Feedforward Neural Network for Force Coding of an MRI-Compatible Tactile Sensor Array Based on Fiber Bragg Grating

Abstract

This work shows the development and characterization of a fiber optic tactile sensor based on Fiber Bragg Grating (FBG) technology. The sensor is a 3×3 array of FBGs encapsulated in a PDMS compliant polymer. The strain experienced by each FBG is transduced into a Bragg wavelength shift and the inverse characteristics of the sensor were computed by means of a feedforward neural network. A 21 mN RMSE error was achieved in estimating the force over the 8 N experimented load range while including all probing sites in the neural network training procedure, whereas the median force RMSE was 199 mN across the 200 instances of a Monte Carlo randomized selection of experimental sessions to evaluate the calibration under generalized probing conditions. The static metrological properties and the possibility to fabricate sensors with relatively high spatial resolution make the proposed design attractive for the sensorization of robotic hands. Furthermore, the proved MRI-compatibility of the sensor opens other application scenarios, such as the possibility to employ the array for force measurement during functional MRI-measured brain activation.

Tactile Sensor Array with Fiber Bragg Gratings in Quasi-Distributed Sensing

“…This behavior indicates a coupled response among the FBGs, allowing its application in a quasi-distributed sensing system. An important feature is the linearity of the FBG responses that allows the use of the optimization method described in (4).…”

“…Some works have pointed to the use of arrays of fiber Bragg grating-(FBG-) based transducers in tactile sensing systems (TSS) applied to the mapping of forces in robotic systems [1], biomedical [2], and medical areas [3,4]. These systems make use of the FBG multiplexing capability.…”

“…Despite the benefits of these traditional technologies, they are not suitable for applications that require the interconnection of many sensor elements, low power consumption, and high immunity to electromagnetic interference [4]. In this sense, the outstanding characteristics of FBG sensors such as reduced size and weight, flexibility, easiness of encapsulation and multiplexing, low loss transmission, high immunity to electromagnetic interference, resistance to temperature, and electrical passivity [16] have been successfully explored.…”

Development of a Large-Area 8 × 8 Tactile Sensing Array with High Sensitivity

“…Saccomandi et al presented a fiber-optic tactile sensor based on fiber Bragg grating (FBG) technology. (10) The static metrological properties and relatively high spatial resolution make the proposed device attractive for robotic hands.…”

Design and Testing of a 2D Optical Fiber Sensor for Building Tilt Monitoring Based on Fiber Bragg Gratings

“…In recent years, optical fiber sensors made of silicon-based optical fibers or polymer optical fibers have been commonly utilized for numerous types of physical detection [1][2][3][4][5][6][7][8][9][10][11][12] because a fiber sensor has many features that are better than conventional electronic sensors. Fiber optic sensors can be used for large-scale distributed monitoring, and also have anti-electromagnetic interference, high sensitivity, light weight, good adaptability in shape, and electrical isolation.…”