Design and testing of a non-intrusive torque measurement system

Abstract

This thesis details the initial development of a non-intrusive torque measurement system to measure torque in a rotating driveshaft like those commonly found on internal combustion engine powered irrigation pumping plants. A typical driveshaft used in pumping plant applications consists of flanged U-joints on each end with a constant cross-section steele tube portion connecting the U-joints. The photoelectric sensor based system was able to predict torque to within 3︢9.1 N-m (346 in-lbs) under constant rpm conditions. Two sensor types, phototransistor and photodiode, were tested. The photodiode sensor was tested with two emitter types: infrared LED and red laser. No significant difference in response was found using either the LED or red laser emmitters. Both the photoelectric and photodiode sensor measurements showed correlation to actual torque. The photoelectric sensor configuration correlation had a standard error of 5︢% of a typical natural-gas pumping plant installation running at 773.9 N-m of torque. The sensors were mounted independent of the driveshaft and measured the phaseshift of two pins mounted on the shaft as they passed through the photosensing area. This caused extreme sensitivity to vibration of the engine and driveshaft. A similar design with a temporary mount connected to the shaft and transmitting the response signal via radio frequency telemetry could decrease the effects of vibration on the system.