Contents I. Introduction
Robotic manipulation is a topic of significant research interest [1]. Among manipulation techniques, in-hand manipulation, which controls the position and posture of an object within the hand, is expected to improve dexterity [2]. In-hand manipulation comprises two tasks: holding the object stably in the hand and giving the object translational and/or rotational motion. To perform in-hand manipulation, several approaches have been proposed, such as using a human-like multi-fingered hand [3]–[6], implementing special mechanisms such as rollers or crawlers on the fingers [7]–[12], and leveraging external environments, e.g., floors, walls, and gravity [13]–[15]. Fig. 1(a) shows a scenario of handling an object directly with the fingertips of a multi-fingered hand according to the above first approach "using a human-like multi-fingered hand." In this case, the finger posture of the hand must be changed actively to adapt to the shape, position, and posture of the object. Furthermore, to perform continuous manipulation, repositioning of the fingers is required. Further, as shown in Fig. 1(b), we consider attaching a cloth to the hand. This approach is classified as the second approach "to implement special mechanisms". The use of flexible materials such as cloth or rope for fingers and palms improves contact stability due to their high adaptability [16]–[19]. In Fig. 1(b), adaptive deformation of the cloth allows the object on the cloth to be held stably. Furthermore, the displacement of the fingertip changes the shape of the cloth and generates rolling and slipping of the object. In this study, we discuss an in-hand manipulation method using cloth.
