Rotary machine state observation device, rotary machine, and rotary machine state observation method

A rotary machine state observation method, comprising:

• detecting, via a gap sensor, a distance between an impeller of a rotary machine and the gap sensor, the gap sensor being provided at an interval in a radial direction between the impeller and the gap sensor;
• converting, via an analog-to-digital converter (ADC), a detection signal from an analog signal into a digital signal, the detection signal being detected by the gap sensor at a predetermined sampling period;
• comparing, via a digital signal processor, the detection signal converted by the ADC with a threshold value;
• separating, via a digital signal processor, the detection signal equal to or more than the threshold value as a vane detection signal considered to be for detection of a vane of the impeller and the detection signal less than the threshold value as a non-vane detection signal considered not to be for detection of the vane;
• extracting, via the digital signal processor, a vane detection signal considered to be for a peak of the vane by comparing the vane detection signal with vane detection signals corresponding to other vanes and the non-vane detection signal;
• and
• determining, via the digital signal processor, a state of the impeller on the basis of the extracted vane detection signal.