Print Email Facebook Twitter Steerability and Stiffness: Applied in minimally invasive instruments Title Steerability and Stiffness: Applied in minimally invasive instruments Author Pessers, R.A.W. Contributor Dankelman, J. (mentor) Faculty Mechanical, Maritime and Materials Engineering Department BioMechanical Engineering Programme BMD Date 2011-06-30 Abstract This thesis discusses the design of a new steerable tip for a laparoscopic instrument. A new tip design is required since current steerable tip designs have problems with the bending stiffness and the lifespan of the cables. Underaction is a main cause of the low tip stiffness. Since one of the design requirements is that the tip needs to be able to rotate in two perpendicular planes, the tip has two rotational degrees of freedom (DOF). The simplest way to fully actuate the tip and to rotate each DOF over 90 degrees in a clockwise (CW) and counter clockwise (CCW) direction is by using two cables for each DOF, resulting in a total of four cables in the tip. A limiting factor of the lifespan of the tip is the fatigue of the cables. The fatigue is the result of the cables being forced to make a sharp bend during a rotation of the tip. To reduce the fatigue of the cables, the cables therefore need to be guided and to make a bend as large as possible in a g5 mm tip. As a prove of concept, two prototypes have been produced. From these prototypes it can be concluded that each DOF in the tip is able to rotate up to an angle of 90 degrees in CW and CCW direction. It can also be concluded that the tip is fully actuated. The bending stiffness of the tip therefore only depends on the stiffness of the cables and the rigid bodies of the tip. Since the cables and rigid bodies will be produced from steel, the bending stiffness of the tip will be high. Considering the cables to have a diameter of 0.5 mm, the cables will be guided over a guiding with a radius of 3.48 mm. Compared to the EndoWrist, where the radius of the pulley with similar cables would be 2 mm, the radius is almost 1.75 as large. The result is that the lifespan of the cables in the new design will be superior. Subject laparoscoysteerable instrumentstiffness To reference this document use: http://resolver.tudelft.nl/uuid:e8a29db4-7f0d-4ab2-aff6-a70ffee707f3 Embargo date 2015-06-28 Part of collection Student theses Document type master thesis Rights (c) 2011 Pessers, R.A.W. Files PDF Master_thesis_Rob_Pessers.pdf 2.96 MB Close viewer /islandora/object/uuid:e8a29db4-7f0d-4ab2-aff6-a70ffee707f3/datastream/OBJ/view