A Vibration Signal Family of Impact Events

Many mechanical and electromechanical devices work by the impact principle. A movable part in the device switches between two stable positions and each working cycle causes an impact inside the device. This process can be found for example in relays and valves. In industrial systems like plants and machines, condition based maintenance is of rising importance to reduce both the cost of maintenance and to avoid faults in the system. Vibration analysis is an often used method to monitor the state of machines and devices. The vibration signals of switching events of the above mentioned devices are often non-stationary. Another problem is that the length of vibration impulses are often very short (only some few milliseconds). These difficulties are contribury facts as to why condition based maintenance is not established very well and wide for the above mentioned devices like relays or valves. In this paper, we present information about the vibration signals of these devices. There are similarities and relations between the different devices, which lead to a family of signals which can be analysed with similar algorithms. A new approach is presented using segmentation of the signals in the time-domain. This step in signal pre-processing is demonstrated to be very important for all later classification and analysing-tasks. After the presented pre-processing steps it is possible to develop classifiers to monitor the state of these devices. Because of the high degree of variance in the vibration signal and the other characteristics of this signal family (short duration and non-stationarity), the classification results are only convincing with intensive and sophisticated pre-processing.