Novel Analog Ratio-Metric Optical Rotary Encoder for Avionic Applications

In this paper, an optical, analog, self-referencing, ratio-metric, smart displacement sensor is proposed for avionic applications. The position of rotation is determined by the ratio of the transmitted and reflected light powers, which makes the sensor independent of power fluctuations. A single multi-gradient encoder design compensates for the use of a non-uniform source. An anti-reflection coated glass window with the outer diameter of 27 mm is used with an encoder pattern mapped on it by aluminum deposition. The experimental results show that the ratio of the transmitted and reflected powers has an accuracy of 0.53% over the full range, matching the specifications for avionic applications. It is also experimentally proved that the sensor operates ratio-metrically and not affected by the change in the source power, which makes it highly reliable for the avionic application. Further optimization of the design will make this type of sensor an excellent choice for future lightweight and greener aircraft technology.

I. Introduction

Rotary sensors are key components in several systems, such as motion capture devices [1], [2], industrial control application to monitor rotation of mechanical parts [1], [3]–[5], and automotive sensors for tracking steering-angle [1], [6], [7]. Rotary displacement sensors are widely employed in fly-by-wire aircraft and avionics systems for flight control purposes [8]–[12].