• Soft Tissues
• Hyperelasticity
• FEM Analysis
• Stomach

The bases to develop a tool for the design of a robotic platform, interacting with human organs, were developed in this thesis. The case of the stomach, faced in this work, represents only an example of a broader approach.
The static point of view were completely characterized using a non-linear FEM model of the stomach. The model were developed using a data background available in literature, corcerning in-vivo and ex-corpus measures on all the organs of the abdominal cavity under laparoscopic conditions. The data were used to extrapolate a strain energy function and therefore for simuling the stomach as a hyperelastic material. The simulations were performed in ANSYS. Images taken from EPFL's visible human server were processed in SolidWorks and then used to build the stomach geometry.
The model were preliminary validated by using an experimental test.

The model allows to extrapolate a force-displacement curve of the stomach in order to simulate the interaction between the organ itself and the robotic system.
The designer will be able to assess the values of forces and torques on the robotic system using the force-displacement curve to implement a non-linear spring in the x, y, z directions, and thus performing the simulation in CosmosMotion.

A first possibility for the dynamic interaction were also tackled. We proposed to add a dashpot to the non-linear spring and thus to model the robotic system-organ interaction as a mass-spring-dashpot system.
An initial way to characterized the dashpot, relating the damping factor with the stress-relaxation behavior of the organ, were shown.
Anyhow, a proper analysis of the system should be performed by FE transient analysis verified by experimentals tests.

At the end, two different configuartion (mass-spring-dashpot) to model the interaction in CosmosMotion were shown.