Thrust Ripple Reduction of Permanent Magnet Linear Synchronous Motor Based on Improved Pole Shape for Electromagnetic Launcher System

In this paper, a new design of permanent magnet linear synchronous motor (PMLSM) for electromagnetic launcher system (EMLs) has been investigated in terms of the requisite amount of average launching thrust force and thrust force ripple minimization through finite element method. EMLs are a kind of technology used to develop thrust force and launch heavy loads with different applications including military, aerospace, and civil applications. A linear motor as a major part of the system plays a substantial role in this application providing sufficient load launch force. Cogging force and its mitigation techniques are principle challenges in linear motor operation leading to thrust ripples and detrimental effects on positioning precision and dynamic performance of the moving part. In the proposed design, some modifications have been made in the conventional PMLSM structure. Semi-closed slot construction is used for the primary and the pole shoes width has been changed to access minimum thrust ripple value. In order to attain further optimization in PMLSM’s thrust ripple profile, some other modifications have been considered in PM’s shape as arc-shaped magnetic poles. The latter assists to enforce air gap flux density distribution as sinusoidal as possible, and makes further ripple reduction. The results exhibit that the proposed structure has low weight and it is more economical compared to conventional PMLSM with rectangular shape magnet. In addition, the Average thrust force and ripple are improved providing suitable thrust force for throwing the load.