Extraction of angle deterministic signals in the presence of stationary speed fluctuations with cyclostationary blind source separation

This paper addresses the use of a cyclostationary blind source separation algorithm (namely RRCR) to extract angle deterministic signals from mechanical rotating machines in presence of stationary speed fluctuations. This means that only phase fluctuations while machine is running in steady-state conditions are considered while run-up or run-down speed variations are not taken into account. The machine is also supposed to run in idle conditions so non-stationary phenomena due to the load are not considered. It is theoretically assessed that in such operating conditions the deterministic (periodic) signal in the angle domain becomes cyclostationary at first and second orders in the time domain. This fact justifies the use of the RRCR algorithm, which is able to directly extract the angle deterministic signal from the time domain without performing any kind of interpolation. This is particularly valuable when angular resampling fails because of uncontrolled speed fluctuations. The capability of the proposed approach is verified by means of simulated and actual vibration signals captured on a pneumatic screwdriver handle. In this particular case not only the extraction of the angle deterministic part can be performed but also the separation of the main sources of excitation (i.e. motor shaft imbalance, epyciloidal gear meshing and air pressure forces) affecting the user hand during operations.

► Extraction of angle deterministic signals (ADSs) from mechanical rotating machines in presence of stationary speed fluctuations. ► Where some speed fluctuations occur from cycle to cycle and within the cycle itself, the Time Synchronous Average fails in estimating the ADS. ► It is theoretically assessed that the ADS becomes cyclostationary at first and second orders in the time domain. ► Use of a cyclostationary blind source separation algorithm (namely RRCR) for simulated and actual (screwdrivers) time signals to extract the ADS.