三次元力覚・触覚呈示装置は，次世代の三次元触覚ディスプレイとして重要である．この装置の特徴は，呈示する反力の大きさ・方向・位置を独立に制御可能な点で，特に2つ以上の反力ベクトルの補間による平滑化は，少ない情報量・計算量で滑らかな形状を呈示するために特に有用性が高く，これに関する人間の特性の解明が必要である．本論文では，1点接触型・3自由度の力覚呈示装置PHANToMを用い，平面の中央が幅2w，高さhのなだらかな山型に盛り上がった形状を，反力の方向を固定し変位情報のみを呈示するという条件下で，w，h，および刺激形状の硬さsを変化させ，ヒトが平面であると判断するパラメータを特定し，その絶対閾を極限法により求めた．その結果，sが0.25?0.5 N/mm，wが20?40 mmの範囲では形状高さが絶対閾hat= 0.034 ・w + 0.022以下である場合に，また wが5?20mmの範囲では形状の高さhにstiffnessを乗じた値が0.18N以下であれば，ヒトは平面と判断するとしてよいことが分かった．Haptic/force feedback device is an important type of three- dimensional haptic display whose application fields include computer aided design and surgical simulation. With such a device, three elements of feedback force (magnitude, direction, and displacement) can be controlled independently to give haptic illusion as well as natural haptic simulation of virtual objects. To date, however, shape perception factors have not been well studied. This paper presents experiments on the effect of displacement in plane shape perception with a point contact type force feedback device. The subjects changed the height h of smooth mountainous stimulus shape (width 2w and stiffness s) to determine parameters and their thresholds for the shape perceived as flat. The feedback force direction was fixed upward, the same as a horizontal plane, to see the effect of displacement. A shape is felt to be flat (1) if its height is smaller than absolute threshold value hat = 0.034 ・w + 0.022 (where s is 0.25--0.5N/mm and w is 20--40mm), or (2) if force for its height h, calculated by h ・s, is smaller than 0.18N (where s is 0.25--0.5N/mm and w is 5--20mm).
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