Design of a vibration-insensitive surface-mounted wide-range FBG tilt sensor

Tilt sensors are devices that measure the tilt or slope of an object with respect to a reference. Fibre Bragg Grating (FBG) tilt sensors are a specific type of tilt sensor that utilizes the principle of Bragg’s law in fiber optics to measure tilt angles. In a FBG tilt sensor, the optical fibre is usually placed such that there is a shift in the Bragg wavelength with the change of orientation of the monitored object thus eliciting a sensor response. The advantages of an FBG tilt sensor over traditional sensor is its high precision of measurement and insensitivity to EMI. The FBG tilt sensor in this study is designed to operate accurately and reliably in the presence of vibrations or mechanical oscillations over a range of 0-50°. The structure of the sensor consists of the sensing element attached to a single body cantilever with optimized variable cross-section for adequate strain enhancement. The sensitivity of the sensor is approximately 31 pm/° and the resonant frequency is approximately 40 Hz. A vibration isolation mechanism is designed for this sensor where a neoprene pad is attached between the main body and the mount of the sensor. A finite element analysis is conducted to comparatively verify the sensor’s performance with and without the vibration isolation scheme. It has been found from the results that the current design scheme has been effective in isolating the response of the sensor from environmental vibrations. This sensor can thus be reliably used in machines/structures subjected to random vibrations in various application areas such as aerospace, automotive, structural health monitoring, and industrial automation, where stable and accurate measurements are crucial.