Fluidic two-axis time modulated position sensor

Abstract

The paper describes a fluidic means of sensing angular displacements between the rotor and case of a two-axis displacement gyroscope. The sensor consists of an eccentric jet pipe located on the gyroscopic element and a quadranted fluidic receiver which captures the jet pipe flow across a small gap. The resulting pressure pulses in the receiver quadrants are added and subtracted in such a manner that the variation in pulse duty cycle is a measure of relative displacement between the rotor and the receiver. The processing of the receiver signals is accomplished by a cascade of bistable fluidic elements which eliminates the problem of cross-coupling angular inputs between the two mutually orthogonal input axes. Results of tests conducted to evaluate the sensor's capability to serve as a means of angle determination for an inertial component are included in the form of oscilloscope traces. The fluidic waveforms and plots of per cent modulation versus position gives a complete picture of the accuracy of the mathematical model to that of the actual device. Excellent correlation (±1.0 per cent) was obtained between test and theoretical results. Fabrication techniques used for the fluidic circuitry are discussed, including Electro-Discharge Machining (EDM), Pantograph engraving and conventional milling methods.