What specific type of sensor data is analyzed in cepstrum analysis for WEC condition monitoring?

Cepstrum analysis, used for condition monitoring in Wave Energy Converters (WECs), analyzes vibration data acquired from accelerometers. Accelerometers are sensors that measure acceleration, which is directly related to the vibration levels of a machine or structure. The vibration data, typically recorded as a time-domain signal, contains information about the various mechanical components within the WEC, such as gears, bearings, and shafts. Cepstrum analysis is particularly useful for detecting periodicities in the frequency spectrum of the vibration signal. For example, if a bearing has a defect, it will generate vibrations at specific frequencies related to the bearing's geometry and rotational speed. These frequencies, although present in the frequency spectrum, can be difficult to detect due to the presence of other vibrations and noise. Cepstrum analysis transforms the frequency spectrum into a "cepstrum," which highlights periodic components, making it easier to identify the frequencies associated with specific faults. The cepstrum can reveal subtle changes in the vibration patterns that indicate the onset of a fault, allowing for early detection and preventive maintenance.