Identification of a force-sensing resistor for tactile applications

A force-sensing resistor is a conductive polymer that exhibits a decrease in resistance as the force applied at its surface increases. The aim of this study is to identify the characteristics of the force-sensing resistor for use in a refreshable and portable E-Braille device that can assist the blind and visually impaired persons. The force-sensing resistor is placed within a component dynamic testing device that is composed of a linear actuator that can generate different displacement loading profiles and a load cell that measures the applied forces. The system records the voltage, force, and the displacement profiles. Several strategies are used in the identification process. First, the mechanical properties of the force-sensing resistor are experimentally characterized. A second-order mechanical system whose parameters are function of the exciting frequency is created based on the results of this experiment. The performance of this model is evaluated using several test inputs. In an attempt to better identify the force-sensing resistor, alternative higher order linear and nonlinear models, including Hammerstein, Wiener, and Hammerstein-Wiener, are proposed using system identification techniques. The accuracy and robustness of these models are assessed using various loading profiles. The outputs of these models are compared with the experimental results.