EP4648998A1 - Vehicle control method with steering angle correction - Google Patents

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

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

Vehicle control procedure with steering angle correction

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.

The autonomization of vehicles is one of the key areas of development in the modern automotive industry. Partially autonomous vehicles take on partial tasks in controlling the vehicle, while autonomous vehicles are controlled completely without human intervention. Autonomous vehicles control the lateral and longitudinal guidance of the vehicle completely independently of a human user. Partially autonomous vehicles, on the other hand, only take on partial tasks in controlling the vehicle. As vehicles become increasingly autonomous, vehicles are increasingly 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 partially autonomous vehicles, for example if the vehicle has a lane keeping assistant that automatically keeps the vehicle within a lane. Electronically controlled steering controls the vehicle at least partially based on electrical signals.

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

Due to various influences, it may happen that the vehicle does not follow the specified target trajectory or that a trajectory deviation occurs. The vehicle then does not move along the path covered by the trajectory, but offset from it or with a different orientation.

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 with the electronically controllable steering, which can also be referred to as active steering. When cornering, if the vehicle veers sideways to the outside of a curve, the position controller will attempt to compensate for this veering sideways by turning more sharply (increasing the steering angle to the inside of a curve). In the case of unfavorable road conditions, this will not succeed because the vehicle does not respond to steering commands 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 guidance forces built up between the vehicle's tires and the road surface are not sufficient to guide the vehicle against inertia along the required curvature of the travel path. In particular, if there is already yaw instability, 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 a so-called Electronic Stability Control (ESC), is necessary. Due to the specified intervention thresholds of stability control systems, such an intervention only takes place when the vehicle is very unstable and therefore very late. The space required is increased and the risk of accidents increases. Furthermore, in the event of instability, the vehicle may no longer react at all to a change or variation in the steering angle and further steering on the part of the position controller can even worsen the stability of the vehicle, especially if the vehicle is understeering. Furthermore, too late and/or Incorrect counter-steering, even in the case of an oversteering vehicle, can further worsen the stability of the vehicle.

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

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 in a way that is appropriate to the situation.

The invention solves the problem with a vehicle control method of the type mentioned at the outset, comprising: determining a target trajectory for the vehicle; determining a target steering angle for driving the target trajectory; early detection of an unstable driving state of the vehicle at least using the target trajectory; wherein during the early detection it is determined whether the unstable driving state is understeering of the vehicle or oversteering of the vehicle; and in response to the early detection of the unstable driving state: 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 if the unstable driving state is understeering of the vehicle, and wherein the steering angle correction comprises a counter-steering angle directed opposite to the target steering angle if the unstable driving state 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 realization that the measures taken by a position controller and/or virtual driver to compensate for an unstable driving condition may be unsuitable for eliminating the unstable driving condition. Dangerous situations can be prevented by intervening early. The steering angle correction corrects the steering angle belonging to 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.

The target trajectory is preferably provided by a unit for autonomous driving, in particular a virtual driver, for example via a vehicle bus. Preferably, the vehicle control method 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 driving the target trajectory, whereby the virtual driver assumes stable driving behavior of the vehicle. Preferably, the target steering angle is included in the target trajectory. The target trajectory then includes not only the driving path to be driven, but also the target steering angle predicted for driving this driving path. Preferably, the determination of the target steering angle is model-based. For example, when determining the target trajectory, the virtual driver can determine a target steering angle to be specified 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 speed of the vehicle or a speed profile of the vehicle when driving along the target trajectory, whereby the speed and/or the speed profile can be included in the target trajectory. The actual value is a value that occurs when driving along the trajectory or in the driving situation to which the target trajectory belongs.

The early detection of an unstable driving state of the vehicle is carried out at least using the actual size and the target trajectory. In contrast to previously known methods, instabilities can be detected not only when various vehicle sensors report strong actual deviations from predefined threshold values. The target trajectory is taken into account according to the invention and allows an instability to be detected that is adapted to the respective driving situation. In this way, an unstable Driving conditions can be detected early, for example, if the actual value deviates from the target trajectory or from a value derived from the target trajectory by more than a tolerance value. 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 so-called self-steering gradient of the vehicle is greater than zero, so it has to be steered more strongly to follow a curve than with a neutral vehicle. Oversteering of the vehicle is also colloquially referred to as the vehicle skidding.

The steering angle correction is defined in response to the early detection of the unstable driving condition. In the case of understeering, the steering angle correction includes a steering angle limitation of the available actual steering angle. In the case of understeering, the vehicle deviates from the planned driving path on the outside of curves. 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 strongly. The target steering angle that 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 cornering forces. This is often the case when the grip between the tires and the road is reduced, for example in wet or slippery conditions. If the grip between the tires and the road suddenly increases again when the actual steering angle is large, the steered wheels suddenly build up high cornering forces and the vehicle can become uncontrollable. In the method according to the invention, a steering angle limitation is defined in the event of understeering, so that this risk is eliminated. The vehicle is steered using the steering angle correction, so that no actual steering angle can be specified that goes beyond a sensible or safe level. 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 to 30°.

In the case of oversteering, the vehicle turns more sharply than is necessary to travel the current path. In doing so, the vehicle usually also leaves the planned path. However, the position controller and/or autonomous driver must not base the steering angle on the offset of the vehicle from the planned path in order to return to it. For example, in the case of an oversteering vehicle, If the vehicle is veering sideways towards the outside of a curve, a pure orientation based on the position deviation would result in the actual steering angle being increased further in the direction of the curve, which would further increase oversteering. Instead, the vehicle reaction should be adapted to the excessive yaw rate and this should be appropriately dampened by countersteering. In the method according to the invention, this is achieved in that the steering angle correction comprises a countersteering angle that is directed opposite to the target steering angle, which is directed inwards towards curves. When the vehicle is steered using the steering angle correction, the countersteering angle counteracts the target steering angle and the vehicle is stabilized. The countersteering angle that counteracts the target steering angle has a sign that is opposite to the actual steering angle. For example, if the actual steering angle is positive (i.e. measured counterclockwise), then the countersteering angle is a negative angle (measured clockwise).

In a first preferred embodiment, the method further comprises, in response to the early detection of the unstable driving state: wheel-specific deceleration of at least one wheel of the vehicle. In addition to the steering angle correction, the method in the preferred embodiment also 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. As a result of the steering angle limitation or other factors, such as a low coefficient of friction between the vehicle and the road, a 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 that can be set by the steering. Preferably, a brake slip is controlled on the wheel to be decelerated to decelerate the wheel. This can be done, for example, by providing a brake pressure on a brake actuator assigned to the wheel. However, the wheel to be decelerated can also be decelerated, for example, by recuperation. A wheel that is individually decelerated is decelerated independently of the other wheels of the vehicle. However, it can be provided that two or more wheels of the vehicle are simultaneously decelerated to the same extent. For example, all wheels of a vehicle that are oriented towards the center of a curve (ie all wheels on the inside of the curve) can be decelerated to the same extent. Of course, only a single wheel can be decelerated. For example, to compensate for oversteering, an outer front wheel of the vehicle on the curve can be decelerated in order to compensate for oversteering. to provide a counteracting yaw moment. The necessary control variable for deceleration and/or the selection of the correct wheel is preferably carried out using the target trajectory and the actual size. Unlike in a conventional stability control system (ESC), in which the strength of the intervention is dosed solely via the steering, a target size is also taken into account. By decelerating each wheel, an additional yaw moment is preferably provided, which acts in the direction of the steering angle correction. In the event of understeering, the steering angle correction or the steering angle limitation acts in the direction of the target steering angle. The steering angle correction therefore counteracts the yaw of the vehicle towards the outside of bends. In the event of oversteering, the countersteering angle acts towards the outside of bends, so that the yaw moment provided by the wheel-individual deceleration counteracts an excessive rotation of the vehicle towards the inside of bends. Preferably, wheel-individual deceleration does not take place on an axle-by-axle basis. Wheels of the commercial vehicle belonging to the same axle are therefore preferably not decelerated uniformly.

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

It is also preferred that the steering angle limitation corresponds to the target steering angle plus a steering angle allowance if the unstable driving condition is understeering of the vehicle. By taking into account a fixed or variable steering angle allowance, the steering angle limitation can be defined particularly easily. The steering angle allowance is preferably determined taking into account the target trajectory. For example, the steering angle allowance can be selected to be larger if the driving path is very curved or at high speeds than for a target trajectory that corresponds to the vehicle traveling slowly. 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. Preferably, the target steering angle can also take into account a build-up of force in 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 cornering forces in the contact area between the tire and the road.

According to a further preferred embodiment, the steering angle allowance 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 smooth 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 wheels of the vehicle can achieve maximum lateral guidance of the vehicle depends on the surface of the roadway or a friction coefficient between the wheels of the vehicle and the roadway on which the vehicle is traveling. On icy roads, the optimal slip angle has a lower value than on a rough, dry roadway. 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 allowance is lower than on dry roads, since a further increase in the steering angle may no longer be useful even at comparatively low steering angles.

Preferably, the method further comprises: monitoring a position of the vehicle; determining a trajectory deviation of the vehicle using the target 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 determined at discrete time intervals. By monitoring the position, a change in the position of the vehicle can be determined. The position preferably includes the position of the vehicle. Furthermore, the position can alternatively or additionally also include an orientation of the vehicle, in particular a heading angle. The heading angle refers to an angle between the geographic north direction and the target direction of the vehicle. If the vehicle is traveling east, for example, 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 position of the vehicle from the trajectory. The trajectory deviation is or preferably includes a position deviation of the vehicle between an actual current position of the vehicle and a target position of the vehicle on the travel path. An example of a position deviation is a transverse deviation of the vehicle from the travel path transverse to the direction of travel. The trajectory deviation can also be or include a course angle deviation between an actual course angle of the vehicle and a target course angle. The trajectory deviation change rate indicates the temporal change of the trajectory deviation. The trajectory deviation change rate preferably describes the change of the trajectory deviation over a certain period of time in relation to the duration of this period of time. The period under consideration is preferably short. The duration of the period of time 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, the vehicle's lateral offset (i.e. an offset of the vehicle transverse to the travel path) steadily increases. Determining the trajectory deviation change rate allows for particularly simple early detection of the unstable driving state. Starting from a state 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. An unstable driving state can thus 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, so that these stability control systems can only detect unstable driving states when steering is performed. Unstable driving states can therefore be detected much 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 of early detection of an unstable driving condition using the desired trajectory.

In a preferred development, the actual value is an actual yaw rate and the early detection of an unstable driving state of the vehicle at least using the actual value and the target trajectory comprises: determining a target yaw rate for the driving vehicle using the target trajectory; determining an actual yaw rate for the vehicle; and determining an unstable driving state if the actual yaw rate is outside a yaw rate tolerance band around the target 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 that are 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 on 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 requirement for the at least one wheel.

Preferably, understeering of the commercial vehicle is determined if the amount of the actual yaw rate is below the yaw rate tolerance band, and oversteering of the vehicle is determined if the amount of the actual yaw rate is above the yaw rate tolerance band. The actual yaw rate is below the yaw rate tolerance band if the amount of the actual yaw rate is less than the amount of the target yaw rate and the actual yaw rate is not within the yaw rate tolerance band. Analogously, the actual yaw rate is above the yaw rate tolerance band if the amount of the actual yaw rate is greater than the amount 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 amount. If the amount of the actual yaw rate is below the yaw rate tolerance band, then the vehicle is understeering. If, on the other hand, the amount of the actual yaw rate is above the yaw rate tolerance band, then the vehicle is oversteering. The advantage of the quantitative analysis is that the method can be applied to left and right turns.

In a preferred development, understeering or oversteering is only determined if the trajectory deviation change rate indicates an increasing trajectory deviation of the vehicle from the target trajectory. According to the preferred development, understeering is therefore only determined if the actual yaw rate is below the yaw rate tolerance band and the trajectory deviation increases. In a similar way, oversteering is only determined in the preferred development if the actual yaw rate is above the yaw rate tolerance band and the trajectory deviation increases. The determination of an unstable driving state is thus more robust and the risk of incorrect determination is minimized. For example, error averaging can be excluded in cases in which the vehicle already enters a curve with a transverse deviation to the driving path included in the target trajectory, but then follows the curve stably with a constant transverse deviation.

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.

Preferably, the yaw rate tolerance band 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 target yaw rate. The yaw rate tolerance band preferably 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 target yaw rate. For example, if the target yaw rate has a value of 107s and the yaw rate tolerance band has a width of ± 1.57s, then an unstable driving condition is determined if the value of the actual yaw rate is less than or equal to 8.57s (understeer) or if the value of the actual yaw rate is greater than or equal to 11.57s (oversteer). The yaw rate tolerance band can preferably also be determined dynamically. 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. The yaw rate tolerance band preferably has a minimum width which is not undercut even if there is no curvature of the target trajectory (on a straight stretch). In one variant, the countersteering angle is determined using a yaw rate deviation between the actual yaw rate and the target yaw rate if the unstable driving condition is oversteering. The yaw rate deviation is preferably determined from the amount of the actual yaw rate and the amount of the target yaw rate. The yaw rate deviation is then independent of the direction of the curve. By using the yaw rate deviation to determine the countersteering angle, oversteering can be counteracted particularly effectively. A large yaw rate deviation then also requires a large countersteering angle. For example, if the vehicle swerves sharply, strong countersteering is also carried out.

According to a preferred embodiment, the actual value is the actual steering angle and the early detection of an unstable driving state of the vehicle at least using the actual value and the target trajectory comprises: performing a target-actual comparison between the actual steering angle and the target steering angle; and early detection of the unstable driving state if a trajectory deviation is determined and the actual steering angle deviates from the target steering angle by at least a steering angle tolerance value. It should be understood that the early detection of an unstable driving state can be carried out based on the actual steering angle and based on the actual yaw rate. For example, an unstable driving state can only be determined if the actual yaw rate is outside the yaw rate tolerance band and the actual steering angle deviates from the target 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 understeering and/or oversteering only occurs if 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. If 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. Due to the steering angle tolerance value, only significant deviations of the actual steering angle from the target steering angle lead to Early detection of unstable driving conditions. This minimizes the risk of false detections, for example due to measurement errors when determining the actual steering angle. The process becomes more robust.

Preferably, the early detection of the unstable driving state, if the actual steering angle deviates from the target steering angle by at least one steering angle tolerance value and a trajectory deviation is determined, comprises: early detection of understeering of the vehicle if the trajectory deviation comprises a transverse 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 comprises a directional error directed inwards towards curves. The trajectory deviation preferably comprises a transverse 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 course angle. Preferably, the directional error is determined if the deviation between the target direction of movement and the actual direction of movement is 2° or more. The inside of a curve is the side of a curve on which the center of the curve radius of the curve is located. 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 transverse 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 slip angle of the vehicle. The slip angle can be determined, for example and preferably by integration based on a time profile of the yaw rate and a direction of movement of the vehicle. The slip angle is preferably determined based on the yaw rate deviation, in particular by temporal integration of the yaw rate deviation.

In a preferred further development, the counter-steering angle is determined based on the directional error directed inwards towards curves. Alternatively or additionally, the counter-steering angle can also be determined based on the sideslip angle.

Preferably, the vehicle is an at least partially autonomous vehicle, wherein the determination of the target steering angle is carried out by a position controller of the vehicle, and wherein the steering of the vehicle is carried out 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 carried out by the steering. The takeover can preferably take place by assigning a corresponding priority, so that steering requests provided by the control unit are carried out in preference to steering requests from the position controller.

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. The method can thus be carried out particularly quickly. It is also ensured that the vehicle is steered using the steering angle correction. However, it can also be provided that the steering angle correction is provided on the position controller and the position controller steers the vehicle using the steering angle correction.

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 of the vehicle as soon as an unstable driving state is detected. Before the unstable driving state is detected, the vehicle is usually 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 state is achieved when there is no understeering or oversteering. no longer exists and/or if a trajectory deviation is within a tolerance corridor around the target trajectory. For example, a stable driving condition may not be achieved even if the vehicle is not understeering or oversteering but still deviates transversely from the driving path of the target trajectory.

Preferably, the method comprises reducing an engine torque of the vehicle in response to the early detection of the unstable driving state. 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, so that returning the vehicle to a stable state with reduced engine torque is made easier.

It is further 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 preferably takes place 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 so 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.

In a second aspect, the invention solves the problem mentioned at the outset by a vehicle control system for a vehicle, in particular a commercial vehicle, having a control unit that is designed to carry out the method according to the first aspect of the invention. Preferably, the vehicle control system as such can also be designed to carry out the method according to the first aspect of the invention.

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 is used to determine a target trajectory for the vehicle with a virtual vehicle. rer of the vehicle and has an interface for connection to an electronically controllable steering system of the vehicle; wherein the control unit is designed to; determine a target steering angle for driving the target trajectory; determine an actual size of the vehicle and determine oversteering or understeering of the vehicle at least using the actual size and the target trajectory; wherein the control unit is further configured to determine a steering angle correction for the target steering angle in response to the early detection of the unstable driving state and to provide a control variable based on the steering angle correction and the target steering angle at the interface for steering the vehicle, wherein the steering angle correction comprises a steering angle limitation of the steering angle that can be provided by the electronically controllable steering if the unstable driving state is understeering of the vehicle, and wherein the steering angle correction comprises a counter-steering angle directed opposite to the target steering angle if the unstable driving state of the vehicle is oversteering. The target steering angle can preferably also be included in the target trajectory.

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 are particularly set out 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 also 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.

In a fourth aspect, the object mentioned at the outset is achieved by a vehicle, in particular a commercial vehicle, having an electronically controllable steering system, a virtual driver who is designed 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 at the outset is achieved by a computer program product with program code means that are stored on a computer-readable data carrier in order to carry out 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.

Embodiments of the invention are now described below with reference to the drawings. These are not necessarily intended to show the embodiments to scale; rather, the drawings are schematic and/or slightly distorted if 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 a wide variety of modifications and changes can be made to the shape and detail of an embodiment without deviating from the general idea of the invention. The features of the invention disclosed in the description, drawings and claims can be essential for the development of the invention both individually and in any combination. In addition, all combinations of at least two of the features disclosed in the description, drawings and/or claims fall within the scope of the invention. The general idea of the invention is not limited to the exact shape or detail of the preferred embodiments shown and described below or limited to an object that would be limited compared to the object claimed in the claims. For specified design ranges, values within the specified limits should also be disclosed as limit values and can be used and claimed as required. For the sake of simplicity, the same reference symbols are used below for identical or similar parts or parts with identical or similar functions.

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;

Fig. 2a a vehicle understeering when negotiating a curve;

Fig. 2b a vehicle oversteering when negotiating a curve;

Fig. 3 is a schematic flow diagram illustrating a first embodiment of a vehicle control method;

Fig. 4 is a schematic flow diagram illustrating a second embodiment of a vehicle control method;

Fig. 5 is a diagram showing the course of a target value for understeer.

steering angle, an actual steering angle, a curvature of a curve, a transverse offset of the vehicle and a directional error of the vehicle along a travel path; and in

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.

Fig. 1 shows a vehicle 300, which is designed here as a vehicle train 302. The vehicle train 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, which is designed to carry out trajectory planning in order to obtain a target trajectory TSoll for the vehicle 300. The target trajectory TSoll comprises the travel path FP to be traveled by the vehicle 300, which the vehicle 300 is to follow according to the target trajectory TSoll.

The vehicle 300 further comprises an electronically controllable steering system 310, a drive motor 312 and a braking system 314, which is 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 braking signals SB from the virtual driver 308 and controls corresponding braking pressures pB for the brake actuators 318. It should be understood that the braking pressures pB of the wheels 316 can vary. A braking pressure pB on a left front wheel 316a can therefore be different from a braking pressure pB provided at the brake actuator 318 that is assigned to a right front wheel 316b of the vehicle 300. Furthermore, the braking system 314 is also provided for decelerating the trailer vehicle 306, wherein only brake actuators 318 of the towing vehicle 304 are shown in Fig. 1.

In addition to trajectory planning, the virtual driver 308 of the vehicle 300 shown in Fig. 1 is designed as a position controller 322. The virtual driver 308 controls the vehicle 300 in a regular driving situation along the travel path FP included in the target trajectory TSoll. To do this, the virtual driver 308 controls the drive motor 312, the braking system 314 and the electronically controllable steering 310 such that the vehicle 300 follows the travel path PF at a target speed VSoll included in the target trajectory TSoll, wherein the target speed VSoll 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 braking 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 here, namely a CAN bus of the commercial vehicle 300.

The electronically controllable steering 310 receives steering signals SL provided by the virtual driver 308 and steers the vehicle 300 in accordance with these steering signals SL. To do this, the electronically controllable steering 310 controls an actual steering angle ölst on the front wheels 316a, 316b of the towing vehicle 304 in normal operation, which 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.

The towing vehicle 304 and the trailer vehicle 306 are connected by means of a drawbar 326, whereby 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 driving 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.

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 display the driving behavior assumed as part of the trajectory planning. This is often the case when the vehicle 300 is unfavorably loaded or when the 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 tends to be unstable because the trailer vehicle 306 can push the towing vehicle 304 from behind. Furthermore, a deviation between the assumed driving behavior and real driving behavior may occur, for example, when a loading situation of a trailer vehicle 306 designed as a semitrailer leads to an increased rear axle load of a towing vehicle 304 designed as a tractor unit, thus causing understeering driving behavior. Furthermore, poor road conditions, such as slippery roads or reduced friction between tires of the vehicle 300 and a roadway 328 (see Fig. 2a, 2b) due to an oil slick, sand or chippings, can lead to the vehicle 300 not being able to follow the travel path FP included in the target trajectory TSoll.

Two unstable driving conditions 330 that can occur when the vehicle 300 is cornering are understeering 332 and oversteering 334 of the vehicle 300. Fig. 2a and Fig. 2b illustrate these unstable driving conditions 330 using a simplified representation of a vehicle 300 driving through a curve 336 (left turn). Fig. 2a shows an understeer 332 of the vehicle 300, while Fig. 2b illustrates an oversteer 334 of the vehicle 300.

In Fig. 2a, the vehicle 300 travels through the 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 the vehicle 300 in the unstable driving state 330, which is superimposed on the vehicle 300 in a stable driving state 342, in which the vehicle 300 ideally follows the target trajectory TSoll. In the stable driving state 342, the vehicle 300 is shown with lower contrast compared to the unstable driving state 330. When entering the curve 336, the stable driving state 342 and the unstable driving state 330 are still identical. In the unstable case, the vehicle 300 cannot follow the course of the curve 336 or the target trajectory TSoll. During understeering 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 transverse offset Q of the vehicle 300 to the travel path FP or to the target trajectory TSoll increases continuously from the curve entrance 338 to the curve exit 340. An actual yaw rate 'T'actual of the vehicle 300 is less than a target yaw rate ^Soll, so that the vehicle 300 turns less into the curve 336 than is desired to follow the target trajectory TSoll. A directional error cp between the orientation of the vehicle 300 during understeering 332 and the stable driving vehicle 300 increases towards the curve exit 340.

Fig. 2b illustrates an oversteering vehicle 300. The vehicle 300 during oversteering 334 is also superimposed here on a vehicle 300 in a stable driving state 342 (shown with lower contrast in Fig. 2b). During oversteering 334, the vehicle 300 turns more sharply than would be necessary for the current driving path FP. Even if the actual steering angle ö of the vehicle 300 is smaller than a target steering angle ötar, or even points in the opposite direction, the actual yaw rate 'T'lst of the vehicle 300 during oversteering 334 exceeds the target yaw rate ^target that would be necessary to negotiate the curve 336. The directional error cp also increases continuously during oversteering 334 from the corner entrance 338 to the corner exit 340, but has a different sign compared to understeering 332. Thus, a front of the vehicle 300 points further inwards 344 during oversteering 334 than in the stable driving state 342, whereas the front of the vehicle 300 during understeering 332 is directed further towards the outside of the curve 346 than in the stable driving state 342. Due to the actual yaw rate being too high compared to the target yaw rate M^Soll the rear of the vehicle 300 breaks out during oversteering 334. In the embodiment according to Fig. 2b, a transverse offset Q of the vehicle 300 towards the outside of the curve also increases 346.

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 target 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 transverse deviation Q of the vehicle 300 towards the outside of the curve 346. The greater the transverse 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 exceeds a predefined rate of change (i.e. change in the actual steering angle ölst per unit of time), a stability control system 350 of the commercial vehicle 300 intervenes to stabilize it. 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 control a brake pressure pB on the brake actuator 318 that is assigned to the outer front wheel 316b of the vehicle 300 when cornering. The brake actuator 318 decelerates the right front wheel 316b. This deceleration is illustrated in Fig. 1 by the arrow 355.

The ESC is an emergency system that only intervenes in the driving of the commercial vehicle 300 when very large instabilities occur. Interventions by the ESC 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 intervention threshold of the ESC is therefore set very high, so that only large instabilities in the vehicle 300 lead to an intervention by the ESC. The high intervention thresholds of the ESC mean that a stabilizing intervention by the ESC only takes place late, for example when the vehicle 300 already has a very large transverse deviation Q from the driving path FP of the target trajectory TSoll. 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 only intervenes late in the case of oversteering 334, since incorrect interventions that can result from measurement errors, for example, 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 here is the transverse offset Q and the directional error cp, which brings with it the disadvantages mentioned above.

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 designed 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 TSoll from the vehicle network 324, wherein the target trajectory TSoll 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.

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 target steering angle öSoll from the target trajectory TSoll, for example by the electrically controllable steering system 310 calculating the target steering angle öSoll from the curvature of the travel path FP and pre-stored geometric dimensions of the vehicle 300.

In a further step, at least one actual value 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 ^J lst of the vehicle 300 when driving through the curve 336. The determination 7 of the actual variables 9 is carried out here based on signals S which are 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 '- lst 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 completely or partially simultaneously, or that the determination 7 takes place before the determination 5 or the determination 3.

Simultaneously with the determination 3, 5, 7 of the target trajectory TSoll, the target steering angle öSoll 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 AT of the vehicle 300 from the target trajectory TSoll using the target 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 target trajectory TSoll increases. However, as the trajectory deviation change rate ATR decreases, the trajectory deviation AT is reduced, so that the vehicle 300 in this case approaches the target trajectory Ttarget. 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 state 300 takes place using a yaw rate-based approach, while Fig. 4 illustrates a steering angle-based approach of the method 1. Preferably, however, the method 1 includes both approaches. As a result, an unstable driving state 300 can be predicted particularly reliably using the vehicle control method 1.

In the yaw rate-based approach according to Fig. 3, the early detection 17 first includes determining 19 a target yaw rate '4 ^J target. The control unit 202 determines the target yaw rate M ^J target here based on the target trajectory T target. To do this, the control unit 202 first carries out a determination 21 of a curvature K of the target trajectory T target, where the curvature K here is the curvature K of the curve 336. The control unit 202 also determines an actual speed V target 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 V target, the control unit 202 determines the target yaw rate M J target from these variables.

In a further step of the vehicle control method 1 (determination 27 in Fig. 3), the control unit 202 of the vehicle control system 200 determines a yaw rate difference A'T' between the actual yaw rate 'T'lst and the target yaw rate M ^J Soll from the target yaw rate M ^J Soll determined using the target trajectory TSoll and the real actual yaw rate 'T'lst occurring when driving through the curve 336. The yaw rate difference A'T' is a measure of the strength of the unstable driving state 330. The yaw rate difference A'T' is particularly large during oversteering 334 when the vehicle 300 turns significantly faster towards the inside of curves 344 than desired. The yaw rate difference A'T' is used in a later step of the method 1 to determine the strength 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 state 330. In the embodiment of the method 1 shown, for the early detection 17 of the unstable driving state 330, it is determined (determination 29 in Fig. 3) whether the amount of the actual yaw rate 'T'lst is within a yaw rate tolerance band 'T'Tol around the target yaw rate MJSoll. 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 '4 ^J Soll, then an understeer 332 of the vehicle 300 can be determined. If the amount of the actual yaw rate '4 ^J lst is outside the yaw rate tolerance band M ^J Tol and the amount of the actual yaw rate ' ^J lst is greater than the amount of the target yaw rate '4 ^J Soll, then an oversteer 334 of the vehicle 300 can be determined.

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 the method 1 and to avoid false detections of unstable driving states 330, the early detection 17 in the 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 target trajectory Ttarget increases over the course of the curve 336, an unstable driving state 330 is detected. By taking the trajectory deviation change rate ATR into account, 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 caused by other reasons, then no unstable driving condition 330 is detected. This is the case, for example, if the vehicle 330 already has a transverse offset Q to the target trajectory TSoll towards the outside of the curve 346 at the beginning of the curve 338. In such a situation, the virtual driver 308 will try to compensate for the transverse 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 target steering angle öSoll determined from the target trajectory TSoll. As a result, the actual yaw rate 'T'lst is also greater than the corresponding target yaw rate 'T'Soll' 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 amount of the actual yaw rate 'T'lst' is greater than the amount of the target yaw rate 'T'Soll'. Since the vehicle 300 simultaneously approaches the target trajectory TSoll or the travel path FP, the trajectory deviation AT is reduced and the trajectory deviation change rate ATR indicates a decreasing trajectory deviation AT. In this special case, no oversteer 334 is therefore determined. Analogously, despite an amount of the actual yaw rate 'T'lst that is smaller than an amount of the target yaw rate 'T'Soll, no understeer 332 is determined if the trajectory deviation AT decreases. This is particularly the case when the vehicle 300 is already entering the curve 336 with a transverse offset Q to the inside 344 of the curve.

Fig. 4 illustrates the steering angle-based approach for early detection 17 of an unstable driving state 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 driving through the curve 336, and the target steering angle öSoll previously determined using the target trajectory TSoll (implementation 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 state 330 can be detected early, since this indicates that the virtual driver 308 is attempting to compensate for a trajectory deviation AT. 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, the yaw rate tolerance band 'T'Tol is taken into account in the first embodiment of the method 1 according to Fig. 3.

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

In the case of both understeering 332 and oversteering 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 and, as a result, a transverse deviation Q of the vehicle 300 from the target trajectory TSoll will occur, which is directed to the outside 346 of the curve. To compensate for this transverse deviation Q, the virtual driver 308 will attempt to increase the actual steering angle ölst beyond the target steering angle öSoll both in the case of understeering 332 and in the case of oversteering 334. To distinguish between oversteering 334 and understeering 332, the method 1 according to the second embodiment also uses the determined trajectory deviation AT. In the event that the trajectory If the torien deviation AT includes a transverse deviation Q of the vehicle 300 directed towards the outside 346 of the curves from the desired trajectory TSoll and a directional error (pout) directed towards the outside 346 of the curves, 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 curves is determined when the vehicle 300 is transversely deviated Q towards the outside 346 of the curves, an early detection 39 of an oversteer 334 takes place. During oversteer 334, the vehicle 300 turns more towards the inside 344 of the curves than desired, which results in the directional error (pin) directed towards the inside 344 of the curves.

Analogous to the first 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 state 330 is only detected early if the trajectory deviation change rate ATR indicates an increasing trajectory deviation AT.

Following the early detection 17 of an unstable driving state 330, the two embodiments of the vehicle control method 1 are essentially identical. In response to the early detection 17 of the unstable driving state 330, a steering angle correction 41 is defined 39 in both embodiments of the vehicle control method 1 according to the invention. In the event of understeering 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 310. The steering angle limitation ölim therefore limits the actual steering angle ölst that can be provided to a maximum value. The steering angle limitation ölim here corresponds to the target steering angle öSoll plus a steering angle allowance özu. In the event of oversteering 334 of the vehicle (illustrated in Fig. 3 and Fig. 4 as defining 40b), the steering angle correction 41 is a counter-steering angle öcs. The counter-steering angle öcs is directed opposite to the target steering angle öSoll and points outwards 346 of the curves. The size of the counter-steering angle öcs is preferably defined based on the severity of the unstable driving state 330. Thus, in the case of severe instability, which can 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 target steering angle öSoll, a large counter-steering angle öcs is preferably defined and vice versa. The steering angle limitation ölim corresponds to the target steering angle öSoll plus the steering angle allowance özu. The steering angle allowance özu can be a pre-stored value. In the 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 target trajectory TSoll and represents grip properties of the roadway 328. The control unit 202 of the vehicle control system 200 receives the target trajectory TSoll and determines the surface information Ol from it.

The control unit 202 then uses this surface information Ol when defining 40a the steering angle correction 40a in the case of understeering 332. The steering angle allowance özu is thus 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 low absolute values. On the other hand, if the road surface has good grip or the surface information Ol is corresponding, the steering angle allowance özu can be large, since cornering forces can still be provided even with large actual steering angles ölst.

In parallel with the definition 39 of the steering angle correction 41, in both embodiments of the method 1, a wheel 316 of the vehicle 300 is decelerated 43 for each wheel. The wheel-individual 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 understeering 332 or to reduce it in the case of oversteering 334.

Preferably, the wheel-individual deceleration 43 during understeering 332 takes place on 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 understeering 332 is illustrated by arrows 352, 354. During oversteering 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 in Fig. 1 by arrow 355. The wheel-individual deceleration 43 preferably takes place asymmetrically on the axles of the vehicle 300, so that a yaw moment is applied. Wheels 316 of axles of the vehicle 300 are therefore preferably decelerated to different degrees. For example, in the case of understeering 332, the wheel 316a can be decelerated while the wheel 316b is not decelerated. A strength of the Deceleration 43 of the 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 oversteering 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 controlled with a large yaw rate deviation A^P, while a small brake pressure pB is controlled with a small yaw rate deviation A^P.

Fig. 5 illustrates the influence of the steering angle correction 41 and the deceleration 43, which is implemented in particular on an individual wheel or axle basis, on the vehicle 300 during understeering 332 in a diagram. The diagram illustrates the course of the curvature K of the travel path FP, the target steering angle öSoll, the actual steering angle ölst, the lateral deviation Q and the directional error cp along the travel path, with the vehicle 300 traveling on 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 target 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 offset 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 target steering angle öSoll. The virtual driver 308 controls the actual steering angle ölst using the electronically controllable steering 310 in order to guide the vehicle 300 along the curve 336. Fig. 5 illustrates understeering 332 of the vehicle 300. An actual steering angle ölst corresponding to the target 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 lateral deviation 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 deviation 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 If the actual steering angle ölst is too large, this would lead to large cornering forces suddenly building up, 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 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 the road conditions is thus eliminated. In order to compensate for the transverse offset Q and the directional error cp, a cornering 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 inwards 344 into the curve. 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 ended. Instead of decelerating an individual wheel 316, deceleration can also take place on an axle-by-axle basis in the event of understeer 332.

The wheel-individual deceleration 43 and the steering angle correction 41 stabilize the vehicle 300 while driving through the curve 336. In addition, in response to the early detection 17 of the understeer 332, a motor torque Mmot of the drive motor 312 is reduced (reduction 45 in Fig. 3 and Fig. 4). This further stabilizes the vehicle 300.

Fig. 6 shows, analogously to Fig. 5, a course of the curvature K of the travel path FP, the transverse 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 courses 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 transverse 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 direction error cp increases towards the inside of the curve 344. At the same time, the lateral deviation Q of the vehicle 300 increases towards 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 towards the inside of the curve 344 and thus the oversteer 334 can be further increased. In vehicle control method 1, however, the countersteering angle öcs is defined as a steering angle correction 41 and is superimposed on the target steering angle öSoll. The countersteering angle öcs is directed opposite to the target steering angle öSoll, i.e. it points towards the outside of the curves 346. The countersteering angle öcs is significantly larger here than the target steering angle öSoll, so that an actual steering angle ölst is established, which also points towards the outside of the curves 346. This compensates for the understeer 334 and stabilizes the vehicle 300. In addition to the countersteering angle öcs, the steering angle correction 41 for oversteering 334 includes a steering angle limitation ölim. This steering angle limitation ölim ensures that the countersteering 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 of the curve 344 does not take too long and that mechanical restrictions of the electronically controllable steering 310 are adhered to. As described above, additional stabilizing measures also take place during oversteering 334: reducing 45 the engine torque Mmot of the drive motor 312 and decelerating 43 at least one wheel 316 (preferably the outside front wheel of the curve during oversteering 334) of the vehicle 300. The deceleration 43 is also illustrated in Fig. 6 by a curve of the brake pressure pB.

The diagrams according to Fig. 5 and Fig. 6 illustrate that the vehicle 300 is steered after the early detection 17 of an unstable driving state 330 using the steering angle correction 41. This steering 47 is shown in the flow charts for the first and second embodiments of the 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 state 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 for the virtual driver 308 and the virtual driver 308 carries out the steering 47 of the vehicle 300 using the steering angle correction 41. In both variants, consideration of the steering angle correction 41 when steering 47 the vehicle 300 can be ensured, for example, by appropriate signal priorities. If the steering 47 of the vehicle 300 is carried out using the steering angle correction 41 in response to the early determination 17 of an unstable driving state 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, on the other hand, 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 state 330, then the reliability of the vehicle 300 is increased, since both the virtual driver 308 and the control unit 200 are designed to control the electronically controllable steering 310. Furthermore, a 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 designed for steering 47 when the steering 47 is carried out in response to the early determination 17 by the virtual driver 308. For example, the control unit 202 can steer the vehicle 300 using the steering angle correction 41 when the virtual driver 308 has an error.

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 the towing vehicle 304 and the 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 articulation angle y. Preferably, the trailer vehicle 306 is braked strongly when the articulation angle y is large, i.e. when the trailer vehicle 306 has an alignment that differs greatly from the towing vehicle 304. When the articulation angle y is small, i.e. when the trailer vehicle 306 is aligned essentially identically to the towing vehicle 304, a brake pressure pB on the brake actuators of the trailer vehicle 306 can be reduced. After the vehicle 300 has driven through the curve 336, it again reaches a straight section 356. There, the vehicle 300 behaves stably. In the vehicle control method 1, a stable driving state 342 of the vehicle 300 is therefore determined 49. 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, who here is also the position controller 322 of the vehicle 300 (transfer 51 in Fig. 3 and Fig. 4). Until the next early determination 17 of an unstable driving state 330, the steering remains with the virtual driver 308.

Reference symbol (part of the description)

Vehicle tax procedure

Determining a target trajectory

Determining a target steering angle

Determining an actual size

Actual size

Monitoring a vehicle's position

Determining a trajectory deviation

Determining a trajectory deviation change rate

Early detection of an unstable driving condition

Determining a target yaw rate

Determining a curvature of the target trajectory

Determining a target speed

Determining a yaw rate difference

Determine whether the magnitude of the actual yaw rate in a

Yaw rate tolerance band is

Determine whether the trajectory deviation change rate is increasing

Perform a comparison of actual steering angle and target

Steering angle

Target-actual comparison

Early detection of understeer

Early detection of oversteering

Defining a steering angle correction a Defining a steering angle correction for understeer b Defining a steering angle correction for oversteer

Steering angle correction wheel-individual deceleration

Reducing engine torque

To steer

Determining a stable driving condition

Handing over the steering

Braking a trailer vehicle Vehicle control system

Control unit

Vehicle

Vehicle train

Towing vehicle

Trailer vehicle virtual driver electronically controlled steering

Drive motor

Braking system

Wheels a left front wheel b right front wheel c left rear wheel

Brake actuator

Brake modulator

Position controller

Vehicle network

Drawbar

Road unstable driving condition

Understeer

Oversteer

Curve

Curve start

End of curve stable driving condition

Curves inside

Curves outside

Location

Stability control system

Deceleration of a cornering inner rear wheel illustrative

Arrow

Deceleration of a cornering outer rear wheel illustrative

Arrow 354 Deceleration of a cornering inner front wheel illustrative arrow

355 Deceleration of a cornering outer front wheel illustrative

Arrow

356 straight section ESC Electronic Stability Control FP driving path

Mmot engine torque

01 Surface information

PB brake pressure

SB brake signals

SL steering signals

TSoll Target trajectory

AT Trajectory deviation ATR Trajectory deviation change rate VSoll Target speed

Y articulation angle ölst actual steering angle ösoll target steering angle

K Curvature

M^lst actual yaw rate

'T’Soll Target yaw rate

AM^ Yaw rate difference P Directional error (pin inward direction after cornering (pout outward direction after cornering

Claims

Patent claims 1 . Vehicle control method (1 ) for a vehicle (300) with an electronically controllable steering (310), the vehicle control method (1 ) comprising: Determining (3) a desired trajectory (Tsoii) for the vehicle (300); Determining (5) a target steering angle (ösoii) for traveling the target trajectory (Tsoii); Determining (7) an actual size (9) of the vehicle (300); Early detection (17) of an unstable driving state (330) of the vehicle (300) at least using the actual value (9) and the target trajectory (TSoll); wherein during early detection (17) it is determined whether the unstable driving state (330) is an understeer (332) of the vehicle (300) or an oversteer (334) of the vehicle (300); and in response to the early detection (17) of the unstable driving state (330): Defining (40) a steering angle correction (41) for the target 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 (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 target 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 allowance (özu) if the unstable driving state (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. Method (1) according to 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 target 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 value (9) is an actual yaw rate (M ^J lst) and the early detection (17) of an unstable driving state (330) of the vehicle (300) at least using the actual value (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. 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 an understeer (332) or an oversteer (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 desired trajectory (TSoll); Determining (23) an actual speed (Vlst) of the vehicle (300); Determining the target yaw rate ('- target) 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 ^J Tol) has a width of ± 0.1 °/s to ± 10 °/s, preferably ± 0.5 °/s to ± 2 °/s, around the desired yaw rate (' ^J Soll). 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) if the unstable driving state (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 state (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 a steering angle tolerance value (öTol). 13. Method (1) according to claim 12, wherein the early detection (17) of the unstable driving state (330) if the actual steering angle (ölst) deviates from the target steering angle (öSoll) by at least a steering angle tolerance value (ÖTol) and a trajectory deviation (AT) is determined, comprises: Early detection (37) of understeering (332) of the vehicle (300) if the trajectory deviation (AT) comprises a transverse deviation (Q) directed towards the outside (346) of the curve and a directional error (cp) directed towards the outside (346) of the curve; and Early detection (39) of an oversteer (334) of the vehicle (300) if the trajectory deviation (AT) includes a directional error (<p) directed inwards (344) into curves. 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-directed direction error (cp) when cornering. 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) further comprises in response to the early detection (17) of the unstable driving condition (330): Braking (53) of the trailer vehicle (306), wherein the braking (53) of the trailer vehicle (306) is preferably carried out 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) which is designed to carry out the method (1) according to one of claims 1 to 20. 22. Vehicle (300) comprising an electronically controllable steering system (310), a virtual driver (308) configured to carry out 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 in order to carry out the method (1) according to one of claims 1 to 20 when the computer program product is executed on a computing unit.