Masoud Rais-Rohani

Optimal Operation of Active Distribution Grids: A System of Systems Framework

Active distribution grid is composed of autonomous systems which should collaborate with each other in order to operate the entire distribution grid in a secure and economic manner. This paper presents a system of systems (SoS) framework for optimally operating active distribution grids. The proposed SoS framework defines both distribution company (DISCO) and microgrids (MGs) as independent systems, and identifies the process of information exchange among them. As the DISCO and MGs are physically connected together, the operating condition of one might impact the operating point of other systems. The proposed mathematical model uses a decentralized optimization problem aimed at maximizing the benefit of each independent system. A hierarchical optimization algorithm is presented to coordinate the independent systems and to find the optimal operating point of the SoS-based active distribution grid. The numerical results show the effectiveness of the proposed SoS framework and solution methodology.

Integrated aerodynamic-structural design of a transport wing

The integrated aerodynamic-structural design of a subsonic transport wing for minimum weight subject to required range is formulated and solved. The problem requires large computational resources, and two methods are used to alleviate the computational burden. First, a modular sensitivity method that permits the usage of black-box disciplinary software packages, is used to reduce the cost of sensitivity derivatives. In particular, it is shown that derivatives of the aeroelastic response and divergence speed can be calculated without the costly computation of derivatives of aerodynamic influence coefficient and structural stiffness matrices. A sequential approximate optimization is used to further reduce computational cost. The optimization procedure is shown to require a relatively small number of analysis and sensitivity calculations.

Multidisciplinary Design and Prototype Development of a Micro Air Vehicle

This paper discusses the application of multidiscipli nary design optimization (MDO) methodology for the design of a very small remotely piloted airplane for a short-range reconnaissance mission. Low Reynolds number aerodynamics and size requirements are used as primary drivers in the conceptual design of the vehicle, and are combined with performance, stability, propulsion, and weight constraints in the design optimization problem. With vehicle size as the objective function, the constrained optimization problem is solved using a penalty function method. Following the analytical validation of the MDO-based design, a prototype of the design vehicle was developed and flight tested. The results of this investigation show that MDO methodology could be used as an enabling technology in creating nonconventional designs that aim at pushing the limits of flight in low Reynolds number regime. They also show that the level of technology incorporated in the propulsion, navigation and communication, and control systems plays a key role in determining the size and weight of micro air vehicles.

Manufacturability-Based Optimization of Aircraft Structures Using Physical Programming

Complex design optimization problems, which involve many nonlinearly coupled design objectives and constraints, pose considerable difficulties in the formulation of the aggregate objective function. A representative example of such a complex optimization problem is the design of aircraft structures based on strength, stiffness, manufacturability, and cost requirements. An effective methodology for such a design has recently been developed. This methodology has been used to develop a computational tool for analysis and optimization of primary structural aircraft components. A wing spar design problem was used to demonstrate the effects of manufacturability and cost requirements on the optimal design configuration. By the use of the computational analysis tool that has been developed, physical programming is applied to the optimization phase of the design. The effectiveness of the physical programming method is demonstrated in the context of such complex problems. In the previous approach, the problem complexity necessitated the minimization of one objective at a time in conjunction with behavioral constraints. The associated Pareto hypersurface is not convex, and the employed approach did not allow the designer to explore the design space efficiently. The use of physical programming is explored for this class of complex problems and it is concluded that physical programming offers the formulation flexibility needed to obtain efficiently the desired points on the Pareto frontier. A comparison with the weighted sum method, as well as the previous results, is made.

Toward manufacturing and cost considerations in multidisciplinary aircraft design

This paper discusses the need for and demonstrates the challenges in the way of manufacturing and cost considerations in multidisciplinary aircraft design. A perspective view of multidisciplinary aircraft design optimization is presented. Several methods for addressing product quality and customer requirements early in aircraft design are discussed. A literature survey on concurrent engineering, manufacturing influence factors, and manufacturing cost models indicates substantial accomplishments. However, many unresolved issues with regard to methods for accurate prediction of manufacturing cost and determination of manufacturing complexity still remain that require further research.

Buckling and vibration analysis of composite sandwich plates with elastic rotational edge restraints

Thesmall-dee ectiontheorydevelopedforsimplysupportedorthotropicsandwichplatesisextendedfortheelastic buckling and free vibration analysis of anisotropic rectangular sandwich plates with edges elastically restrained againstrotation.Theplatedee ection andtransverseshearforcesarerepresentedby anindependentsetoffunctions that satisfy the essential boundary conditions for all and the natural boundary conditions for specie c cases. The Rayleigh‐Ritz method is used to solve for in-plane buckling loads and transverse natural frequencies through the solution ofaneigenvalueproblem. Thenumerical tablesincluded demonstratetheeffectsof elasticedgeconditions, aspectratio,andfacesheetplypatternonthebucklingloadsandnaturalfrequenciesofanisotropicsandwichplates.

Crashworthiness Optimisation of Vehicle Structures with Magnesium Alloy Parts

This paper explores the effects of replacing the baseline steel with lightweight magnesium alloy parts on crashworthiness characteristics and optimum design of a full-vehicle model. Full frontal, offset frontal and side crash simulations are performed on a validated 1996 Dodge Neon model using explicit nonlinear transient dynamic finite element analyses in LS-DYNA to obtain vehicle responses such as crash pulse, intrusion distance, peak acceleration and internal energy. Twenty-two parts of the vehicle body structure are converted into AZ31 magnesium alloy with adjustable wall thickness while the remaining parts are kept intact. The magnesium alloy material model follows a piecewise linear plasticity law considering separate tension and compression properties and maximum plastic strain failure criterion. Six different metamodelling techniques including optimised ensemble are developed and tuned for predictions of crash-induced responses within the design optimisation process. The crashworthiness optimisation problem is solved using the sequential quadratic programming method with most accurate surrogate models of structural responses considering both constrained single- and multi-objective formulations. The results show that under the combined crash scenarios with the selected material models and design constraints, the vehicle model with magnesium alloy parts can be optimised to maintain or improve its crashworthiness characteristics with up to 50% weight savings in the redesigned parts.

Process parameter optimization of lap joint fillet weld based on FEM-RSM-GA integration technique

A welding process design tool is proposed for arc welding parametric optimization.It is based on integrated Finite Element Method, Response Surface Method and Genetic Algorithms.Simulation based process parameter optimization is possible without expensive experiments.The method effectively determines optimum parameters for minimum distortion. This study introduces a welding process design tool to determine optimal arc welding process parameters based on Finite Element Method (FEM), Response Surface Method (RSM) and Genetic Algorithms (GA). Here, a sequentially integrated FEM-RSM-GA framework has been developed and implemented to reduce the weld induced distortion in the final welded structure. It efficiently incorporates finite element based numerical welding simulations to investigate the desired responses and the effect of design variables without expensive trial experiments. To demonstrate the effectiveness of the proposed methodology, a lap joint fillet weld specimen has been used in this paper. Four process parameters namely arc voltage, input current, welding speed and welding direction have been optimized to minimize the distortion of the structure. The optimization results revealed the effectiveness of the methodology for welding process design with reduced cost and time.

Integrated aerodynamic-structural-control wing design☆

Abstract The aerodynamic-structural-control design of a forward-swept composite wing for a high subsonic transport aircraft is considered. The structural analysis is based on a finite-element method. The aerodynamic calculations are based on a vortex-lattice method, and the control calculations are based on an output feed-back control law. The wing is designed for minimum weight subject to structural, performance/aerodynamic and control constraints. Efficient techniques are developed to calculate the control-deflection and control-effectiveness sensitivities which appear as second-order derivatives in the control constraint equations. To suppress the aeroelastic divergence of the forward-swept wing, and to minimize the take-off gross weight of the design aircraft, two separate cases are studied: (1) combined application of aeroelastic tailoring and active controls; and (2) aeroelastic tailoring alone. For the particular example problem considered in this study, the aeroelastic tailoring was found to have a substantially greater influence than active controls on weight minimization and divergence suppression.

Shape and Sizing Optimisation of Automotive Structures With Deterministic and Probabilistic Design Constraints

This paper presents the results of a study on the combined shape and sizing optimisation of automotive structures while examining the effects of different design constraints and associated uncertainties on reliability and efficiency of the optimum designs. Nonlinear transient dynamic finite element analysis is used for full- and offset-frontal crash simulations of a full vehicle model. Surrogate models are developed for the intrusion distance and peak acceleration responses at different vehicle locations based on the material and geometric characteristics of the rail component. The obtained solutions provide insight on the effect of uncertainties in optimum design of automotive structures.