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Model Based Control of a Laparoscopic Instrument for Safe and Effective Grasping of Spleen Tissue

Abdi, Elahe | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42809 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam; Durali, Mohammad
  7. Abstract:
  8. In the present dissertation model based grasping of soft tissue with the laparoscopic gripper, tissue deformation under the applied load and control of the tissue-instrument interaction have been studied. As the first step a cantilevered beam under bending and tension has been modeled statically and dynamically using the meshless EFG based method. Results show that an increase in the number of nodes at the displacement boundary and the area of force insertion improves the accuracy of the predicted displacement in the model compared to the analytical solution. In the second step the model is developed for a hemisphere under vertical and lateral compression. Comparison of the deformation of the cantilevered beam model with that of the analytical solution, and the deformation of the hemisphere model with that of the finite element model shows a maximum error of 10%. As the last step in modeling, interaction of spleen with laparoscopic gripper is studied. Spleen viscoelastic properties are obtained by performing tests on 3 sheep spleens each with 3 samples. The accuracy of the model deformation in interaction with a two jawed grasper is investigated by an experimental test on a cylindrical sample of silicon. The resultant deformation is compared with that of the meshless model showing an error of 4%. Then the grasping of spleen with a two jawed laparoscopic gripper and slippage of the tissue under insufficient compression is modeled. Finally a Proportional-Derivative controller is used to improve the tissue-instrument interaction. Results show that the appropriate constant parameter for the controller depends on the Young’s modulus of the tissue. This dependency decreases in a specific range of Young’s modulus and increases out of that range
  9. Keywords:
  10. Viscoelastic Behavior ; Tool-Tissue Interaction ; Force Control ; Meshless Method ; Spleen Soft Tissue ; Modeling

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