A projected virtual hand interface, which visually extends the arms of users using projection images, enables wheelchair users to reach unreachable objects; however, its projection area is usually smaller than the reaching area for its users. In our previous research, we developed a wheelchair system with a projected virtual hand system in which users can move the projected area via finger movements on a touch panel. However, it requires some time to move the projected area to the desired position. To address this problem, we propose a wheelchair system enhanced with a projected virtual hand that allows controlling a projection area using a user's head orientation. The proposed system measures the current user's head orientation and distance between a user and a projection surface. Then, it adapts the suitable pan and tilt of the projector by considering its positional relationship with the projection plane. As users can operate the projection area simply by turning their head, this operation can be executed simultaneously with operating a virtual hand using their hands. We propose a control model for projector rotation according to the user's head orientation. We implemented a prototype based on the model and confirmed the system's latency. The usability study revealed that the proposed method enables users to perform pointing tasks in a shorter time compared with the existing method. Moreover, it has acceptable interface usability. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
