Development of a tactile sensor based on optical fiber specklegram analysis and sensor data fusion technique

The development of a tactile sensor based on optical fiber specklegram analysis is reported. The device is comprised of 9 microbending transducers connected to 3 multimode fibers, and attached to a 30 × 30 mm2 touching surface in a matrix arrange. The output fiber speckle fields, produced by coherent light transmission through the multimode waveguides, are processed for evaluation of the normalized inner-product coefficients, being further correlated to the external load characteristics according to a specklegram referencing approach. Finally, the magnitude and location of the forces applied over the tactile frame are estimated by means of a data fusion technique, yielding the probabilistic distribution of the mechanical disturbances. The sensor characterization indicated a 0.5 N−1 sensitivity, with capability to detect variations of 1 mm in force location, being comparable to the requirements for tactile technologies. Moreover, the data fusion approach provided the estimation of the load distribution with 0.86 relative accuracy, allowing the assessment of tactile variables based on the response of only 3 sensing fibers and without utilizing wavelength multiplexing schemes.