Showing 6 results for Multi-Objective Genetic Algorithm
Ehsan Maani, Amir Reza Kosari, Mehdi Fakoor,
Volume 14, Issue 5 (8-2014)
Abstract
In this paper, multi-objective Genetic Algorithm has been employed to find the communications satellite optimal transfer trajectory from geosynchronous transfer orbit (GTO) to geosynchronous orbit (GEO) as the destination operational zone. Because of satellite high specific impulse, Orbital maneuvers are considered as impulsive maneuvers in this paper and its validation is verified by comparison of results with continues one. Number of intermediate orbits has been found in order to physical constraints. In this systematic approach, both minimum-time and fuel-saving using constant acceleration simultaneously as the problem strategy to find the optimal transfer trajectory between two orbits. Set of optimal trajectories are plotted in Pareto Front and transfer trajectory can be selected from these points. Finally, the results are compared with the results obtained using STK software and good agreement has been revealed. The satellite access to ground station (GS) is analyzed and optimal position for GS is found by defining lack of access and mass consumption as objective functions. Finally, disturbance torques induced by liquid apogee motor (LAM) is investigated and thrusters' fuel mass for this disturbance torque control is proposed.
Farid Vakil-Tahami, Mohammad Zehsaz, Arash Mohammad Alizadeh Fard,
Volume 14, Issue 12 (3-2015)
Abstract
In this paper the creep behavior of a functionally graded (FG) rotating disc made of Aluminum 6061 and Silicon Carbide is investigated and the optimum volume fraction of FG disc and its profile has been obtained. For this purpose, the temperature gradiant along the disc radius is obtained by solving the govering heat transfer differential equation. All the thermal properties of the material are assumed to be the function of temperature and volume fraction. To obtain material properties, two models of Mori-Tanaka and Hashin-Schtrickman are used. To validate the results, they are compared with those given in the literature. Two solution methods: semi-analytical and closed form are employed and the results are compared. The optimum design is carried out with one, and multi-objective methods which are based on genetic algorithm. The objectives are increasing the factor of safety, reducing the weight of the disc and reducing the range between minimum and maximum safety factors. The design variables are percentage of volume fraction, the power of material distribution formula, and the thickness of the disc. The results show that two solution methods compare well. Also, it has been shown that high fraction of Silicon Carbide in the outer side the disc provide optimum results. Also, contradiction of the objectives is reviled, hence the results are presented as Pareto front.
Mohsen Broghany, Sedigheh Basirjafari, Saber Saffar,
Volume 16, Issue 2 (4-2016)
Abstract
In an anechoic chamber, the flat multi-layer sound absorber is cheaper, easier to install and less complicated in manufacturing than conventional wedge and pyramid absorbers. Therefore, design of the optimum flat multi-layer absorber which has minimum thickness is desirable. In this paper, the genetic algorithm has been employed as an effective optimization tool to determine flat triple layer porous absorber. To obtain a broader range of porous materials, combination of foam and fiber types is used. Theoretical and numerical method (finite element method specifically COMSOL Multi-physics version 4.4) have been used to investigate on the operation of sound absorption correspond to the multi-layer structure. In the first step, mathematical model is verified and finite element method, theoretical and experimental results are compared together for two different samples of structures which show appropriate matching. Furthermore to verify the operation of programmed genetic algorithm, the results obtained from the optimization of flat triple layer porous absorber are compared with others that show accuracy and efficiency of this method. The optimization results indicate that a flat triple layer porous structure can achieve results comparable with quality wedge type structure with overall thickness slightly smaller than a fifth of a wavelength at 80 Hz cut-off frequency.
F. Pashmforoush , M. Kazemi,
Volume 19, Issue 4 (4-2019)
Abstract
In sheet metal forming processes, one of the most important limitations relates to the elastic recovery after punch unloading, which usually leads to spring-back phenomenon. Production of precise parts without spring-back controlling is not possible. Hence, the main aim of the present research is to minimize the amount of spring-back as well as to prevent the crack initiation during bending process of Aluminum A1050-H14 sheet. For this purpose, firstly, the sheet metal bending process was numerically simulated in ABAQUS finite element package. Then, the effect of friction coefficient and punch velocity was investigated on elastic recovery and von Mises stress in order to minimize the spring-back as well as to prevent the crack initiation. In this regard, python programming language was utilized. Then, by linking multi-objective genetic algorithm and finite element method in modeFRONTIER software, the optimum values of the process parameters were determined. It should be mentioned that for validation purposes, the simulation results of the present study were compared with the experimental data available in literature, showing a 3.14% relative error between the numerical and experimental results.
Mohammad Reza Bagheri, Masoud Mosayebi, Asghar Mahdian, Ahmad Keshavarzi,
Volume 19, Issue 8 (8-2019)
Abstract
The present paper applies a multi-objective genetic algorithm for optimally design of a vehicle suspension. The vehicle model considers three-dimensional movements of vehicle body. In this full vehicle model having 8 degrees of freedom, vertical movement of passenger seat, vehicle body, and 4 tires as well as rotational movements of vehicle body create the degrees of freedom of the model. In this paper, applicable suspension parameters, consisting of passenger seat acceleration, vehicle body pitch angle, vehicle body roll angle, dynamic tire force, tire velocity, and suspension deflections are considered and optimized in optimization process. Different pairs of these parameters are selected as objective functions and optimized in multi-objective optimization processes, and Pareto solutions are obtained for pair of objective functions. In final optimization process, the Pareto solution related to the summation of dimensionless parameters in one suspension parameters group versus other group, is derived. In these Pareto solutions, there are important optimum points and designers can choose any optimum points for a particular purpose. Pareto optimization is better than other multi-objective optimization methods because there are more optimum points on Pareto front, where each point represents a level of optimization for the pairs of objective functions, and designers can choose any of the points to specific purpose.
Volume 22, Issue 2 (9-2018)
Abstract
The purpose of this study is to develope a sustainable recovery model for used vehicle in which economic, environmental and social impacts are balanced. This study is result or purpose based and is applied and in terms of method is mathematical programming modeling – quantitative. In order to collecting required data, a questionnaire of paired comparison applied. As well as data modeling for research in case of research, for solving various problems of mathematical programming model by Hypothetical data documentation and experts ideas in Saipa company gathered. Fuzzy Analytic Hierarchy Process has been set appropriate criteria weight for defining social functions applied. Then, using concepts and principles of mathematical modeling has been paid to determine sets, parameters, variables, objective functions and limitations of the mathematical model for locating car waste recovery sites. Then mathematical modeling provided by multi-objective genetic algorithm solved. In this study proposed hybrid algorithm and simple NSGA-II for solving the model used and compared. Some of test problems randomly generated and solved by both algorithms. Also, case study problem is solved using proposed NSGA-II hybrid algorithm. The analysis of data for this study has been done using Excel and MATLAB. Results show that dismantling facility should be establish in Tehran, Semnan, Khorasan, Tabriz, Kashan, and processing facility should be set in Semnan, Khorasan and Tabriz. Solving the test problems show that the proposed NSGA-II hybrid algorithm in terms of solution quality is better simple NSGA-II algorithm and proposed NSGA-II hybrid algorithm is more time consuming to solve.
