Cyclic modulation spectrum — An online algorithm

Many profitable methods of damage detection in rotating machines involve cyclostationarity. This approach exploits the fact that vibrations of a damaged machinery possess a periodic envelope. The frequency related to this periodic behavior is strictly related to one of the characteristic frequencies associated with design and specific operation of the considered machine. Nowadays, such methods are rarely implemented in industrial condition monitoring systems for several reasons. One of the main reasons is related to computational complexity. Algorithms that calculate cyclostationary features are said to be computationally expensive, thus their involvement in monitoring systems is limited. This drawback becomes critical in online systems in which the monitored features are updated just after arrival of the next measurement. Because of complexity of cyclostationary approach other tools are preferred instead, especially those which do not require intensive computations. In this paper we discuss algorithms for calculation of a basic cyclostationary tool, namely cyclic modulation spectrum (CMS). In this paper we provide several novel algorithms that update CMS when new measurements arrive.