Method and device for identifying a damaged bearing of a rotating shaft

• US 7,743,658 B2
• Filed: 10/18/2005
• Issued: 06/29/2010
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Filbry, Karl-Heinz
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): FAYYAZ, NASHMIYA SAQIB
• Application Number:
  US11/577,544
• Publication Number:
  US 20080083280A1
• Time in Patent Office: 1,715 Days
• Field of Search: 735/79, 736/60, 736/02, 735/93
• US Class Current: 73/579
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

The invention relates to a method and a device for identifying a damaged bearing (4a, 4b) of a rotating shaft (1). According to the invention: the rotational speed (n) of the shaft (1) is determined; the alternating component (n_AC) of the rotational speed (n) is determined, together with a smooth curve (h) of said alternating component (n_AC) of the rotational speed (n); the smooth curve (h) is converted into the frequency range and a frequency response (B) of the value of the smooth curve (h) is determined. Said frequency response (B) of the value of the curve is monitored for the passing of a threshold value (G₁, G₂, G₃, G₄) and if said threshold value (G₁, G₂, G₃, G₄) is exceeded, a damaged bearing (4a, 4b) is identified. The invention thus provides a method and a device for identifying a damaged bearing (4a, 4b) of a rotating shaft (1) of a motor, which do not require a vibration sensor (11) to identify a damaged bearing (4a, 4b) of said shaft (1).

Claims

1. A method for identifying a damaged bearing of a rotating motor shaft of a motor, comprising the steps of:

determining a rotation speed of the motor shaft,

determining a temporally varying component of the rotation speed,

determining an envelope of the temporally varying component of the rotation speed by rectifying the temporally varying component and low-pass filtering the rectified temporally varying component,

transforming the envelope into the frequency domain and determining an absolute value of a frequency response of the envelope in the frequency domain,

monitoring the absolute value of the frequency response to detect if the absolute value exceeds a limit value, and

identifying the bearing as being damaged if the limit value is exceeded.

2. The method as claimed in claim 1, and further comprising the step of monitoring if the limit value is exceeded in a region where a bearing pass frequency is located.

3. The method as claimed in claim 2, wherein the bearing pass frequency is stored in a memory disposed on the motor.

4. The method as claimed in claim 1, and further comprising the steps of determining the mtation speed of the shaft by measuring a position of the shaft with a position sensor and differentiating the measured position with respect to time.

6. A computer program product embodied on a computer-readable medium, said computer program including computer code which, when executed on a computer, enables the computer to perform the method as claimed in claim 1.

5. A device for identifying a damaged bearing of a rotating motor shaft of a motor, with the device being embodied as an open-loop or a closed-loop controller for respective open-loop or closed-loop control of the motor, the device comprising:

means for determining a rotation speed of the motor shaft,

means for determining a temporally varying component of the rotation speed,

means for determining an envelope of the temporally varying component of the rotation speed by rectifying the temporally varying component and low-pass filtering the rectified temporally varying component,

means for transforming the envelope into the frequency domain and determining an absolute value of a frequency response of the envelope in the frequency domain, and

means for monitoring the absolute value of the frequency response to detect if the absolute value exceeds a limit value, and identifying the bearing as being damaged if the limit value is exceeded.

7. A device for identifying a damaged bearing of a rotating motor shaft of a motor, with the device being embodied as an open-loop or a closed-loop controller for respective open-loop or closed-loop control of the motor, the device comprising:

a position sensor for measuring a rotational position of the motor shaft,

a differentiator for differentiating the measured rotational position with respect to time to determine a rotation speed of the motor shaft,

a high-pass filter for determining a temporally varying component of the rotation speed,

a rectifier for rectifying the temporally varying component,

a low-pass filter for determining from the rectified temporally varying component an envelope of the temporally varying component of the rotation speed,

a Fourier transformation unit for determining an absolute value of a frequency response of the envelope in the frequency domain, and

a limit detector for detecting if the absolute value exceeds a predetermined limit value and identifying the bearing as being damaged if the limit value is exceeded.