Design of a 1.0mm Multifunctional Forceps-Scissors Instrument for Minimally Invasive Surgery

2006 ◽  
Author(s):  
Milton E. Aguirre ◽  
Mary Frecker
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Minimally Invasive Surgery ◽  
Minimally Invasive ◽  
Invasive Surgery ◽  
Compliant Mechanism ◽  
Rectangular Cross Section ◽  
Geometric Constraints ◽  
Element Analysis ◽  
Performance Space

A multifunctional forceps-scissors instrument is designed for minimally invasive surgery. The device is a compliant mechanism capable of both grasping and cutting. The focus of the paper is on the design optimization and a detailed finite element analysis of the compliant mechanism. One-half of the symmetric compliant mechanism is modeled as a cantilever beam of rectangular cross-section undergoing large deformation. The optimization problem is solved graphically where all feasible designs (i.e., those that satisfy the stress and geometric constraints) are displayed on performance space plots. Using this method it is easy to visualize the performance space and to select a suitable design; however, it is found that it is not possible to simultaneously maximize free deflection and blocked force in the forceps or scissors modes. A detailed finite element analysis was conducted using ANSYS to model the multiple loading conditions. A prototype instrument, fabricated from stainless steel using wire EDM with the precision of +/- 2 μm, has been tested for comparison of actual and predicted results.

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

2008 ◽  
Author(s):  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Gabriele Vassura ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanism ◽  
Structural Parameters ◽  
Dielectric Elastomer ◽  
Constant Force ◽  
Element Analysis ◽  
Body Model ◽  
Rigid Body Model ◽  
Supporting Frame

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

Bistable Compliant Four-Bar Mechanisms With a Single Torsional Spring

2006 ◽  
Author(s):  
Adarsh Mavanthoor ◽  
Ashok Midha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Stored Energy ◽  
Element Analysis ◽  
Bistable Behavior ◽  
Torsional Spring ◽  
Bistable Mechanism

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements.

Size and Shape Optimization of a 1.0mm Multifunctional Forceps-Scissors Instrument for Minimally Invasive Surgery

2007 ◽  
Author(s):  
Milton E. Aguirre ◽  
Mary Frecker
Keyword(s):  
Minimally Invasive Surgery ◽  
Minimally Invasive ◽  
Shape Optimization ◽  
Invasive Surgery ◽  
Optimization Problems ◽  
Compliant Mechanism ◽  
Linear Deformation ◽  
Cross Sectional ◽  
Size And Shape ◽  
Grasping Forces

A size and shape optimization routine is developed and implemented on a 1 mm multifunctional instrument for minimally invasive surgery. The instrument is a compliant mechanism, without hinges, capable of both grasping and cutting. Multifunctional instruments have proven to be beneficial in the operating room because of their ability to perform multiple tasks, thereby decreasing the total number of instrument exchanges in a single procedure. In addition, with fewer exchanges the risk of inadvertent tissue trauma as well as overall surgical time and costs are reduced. The focus of the paper is to investigate the performance effects of allowing the cross-sectional area along the length of the device to vary. This is accomplished by defining various cross-sectional segments along the device in terms of parametric variables (Wi) and optimizing the dimensions to provide a sufficient forceps jaw opening while maintaining adequate cutting and grasping forces. Two optimization problems are considered. First, all parametric segments are set equal to one another permitting all cross-sections to vary uniformly and achieving size optimization. Second, each segment is defined as a separate design variable to allow segments to vary independently and thereby achieving shape optimization. Due to the device’s symmetry, one-half of the mechanism is modeled as a cantilever beam undergoing large deformation. ANSYS’ optimization module is employed using the first order method because it is capable of performing optimization considering non-linear deformation and multiple loading conditions. Finally, prototypes are fabricated using wire EDM and prototype evaluations are conducted to compare size versus shape optimization, and to validate ANSYS as the solution method.

Three-Dimensional Finite Element Analysis of Qingyi River Aqueduct during Operation Period

2014 ◽  
Vol 556-562 ◽  
pp. 679-682
Author(s):  
Yan Yan Zhang ◽  
Cai Ying Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Engineering Practice ◽  
Good Precision ◽  
Operation Condition ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, finite element model of the Qingyi River rectangular section reinforced concrete aqueduct is set up by using three-dimensional finite element analysis software ANSYS. Considering the conventional static load, the seismic loads which use quasi-static method, and considering five combinations of operation condition of aqueduct in operation process, the structure stress and displacement rules of aqueduct are obtained in the different conditions. The results show that the rectangular cross-section aqueduct in the water level under the action of the full tank, the vertical displacement of the aqueduct body structure is nearly doubled than the empty slot, indicating the water load have a significant impact on the aqueduct. The calculated results has a good precision, can meet the needs of practical engineering, can provide a reference basis for the design of thin-walled rectangular aqueduct and the theoretical basis for engineering practice and guidance recommendations.

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