Research On Multi-Quality Characteristics Robust Optimization Design Of Compliant Mechanism Considering Stress Fatigue

Compliant mechanisms is a pivotal component in the field of micro-electromechanical systems,of aeronautics and astronautics,of biological engineering,of medical apparatus and instruments and so on,because of its fabulous advantages,fatigue damage,low clamping and displacement sensitivity often occur in the actual working process,so it is necessary to make a higher requirement for the quality robustness of compliant mechanisms.This paper proposed a new method in the process of robust optimization design in compliant mechanisms,which considering stress fatigue phenomenon,to ensure the quality and reliability of the product at the design period.Take a certain type of micro gripper in a compliant mechanism as the research object,the main research could be illustrated as follows:(1)Analysis of multi-quality characteristics of micro gripper in compliant micromechanics.First,take a brief overview and analysis on micro-gripper quality in the field of characteristics of fluctuations and working principle,and sketch which material is proper combined with the actual working conditions.Second,static displacement theory is used to theoretically model and simulate the output displacement of the mechanism,using the theory of modal analysis to model and simulate mechanism's natural frequencies,stress fatigue theory is applied to model to identify the weakest point and level of the micro gripper.Finally,take mechanism's output displacement,first order natural frequency and the maximum equivalent stress of the weakest point as the three quality characteristics in the process of robust optimization design.(2)In the process of 6 sigma robust optimization design for multi-quality characteristics,spearman rank correlation coefficient is selected to analysis sensitivity of design parameters and for the sake of improving the tackling efficiency.A design of experiment is implemented based on the PB(Plackett-Burman)partial factor test design method for initial design parameters,and simulate for the three quality characteristics,select the design parameters that are more sensitive to three quality characteristics by analyzing sensitivity.Lay the foundation for robust optimization design of multi quality characteristics for follow-up.(3)Robust optimization design of 6 sigma multi quality characteristics considering stress fatigue for compliant mechanism micro gripper.First,central composite design is selected to doing an experiment for the selected parameters in order to get the relationship between design parameters and three quality characteristics,response surface method based on artificial neural network is used for this,precision test is also been considered;then a deterministic optimal design model and a 6 sigma robust optimization design model for the multi quality characteristics of the compliant mechanism micro gripper are established respectively,meanwhile,the maximum equivalent stress of the most prone to fatigue damage in mechanism is taken into consideration in the constraints of the model;and second generation non dominated sorting genetic algorithm(NSGA-II algorithm)for multi-objective optimization is adapted;finally,evaluate the two model through sigma level,and make a comparison between two model so we can tell which model has a better effect in robust optimization design.