Detecting deformation of a soft cylindrical structure using piezoelectric sensors

In this paper, we propose a model for the electrical responses of a soft cylindrical structure with shear deformations using piezoelectric sensors. Specifically, to analyze the cylindrical structure during movement, we assumed that a shear force was applied to the flat surface on the top of the structure. Using this force, we established a model using the Euler-Bernoulli beam theory and estimated the electrical responses of the sensors generated by its deformation. To validate the theoretical analysis, a soft cylindrical structure was fabricated using silicone containing piezoelectric sensors. Moreover, a series of tests were performed by applying a tensile testing machine and vibration exciter to the soft structure. During the experiments, we observed the sensor outputs while generating vibrations in the form of triangular and sinusoidal waves. The experimental outputs demonstrate that the sensors can distinguish the displacements and directions of the structural deformations, similar to our predictive model, through the voltage outputs and phase variations of the sensors. Moreover, parametric studies were performed to investigate the sensor responses under structural deformations affected by four parameters related to the material and external forces: the Young's modulus, radius, mass density, and frequency of the sinusoidal shear force.