A Basic Study on Tactile Interface Devices Modeled after Skin Structure and Sensory Characteristics of Human Hands

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We have been studying how to reproduce a tactile sensation on fingertips with reality in order to design tactile interface devices for virtual reality and tele-robotics. In this study, tactile information processing on quality of materials and movement of a grasping object was investigated based on psychophysical experiments. From experimental results, temperature change patterns of fingertip skin were very important to recognize what kind of materials contacted the skin surface. The Optimal room temperature to recognize materials was approximate 20 degrees centigrade. Next, the detection ability of the direction of strain applied to fingertips was measured. The directional differential limens for strain were 10-17 degrees as longitudinal and 7-10 degrees as transversal. There were dependency of skin locus and difference between right hand and left hand. We have designed new tactile interface devices (sensor and display) on the basis of the above experimental results. The tactile senso … More r had compliance and detectability of the 3D force direction as well as force itself. The surface of this sensor was given a rugged pattern like a fingerprint to detect a texture of objects effectively. It was proven that the tactile sensor had the similar detection ability of human fingers. The tactile display presenting sharing and pressure force and quality of materials was designed. This device used a pneumatic system to separate from the driving mechanism enabling a small and light weight display. The air pressure on each cylinder was controlling both pressure and shearing sensations by means of a three dimensional moving stage. Moreover, this display was composed of a Peltier module and a PID controller to change the temperature of skin surface dynamically. It was ascertained that the tactile display has the ability to present the shearing sensation by controlling the pressure change pattern logarithmically and the quality of materials by changing the temperature of skin surface from psychophysical experiments. In addition to the above results, other three findings can be drawn from this study : i) a new tactile stimulation method for hearing substitute, ii) influence of tactile sense of the great toe on dynamic standing balance, iii) a new force display system using metal hydride actuators for rehabilitation of a human elbow joint. Less