T55 Engine: The Challenge of Torque Measurement

This paper describes the design, development, and testing of an Improved Magnetostrictive Torquemeter (IMT) for the T55 engine family. The goals of the IMT are to improve accuracy, reliability, and maintainability, while preserving low weight and cost. This must be achieved without major redesign of the engine and its short, torsionally stiff output shaft. The approach taken to achieve these goals includes choice of a magnetostrictive material having a more linear transfer curve, and use of ratiometric signal processing, which eliminates errors resulting from variations in common mode voltage. Development of a procedure which enables field replacement of the torquemeter junction box provides a substantial maintainability improvement over previous T55 magnetostrictive torquemeters.