General Design Optimization Research Articles

A new harmony search algorithm for solving mixed–discrete engineering optimization problems

In general design optimization problems, it is usually assumed that the design variables are continuous. However, many practical problems in engineering design require considering the design variables as integer or discrete values. The presence of discrete and integer variables along with continuous variables adds to the complexity of the optimization problem. Very few of the existing methods can yield a globally optimal solution when the objective functions are non-convex and non-differentiable. This article presents a mixed–discrete harmony search approach for solving these nonlinear optimization problems which contain integer, discrete and continuous variables. Some engineering design examples are also presented to demonstrate the effectiveness of the proposed method.

Simulation of maximum power in the wearable thermoelectric generator with a small thermopile

Miniature thermopiles that could be fabricated by using modern thin- and thick-film technologies are discussed as a power supply to wearable devices. The maximum power that can be produced by a thermopile of a medium-to-small size was simulated in case of typical thermal properties of humans and their living environment. The local thermal resistances of human being required for the simulation were obtained experimentally. The designs of wearable thermoelectric generators are discussed. The general design optimization of wearable thermoelectric energy harvester with a miniature thermopile was performed in case of near-maximum power generated per unit volume of thermoelectric generator. The obtained performance characteristics allow prediction of the application area for wearable energy harvesters of human body heat and the perspectives of their market success.

Optimal Experimental Design for Assessment of Enzyme Kinetics in a Drug Discovery Screening Environment

A penalized expectation of determinant (ED)-optimal design with a discrete parameter distribution was used to find an optimal experimental design for assessment of enzyme kinetics in a screening environment. A data set for enzyme kinetic data (V(max) and K(m)) was collected from previously reported studies, and every V(max)/K(m) pair (n = 76) was taken to represent a unique drug compound. The design was restricted to 15 samples, an incubation time of up to 40 min, and starting concentrations (C(0)) for the incubation between 0.01 and 100 μM. The optimization was performed by finding the sample times and C(0) returning the lowest uncertainty (S.E.) of the model parameter estimates. Individual optimal designs, one general optimal design and one, for laboratory practice suitable, pragmatic optimal design (OD) were obtained. In addition, a standard design (STD-D), representing a commonly applied approach for metabolic stability investigations, was constructed. Simulations were performed for OD and STD-D by using the Michaelis-Menten (MM) equation, and enzyme kinetic parameters were estimated with both MM and a monoexponential decay. OD generated a better result (relative standard error) for 99% of the compounds and an equal or better result [(root mean square error (RMSE)] for 78% of the compounds in estimation of metabolic intrinsic clearance. Furthermore, high-quality estimates (RMSE < 30%) of both V(max) and K(m) could be obtained for a considerable number (26%) of the investigated compounds by using the suggested OD. The results presented in this study demonstrate that the output could generally be improved compared with that obtained from the standard approaches used today.

Computation as Estimation: A General Framework for Robustness and Energy Efficiency in SoCs

Traditional integrated circuit design achieves error-free operation by designing with margins (clock frequency and supply voltage) and/or including hardware replication and recomputation, which may counter the full energy and area benefits of aggressive technology scaling. It is thus desirable that modern systems-on-chip (SoCs) permit hardware errors while maintaining robust system-level performance. Treating hardware errors as computational noise and extending traditional estimation theory to include practical SoC design constraints yields a novel and general design optimization framework. This work demonstrates the breadth of applicability of the estimation-theoretic framework for system design by showcasing two different application classes that demonstrate 36% to 50% power reduction.

A Nonhierarchical Formulation of Analytical Target Cascading

Analytical target cascading (ATC) is a method developed originally for translating system-level design targets to design specifications for the components that comprise the system. ATC has been shown to be useful for coordinating decomposition-based optimal system design. The traditional ATC formulation uses hierarchical problem decompositions, in which coordination is performed by communicating target and response values between parents and children. The hierarchical formulation may not be suitable for general multidisciplinary design optimization (MDO) problems. This paper presents a new ATC formulation that allows nonhierarchical target-response coupling between subproblems and introduces system-wide functions that depend on variables of two or more subproblems. Options to parallelize the subproblem optimizations are also provided, including a new bilevel coordination strategy that uses a master problem formulation. The new formulation increases the applicability of the ATC to both decomposition-based optimal system design and MDO. Moreover, it belongs to the class of augmented Lagrangian coordination methods, having thus convergence properties under standard convexity and continuity assumptions. A supersonic business jet design problem is used to demonstrate the flexibility and effectiveness of the presented formulation.

Optimization of System Parameters for Liquid Rocket Engines with Gas-Generator Cycles

System design of liquid rocket engines must consider engine performance, weight, cost, and reliability requirements. A general design optimization framework has been developed in this paper to select the best system parameters for liquid rocket engines with gas-generator cycles. The object is to maximize the specific impulse and vacuum thrust-to-weight ratio of the engine with given system requirements and design assumptions by changing thrust-chamber pressure and mixture ratio. The system analysis, along with the engine weight estimation, is based on a modular scheme. Multidisciplinary design optimization formulations including multidisciplinary feasible and collaborative optimization are used, evaluated, and compared during the optimization process. Several techniques of multi-objective processing are also used to identify the Pareto frontier and the optimal compromise solutions. A proposed cryogenic-propellant engine using liquid oxygen and hydrogen with a gas-generator cycle is studied as a specific example. Moreover, uncertainties in the engine operation, such as thrust-chamber pressure and mixture ratio, are taken into account as random variables in the reliability-based optimization. Results are presented to illustrate the tradeoff between the engine performance and reliability requirements.

Design Considerations for an Underactuated Robotic Finger Mechanism

A design approach is presented in this paper for underactuation in robotic finger mechanisms. The characters of underactuated finger mechanisms are introduced as based on linkage and spring systems,The feature of self-adaptive enveloping grasp by underactuated finger mechanisms is discussed with feasible in grasping unknown objects. The design problem of robotic fingers is analyzed by looking at many aspects for an optimal functionality. Design problems and requirements for underactuated mechanisms are formulated as related to human-like robotic fingers. In particular,characteristics of finger mechanisms are analyzed and optimality criteria are summarized with the aim to formulate a general design algorithm. A general multi-objective optimization design approach is applied as based on a suitable optimization problem by using suitable expressions of optimality criteria. An example is illustrated as an improvement of finger mechanism in Laboratory of Robotics and Mechatronics (LARM) Hand. Results of design outputs and grasp simulations are reported with the aim to show the practical feasibility of the proposed concepts and computations.

A Design-Specific and Thermally-Aware Methodology for Trading-Off Power and Performance in Leakage-Dominant CMOS Technologies

As CMOS technology scales deeper into the nanometer regime, factors such as leakage power and chip temperature emerge as critically important concerns for high-performance VLSI design. Consequently, enhancing processing performance is no longer the most important factor that dominates future circuit design considerations. This paper, for the first time, proposes a systematic methodology to determine a generalized design optimization metric for simultaneously trading-off power and performance in nanometer scale integrated circuits to achieve design-specific targets. The methodology incorporates interconnect effects as well as electrothermal couplings between substrate temperature, power, and performance for nanometer scale design optimization. Implications of choosing a specific design optimization metric on power, performance, and operating temperature are illustrated and discussed. The proposed methodology is shown to provide a more meaningful optimization metric (for power-performance tradeoff analysis) and basis, with considerations of chip-level thermal management including maximum allowable operating temperature and packaging/cooling solutions. Furthermore, implications of CMOS technology scaling and parameter variations on the proposed methodology are discussed.

Optimized Design of Piezoelectric Flap Actuators for Active Flow Control

Piezoelectric flap actuators are often used in active flow-control applications. However, effective design tools are lacking in the flow-control community. This paper discusses theoretical modeling, experimental validation, and optimal design of piezoelectric unimorph and bimorph flap actuators. First, two different finite element models are described. One is a simple beam model that assumes a perfect bond exists between the piezoelectric patch and the shim,whereasthesecondincorporatesalinearelasticshearelementforthebondlayer.Thesemodelsarethenusedto predict the magnitude of the dc response (tip displacement per unit applied voltage) and the natural frequency (a measureofthebandwidth)oftheseactuators.Next,anapproximateanalyticalmodelisdevelopedtofacilitatedesign optimization. The models are compared with experimental data obtained from a parametric study in which 10 otherwise identical unimorph piezoelectric actuators with varying piezoelectric patches are fabricated and characterizedusingalaserdisplacementsensor.Allmodelsproduceestimatesthatareaccuratetowithin15%and 10% for the dc response and natural frequency, respectively. The analytical model is also extended to bimorph actuators. Finally, a general design optimization procedure is presented, and representative results are provided.

Family design of scroll compressors with optimization

This paper proposes a systematic design method for developing a family of scroll-type compressor (STC). Except of using the general design optimization model includes multi-variable, direct search, inequality constraints, both interactive session and discrete variable design optimization skills have also been employed in this study. A practical design case on the 5200–9800W capacity range of the STC family using R22 refrigerant has been implemented, and to achieve a common share percentage of 80% for the major components of this STC series plus a coefficient of performance based on electrical power input (COPel) of over 3.02 for each specified capacity of this family. Comparisons between calculated and measured results show that the maximum deviation of cooling capacity and COPel are below 2.53% and 1.69%, respectively.

Design considerations for passive gamma-ray spectrometers

Passive gamma-ray spectrometers composed of attenuation filters and integrating detection materials provide important advantages for measurements in high-radiation environments and for long-term monitoring. Each of these applications has requirements that constrain the design of the instrument, such as incident energy range of interest, sensor size and weight, readout method, and cost. The multitude of parameters in passive spectrometer design (e.g., attenuation filter material and thickness, integrating sensor type, number of pixels, reconstructed energy bin structure) results in a large design space to examine. The development of generalized design optimization tools to interrogate this space and to identify promising spectrometer designs is discussed, particularly the methods used to rapidly calculate system transfer functions and the use of genetic algorithms for design optimization. Preliminary measurements to validate the design tools are described, and example results from early design optimization efforts are provided.

Reliability Estimation and Design with Insufficient Data Based on Possibility Theory

Early in the engineering design cycle, it is difficult to quantify product reliability or compliance to performance targets because of insufficient data or information for modeling the uncertainties. Design decisions are, therefore, based on fuzzy information that is vague, imprecise, qualitative, linguistic, or incomplete. The uncertain information is usually available as intervals with lower and upper limits. In this work, the possibility theory is used to assess design reliability with incomplete information. The possibility theory can be viewed as a variant of fuzzy set theory. The formal theories to handle uncertainty are first introduced using the theoretical fundamentals of fuzzy measures. A computationally efficient and accurate hybrid (global-local) optimization approach is subsequently described for calculating the confidence level of fuzzy response. The method combines the advantages of the commonly used vertex and discretization methods. Subsequently, the possibility theory is used in design. A possibility-based design optimization method is proposed where all design constraints are expressed in a possibilistic way. It is shown that the method gives a conservative solution compared with all conventional reliability-based designs obtained with different probability distributions. Finally, a general possibility-based design optimization method, which handles a combination of random and possibilistic design variables, is presented. Several numerical examples demonstrate the application of possibility theory in design.

Two-point mid-range approximation enhanced recursive quadratic programming method

This research represents an attempt to combine good convergence properties of recursive quadratic programming methods with the benefits of mid-range approximations, initially developed in the field of structural optimization. In this paper, an optimization method based on Arora and coworkers’ PLBA (Pshenichny–Lim–Belegundu–Arora) algorithm is proposed in which, during the line search phase, cost and constraint functions are substituted by their two-point approximations using the Generalized Convex Approximation formulae of Chickermane and Gea. The results showed that the proposed optimization method preserves the reliability and accuracy of the recursive quadratic programming method while it might simultaneously reduce the computational effort for some problems. Therefore, the proposed optimization method may be taken as potentially suitable for general design optimization purposes.

The global optimization design for electron emission system using genetic algorithms

The general optimization design method, such as Simplex method and Powell method, etc., can determine the final optimum structure and electric parameters of an electron optical system from given electron optical properties, but it may land in a local minimum of the optimum search process. The Genetic Algorithms (GAs) is a novel direct search optimization method based on principles of natural selection and “survival of the fittest” from natural evolution. Through the “reproduction”, “crossover” and “mutation” iterative process, GAs can search the global optimum result. In this paper, we applied the GAs to optimize an electron emission system, a “triode” structure used in a projection display with high resolution and brightness. The optimal structure and corresponding electrical parameters with a criterion of minimum objective function value, crossover radius, have been searched and presented in this paper. The GAs, as a direct search method and an adaptive search technique, has significant advantage in the optimization design of electron optical systems.

A novel method for biomaterial scaffold internal architecture design to match bone elastic properties with desired porosity

An often-proposed tissue engineering design hypothesis is that the scaffold should provide a biomimetic mechanical environment for initial function and appropriate remodeling of regenerating tissue while concurrently providing sufficient porosity for cell migration and cell/gene delivery. To provide a systematic study of this hypothesis, the ability to precisely design and manufacture biomaterial scaffolds is needed. Traditional methods for scaffold design and fabrication cannot provide the control over scaffold architecture design to achieve specified properties within fixed limits on porosity. The purpose of this paper was to develop a general design optimization scheme for 3D internal scaffold architecture to match desired elastic properties and porosity simultaneously, by introducing the homogenization-based topology optimization algorithm (also known as general layout optimization). With an initial target for bone tissue engineering, we demonstrate that the method can produce highly porous structures that match human trabecular bone anisotropic stiffness using accepted biomaterials. In addition, we show that anisotropic bone stiffness may be matched with scaffolds of widely different porosity. Finally, we also demonstrate that prototypes of the designed structures can be fabricated using solid free-form fabrication (SFF) techniques.

A general equation and optimal design for a 2-factor restricted region

Economic, practical, or physical constraints sometimes prevent the factor space of a designed experiment from being a regular p-dimensional hypercube or hypersphere. Since standard designs may not be the best choice, it is desirable to be able to find best designs under these restrictions. This paper extends the work of Zahran et al. (J. Quality Tech. 35 (4)) using a more general equation to define the boundary of a modifying 2 2 factorial design and considers optimality criteria for the best of the designs.

Analysis and design of distributed ESD protection circuits for high-speed mixed-signal and RF ICs

Electrostatic discharge (ESD) protection devices can have an adverse effect on the performance of high-speed mixed-signal and RF circuits. This paper presents quantitative methodologies to analyze the performance degradation of these circuits due to ESD protection. A detailed S-parameter-based analysis of these high-frequency systems illustrates the utility of the distributed ESD protection scheme and the impact of the parasitics associated with the protection devices. It is shown that a four-stage distributed ESD protection can be beneficial for frequencies up to 10 GHz. In addition, two generalized design optimization methodologies incorporating coplanar waveguides are developed for the distributed structure to achieve a better impedance match over a broad frequency range (0-10 GHz). By using this optimized design, an ESD device with a parasitic capacitance of 200 fF attenuates the RF signal power by only 0.27 dB at 10 GHz. Furthermore, termination schemes are proposed to allow this analysis to be applicable to high-speed digital and mixed-signal systems.

Design optimization of silo structures made from composite materials Part 1: design of the vertical cylindrical section

AbstractThis study implements the general design optimization procedures that have been formulated for composite materials to the design of silo structures. Recent Eurocodes and other guides have presented a thorough summary of the necessary procedures for steel silo design. However, design guidance for composite silos is less readily available. While the use of a composite material requires consideration of the anisotropy of the material properties, it also allows a greater degree of interaction between the material and the design requirements. This paper, and its companion, present a genera) approach to the optimized design of the main parts of a cylindrical silo structure, i.e. the upper cylindrical section (Part 1) and the hopper (Part 2) respectively. The general methodology is outlined, and the effectiveness of the optimization is demonstrated using a particular example. In this case, the resultant optimized design produced a 16 per cent saving in wall thickness, and thus material cost, in comparison with the non-optimized wall thickness.

Design optimization of silo structures made from composite materials Part 1: Design of the vertical cylindrical section

This study implements the general design optimization procedures that have been formulated for composite materials to the design of silo structures. Recent Eurocodes and other guides have presented a thorough summary of the necessary procedures for steel silo design. However, design guidance for composite silos is less readily available. While the use of a composite material requires consideration of the anisotropy of the material properties, it also allows a greater degree of interaction between the material and the design requirements. This paper, and its companion, present a genera) approach to the optimized design of the main parts of a cylindrical silo structure, i.e. the upper cylindrical section (Part 1) and the hopper (Part 2) respectively. The general methodology is outlined, and the effectiveness of the optimization is demonstrated using a particular example. In this case, the resultant optimized design produced a 16 per cent saving in wall thickness, and thus material cost, in comparison with the non-optimized wall thickness.

Design optimization of silo structures made from composite materials Part 2: Optimum design of the composoite conical hopper

This study implements the general design optimization procedures that have been formulated for composite materials to the design of silo structures. Recent Eurocodes and other guides have presented a thorough summary of the necessary procedures for steel silo design. However, design guidance for composite silos is less readily available. While the use of a composite material requires consideration of the anisotropy of the material properties, it also allows a greater degree of interaction between the material and the design requirements. This paper, and its companion, present a general approach to the optimized design of the main parts of a cylindrical silo structure, i.e. the upper cylindrical section (Part 1) and the hopper (Part 2) respectively. The present paper develops the structural optimization of multilaycred and multizonal composite shells further for this particular application. Using the particular silo design outlined in Part 1, it is shown that a reduction in material of more than 50 per cent is achieved compared with the equivalent single-zone design for the conical hopper.