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In this paper, a new approach to robust optimal design is proposed. The idea is to consider the sensitivity by means of two auxiliary criteria A and D, related to the magnitude and isotropy of the sensitivity, respectively. The optimal design of a switched-reluctance motor is considered as a case study: since the case study exhibits two design criteria, the relevant Pareto front is approximated by means of evolutionary computing.

Traditionally, the objective function used for optimizing the design of an internal permanent magnet motor (IPM) has maximized efficiency or torque for a particular current or volume. Creating a particular torque speed curve can be considered to be a multi-objective problem and would usually be expressed in terms of a single objective by minimizing the average error over the curve. In this paper, it is proposed to treat this directly as a multi-objective problem thus allowing the designer to decide which tradeoffs in the torque-speed performance are most acceptable after the analysis has been performed rather than before. Additionally, a new variant of a multi-objective evolutionary algorithm using mixed elitism, intended for this problem, is described. Index Terms--Genetic algorithms, optimization methods, permanent magnet motors.

Case-based reasoning (CBR) is an attractive approach to the design of electromagnetic (EM) devices because it draws upon experiential knowledge to tackle new problems. This paper presents a hybrid design model to represent the structural, behavioral, mathematical, and material information for a generic EM device. Using this representation method, a hierarchical case library can be constructed for the preliminary design of EM devices and act as input and design knowledge storage for a CBR-based creative design system. Index Terms--Case-based reasoning, electromagnetic (EM) devices, hybrid design model, preliminary design.

Several approaches exist for the evaluation of force distributions in electromagnetic devices. The local virtual work based stresses derived from the application of continuum design sensitivity analysis to the variation of system energy are equivalent to the traditional Maxwell stress tensor formulation in total force calculation. While both methods rely on local field values, they produce different force distributions for the same field. The paper reviews these results and examines the discrepancy due to the numerical errors in the field solution and the difference in the permeability of the material across the interface. Index Terms--Accuracy, design, force evaluation, numerical computation.

The use of soft magnetic composites (SMCs) provides electromagnetic device designers with serious challenges. While such materials have the potential of allowing novel 3-D topologies to be used, as well as providing major advantages in recycling at the end of the lifetime of the device, little or no design experience exists in this area. This paper proposes the use of sensitivity based topology optimization as a methodology for assisting designers in this task. Index Terms--Electrical machines, shape optimization, soft magnetic composites (SMC), topology optimization.