University of Twente Student Theses


Reducing apparent inertia in a tool for minimally invasive surgery

Plaisier, Thomas (2017) Reducing apparent inertia in a tool for minimally invasive surgery.

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Abstract:The Minimally Invasive Surgery Tool (MIST) developed by the Universitair Medisch Centrum Utrecht (UMCU) seeks to improve surgeon working conditions and can also help to improve the skills of surgeons in training. The current design, which is passive and purely mechanical, has several drawbacks: a relatively high and anisotropic inertia, and imperfect passive balancing. In this thesis, an active system is added to the MIST to improve the handling by reducing the apparent inertia. This is expected to increase movement accuracy and speed, and lead to a better intuitive feel for the dynamics of the surgical tool. The developed system also allows for implementing solutions for active gravity compensation, and configuration dependent manipulation of the system dynamics. In this research a form of inertia compensation is developed that uses a dynamic model of the MIST, and an Inertial Measurement Unit (IMU) instead of a force sensor. By predicting the accelerations that results from system dynamics and controller output, the operator contribution can be isolated from the measured acceleration and selectively amplified. This amplification allows for a reduction of the apparent inertia. Results from simulations and stability analyses predict that the apparent inertia can be reduced by approximately 80%, even for mismatches of 25% between the estimated and physical system dynamics. Data obtained with a force sensor shows that for a predicted apparent inertia reduction of 33%, an average reduction of 20% is achieved in practice; the difference is likely due to modeling errors.
Item Type:Essay (Master)
Universitair Medisch Centrum Utrecht, Utrecht, Nederland
Faculty:TNW: Science and Technology
Subject:52 mechanical engineering
Programme:Biomedical Engineering MSc (66226)
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