Abstract
Soft robotics require flexible sensors that can realize sensitive measurements for which rigid sensors are not viable. Precise and quantitative measurement of the mechanical phenomena is necessary in all the sensors; however, in the field of soft robotics, the complex structure and physical properties of composite materials complicate the construction of a precise sensing model. In this study, a built-in sensor system for internal shear strain and stress distribution measurement is developed by embedding piezoelectric polyvinylidene fluoride polymer films within the objective soft material. Shear-strain sensing models are established by relating the piezoelectricity and cantilever bending mechanics. For validation, experiments are conducted in which the deflection of the embedded film sensors is monitored and digitized using a video camera. The shear-strain sensing model is validated by evaluating the agreement between the modeled and measured physical variations, and a high coefficient of determination of 0.974 is obtained. In addition, based on the linear relation of the arithmetic expression of each sensing model, calibrated results for internal shear strain and stress sensing are successfully obtained. Furthermore, the measurement effect of this type of flexible sensor and its potential applications are discussed.
Highlights
R ESEARCH on elastomeric and soft robotics is extensive and significant in a wide range of fields, such as safety wearable soft sensor [1] and soft-bodied robot [2]
Because the built-in films do not perfectly follow the deformation of the substrate and there must be a stretching press occurring in the longitudinal direction under shear deformation, a stretching model was combined with the sensing model
To explain the sensing mechanism, sensing models were mathematically established based on piezoelectricity and material mechanics
Summary
R ESEARCH on elastomeric and soft robotics is extensive and significant in a wide range of fields, such as safety wearable soft sensor [1] and soft-bodied robot [2]. Few researchers have studied installation methods of a conventional transducers inside the objective material owing to challenges in architecture, manufacturing technology architecture and manufacturing technology and difficulties in guaranteeing measurement accuracy [16] Soft materials such as skin tissue are multilayer complex structures with different characteristics for each layer [17]. Li et al developed a sensor system for measuring the internal shear strain distribution for soft materials by embedding an array of polyvinylidene fluoride (PVDF) films [21], [22]. To realize the internal measurement of shear strain and shear stress distribution for soft materials, a flexible PVDF film sensor was applied and built in a bilayer substrate. Different embedded lengths of sensor elements were arranged in the depth direction at one unit position
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