共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Mohsine A. El Hami 《Computer Methods in Applied Mechanics and Engineering》2010,199(17-20):1006-1018
Nowadays, the search in reliability-based design optimization is becoming an important engineering design activity. Traditionally for these problems, the objective function is to minimize a cost function while satisfying the reliability constraints. The reliability constraints are usually formulated as constraints on the probability of failure. This paper focuses on the study of a particular problem with the failure mode on vibration of structure. The difficulty in evaluating reliability constraints comes from the fact that modern reliability analysis methods are themselves formulated as an optimization problem. Solving such nested optimization problems is extremely expensive for large-scale multidisciplinary systems which are likewise computationally intensive. With this in mind research, we propose in this paper a new method to treat reliability-based optimization methods under frequencies constraint. The goal of this development has resolved just one problem of optimization and reduced the cost of computation. Aircraft wing design typically involves multiple disciplines such as aerodynamics and structure; this numerical example demonstrated the different advantages of the proposed method. 相似文献
2.
JINN-SHING CHENG FENG-HSIAG HSIAO JER-GUANG HSIEH 《International journal of systems science》2013,44(11):2101-2119
A systematic and effective design procedure for a class of linear multivariable feedback control systems is proposed For simultaneously achieving robust tracking of the prescribed input signal via the Q-parametrization approach and internal model principle, the prescribed transient specifications by choosing an appropriate performance criterion, robust stabilization, and sensitivity minimization. The problem can best be cast in the form of an optimization problem with dynamic constraints. A numerical method is formulated to solve the optimization problem with dynamic constraints using a non-linear programming method. A numerical example is provided to illustrate the main results of the paper. 相似文献
3.
A level set based topology optimization method using the discretized signed distance function as the design variables 总被引:2,自引:2,他引:0
Shintaro Yamasaki Tsuyoshi Nomura Atsushi Kawamoto Kazuo Sato Kazuhiro Izui Shinji Nishiwaki 《Structural and Multidisciplinary Optimization》2010,41(5):685-698
This paper deals with a new topology optimization method based on the level set method. In the proposed method, the discretized
signed distance function, a kind of level set function, is used as the design variables, and these are then updated using
their sensitivities. The signed distance characteristic of the design variables are maintained by performing a re-initialization
at every update during the iterated optimization procedure. In this paper, a minimum mean compliance problem and a compliant
mechanism design problem are formulated based on the level set method. In the formulations of these design problems, a perimeter
constraint is imposed to overcome the ill-posedness of the structural optimization problem. The sensitivity analysis for the
above structural optimization problems is conducted based on the adjoint variable method. The augmented Lagrangian method
is incorporated to deal with multiple constraints. Finally, several numerical examples that include multiple constraints are
provided to confirm the validity of the method, and it is shown that appropriate optimal structures are obtained. 相似文献
4.
Xiaoxia Dai Chengwei Zhang Ye Zhang Mårten Gulliksson 《Structural and Multidisciplinary Optimization》2018,57(6):2193-2203
This paper presents a piecewise constant level set method for the topology optimization of steady Navier-Stokes flow. Combining piecewise constant level set functions and artificial friction force, the optimization problem is formulated and analyzed based on a design variable. The topology sensitivities are computed by the adjoint method based on Lagrangian multipliers. In the optimization procedure, the piecewise constant level set function is updated by a new descent method, without the needing to solve the Hamilton-Jacobi equation. To achieve optimization, the piecewise constant level set method does not track the boundaries between the different materials but instead through the regional division, which can easily create small holes without topological derivatives. Furthermore, we make some attempts to avoid updating the Lagrangian multipliers and to deal with the constraints easily. The algorithm is very simple to implement, and it is possible to obtain the optimal solution by iterating a few steps. Several numerical examples for both two- and three-dimensional problems are provided, to demonstrate the validity and efficiency of the proposed method. 相似文献
5.
Jiangzi Lin Zhen Luo Liyong Tong 《Structural and Multidisciplinary Optimization》2010,40(1-6):241-255
This paper presents an alternative method in implementing multi-objective optimization of compliant mechanisms in the field of continuum-type topology optimization. The method is designated as “SIMP-PP” and it achieves multi-objective topology optimization by merging what is already a mature topology optimization method—solid isotropic material with penalization (SIMP) with a variation of the robust multi-objective optimization method—physical programming (PP). By taking advantages of both sides, the combination causes minimal variation in computation algorithm and numerical scheme, yet yields improvements in the multi-objective handling capability of topology optimization. The SIMP-PP multi-objective scheme is introduced into the systematic design of compliant mechanisms. The final optimization problem is formulated mathematically using the aggregate objective function which is derived from the original individual design objectives with PP, subjected to the specified constraints. A sequential convex programming method, the method of moving asymptotes (MMA) is then utilized to process the optimization evolvement based on the design sensitivity analysis. The main findings in this study include distinct advantages of the SIMP-PP method in various aspects such as computation efficiency, adaptability in convex and non-convex multi-criteria environment, and flexibility in problem formulation. Observations are made regarding its performance and the effect of multi-objective optimization on the final topologies. In general, the proposed SIMP-PP method is an appealing multi-objective topology optimization scheme suitable for “real world” problems, and it bridges the gap between standard topological design and multi-criteria optimization. The feasibility of the proposed topology optimization method is exhibited by benchmark examples. 相似文献
6.
M. H. Nagrial 《Computers & Electrical Engineering》1984,11(4):191-199
The design of squirrel-cage induction motors is formulated as a nonlinear programming problem, to predict a computer-aided optimum design. The cost of active materials is taken as an objective function. A constrained optimization method called the Complex Method is used to predict optimum design while meeting the specification requirements, formulated as constraints. The flow-chart diagram and design procedure is given. 相似文献
7.
On the design optimization of built-up stiffened steel beams with buckling and frequency constraints
The literature on the structural design optimization of steel-plate girders indicates a need for more refined research studies to obtain optimal designs by formulating and solving the design problem that combines structural sizing and shape parameters in one unified, constrained problem. For this purpose, the structural optimization design problem of stiffened steel-plate girders is formulated with specified loading conditions and constraints on strength and serviceability considerations including limits on fundamental frequency and buckling modes. The finite-element method-based model is used to define the objective function and the structural/geometric response functions, while the geometric domain elements are used to systematically perturb the structural shape during the search for an optimal shape of the structure. The mathematical statement of the gradient-based-design problem is solved for an optimal structural size and shape with buckling and frequency constraints in addition to the traditional strength constraints. The numerical results obtained are compared with results obtained from a less formal ad hoc design procedure, and some conclusions are drawn to emphasize the design benefits obtained from solving the design problem for optimal structural size and shape. 相似文献
8.
Constrained optimization of an idealized Y-shaped baffle for the Fontan surgery at rest and exercise
Weiguang Yang Jeffrey A. Feinstein Alison L. Marsden 《Computer Methods in Applied Mechanics and Engineering》2010,199(33-36):2135-2149
Coupling shape optimization to three-dimensional unsteady cardiovascular simulations poses several key challenges, including high computational cost, a need to handle constraints, and a need for automatic generation of parameterized vessel geometry. In this work we extend our previous framework for cardiovascular optimization to include constraints, pulsatile flow under both rest and exercise conditions, and multiple geometric parameters. Optimization is performed using a derivative-free algorithm called the surrogate management framework, with constraints enforced using a filter method. In this work, we examine a specific surgery called the Fontan, which is performed to treat single-ventricle heart patients. These patients typically undergo a series of three surgeries, the last of which connects the inferior vena cava to the pulmonary arteries. Our group and others have recently proposed and evaluated a new Y-graft modification of the Fontan operation that replaces the current tube shaped baffle. Preliminary simulations have shown that the Y-graft modification is a promising design that increases energy efficiency and improves flow distribution to the pulmonary arteries. In this work, we perform optimization on a model Y-graft design problem. This work represents the first use of formal design optimization methods for the Fontan surgery, and also demonstrates the applicability of the optimization framework on a pulsatile flow problem with multiple design parameters and constraints. The idealized Y-graft model was parameterized with six geometric parameters including graft diameter and anastomosis locations, and the optimization procedure, including model construction, meshing, and simulation, was executed automatically. Energy efficiency was chosen as the objective function. A constraint on the wall shear stress (WSS), a presumed correlate to thrombosis risk, was added to the problem using a filter method, which allowed for exploration of the trade-offs between WSS and energy efficiency. Optimization was performed at two exercise levels with effects of respiration incorporated, and differences in optimal solutions were examined. It was shown that optimal shapes differed between rest and exercise, as well as steady and pulsatile flow conditions, with wide-span branches and decreasing graft branch size favored with increasing exercise level. The optimization method was found to be robust for different polling strategies, and computationally efficient both with and without constraints. 相似文献
9.
《Computer Methods in Applied Mechanics and Engineering》2005,194(30-33):3472-3495
Fluid–structure interaction phenomena are often roughly approximated when the stochastic nature of a system is considered in the design optimization process, leading to potentially significant epistemic uncertainty. In this paper, after reviewing the state-of-the-art methods in robust and reliability-based design optimization of problems undergoing fluid–structure interaction phenomena, a computational framework is presented that integrates a high-fidelity aeroelastic model into reliability-based design optimization. The design optimization problem is formulated pursuant to the reliability index and performance measure approaches. The system reliability is evaluated by a first-order reliability analysis method. The steady-state aeroelastic problem is described by a three-field formulation and solved by a staggered procedure, coupling a potentially detailed structural finite element model and a finite volume discretization of the Euler flow. The design and imperfection sensitivities are computed by evaluating the analytically derived direct and adjoint coupled aeroelastic sensitivity equations. The computational framework is verified by the optimization of three-dimensional wing structures. The lift-to-drag ratio is maximized, subject to stress constraints, by varying shape, thickness, and material properties. Uncertainties in structural parameters, including design parameters, operating conditions, and modeling uncertainties are considered. The results demonstrate the need for reliability-based optimization methods, for the design of structures undergoing fluid–structure interaction phenomena, and the applicability of the proposed framework to realistic design problems. Comparing the optimization results for different levels of uncertainty shows the importance of accounting for uncertainties in a quantitative manner. 相似文献
10.
For structural systems exhibiting both probabilistic and bounded uncertainties, it may be suitable to describe these uncertainties
with probability and convex set models respectively in the design optimization problem. Based on the probabilistic and multi-ellipsoid
convex set hybrid model, this paper presents a mathematical definition of reliability index for measuring the safety of structures
in presence of parameter or load uncertainties. The optimization problem incorporating such reliability constraints is then
mathematically formulated. By using the performance measure approach, the optimization problem is reformulated into a more
tractable one. Moreover, the nested double-loop optimization problem is transformed into an approximate single-loop minimization
problem by considering the optimality conditions and linearization of the limit-state function, which further facilitates
efficient solution of the design problem. Numerical examples demonstrate the validity of the proposed formulation as well
as the efficiency of the presented numerical techniques. 相似文献
11.
Salam Nema John Y. Goulermas Graham Sparrow Paul Helman 《Structural and Multidisciplinary Optimization》2011,43(1):107-119
Many engineering design problems can be formulated as constrained optimization problems which often consist of many mixed
equality and inequality constraints. In this article, a hybrid coevolutionary method is developed to solve constrained optimization
problems formulated as min–max problems. The new method is fast and capable of global search because of combining particle
swarm optimization and gradient search to balance exploration and exploitation. It starts by transforming the problem into
unconstrained one using an augmented Lagrangian function, then using two groups to optimize different components of the solution
vector in a cooperative procedure. In each group, the final stage of the search procedure is accelerated by via a simple local
search method on the best point reached by the preceding exploration based search. We validated the effectiveness and robustness
of the proposed algorithm using several engineering problems taken from the specialised literature. 相似文献
12.
《Computer Methods in Applied Mechanics and Engineering》2005,194(12-16):1779-1795
The robust design of non-linear structures with path-dependent response is stated as a two-criteria optimization problem and is solved by the method of mathematical programming. To this end, the perturbation technique is applied in conjunction with the incremental loading procedure for the response moment analysis of path-dependent non-linear structural systems with random parameters. Furthermore, the sensitivities of mean and variance of the structural performance function are evaluated using direct differentiation in the framework of perturbation based stochastic finite element analysis. By introducing a weighting factor in the compound objective––resp. desirability function, and feasibility indices in the constraints, the mathematical model of structural robust design problem is formulated and is solved with a gradient-based algorithm. Numerical examples demonstrate the applicability of the presented method. 相似文献
13.
The design of broadband beamformers can be formulated as a semi-infinite programming optimization problem, where the coefficients of the filters are determined such that the actual response of the microphone array is near a given desired response. This problem can be solved by existing optimization solvers after the discretization of the infinite constraints. However, this problem will become large-scale and it's expensive to find the optimal solution, as the discretization points grow and the filter length increases. In this paper, we propose a fast method based on the window functions. First, we formulate a simplified optimization problem to find the limit of the cost function values as the filter length is sufficiently long. Hence, the optimal frequency response vector is obtained and the corresponding filter coefficients can be calculated. Second, we apply the window method to truncate the limiting filter to obtain a finite FIR filters. The performance as well as the computational complexity are investigated to demonstrate the effectiveness and efficiency of the proposed method. 相似文献
14.
15.
In this paper, we consider the design of an H∞ trade‐off dependent controller, that is, a controller such that, for a given Linear Time‐Invariant plant, a set of performance trade‐offs parameterized by a scalar θ is satisfied. The controller state space matrices are explicit functions of θ. This new problem is a special case of the design of a parameter dependent controller for a parameter dependent plant, which has many application in Automatic Control. This last design problem can be naturally formulated as a convex but infinite dimensional optimization problem involving parameter dependent Linear Matrix Inequality (LMI) constraints. In this paper, we propose finite dimensional (parameter independent) LMI constraints which are equivalent to the parameter dependent LMI constraints. The parameter dependent controller design is then formulated as a convex finite dimensional LMI optimization problem. The obtained result is then applied to the trade‐off dependent controller design. A numerical example emphasizes the strong interest of our finite dimensional optimization problem with respect to the trade‐off dependent control application. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
16.
Multidiscipline topology optimization 总被引:1,自引:0,他引:1
R.J. Yang 《Computers & Structures》1997,63(6):1205-1212
Topology optimization is used for determining the best layout of structural components to achieve predetermined performance goals. The density method which uses material density of each finite element as the design variable, is employed. Unlike the most common approach which uses the optimality criteria methods, the topology design problem is formulated as a general optimization problem and is solved by the mathematical programming method. One of the major advantages of this approach is its generality; thus it can solve various problems, e.g. multi-objective and multi-constraint problems. In this study, the structural weight is chosen as the objective function and structural responses such as the compliances, displacements and the natural frequencies, are treated as the constraints. The MSC/NASTRAN finite element code is employed for response analyses. One example with four different optimization formulations was used to demonstrate this approach. 相似文献
17.
In this work, we propose a dynamic output feedback robust model predictive control (RMPC) design method for linear uncertain systems with input constraints. In order to handle the input constraints, the control signals are permitted to saturate, which can fully utilize the capability of actuators and thus can reduce the conservatism. For the unavailable states, an ellipsoidal set is used to obtain an estimation, and it is updated at every time instant. A modified RMPC design requirement is used to ensure the recursive feasibility of the optimization problem. Then, the design method is formulated in terms of a convex optimization problem with linear matrix inequality constraints. The proposed output feedback RMPC design method is expected to further reduce the conservativeness. The improvements of the proposed algorithm over the other existing techniques is demonstrated by an example. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
Jing Zheng Zhen Luo Chao Jiang Bingyu Ni Jinglai Wu 《Structural and Multidisciplinary Optimization》2018,57(6):2205-2221
In this paper, a new non-probabilistic reliability-based topology optimization (NRBTO) method is proposed to account for interval uncertainties considering parametric correlations. Firstly, a reliability index is defined based on a newly developed multidimensional parallelepiped (MP) convex model, and the reliability-based topology optimization problem is formulated to optimize the topology of the structure, to minimize material volume under displacement constraints. Secondly, an efficient decoupling scheme is applied to transform the double-loop NRBTO into a sequential optimization process, using the sequential optimization & reliability assessment (SORA) method associated with the performance measurement approach (PMA). Thirdly, the adjoint variable method is used to obtain the sensitivity information for both uncertain and design variables, and a gradient-based algorithm is employed to solve the optimization problem. Finally, typical numerical examples are used to demonstrate the effectiveness of the proposed topology optimization method. 相似文献
19.
Maliki Moustapha Bruno Sudret Jean-Marc Bourinet Benoît Guillaume 《Structural and Multidisciplinary Optimization》2016,54(6):1403-1421
Uncertainties are inherent to real-world systems. Taking them into account is crucial in industrial design problems and this might be achieved through reliability-based design optimization (RBDO) techniques. In this paper, we propose a quantile-based approach to solve RBDO problems. We first transform the safety constraints usually formulated as admissible probabilities of failure into constraints on quantiles of the performance criteria. In this formulation, the quantile level controls the degree of conservatism of the design. Starting with the premise that industrial applications often involve high-fidelity and time-consuming computational models, the proposed approach makes use of Kriging surrogate models (a.k.a. Gaussian process modeling). Thanks to the Kriging variance (a measure of the local accuracy of the surrogate), we derive a procedure with two stages of enrichment of the design of computer experiments (DoE) used to construct the surrogate model. The first stage globally reduces the Kriging epistemic uncertainty and adds points in the vicinity of the limit-state surfaces describing the system performance to be attained. The second stage locally checks, and if necessary, improves the accuracy of the quantiles estimated along the optimization iterations. Applications to three analytical examples and to the optimal design of a car body subsystem (minimal mass under mechanical safety constraints) show the accuracy and the remarkable efficiency brought by the proposed procedure. 相似文献
20.
Continuum topology optimization with non-probabilistic reliability constraints based on multi-ellipsoid convex model 总被引:2,自引:1,他引:2
Yangjun Luo Zhan Kang Zhen Luo Alex Li 《Structural and Multidisciplinary Optimization》2009,39(3):297-310
Using a quantified measure for non-probab ilistic reliability based on the multi-ellipsoid convex model, the topology optimization
of continuum structures in presence of uncertain-but-bounded parameters is investigated. The problem is formulated as a double-loop
optimization one. The inner loop handles evaluation of the non-probabilistic reliability index, and the outer loop treats
the optimum material distribution using the results from the inner loop for checking feasibility of the reliability constraints.
For circumventing the numerical difficulties arising from its nested nature, the topology optimization problem with reliability
constraints is reformulated into an equivalent one with constraints on the concerned performance. In this context, the adjoint
variable schemes for sensitivity analysis with respect to uncertain variables as well as design variables are discussed. The
structural optimization problem is then solved by a gradient-based algorithm using the obtained sensitivity. In the present
formulation, the uncertain-but bounded uncertain variations of material properties, geometrical dimensions and loading conditions
can be realistically accounted for. Numerical investigations illustrate the applicability and the validity of the present
problem statement as well as the proposed numerical techniques. The computational results also reveal that non-probabilistic
reliability-based topology optimization may yield more reasonable material layouts than conventional deterministic approaches.
The proposed method can be regarded as an attractive supplement to the stochastic reliability-based topology optimization. 相似文献