This article proposes a hybrid-excited vernier reluctance linear machine (HEVRLM) with slot Halbach permanent magnet (PM) arrays. By utilizing Halbach PM arrays, leakage flux that exists in the consequent pole structure can be greatly reduced. Besides, the dc excitation can enhance both the flux regulation capability and the force density. First, the machine topology and working principle are introduced. Then, a magnetomotive force and permeance model is established to analytically calculate the air-gap flux density under hybrid excitation. Moreover, the flux regulation capability, thrust force characteristic, and PM demagnetization risk of the proposed machine are comparatively studied based on the finite-element method. It shows that Halbach PM arrays can effectively reduce the leakage flux and further significantly improve the thrust force density by more than 30%. In addition, hybrid excitation is a feasible approach to further improve the thrust force density by distributing the optimal dc and ac currents. Moreover, the proposed HEVRLM exhibits high thrust force density compared with the other three types of hybrid-excited linear machines. Finally, a prototype of HEVRLM is manufactured and tested for experimental validation.

In order to provide the general guidance in constructing the novel modular machines with redundant teeth, the available slot and pole number combinations based on the balanced conditions are summarized in this paper. After the brief review of the machine structure, the general slot and pole number combinations are listed: Firstly, the conventional modular machines used to construct the proposed modular machines need to possess integer times of 3 repetitive machine units. Each machine unit should construct as a 3-phase type. Then, a redundant machine unit providing the redundant teeth for modularity is necessary. This redundant machine only has one pole pair to make sure the space waste is minimal. The slot number of this redundant machine is determined by the greatest common divisor of the slot and pole pair numbers of the conventional modular machine. Finally, the combination of the conventional modular machine and the redundant one generates the proposed modular machine. In order to clearly illustrate the influence of slot and pole number combinations on machine performance, four combinations are chosen as examples to be compared. A 42-slot/32-pole machine is prototyped and tested to validate the analyses.

This article investigates the detent force optimization of a modular permanent-magnet linear synchronous motor (MPMLSM). First, the topology structure of a 6-slot/5-pole MPMLSM is introduced, which primary consists of eight modules. Second, the detent force harmonics feature is analyzed including its two components, cogging force and end force. Third, the effects of decoupling optimized method of optimized cogging force and detent force separately and the modulation optimized method of directly optimized detent force are investigated. Combining the modulation method and skewed permanent magnets, a flow chart of fast optimization is proposed for detent force reduction. Fourth, the MPMLSM is optimized by the proposed method, which second harmonic of the detent force has been reduced to 0.41 N, and the peak-to-peak value of the detent force is optimized to 0.94 N. Finally, a prototype is made and tested. The experimental results verify the effectiveness of the proposed fast optimization method, which is applicable to PMLSM with any close slot-pole combination.

The ironless permanent magnet linear synchronous motor (ILPMLSM) with non-overlapping windings is widely used in precise applications due to its simple structure, low thrust ripple and fast response, while the disadvantage is low thrust density. The novel asymmetrical double-layer winding ILPMLSM (DW-ILPMLSM) with quasi-Halbach magnets can improve the thrust density while keeping simple structure. However, the double-layer windings are asymmetric and the primary has finite length. To solve the problem of this asymmetry and investigate its influences on electromagnetic characteristics, an improved two-dimensional (2-D) analytical model is proposed, which introduces “virtual periodic primary” and solves the magnetic field of each winding layer. By the results of Finite Element (FE) and experiments, the proposed analytical model is verified. Moreover, the analytical model requires less computation time, which is helpful for optimizing design of this motor.

Permanent magnet linear synchronous machine (PMLSM) has the inherent drawbacks of end effect which would cause phase winding asymmetry, viz., electromagnetic parameter asymmetry (EMPA). In order to achieve fast and precise thrust response, traditional deadbeat direct thrust control (DB-DTC) is suitable for PMLSM, however it cannot be directly applied to PMLSM since it is constructed based on symmetrical machine mathematical model. Moreover, if EMPA is considered in traditional DB-DTC strategy, it is hard to calculate the required change of load angle since the primary flux linkage should be kept constant, especially when the salient-pole effect exists. Based on this, this paper proposed a simple modified DB-DTC strategy for a salient-pole PMLSM considering EMPA. Firstly, the mathematical model with and without considering asymmetrical inductance are derived. Then the influence of EMPA on traditional deadbeat direct thrust control (DB-DTC) is fully investigated. In order to compensate the effect of EMPA, this paper proposes a simple modified DB-DTC by compensating the error in both prediction and deadbeat control processes. Finally, the prototype experiments are carried out to validate the proposed control strategy. The results show that the phase current unbalance that caused by EMPA is largely suppressed controlled with the proposed control strategy. Moreover, both good steady and transient performances can be obtained compared with traditional DB-DTC strategy. The effectiveness of the proposed control strategy is validated.

This article proposes an improved analytical model of slotted linear permanent magnet synchronous machines (LPMSMs) to fast and accurately obtain the magnetic field distribution and detent force. Considering the secondary end effect can optimize the thrust performance in terms of machine control, while there are few research works focusing on this study. Combined with the periodic extension method, both the primary and secondary end effects are taken into consideration, which is the major contribution of this article. The analytical model containing seven subdomains (SDs) is conducted in Cartesian coordinates. The magnetic distributions in air-gap, slots, and end regions are obtained by solving Maxwell equations with various interface conditions. The thrust and normal forces are subsequently calculated based on the Maxwell stress tensor. The corresponding finite element (FE) model produces numerical results to validate the analytical results. A prototype is manufactured and tested. The experimental results show that the improved analytical model is accurate and efficient in no-load performance calculation. The investigation shows that this proposed method can be applied to all of the LPMSMs with similar structures.