Device and method for checking a wheel of a rail vehicle for flat spots

Abstract

A device for checking a wheel of a rail car for flat spots. The device includes a microelectromechanical microphone for acquiring measured air-borne sound values within a first time span. In addition, the device includes a processing unit, which is configured to determine, as a function of the measured air-borne sound values acquired, if the wheel has a flat spot. The essence of the present invention is that the device includes an acoustic waveguide. In addition, the device takes the form of a mobile device and may be situated on or in the rail car in such a manner, that air-borne sound, which is radiated at a boundary surface, as air-borne sound, by structure-borne sound propagating through the rail car, is transmitted to the microphone by the acoustic waveguide. Also described is a related method for checking a wheel of a rail car for flat spots.

1 - 13 . (canceled) 
     
     
         14 . A device for checking a wheel of a rail car for flat spots, comprising:
 a microelectromechanical microphone for acquiring measured air-borne sound values within a first time span;   a processing unit to determine, as a function of the measured air-borne sound values acquired, if the wheel has a flat spot; and   an acoustic waveguide;   wherein the device is in the form of a mobile device and is situatable on or in the rail car so that air-borne sound, which is emitted at a boundary surface, as air-borne sound, by structure-borne sound propagating through the rail car, is transmittable to the microphone by the acoustic waveguide.   
     
     
         15 . The device of  claim 14 , further comprising:
 a storage unit;   wherein in response to the determination of a flat spot, the processing unit is configured to generate a signal, which represents a detected flat spot, and to store this signal in the storage unit.   
     
     
         16 . The device of  claim 14 , further comprising:
 a wireless communications unit;   wherein in response to the determination of a flat spot, the processing unit is configured to generate a signal, which represents a detected flat spot, and to transmit this signal with the wireless communications unit.   
     
     
         17 . The device of  claim 14 , wherein the processing unit is configured to ascertain an evaluation signal, by low-pass filtering and high-pass filtering the measured air-borne sound values acquired and subsequently differentiating the filtered, measured values with respect to time, squaring them and averaging them. 
     
     
         18 . The device of  claim 17 , wherein the processing unit is configured to check if the evaluation signal has at least one peak occurring periodically; in the case of a plurality of periodic peaks, the largest peak occurring periodically being selected, and all of the other peaks, which occur within a second time span after or prior to the largest periodic peak, being ignored; and wherein the processing unit is configured to check if a derivative of the evaluation signal with respect to time has both a negative and a positive slope in the region of the periodic peak, and in this case, to check if the periodic peak is greater than a threshold value; and wherein in this case, the processing unit is configured to determine that the wheel has a flat spot. 
     
     
         19 . The device of  claim 14 , further comprising:
 a motion sensor, wherein the device is configured to be woken up from a dormant state by an interrupt signal of the motion sensor.   
     
     
         20 . A method for checking a wheel of a rail car for flat spots, including the method steps:
 (a) acquiring measured air-borne sound values within a first time span, using a microelectromechanical microphone;   (b) ascertaining an evaluation signal from the measured structure-borne sound values acquired, using a processing unit;   (c) determining if the wheel has a flat spot, as a function of the evaluation signal, using the processing unit;   (d) generating a signal, which represents a detected flat spot, using the processing unit, if a flat spot has been determined.   
     
     
         21 . The method of  claim 20 , further comprising:
 (e) storing the signal generated in a storage unit.   
     
     
         22 . The method of  claim 20 , further comprising:
 (e) transmitting the signal generated with a communications unit.   
     
     
         23 . The method of  claim 20 , further comprising:
 (g) acquiring an interrupt signal of a motion sensor, prior to performing (a).   
     
     
         24 . The method of  claim 20 , wherein in (b), the measured structure-borne sound values acquired are low-pass filtered and high-pass filtered, and subsequently, the filtered, measured values are differentiated with respect to time, squared, and averaged, in order to ascertain the evaluation signal. 
     
     
         25 . The method of  claim 20 , wherein in (c), it is checked if the evaluation signal has at least one peak occurring periodically; in the case of a plurality of periodic peaks, the largest peak occurring periodically being selected, and all of the other peaks, which occur within a second time span after or prior to the largest periodic peak, being ignored; if a periodic peak is selected, it is subsequently checked if a derivative of the evaluation signal with respect to time has both a negative and a positive slope in the region of the periodic peak; if this is the case, it is checked if the periodic peak is greater than a threshold value; and if this is so, it is then determined that the wheel has a flat spot. 
     
     
         26 . The method of  claim 25 , wherein when the periodic peak is less than or equal to the threshold value, the threshold value is reduced, and subsequently, the method is continued at (a). 
     
     
         27 . The method of  claim 20 , further comprising:
 (e) transmitting the signal generated wirelessly with a communications unit.   
     
     
         28 . The device of  claim 14 , further comprising:
 a motion sensor, which includes an acceleration sensor or a gyroscope;   wherein the device is configured to be woken up from a dormant state by an interrupt signal of the motion sensor.