Optimization of a Force Sensor Realized by Modified Plastic Optical Fibers Integral With a Cantilever

In this work, an optimized force sensor system was simulated, fabricated, and experimentally tested. It is based on a modified plastic optical fiber (POF) bonded on the back side of a spring-steel cantilever. The POF is opportunely modified with several notches in order to enhance the performance of the sensor system. In particular, an optimization analysis of the position and characteristics of these notches was presented. Firstly, a numerical analysis based on finite element method (FEM) simulations was conducted to determine where the cantilever's elastic stress is maximum, resulting in its constrained end. Subsequently, an experimental analysis was carried out to characterize the sensor by fixing one end of the cantilever and applying transversal forces on the unconstrained end, applying different weights. Several preliminary optimization tests were performed to establish the best working condition in terms of light source and notches parameters, i.e. depth and periodicity. From the experimental results, the optimized force sensor system denoted a very good linear behaviour in the range from 50 mN to 300 mN, with a sensitivity and resolution equal to 110.34 mV/N and 5 mN, respectively.