# US 7,743,658 B2 · Method and device for identifying a damaged bearing of a rotating shaft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,743,658 B2 - Document ID: US7743658B2 - Status: Granted - Kind: B2 - Application number: 11/577,544 - Filed: 2005-10-18 - Published: 2008-04-10 - Granted: 2010-06-29 - Earliest claimed: 2004-10-19 - Assignees: Siemens Aktiengesellschaft - Inventors: Karl-Heinz Filbry - Web page: https://patentgrep.com/patent/US7743658B2 ## CPC - G01M 13/045: Acoustic or vibration analysis - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## 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 (nAC) of the rotational speed (n) is determined, together with a smooth curve (h) of said alternating component (nAC) 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 ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 2) The method as claimed in claim 2, wherein the bearing pass frequency is stored in a memory disposed on the motor. ### Claim 4 (depends on 1) 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. ### Claim 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. ### Claim 6 (depends on 1) 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. ### Claim 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.