Development of a non-contact torque transducer based on the laser speckle contrast method

Abstract

Abstract. When a torque measurement is required, torque transducers show many drawbacks during their use: the usual limits are the need for contact and the effects on shaft line parameters. A new approach is proposed in this work: a non-contact torque meter for a machine shaft has been developed. It carries out torque measurements evaluating the torsional displacement between two distinct sections of the shaft, through the monitoring of their roughness.The sensing principle employed is the classical laser speckle contrast method. The outcoming intensity scattered by the rough surface is processed by a cross-correlation function. In this way, the angular torsion of two distinct sections is obtained. It is therefore possible to point out the applied torque knowing the shaft torsional stiffness.

Non-intrusive torque measurement for rotating shafts using optical sensing of zebra-tapes

“…In addition to performance limitations, these methods usually suffer from low range-to-resolution ratio [11]. A laser torque meter was first presented in [16] and later analysed in [17][18][19]. This instrument is based on the cross-correlation of the periodic speckle patterns generated by two axially separated laser beams on a rotating shaft, having known mechanical proprieties.…”