Object Elasticity Research Articles

剛性可変機構を有する5指ロボットハンドの開発

This study deals with a robot hand based on the original finger mechanism consisting of a planetary gear system and serially connected four bar linkages. It also has a mechanism for adjusting stiffness of fingers (VSM: Variable Stiffness Mechanism), which allows to give passive gripping force to a gripping object according to the object's elasticity. The mechanism is merely driven by mechanical elements without sensory feedback from tactile or force sensors attached to fingertip or sole. The total number of motors for driving the robot hand is six, all of which are equipped in the palm. Rotation angle of motor is detected by optical encoder equipped to each motor. The robot hand achieves soft and adaptive gripping action due to VSM that adjusts the joint stiffness of the fingers by changing tension of the spring attached to the planetary gear system equipped in every finger except the thumb. Driving tests show that it achieves typical gripping and pinching motions of a human hand in daily life without any sensory feedback and also show that the VSM works effectively.

Perception of elasticity in the kinetic illusory object with phase differences in inducer motion.

BackgroundIt is known that subjective contours are perceived even when a figure involves motion. However, whether this includes the perception of rigidity or deformation of an illusory surface remains unknown. In particular, since most visual stimuli used in previous studies were generated in order to induce illusory rigid objects, the potential perception of material properties such as rigidity or elasticity in these illusory surfaces has not been examined. Here, we elucidate whether the magnitude of phase difference in oscillation influences the visual impressions of an object's elasticity (Experiment 1) and identify whether such elasticity perceptions are accompanied by the shape of the subjective contours, which can be assumed to be strongly correlated with the perception of rigidity (Experiment 2).Methodology/Principal FindingsIn Experiment 1, the phase differences in the oscillating motion of inducers were controlled to investigate whether they influenced the visual impression of an illusory object's elasticity. The results demonstrated that the impression of the elasticity of an illusory surface with subjective contours was systematically flipped with the degree of phase difference. In Experiment 2, we examined whether the subjective contours of a perceived object appeared linear or curved using multi-dimensional scaling analysis. The results indicated that the contours of a moving illusory object were perceived as more curved than linear in all phase-difference conditions.Conclusions/SignificanceThese findings suggest that the phase difference in an object's motion is a significant factor in the material perception of motion-related elasticity.