Bearing monitoring apparatus and method

A system comprising:

• a bearing,
• at least one strain sensor mounted in at least one circumferential groove in an outer ring of the bearing, and
• a bearing monitoring apparatus having;
• at least one interface for receiving strain signals detected by the at least one strain sensor and at least one data processing unit configured to monitor the bearing by detecting bearing defects based on the strain signals, wherein the data processing unit is configured to:
• a. subject the strain signal to a high pass filtering, wherein a limit frequency of the high pass filter is set higher than a typical ball pass frequency of the bearing to be monitored;
• b. calculate a quantity representative of an amplitude of an envelope signal of the high-pass filtered strain signal;
• c. compare the quantity representative of the amplitude of the envelope signal with an envelope threshold value;
• d. classify the bearing using the result of the envelope comparison;
• and
• e. issue at least one warning signal if the bearing is classified as defective;
• and
• wherein the data processing unit is further configured to:
• f. determine at least one fluctuation signal representative for a fluctuation width of the high-pass filtered strain signal;
• g. compare the at least one fluctuation signal with a fluctuation threshold value;
• and
• h. use the result of the fluctuation comparison in said classification of the bearing,
• receiving the signals of the at least one strain sensor via the interface.

A method for monitoring a bearing using strain signals detected by at least one strain sensor mounted in at least one circumferential groove in an outer ring of a bearing, the method comprising the steps of:

• a. subjecting the strain signal to a high pass filtering, wherein a limit frequency of the high pass filter is set higher than a typical ball pass frequency of the bearing to be monitored;
• b. calculating a quantity representative of an amplitude of an envelope signal of the high-pass filtered strain signal;
• c. comparing the quantity representative of the amplitude of the envelope signal with an envelope threshold value;
• d. classifying the bearing using the result of the envelope comparison;
• and
• e. issuing at least one warning signal if the bearing is classified as defective;
• f. determining a fluctuation signal representative for a fluctuation width of the high-pass filtered strain signal;
• g. comparing the fluctuation signal with a fluctuation threshold value;
• and
• h. using the result of the fluctuation comparison in said classification of the bearing.