METHOD FOR ASCERTAINING THE INSTANTANEOUS ROADWAY ROUGHNESS IN A VEHICLE

Abstract

A method for ascertaining the instantaneous roadway roughness in a vehicle. In the method, the frequency-dependent amplitude response is determined from the wheel speed, and a roughness characteristic variable is ascertained as a measure of the roadway roughness.

Claims

1-10. (canceled)

11. A method for ascertaining an instantaneous roadway roughness in a vehicle, comprising the following steps: ascertaining a rotational speed of a wheel of the vehicle; and carrying out a frequency analysis of a progression of the rotational speed, including determining a frequency-dependent amplitude response; and ascertaining a statistical roughness characteristic variable characterizing a deviation from a basic curve of the amplitude response, from the amplitude response, as a measure of the roadway roughness.

12. The method as recited in claim 11, wherein an amplitude variance of the amplitude response is ascertained as the roughness characteristic variable.

13. The method as recited in claim 11, wherein the roughness characteristic variable at or adjoining a resonance point of the amplitude response of a tire or the wheel is ascertained.

14. The method as recited in claim 11, wherein a friction coefficient between the tire and the roadway is inferred from the roughness characteristic variable.

15. The method as recited in claim 11, wherein the roughness characteristic variable is related to a tire-typical reference value.

16. The method as recited in claim 11, wherein an air pressure in a tire of the wheel is determined from the progression of the rotational speed.

17. The method as recited in claim 11, wherein a rotational speed sensor, using which the rotational speed of the wheel is ascertained, is assigned to each wheel of the vehicle.

18. A method for activating a vehicle unit influencing vehicle dynamics of a vehicle, comprising the following steps: ascertaining a rotational speed of a wheel of the vehicle; and carrying out a frequency analysis of a progression of the rotational speed, including determining a frequency-dependent amplitude response; ascertaining a statistical roughness characteristic variable characterizing a deviation from a basic curve of the amplitude response, from the amplitude response, as a measure of an instantaneous roadway roughness; and activating the vehicle unit as a function of the roughness characteristic variable.

19. A control unit for activating a vehicle unit influencing vehicle dynamics of a vehicle, the control unit configured to: ascertain a rotational speed of a wheel of the vehicle; and carry out a frequency analysis of a progression of the rotational speed, including determining a frequency-dependent amplitude response; ascertain a statistical roughness characteristic variable characterizing a deviation from a basic curve of the amplitude response, from the amplitude response, as a measure of an instantaneous roadway roughness; and activate the vehicle unit as a function of the roughness characteristic variable.

20. A vehicle, comprising: at least one rotational speed sensor at a vehicle wheel; a vehicle unit configured to influence vehicle dynamics of the vehicle; and a control unit configured to activate the vehicle unit to influence the vehicle dynamics, the control unit configured to: ascertain a rotational speed of the vehicle wheel using the rotational speed sensor; and carry out a frequency analysis of a progression of the rotational speed, including determining a frequency-dependent amplitude response; ascertain a statistical roughness characteristic variable characterizing a deviation from a basic curve of the amplitude response, from the amplitude response, as a measure of an instantaneous roadway roughness; and activate the vehicle unit as a function of the roughness characteristic variable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a vehicle wheel on a rough roadway.

[0019] FIG. 2 shows the frequency-dependent amplitude response of the vehicle wheel.

[0020] FIG. 3 shows a flow chart for ascertaining the instantaneous roadway roughness in the vehicle.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0021] FIG. 1 shows a vehicle wheel 1 including a tire 2 on a rim 3, vehicle wheel 1 being suspended at a wheel suspension 4, which is designed as a spring damper system. Vehicle wheel 1 is driving on a roadway 5 which has a comparatively strongly pronounced roadway roughness. The roughness of roadway 5 results in a vertical excitation of vehicle wheel 1 while driving.

[0022] Vehicle wheel 1 may be mounted at a motor-operated two-wheeler or at a motor vehicle.

[0023] The rotational speed of vehicle wheel 1 is ascertained with the aid of a rotational speed sensor, a frequency-dependent amplitude response shown in FIG. 2 being determinable from the progression of the rotational speed by frequency analysis.

[0024] FIG. 2 shows, as a function of the frequency, a setpoint amplitude response 6 and an actual amplitude response 7, which is shifted with respect to setpoint amplitude response 6 in the direction of lower frequencies. The amplitude responses depend on the utilized tire type. The shift between setpoint amplitude response 6 and actual amplitude response 7 is the result of a pressure loss in tire 2.

[0025] In FIG. 2, a resonance area 8 is identified by a dotted line, within which the resonance points having a maximum of both setpoint amplitude response 6 and of actual amplitude response 7 are situated. In order to ascertain the roughness characteristic variable, the amplitude variance of actual amplitude response 7 in resonance area 8 is ascertained with the aid of the flow chart according to FIG. 3.

[0026] According to the flow chart in FIG. 3, the wheel speed of vehicle wheel 1 is ascertained with the aid of rotational speed sensor 9 and supplied to a control unit 10 in the vehicle as an input variable, in which the sensor data of rotational speed sensor 9 are evaluated. In control unit 10, the frequency-dependent actual amplitude response is ascertained in a first evaluation step 11 from the rotational speed of rotational speed sensor 9. In resonance area 8 of actual amplitude response 7, the amplitude variance is determined, and in particular, for the high-frequency oscillation which is superimposed on the basic curve of actual amplitude response 7. In FIG. 2, this high-frequency oscillation is apparent as irregular vibration superimposed on the basic curve of the amplitude response.

[0027] In a next evaluation step 12, the amplitude variance of actual amplitude response 7 is calculated in resonance area 8 in control unit 10. The amplitude variance represents a roughness characteristic variable, which is related to a tire-typical reference value 14, yielding a standardized roughness characteristic variable which is available at the output of control unit 10 and may be further used in a vehicle unit 13, which has an influence on the vehicle dynamics. Vehicle unit 13 is the braking system, the drive system, the steering system or an active chassis unit, by way of example. The standardized roadway roughness may, in particular, be used with respect to the vehicle safetyor possibly another criterionduring the activation of vehicle unit 13.