摘要
常規(guī)優(yōu)化由于不考慮設(shè)計變量的波動，這就使常規(guī)優(yōu)化解處在可行域的邊緣上，當(dāng)設(shè)計變量發(fā)生波動后，常規(guī)優(yōu)化解將會偏離可行域從而變?yōu)椴豢尚薪狻ｔ敯粼O(shè)計由于在設(shè)計之初就考慮到了變量的波動性，它對目標(biāo)函數(shù)和約束函數(shù)均有魯棒性的要求，因而魯棒設(shè)計解較常規(guī)優(yōu)化解具有更好的魯棒性。
現(xiàn)代魯棒設(shè)計方法是在田口方法的基礎(chǔ)上發(fā)展而來的。本文主要介紹了基于容差模型法的魯棒設(shè)計，最小靈敏度法和靈敏度分析法。容差模型法考慮到設(shè)計變量的變差會引起目標(biāo)函數(shù)和約束條件的變差，要在新的可行域內(nèi)找到魯棒解，該法適用于模型線性程度不高以及變差較小的情況；最小靈敏度法和靈敏度分析法是不考慮設(shè)計變量容差的方法。
本文將理論和實際相結(jié)合，所做主要工作如下：
（1）利用容差模型法對一艘8700DWT散貨船中橫剖面結(jié)構(gòu)進(jìn)行了魯棒優(yōu)化設(shè)計。以板厚為設(shè)計變量，整個中橫剖面面積最小為目標(biāo)函數(shù)，約束函數(shù)采用最壞情況容差進(jìn)行處理。魯棒設(shè)計結(jié)果較規(guī)范設(shè)計有更好的魯棒性。
（2）最小靈敏度法不考慮性能參數(shù)的余度，因此本文在最小靈敏度法的基礎(chǔ)上提出了一種最小波動法。本文所提出的最小波動法將最小靈敏度和性能參數(shù)的余度相結(jié)合，對性能參數(shù)的波動進(jìn)行量化。通過對4萬噸散貨船進(jìn)行中橫剖面結(jié)構(gòu)結(jié)構(gòu)的魯棒優(yōu)化設(shè)計，證明本文所提出的方法較最小靈敏度法有更好的設(shè)計結(jié)果。同時本文所提出的方法也可以推廣到其它的魯棒優(yōu)化設(shè)計中。
（3）在MSC.Patran環(huán)境中建立27.6m雙體船全船有限元模型，通過施加邊界條件和載荷，經(jīng)過MSC.Nastran進(jìn)行計算得出結(jié)果。對結(jié)果進(jìn)行分析后，該雙體船的結(jié)構(gòu)需要改進(jìn)。然后借助有限元技術(shù)，利用結(jié)構(gòu)分析軟件MSC.Patran/Nastran求取27.6m雙體船質(zhì)量、板單元合成應(yīng)力、梁單元應(yīng)力、橫向剛度以及扭轉(zhuǎn)剛度對板厚的靈敏度。通過綜合分析比較，得出了優(yōu)化方案，并取得了較好的優(yōu)化結(jié)果，說明靈敏度分析用在船舶結(jié)構(gòu)優(yōu)化設(shè)計可以取得較好的結(jié)果。本文也可作為其它船型靈敏度分析優(yōu)化設(shè)計時的參考。


關(guān)鍵詞：結(jié)構(gòu)魯棒設(shè)計 容差模型 最小靈敏度法 靈敏度分析
























Abstract
Conventional optimal design does not take the variations of variables into account, which makes conventional optimal solution in the edge of the feasible region. When the design variables fluctuate, the conventional optimal solution will deviate from the feasible region into unfeasible solution. While robust design takes the variations of variables into account early in the design, and it makes objective function and constraints are robust, therefore robust design optimization solution has better robustness than the conventional solution.
Modern robust design method is based on the Taguchi method and evolved. This paper mainly describes robust method based on the tolerance model, the minimum sensitivity method and sensitivity analysis. Tolerance model method taking into account the variation of design variables which will cause the objective function and constraints have variation, to find a new robust solution in the new feasible region.This method applies to the linear model is not high and the variation is relatively small; minimum sensitivity method and sensitivity analysis are the methods which don’t considere design variable tolerance.
This paper combined theory and practice, and the major work done is as follows:
(1) Use of tolerance model method for 8700DWT bulk carrier’s midship cross-sectional structure in robust optimal design. Plate thickness as design variables, the minimum cross-sectional area as objective function, and constraint functions using the worst-case tolerance for processing. The result is more robust than specification design.
(2)It doesn’t consider the redundancy of the performance parameters, so the method of minimum variation is proposed in this paper. The minimum variation being proposed in this paper cooperates the method of minimum sensitivity and the redundancy of the performance parameters, which will quantify the variations of the performance parameters. By the robust optimization of the midship section structure of 40,000DWT bulk carrier, finding that the method proposed in this paper has better result than the minimum sensitivity. And the method proposed in this paper can also be extended to other robust optimization designs.
(3) In MSC.Patran environment 27.6m catamaran finite element model was build, through the imposition of boundary conditions and load, got the result by the calculation of MSC.Nastran. After analyzing the results, some catamaran's structure needs to be improved. In this paper by using finite element techniques and structural analysis software MSC.Patran/Nastran, got the sensitivity to sheet thickness of mass, the Von.Mises of shell element, the Von.Mises of beam element, lateral stiffness and torsional stiffness. Through comprehensive analysis and comparison, got the optimization program, and achieved good optimization results, indicating the sensitivity analysis used in ship structural optimization can get better result. This paper can also be used as a reference for other ships’ sensitivity analysis and optimization.

Keywords: structure robust design, tolerance model, minimum sensitivity, sensitivity analysis


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