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DE-102015223273-B4 - Method for detecting a skidding process of a motor vehicle and control unit

DE102015223273B4DE 102015223273 B4DE102015223273 B4DE 102015223273B4DE-102015223273-B4

Abstract

Method for detecting a skidding process of a motor vehicle, wherein a braking force value (p Ssm ) is set at at least one wheel brake of the motor vehicle by means of a holding assist function to prevent the motor vehicle from rolling away after a stopping maneuver and wherein the slipping process is detected by means of an evaluation of a vehicle dynamics parameter (Ψ̇) characterizing the lateral movement of the motor vehicle, characterized in that, in particular in successive calculation cycles, at least one sum (Σ + , Σ - ) is formed over a plurality of measured values of the vehicle dynamics parameter (Ψ̇), and the sliding process is recognized depending on the value of the sum or the values of the sums.

Inventors

  • David Toth
  • Gabor Nagy

Assignees

  • AUMOVIO GERMANY GMBH

Dates

Publication Date
20260513
Application Date
20151125

Claims (11)

  1. Method for detecting a skidding process of a motor vehicle, wherein a braking force value (p Ssm ) is set at at least one wheel brake of the motor vehicle by means of a holding assist function to prevent the motor vehicle from rolling away after a holding process and wherein the skidding process is detected on the basis of an evaluation of a vehicle dynamics parameter (Ψ̇) characterizing the lateral movement of the motor vehicle, characterized in that, in particular in successive calculation cycles, at least a sum (Σ + , Σ - ) is formed over a plurality of measured values of the vehicle dynamics parameter (Ψ̇), and the skidding process is detected as a function of the value of the sum or of the values of the sums.
  2. Procedure according to Claim 1 , characterized in that the vehicle dynamics parameter (Ψ̇) is the yaw rate of the motor vehicle.
  3. Method according to one of the preceding claims, characterized in that only measured values of the vehicle dynamics parameter (Ψ̇) are included in the sum (Σ + , Σ - ) or sums that were determined within a predetermined past time period, in particular within a predetermined number of previous calculation cycles (N S ).
  4. Method according to one of the preceding claims, characterized in that a first sum (Σ + ) is formed over those measured values of the vehicle dynamics quantity ̇ (Ψ̇) that lie above a first predetermined limit value (ε 1 ), and a second sum (Σ - ) is formed over those measured values of the vehicle dynamics quantity (Ψ̇) that lie below a second predetermined limit value ε 2 .
  5. Procedure according to Claim 4 , characterized in that the difference of the magnitudes of the first and second sums (Σ + , Σ- ) is formed, wherein a driving dynamics value ( Ψ̇SD,calc ) is calculated from the difference, wherein a skidding process is detected if the driving dynamics value ( Ψ̇SD,calc ) is above a predetermined third limit ( Ψ̇Grenz ), or that the first and second sums (Σ + , Σ- ) are added to a total sum, wherein a driving dynamics value ( Ψ̇SD,calc ) is calculated from the magnitude of the total sum, wherein a skidding process is detected if the driving dynamics value ( Ψ̇SD,calc ) is above a predetermined third limit ( Ψ̇Grenz ).
  6. Procedure according to Claim 5 , characterized in that a skidding process is also detected when the vehicle dynamics value (Ψ̇ SD,calc ) is above a fourth limit value (Ψ̇ exit ) and a skidding process was detected in a directly preceding calculation cycle.
  7. Procedure according to Claim 6 , characterized in that a skidding process is also detected when the vehicle dynamics value (Ψ̇ SD,calc ) is below the fourth limit (Ψ̇ exit ), and - a skidding process was detected in a directly preceding calculation cycle and - in one of the preceding calculation cycles, which is less than a second predetermined time interval or a second predetermined number of calculation cycles N a behind, the vehicle dynamics value (Ψ̇ SD,calc ) was above the fourth limit (Ψ̇ exit ).
  8. Procedure according to Claim 7 , characterized in that it is deemed to be recognized that no slipping process is present if the driving dynamics value (Ψ̇ SD,calc ) during the second specified time period or the second specified number of successive calculation cycles (N a ) is below the fourth limit value (Ψ̇ exit ).
  9. Method according to one of the preceding claims, characterized in that the method is only carried out if a standstill of the motor vehicle is detected, in particular on the basis of the wheel speeds, and/or a measured pressure in the master cylinder (p) of the motor vehicle is less than a brake pressure requirement (p Ssm ) determined by the holding assist function.
  10. Method according to one of the preceding claims, characterized in that the braking force value (p Ssm ) is reduced when a slipping process is detected.
  11. Electronic control unit for controlling a braking system of a motor vehicle, which performs a holding assist function to prevent the motor vehicle from rolling away after a stopping operation, by which a braking force value (p Ssm ) is set at at least one wheel brake of the motor vehicle, which performs a detection of a skidding process of the motor vehicle, wherein the skidding process is detected by means of the evaluation of a vehicle dynamics parameter (Ψ̇) characterizing the lateral movement of the motor vehicle, characterized in that, for the detection of the skidding process, in particular in successive calculation cycles, at least a sum (Σ + , Σ - ) is formed over a plurality of measured values of the vehicle dynamics parameter (Ψ̇), and the skidding process is detected depending on the value of the sum or on the values of the sums.

Description

The invention relates to a method for detecting a skidding process of a motor vehicle, wherein a braking force value is set at at least one wheel of the motor vehicle to prevent the motor vehicle from rolling away after a stationary maneuver, and wherein the skidding process is detected by evaluating a vehicle dynamics parameter that characterizes the lateral movement of the motor vehicle. The invention further relates to an electronic control unit for controlling a braking system of a motor vehicle. Hill start assist systems, which support the driver of a motor vehicle when starting on an incline by maintaining the brake pressure required to maintain a standstill until sufficient torque for starting is available from the drive motor, are known from the prior art. In such situations, on surfaces with low friction, the vehicle can slip with locked wheels. This slippage is usually accompanied by a rotational movement of the vehicle due to differing friction coefficients and/or forces at the various wheels. Since such slippage generally increases the risk of an accident, it is a significant advantage to detect it as quickly and reliably as possible in order to deactivate or modify the hill start assist function if necessary and/or to warn the driver. From the DE 103 22 125 A1 A method for detecting skidding and subsequently deactivating a hill start assist function is known. In this method, a characteristic lateral parameter of the vehicle, for example the yaw rate, is evaluated, and skidding is detected when the lateral parameter exceeds a threshold value. From the DE 10 2007 036 578 A1 A method for detecting a skidding process is known in which the yaw rate is also evaluated and a proportion of the yaw rate attributable to steering movements is estimated and included as a disturbance variable in the detection. The DE 10 2005 045 998 A1 Disclosing a method for performing a braking operation to ensure that a motor vehicle comes to a standstill. The vehicle's state of motion and the state of motion of at least one of its wheels are detected, and the braking force is reduced when the vehicle is moving and no wheel rotation is detected. The DE 10 2005 015 062 A1 This concerns a procedure for determining when a vehicle has come to a standstill after braking to prevent rolling. It is proposed to monitor the vehicle's operating state using vehicle dynamics parameters and/or states, and to disable the automatic continuation of the operating state depending on the monitoring result. A special regulation for stability or traction control is introduced. Such methods have the disadvantage of proving to be rather unreliable in practice. For example, a brief exceedance of the threshold value by the yaw rate does not necessarily indicate a dangerous skid. Considering the steering angle can also lead to false detections, as, for instance, rapid steering movements by the driver can cause a discrepancy between the expected and measured yaw rate, resulting in a false positive result for skid detection. It is therefore an object of the invention to provide a method which enables a more robust detection of a skidding process of the motor vehicle. The problem is solved by the method according to claim 1 and by a control unit according to claim 11. Further advantageous embodiments are specified in the dependent claims. The invention is based on the idea that a slipping process is detected by means of one or more sums over a plurality of measured values of a vehicle dynamics parameter. Preferably, the sum or sums are calculated using a plurality of measured values of the vehicle dynamics parameter, recorded at different, successive times. Particularly preferably, these are measured values recorded at different times from the same measuring device (e.g., the same sensor). Advantageously, the yaw rate of the vehicle is used as a vehicle dynamics parameter. If the sliding process is accompanied by a rotational movement, which is usually the case, the yaw rate is not zero. The yaw rate can be used to determine whether the vehicle is undergoing a rotational movement. The yaw rate is preferably measured using a yaw rate sensor. Alternatively, the yaw rate can be calculated using measurements from other sensors, such as lateral acceleration sensors. One advantage of using one or more totals is that short-term fluctuations in the measured values, triggered for example by measurement errors or short-term processes that do not pose a hazard, have only a minor influence on the total and thus on the detection of the slipping process. In a preferred embodiment, only measured values of the vehicle dynamics parameter that were determined within a predetermined elapsed time period are included in the sum or sums. Particularly preferably, the predetermined elapsed time period corresponds to a predetermined number of previous calculation cycles of the algorithm. A calculation cycle is understood to be a cycle of the algorithm in which measured values