DE102016214564A1 - Method and control system for driving dynamics control of a vehicle and vehicle - Google Patents

Abstract

The invention relates to a method and a control system for vehicle dynamics control of a vehicle (1), in particular of a motor vehicle, which is formed with at least one front wheel (2) and at least one rear wheel (3), comprising the steps of: detecting one or more values of at least one for the driving state of the vehicle (1) characteristic size on the vehicle (1) and / or their temporal evolution, determining from detected values of at least one size and / or from their temporal evolution, whether the vehicle (1) is in a drift condition , in the presence of a drift condition controlled exertion of a braking force on the at least one front wheel (2), wherein a measure and / or a time course of the braking force are so selected and / or controlled or regulated set or are that over a resulting Radlängskraft ( FxV) and via a slip angle (β) a wheel lateral force (FyV) on the at least one front wheel (2) forms and thereby the yaw acceleration (Ψ ..) of the vehicle (1) does not rise and in particular temporarily decreases.

Description

The present invention relates to a method for vehicle dynamics control of a vehicle, a vehicle dynamics control system and a vehicle. In particular, the present invention also relates to a method and a control system for driving dynamics control of a motor vehicle and a motor vehicle as such.

In the field of vehicle technology and especially in motor vehicles, driver assistance systems generally enjoy increasing popularity. Known driver assistance systems are intended to increase ride comfort and driving safety. Thus, ESP systems and DSR systems are provided to increase the stability of vehicle tools in operation. Such systems often intervene when a driving-critical situation is just starting, so that a driving risk, especially for the inexperienced driver, is avoided from the outset.

On the other hand, there are driving situations in which such intervention is perceived as too restrictive and patronizing. This particularly concerns the savvy or sporty driver who wants to experience driving situations in a wider dynamic range, for example a state of drifting of the vehicle.

Previous driver assistance systems are not able to allow such dynamic limits on the one hand and on the other hand to ensure the necessary driving safety.

The invention is based on the object to provide a method and a system for driving dynamics control of a vehicle and a vehicle as such, in which an operation in an extended range of vehicle dynamics is possible without compromising the driving safety must be accepted.

The object underlying the invention is in a method for vehicle dynamics control of a vehicle according to the invention with the features of independent claim 1, in a system for vehicle dynamics control according to the invention with the features of independent claim 7 and in a vehicle according to the invention with the features of independent claim solved. Advantageous developments are the subject of the respective dependent claims.

• (S1) Erfassen eines oder mehrerer Werte mindestens einer für den Fahrzustand des Fahrzeugs charakteristischen Größe am Fahrzeug und/oder von deren zeitlicher Entwicklung,
• (S2) Bestimmen aus erfassten Werten der mindestens einen Größe und/oder aus deren zeitlicher Entwicklung, ob sich das Fahrzeug in einem Driftzustand befindet,
• (S3) beim Vorliegen eines Driftzustandes gesteuertes Ausüben einer Bremskraft auf das mindestens eine Vorderrad (2),

wobei ein Maß und/oder ein zeitlicher Verlauf der Bremskraft so gewählt und/oder gesteuert oder geregelt eingestellt sind oder werden, dass sich über eine sich ergebende Radlängskraft (F_xV) und über einen Schwimmwinkel (β) eine nicht verschwindende Radquerkraft (F_yV) an dem mindestens einen Vorderrad (2) ausbildet und dadurch die Gierbeschleunigung (Ψ ..) des Fahrzeugs (1) nicht ansteigt und insbesondere temporär sinkt. According to a first aspect of the present invention, a method is provided for vehicle dynamics control of a vehicle, in particular of a motor vehicle, which is formed with at least one front wheel and at least one rear wheel, with the steps:

• (S1) detecting one or more values of at least one characteristic of the driving condition of the vehicle on the vehicle and / or of its temporal evolution,
• (S2) determining from detected values of the at least one size and / or from their temporal evolution whether the vehicle is in a drift state,
• (S3) in the presence of a drift condition controlled exerting a braking force on the at least one front wheel ( 2 )

wherein a measure and / or a chronological progression of the braking force are selected and / or controlled or regulated in such a way that a non-vanishing wheel transverse force (F _yV ) is obtained via a resulting longitudinal wheel force (F _xV ) and via a _slip angle (β) on the at least one front wheel ( 2 ) and thereby the yaw acceleration (Ψ ..) of the vehicle ( 1 ) does not rise and in particular sinks temporarily.

A key aspect of the present invention is first to determine the presence or absence of a drift condition of the vehicle, and to take additional measures aimed at keeping the vehicle quasi-stable in drift condition only in the event that a drift condition already exists on the vehicle.

This is inventively achieved in that in the presence of a drift state in a controlled manner, a braking force is exerted on one or more front wheels of the vehicle. The braking force results in respect of the respective front wheel to a longitudinal wheel force and the present in the drift state slip angle as a function of its size to a tire force that exerts a lateral force by the front wheel angle with respect to the vehicle longitudinal axis.

This intentionally generated by the braking transverse traction leads in connection with the equation of motion of the vehicle and the newly adjusting moment equilibrium to a damping of the yaw acceleration and thus to suppressing a further increase in the yaw rate of the vehicle.

As a result, the yaw rate of the vehicle is stabilized. This means that the critical state, namely the drift state, of the vehicle is also stabilized, or at least not deliberately reduced. An overshoot of the vehicle in one or the other direction with respect to the slip angle is thereby prevented and the occurrence of the drift condition can be fully savored.

In a preferred embodiment, the measure-or, for example, in terms of intensity or intensity-and / or the chronological course of the braking force are selected and / or controlled or regulated such that the yaw acceleration Ψ of the vehicle is set to zero is set and / or temporarily assumes negative values.

Depending on parameters of the vehicle, the environment and / or the driver, dynamic ranges for the operation of the method according to the invention can be defined.

Thus, it is provided according to another embodiment of the method according to the invention, that the degree and / or the time course of the braking force are so selected and / or controlled or regulated set, or thereby, that the yaw rate Ψ. of the vehicle in a range between a predetermined first, lower threshold Ψ. ₁ and a predetermined second, higher threshold Ψ. _{2 is} set or will.

The degree of drift is writable and identifiable among others via the slip angle.

The slip angles are also suitable for adjusting the dynamic range for the method according to the invention.

For this purpose, it may be provided in another embodiment of the method according to the invention, that the measure and / or the time course of the braking force are selected and / or controlled or regulated, or thereby, that thereby the slip angle difference Δα _c between a slip angle α _{V of} a front wheel of the vehicle and a slip angle α _{H of} a rear wheel of the vehicle assumes or retains a negative value, in particular in a range between a first, lower threshold Δα ₁ and a second, higher threshold Δα ₂ .

There are various ways to detect the presence or absence of a drift condition of the vehicle.

• (A) eine Schräglaufwinkeldifferenz Δα_c zwischen einem Schräglaufwinkel α_V eines Vorderrades des Fahrzeugs und einem Schräglaufwinkel α_H eines Hinterrades des Fahrzeugs zu einem oder zu mehreren Zeitpunkten negative Werte annimmt und
• (B) für alle negativen Werte der Schräglaufwinkeldifferenz Δα_c die Gierrate Ψ . des Fahrzeugs zu einem oder zu mehreren Zeitpunkten Werte in einem Bereich zwischen einem dritten, niedrigeren Schwellenwert Ψ .₃ und einem vierten, höheren Schwellenwert Ψ .₄ annimmt.

In a particularly advantageous development of the method according to the invention, the presence of a drift condition in the vehicle is detected in step S2 if

• (A) assumes a skew angle difference Δα _c between a slip angle α _{V of} a front wheel of the vehicle and a slip angle α _{H of} a rear wheel of the vehicle at one or more times negative values, and
• (B) for all negative values of the skew angle difference Δα _c the yaw rate Ψ. of the vehicle at one or more times, values in a range between a third, lower threshold Ψ. ₃ and a fourth, higher threshold Ψ. ₄ assumes.

In order to detect the presence or absence of a drift condition and to ensure its stability, different measured variables can be detected on the vehicle, which characterize the current driving condition of the vehicle.

• – eine Gierrate (Ψ .) des Fahrzeugs (1),
• – eine Querbeschleunigung des Fahrzeugs (1),
• – eine Raddrehzahl eines oder mehrerer Räder (2, 3) des Fahrzeugs (1),
• – eine Lenkkraft und insbesondere eine Zahnstangenkraft des Fahrzeugs (1),
• – einen Schräglaufwinkel (α_V) eines Vorderrades (2) des Fahrzeugs (1),
• – einen Schräglaufwinkel (α_H) eines Hinterrades (3) des Fahrzeugs (1),
• – einen Schwimmwinkel (β) des Fahrzeugs (1) und/oder
• – einen Lenkwinkel (α_V) eines Rades des Fahrzeugs.

In a preferred embodiment of the method according to the invention, it is thus provided that one or more values of one or more of the following variables are detected in step (S1) of the detection:

• A yaw rate (Ψ) of the vehicle ( 1 )
• A lateral acceleration of the vehicle ( 1 )
• A wheel speed of one or more wheels ( 2 . 3 ) of the vehicle ( 1 )
• A steering force and in particular a rack force of the vehicle ( 1 )
• A slip angle (α _V ) of a front wheel ( 2 ) of the vehicle ( 1 )
• A slip angle (α _H ) of a rear wheel ( 3 ) of the vehicle ( 1 )
• A slip angle (β) of the vehicle ( 1 ) and or
• - A steering angle (α _V ) of a wheel of the vehicle.

For the purposes of the present invention, a detection means a direct or indirect determination by measurement, if appropriate involving calculation and / or estimation algorithms.

According to a further aspect of the present invention, a system is also provided for vehicle dynamics control of a vehicle, in particular of a motor vehicle which is designed with at least one front wheel and at least one rear wheel which is set up, uses a method according to the invention and / or in such a method become.

• (I) eine Einheit zum Erfassen eines oder mehrerer Werte mindestens einer für den Fahrzustand des Fahrzeugs charakteristischen Größe am Fahrzeug und/oder von deren zeitlicher Entwicklung,
• (II) eine Einheit zum Bestimmen – aus erfassten Werten der mindestens einen Größe und/oder aus deren zeitlicher Entwicklung – ob sich das Fahrzeug in einem Driftzustand befindet,
• (III) eine Einheit zum gesteuerten Ausüben einer Bremskraft auf das mindestens eine Vorderrad beim Vorliegen eines Driftzustandes,

auf. In an advantageous development of the system according to the invention, this has

• (I) a unit for detecting one or more values of at least one characteristic variable of the vehicle on the driving condition of the vehicle and / or of its temporal evolution,
• (II) a unit for determining - from detected values of at least one size and / or their evolution over time - whether the vehicle is in a drift condition,
• (III) a unit for controlled application of a braking force to the at least one front wheel in the presence of a drift condition,

on.

The system is advantageously set up to select a measure and / or a chronological progression of the braking force and / or to set or control it in such a way that a non-disappearing transverse force _component F _yV at the front axle is obtained via a resulting longitudinal wheel force F _xV and over a _slip angle β , in particular on which forms at least one front wheel and thereby the yaw acceleration Ψ .. of the vehicle does not rise and in particular temporarily decreases.

Furthermore, the present invention also provides a vehicle and in particular a motor vehicle. The key aspect of the vehicle according to the invention is the provision of a control system according to the present invention. In operation, the vehicle according to the invention is thus able to detect a drifting state of the vehicle and to activate measures which maintain this drift state quasi-stable in order to assist the driver in a sporty driving mode.

• – ein oder mehrere Fahrzustandsgrößen zur Ermittlung eines Fahrzeugistzustandes, zum Beispiel eine Querbeschleunigung und/oder eine Gierrate,
• – ein oder mehrere Fahrzustandsgrößen zur Ermittlung eines Fahrzeugsollzustandes, insbesondere analog zum Fahrzeugistzustand, und/oder
• – der Schwimmwinkel, beispielsweise durch einen Beobachter,

erfasst werden. Additionally or alternatively, the following aspects can also be taken up:
To detect a drift condition can

• One or more driving state variables for determining a vehicle actual state, for example a lateral acceleration and / or a yaw rate,
• One or more driving state variables for determining a desired vehicle state, in particular analogously to the vehicle actual state, and / or
• The float angle, for example by an observer,

be recorded.

• – ein Lenkwinkel und/oder
• – eine Zahnstangenkraft, beispielsweise durch eine Beobachter,

erfasst werden To detect the influence of the front wheel forces can

• A steering angle and / or
• A rack-and-pinion force, for example by an observer,

be recorded

To limit the yaw acceleration can be built by a braking engagement of the inside or outside of the curve front wheel a one or a turning yaw moment.

The yaw moment depends on a limit yaw acceleration, which can be determined, for example, by application.

The extent of the braking force to be exerted can be determined by the moment equilibrium around the vehicle's vertical axis while specifying the yaw limit acceleration. Brief description of the figures

Further details, features and advantages of the invention will become apparent from the following description and the figures.

1A and 1B show a schematic plan view in Einspurmodell a vehicle according to the invention and give explanations to the driving dynamics descriptive quantities.

2 and 3 describe in schematic plan view in Einspurmodell a vehicle in a normal driving condition and in a stabilized according to the invention drift condition.

4 shows in the manner of a tree diagram a comparison of the procedure according to the invention to a conventional driver assistance system or to a system not supported by a system.

5 shows in the manner of a flowchart an embodiment of the method and system for vehicle dynamics control of a vehicle according to the invention.

6 and 7 show aspects of a regulation that is in the in 5 shown methods can be realized.

The following are with reference to the 1 to 7 Embodiments of the invention described in detail. Identical and equivalent as well as equivalent or equivalent elements and components are designated by the same reference numerals. Not in every case of their occurrence, the detailed description of the designated elements and components is reproduced.

The illustrated features and other properties can be isolated in any form from each other and combined with each other, without departing from the gist of the invention.

The 1A and 1B show a schematic plan view of a single-track model according to the invention a vehicle 1 ,

On the basis of this schematic representation different variables are explained and defined, which are used to detect a driving condition of a vehicle 1 and can be used to influence it.

In the in the 1A and 1B used Einspurmodell be next to the vehicle mass m and the position of the center of gravity S of the vehicle 1 by taking the mass m of the vehicle 1 is thought concentrating, nor the vehicle's longitudinal axis 4 and a representative front wheel 2 and a rear wheel 3 used as components.

In the situations of 1A and 1B is the model vehicle 1 with front wheel 2 , Rear wheel 3 and vehicle longitudinal axis 4 with its center of mass S concentrated driving mass m in cornering with a curve center or instantaneous center M and a turning radius R to the center of gravity S. The front wheel 2 is a steering angle δ _V to the vehicle longitudinal axis 4 taken.

Due to the vehicle speed V when cornering in a corresponding dynamic range is a deviation between the direction of the speed V and the direction of the vehicle longitudinal axis 4 in front. The corresponding angular difference is referred to as the slip angle β.

Furthermore, the direction of movement corresponds to the front and rear wheels 2 and 3 not necessarily the current direction of travel. Rather, there is a so-called skew with a respective slip angle α _V for the front wheel 2 or α _H for the rear wheel 3 in front.

Due to its movement, the center of gravity S results in a rotation about the vehicle vertical axis passing through the center of gravity S. The corresponding rotational movement about the center of gravity of the vehicle is referred to as yawing and by the yaw rate Ψ. and described by the yaw acceleration Ψ ..

The distance between the Aufpunkte of front wheel 2 and rear wheel 3 with respect to the center of gravity S of the vehicle 1 are considered as corresponding levers l _V and l _H , at which the Radquerkräfte F _yV for the front wheel 2 and F _yH for the rear wheel 3 attack and so in cooperation with the speed V to a centripetal acceleration a _F with a corresponding total moment J · Ψ .. cooperate.

In 2 the sizes are once again for a normal cornering of the vehicle 1 shown. The resulting wheel lateral forces F _yH for the rear wheel 3 and F _yV for the front wheel 2 lead in conjunction with the levers L _H and L _V between wheel point and center of gravity S of the vehicle 1 about the equation of motion J · Ψ .. = F _yV · 1 _V - F _yH · 1 _H. (1) in steady state to a moment equilibrium.

3 explains the so-called drift condition, which is stabilized by that on the front wheel 2 by braking with a braking force initially a longitudinal force F _xV on the front wheel 2 is applied, which leads over the steering angle δ _V to a tire lateral force, which increases quantitatively from the steering angle δ _V F _xV l · _V · sin (δ _V). (2a) certainly.

By selecting the mode of braking the front wheel, the drift state can be kept virtually stable dynamically in a feedback manner. In particular, a further and excessive screwing in of the vehicle and, in the case of a corresponding steering movement, counterbending is prevented according to the invention.

Since a driving condition is dependent on the steering movement even in an oversteer situation, the described concept can be coupled with steering torque recommendations.

Decisive in the context of the invention is the recommendation not to carry out a counter-steering movement beyond the necessary extent, in particular in order to reduce the intensity of a counter-pendulum.

The extension of a DSR functionality would be conceivable, with a counter-steering torque (applicative) is built up from a steering angle (applicative) in the area of the slip angle, which signals the driver at a coated steering movement damping.

4 shows schematically in the manner of a block diagram and quasi in tabular form different operating modes for driver assistance in a vehicle according to the invention.

In particular, the yaw rate, the lateral acceleration, the wheel speed and the steering force or rack-and-pinion steering force are determined on the vehicle in section T0.

Then, it is determined in the section T1 whether the beginning of oversteer is present or pending.

Then, an intervention strategy is selected based on various criteria in section T2. The various criteria also include the or switching off corresponding driver assistance components, for example in the cockpit of the vehicle.

According to a first strategy, for example, in section T4, an ESP system may be on. The objective of an ESP system is the avoidance of oversteer. By deliberately influencing steering, braking and / or the engine, it is attempted to keep the skew angle difference Δα _c = α _V -α _H strictly positive, so that the condition Δα _c ≥ 0 is fulfilled. The intervention takes place by corresponding braking on one or more front wheels 2 for limiting the yaw rate Ψ. and / or the slip angle β and the reduction of the vehicle speed V.

Alternatively, according to section T5, the ESP system and any other system may be disabled. In this case, the control of the vehicle dynamics takes place solely by the manipulations, braking and / or motor control taken by the driver. A system intervention in automatic or semi-automatic manner is not provided in this driving mode.

According to the invention, an intervention according to section T3 only takes place when a drift condition exists and is also intended.

The objective here is, inter alia, the avoidance of so-called Gegenpendelbewegungen. This is achieved by the yaw rate Ψ. is set below a threshold, namely in the event that there is a drift, ie that the cross-angle difference has negative values, namely according to the relationship Ψ. ₁ ≤ Ψ. ≤ Ψ. ₂ , if only Δα _c <0.

The intervention is carried out by a corresponding Bremsaktuierung on one or more front wheels 2 for damping the yaw rate reduction.

5 show in the manner of a flow chart an embodiment of the method and system for vehicle dynamics control.

After an initial start phase, it is checked in an initial step S0 whether the implementation of a driving assistance in the so-called drift mode is even desired. If this is the case, a transition to the subsequent processing step S1 takes place. On the other hand, if it is manifest that the drift mode is not desired, for example, by setting or not setting a corresponding flag, then the processing flow returns to the final step and corresponding to a return to a main processing.

If, on the other hand, a driving dynamics assistance in the drift mode is desired, the processing follows with the step S1, namely the detection of one or more values of at least one for the driving state of the vehicle 1 characteristic size on the vehicle 1 and / or their evolution over time.

This processing step S1 has a first sub-step S1-1 with the actual acquisition of measured values and a second sub-step S1-2 for the evaluation and intermediate evaluation of the detected values.

In the subsequent step S2, it is checked whether a drift condition exists.

If it is determined in step S2 that there is no drift state, then a transition back to step S0 takes place and offers the possibility that the process will leave again, e.g. when the flag of a desire for the drift mode is not set or has been reset meanwhile.

On the other hand, in step S2, it is determined from the detected values of the at least one variable and / or from their temporal development that the vehicle is moving 1 is in the drift state, so in particular from the evaluation of yaw rate and cross angle angle difference, the following processing step S3 follows the controlled exerting a braking force on the front wheel or the front wheels.

For this purpose, in a first substep S3-1, the determination of the measure and / or a time profile of the braking force to be exercised takes place.

In the subsequent substep S3-2, the degree and / or the time course determined for the braking force are then used to determine the corresponding braking force on a front wheel 2 or the front wheels 2 exercise. It can be different front wheels 2 also be acted upon with different braking forces, depending on whether they are arranged in connection with a Kurverfahrt on the inside of the curve or the outside of the curve, possibly also taking into account other parameters, such as the road surface, the slip and so on.

After exerting the braking force, a return to step S0 ensues, with renewed detection of the measurement values currently representative of the driving state of the vehicle.

In connection with the first sub-step S3-1 for determining the degree and / or a time profile of the braking force to be exerted, various control-loop aspects can also be realized. These are exemplary in the Representations of 6 and 7 shown, which possible details of step S3-1 from the sequence according to 5 illustrate, being a state of the vehicle 1 under drift conditions.

An alternative to calculating the necessary braking forces on the front axle is the specification of a yawing moment to a control unit 4 , Eg an ESP control unit, which performs the calculation of a brake force distribution.

These and other features and characteristics of the present invention will be further elucidated with reference to the following statements:
In the field of dynamic driving situations, on the one hand, oversteer situations due to nonlinearities of the tire side force behavior are regarded as demanding driving tasks. At the same time, the performance of the developed passenger cars is steadily increasing.

To support the - especially athletic - driver in driving physics critical driving situations in the vehicle control, there are already various stability functions, such as the ESP with wheel-specific braking interventions and the DSR with steering torque recommendations.

Conventional solutions for controlling an oversteer situation always have the goal of counteracting oversteer. A situation of oversteer before their training already counteracted and thus prevented in their creation.

Interventions by the ESP reduce e.g. while driving the vehicle and thus by the decreasing speed of the criticality of the driving situation.

Interventions in the steering torque, however, give the driver a steering direction recommendation in order to counteract the oversteer situation by countersteering in the direction of the slip angle.

Both solutions help the driver to prevent entry into an oversteer situation in advance or to leave an existing oversteer situation. Consequently, the previous measures do not allow for a stable drift condition, but the achievement of a drift condition is prevented in advance.

While in pure steering torque recommendations, the driver may be overwhelmed by large steering angle and steering angle speeds, a stabilization by consistent speed reduction in the ESP is perceived as patronizing and is at the expense of driving pleasure.

When steering torque recommendations continue to be the risk of motivating a driver to large steering movements. These can provoke an overreaction of the vehicle and cause a Gegenpendelbewegung the vehicle, which is usually much more safety-critical than the actual oversteer situation.

In order to solve the stated problem, the inventive concept by combining steering and braking interventions assists the driver in maintaining a quasi-stable drift condition.

Assuming a drift situation in which a - in particular sporty - driver performs a counter-steering movement on or in the direction of the slip angle, a longitudinal force intervention on the wheels of the front axle regulates the balance of power to the vehicle's vertical axis.

For a more detailed description of the functioning in the 2 and 3 described example driving conditions described. The vehicle 1 is represented here in a one-track model.

2 schematically describes a cornering of a vehicle 1 in which the tires 2 and 3 are in the static friction region and thus have a more linear tire side force behavior.

In moment equilibrium and results in the following relationship as the equation of motion of the considered vehicle 1: J · Ψ .. = F · l _{yV V} * cos (δ _V) - F _{y H} * l _H. (1)

Here denote Ψ .. the yaw acceleration, so the second time derivative of the yaw angle Ψ, ie the vehicle angle about the vehicle vertical axis z in the vehicle center of gravity M, which is also referred to as yaw axis, J is the moment of inertia of the vehicle 1 around the yaw axis, F _yV the lateral force on the front wheels 2 of the vehicle 1 , F _yH the lateral force on the rear wheels 3 of the vehicle 1 , ie in each case the y component of the total force in the reference system of the vehicle 1 , and L _V and L _{H are} the respective lever _{lengths of} the levers, among which the _lateral forces F _yV and F _yH on the vehicle 1 attack and thereby generate the moments. The _lateral forces F _yV and F _yH on the vehicle are also referred to as tire side forces.

Reach the tire _{side forces} F _yH on the wheels 3 the rear axle, the sliding friction range, the ratio of skew angle to tire side force increase increases. Increases the slip angle of the wheels 3 the rear axle now stronger than at the wheels 2 the front axle, so there is a negative skew angle difference.

There is then an oversteer situation like this in 3 is shown.

To further screw in the vehicle 1 and thus to prevent a spin, conventionally, a counter-steering movement in the direction of the slip angle β can be performed.

But it is by the front wheel angle of the slip angle at the wheels 2 compensated for the front axle, the moment F _yV · l _V due to the _{traction force} F _yV in the above equation is very low and in particular zero.

The remaining balance of forces and moments between yaw moment and rear axle lateral force influence is then highly unstable due to the non-linearity of tire side force behavior in the sliding friction area.

Up to a limit yaw rate, the tire side force on the wheels of the rear axle results in a yawing yaw. This countervailing yaw motion requires a corresponding driver response to prevent the vehicle from spinning in the opposite direction.

The concept according to the invention consists, inter alia, of damping this countermovement by means of a longitudinal force control on the wheels of the front axle. Due to the influence of force component F _xV applied _{according to the invention} , a new equilibrium of forces then results around the vertical axis.

This balance of forces and moments is given by the equation J · Ψ .. = F · l _{xV V} * sin (δ _V) - F _{y H} * l _H. (2) described, while F _{xV is} the one by a brake on the front wheels 2 imprinted force as longitudinal force with respect to the respective wheel 2 the front axle. From the angular relationship with the steering angle δ _V , ie from the wheel position during braking in the drift condition, a resulting lateral force now results on the front axle, so that the yaw acceleration Ψ .. remains controllable and not at a quasi-stationary value for the yaw rate Ψ .. not grows and in particular is lowered to about zero and remains there.

The aim of the longitudinal force control according to the invention is to dampen the yaw acceleration Ψ .. by braking force interventions - for example by a suitable functionality of an electric brake booster - which, with the driver's intention, keeps the oversteer situation stable and the existing yaw rate is stabilized.

It is important that it is possible to leave the drift state. The stabilization or damping refers to the Gegenpendelbewegung that is to be damped to prevent the spin in the other direction. Only getting an oversteer situation alone would possibly lead to leaving the target travel trajectory.

In contrast to the concepts of previous stability programs, the goal is thus not to bring about a reduction in driving state criticality through speed-reducing brake interventions.

Rather, it is about a targeted braking intervention on the wheels of the front axle, which leads by the force component in the vehicle transverse direction to a quasi-stable drift condition. The force component in the vehicle longitudinal direction also leads to a speed reduction, which is minimized to maximize the curve passing speed.

These measures therefore increase the sportiness and fun of driving.

Although the aspects and advantageous embodiments of the invention have been described in detail with reference to the embodiments explained in connection with the accompanying drawings, modifications and combinations of features of the illustrated embodiments are possible for the skilled person, without departing from the scope of the present invention, the scope of protection the appended claims are defined.

LIST OF REFERENCE NUMBERS

1

vehicle

2

front

3

rear wheel

4

Control unit, ESP control unit

F _yV

Transverse force / lateral force Front wheel

F _xV

Longitudinal force front wheel

J

Vehicle moment of inertia about yaw axis

l _H

lever length

l _V

lever length

m

vehicle mass

M

Turning center

R

Curve radius with respect to the vehicle center of gravity S

S

Center of gravity

V

vehicle speed

α _H

Slip angle rear wheel

α _V

Slip angle front wheel

β

float angle

δ _V

steering angle

Δα ₁

 Threshold skew angle difference

Δα ₂

 Threshold skew angle difference

Δα _c

 Slip angle difference

Ψ 

yaw rate

Ψ  ₁

Threshold yaw rate

Ψ  ₂

Threshold yaw rate

Ψ  ₃

Threshold yaw rate

₄

Threshold yaw rate

Ψ 

yaw acceleration

Claims (9)

Method for driving dynamics control of a vehicle ( 1 ), in particular a motor vehicle, which with at least one front wheel ( 2 ) and at least one rear wheel ( 3 ), comprising the steps of: (S1) detecting one or more values of at least one of the driving state of the vehicle ( 1 ) characteristic size on the vehicle ( 1 ) and / or from their temporal evolution, (S2) determining from detected values of the at least one variable and / or from their temporal evolution, whether the vehicle ( 1 ) is in a drift state, (S3) in the presence of a drift state controlled exerting a braking force on the at least one front wheel ( 2 ), wherein a measure and / or a time course of the braking force are selected and / or controlled or regulated set or that a non-vanishing Radquerkraft (F. _B. ) over a resulting Radlängskraft (F _xV ) and over a _slip angle (β) _yV ) on the at least one front wheel ( 2 ) and thereby the yaw acceleration (Ψ ..) of the vehicle ( 1 ) does not rise and in particular sinks temporarily. Method according to Claim 1, in which the extent and / or the chronological progression of the braking force are or are / are set and / or controlled in such a way that the yaw acceleration (Ψ ..) of the vehicle ( 1 ) is set to zero and / or temporarily assumes negative values. Method according to one of the preceding claims, in which the degree and / or the chronological progression of the braking force are or are set and / or controlled or regulated such that thereby the yaw rate (Ψ) of the vehicle ( 1 ) is set in a range between a predetermined first lower threshold value (Ψ ₁ ) and a predetermined second higher threshold value (Ψ ₂ ). Method according to one of the preceding claims, in which the degree and / or the chronological progression of the braking force are or are set and / or controlled or regulated such that the slip angle difference (Δα _c ) between a slip angle (α _V ) of a front wheel ( 2 ) of the vehicle ( 1 ) and a slip angle (α _H ) of a rear wheel ( 3 ) of the vehicle ( 1 ) assumes or retains a negative value, in particular in a range between a first, lower threshold (Δα ₁ ) and a second, higher threshold (Δα ₂ ). Method according to one of the preceding claims, in which, in step S2, the determination of the presence of a drift condition in the vehicle ( 1 ) is detected when (A) a skew angle difference (Δα _c ) between a slip angle (α _V ) of a front wheel ( 2 ) of the vehicle ( 1 ) and a slip angle (α _H ) of a rear wheel ( 3 ) of the vehicle ( 1 ) assumes negative values at one or more times and (B) for all negative values of the slip angle difference (Δα _c ) the yaw rate (Ψ.) of the vehicle ( 1 Accepts) to one or more points in time values (in a range between a third, lower threshold value Ψ. ₃₎ and a fourth, higher threshold value (Ψ. _4). Method according to one of the preceding claims, in which in step S1 of the detection one or more values of one or more of the following quantities are detected: a yaw rate (Ψ) of the vehicle ( 1 ), - a lateral acceleration of the vehicle ( 1 ), - a wheel speed of one or more wheels ( 2 . 3 ) of the vehicle ( 1 ), - a steering force and in particular a rack force of the vehicle ( 1 ), - a slip angle (α _V ) of a front wheel ( 2 ) of the vehicle ( 1 ), - a slip angle (α _H ) of a rear wheel ( 3 ) of the vehicle ( 1 ), - a slip angle (β) of the vehicle ( 1 ), - a steering angle (δ _V ) of a wheel ( 2 . 3 ) of the vehicle ( 1 ). Vehicle dynamics control system of a vehicle ( 1 ), in particular a motor vehicle, which with at least one front wheel ( 2 ) and at least one rear wheel ( 3 ) configured to carry out a method according to any one of claims 1 to 6. The system of claim 7, comprising: (I) a unit for detecting one or more values of at least one of the driving condition of the vehicle Vehicle ( 1 ) characteristic size on the vehicle ( 1 ) and / or its development over time, (II) a unit for determining - from detected values of the at least one size and / or from their time evolution - whether the vehicle ( 1 ) is in a drift state, (III) a unit for the controlled exertion of a braking force on the at least one front wheel ( 2 ) in the presence of a drift condition, wherein the control system is arranged to select a measure and / or a time profile of the braking force so and / or controlled or regulated that over a resulting Radlängskraft (F _xV ) and a float angle (β ) a non-vanishing Radquerkraft (F _yV ) on the at least one front wheel ( 2 ) and thereby the yaw acceleration (Ψ ..) of the vehicle ( 1 ) does not rise and in particular sinks temporarily. Vehicle ( 1 ) and in particular motor vehicle with a system according to claim 7 or 8.

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