Design and Characterization of a Fabric-based Softness Display

To enable a realistic tactile interaction with remote or virtual objects, softness information represents a fundamental property to be rendered via haptic devices. What is challenging is to reduce the complexity of such an information as it arises from contact mechanics and to find suitable simplifications that can lead an effective development of softness displays. A possible approach is to surrogate detailed tactile cues with information on the rate of spread of the contact area between the object and the finger as the contact force increases, i.e. force/area relation. This paradigm is called contact area spread rate. In this paper we discuss how such a paradigm has inspired the design of a tactile device (hereinafter referred to as Fabric Yielding Display, FYD-2), which exploits the elasticity of a fabric to mimic different levels of stiffness, while the contact area on the finger indenting the fabric is measured. In this manner, the FYD-2 can be controlled to reproduce force-area characteristics. In this work, we describe the FYD-2 architecture and report a psychophysical characterization. FYD-2 is shown to be able to accurately reproduce force-area curves of typical objects and to enable a reliable softness discrimination in human users.