Improvement of Tubular Linear Oscillating Actuators by Using End Ferromagnetic Pole Pieces

In this paper, an improved tubular Halbach surface-mounted permanent magnet (HSPM) linear oscillating actuators (LOAs) with end ferromagnetic pole pieces is proposed. Generally, the end magnet rings are exposed to air due to the inherent opening structure of LOA, resulting in a rather larger reluctance of end air gap and a lower air-gap flux density. Therefore, the analysis of the end air gap is of great significance for LOA performance. Considering this fact, the ferromagnetic pole pieces are added at both the ends of the support tube of LOA, trying to direct the magnetic fields in desired paths and enhance the electromagnetic performance of LOA. Two HSPM LOAs with ferromagnetic and without ferromagnetic pole pieces are simulated, built, and tested. The results show that the electromagnetic performance of the proposed design is superior to the original. Moreover, its cost and volume are approximately unchanged. The proposed design plays a significant role in enhancing LOA performance and efficiency.