21-09-2017, 01:04 PM
The information collected from the sensors is used to determine the health of a sensor. Once a normal mode of operation is established, any deviation from normal behavior indicates a change. This change may be due to a malfunction of the sensor (s) or system (or process). It is assumed that the stepped and decreasing characteristics, as well as the sensor disturbances, are exponential. An RC network is used to model the main process, which is defined by a step-up, drift, and step-down. Sensor and peak disturbances are added while the system is drifting. The system runs for a period of at least three main process time constants each time a process characteristic (eg, step change) occurs. The Short-Time Signal Fourier Transform is taken with the Hamming window. Three window widths are used. The DC value is removed from the data in windows before taking the FFT.