Wearable Artificial Fingers with Skin Vibration and Multi-Axis Force Sensors.

Tactile sensations are based on stimulation elicited on the skin through mechanical interactions between the skin and an object. Hence, it is important to consider skin properties as well as objects. We aim to develop wearable artificial fingers for quantitative evaluations reflecting individual differences in human fingers. In a previous study, a wearable skin vibration sensor was attached to artificial fingers and it was demonstrated that the skin vibrations differed according to the dimension of surface ridge and the artificial finger is useful for roughness evaluation. This paper improved the artificial finger to measure the contact force and friction in addition to the skin vibration. A small three-axis force sensor was embedded into the base of the finger, and normal and friction forces were estimated via a multi-regression method. Furthermore, artificial fingers with different hardness were prepared and six different textures were used to investigate tactile evaluation. Experimental results showed that the artificial fingers could measure normal and friction forces along with the skin vibration and were useful to evaluate textures. Resulting distributions of the vibration intensity and friction coefficient were different for the soft and hard artificial fingers, indicating the complex influence of skin properties on tactile sensations.