Method for Optimization of a Nonlinear Static Balance Mechanism With Application to Ophthalmic Surgical Forceps

Abstract

A new method for optimizing the dimensions of a nonlinear static balance mechanism has been created. A rigid link slider-crank mechanism with a nonlinear spring is designed to balance a compliant mechanism. This is accomplished by determining the potential energy of the compliant mechanism using finite element analysis and then optimizing the dimensions of the static balance mechanism to balance the potential energy stored in the compliant forceps. The optimization is performed using a sequential quadratic programming algorithm in Matlab’s optimization toolbox. It is seen that using higher order nonlinear springs results in a system that is better statically balanced. The mechanism that is statically balanced is a compliant forceps that has previously been designed for use in ophthalmic surgery. The compliant forceps stores energy when it creates motion, which then creates neutral positions of the mechanism with minimum potential energy. This situation is often unwanted in surgical situations. This paper uses the compliant forceps as an example of how to optimize the dimensions of a nonlinear static balance mechanism.