PURPOSE: To make a highly accurate decision of abnormality regardless of the individual variation range of status amount by assuming the distribution of respective populations at the normal, abnormal and monitoring times of a machine to be normal distribution and making a decision that the machine is abnormal at the time of monitoring if the normal distribution at the time of monitoring is closer to that at the abnormal time than that at the normal time.
CONSTITUTION: A status amount measuring unit 2, e.g. an oscillation sensor, is disposed at a position susceptible to the status change of a machine 1. Status amount of the machine 1 is measured and subjected to A/D conversion 3 before being processed through a μCPU 4. In other words, status amounts are collected at normal and abnormal times and, at the time of monitoring, it is collected in time sequence. Mean value and variance value are then determined for each sample of status amount and the test statistic of the difference of population mean or the ratio of population variance is calculated for the normal and monitoring times and the abnormal and monitoring times based on the sample mean and variance. The test statics are compared each other and such a decision is made that the machine is in an abnormal state at the time of monitoring it the normal distribution at the time of monitoring is closer to the normal distribution for abnormal time than that for normal time.
YAMAGUCHI HIROSHI
ONO MITSUHARU
HYODO FUMIO
SHIKOKU KEISOKU KOGYO KK
ENTOROPII SOFTWARE KENKYUSHO K
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