Pneumatic Concave Deformable Device and Finger Deformation-Based Evaluation for Hardness Perception

Modifying and controlling hardness on the same surface are very useful for digitizing realistic and intuitive interactions for many use cases. We propose a novel haptic device with a dual-layered air structure to control both the reaction force and the three-dimensional (3-D) concave deformation that provides realistic hardness and softness. To physically evaluate this device and other objects with various hardness, a measurement system is set up to acquire both kinesthetic and cutaneous profiles simultaneously. In particular, we propose a cutaneous profile based on finger deformation when pushing objects with various hardnesses. We show that our device has the potential to present hardness over a high dynamic range from a sponge specimen (stiffness: 0.544 N/mm) to a hard silicone rubber (stiffness: 5.304 N/mm) with evaluation using the aforementioned measurement system. We also conduct a psychophysical experiment to confirm that our device can change the perception of hardness.