Tactile sensing system with wrinkle's morphological change: Modeling

Previously, we have developed an active tactile sensing system that can select sensing modalities based on specific sensing tasks by changing its morphology, named Wrin'Tac. This tactile sensing system is constructed by an integration of actuation (pneumatic actuator) and sensing elements (strain gauge) inside a thin, multi-layered substrate. Under pressurization, the morphology of the substrate surface changes with the appearances of wrinkle. As a result, this device can detect both static load under indentation and dynamic sliding action by using only a single type of sensing element (strain gauge). In this paper, we present a computational model for estimation of the wrinkle's morphology and prediction of output of embedded sensing elements. The shape of the wrinkle and the posture of the sensing element are evaluated by calculating the height of the wrinkle. The wrinkle's mechanical change is assessed by ascertaining the stiffness of the wrinkle under vertical indentation by a spherical indenter. The output voltages of the sensor are calculated by the proposed model and the experimental values have an error of less than 10%, which validates the accuracy of the proposed model. We also pointed out the role of the wrinkle's morphology to the sensor's sensitivity, implying that this sensing system may select suitable sensitivity for specific sensation tasks. This work is expected to pave a way for assessing the role of morphological change to tactile sensation, and development of soft active tactile sensing systems.