DE102007036578B4 - Method and device for more robust skid detection of vehicles - Google Patents

Abstract

Method for determining a skid, the following steps being carried out: a) determining a vehicle standstill based on the rotational behavior of the vehicle wheels, b) initiating an automatic continuation of an operating state by controlling or maintaining a service brake pressure, c) checking the operating state using driving dynamics variables, d) repealing the automatic continuation of the operating state depending on the result of the check ande) initiation of a special regulation for stability or traction control, characterized in that the driving dynamics parameters for determining the vehicle standstill are related to known disturbance variables, redetermined and as a check result of the special regulation for stability or traction control are supplied, with the yaw rate Ψ̇ being used as a driving dynamics variable, and the component Ψ̇Steer of the yaw rate Ψ̇ of the vehicle attributable to a steering movement being estimated and used as a disturbance variable, and the difference Ψ̇ -Ψ̇Steer der special regulation for stability or traction control being supplied as the verification result.

Description

The invention relates to the field of vehicle traction aids and in particular to a method having the features of the preamble of claim 1 and a traction assistant having the features of claim 5.

In a vehicle with a traction aid or a traction assistant, the service brake system is used to hold the vehicle on an inclined roadway during an assisted starting process until a torque sufficient for starting is transmitted from the drive motor to the wheels. The service brake, which generates the braking forces required for standstill, is usually controlled automatically. An electric parking brake device is also used for this purpose if the vehicle is parked for a longer period of time.

The DE 10 2005 015 062 A1 relates to a method for determining a vehicle standstill after braking, in which an automatic continuation of this operating state is carried out to prevent the vehicle from rolling away when starting off. Methods of this type describe a starting aid with which vehicles are to be prevented from rolling back when starting off on a hill via the service brake. If the vehicles slide on the hill when the vehicle is stationary, they can no longer be controlled because the wheels are blocked by the traction help. It is therefore proposed to check the operating state of the vehicle using driving dynamics parameters and/or driving dynamics states and to stop the automatic continuation of the operating state depending on the checking result. A special regulation for stability or traction control is initiated.

From the DE 44 46 823 C1 a device for preventing a vehicle from rolling away is known in which, when the vehicle is properly parked, ie with the parking brake actuated, a braking pressure ensuring the standstill of the vehicle is generated when the parking brake is released. This is intended to ensure that the vehicle does not roll away unintentionally as long as no starting process has been detected or until the parking brake of the vehicle is actuated.

From the WO 92/04213 A1 an arrangement for holding a vehicle on a hill is known, which enables a holding aid, a so-called hillholder function, on an inclined roadway.

The DE 195 25 552 A1 discloses a method for holding a vehicle on a sloping roadway and when starting off on a hill, in which, taking into account the vehicle speed and the brake pedal actuation or corresponding criteria, braking force is applied to one or more vehicle wheels, in particular to the wheels of an axle, ie maintained, increased and is dismantled again. The braking force is adjusted depending on the driving situation of the vehicle.

From the DE 196 25 919 A1 a system for controlling the braking effect in a motor vehicle emerges, in which the vehicle's longitudinal speed is detected and a creep suppression mode or a hillholder mode is activated depending on this vehicle's longitudinal speed, in order to prevent the driver from moving the vehicle away unintentionally.

From the DE 196 21 628 A1 also discloses a method or a device for controlling a brake system of a vehicle, which enables a so-called hillholder function. This hillholder function is put into operation by the driver pressing the brake pedal and a corresponding request signal, for example from a button that can be operated by the driver or from a vehicle standstill detection system, being present.

Facilities with hillholder functions are also from the DE 34 26 669 A1 , the DE 35 07 330 A1 , the EP 0 822 129 A1 and the DE 36 18 532 A1 known.

From the DE 196 11 360 A1 a device for actuating the braking system of a road vehicle is known, in which, in traffic-related standstill phases in which a gear of the transmission remains engaged with the engine running, a road vehicle with an automatic transmission operates the service brake shortly after the vehicle has come to a standstill due to targeted braking activated automatically, allowing the driver to release the brake pedal and holding the vehicle stationary on a level or downhill road. This parking brake operation of the vehicle's service brake system is canceled when the driver actuates the accelerator pedal, the position of which is monitored by a switch. This device also enables starting assistance on hills.

There are a variety of conditions under which launching ( WO 99/20921 A1 , DE 199 50 162 A1 , DE 100 63 061 A1 , DE 198 25 642 A1 ) or the activation of the start-up assistant can or should take place. A start-up assistant solves the problem that occurs when starting on an inclined road, for example on a slope, that the vehicle rolls back a little, when the driver takes his foot off the brake pedal to accelerate a short time later. From the DE 199 50 162 A1 a start-up assistant is known, which is activated manually by the driver via the brake pedal and does not require additional sensors. To activate the start-up assistant, the brake pressure applied by the driver is monitored. The driver has to feed a certain pressure into the service brake over a certain period of time in order to trigger an automatic vehicle standstill on a hill.

With most of the braking devices described above, the traction aids are activated automatically. In addition, it is known to activate the traction help in that the brake pedal and a switch are actuated at the same time.

Other systems use longitudinal acceleration sensors or longitudinal acceleration estimates, by means of which a slope can be determined. Depending on the determined slope and other conditions, such as the brake pressure controlled by the driver, the brake pressure required to keep the vehicle stationary on a hill can be automatically controlled in the wheel brakes of the vehicle.

The traction aids usually use the wheel speed sensors of the ABS system to detect when the vehicle is stationary ( DE 198 25 642 A1 ). There is a risk here that a standstill of the wheels will erroneously be inferred that the entire vehicle is at a standstill, even though the vehicle is slipping with the wheels locked. Such an activation can lead to incorrect activations in the case of low coefficients of friction. Since some functions, such as the "Hill Start Assist" (HSA) should only be activated when the vehicle is stationary, special controller processes monitor in addition to the wheel speed signals whether the vehicle shows signs of slipping. The skid detection becomes active shortly after the wheels are detected to be stationary and is intended to determine whether the vehicle is skidding with locked wheels so that, for example, the affected control process can be switched off immediately.

The skid detection evaluates the yaw rate signal from the ESP controller because vehicles exhibit a slight turning movement when they start to skid. Steering movements also lead to a slight yaw movement of the vehicle and represent a disturbance variable for skid detection from a control point of view. Without suitable measures, it is possible to trigger skid detection via strong steering movements, such as can occur when maneuvering a vehicle.

The invention is therefore based on the object of providing a method and a starting assistant as well as a device which ensures that the activated skid detection was not triggered by additional steering movements caused by the driver.

This object is solved by the features of the independent claims. Advantageous developments are specified in the dependent claims.

1. a) Ermitteln des Fahrzeugstillstands anhand des Drehverhaltens des Fahrzeugs,
2. b) Einleiten der selbsttätigen Fortsetzung des Betriebszustandes durch Einsteuern oder Halten eines Betriebsbremsdruckes,
3. c) Überprüfen des Betriebszustandes mittels Fahrdynamikgrößen,
4. d) Aufheben der selbsttätigen Fortsetzung des Betriebszustandes in Abhängigkeit von dem Überprüfungsergebnis und
5. e) Einleiten einer Sonderregelung zur Stabilitäts- oder Traktionskontrolle

, wobei die Fahrdynamikgrößen zur Ermittlung des Fahrzeugstillstandes gegenüber bekannten Störgrößen in Bezug gesetzt, neu bestimmt und als Überprüfungsergebnis der Sonderregelung zur Stabilitäts- oder Traktionskontrolle zugeführt werden.According to the invention, it is provided that the following steps are carried out to determine a slip event:

1. a) Determination of the vehicle standstill based on the turning behavior of the vehicle,
2. b) Initiating the automatic continuation of the operating state by applying or maintaining a service brake pressure,
3. c) Checking the operating status using driving dynamics parameters,
4. d) cancellation of the automatic continuation of the operating state depending on the check result and
5. e) Initiating a special regulation for stability or traction control

, whereby the driving dynamics variables for determining the vehicle standstill are related to known disturbance variables, re-determined and fed as a check result to the special regulation for stability or traction control.

In a further embodiment of the invention, it is provided that the steering angle and/or its derivatives are evaluated in order to check the operating state of the vehicle.

According to the invention, the yaw rate Ψ̇ is estimated as the driving dynamics variable, the disturbance variable of the component Ψ̇ _Steer of the yaw rate Ψ̇ of the vehicle due to the execution of a steering movement and the difference Ψ̇-Ψ̇ _Steer of the special regulation for stability or traction control as a check result.

1. a) Ermitteln eines Fahrzeugstillstands anhand vom Drehverhalten der Fahrzeugräder,
2. b) Einleiten der selbsttätigen Fortsetzung des Betriebszustandes durch Einsteuern oder Halten eines Betriebsbremsdruckes,
3. c) Überprüfen des Betriebszustandes mittels Fahrdynamikgrößen und/oder Fahrdynamikzuständen,
4. d) Aufheben der selbsttätigen Fortsetzung des Betriebszustandes in Abhängigkeit von dem Überprüfungsergebnis
5. e) Einleiten einer Sonderregelung zur Stabilitäts- oder Traktionskontrolle

und die Fahrdynamikgrößen und/oder Fahrdynamikzustände zur Ermittlung des Fahrzeugstillstandes gegenüber bekannten Störgrößen und/oder Störzuständen in Bezug gesetzt, neu bestimmt und als Überprüfungsergebnis der Sonderregelung zur Stabilitäts- oder Traktionskontrolle zugeführt werden.A particularly advantageous embodiment of the invention is the start-up assistant for supporting the start-up of a vehicle uphill, the steps

1. a) Determination of a vehicle standstill based on the rotational behavior of the vehicle wheels,
2. b) Initiating the automatic continuation of the operating state by applying or maintaining a service brake pressure,
3. c) Checking the operating state using driving dynamics variables and/or driving dynamics states,
4. d) canceling the automatic continuation of the operating state depending on the result of the check
5. e) Initiating a special regulation for stability or traction control

and the driving dynamics variables and/or driving dynamics states for determining the vehicle standstill are related to known disturbance variables and/or disturbance states, redetermined and fed as a check result to the special regulation for stability or traction control.

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

• 1 eine schematische Darstellung der auf ein Fahrzeug wirkenden Kräfte bei einer Fahrzeugbewegung an einer Steigung.
• 2 ein vereinfachtes Blockschaltbild einer Eliminierung einer durch das Lenken bewirkten Störeinwirkung und Weitergabe der korrigierten Gierrate an das Rutscherkennungsmodul

Show it

• 1 a schematic representation of the forces acting on a vehicle during vehicle movement on an incline.
• 2 a simplified block diagram of an elimination of an interference effect caused by the steering and forwarding of the corrected yaw rate to the skid detection module

wird durch die Gewichtskraft bestimmt.The invention is based on the finding that a vehicle (1) that is brought from the driving state to a standstill state on a hill (2) and is equipped with a starting assistant can slide. On an incline, the gradient resistance G _g * sin α _st (3) is counteracted by the longitudinal force F _x that is required to keep the vehicle stationary on the incline. The coefficient of friction required to transmit the longitudinal force $\mu =\frac{f_x}{f_G}$

is determined by the weight.

Vehicle skidding can be triggered or influenced from the operating state of standstill with a low coefficient of friction (e.g. on ice) and/or a steep incline and/or high vehicle weight. An additional influencing factor is the position of the center of gravity (4) and how it changes with the loading of the vehicle. If a grip limit between the tires of the vehicle and the ground is exceeded, the vehicle begins to move downhill.

The invention advantageously makes the slip detection of the ESP controller robust against steering wheel movements when stationary.

(34) mit $${\overrightarrow{k}}_{Steer}=\left(k_{\mathrm{\Theta }},k_{\dot{\Theta }}\right)\text{ zu }{\dot{\Psi }}_{Steer}={\overrightarrow{k}}_{Steer}\cdot \left(\begin{array}{c}\mathrm{\Theta }\\ \dot{\Theta }\end{array}\right).$$

The method consists in estimating the proportion Ψ̇ _Steer (30) of the yaw rate Ψ̇ (31) of the vehicle that is attributable to steering movements and feeding it to the skid detection algorithm as a disturbance variable. This proportion is calculated from the steering angle Θ (32) and its derivative Θ̇ (33) and a factor ${\overrightarrow{k}}_{Stee\mathrm{right}}=\left(k_{\mathrm{\theta }},k_{\dot{\theta }}\right)$

(34) with $${\overrightarrow{k}}_{Stee\mathrm{right}}=\left(k_{\mathrm{\theta }},k_{\dot{\theta }}\right)\text{to}{\dot{\Psi }}_{Stee\mathrm{right}}={\overrightarrow{k}}_{Stee\mathrm{right}}\cdot \left(\begin{array}{c}\mathrm{\theta }\\ \dot{\theta }\end{array}\right).$$

2 shows how the corrected yaw rate Ψ̇ _Corr (34) is obtained by subtracting the steering component: $${\dot{\Psi }}_{CO\mathrm{right}\mathrm{right}}=\dot{\Psi }-{\dot{\Psi }}_{Stee\mathrm{right}}.$$

Only the corrected yaw rate is included in the skid detection, which is now robust to steering movements when stationary.

By adding the steering movement as a disturbance variable, it is possible to make the skid detection insensitive to violent steering movements. As a result, the skid detection can simultaneously be made more sensitive to the yaw rate component that can be attributed to skids.

The decisive factor is that the corresponding proportion of the vehicle's yaw rate, which is due to the steering movement at a standstill, is estimated on the basis of the steering angle and steering angle speed. The skid detection method then uses the yaw rate corrected by this proportion.

Claims (5)

Method for determining a skid, the following steps being carried out: a) determining a vehicle standstill based on the rotational behavior of the vehicle wheels, b) initiating an automatic continuation of an operating state by controlling or maintaining a service brake pressure, c) checking the operating state using driving dynamics variables, d) repealing the automatic continuation of the operating state depending on the result of the check and e) initiation of a special regulation for stability or traction control, characterized in that the driving dynamics parameters for determining the vehicle standstill are related to known disturbance variables, redetermined and as a check result of the special regulation for stability or Traction control are supplied, the yaw rate Ψ̇ ver as a driving dynamics variable is turned, and the part Ψ̇ _Steer of the yaw rate Ψ̇ of the vehicle that can be attributed to a steering movement is estimated and used as a disturbance variable and the difference Ψ̇ -Ψ̇ _Steer of the special regulation for stability or traction control is supplied as the verification result. procedure after claim 1 characterized in that the steering angle and/or its derivatives are evaluated to check the operating state of the vehicle. Procedure according to one of Claims 1 until 2 , characterized in that depending on the result of the check, the brake pressure is reduced. Procedure according to one of Claims 1 until 3 , characterized in that the brake pressure is reduced and built up as a function of the check result. Start-up assistant for supporting the starting of a vehicle uphill, the steps a) determining a vehicle standstill based on the rotational behavior of the vehicle wheels, b) initiating the automatic continuation of the operating state by applying or maintaining a service brake pressure, c) checking the operating state using driving dynamics variables and / or driving dynamics states, d ) Cancellation of the automatic continuation of the operating state depending on the result of the check e) Initiation of a special regulation for stability or traction control. characterized in that the driving dynamics variables for determining the vehicle standstill are related to known disturbance variables, redetermined and fed as a check result to the special regulation for stability or traction control, with the yaw rate Ψ̇ being used as the driving dynamics variable, and the proportion Ψ̇ _steer attributable to a steering movement Yaw rate Ψ̇ of the vehicle is estimated and used as a disturbance variable and the difference Ψ̇ -Ψ̇ _Steer of the special regulation for stability or traction control is supplied as the result of the check.

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