Wide-Range Fiber Bragg Grating Tilt Sensor Based on a Cam Structure

This work presents a fiber Bragg grating (FBG) wide-range tilt sensor based on a cam structure. Two FBGs are fixed on a specially-designed sensor shell. When one FBG is stretched by the rotating cam driven by tilt, the other FBG moves along a standard semicircle with a constant radius, and compensates for temperature variations of the stretched FBG. By detecting the difference of the central wavelength shifts of two FBGs, variations of the tilt angle can be measured. The detailed mechanical structure design and measurement theory of the sensor is presented, and the sensor prototype is discussed. Testing results of comprehensive performance show that there is a good linear relationship between the tilt angle and the central wavelength of the FBG over three intervals from -90° to 90°. The repeatability and creep resistance of the FBG tilt sensor are good, the measuring accuracy is 1.516°, and the measuring resolution is 0.003°. The measurement range is much larger than comparable existing sensors, and it avoids cross-sensitivity between temperature and strain for FBG. The sensitivity of the sensor can be easily adjusted by changing the outline of the cam, or the length of the optical fiber between two fixed points.