Importance

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Abstract

A microprocessor-based torque measuring system for a twin engine-aircraft gas turbine engine installation comprises respective inductive sensors 12,14, one for each engine. The sensors are positioned to co-operate with respective pairs of toothed wheels, which are secured to axially spaced points on the engine shaft whose torque is to be sensed and have interlaced teeth whose spacing circumferentially of the wheels varies with torque. Each sensor produces a torque signal which, after suitable shaping, has a mark-space ratio representative of torque, and the respective durations of the mark and space periods of the signal are measured digitally by counting clock pulses during successive groups of mark periods and space periods. The accumulated counts are then subjected to recursive digital filtering by the microprocessor, in accordance with a predetermined function approximating the response of a second order Butterworth filter. The microprocessor then calculates the torque for each engine, using the appropriate filtered counts together with digital signals respectively representative of the temperature, stiffness and zero-torque twist of the respective shaft.

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First Claim