates a direction error directed towards the inside (344) of the curve ( <p) umfasst.

14. Method (1 ) according to claim 13, wherein an early detection (37) of an understeer (332) and / or an early detection (37) of an oversteer (334) only occurs if the trajectory deviation change rate (ATR) indicates an increasing trajectory deviation (AT) of the vehicle (300) from the desired trajectory (TSoll).

15. Method (1 ) according to claim 13 or 14, wherein the counter-steering angle (öcs) is determined based on the inward-curving directional error (cp).

16. Method (1) according to one of claims 1 to 15, wherein the vehicle (300) is an at least partially autonomous vehicle (300), the determination of the desired steering angle (öSoll) is carried out by a position 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 condition (330) is detected.

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

18. Method (1) according to claim 16 or 17, further comprising: Determining (49) whether a stable driving state (342) of the vehicle (300) has been reached, and Transferring (51) the electronically controllable steering (310) of the vehicle (300) from the control unit (202) of the vehicle control system (200) to the position controller (322) of the vehicle (300) if a stable driving state (342) of the vehicle (300) is reached.

19. Method (1) according to one of claims 1 to 18, in response to the early detection (17) of the unstable driving condition (330) further comprising: Reducing (45) an engine torque (MMot) of the vehicle (300).

20. Method (1) according to one of claims 1 to 19, wherein the vehicle (300) is a vehicle train (302) with a towing vehicle (304) and at least one trailer vehicle (306), wherein the method (1) in response to the early detection (17) of the unstable driving condition (330) further comprises: Braking (53) of the trailer vehicle (306), wherein the braking (53) of the trailer vehicle (306) is preferably based on an articulation angle (y) between the towing vehicle (304) and the trailer vehicle (306).

21. Vehicle control system (200) for a vehicle (300), comprising a control unit (202) designed to carry out the method (1) according to one of claims 1 to 20.

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

23. Computer program product with program code means stored on a computer-readable data carrier for carrying out the method (1) according to one of claims 1 to 20 when the computer program product is executed on a computing unit.

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