Development of a systematic instrumentation methodology for continuous torque measurement in high-capacity shafts

Abstract

This paper presents the development of a systematic instrumentation methodology for continuous torque measurement in high-capacity shafts, based on the application of strain gauges. Within the proposed methodology, systematically derived solutions to the most important challenges in the development of instrumented shafts for torque measurement are presented, including the determination of optimal strain gauge locations, their arrangement and number, as well as the configuration of their connection into Wheatstone bridges. The main objective of the proposed methodology is to achieve high sensitivity and accuracy of torque measurement while simultaneously neutralizing parasitic effects in the output signal of the Wheatstone bridge. In addition, the model-based calibration procedure of the measurement system and an inverse torque determination algorithm based on the output signal of the Wheatstone bridge are presented. The developed methodology was tested on a finite element method (FEM) model of a high-capacity wind turbine shaft under various loading conditions, considering the combined effects of torque (to be measured), bending moments, as well as axial and transverse forces. The obtained results demonstrate that the developed methodology enables high numerical consistency in torque determination, with deviations between the prescribed torque in the FEM model and the torque obtained by inverse determination being less than 0.04%. Thus, it is confirmed that the proposed methodology can be successfully applied in the development of high-capacity instrumented shafts intended for continuous torque measurement.