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To meet the requirements of higher speeds, greater accuracies and improved reliability, direct linear drives are increasingly employed in new machine tools. In this paper, the modelling, control and monitoring of a direct linear drive for end milling are studied. First, a direct linear drive and its advantage are addressed; then, a dynamical model of the direct drive for end milling is proposed. Second, the friction and damping characteristic of the guideways and its relation to axis velocity and temperature as well as the cogging force of the drive resulting from the interaction of the primary (active) and secondary (passive or stator) part are analysed in detail. Third, possibilities to improve the motion behaviour of the direct linear drive by compensation of disturbances, friction and cogging forces are discussed, and a self-adjusting compensation controller and a state-space controller are proposed. Finally, a practical case demonstrates that the high-frequency cutting force can be tracked by the linear motor current. Then a tool breakage monitoring method by sensing linear motor current with a smoothing non-linear energy operator is proposed and tested with the practical case. [ABSTRACT FROM AUTHOR]

The systems for in-process quality assurance offer the possibility of estimating the workpiece quality during machining. Especially for finishing processes like grinding or turning of hardened steels, it is important to control the process continuously in order to avoid rejects and refinishing. This paper describes the use of on-line monitoring systems with process-integrated measurement of acoustic emission to evaluate hard turning and grinding processes. The correlation between acoustic emission signals and subsurface integrity is determined to analyse the progression of the processes and the workpiece quality.