This paper addresses the influence of friction on the haptic transparency within soft tissue telemanipulation. In contrast to remote handling of hard environments, the level of the friction forces is thereby within the same order of magnitude as the interaction forces. Therefore, these friction forces may alter performance and haptic transparency considerably. Control schemes showing nice results within simulations using linear models, with frictionless virtual manipulators in a virtual environment, or where friction forces are negligible compared to the interaction forces, show totally different results when implemented on a real telemanipulator setup with a realistic friction level and in contact with a soft environment. In this paper, friction is added to the linear models of the master and slave actuators as an input force disturbance. The influence of these disturbances on haptic transparency then is investigated analytically for the most widely used teleoperator schemes. Thereby, effectiveness of using force sensors on master and/or slave side is evaluated, and validated through experiments on a one-dimensional test setup.

This paper describes an advanced tool guiding system for robot assisted surgery. It is offering two additional local degrees of freedom to a standard robotic tool guiding system like of the Zeus robotic surgery system. The tool guide is basically a tube that guides the inserted surgical instrument to the desired location. By adding two bending degrees of freedom at the tip, the developed system largely increases the maneuverability of the instrument. It consists of a micromachined superelastic tube driven by a conventional cable system. Main issue was the design of a flexible hinge system in superelastic NiTi that offers the desired bending angles (at least 90 degrees in both directions) and that is compatible with the material limits for long-time cycling. Based on extended FE calculations and experimental measurements the second-generation design offers 90 degrees bending in both directions. The improvement over previous devices is the combination of two degrees of freedom with a small diameter of only 5 mm. An additional advantage is the tool channel, which enables the use of different instruments with this single device.