Document Type

Dissertation

Publication Date

1994

Abstract

An optical diagnostic system capable of measuring angular displacements in a torsionally loaded shaft through noncontact means has been developed. Conventional torsion diagnostic mechanisms must come in contact with the shaft to be analyzed. The signal-to-noise ratio response of conventional systems is compromised by dirt and wear. Another consequence of these devices is that the shaft being diagnosed must be cut in half to implement the mechanism.

In this work, the shaft angle of twist (ϕ) is measured utilizing precision optics and HeNe laser light. Accuracy in the placement and orientation of mirrors on the shaft surface is shown to be crucial, since precise bending of the laser light is required to effectively measure twisting distortions.

A CdS photoresistor was augmented with a high gain operational amplifier for light sensing. This system was then implemented as the receiving source of optically measured torsional displacements. Experimental results confirm that the voltage response of the amplifier varies linearly with ϕ. It is shown that the amplifier output voltage varies as a function of the amount of optical energy received from the shaft reflected laser light. The amount of optical energy transmitted to the circuit is dependent on the angle of twist in the shaft. The system performs these tasks without any physical contact between the laser source, shaft, or the photocircuitry.

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