Classical Design Problem Research Articles

Level set method via positive parts for optimal design problems of two-material thermal conductors

This paper is concerned with optimal design problems for two-material thermal conductors via level set methods based on (doubly) nonlinear diffusion equations. In level set methods with material representations via characteristic functions, gradient descent methods cannot be applied directly in terms of the differentiability of objective functionals with respect to level set functions, and therefore, appropriate sensitivities need to be constructed. This paper proposes a formulation via the positive parts of level set functions to avoid heuristic derivation of sensitivities and to apply (generalized gradient) descent methods. In particular, some perturbation term, such as a perimeter constraint, is involved in the formulation, and then an existence theorem for minimizers will be proved. Furthermore, convergence of objective functionals for minimizers with respect to a parameter of the perturbation term will also be discussed. In this paper, by deriving so-called weighted sensitivities, two-phase domains are numerically constructed as candidates for optimal configurations to approximate minimum values for classical design problems in two-dimensional cases.

A Comparative Study of Metaheuristic Optimization Algorithms for Solving Engineering Design Problems

Metaheuristic optimization algorithms (Nature-Inspired Optimization Algorithms) are a class of algorithms that mimic the behavior of natural systems such as evolution process, swarm intelligence, human activity and physical phenomena to find the optimal solution. Since the introduction of meta-heuristic optimization algorithms, they have shown their profound impact in solving the high-scale and non-differentiable engineering problems. This paper presents a comparative study of the most widely used nature-inspired optimization algorithms for solving engineering classical design problems, which are considered challenging. The teen metaheuristic algorithms employed in this study are, namely, Artificial Bee Colony (ABC), Ant Colony Optimization (ACO), Biogeography Based Optimization Algorithm (BBO), Covariance Matrix Adaptation Evolutionary Strategy (CMA-ES), Cuckoo Search algorithm (CS), Differential Evolution (DE), Genetic Algorithm (GA), Grey Wolf Optimizer (GWO), Gravitational Search Algorithm (GSA) and Particle Swarm Optimization (PSO). The efficiency of these algorithms is evaluated on teen popular engineering classical design problems using the solution quality and convergence analysis, which verify the applicability of these algorithms to engineering classical constrained design problems. The experimental results demonstrated that all the algorithms provide a competitive solution.

Design for Additive Manufacturing of Functionally Graded Lattice Structures: A Design Method with Process Induced Anisotropy Consideration

Lattice structures are well-known as a solution for designing parts with lightweight and multifunctional characteristics. Owing to the advancement of additive manufacturing (AM), the development of design methods for additively manufactured lattice structures has extensively progressed, especially for functionally graded lattice structures (FGLS). Despite plenty of available design frameworks, the application of AM constraints in the design of FGLS is limited to geometric issues. Further, there is a lack of design methods that consider the unique physical properties of additively manufactured parts, especially the anisotropic characteristics induced by AM processes. This paper proposes a novel method for the design of additively manufactured functionally graded lattice structures with the consideration of AM anisotropic properties. In addition, a customized anisotropic AM-Lattice material model that supports the design of FGLS through the density-variable topology optimization is proposed. Moreover, Fused Deposition Modeling (FDM) process in which the process-induced anisotropy of AM is clearly demonstrated is focused. The design method was validated by the three-point bending-beam design problem, a classical design problem for validating topology optimization. The results, showing agreements between simulations and experiments, prove the validity and practicality of the proposed method.

Optimal shape and motion planning for dynamic planar manipulation

This paper presents a framework for optimizing both the shape and the motion of a planar rigid end-effector to satisfy a desired manipulation task. Both shape and motion play key roles in determining contact interaction, and while both are commonly seen as design/control freedoms, their synergies are rarely formally explored. In this paper we study quasistatic problems like cam design, or dynamic problems like ball throwing, where both the shape and motion of the surfaces at contact are relevant. We frame this design problem as a nonlinear optimization program, where shape and motion are decision variables represented as splines. The task is represented as a series of constraints, along with a fitness cost, which force the solution to be compatible with the dynamics of frictional hard contact while satisfying the task. We illustrate the approach with the example problem of moving a disk along a desired path or trajectory, and we verify it by applying it to three classical design problems: the rolling brachistochrone, the design of teeth of involute gears, and the pitch curve of rolling cams. We conclude with a case study involving the optimization and real implementation of the shape and motion of a dynamic throwing arm.

ℋ∞ state feedback switched control for discrete time-varying polytopic systems

This article treats, in a new framework, a classical design problem, namely ℋ∞ state feedback switched control for discrete time-varying polytopic systems. The main goal is to jointly design a set of state feedback gains and a switching rule in order to assure a pre-specified ℋ∞ guaranteed level. The main contribution is to generalise switched system results to design a switched controller that does not require online measurements of the time-varying parameters. This property has important consequences mainly because the performance quality is preserved even in the lack of parameter information. Our conditions are based on modified Riccati–Metzler inequalities and are described in terms of linear matrix inequalities. An academical example compares the proposed technique with others from the literature.

Optimal design of four-bar mechanisms using a hybrid multi-objective GA with adaptive local search

Responding to an increasing demand for mechanism synthesis tools that are both efficient and accurate, this paper presents a novel approach to the multi-objective optimal design of four-bar linkages for path-generation purposes. Three, often conflicting criteria including the mechanism's tracking error, deviation of its transmission angle from 90° and its maximum angular velocity ratio are considered as objectives of the optimization problem. To accelerate the search in the highly multimodal solution space, a hybrid Pareto genetic algorithm with a built-in adaptive local search is employed which extends its exploration to an adaptively adjusted neighborhood of promising points. The efficiency of the proposed algorithm is demonstrated by applying it to a classical design problem for one, two and three objective functions and comparing the results with those reported in the literature. The comparison shows that the proposed algorithm distinctly outperforms other algorithms both quantitatively and qualitatively (from a practical point of view).

Reusable design: A proposed approach to Public Health Informatics system design

BackgroundSince it was first defined in 1995, Public Health Informatics (PHI) has become a recognized discipline, with a research agenda, defined domain-specific competencies and a specialized corpus of technical knowledge. Information systems form a cornerstone of PHI research and implementation, representing significant progress for the nascent field. However, PHI does not advocate or incorporate standard, domain-appropriate design methods for implementing public health information systems. Reusable design is generalized design advice that can be reused in a range of similar contexts. We propose that PHI create and reuse information design knowledge by taking a systems approach that incorporates design methods from the disciplines of Human-Computer Interaction, Interaction Design and other related disciplines.DiscussionAlthough PHI operates in a domain with unique characteristics, many design problems in public health correspond to classic design problems, suggesting that existing design methods and solution approaches are applicable to the design of public health information systems. Among the numerous methodological frameworks used in other disciplines, we identify scenario-based design and participatory design as two widely-employed methodologies that are appropriate for adoption as PHI standards. We make the case that these methods show promise to create reusable design knowledge in PHI.SummaryWe propose the formalization of a set of standard design methods within PHI that can be used to pursue a strategy of design knowledge creation and reuse for cost-effective, interoperable public health information systems. We suggest that all public health informaticians should be able to use these design methods and the methods should be incorporated into PHI training.

A Review of an Optimal Design Problem for a Plate of Variable Thickness

We revisit a classic design problem for a plate of variable thickness under the model of Kirchhoff. Our main contribution has two goals. One is to provide a rather general existence result under a main assumption on the structure of the tensor of material constants. The other focuses on providing a minimal number of additional design variables for a relaxation of the problem when that assumption on the tensor of elastic constants does not hold. In both situations, the cost functional can be pretty general.

Adaptation of density distributions for optimising aluminium foam structures

Metallic foams show some potential for being produced with controlled spatial variations in their density. This suggests employing them as graded materials in space filling lightweight structures designed in analogy to cortical bone, a natural cellular material, that displays increased density in regions of high loading. In the present study the influence of the mechanical properties of aluminium foams on the results of an optimisation of the foam density distribution with regard to structural strength and stiffness was examined. Regression formulae for the relationships between stiffness and strength of metallic foams on one hand and effective density on the other hand can be fitted to the results of uniaxial compression tests of a certain brand of metallic foam. These results and additional assumptions such as overall isotropy and a yield surface suitable for cellular materials can be implemented into a finite element program adapted for performing stiffness or strength optimisation on the basis of a density adaptation similar to the remodelling of bone. Some applications are presented that show how foams with gradients in the apparent density may be employed to obtain optimal structural behaviour for classical design problems.

Genetic algorithm synthesis of four-bar mechanisms

AbstractThe synthesis of four-bar mechanisms is a well-understood, classical design problem. The original systematic work in this field began in the late 1800s and continues to be an active area of research. Limitations to the classical theory of four-bar synthesis potentially limit its application to certain real-world problems by virtue of the small number of precision points and unspecified order. This paper presents a numerical technique for four-bar mechanism synthesis based on genetic algorithms that removes this limitation by relaxing the accuracy of the precision points.

On the principles of aerodynamic design

It is suggested that the development of aeroplanes requires, at the beginning, the solution of an aerodynamic design problem, namely, to find in broad outline classes of shapes with acceptable physical properties and types of flow which are usable in engineering practice. The basic principles of the classical design problem are briefly discussed and it is indicated how these methods can logically be extended to lead to new types of aircraft such as the slender wing.