The paper presents an example of Instance-Based Learning using a supervised classification
method of predicting selected ductile cast iron castings defects. The test used the algorithm
of k-nearest neighbours, which was implemented in the authors’ computer application. To
ensure its proper work it is necessary to have historical data of casting parameter values
registered during casting processes in a foundry (mould sand, pouring process, chemical
composition) as well as the percentage share of defective castings (unrepairable casting defects).
The result of an algorithm is a report with five most possible scenarios in terms of
occurrence of a cast iron casting defects and their quantity and occurrence percentage in
the casts series. During the algorithm testing, weights were adjusted for independent variables
involved in the dependent variables learning process. The algorithms used to process
numerous data sets should be characterized by high efficiency, which should be a priority
when designing applications to be implemented in industry. As it turns out in the presented
mathematical instance-based learning, the best quality of fit occurs for specific values of
accepted weights (set #5) for number k = 5 nearest neighbours and taking into account the
search criterion according to “product index”.
One of the most important issues that power companies face when trying to reduce time and cost maintenance is condition monitoring. In electricity market worldwide, a significant amount of electrical energy is produced by synchronous machines. One type of these machines is brushless synchronous generators in which the rectifier bridge is mounted on rotating shafts. Since bridge terminals are not accessible in this type of generators, it is difficult to detect the possible faults on the rectifier bridge. Therefore, in this paper, a method is proposed to facilitate the rectifier fault detection. The proposed method is then evaluated by applying two conventional kinds of faults on rectifier bridges including one diode open-circuit and two diode open-circuit (one phase open-circuit of the armature winding in the auxiliary generator in experimental set). To extract suitable features for fault detection, the wavelet transform has been used on recorded audio signals. For classifying faulty and healthy states, K-Nearest Neighbours (KNN) supervised classification method was used. The results show a good accuracy of the proposed method.