Haptic device using flexible sheet by tension and touch area control

We have already developed a haptic device using flexible sheet such as rubber. This device varies sheet compliance by controlling tension applied to the sheet: stretched sheet feels hard, and loose sheet feels soft. Hence a user can feel different compliance of virtual objects when he pushes the sheet directly with his finger. In the present study we propose a new haptic device which can move, expand and narrow the touch area on the sheet in addition to tension control. This device has two movable bars slightly touching the back of the tensioned sheet. A user touches and pushes the area between the bars on the sheet. Because the bars work as supporting struts, only this area is depressed. Controlling the distance between the bars varies the size of the touch area, thus varying sheet compliance: wide area makes the sheet soft, and narrow area makes the sheet hard. Keeping the size of the touch area constant generates the same sheet compliance, even if the touch area moves anywhere. Owing to the effects of variable tension and touch area, the new device can generate more variety of compliance than the previous one. A prototype device using a silicon rubber sheet is developed. Four servo motors move two bars through parallel link mechanisms under the tensioned sheet. The force-indentation curves for some sets of different tension and touch area are measured. The results show that the developed device can generate wide range of sheet compliance.