Optimisation of electromagnetic devices with uncertain parameters and tolerances in the design variables

The common approach to continuous and discrete optimisation problems in ele ctromagnetics does not take into account uncertainties and variations of th e design variables. Local sensitivity analysis is usually performed only af ter the optimisation run to study the behaviour of the objective function i n the neighbourhood of the optimum. However, this procedure may prove ineff icient if the optimum has to be rejected due to sensitivity considerations and a new run has then to be performed. In this paper an alternative approa ch, which takes into account uncertainties in the design variables and phys ical data, is presented, and an analytical function is used to highlight th e features of the proposed method, The essence of the technique is to coupl e the optimisation with a series of worst case analyses which are embedded in the optimisation loop. The method is fully general and can be applied to any optimisation method. The additional computational costs associated wit h the procedure maybe relatively high, but in the authors' opinion the obta ined gains in user confidence in the solution and the computational savings in some cases far offset the possible drawbacks of the method.