Development and analysis of two alternative tubular linear motors for use in machine tools

The manufacturing industry is relying on faster and more accurate positioning systems in machine tools to meet the increasing demand of higher machining tolerances. Improvements in positional accuracy, smoother velocity control at low speeds and higher bandwidth in speed and acceleration have been the focus of many researchers over recent years. This thesis is concerned with the modelling and development of two different high precision tubular linear synchronous motors which are potential alternative direct drive actuators in present day machine tools. The investigations include the analysis, design, manufacturability and control of a slotless Permanent Magnet Tubular Linear Motor (PMTLM) and a Synchronous Reluctance Tubular Linear Motor (SyncRTLM) through appropriate modelling, construction and experimental validation. The most significant contributions of this thesis are: • The analysis of the cogging force in the PMTLM taking into account the finite length of the stator. An appropriate model is developed using Finite Element Analysis (FEA) tools and experimentally verified. • The SyncRTLM with a laminated stator is modelled and experimentally verified for the first time. The tubular topology gives rise to a number of unique and novel optimisations which are presented in this thesis. • A novel commutation technique for the SyncRTLM is developed and customised code is developed in an industrial controller to achieve accurate servo control. • Two innovative manufacturing techniques were developed, one to facilitate the manufacture of the magnet structure for the PMTLM, and one which enables practical production of the SyncRTLM anisotropic stator. FEA models of the two motors including simulations of the force characteristics are presented. Experimental validations of the FEA analyses are carried out. Proposals for construction and manufacturing techniques for the motor production are also given