DE10325486B4 - Method for regulating the driving stability - Google Patents

Abstract

A method for controlling the driving stability of a vehicle, characterized in that is determined in an unstable driving behavior with a brake engagement on at least one engagement wheel, whether based on variables, the steering angle speed, the steering angle, the lateral acceleration, the yaw rate and / or the reference yaw rate a tendency to a subsequent zero crossing of the yaw rate with further unstable driving behavior of the vehicle is present, and that in this case, a brake overlay intervention takes place when an analysis of at least the two yaw rate signals, namely obtained by means of a yaw rate sensor and in one Vehicle model determined yaw rate reference signal, shows that adapted to the reference yaw rate course approaching a stable driving behavior and / or a stable driving behavior is achieved by the brake overlay intervention.

Description

The invention relates to a method for regulating the driving stability according to the preamble of claim 1.

Violent steering and countersteering actions at z. B. evasive maneuvers, lane changes, freestyle u. Like. Can lead to vehicle instabilities at high friction. For vehicles with a high center of gravity, there is an increased risk of tipping over.

To counteract these vehicle instabilities automatically a variety of driving stability regulations have become known. The term driving stability control unites five principles for influencing the driving behavior of a vehicle by means of specifiable pressures or braking forces in or at individual wheel brakes and by means of intervention in the engine management of the drive motor. This is brake slip control (ABS), which is to prevent the blocking of individual wheels during a braking process, to traction control (ASR), which prevents the spinning of the driven wheels to electronic brake force distribution (EBV), which determines the ratio of braking forces between front wheels. and rear axle of the vehicle to control a tilting control (ARB), which prevents tilting of the vehicle about its longitudinal axis, and a yaw moment control (ESP), which provides stable driving conditions when yawing the vehicle about the vertical axis.

With vehicle is thus meant in this context, a motor vehicle with four wheels, which is equipped with a hydraulic, electro-hydraulic or electro-mechanical brake system. In the hydraulic brake system, a brake pressure can be built up by the driver by means of a pedal-operated master cylinder, while the electro-hydraulic and electro-mechanical brake systems build up a brake force dependent on the sensed driver's brake request. In the following, reference will be made to a hydraulic brake system. Each wheel has a brake, which are each associated with an inlet valve and an outlet valve. Through the intake valves, the wheel brakes are in communication with the master cylinder, while the exhaust valves lead to a non-pressurized container or low pressure accumulator. Finally, there is still an auxiliary pressure source available, which is able to build up a pressure in the wheel brakes independently of the position of the brake pedal. The intake and exhaust valves are electromagnetically operable to control pressure in the wheel brakes.

To detect dynamic driving conditions, there are four speed sensors, one per wheel, one yaw rate meter, one lateral accelerometer and at least one pressure sensor for the brake pressure generated by the brake pedal. In this case, the pressure sensor may also be replaced by a Pedalweg- or pedal force gauge, if the auxiliary pressure source is arranged such that a brake pressure built up by the driver of the auxiliary pressure source is indistinguishable.

In a driving stability control, the driving behavior of a vehicle is influenced in such a way that it becomes more manageable for the driver in critical situations. A critical situation here is an unstable driving condition in which, in extreme cases, the vehicle does not follow the specifications of the driver. The function of the driving stability control therefore consists in giving the vehicle the vehicle behavior desired by the driver within the physical limits in such situations.

While for the brake slip control, the traction control and the electronic brake force distribution primarily the longitudinal slip of the tires on the road is important in the yaw moment control (GMR) other variables, such as the yaw rate and the buoyancy velocity. Tilt controls usually evaluate lateral acceleration or roll sizes ( DE 196 32 943 A1 ).

It would be desirable to regulate unstable driving situations, which are often not mastered by the driver, faster and more comfortable, so that critical driving situations can be better controlled.

The DE 100 24 656 A1 discloses a method for controlling the driving stability of a vehicle, in which based on a plurality of input variables pressures for individual brakes of the vehicle are determined, so that by a braking intervention, the driving stability of the vehicle is increased. It is provided that it is determined in an understeering driving behavior, whether there is a tendency to a subsequent oversteering driving behavior and that in this case a braking intervention already takes place in an understeering driving behavior.

From the DE 100 54 647 A1 a method for controlling the driving stability of a vehicle is known, in which, depending on a plurality of input variables, pressures for individual brakes of the vehicle are determined, so that wheel stability is increased by wheel-specific brake interventions. With a stable driving behavior, it is determined whether there is a tendency for subsequent unstable driving behavior on the basis of highly dynamic articulation. Here, the highly dynamic articulation in dependence on the temporal Course of the steering wheel angular velocity detected. If a subsequent unstable driving behavior is concluded, in this case a brake pre-engagement already takes place with a stable driving behavior. By predicting the critical driving situation unstable driving behavior of the vehicle is either avoided or reduced to a level that it can be controlled by the driver. In addition, with extreme countersteering, the lateral acceleration should be taken into consideration, if there is a tendency to a subsequent unstable driving behavior.

The vehicle dynamics control builds on the brake pre-intervention, as well as a conventional brake intervention in ESP rule case, the brake pressure in at least one meshing wheel as quickly as possible, so that the critical driving situation of the vehicle is immediately changed to a stable driving behavior. As a result, too large a rotation of the vehicle about the vertical axis can be initiated during countersteering during the lane change, which must be corrected with a further brake intervention. It can be caused during cornering with high lateral acceleration by the transverse dynamics rolling movements of the body, with the risk of tilting of the vehicle about the longitudinal axis.

The invention has the object of developing the generic method for controlling the driving stability such that a more comfortable and faster stabilization of the vehicle can be achieved.

According to the invention, this object is achieved in that a generic method for controlling the driving stability of a vehicle is performed so that is determined at an unstable driving behavior with a brake engagement on at least one engagement wheel, whether based on variables that the steering angle speed, the steering angle Lateral acceleration, the yaw rate and / or the reference yaw rate u. Likewise, there is a tendency for a subsequent zero crossing of the yaw rate with a further unstable driving behavior of the vehicle, and that in this case a brake overlay intervention already takes place before the end of the unstable driving behavior, if an analysis of at least the two yaw rate signals, of the yaw rate reference signal obtained with the aid of a yaw rate sensor and of the yaw rate reference signal determined in a vehicle model, results in a matching to a stable drivability and / or a stable drivability adapted to the reference yaw rate profile by the brake overlay intervention.

Advantageously, as a function of the reference yaw rate, an approach to a stable driving behavior and / or a stable driving behavior is achieved when the brake overlay intervention prematurely terminates the brake intervention on the engagement wheel. By prematurely ending the brake engagement, the rate of rotation of the vehicle about the vertical axis generated by the brake engagement can be influenced to either avoid or reduce to a certain extent a tendency for a subsequent unstable driving behavior as it originates from the driver can be mastered. If, nevertheless, a tendency for a subsequent zero crossing of the yaw rate is determined with a further unstable driving behavior of the vehicle, it is expedient that the brake overlay intervention prematurely initiates a brake intervention on another engagement wheel by the brake engagement on the engagement wheel to mitigate caused turning behavior of the vehicle. Furthermore, it is advantageous for the brake overlay engagement to modify the brake engagement on the engagement gear (s) such that the brake pressure in the wheel brakes is degraded, retained, and / or rebuilt in a model-based manner. By means of the method, the braking intervention of the vehicle dynamics control (lane change logic) is advantageously already ended when the course of the measured yaw rate and the course of the yaw rate reference determined in the vehicle model (target specification of the yaw rate ) approach each other within a period of time (multiple loops). For early prediction of an unstable driving behavior, a signal is preferably formed for analyzing or evaluating the yaw rate signals, which represents the difference between the yaw rate reference signal obtained with the aid of a yaw rate sensor and the yaw rate reference signal determined in a vehicle model. It is expedient here if the analysis of the two yaw rate signals is carried out if the two yaw rate signals have the same signs or the same direction. This is considered the right (desired) signal trend. In this case, the steering angle gradient in size and direction can be evaluated in conjunction with the difference signal. It is advantageous that the temporal change of the difference signal is evaluated for terminating, initiating and / or modifying the brake intervention. Alternatively, the temporal change of the two yaw rate signals and their course can be evaluated. Advantageously, they have a similar yaw acceleration.

In a time course of the two yaw rate signals to each other, in which the difference of the yaw rate signals or the difference signal decreases until a limit is reached or fallen below or stops over a predetermined period or a predetermined period of time, the brake engagement on the sprocket finished and / or initiates a brake engagement on another engagement gear and / or modifies the brake engagement on one of the engagement gears.

According to one embodiment, it is further advantageous that at the time when the brake engagement is terminated or mitigated by a brake overlay engagement that relieves or maintains the brake pressure in the wheel brake of the engagement wheel, the brake pressure in the on the same Axle opposite wheel is constructed to counteract the excessive yaw moment of the previous brake engagement.

The brake overlay engagement is preferably done in highly dynamic maneuvers, i. H. for example when changing lanes.

Advantageously, this consideration of the signal trend increases control comfort, reduces the danger of tipping and more comfortably stabilizes the vehicle at the same or earlier point in time without a substantial deviation from the desired lane or lane of the vehicle. The signal trend is analyzed taking into account the steering angular velocity, and / or the yaw rate reference acceleration, assuming that the rotational behavior should decrease as these quantities decrease.

If the difference of the yaw rate signals is reduced as a condition essential to the invention, it is assumed that the rotational behavior of the vehicle about the vertical axis should be reduced. Now, if the yaw rate signal and the yaw rate reference signal have the same sign, depending on the difference of the yaw rate signals, an intervention countering the rotation of the vehicle can be made, which dampens the dynamics of the changeover maneuver and thus overshoots the yaw rate (actual value) Yaw rate reference signal (setpoint) is prevented or largely reduced. This method of rotary damping reduces the number and hardness of the interventions, which improves comfort. Avoiding oversteer situations caused by the ESP Dynamic Driving Controller reduces the danger of tipping over. If this pattern recognition (trend analysis) takes place and it can be concluded that a critically critical excitation has occurred, brake pressure is applied to the wheel brake of the opposite wheel of the same axis. As a result, an increasing rotational damping of the vehicle about the vertical axis is achieved, which reduces the amount of yaw rate to a size below the size of the model-based yaw rate reference.

Advantageous developments of the invention are specified in the subclaims.

An embodiment is shown in the drawing and will be described in more detail below.

Show it

1 evaluated or generated signal sequences of a lane change logic in the prior art

2 In accordance with the invention evaluated or generated signal sequences of a lane change logic

3 a vehicle with the components of a vehicle dynamics control

3 schematically shows a vehicle with a brake control system. The four wheels are with 15 . 16 . 20 . 21 designated. At each of the wheels 15 . 16 . 20 . 21 is ever a wheel sensor 22 to 25 intended. The signals become an ESP driving dynamics controller 28 supplied, which determines based on predetermined criteria from the wheel speeds, the vehicle speed v _Ref . Furthermore, a yaw rate sensor 26 , a lateral acceleration sensor 27 and a steering angle sensor 29 with the regulator 28 connected. Each wheel also has a wheel brake 30 to 33 on. These brakes are hydraulically operated and receive pressurized hydraulic fluid via hydraulic lines 34 to 37 , The brake pressure is via a valve block 38 set, wherein the valve block is driven by electrical signals independent of the driver, in the electronic control 28 be generated. About a operated by a brake pedal master cylinder 39 can be controlled by the driver brake pressure in the hydraulic lines. In the master cylinder and the hydraulic lines pressure sensors are provided by means of which the driver's brake request can be detected.

1 shows the known waveform of the yaw rate sensor 26 measured yaw rate 44 , the reference yaw rate determined in the vehicle dynamics controller in a model 40 , of the steering angle sensor 29 measured steering angle 41 , the difference signal 42 from the yaw rate and the reference yaw rate and the lateral acceleration 43 with a double lane change, which may be desired, for example, if an obstacle suddenly has to be avoided. An ESP controller can detect the unstable driving behavior and correctively intervene, but it can not prevent the emergence of the unstable state.

The in 1 shown signal course in the double lane change is based on a stable driving behavior, ie the vehicle follows the driver's specification without noticeable difference, the slip angle is 0 degrees. The ESP control system is available to control the brake system standing signals 40 - 44 are in this stable driving condition in a rest band. From the stable driving situation, a highly dynamic steering process can take place. The highly dynamic steering process is the course of the steering angle speed 41 to recognize that up to a steering angle maximum 50 increases. Thereafter, a back and counter steering takes place.

Due to the highly dynamic steering operation, a rotation of the vehicle about its vertical axis can be initiated, which can lead to a subsequent unstable driving behavior (driving condition). 1 shows a initiated according to a highly dynamic steering operation brake intervention 60 on the right, outside of the curve 16 , at a left turn. The brake engagement takes place at a time when the steering angle is the Lenwinkelmaximum 50 has already passed and a return takes place. Is this the yaw rate 44 above the reference yaw rate 40 (oversteering drivability) and the difference value resulting from a comparison of the yaw rate with the reference yaw rate is above a limit value calculated in the controller 28 provided control law an additional yaw moment. This additional yaw moment is fed to a distribution logic which generates output variables for controlling the brake pressure values or valve switching times. The brake pressure values are converted directly into the wheel brakes. The brake intervention 70 causes a lowering of the transmittable lateral forces on the curve outer front wheel 16 , It becomes a yaw moment 62 the vehicle opposite direction torque 63 generated in the event of oversteer causes the vehicle turns out of the curve.

As 1 shows is by the brake intervention 70 the yaw rate 44 introduced with a gradient to the reference yaw rate, which causes as immediate as possible reduction of the difference between the yaw rate and the reference yaw rate, wherein there is an overshoot of the yaw rate at time t1. The regulator 28 controls the oversteering driving behavior of the vehicle in the opposite direction with another brake intervention 80 on the opposite wheel arranged on the same axis 15 opposite.

2 shows the inventive waveform. The same reference numerals are used for the same process steps or the same signal transitions, so that the above statements on the 1 Also part of the following description of 2 are. By the scheme 28 the oversteering driving behavior is determined, and in the wheel 16 the brake pressure 70 ( 1 ) adjusted individually according to the additional yawing moment. If the steering angle velocity, and / or the yaw rate reference and / or the difference between the yaw rate and the reference yaw rate is now reduced, it is assumed that the rotational behavior should weaken. Preferably, the difference signal is observed 42 or its derivative from the yaw rate ψ. and the reference yaw rate ψ. _Ref on the basis of the yaw rate sensor 26 and the signals emitted by a model, preferably the one-track model. In accordance with the received signals or the difference signal 42 becomes a brake overlay intervention 75 initiated, the control signals for the valves in the valve block 38 generated. This will increase the brake pressure in the wheel brake 16 at the time t terminates when the difference signal 42 falls below a threshold value D. ?? Like the waveform of the difference signal (Δψ.) 42 in 2 shows, the threshold D depending on the course of the yaw rate 44 calculated using one of the relationships | D | ≈ f | ψ. | or | D | = | ψ. | or | D | = k · | ψ. | during brake overlay intervention 75 must be fulfilled, with f = function, k = correction factor.

Due to the reduced braking torque is adjusted in accordance with the Referenzgierratenverlaufs approximation of the yaw rate 44 reached. The brake overlay intervention 75 remains active as long as the brake pressure applied at time t is maintained in the wheel brake until the analysis of the yaw rate signals indicates that the yaw rate and the reference yaw rate are approaching at the same sign over a given time period. The temporal change of the difference signal 42 or the temporal change of the two yaw rate signals ψ., ψ. _Ref and their course is evaluated to complete the brake overlay intervention. The steering angle velocity and / or yaw rate reference acceleration may be included in the evaluation.

It is terminated as soon as the above condition is no longer met. In this case, the brake pressure 75 dismantled or modified after a function.

It is analyzed whether a time course of the two yaw rate signals to each other, in which the difference of the yaw rate signals decreases, takes place. The comparison and the analysis of the two yaw rate signals is made when the two yaw rate signals have the same sign and the same direction and have a similar yaw acceleration. This is considered a true trend and no further brake interventions are allowed to increase the vehicle's rotation about its vertical axis.

Through the brake overlay intervention 75 , stopping, holding, modifying and building up the brake pressure build-up can prevent further brake interventions or reduce the number of brake interventions.

Unlike the in 2 illustrated measure, in which at time t exclusively the brake pressure reduction on the curve outer front wheel 16 takes place, parallel or delayed offset a brake pressure build-up also on the front wheel 15 take place, with recognized signal trend, if Δψ. = | ψ. - ψ. _Ref | from the time of the brake overlay engagement to a steady functional relationship Δψ. (T / dt) is greater than a threshold or if the gradient of the yaw rate is greater than the gradient of the reference yaw rate. In this case, in the front wheel 15 built up brake pressure prematurely. By constructed in accordance with the signal trend brake pressure in the sprocket 15 an attenuation of the set by the brake overlay intervention rate of rotation of the vehicle is achieved about its vertical axis and avoids an overshoot of the yaw rate on the reference yaw rate.

Claims (13)

A method for controlling the driving stability of a vehicle, characterized in that is determined in an unstable driving behavior with a brake engagement on at least one engagement wheel, whether based on variables, the steering angle speed, the steering angle, the lateral acceleration, the yaw rate and / or the reference yaw rate a tendency to a subsequent zero crossing of the yaw rate with further unstable driving behavior of the vehicle is present, and that in this case, a brake overlay intervention takes place when an analysis of at least the two yaw rate signals, namely obtained by means of a yaw rate sensor and in one Vehicle model determined yaw rate reference signal, shows that adapted to the reference yaw rate course approaching a stable driving behavior and / or a stable driving behavior is achieved by the brake overlay intervention. A method according to claim 1, characterized in that the brake overlay engagement terminates the brake engagement prior to completion of the unstable ride on the engagement wheel or prevents its active execution. A method according to claim 1, characterized in that the brake overlay intervention initiates a brake engagement on another engagement wheel before the end of the unstable driving behavior. A method according to claim 1, characterized in that the brake overlay engagement modifies the brake engagement on the engagement wheel. Method according to one of claims 1 to 4, characterized in that for analyzing the yaw rate signals, a signal is formed which represents the difference between the value obtained by means of a yaw rate sensor and the yaw rate reference signal determined in a vehicle model. Method according to one of claims 1 to 5, characterized in that the temporal change of the difference signal is evaluated for inhibiting, terminating, initiating or modifying the brake intervention. Method according to one of claims 1 to 6, characterized in that the temporal change of the two yaw rate signals and their course is evaluated. A method according to claim 7, characterized in that at a time course of the two yaw rate signals to each other, in which reduces the difference of the yaw rate signals, inhibited the brake engagement on the sprocket and / or terminated and / or a brake engagement with another sprocket initiated and / or the brake engagement is modified on one of the engagement wheels. Method according to one of claims 1 to 8, characterized in that the analysis of the two yaw rate signals is performed when the two yaw rate signals have the same sign and / or the same direction. Method according to one of claims 1 to 9, characterized in that at the time at which the brake engagement is terminated or attenuated by a brake overlay engagement, which degrades or holds the brake pressure in the wheel brake of the engagement wheel, the brake pressure in is built on the opposite axis on the same wheel. Method according to one of claims 1 to 10, characterized in that the brake intervention takes place in highly dynamic maneuvers. Method according to one of claims 1 to 11, characterized in that the steering angle gradient is evaluated in size and direction in conjunction with the difference signal. Method according to one of claims 1 to 12, characterized in that the execution logic of the brake overlay intervention is a component of the torque distribution logic of a system for yaw moment control.

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