Design method and analysis of double-side air-core permanent magnet linear servo motor

Thrust ripple, caused by non-sinusoidal magnetic field and end effect, always deteriorates the servo characteristics of linear servo system. In this paper the magnetic field of the double-side air-core permanent magnet linear servo motor (DAPMLSM) was analyzed by equivalent magnetization intensity method (EMI). The formulas were proved accurate by finite element analysis (FEA) and experiments. Then they were used to analyze no-load magnetic harmonic to reduce thrust ripple. Then together with changing winding pitch and current input order, further more stable thrust was gained. And the thrust analysis indicated harmonics are mainly even, from non-sinusoidal magnetic field and end effect of linear motor. Finally the design laws of motor´s main dimensions, including windings, were discussed to obtain optimal sinusoidal magnet field and stable thrust.