1999 Volume 24 Issue 74 Pages 23-35
The hierarchic frame network has been proposed as a new diagnostic model that can be applied to most of air conditioning systems. In the present study, stepwise diagnosis was used as an evaluation item, and the practicality and usability of the diagnostic model were verified in actual air conditioning systems. In the first diagnostic step, which detects fault symptoms, it was possible to perform fault detection without errors by considering the range of design specifications, safety device settings, and operating conditions with the setting of threshold values. In the second diagnostic step, which classifies the types of fault phenomena, it was possible, by adjusting the threshold which was based on statistical analysis of actual operating data and by setting a condition of high frequency for fault detection, to classify fault phenomena from which noise superimposed on the measurement signal had been removed. In the third diagnostic step, which performs fault localization, it was possible to identify faulty apparatus by inferring the fault phenomenon using knowledge of the frame network and rules. And in the fourth diagnostic step, it was possible to identify the cause of the fault by inferring the fault phenomenon using a fault tree for each apparatus. After confirming these diagnosis results in actual air conditioning systems and repairing the causes of faults, the diagnosis results returned to normal values, thus verifying that the identification of faults had been correctly carried out. The above verification process indicates the practicality and usability of a diagnostic model employing a hierarchic frame network.
