EPOCH parallel computing facilitates optimum product design

Oxford, 22 October 98 Industrial developers are facing a tremendous challenge to achieve the optimum design for products with regard to the ever increasing demands towards their electromagnetic features. Since January 1997, Vector Fields Ltd, a company specialised in software for electromagnetic design, is co-ordinating a two year Esprit funded project to offer full 2D and even 3D optimisation facilities on high performance computing and networking (HPCN) equipment to the industry. Partners such as Moulinex, Philips, and Ansaldo Energia will benefit as end-users from the EPOCH project results. Products including microwave ovens, Cathode Ray Tubes (CRT) for X-rays and TVs, thin film recording heads for videorecorders, bending magnets, permanent magnet brushless electric motors, and train brake systems are among the first applications to validate the design optimisation environment.

Electromagnetic Product Optimisation using Computers of High Performance constitutes the project's full name and exactly indicates the major objective. In order to offer industrial product developers a possibility to find the most adequate parameters for their design, the EPOCH Consortium aims at creating an open-ended, user-friendly optimisation software system. To allow realistic design times and to ensure portability between computer systems, the Bulk Synchronous Parallel (BSP) library, pioneered by Oxford Parallel, is being used. The BSP model also permits scheduling of processes and processors to make the most cost-effective use of the available HPCN hardware. BSP is mainly being directed at the most computationally intensive part of the design process, which is based on Vector Fields' Finite Element Method (FEM) electromagnetic analysis codes - ELEKTRA, SCALA, SOPRANO and TOSCA.

The three remaining partners provide essential software and algorithm development to the project. In this capacity, Labein enhances the EPOCH environment with Optimisation Manager and variational geometry software whereas the University of Genova supplies optimisation methods. In turn, the Ecole Centrale de Lille delivers Design of Experiments tools. In the Spring of 1998, the first 2D system version has been released. The Optimisation Manager stores a range of optimisation methods and Design of Experiments models, which correspond to the user's preferences. The designer first executes a manual pre-pass run through the selected software components to establish the sequence of pre-processing, solver and post-processing software applied to the design.

Subsequently, the Evaluation Manager defines the various steps and choices to have them run under script control during the optimisation process. During the optimisation of the design, geometric parameter changes are facilitated by the variational modelling system to provide a new, topologically consistent model. The software automatically generates a finite element mesh in accordance with the new sizes. By the end of 1998, the project team plans to integrate full 3D facilities. The Bulk Synchronous Parallel model is used to speed up the evaluation process by selecting the appropriate number of processors needed to minimise the calculation time. It is even possible to perform several evaluations simultaneously, if required. For this purpose, BSPlib provides check-pointing and process migration features to prevent failing or too heavily loaded processor nodes from slowing down the process.

The 2D EPOCH optimisation system has been tested with positive results in the delicate design of both thin film recording heads and Cathode Ray Tubes (CRT) for Philips. Since advanced video equipment contains a large amount of sensing equipment that may suffer interference from stray magnetic fields of the recording head, an important aspect of the electromagnetic design is minimisation of these conflicts. As for the CRT tubes, the EPOCH optimisation expects to be able to reduce the three weeks computing time on 10 to 15 workstations for a triode design by a factor of 10, thus bringing down the overall development period from one year to 1 or 2 months. The distribution of high frequency radiation in next generation microwave ovens has only recently been tackled by FEM computer analysis. The complex geometry of the device amounts to an enormous number of finite elements, largely exceeding the capacity of a single workstation.

The EPOCH team therefore decided to use simplified models to validate the efficiency of nodal based FEM analysis in the frequency domain. However, this method proved to be unsatisfactory and future investigations are now focusing on edge variable elements and finite difference time domain. Moulinex has however provided the team with an intermediate test case for high frequency modelling to explore the possible approaches to solve this difficult problem. Ansaldo Energia's contribution to EPOCH consisted in the complete design of a C-shaped bending magnet for a high energy colliding beam facility. With use of the Response Surface Method, the partners were able to optimise the homogeneity of the magnetic field in the air-gap, taking in account two sorts of variables, namely the current carried by the winding and the geometry.

The Ecole Centrale de Lille faced the EPOCH team with two challenges. The first one involved the design of an eddy current braking system for both high speed and conventional trains, which avoids any physical contact with the wheel of the train. The partners currently are studying the complex geometry design which appeared to turn out too expensive in an initial optimisation trial. The second problem relates to the development of a permanent magnet motor for an industrial fan. The flat and tiny device has to be inserted into the hub of the screw and must use a power supply of less than 50W. The first prototype has been successfully tested but the EPOCH team is still trying to improve the performance with the assistance of the design optimisation tool. For more details, we refer to the EPOCH home page.

Leslie Versweyveld