This paper explains the PMR-2R (prototype mobile robot -2 revised), the mobile robot with the eyeball expression as the preliminary-announcement and display of the robot's following motion. Firstly, we indicate the importance of the preliminary-announcement and display function of the mobile robot's following motion for the informational affinity between human being and a robot, with explaining the conventional methods and the related works. We show the proposed four methods which are categorized into two types: one type which indicates a state just after the moment and the other type which displays from the present to some future time continuously. Then we introduce the PMR-2R, which has the omni-directional display, the magicball, on which the eyeball expresses the robot's following direction of motion and the speed of motion at the same time. From the evaluation experiment, we confirmed the efficiency of the eyeball expression to transfer the information. We also obtained the announcement at around one or two second before the actual motion may be appropriate. And finally we compare the four types of eyeball expression: the one-eyeball type, the two-eyeball type, the will-o'-the-wisp type, and the armor-helmet type. From the evaluation experiment, we have declared the importance to make the robot's front more intelligible especially to announce the robot's direction of motion.
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