Abstract: Real-time tilt monitoring is very important for the safety of large wind power towers, offshore floating cranes, and other major mechanical equipment. The existing tilt sensors based on the electromagnetic signals have some common shortcomings in practical applications such as inapplicability in harsh environments, poor large-scale networking capabilities, and insufficient signal transmission. Therefore, this work developed a novel fiber Bragg grating(FBG) tilt sensor. Based on equal strength beam, we proposed a new sensing mechanism with a movable and spring damping connection between the mass and the beam. Compared with the existing design, the mass swing induced by the vibration of the measured object can be absorbed, which eliminates the coupling output caused by vibration interference. The mechanical structure, operation principle, and corresponding theoretical model are presented in detail. Then a FBG tilt sensor prototype was manufactured and fully tested. Test results show that the sensor provides a high sensitivity of 146.899 pm/(°) within a range of ±15°, a measuring resolution of 6.8×10^-4 °, a repeatability error less than 4.125%. Furthermore, good creep resistance, and good temperature compensation and applicability from -40℃ to 60℃ have also been demonstrated. Through comparative testing, the sensor possesses a measuring accuracy of 0.157° and good vibration resistance. These results demonstrate that the sensor has strong applicability in safety monitoring of major mechanical equipment.

Key words: fiber Bragg grating, tilt sensor, mechanical equipment, safety monitoring