Linear permanent magnet (PM) motors have increasingly been used in high-performance applications where high accuracy and fast dynamic response are required. However, the presence of cogging force in linear motors compromises position and speed control accuracy, which can be particularly troublesome at low speeds. This paper presents analysis and minimization of cogging force associated with a tubular PM motor with transverse flux configuration. An analytical criterion is brought forward, which allows the impact prediction of leading design parameters on the cogging force in an accurate way. And the validity and results are verified by extensive three-dimensional numerical computations and experimental measurements. It is shown that the cogging force increases along with the PM height. And it is highlighted that the cogging force amplitude is a sinusoidal function of the stator segment length, which is quite different from that in conventional PM machines. This work has provided a basis for cogging force reduction, and will aid the design process of the transverse flux motor, especially when targeting high-performance direct drive applications.

This paper investigates the performance of a magnetic lead screw (MLS) equipped with skewed arc magnets. Skewed arc magnets are adopted to approximate the helical ones, because the latter is hard to realize. Although similar method had been proposed in the previous literature, discussion about the parameters of the skewed arc magnets was insufficient and little attention was paid to the gear ratio of the resultant MLS. In this paper, the principle of approximation by skewed arc magnets is proposed and discussed, and the performance of the MLS with skewed arc magnets is evaluated and compared with the ideal MLS in terms of thrust force, torque, and gear ratio. It is highlighted that the gear ratio is the fundamental indicator of the MLS's performance, besides the thrust force and torque. It is shown that the gear ratio of MLS is mainly affected by the reference angle and the arc angle of skewed arc magnets, and optimal values for the two angles are obtained. In addition, the effects of the magnet magnetization on thrust force and torque are analyzed. Finally, dovetail budge and groove are introduced between the adjacent magnet segments for simpler fabrication.

Structural vibrations in modern buildings have been increasing concerns. If not properly controlled, they would give rise to serviceability problems and disturbances to occupants. The permanent magnet (PM) linear actuator-based active vibration mitigation strategy exhibits excellent dynamic performances on elimination of vibrations with complex modes, and has great potential. This paper describes modeling, design optimization, and numerical and experimental verifications of a PM linear actuator for structural vibration mitigation applications. Analytical expressions for prediction of the actuator performance are derived, and the linear actuator is then designed in optimization within a specific set of volumetric and thermal constraints in order to maximize the product of efficiency and power factor. It is shown that the proposed analytical model has provided a computationally efficient tool for design optimization, and the Halbach ratio and actuator width have significant impacts on the performance of the PM linear actuator. The results are validated by finite-element computations, and further verified by experimental measurements on a prototype actuator.

Launch efficiency has always been the focus of reluctance coil launchers research. In a traditional launch mode, the residual current in the drive coil creates a reverse force on the projectile. This is undesirable since the reverse force is in the opposite direction of movement, reducing the launch efficiency of the system. To address this problem, a multistage discharge circuit with the residual energy recovery and utilization mode is proposed in this article. As the projectile approaches the center of each stage of the drive coil, the current in the drive coil decays rapidly to zero by using the last stage capacitor to absorb the residual energy. The residual energy from the previous stages is eventually recovered by the last stage capacitor. This capacitor with residual energy is used to power the last stage drive coil of the reluctance coil launcher. This mode effectively suppresses the reverse force on the projectile and realizes the reuse of residual energy. Taking a four-stage reluctance coil launcher as an example, this article introduces the working principle of this mode in detail. The feasibility of the model is verified by finite-element simulation and experiments. Both simulation and experimental results show that this mode performs well in the recovery and reuse of residual energy and can effectively improve the launch efficiency of system.

The reluctance electromagnetic launchers mainly use the driving coils to generate high magnetic field to accelerate the ferromagnetic projectiles. Its advantages in accelerating large-mass projectiles have attracted considerable attention. However, during the projectile acceleration of conventional reluctance electromagnetic launchers, residual currents in the drive coils may produce opposing forces that reduce launch speed and efficiency. For this issue, an improved pulsed power supply circuit for reluctance electromagnetic launchers is proposed in this article based on a bridge-type capacitor circuit. The circuit can quickly reduce the residual current of the driving coil and recover the residual current energy. Since the circuit uses the same capacitor to power the drive coil and recover the remaining energy, the remaining energy recovered by the capacitor can be used as the initial energy storage for a new cycle. This can shorten the charging time for new cycles. In this article, the basic principle of the improved pulsed power supply circuit is introduced and analyzed in detail, and a comparative analysis is carried out with the traditional circuit through simulation. The results show that the new circuit has better characteristics in terms of residual energy recovery.

Launch efficiency is an important indicator to judge the performance of electromagnetic launchers. The goal of the conventional parameter optimization method for multistage launch is to maximize projectile kinetic energy in each stage acceleration. For reluctance coil launchers with residual recovery and utilization mode, the effect of the launcher parameters on the recovery energy should be considered in addition to the kinetic energy of the projectile. In this article, the feasibility of the model and the correctness of the original model are first verified by a four-stage launching experiment. Then, the influence of the drive coil parameters on the projectile acceleration and energy recovery is analyzed through theoretical analysis. In addition, a drive coil parameter optimization method for multistage reluctance coil launchers with residual energy recovery and utilization mode is proposed. By this method, the coil parameters of the original simulation model are optimized, and the simulation and experimental results before and after optimization are compared. The comparison results show that the optimization method proposed in this article integrates the relationship between projectile velocity and recovery energy, which can significantly improve the overall launch efficiency of the multistage system.