Sensory substitution using 3-degree-of-freedom tangential and normal skin deformation feedback

During manual interactions, we experience both kinesthetic forces and tactile sensations. Friction and normal force between the fingerpads and the tool/interaction surfaces cause shear and normal deformation of the skin. Capitalizing on this observation, we designed a 3-degree-of-freedom (DoF) tactile device that is grasped by a user and can render both tangential skin stretch and normal deformation on the skin of the user´s fingerpads. Tactile feedback from the device is delivered in a manner consistent with natural tactile cues from manual interaction. An experiment assessed the accuracy with which users can locate the center of a contoured hole on a virtual surface. The task was completed under four conditions: the cases of skin deformation and force feedback, with both 3- and 1-DoF feedback in each case. With 3-DoF feedback, users located the hole faster and more accurately than with 1-DoF feedback, for both force and skin deformation feedback. These results indicated that users were able to interpret the additional DoF cues provided by our 3-DoF tactile device to improve task performance.