PURPOSE: To detect troubles in the idle time of a controlling computer without requiring a long operation time, by detecting the deviation between a target value of a control system and a feedback value with a detection level corresponding to the changing speed of the target value.
CONSTITUTION: An oil pressure servo system 3 is driven in accordance with the deviation between a target value X and a feedback value X' to obtain an output Y, and the output Y is detected by a position detector 4 to attain the feedback value X'. Meanwhile, a differentiator 6 of a trouble diagnostic device 2 operates an allowable level correcting value ΔL on a basis of the changing speed of the target value X, and an adder 7 adds an allowable level initial value L0 and the correcting value ΔL to set an allowable level L of a level detector 5. A deviation is inputted to this level detector 5, and an abnormality signal F is outputted if the deviation is higher than the allowable level set value L, and a duration detector 8 displays a trouble on a display device 9 if the duration of the abnormality signal F is longer than an allowable duration set value T.
HAYAMA YASUNOBU
ABE MITSUHIRO
OOKURA KATSUHIRO
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