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.

Claims

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows an exemplary embodiment of a device of the present invention for checking a wheel of a rail car for flat spots.

[0022] FIG. 2 shows an exemplary embodiment of a method of the present invention for checking a wheel of a rail car for flat spots.

[0023] FIG. 3 shows a curve of a measured air-borne sound value versus time and the corresponding, ascertained evaluation signal from this measured air-borne sound value characteristic.

DETAILED DESCRIPTION

[0024] FIG. 1 shows an exemplary embodiment of a device 10 of the present invention for checking a wheel of a rail car 15 for flat spots. Device 10, which includes a microelectromechanical microphone 20 for acquiring measured air-borne sound values 22, is shown. This microphone 20 may be, for example, a piezoelectric microphone or a capacitor microphone. In this connection, attention must be paid to whether microphone 20 has an analog or digital signal output. In the case of an analog microphone, for example, appropriate signal amplification and resistance adjustment may become necessary, and in the case of a digital microphone, interface adaptation may become necessary. Device 10 may be mounted to rail car 15 in such a manner, that a structure-borne sound, which propagates through rail car 15 and is generated, in particular, by the wheels of rail car 15 during the trip, is converted to air-borne sound and this is supplied to microphone 20 via an acoustic waveguide 40. Acoustic waveguide 40 may be, for example, a hollow conductor. Acoustic waveguide 40 transmits the air-borne sound, which is radiated by the structure-borne sound propagating through rail car 15, in the form of air-borne sound, at a boundary surface 16 of rail car 15, from this boundary surface 16 to microphone 20. Boundary surface 16 may be, for example, an outer or inner wall of rail car 15. For example, the hollow conductor may also take the form of a simple opening in a housing of device 10; microphone 20 directly bordering on the opening from one side, and rail car 15 directly bordering on the opening from the other side. In addition, device 10 includes a processing unit 30. For example, processing unit 30 may take the form of a microcontroller.

[0025] Processing unit 30 is connected to microphone 20 in such a manner, that measured air-borne sound values 22 acquired by microphone 20 may be tapped off by processing unit 30. Processing unit 30 is configured to determine, as a function of measured air-borne sound values 22, if the wheel of rail car 15 has a flat spot on a rolling surface. In response to the determination of a flat spot, processing unit 30 is configured to generate a signal 32, which represents a detected flat spot. Device 10 includes a storage unit 50 or also a communications unit 60. Communications unit 60 is connected to processing unit 30 in such a manner, that signal 32 may be transmitted with the aid of communications unit 60. Communications unit 60 may be, for example, a Bluetooth, WLAN or GSM module for wireless transmission of a signal, but wired transmission via, e.g., a USB module is also conceivable. Storage unit 50 is connected to processing unit 30 in such a manner, that signal 32 may be transmitted from processing unit 30 to storage unit 50 and stored in storage unit 50, and also fetched out of it again. Optionally, device 10 even has a motion sensor 25. This motion sensor 25 is connected to processing unit 30 in such a manner, that an interrupt signal 27 may be transmitted from motion sensor 25 to processing unit 30. Motion sensor 25 is configured to transmit an interrupt signal 27 to processing unit 30 in response to a movement of rail car 15, which means that processing unit 30 may recognize that rail car 15 is in motion. However, if such an interrupt signal 27 is not received by processing unit 30, then it may allow device 10 to remain in a quiescent state.

[0026] In one alternative exemplary embodiment not shown graphically, device 10 is not mountable directly to rail car 15, but to a mobile object in rail car 15. Such a mobile object may be a package or a transport pallet. The structure-borne sound of rail car 15 is then transmitted by the mobile object, which, in turn, converts the structure-borne sound to air-borne sound and transmits it via acoustic waveguide 40 to microphone 20. Accordingly, boundary surface 16 is then, for example, a wall of the mobile object. Optionally, device 10 may also include further sensor technology, such as an acceleration sensor, a light sensor, or a moisture sensor. This allows device 10 to be used for monitoring the mobile object during transport, for example, by configuring processing unit 30 to additionally store measured values acquired by this sensor technology in storage unit 50.

[0027] FIG. 2 shows an exemplary embodiment of a method of the present invention for checking a wheel of a rail car for flat spots. First, in a method step a, measured air-borne sound values 22 are acquired by an electromechanical microphone 20 within a first time span T1. In a method step b, an evaluation signal 35 is subsequently ascertained by a processing unit 30, from the acquired, measured air-borne sound values 22. In this context, evaluation signal 35 is ascertained, by first low-pass filtering and high-pass filtering the ascertained, measured air-borne sound values 22. Alternatively, acquired, measured air-borne sound values 22 may also be initially high-pass filtered, and then low-pass filtered. Background noise is suppressed by the low-pass filtering, and the signal is smoothed by the high-pass filtering. The filtered, measured values are then differentiated with respect to time, followed by the squaring of the time derivative. Subsequently, starting from the result of the squaring, averaging is then carried out, in order to ultimately obtain evaluation signal 35. This evaluation signal 35 represents the energy concentration of acquired, measured air-borne sound values 22, that is, the vibrations propagating through rail car 15, which are converted to air-borne sound and detected by microphone 20. After method step b, then, in a method step c, whether or not the wheel has a flat spot, is determined by processing unit 30 as a function of evaluation signal 35. The determination as to whether the wheel of rail car 15 has a flat spot takes place in method step c, by checking if evaluation signal 35 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 each occur within a second time span T2 after or prior to the largest periodic peak, being ignored. The period of the peaks, that is, the time interval of the peaks, which are generated by flat spots, may also be estimated, for example, from the speed of rail car 15 and the circumference of the wheels, in order to carry out a plausibility check as to whether the measured, periodic peaks have been produced by a flat spot. If such a periodic peak is then selected, it is subsequently checked if a derivative of evaluation signal 35 with respect to time exhibits both a negative and a positive slope in the region of the periodic peak. If this is the case, it is further checked if the periodic peak is greater than a threshold value 37. If this is so, it is then determined that the wheel has a flat spot. In addition, the size of the flat spot may be deduced from the height and width of the peak, in view of the speed and the distance of the device from the wheel. If a flat spot is determined in method step c, then the method is continued at method step d. In method step d, a signal 32, which represents a particular flat spot, is generated by processing unit 30. However, if no flat spot is determined in method step c, the method is ended.

[0028] After signal 32 is generated in method step d, then a further method step e, or also a method step f are optionally executed. In this context, in method step e, the signal 32 generated is stored in a storage unit 50. In method step f, signal 32 is transmitted, in particular, wirelessly, by a communications unit 60. A further, optional method step g may additionally be executed prior to method step a. In this method step g, an interrupt signal 27 is received from motion sensor 25, and when such an interrupt signal 27 is received, the method continues at method step a.

[0029] FIG. 3 shows a curve of a measured air-borne sound value versus time, as well as the corresponding, ascertained evaluation signal 35 from this measured air-borne sound value characteristic. A typical plot of measured air-borne sound values 22 versus time t is shown. In this connection, measured air-borne sound values 22 have been acquired within a first time span T1. As described in accordance with FIG. 2, an evaluation signal 35 is ascertained from measured air-borne sound values 22. This evaluation signal 35 typically exhibits different characteristic spots. Thus, at the beginning, evaluation signal 35 includes a first, small peak 71 followed by an additional small peak 72 and a large peak 73. After large peak 73, the further, small peak 72 and large peak 73 occur again, which is why these may be assumed to be periodic. With regard to shape, peaks 72 and 73 each resemble a shark fin, that is, they increase in both a concave and convex manner and decrease steeply at the end; this being an indication of flat spots. In comparison, first small peak 71 does not have such a shape and is also not periodic, that is, it does not recur. Thus, it may be assumed that this first, small peak 71 was not caused by a flat spot, but is an artifact. In addition, it is apparent that further, small peaks 72 are beneath a threshold value 37 and large peaks 73 are above threshold value 73. In this case, further, small peaks 72 are each within a second time span T2 prior to or after large peaks 73. This, in turn, is an indication that further, small peaks 72 are caused by a neighboring flat spot and may therefore be ignored.