Abstract：Iron core permanent magnet linear synchronous motor (PMLSM) is widely used in semicon- ductor processing, precision machine tools, and flexible logistics lines that require high-performance linear motions. It has the advantages of high speed, large thrust force, and high thrust force density. However, due to the two broken ends of the structure, the asymmetry of the magnetic circuit causes large thrust ripple, and reducing thrust ripple has become the main objective of optimization design. Usually, the thrust ripple at no-load (detent force) is chosen as the research object. This paper reviews the three methods for calculating the detent force and discusses how to consider the core saturation, cogging effect, and end effect. Then, the suppression methods of detent force are summarized from two aspects of motor structure optimization and control strategy. In addition, the existing problems and limitations of detent force research are pointed out. The development trends of detent force research are predicted. Firstly, the characteristics and principal components of detent force for an iron-core PMLSM with short primary and short secondary are introduced. For short primary structure, the a-slot PMLSM with all-teeth wound contains a+1 slots due to the broken ends, resulting in the cogging force containing 2nd and 4th harmonic components when taking 2τp (τp is pole pitch) as the fundamental wavelength. The detent force of PMLSM with short secondary operating in the non-end region of the primary contains the teeth harmonic component, similar to the cogging torque of a rotating motor. Secondly, three analysis methods of the detent force are introduced, which are the analytical method, the magnetic network method, and the finite element method. To consider the slotting and end effects, the exact subdomain method and the conformal mapping method are proposed based on the traditional subdomain method. However, the magnetic saturation is ignored. The magnetic network method considers the nonlinearity of iron properties by iterative calculation, taking into account slotting and end effects through the magnetic circuit division method and the mesh generation method. The finite element method is the most widely used numerical method. It has high accuracy, but needs a long computing time with accurate meshing. Thirdly, the suppression technology for the detent force is summarized from two aspects: motor design and motor control. In motor design, the optimization methods can be divided into two kinds. One is separating and decreasing the cogging force and end force, and the other is directly weakening the detent force, considering the coupling effect between the cogging force and end force. The latter is more effective in suppressing the detent force. The methods include end-reversed slots, shifting one of the primary components, unequal slot width design, and auxiliary teeth modulation. Most of them are only suitable for double-sided PMLSM. For motor control, the optimization methods of weakening detent force can be divided into compensation methods with and without the mathematical model of detent force. However, the design with the optimal detent force is not optimal for thrust ripple at load, especially under overload conditions. Thus, taking the thrust ripple at load as an optimization objective is needed. The development trends of detent force research for PMLSM are as follows: (1) Exact analytical model considering core saturation effect. (2) Efficient thrust ripple suppression technologies combined with actual load conditions. (3) System-level thrust ripple suppression optimization combined with structural design and control strategies for high precision control requirements.
吴丽泽, 李焱鑫, 卢琴芬. 有铁心永磁直线同步电机定位力分析与抑制技术综述[J]. 电工技术学报, 2025, 40(24): 7918-7935.
Wu Lize, Li Yanxin, Lu Qinfen. Overview on Analysis and Suppression Techniques of Detent Force for Iron-Core Permanent Magnet Linear Synchronous Motor. Transactions of China Electrotechnical Society, 2025, 40(24): 7918-7935.
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