Low Frequency Axial Flux Linear Oscillating Electric Drive Suitable for Short Strokes

The design, analysis, and control methodology of an energy efficient and high force to weight ratio rare earth N42 NdFeB based permanent magnet linear oscillating motor has been described. For this axial flux machine the mover is consisting of Aluminium structure embedded with rare earth permanent magnets of high energy density. Microcontroller based drive is developed for frequency and thrust control of the machine. Finite element method using FEMM is employed for analysis of various performance parameters of machine. The same parameters are also compared with the measured ones, which yields a good agreement to the proposed design. 1. Introduction Permanent magnet linear oscillating motors (PMLOMs) are finding increased suitability for many applications [1–3]. These motors require accurate oscillating/reciprocating characteristics for high precision application. Also the power requirements for these motors play an important role from efficiency point of view. The use of linear reluctance motors is already studied [2] under alternating current and also with direct current supply [3, 4]. The d.c. motors are having negligible core losses and therefore show higher efficiency than the a.c. ones, although the a.c. motors are employed in many applications [3]. The a.c. motors are used in pumps and many linear actuators [5]. The linear oscillating motors (LOMs) differ in terms and technologies as well as construction [3] from their rotating counterparts. The motors with the small oscillating frequency but high stroke length are used as a shuttle power drive for looms (in the textile industry) or as electric hammers. In [1, 3] the different applications for low frequency operation are given. In [6, 7] magnetic field analysis for tubular motors has been presented for mostly flat induction motors. In [5, 8, 9] the field circuit models have also been applied for simulation of dynamic characteristics of the tubular motors. However, the investigations did not include the permanent magnet axial flux type linear oscillating motors (PMLOMs). The short stroke oscillators are mainly applicable in water pumps. These motors work relatively at higher frequencies. The proposed motor as given in this paper is suitable for short stroke and low frequency application from 0 to 5？Hz. This machine has applicability for the development of heart pump with adjustable stroke frequency and thrust force. In the present work, the field calculations of the PMLOMs and their speed and thrust control techniques are presented. In formulated motion and electrical circuit equations, the