DE10325486A1 - Regulating vehicle driving stability involves determining tendency towards subsequent crossing of yaw rate null under unstable behavior conditions with braking intervention using various parameters - Google Patents

Abstract

The method involves determining if there is a tendency towards a subsequent crossing of the yaw rate null, with further unstable behavior, under unstable behavior conditions with braking intervention using steering angle rate, steering angle (41), transverse acceleration (43), yaw rate (44) and/or reference yaw rate (40), etc. parameters. If so a braking intervention (70) is applied if analysis shows this will stabilize the vehicle.

Description

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

Violent steering and counter steering actions at e.g. Evasive maneuvers, Changing lanes, freestyle u. Like. Can with a high coefficient of friction vehicle instabilities to lead. For vehicles with a high center of gravity, there is increasing Risk of tipping over.

To counteract these vehicle instabilities automatically a variety of driving stability regulations have become known. Under the term driving stability control unite five Principles for influencing the driving behavior of a vehicle by means of presettable pressures or braking forces in or on individual wheel brakes and by intervening in engine management of the drive motor. This is brake slip control (ABS) which during braking should prevent individual wheels from locking in order to control traction control (ASR), which prevents the driven wheels from spinning, electronic braking force distribution (EBV), which determines the ratio of the braking forces regulates between the front and rear axles of the vehicle by a tilt control (ARB), which prevents the vehicle from tipping over its longitudinal axis, and around a yaw moment control (ESP), which ensures stable driving conditions during Yaws the vehicle around the vertical axis.

So with vehicle is in this context a motor vehicle with four wheels meant, which with a hydraulic, electro-hydraulic or an electro-mechanical brake system. In the hydraulic Brake system can be activated by the driver using a pedal-operated master cylinder a brake pressure can be built up while the electro-hydraulic and electro-mechanical brake systems from the sensed driver braking request dependent Build up braking power. Below is a hydraulic brake system referred. Each wheel has a brake, which one Inlet valve and an outlet valve are assigned. About the Intake valves connect the wheel brakes to the master cylinder, while the outlet valves to a pressureless container or low-pressure accumulator to lead. Finally is there is also an auxiliary pressure source, which is also independent of the position of the brake pedal to build up pressure in the wheel brakes can. The inlet and outlet valves are in for pressure control the wheel brakes can be actuated electromagnetically.

For the detection of driving dynamics states are four speed sensors, one for each wheel, a yaw rate sensor, a lateral accelerometer and reduces a pressure sensor for the from Brake pedal generated brake pressure available. The pressure sensor can also be replaced by a pedal travel or pedal dynamometer if the auxiliary pressure source is arranged such that the driver built up brake pressure indistinguishable from that of the auxiliary pressure source is.

With a driving stability control the driving behavior of a vehicle is influenced in such a way that it for the driver becomes more manageable in critical situations. A critical situation here is an unstable driving condition in which in extreme cases, the vehicle does not follow the driver's instructions. The function of driving stability control So it is within the physical limits in such Situations to the vehicle the vehicle behavior desired by the driver to lend.

While the longitudinal slip of the tires on the road is of primary importance for the brake slip control, the traction control and the electronic brake force distribution, further variables flow into the yaw moment control (GMR), for example the yaw angular velocity and the floating angular velocity. Tilt controls usually evaluate lateral acceleration or roll sizes ( DE 196 32 943 A1 ).

It would be desirable to be able to regulate unstable driving situations that are often not mastered by the driver faster and more comfortably, so that critical driving situations can be better mastered DE 100 54 647 A method for regulating the driving stability of a vehicle is known, in which pressures for individual brakes of the vehicle are determined as a function of a plurality of input variables, so that the driving stability is increased by wheel-specific brake interventions. In the case of stable driving behavior, it is determined whether there is a tendency towards subsequent unstable driving behavior based on highly dynamic steering. If a subsequent unstable driving behavior is inferred, then in this case a brake pre-intervention takes place when the driving behavior is stable. By predicting the critical driving situation, an unstable driving behavior of the vehicle should either be avoided or reduced to a level that the driver can control. In addition, in the case of extreme countersteering, the lateral acceleration should also be taken into account whether there is a tendency towards subsequent unstable driving behavior.

The driving dynamics controller builds up the brake pressure in at least one engagement wheel as quickly as possible during the pre-intervention of the brakes, just as with a conventional brake intervention in the ESP rule, so that the critical driving situation of the vehicle is immediately changed to a stable driving behavior. As a result, an excessive rotation of the vehicle about the vertical axis can be initiated when counter-steering during the lane change, which must be corrected with a further brake intervention. You can During cornering with high lateral acceleration, the lateral dynamics cause the body to roll, with the risk of the vehicle tipping over the longitudinal axis.

The invention is based on the object the generic method to regulate driving stability to further develop such that a more comfortable and faster stabilization of the vehicle can be reached.

According to the invention, this object solved that a generic method to regulate driving stability of a vehicle will that with an unstable driving behavior with a brake intervention is determined on at least one meshing wheel, whether on the basis of quantities that the steering angle speed, the steering angle, the lateral acceleration, the yaw rate and / or the reference yaw rate and the like. play one Tendency to a subsequent zero crossing of the yaw rate with a there is further unstable driving behavior of the vehicle, and that in this case there is a brake overlay intervention, if an analysis of at least the two yaw rate signals, namely the obtained with the help of a yaw rate sensor and that in a vehicle model determined yaw rate reference signal, results from the brake superposition intervention one in accordance Approach of stable driving behavior adapted to the course of the reference yaw rate and / or stable driving behavior is achieved. Preferably the brake overlay intervention already takes place before the end of the unstable driving behavior.

It becomes advantageous depending from the reference yaw rate an approximation to a stable driving behavior and / or a stable driving behavior is achieved when the brake overlay intervention the brake intervention terminated prematurely on the gear wheel or its active execution prevented. The premature termination of the brake intervention can by the brake intervention generated rotation rate of the vehicle around the vertical axis affected that have a tendency to subsequent unstable driving behavior either avoided or reduced to a measure as soon as it arises is that the driver can control it. Will still be one Tendency to a subsequent zero crossing of the yaw rate with a determined further unstable driving behavior of the vehicle, it is expedient that the brake overlay intervention initiates a brake intervention prematurely on another gear wheel, around the turning behavior caused by the brake intervention on the meshing wheel weaken the vehicle. Furthermore, it is advantageous if the brake superposition intervention is the brake intervention modified on the engagement wheel or wheels so that the Brake pressure in the wheel brakes according to a model-based course dismantled, held and / or rebuilt. Through the process becomes the brake intervention of the driving dynamics control (lane change logic) is already advantageous ended when in a maneuver recognized as dynamic, at with a countersteering movement, 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) within a period (several Loops), For early Prediction of unstable driving behavior is preferred a signal is formed for analyzing or evaluating the yaw rate signals, that's the difference between that using a yaw rate sensor obtained and the yaw rate reference signal determined in a vehicle model reproduces. It is useful if the analysis of the two yaw rate signals is performed when the two yaw rate signals have the same sign or the same direction. this will considered the right (desired) signal trend. The Steering angle gradient in size and direction can be evaluated in conjunction with the difference signal. Advantageous is that the temporal change the difference signal to prevent and / or terminate, initiate and / or modifying the brake intervention is evaluated. alternative can change over time of the two yaw rate signals and their course are evaluated. They advantageously have a similar one Acceleration of yaw.

With 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 is reduced until a limit value is reached or is below or over a predetermined period or a predetermined period of time, the brake intervention prevented and / or terminated on the engagement wheel and / or a brake intervention initiated on another meshing wheel and / or the brake engagement on one of the meshing wheels modified.

According to one embodiment, it is still advantageous that at the time when the brake intervention through a brake overlay intervention ended or weakened that reduces the brake pressure in the wheel brake of the meshing wheel or holds, the brake pressure in the opposite on the same axis Wheel is built up to the large yaw moment of the previous one Counteracting brake intervention.

The brake overlay intervention takes place preferably in highly dynamic maneuvers, i.e. For example Lane changes.

This consideration is advantageous of the signal trend increases the control comfort, reduces the risk of tipping and the vehicle is more comfortable at the same time or earlier stabilized without a significant deviation from the desired Track or path of the vehicle takes place. The signal trend is including the steering angular velocity, and / or the yaw rate reference acceleration analyzed, assuming that the turning behavior should weaken, when these sizes decrease.

If the difference between the yaw rate signals is reduced as a condition essential to the invention, is indicated take that the turning behavior of the vehicle around the vertical axis should weaken. If the yaw rate signal and the yaw rate reference signal now have the same sign, depending on the difference in the yaw rate signals, an intervention counteracting the rotation of the vehicle can be undertaken, which dampens the dynamics of the change maneuver and thus overshoots the yaw rate (actual value) over the Yaw rate reference signal (target value) prevented or largely reduced. This method of torsional damping reduces the number and hardness of the interventions, which improves comfort. The avoidance of oversteer situations caused by the ESP vehicle dynamics controller reduces the risk of tipping over. If this pattern recognition (trend observation) takes place and a tilt-critical excitation can be concluded, brake pressure is applied to the wheel brake of the opposite wheel of the same axis. As a result, increasing rotational damping of the vehicle about the vertical axis is achieved, which reduces the amount of the yaw rate to a size below the size of the model-based yaw rate reference.

The execution logic of the brake superposition intervention is advantageously a component of the ESP torque distribution logic. The ESP torque distribution logic is in the DE 195 15 048 A1 described, the content of which is part of the present invention. The inclusion in the ESP distribution logic, ie the modification of the ESP distribution logic in accordance with the method for carrying out the brake superimposition interventions, represents a particularly advantageous embodiment. Of course, the method for carrying out the brake superimposition interventions can also be carried out in a separate supplementary block be trained as a module.

Advantageous further developments of Invention are in the subclaims specified.

An embodiment is in the drawing shown 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 Signal sequences of a lane change logic evaluated or generated according to the invention

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 labeled 15, 16, 20, 21. On each of the wheels 15 . 16 . 20 . 21 is a wheel sensor 22 to 25 intended. The signals are sent to an ESP vehicle dynamics controller 28 supplied, which determines the vehicle speed V _Ref from the wheel speeds based on predetermined criteria. There is also a yaw rate sensor 26 , a lateral acceleration sensor 27 and a steering angle sensor 29 with the controller 28 connected. Each wheel also has a wheel brake 30 to 33 on. These brakes are hydraulically operated and receive hydraulic fluid under pressure via hydraulic lines 34 to 37 , The brake pressure is via a valve block 38 set, the valve block being controlled by electrical signals independent of the driver, which is in the electronic control 28 be generated. Via a master cylinder operated by a brake pedal 39 can be controlled by the driver brake pressure in the hydraulic lines. Pressure sensors are provided in the master cylinder or the hydraulic lines, by means of which the driver's braking 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 from 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 in the case of a double lane change, which may be desired, for example, if an obstacle must suddenly be avoided. An ESP controller can detect the unstable driving behavior and intervene to correct it, but it cannot prevent the unstable condition from occurring.

The in 1 The signal curve shown for a double lane change assumes stable driving behavior, ie the vehicle follows the driver's specifications without a noticeable difference, the float angle is 0 degrees. The signals available to the ESP control system to control the brake system 40-44 are in a rest band in this stable driving condition. A highly dynamic steering process can take place from the stable driving situation. The highly dynamic steering process is based on the course of the steering angular velocity 41 to recognize that up to a maximum steering angle 50 increases. Then there is a reverse and counter steering.

The highly dynamic steering process can initiate a rotation of the vehicle about its vertical axis, which can lead to a subsequent unstable driving behavior (driving state). 1 shows a brake intervention initiated in accordance with a highly dynamic steering process 60 on the right front wheel on the outside of the curve 1b , on a left turn. The braking intervention takes place at a time when the steering angle is the maximum steering angle 50 has already exceeded and there is a return steering. Here lies the yaw rate 44 above the reference yaw rate 40 (overriding driving behavior) and the difference value resulting from a comparison of the yaw rate with the reference yaw rate is above a limit value, is calculated in the controller 28 provided law an additional yaw moment. This additional yaw moment is fed to a distribution logic, the output variables for controlling the brake pressure values or valve switching times generated. The brake pressure values are implemented directly in the wheel brakes. The brake intervention 70 causes a reduction in the transferable side forces on the front wheel on the outside of the curve 16 ,

It becomes a yaw moment 62 opposite torque of the vehicle 63 generated, which in the event of oversteer causes the vehicle to turn out of the curve.

How 1 shows is by the brake intervention 70 the yaw rate 44 brought up to the reference yaw rate with a gradient, which causes the difference between the yaw rate and the reference yaw rate to be reduced as quickly as possible, the yaw rate overshooting 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.

beim Bremsen-Überlagerungs-Eingriff 75 erfüllt sein muss, mit f = Funktion, k = Korrekturfaktor. 2 shows the signal curve according to the invention. The same reference numerals are used for the same method steps or the same signal paths, so that the above explanations for 1 also part of the following description of the 2 are. By the scheme 28 the oversteering driving behavior is determined, and in the wheel 16 the brake pressure 70 ( 1 ) individually adjusted according to the additional yaw moment. If the steering angle speed is reduced, and / or the yaw rate reference or acceleration and / or the difference between yaw rate and reference yaw rate, it is assumed that the turning behavior should weaken. The difference signal is preferably observed 42 or its derivation from the yaw rate and the reference yaw rate _Ref on the basis of that from the yaw rate sensor 26 and the signals emitted by a model, preferably the single-track model. According to 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 build up the brake pressure in the wheel brake 16 ended at time t when the difference signal 42 falls below a threshold value D. How the waveform of the difference signal (Δ) 42 in 2 shows, the threshold value D is dependent on the course of the yaw rate 44 calculated using one of the relationships

during the brake superposition intervention 75 must be fulfilled, with f = function, k = correction factor.

Due to the reduced braking torque, an approximation of the yaw rate is adjusted in accordance with the reference yaw rate curve 44 reached. The brake overlay intervention 75 remains active until the brake pressure entered at time t is kept at the pressure value in the wheel brake until the analysis of the yaw rate signals shows that the yaw rate and the reference yaw rate approach the same sign over a predetermined period of time. The change in time of the difference signal 42 or the temporal change in the two yaw rate signals, _Ref and their course is evaluated to end the brake superimposition intervention. The steering angle speed and / or yaw rate reference acceleration can be included in the evaluation.

It ends as soon as the above condition is no longer met. The brake pressure 75 dismantled or modified after a function.

It is analyzed whether a temporal Course of the two yaw rate signals to each other, in which the Difference in the yaw rate signals is reduced. The comparison and the analysis of the two yaw rate signals is done if the two yaw rate signals have the same sign or the same Direction and a similar Have yaw acceleration, this is considered the right trend and no further brake interventions allowed the rotation reinforce the vehicle about its vertical axis.

Through the brake overlay intervention 75 , with the steps of canceling, maintaining, modifying and building up brake pressure, further brake interventions can be prevented or the number of brake interventions reduced.

ab der Zeit des Bremsen-Überlagerungs-Eingriffs nach einem stetigen funktionalen Zusammenhang Δ (t/dt) größer einem Schwellenwert ist oder wenn der Gradient der Gierrate größer ist als der Gradient der Referenzgierrate. In diesem Fall wird in dem Vorderrad 15 vorzeitig Bremsdruck aufgebaut. Durch den nach Maßgabe des Signaltrends aufgebauten Bremsdruck in dem Eingriffsrad 15 wird eine Abschwächung der durch den Bremsen-Überlagerungs-Eingriff eingestellten Drehrate des Fahrzeugs um seine Hochachse erzielt und ein Überschwingen der Gierrate über die Referenzgierrate vermieden.Unlike the one in 2 Measure shown, in which at the time t only the brake pressure reduction on the front wheel on the outside of the curve 16 takes place, a brake pressure build-up on the front wheel can also occur in parallel or with a time delay 15 if the signal trend is detected, if

from the time of the brake superimposition intervention after a continuous functional relationship Δ (t / dt) is greater than a threshold value or if the gradient of the yaw rate is greater than the gradient of the reference yaw rate. In this case, the front wheel 15 brake pressure built up prematurely. Due to the brake pressure built up in accordance with the signal trend in the meshing wheel 15 a weakening of the rotational rate of the vehicle about its vertical axis set by the brake superimposition intervention and an overshoot of the yaw rate over the reference yaw rate are avoided.

Claims (13)

Method for regulating the driving stability of a vehicle, characterized in that, in the case of unstable driving behavior with a brake intervention on at least one pressure wheel, it is determined whether on the basis of quantities which determine the steering angle speed, the steering angle, the lateral acceleration, the yaw rate and / or the reference yaw rate etc.. reproduce, there is a tendency to a subsequent zero crossing of the yaw rate with further unstable driving behavior of the vehicle, and that in this case a brake superposition intervention takes place if an analysis of at least the two yaw rate signals, namely that obtained with the aid of a yaw rate sensor and one in one Vehicle model determined yaw rate reference signal, shows that the brake superimposition intervention achieves an approximation to a stable driving behavior and / or a stable driving behavior in accordance with the reference yaw rate curve. A method according to claim 1, characterized in that the Brake overlay intervention the brake intervention terminated prematurely on the gear wheel or its active execution prevented. A method according to claim 1, characterized in that the Brake overlay intervention initiates a brake intervention prematurely on another gear wheel. A method according to claim 1, characterized in that the Brake overlay intervention modified the brake engagement on the mesh wheel. Method according to one of claims 1 to 4, characterized in that that a signal is formed to analyze the yaw rate signals, that's the difference between that using a yaw rate sensor obtained and the yaw rate reference signal determined in a vehicle model reproduces. Method according to one of claims 1 to 5, characterized in that that the temporal change the difference signal to prevent, terminate, initiate or modify of the brake intervention is evaluated. Method according to one of claims 1 to 6, characterized in that 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 one another, at which the difference in the yaw rate signals decreases, the Braking - intervention prevented and / or terminated on the engagement wheel and / or a brake intervention initiated on another meshing wheel and / or the brake engagement on one of the meshing wheels is modified. Method according to one of claims 1 to 8, characterized in that that the analysis of the two yaw rate signals is carried out if the two yaw rate signals have the same sign or the have the same direction. Method according to one of claims 1 to 9, characterized in that that at the time when the brake engagement is through a brake overlay engagement ended or weakened that reduces the brake pressure in the wheel brake of the meshing wheel or holds, the brake pressure in the opposite on the same axis Wheel is built. Method according to one of claims 1 to 10, characterized in that that the brake intervention takes place during highly dynamic maneuvers. Method according to one of claims 1 to 11, characterized in that that the steering angle gradient is related in size and direction is evaluated with the difference signal. Method according to one of claims 1 to 12, characterized in that that the execution logic of the Brake overlay procedure a component of the ESP torque distribution logic is.