Meng Xia and Jan Sykulski
The purpose of this paper is to propose a novel methodology based on budget constrained Min-Cut theorem to solve constrained topology optimization (TO).
Abstract
Purpose
The purpose of this paper is to propose a novel methodology based on budget constrained Min-Cut theorem to solve constrained topology optimization (TO).
Design/methodology/approach
This paper establishes a weighted network with budget, which is derived from the sensitivity with respect to the constraint function. The total budget carried by the topology evaluates the extent to which the constraint is satisfied. By finding the Min-Cut under budget constraint in each step, the proposed method is able to solve constrained TO problem.
Findings
The results obtained from a magnetic actuator including a yoke, a coil and an armature have demonstrated that the proposed method is effective to solve constrained TO problem.
Originality/value
A novel methodology based on budget constrained Min-Cut is proposed to solve constrained TO problem.
Details
Keywords
Song Xiao, Yuanpei Luo, Jingchi Wu, Can Zhang, Yang Rao, Guangning Wu and Jan Sykulski
In high-speed trains, the energy is supplied from a high voltage catenary to the vehicle via a pantograph catenary system (PCS). Carbon pantograph strips must maintain continuous…
Abstract
Purpose
In high-speed trains, the energy is supplied from a high voltage catenary to the vehicle via a pantograph catenary system (PCS). Carbon pantograph strips must maintain continuous contact with the wire to ensure safety and reliability. The contact is often confined to a particular spot, resulting in excessive wear due to mechanical and thermal damage, exacerbated by the presence of an electric arc and associated electrochemical corrosion. The effectiveness and reliability of the PCS impacts on the performance and safety of HSTs, especially under high-speed conditions. To alleviate some of these adverse effects, this paper aims to propose a configuration where a circular PCS replaces the currently used pantograph strips.
Design/methodology/approach
Two dynamic multi-physics models of a traditional PCS with a carbon strip and a novel PCS with a circular pantograph strip catenary system are established, and the electrical and mechanical characteristics of these two systems are compared. Moreover, a PCS experimental platform is designed to verify the validity and accuracy of the multi-physics model.
Findings
A novel circular pantograph system is proposed in this paper to alleviate some of the shortcomings of the traditional PCS. Comparing with a traditional PCS, the circular PCS exhibits superior performance in both electromagnetic and thermal aspects.
Originality/value
The paper offers a new technical solution to the PCS and develops a dedicated multi-physics model for analysis and performance prediction with the aim to improve the performance of the PCS. The new system offers numerous benefits, such as less friction heat, better heat dispersion and improved catenary-tracking performance.
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Andrzej Demenko and Jan Sykulski
The aim of this paper is to develop network models of an electromagnetic field containing both eddy and displacement currents. The proposed network models provide good physical…
Abstract
Purpose
The aim of this paper is to develop network models of an electromagnetic field containing both eddy and displacement currents. The proposed network models provide good physical insight, help understanding of complicated electromagnetic phenomena and aid explanation of methods of analysis of electromagnetic systems.
Design/methodology/approach
The models consist of magnetic and electric networks coupled via sources. The analogy between the finite element method and the loop and nodal formulations of electric circuits is emphasised. The models include networks containing branches associated with element edges (edge networks) or facets (facet networks).
Findings
Methods of determining mmf sources of magnetic networks from loop and branch currents in electric circuits, as well as emf sources in electric networks on the basis of the rate of change of loop and branch fluxes in electric networks, have been carefully considered. The models are general and allow creation of networks of electromagnetic systems containing non‐homogenous materials and multiply‐connected conducting regions.
Originality/value
The presented analogies between the finite element formulation and the equivalent network models not only facilitate understanding of the methods of field analysis but also help to formulate efficient computational algorithms.
Details
Keywords
Rafal M. Wojciechowski, Andrzej Demenko and Jan K. Sykulski
The purpose of this paper is to develop a reluctance‐resistance network (RRN) formulation for determining the induced current distributions in a 3D space of multiply connected…
Abstract
Purpose
The purpose of this paper is to develop a reluctance‐resistance network (RRN) formulation for determining the induced current distributions in a 3D space of multiply connected conducting systems.
Design/methodology/approach
The proposed RRN method has been applied to solve Problem No. 7 of the International TEAM Workshops. The induced currents in the conductive plate with an asymmetrically situated “hole” have been analysed. The RRN equations have been formed by means of the finite element method using the magnetic vector potential A and the electric vector potentials T and T0. The block relaxation method combined with the Cholesky decomposition procedure has been applied to solve the resultant RRN equations.
Findings
Comparison with results published in literature has demonstrated high accuracy of the proposed RRN computational scheme while offering significant savings in computing times.
Originality/value
A novel formulation of the RRN approach has been proposed and demonstrated to be computationally efficient.
Details
Keywords
The purpose of this paper is threefold: to make explicitly clear the range of efficient multi‐objective optimization algorithms which are available with kriging; to demonstrate a…
Abstract
Purpose
The purpose of this paper is threefold: to make explicitly clear the range of efficient multi‐objective optimization algorithms which are available with kriging; to demonstrate a previously uninvestigated algorithm on an electromagnetic design problem; and to identify algorithms particularly worthy of investigation in this field.
Design/methodology/approach
The paper concentrates exclusively on scalarizing multi‐objective optimization algorithms. By reviewing the range of selection criteria based on kriging models for single‐objective optimization along with the range of methods available for transforming a multi‐objective optimization problem to a single‐objective problem, the family of scalarizing multi‐objective optimization algorithms is made explicitly clear.
Findings
One of the proposed algorithms is demonstrated on the multi‐objective design of an electron gun. It is able to identify efficiently an approximation to the Pareto‐optimal front.
Research limitations/implications
The algorithms proposed are applicable to unconstrained problems only. One future development is to incorporate constraint‐handling techniques from single‐objective optimization into the scalarizing algorithms.
Originality/value
A family of algorithms, most of which have not been explored before in the literature, is proposed. Algorithms of particular potential (utilizing the most promising developments in single‐objective optimization) are identified.
Details
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Andrzej Demenko and Jan. K. Sykulski
The purpose of this paper is to emphasise the analogies between variational and network formulations using geometrical forms, with the purpose of developing alternative but…
Abstract
Purpose
The purpose of this paper is to emphasise the analogies between variational and network formulations using geometrical forms, with the purpose of developing alternative but otherwise equivalent derivations of the finite element (FE) method.
Design/methodology/approach
FE equations for electromagnetic fields are examined, in particular nodal elements using scalar potential formulation and edge elements for vector potential formulation.
Findings
It is shown how the equations usually obtained via variational approach may be more conveniently derived using integral methods, employing a geometrical description of the interpolating functions of edge and facet elements. Moreover, the resultant equations describe the equivalent multi‐branch circuit models.
Originality/value
The approach proposed in the paper explores the analogy of the FE formulation to loop or nodal magnetic or electric networks and has been shown to be very beneficial in teaching, especially to students well familiar with circuit methods. The presented methods are also helpful when formulating classical network models. Finally, for the first time, the geometrical forms of edge and facet element functions have been demonstrated.
Details
Keywords
Song Xiao, Mihai Rotaru and Jan K. Sykulski
Design optimisation of electromagnetic devices is computationally expensive as use of finite element or similar codes is normally required. Thus, one of the objectives is to have…
Abstract
Purpose
Design optimisation of electromagnetic devices is computationally expensive as use of finite element or similar codes is normally required. Thus, one of the objectives is to have efficient algorithms minimising the number of necessary function calls. In such algorithms a balance between exploration and exploitation needs to be found not to miss the global optimum but at the same time to make efficient use of information already found. The purpose of this paper is a contribute to the search of such efficient algorithms.
Design/methodology/approach
This paper discusses the use of kriging surrogate modelling in multiobjective design optimisation in electromagnetics. The investigation relies on the use of special test functions.
Findings
The importance of achieving appropriate balance between exploration and exploitation is emphasised when searching for the global optimum. New strategies are proposed using kriging.
Originality/value
It is argued that the proposed approach will yield a procedure to solve time consuming electromagnetic design problems efficiently and will also assist the decision making process to achieve a robust design of practical devices considering tolerances and uncertainties.
Details
Keywords
Andrzej Demenko and Jan Sykulski
Numerical three-dimensional formulations using vector potential A have been examined for magnetic fields, with emphasis on the finite difference (FDM) and edge element (EEM…
Abstract
Purpose
Numerical three-dimensional formulations using vector potential A have been examined for magnetic fields, with emphasis on the finite difference (FDM) and edge element (EEM) methods, with the view to establish common features. The paper aims to discuss these issues.
Design/methodology/approach
It has been shown that for hexahedral elements the FDM equations may be presented in the form similar to the EEM equations, providing the products of the nodal potentials and distances between the nodes are used as unknowns in FDM, instead of the usual nodal potentials.
Findings
The analogy between the FDM and the EEM approach has been established.
Originality/value
It has been demonstrated, following from this and previous publications, that analogy exists between all fundamental methods of field solutions relying on space discretisation. This is helpful in terms of classification of the methods and aids the understanding of physical processes involved.