The effects of laterotactile information on lump localization through a teletaction system

The human finger pad is known to be highly sensitive to lateral skin deformation, which is present during the palpation of soft objects containing hard lumps. This study investigates the effects of this lateral information on the accuracy and reliability of lump localization through a teletaction system. The results are expected to benefit future telesurgical robots for remote palpation. A previously proven deformation-based tactile feedback system was modified to include laterotactile feedback using a new version of a biologically-inspired fingertip sensor (TACTIP) and a remotely-actuated electromechanical shape display. These novel devices were mounted on to a newly developed teleoperated system equipped with visual and force feedback, through which test subjects palpated a number of soft artificial tissue samples. The level of lateral feedback was altered between trials, with constant visual, force, and normal-direction tactile feedback provided throughout. The surprising results show that the addition of lateral feedback offered no benefit to the subjects´ ability to detect and localise embedded objects. Reasons for this observation are discussed. It is concluded that normal-direction tactile feedback is likely to be sufficient for lump detection even when lateral motions are made, although feedback from the subjects indicates that the addition benefited their perception of interactions with the system.