METHOD FOR DETECTING BRAKE WEAR IN A VEHICLE

Abstract

A method for detecting brake wear in a vehicle includes ascertaining a condition variable and generating a warning signal if multiple brake judder events are detected from the profile of the condition variable.

Claims

1. A method for detecting brake wear in a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; based on a profile of the at least one of the driving condition variable and the braking condition variable, detecting that a number of occurrences of brake judder events exceeds a first predefined threshold; and in response to the detection of the number exceeding the predefined threshold, generating a warning signal indicating increased brake wear.

2. The method of claim 1, wherein the at least one variable includes a wheel speed signal.

3. The method of claim 1, wherein the at least one variable includes a brake pressure signal of a hydraulic vehicle brake in the vehicle.

4. The method of claim 1, wherein: the detection of at least one of the occurrences of the brake judder events is by detecting a superimposition on the at least one variable of a signal, a frequency (f) of which is one or two times v/(2 r); v is the vehicle speed; and r is a dynamic rolling radius of the tire.

5. The method of claim 1, wherein the detection of at least one of the occurrences of the brake judder events is by detecting a superimposition on the at least one variable of a signal that has an amplitude that exceeds a second predefined threshold.

6. The method of claim 1, wherein, at most, only one brake judder event is counted per braking operation.

7. The method of claim 1, further comprising executing a semi-automatic or fully-automatic braking operation based on the brake judder events.

8. A method for carrying out a fully automatic or semi-automatic braking operation of a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; producing a smoothed signal by subjecting the at least one of the driving condition variable and the braking condition variable to a filtering or a compensation for occurrences of brake judder events identified by superimpositions on a profile of the at least one of the driving condition variable and the braking condition variable; and performing the braking operation based on the smoothed signal.

9. A control unit comprising a processor, wherein the processor is configured to perform a method for detecting brake wear in a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; based on a profile of the at least one of the driving condition variable and the braking condition variable, detecting that a number of occurrences of brake judder events exceeds a first predefined threshold; and in response to the detection of the number exceeding the predefined threshold, generating a warning signal indicating increased brake wear.

10. A control unit comprising a processor, wherein the processor is configured to perform a method for carrying out a fully automatic or semi-automatic braking operation of a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; producing a smoothed signal by subjecting the at least one of the driving condition variable and the braking condition variable to a filtering or a compensation for occurrences of brake judder events identified by superimpositions on a profile of the at least one of the driving condition variable and the braking condition variable; and performing the braking operation based on the smoothed signal.

11. A vehicle comprising: a brake actuator; and a control unit that includes a processor, wherein the processor is configured to perform a method for carrying out a fully automatic or semi-automatic braking operation of a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; producing a smoothed signal by subjecting the at least one of the driving condition variable and the braking condition variable to a filtering or a compensation for occurrences of brake judder events identified by superimpositions on a profile of the at least one of the driving condition variable and the braking condition variable; and controlling the brake actuator to perform the braking operation based on the smoothed signal.

12. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor and that, when executed, causes the processor to perform a method for detecting brake wear in a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; based on a profile of the at least one of the driving condition variable and the braking condition variable, detecting that a number of occurrences of brake judder events exceeds a first predefined threshold; and in response to the detection of the number exceeding the predefined threshold, generating a warning signal indicating increased brake wear.

13. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor and that, when executed, causes the processor to perform a method for carrying out a fully automatic or semi-automatic braking operation of a vehicle, the method comprising: ascertaining at least one of a driving condition variable and a braking condition variable; producing a result by subjecting the at least one of the driving condition variable and the braking condition variable to a filtering or a compensation for occurrences of brake judder events identified by superimpositions on a profile of the at least one of the driving condition variable and the braking condition variable; and performing the braking operation based on the result.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0023] The FIGURE is a flowchart that illustrates a method for detecting brake wear due to repeated brake judder, according to an example embodiment of the present invention.

DETAILED DESCRIPTION

[0024] The flowchart illustrates a method sequence for detecting brake wear in a vehicle for the case that brake judder repeatedly occurs in the vehicle brake that is designed as a hydraulic brake. In a first block 1, which contains the detection logic for establishing brake judder, brake pressure p.sub.B of the hydraulic vehicle brake as well as at least one wheel speed w are supplied as input signals. A brake judder event can be detected from the profile of brake pressure signal p.sub.B if a vibration is superimposed on the basic profile of the brake pressure signal, the frequency of which lies within a defined frequency range and the amplitude of which exceeds an amplitude limiting value. Such brake judder usually occurs either as hot judder, which is characterized by a local material deformation due to heat input in the brake disk, or as cold judder which is induced due to thickness differences in the brake disk or an oblique installation of the brake disk. The frequency typical for hot judder is in the magnitude of f=v/(2 r), where v is the vehicle speed and r is the dynamic rolling radius of the tire. In the case of cold judder, the frequency that results is twice as great as the above-described frequency. The frequencies are mean values, a hot judder or a cold judder being present when the frequency of the superimposed vibration moves within a frequency range about the mean frequency.

[0025] The brake judder is preferably ascertained on the basis of brake pressure signal p.sub.B, where hot judder or cold judder can be differentiated on the basis of wheel speed signal w.

[0026] Alternatively, it is also possible to directly infer a brake judder event on the basis of the profile of wheel speed signal w.

[0027] If it is established in the logic in block 1, that a brake judder has occurred during a braking operation, a braking judder counter is incremented by the value 1 in next block 2. According to an example embodiment, the value of the counter is incremented by the value 1 only once per braking operation, regardless of the duration of the brake judder and regardless of whether brake judder occurs one time or multiple times during an on-going braking operation.

[0028] The brake judder counter of block 3 is used for a prompt to the driver to visit a repair shop. This takes place for the case, in particular, in which the brake judder counter exceeds a limiting value. Additionally or alternatively, it is also possible, according to block 4, to store the brake judder counter internally, for example, in a control unit and to make it available during the next visit to the repair shop, whereupon measures for eliminating the brake judder, for example, on the brake disks of the vehicle, can be carried out, if necessary.

[0029] The brake judder counter represented in block 3 and stored in block 4, represents a warning signal or can result in the output of a warning signal if the number of the detected brake judder events in the brake judder counter exceeds a limiting value.