PURPOSE: To adequately recognize the state of an object system. CONSTITUTION: This device is equipped with a dust sensor 107 which detects sucked dust and dirt, a fractal-dimension calculation part 1 which calculates a fractal dimension of the output of the dust sensor 107, a pulse frequency detection part 2 which detects the frequency of the output of the dust sensor 107, and a state decision part 3 which decides the state of the sucked dust and dirt on the basis of the obtained fractal dimension and frequency and controls a motor fan 106 according to the decision result.
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