Reaction force and surface deformation estimation based on heuristic tissue models

Abstract

Abstract-In many of the advanced surgical robotic systems, soft tissue mechanics and tool-tissue interaction modeling play an important role in achieving optimal control, relying on model-based control methods. This approach allows one to address crucial issues during teleoperation, such as time-delay, stability or state observation. This paper presents a novel approach for modeling the behavior of soft tissue during surgical interventions, employing the widely-used concept of rheological models. The nonlinear Wiecher model is used for reaction force estimation during tissue indentation, tested on beef liver samples for acquiring mechanical parameters from experimental data. Curve fitting methods have been used in both stress relaxation and constant indentation speed compression phases. Reaction forces are estimated using the proposed model, followed by verification tests on ex-vivo beef liver samples. The results of this research showed that the proposed novel rheological soft tissue model is capable of estimating the reaction forces acting on the tool, if the shape of the deformed tissue is known in time.