Dual-axis fiber Bragg grating tilt sensor based on universal joint structure

•The sensor is composed of a universal joint, which includes an upper fixed bracket, two cross-connected shafts and bearings, and a lower fixed bracket, as well as a pole and a pendulum. This design enables dual-axis measurement.•The sensitivity of the X and Y axes of the sensor are 229.8 pm/° and 224.9 pm/° respectively, and the tilt measurement accuracy is 0.48°.•A testing system for tilt and temperature experiments has been constructed using equipment such as a tilt platform, a temperature control chamber, and an optical fiber sensing system.•A prototype based on the design principle is prepared for engineering experiments. Inclination angle measurement is widely used in fields such as infrastructure health, power engineering safety, and earthquake monitoring. In response to the problem that existing inclinometers based on the pendulum structure can only measure a single axial inclination angle, a dual-axis Fiber Bragg Grating (FBG) tilt sensor based on a universal joint structure is proposed. SolidWorks was used to establish a sensor model and conduct theoretical analysis. The structural parameters of the sensor were optimized using the control variable method. Based on the optimization results, a physical sensor was developed, and an inclination and temperature testing system was set up for performance testing. The results show that within a measurement range of ± 5°, the sensitivities of the X and Y axes of the sensor are 229.8 pm/° and 224.9 pm/°, respectively, with a resolution of approximately 4.4 × 10-4°. The tilt accuracy of the sensor is approximately 0.48°, and it exhibits good creep resistance and stability during long-term measurements, as well as temperature self-compensation capabilities. The research results provide a new reference for the development of similar dual-axis tilt measurement sensors.