DE102014211061A1 - Method and device for regulating the driving stability of a vehicle - Google Patents

Abstract

A method for controlling the running stability of a vehicle, wherein a yaw rate control intervention is performed in dependence on a difference between a yaw rate of a reference model and a yaw rate of the vehicle, is intended to further reduce the risk of skidding accidents. For this purpose, it is provided that in the presence of at least one intervention condition additionally a brake control intervention is performed, and wherein there is an engagement condition when a driving deviation of the driver specification of the vehicle behavior exceeds a predetermined deviation limit.

Description

The invention relates to a method for controlling the driving stability of a vehicle, wherein a yaw rate control intervention takes place as a function of a difference between a yaw rate of a reference model and a yaw rate of the vehicle. It further relates to a corresponding device.

The Electronic Stability Program (ESP) is now standard on modern vehicles and can significantly reduce the risk of the car breaking or skidding. The targeted braking of individual selected wheels can be counteracted understeer or oversteer or skidding of the vehicle by deliberately increasing or decreasing the radius of curvature.

ESP includes several features such as ARP (Anti-Roll-Over Protection), TCS (Traction Control System), TSC (Trailer Stability Control), but above all AYC, a yaw rate controller that determines the position of the steering wheel from which the driver's request is derived can be compared with the determined from vehicle inertial sensors actual yaw rate of the vehicle and engages in deviations on the wheels with a brake intervention, where a corresponding moment to increase or decrease the yaw rate can be established. Depending on the vehicle manufacturer, the ESP is designed differently.

From the DE 100 24 656 B4 is a method for controlling the driving stability of a vehicle is known in which to increase the driving stability of the vehicle active yaw moments are generated.

The basic idea in the known interpretations of methods for driving stability control, however, is always to regulate the yaw rate of the motor vehicle and, as far as possible, not to reduce any speed. A reduction in the vehicle speed is therefore regarded only as an undesirable side effect of targeted braking interventions.

Despite the increasing equipment rates of motor vehicles with ESP, the number of accidents that are caused by skidding or breaking out of the vehicle, especially on rural roads, continues to be high or even rising again.

The invention is therefore based on the object to improve a method mentioned above to the effect that the risk of skidding accidents can be further reduced. Furthermore, an apparatus for carrying out a method improved in this way is to be specified.

With regard to the method, this object is achieved according to the invention in that, in the presence of at least one intervention condition, additionally a brake control intervention is performed, and wherein an intervention condition exists when a driver deviation of the driver specification from the vehicle behavior exceeds a predetermined deviation limit value.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that the intervention of the conventional ESP or ESC in critical situations in which a spinning or breaking out of the vehicle threatens, although it can make a significant and important contribution to accident prevention by the controllability of the vehicle again improved. On the other hand, the current accident figures show that there is still potential and demand for a further reduction of the accident risk.

The intervention of the conventional ESP is trying to stabilize the course of the vehicle. As has now been recognized, however, a superimposed, simultaneous reduction of the vehicle speed in the vast majority of cases can lead to a further mitigation of the emergency situation.

As further explained on this basis, not only the reduction of the vehicle speed can be achieved by such a method, but the method can be further differentiated by not only the strength of the ESP intervention but also the type of (ESP) intervention on vehicle sizes, in particular Steering wheel angle and pedal position to be adjusted. This is done by one or more intervention conditions, with which different scenarios can be mapped.

If the steering wheel angle position differs significantly from the vehicle course or exceeds the physically possible, d. H. If it leads to vehicle behavior that can no longer be controlled by autonomous control interventions, it can or must be assumed that the danger situation is no longer controllable. In such a case, it makes sense to brake as much as possible while maintaining the yaw compensation on all wheels. By reducing the speed while trying to achieve the desired yaw rate, the driver can again be given room to maneuver in order to avoid an accident.

In the present case, a braking control intervention is understood to mean an active construction of brake pressure or an active generation of braking torque in such a way that the vehicle speed is significantly reduced, at least more than by a typical ESC intervention in which the reduction of vehicle speed is an undesirable side effect. The brake control intervention thus aims at braking or deceleration of the vehicle, in particular a strong deceleration up to a full braking is included.

The exceeding of a limit refers in the context of the application in each case to the strength of a size, ie the amount exceeded, z. B. from a driving instruction predicted by a vehicle reference model driving behavior. Exceeding the limit value of a deviation is therefore also understood if both variables have negative signs.

Advantageously, the strength of the brake control intervention depends on the strength of the driving deviation. Preferably, the strength of the braking intervention increases with increasing driving deviation. The greater the driving deviation, the greater the likelihood that the driver loses control of the vehicle, so that the situation can be defused by a strong deceleration.

An intervention condition is preferably present when the driver operates the brake pedal with a predetermined pedal travel and / or predetermined pedal travel speed or exceeds a predetermined limit value. The pedal operation expresses the driver's desire to actively brake the vehicle so that it can be assisted by the braking intervention in it.

In this case, the deviation limit value is advantageously lowered from the deviation limit value corresponding to the case where the brake pedal is not operated at a predetermined pedal travel and / or pedal travel speed. h., even with minor deviations is actively carried out the brake control intervention.

An intervention condition is preferably present when the steering wheel angle set by the driver exceeds a predetermined limit value. This limit value may in particular also be dependent on further driving dynamics parameters, such as, for example, the speed of the vehicle and / or the recognized road condition. In particular, when the steering wheel angle signals a physically no longer feasible maneuver, the braking control intervention should take place.

An intervention condition is preferably also present if, due to predictive analysis, the steering wheel angle position would lead to an unstable and / or unrealisable driving situation.

Upon actuation of the accelerator pedal with a predetermined pedal travel and / or predetermined pedal travel speed, the strength of the brake control intervention is advantageously at least partially reduced. This operation signals the driver's desire to actively accelerate the vehicle, so that an excessive brake control intervention would be a hindrance.

Upon actuation of the accelerator pedal with a predetermined pedal travel and / or predetermined pedal travel speed, therefore, the deviation limit value is also preferably increased, so that the brake control intervention takes place only at higher deviations than in normal driving operation.

In a preferred embodiment, upon detection of recurring deviations of the vehicle course from the steering input, the threshold of the intensity of the course deviations, starting from the brake control interventions, is carried out, ie the deviation limit value is reduced. Repeated deviations indicate that the driver can not control the vehicle well, so that the speed of the vehicle is kept low or reduced with the help of conservative brake control interventions.

In the case of manual actuation of a driving dynamics switch by the driver, it is preferably provided that the deviation limit value is increased in relation to the deviation limit value of a standard setting of the vehicle.

The yaw rate control intervention preferably acts on the wheel determined according to an ESC intervention strategy known per se with a brake pressure determined for a yaw rate compensation, wherein at least one further wheel is preferably subjected to brake pressure in order to reduce the vehicle speed.

Particularly preferred and to decouple the braking as well as possible from the yaw compensation, all wheels are additively acted upon by an additional brake pressure by the brake control intervention.

With regard to the device, the above-mentioned object is achieved according to the invention by hardware and / or software implemented means for carrying out a method described above. In particular, it may be an electrohydraulic control unit having a computing unit that controls a number of solenoid valves and a driver-independent pressure source, such as an electric pump or an electrically driven cylinder-piston assembly.

The advantages of the invention are in particular that a further reduction of accidents is made possible by a superposition of a yaw rate control intervention with a brake control intervention. As a result of the associated reduction in vehicle speed, kinetic energy is dissipated or converted into frictional heat in the brakes and is then no longer available in the further course of the critical situation. The dependency of the brake control intervention on one or more engagement conditions or criteria allows the vehicle to continue driving dynamically or sportily, but leads to optimized driver assistance in emergency situations.

The method can be deactivated, for example, by pressing a corresponding button or a switch in the cockpit if necessary, and it should be set as the default mode at ignition restart. On the one hand, such a configuration allows deliberately intended sporty-athletic driving, but intervenes as standard, since the brake control interventions must be actively reduced during operation.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

1 a flowchart of a method for controlling the driving stability of a vehicle in a preferred embodiment,

2 a schematic representation of engagement conditions for the method according to 1 , and

3 an apparatus for performing a method in a preferred embodiment.

Identical parts are provided in both figures with the same reference numerals.

In 1 a method for controlling the driving stability of a vehicle in a preferred embodiment is shown in the form of a flow chart. The procedure starts at startup 2 , In a decision will 6 it is checked whether a yaw rate control intervention is to take place as a function of a difference between a yaw rate of a reference model and a yaw rate of the vehicle. If this is not the case, this will be in the decision 6 again, especially after a predetermined time interval checked.

The method is capable of further reducing the risk of skidding accidents due to the breaking out of the vehicle. If a yaw rate control intervention is made, this will be in a decision 10 Checks whether a driver deviation of the driver's behavior of the vehicle behavior exceeds a predetermined deviation limit, whereby an intervention condition for a brake control intervention is present. If this is not the case, the process branches back to the decision 6 , If a brake control intervention take place, this is in a block 14 performed together with yaw compensation. The method thus effectively performs a superposition of the yaw rate control intervention with a brake control intervention. The yaw rate control intervention takes place in such a way that pressures for individual brakes of the vehicle are determined on the basis of a plurality of input variables and the corresponding pressures are set, for example by means of an ESC or ESP system.

In a decision 20 a check is made as to whether the driver actuates the brake pedal or whether he actuates this faster and / or more strongly than prescribed limit values. If this is the case, it will be in a block 24 the threshold of the vehicle deviation, from which the yaw rate compensation is superimposed with a braking intervention, is reduced compared to the case where neither the gas pedal nor the brake pedal are actuated.

In a decision 28 it is checked whether the driver operates the gas pedal with a pedal travel and / or a pedal speed, each exceeding a predetermined limit or threshold. If this is the case, in block 32 the threshold from which brake control intervention is carried out, compared to the case that neither gas nor brake pedal are operated, increased.

In a decision 36 It is checked whether deviations of the given driving behavior and the actual driving behavior occur frequently, also for this purpose can be defined how often this should be done in a given period of time. If the deviations are correspondingly frequent, this is to be taken as an indication that the driver is unable to control the vehicle well. In a block 40 then the deviation threshold is adjusted, in particular reduced.

The brake control intervention in block 14 can be parallel to the other decisions 20 . 28 . 38 run.

The engagement thresholds for the overlay of the yaw compensation with the brake control intervention can be divided into two areas in a first version of the method. Only a yaw rate control or yaw compensation is performed up to a predefined course deviation of the vehicle course from the course desired by the steering wheel setting. If the deviation is greater than this predetermined deviation, the brake control intervention is also performed.

In 2 is on an axis 50 is schematically the deviation of the driver specification of the vehicle behavior plotted. The boxes or blocks shown in various rows each symbolize the areas in which only a yaw compensation or a yaw compensation with superimposed brake intervention is performed. In a corresponding interpretation of the intervention thresholds or intervention conditions, a distinction can be made between different scenarios:
For very small course deviations, ie for course deviations, in a first predetermined interval up to a limit deviation 54 or a deviation limit is in a range 56 only a yaw rate control or yaw compensation performed. This can be done with the aid of the standard existing in the motor vehicle ESP. For deviations greater than the limit deviation 54 , will be in one area 62 the yaw compensation superimposed with a braking intervention.

The superposition of the braking intervention can also be carried out depending on the pedal position. While in one area 68 again exclusively a yaw compensation takes place, when yawing the brake pedal yaw rate control not only from the limit deviation 54 but already from the limit deviation 70 which is less than the limit deviation 54 , a brake control superimposed. The amount of brake control intervention may be made dependent on the amount of brake pedal depression (as measured by the pedal travel) and / or the gradient that measures the change in the pedal travel over time. Preferably, even with slight actuation of the brake pedal with a high gradient by the brake control intervention, the vehicle is strongly or even delayed maximum.

Furthermore, the deviation, but a brake intervention is performed, be made dependent on the pedal position of the accelerator pedal. By recognizing the intended accelerator pedal operation by the driver, the strength of the brake control intervention can be withdrawn. In this case, a high threshold is preferably set for the strength of the actuation or its gradient, so that the automatic brake control intervention is not prematurely or prematurely reduced or stopped. Only from a limit deviation 82 , which is higher than the limit deviation 54 , a brake intervention or brake control intervention is performed.

For particularly high course deviations, which in turn can be described by a threshold or an interval, the brake control intervention is performed in each case.

If a malfunction is detected more often, ie, for example, within a predetermined time interval exceeding the limit deviation 54 is determined, in the present embodiment, the limit deviation, from which the yaw rate intervention, a braking intervention is superimposed, to a smaller deviation 94 postponed. In one area 92 Again, only the yaw compensation is performed while in one area 98 the overlay with the brake control intervention takes place.

It can also be provided that the driver actively shifts the limit deviation to higher values, for example by activating a driving dynamics switch (sports mode). The limit deviation 106 is higher than the limit deviation after such an activation 54 during normal operation. In one area 104 Again, only one yaw compensation is performed while in one area 110 a brake control intervention is superimposed.

In order to recognize that a steering angle position leads to a vehicle control-dynamic situation of the vehicle which is no longer controllable, a predictive strategy is preferably pursued. Based on the current driving dynamics situation, a predefined time T is predicted for the future as to how the vehicle will behave. In this case, for example, it can also be determined predictively which actuator values (brake pressure, steering angle, etc.) would be necessary in a normal engagement pattern, essentially an ESP intervention or a yaw rate regulation, in order to guide the vehicle stably and safely.

Are the precised values beyond the physically possible, i. H. If the vehicle can no longer be brought into a controlled state by yaw rate control, the above-described escalation of the brake control interventions is carried out.

Both simple linear predictions and predictions on the basis of polynomials or maneuver curves are suitable for the prediction of vehicle behavior. As a basis for the prediction model, the same models as for the intervention can be used to reduce the application effort.

A typical example of a yaw rate that can no longer be implemented physically is when the driver prescribes a strong steering angle jump or a large steering angle at high driving speed. This would normally require a yaw rate Ψ _p that could not be implemented in terms of lateral dynamics, since the lateral acceleration required for this according to the equation a _y = v · Ψ _{p is} well above the physical limit of approximately 1 g would lie (g is the gravitational acceleration). With such a steering input is thus signaled by drivers or expressed that he is in a real emergency situation.

Although the usefulness of braking in such cases depends on many traffic conditions, it can generally be said that a reduction in the driving speed practically always leads to a defusing of the emergency situation. In a preferred embodiment of the method is therefore at a described physically unreachable yaw rate of as many brakes substantially maximum braked, so that the vehicle speed is reduced as quickly as possible.

Another typical example of an ESC no longer or only delayed implementable steering input is when the driver on a road with very low friction (in spite of ESC) gets into an ejection situation and then pretends due to panic overreaction steering angle, the ESC not only can not implement, but also lead to angular positions of the front wheels, where an ESC brake intervention hardly leads to an effective stabilizing torque around the vertical axis of the vehicle, since the line of action of the brake force vector then passes too close or even on the wrong side of the vehicle's center of gravity , The ESC torque M then results according to the formula M = F _b · s, where s the effective lever travel and F _b denotes the braking force, and is small or even gets a wrong sign, the latter case, however, almost impossible for kinematic reasons is.

Even in such situations, an active braking intervention or brake control intervention is advantageously carried out on as many wheels as possible in order to adapt the vehicle dynamics to the lower coefficient of friction of the roadway.

The distribution of the braking forces on the four wheels is preferably as follows. The wheel, which is primarily responsible for the ESC torque control, is subjected to the calculated from the conventional existing ESC algorithm brake pressure. All wheels additively receive an additional brake pressure or are additively loaded with an additional brake pressure, which is determined from the strength of the expected and precisely defined control deviation between the driver's desired yaw rate and the yaw rate that can be reached dynamically as well as from the driver's reaction.

In 3 is a device 120 for performing a method described above schematically. In a yaw rate control module 126 a yaw rate intervention or a yaw compensation is calculated on the basis of the deviation from the measured yaw rate and by a driver request of a certain yaw rate or by a yaw rate predicted by a vehicle reference model. In a brake control module 132 it is checked whether the deviation of the driver specification of the vehicle behavior exceeds a predetermined limit or whether the above-described engagement conditions are met. If this is the case, a brake control intervention is calculated. The two modules 126 . 132 may be preferred over a data connection 138 communicate with each other, so that, for example, the brake control module 132 from the yaw rate control module 126 the information is obtained, which wheels are already subjected to brake pressure with which brake pressure by the yaw rate intervention. The modules 126 . 132 which implement the method described above are preferably implemented by software as software modules on a common architecture. The device 120 is preferably designed as ESP system. The two modules 126 . 132 can also be implemented as a common module.

The device 120 then outputs the calculated brake pressures to a brake pressure adjustment device 140 Next, which actively adjusts the brake pressure at the various wheels.

LIST OF REFERENCE NUMBERS

2

 begin

6

 decision

10

 decision

14

 block

20

 decision

24

 block

28

 decision

32

 block

36

 decision

40

 block

50

 axis

54

 Limiting error

56

 Area

62

 Area

68

 Area

70

 Limiting error

74

 Area

80

 Area

86

 Area

82

 Limiting error

92

 Area

94

 Limiting error

98

 Area

104

 Area

106

 Limiting error

110

 Area

120

 contraption

126

 Yaw rate control module

132

 Brake control module

138

 Data Connection

140

Bremsdruckeinstellvorrichtung

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10024656 B4 [0004]

Claims (13)

A method for controlling the driving stability of a vehicle, wherein in response to a difference between a yaw rate of a reference model and a yaw rate of the vehicle, a yaw rate control intervention, characterized in that in the presence of at least one engagement condition additionally a brake control intervention is performed, and wherein an engagement condition is present a driving deviation ( 50 ) exceeds the driver default of the vehicle behavior a predetermined deviation limit. The method of claim 1, wherein the strength of the brake control intervention depends on the strength of the driving deviation ( 50 ). The method of claim 1 or 2, wherein an engagement condition exists when the driver operates the brake pedal with predetermined pedal travel and / or predetermined pedal travel speed. The method of claim 3, wherein the deviation limit value is lowered from the deviation limit value corresponding to the case that the brake pedal is not operated at a predetermined pedal travel and / or at a predetermined pedal travel speed. Method according to one of claims 1 to 4, wherein an engagement condition is present when the adjusted by the driver steering wheel angle exceeds a predetermined limit. Method according to one of claims 1 to 5, wherein an intervention condition is present if due to predictive analysis, the steering wheel angle position would lead to an unstable and / or unrealizable driving situation. Method according to one of claims 1 to 6, wherein upon actuation of the accelerator pedal with a predetermined pedal travel and / or predetermined pedal travel speed, the strength of the brake control intervention is at least partially reduced. Method according to one of claims 1 to 7, wherein upon actuation of the accelerator pedal with a predetermined pedal travel and / or predetermined pedal travel speed of the deviation limit value is increased. Method according to one of claims 1 to 8, wherein upon detection of recurring deviations of the vehicle heading from the steering input of the deviation limit is reduced. A method according to any one of claims 1 to 9, wherein upon manual operation of a vehicle dynamics switch by the driver, the deviation limit value is increased from the deviation limit value of a default setting of the vehicle. Method according to one of claims 1 to 10, wherein the yaw rate control intervention acts on the wheel with a designated for yaw rate compensation brake pressure, and wherein at least one further wheel is applied to reduce the vehicle speed with brake pressure. The method of claim 11, wherein all the wheels are additively acted upon by an additional brake pressure by the brake control intervention. Contraption ( 120 ) for regulating the driving stability of a vehicle, wherein a yaw rate control intervention takes place as a function of a difference between a yaw rate of a reference model and a yaw rate of the vehicle, characterized by hardware and / or software implemented means ( 126 . 132 ) for carrying out a method according to one of the preceding claims.

Images