Full-range displacement sensor with dual FBGs combined cantilever beam based on magnetic grating

We propose a full-range displacement sensor system based on double fiber Bragg gratings (FBGs) with a cantilever beam. This sensor adopts a magnetic scale as a unique transmission mechanism. By combining a simple and low-cost cantilever beam structure makes the sensing probe very easy to realize. The optimal magnetic gap was explored through multiple sets of numerical simulations. The experiment proved the sine relationship between the center wavelength shifts of FBGs and the linear displacement, proving the feasibility of this method. Results indicate that the amplitude of the tensile compression load of FBGs are 169.76 με and 296.12 με. The fitting linearity based on sinusoidal function at an air gap of 3.5 mm is 0.9663 and 0.9566. The direction of motion can be determined by the phase difference between two FBGs. Moreover, the difference of double FBGs can realize the effect of temperature compensation. Thus, this sensor can achieve non-contact, temperature-independent, and full-range measurements. It can also be exploited to measure other parameters such as angular velocity, acceleration, and magnetic field strength.