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Title:Alternative design optimization formulations – developing and comparing for a vibration damping example
Author(s):Luan, Siyao
Advisor(s):Thurston, Deborah L.
Department / Program:Industrial&Enterprise Sys Eng
Discipline:Industrial Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Optimization formulation
Design guidelines
Abstract:Developing mathematical formulations for design problems requires determining an objective function to compare design alternatives, a set of design features and options to be included for consideration, and a predictive model that reflect any unavoidable cause and effect relationships that are relevant. There are no formal principles guiding the formulation process, and heuristics prevail. There are some instances when the level of effort required to formulate the problem and solve the problem are excessive, not worth the improvement that might be realized in the overall design objective. In other words, a hypothetically “perfect” design problem formulation that takes all possible factors into account might be so difficult to fully compose and solve that it is not worth the effort. This thesis presents a set of guidelines for formulating design problems that seeks a middle ground. The method presented defines three different tasks in the formulation process: comparison metrics, predictive model and design representation. Each task offers opportunities for the practitioner to balance the expected quality of the solution with the level of effort and time required to reach that solution. This thesis demonstrates how using the guidelines can help create alternative formulations for the same design problem, and then how the resulting solutions can be evaluated and compared. Using a vibration absorber design example, the guidelines are enumerated, explained, and used to compose six alternative optimization formulations of the problem. These alternatives formulations vary in objective functions, decision variables, and some other design formulation practices. The overall goal is to maximize surface finish quality of a machined component processed on a platform to which the vibration absorber is attached. Vibrations of the platform can have a detrimental effect on surface quality. The goal of the vibration absorber system is to minimize these detrimental effects. The six alternative optimization formulations are subsequently solved, and their scores reflecting their complexity, computational time and solution quality are quantified and compared. The results illustrate the unavoidable tradeoffs among these three attributes. The best formulation depends on the set of tradeoffs that are best in that situation, given the decision maker’s risk attitude and preference.
Issue Date:2017-07-20
Rights Information:Copyright 2017 Siyao Luan
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08

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