Self-Referenced Broad-Range Optical Rotation Sensor for Flight Control Applications

In this paper, we present a self-referenced broad range optical rotary sensor (ORS) for avionics applications. To achieve the high reliability required for aerospace use, the rotary encoder operates ratiometrically to make it insensitive to source light power variation. This sensor has a higher operating range than rotary variable differential transformers (RVDTs) currently used in fly-by-wire aircraft. The ORS encoder is fabricated on an antireflection coated glass substrate with a reflective aluminum coating. Experimental results prove that the sensor accuracy is 0.8% over the full rotation range from 0 degrees to 356.5 degrees. The proposed ORS has better accuracy and an operating range of at least twice that of RVDTs, which have an accuracy of 1% over a full range of only 80 degrees. We also test the insensitivity of the sensor to source fluctuations, which confirms that the sensor is self-referencing.