Application of a Redundant Haptic Interface in Enhancing Soft-Tissue Stiffness Discrimination

Haptic-enabled teleoperated surgical systems have the potential to enhance the accuracy and performance of surgical interventions. The user interface of such a system can provide haptic feedback to the surgeon to more intuitively perform surgical tasks. In this letter, we study the added benefits of redundant manipulators as haptic interfaces for teleoperated surgical systems. First, we introduce the intrinsic benefits of employing a redundant haptic interface, namely, reduced apparent inertia and increased manipulability (one result of which is reduced friction forces). Next, we demonstrate that the haptic interface redundancy can further reduce its apparent inertia and friction via appropriately manipulating the extra degrees of freedom of the interface. This will consequently enhance the haptic feedback resolution (sensitivity) for the user. Finally, a psychophysical experiment is performed to validate the improved force perception for the user in a virtual soft-tissue palpation task. We conduct a set of perceptual experiments to evaluate how a redundant and non-redundant user interface affects the perception of the virtual stiffness. Experimental results demonstrate that the redundancy in the haptic user interface helps to enhance tissue stiffness discrimination ability of the user by reducing the distortions caused by the kinematics and dynamics of the user interface.