Vibration Measurement of an Unbalanced Metallic Shaft Using Electrostatic Sensors

Vibration measurement of a rotary shaft is essential for the diagnosis and prognosis of industrial rotating machinery. However, the imbalance of a shaft, as quantified through vibration displacement, is the most common cause of machine vibration. The objective of this paper is to develop a novel technique through electrostatic sensing for the online, continuous and noncontact displacement measurement of a rotary shaft due to imbalance faults. A mathematical model is established to extract useful information about the shaft displacement vibration from the simulated signal in the frequency domain. Experimental tests were conducted on a purpose-built test rig to measure the displacement vibration of the shaft. An eccentric shaft was tested with the output signal from the electrostatic sensor analyzed. The effectiveness of the proposed method is verified through computer simulation and experimental tests. Results obtained indicate that the measurement system yields a relative error of within +/- 0.6% in the displacement measurement.