This paper reviews studies on the tactile dimensionality of physical properties of materials in order to determine a common structure for these dimensions. Based on the commonality found in a number of studies and known mechanisms for the perception of physical properties of textures, we conclude that tactile textures are composed of three prominent psychophysical dimensions that are perceived as roughness/smoothness, hardness/softness, and coldness/warmness. The roughness dimension may be divided into two dimensions: macro and fine roughness. Furthermore, it is reasonable to consider that a friction dimension that is related to the perception of moistness/dryness and stickiness/slipperiness exists. Thus, the five potential dimensions of tactile perception are macro and fine roughness, warmness/coldness, hardness/softness, and friction (moistness/dryness, stickiness/slipperiness). We also summarize methods such as psychological experiments and mathematical approaches for structuring tactile dimensions and their limitations.

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The goal of our study is realization of static friction sensation using a piece of artificial finger skin for robot hand manipulation. In order to realize the sensation, we recall the importance of incipient slip detection. First, artiJicialJinger skin is designed which is mimicked to have characteristics similar to that of a human finger with respect to the shape and a part of the sensing functions which such enable the incipient slip detection: Thefinger skin has ridges on the surface in each of which a pair of ar@cia1 FA1 receptors are embedded. The design process of art$-cialfinger skin is also shown that includes three phases. Design phase #I is to design the characteristics of a FA1 receptor as the transducer of which, we choose PVDF film sheets which have a dynamic stress rate characteristic. Design phase #2 involves determination of the shape and size of artijkialfinger skin, and the location of the transducers in a ridge. We analyze the stress in the finger skin when incipient slip occurs at the surface. The signal from transducer is analyzed what the best situation of the position of transducer and the using information of transducer at the future process. Design phase #3 is to manufacture artijicial finger skin. Experimental result that incipient slip occurs at the surface of artijicial finger skin reveal that the differential output voltage signal from a pair of artijicial FA1 receptors embedded in a ridge captures not only low-frequency vibration to generate a predictive signal which warns incipient slip of the ridge, but also high frequency vibratory signal which indicates slip of the ridge. In order to judge automatically that incipient slip occurs we use multi-layered ANN. The result to judge incipient slip use ANN shows that the system is robust to noise and can detect the incipient slip.

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Wearable robots have finally reached a point at which they can be put to more practical use. However, methods for assessing their safety have yet to be properly established. Furthermore, for ethical reasons, such assessments must be conducted without exposing the human user to unnecessary danger. Therefore, in this study, a lower-leg dummy for the safety assessment of a wearable robot was developed to evaluate the effects of a misaligned knee joint.

Abstract:To effectively design tactile textures of product surfaces, it is essential to specify the semantically multilayered and multidimensional structure of human perceptual, emotional, and preferential expressions pertaining to touching materials. We implemented a method to identify individual differences in the structure of these expressions, based on subjective reports of the mutual impacts among 29 adjective dyads used to describe tactile experiences of material samples. Results showed that the 11 university students who responded to 46 types of flat materials were clustered into three statistically different groups. The structures were largely composed of three layers of expressions: psychophysical (bottom), emotional or material attributes (middle), and preferential (top). All groups selected the same adjective dyads encompassed in the bottom layer, relating to percepts of physical quantities, which indicates the similarity of psychophysical percepts among the participants; however, the middle and top layers significantly differed across individuals. These results indicate that under the tested conditions, there are individual differences in the semantic structures of emotional and preferential experiences; however, such differences in psychophysical expressions are relatively minor.