This paper presents the theoretical analysis and numerical modeling of various cogging torque suppression methods of the slotted limited angle torque motor(LATM). The relationship between the cogging torque, the output characteristics and the structure parameters of new methods is revealed by derived equations and finite element analysis(FEA), which provides a theoretical basis for the optimization of the slotted LATM. The effectiveness of the best suppression method is verified by the prototype experiment. In addition, a method to predict torque distortion caused by armature reaction is proposed, and it is verified by finite element simulation and prototype experiment.

Low force ripples from permanent magnet linear motors (PMLMs) are typically essential requirements in a wide range of demanding control applications with high motion quality. Apart from the sources present in rotary PM machines, phase unbalance due to the end effect is another major contributor of the thrust force ripples in the PMLMs. In this paper, the phase unbalance and induced force ripples are investigated in the case of a planar PMLM typically equipped with single-layer concentrated windings and quasi-Halbach magnets. It demonstrates that although the PMLM is quite carefully deigned to minimize the end effect, the phase unbalance still exists, including both the amplitude and phase position unbalances. And the phase unbalances give rise to even order force ripple harmonics, in which the 2 ^nd -order force ripple is particularly significant. In order to compensate the end effect and the unbalance between the three phases, a novel PMLM topology is presented, in which the width of the two end teeth (instead of the edge teeth) is adjusted to reduce the force ripple. And the impact of the end teeth width on the ripple force magnitude is further revealed. It is shown that by proper design of the end teeth width, the 2 ^nd -order force ripple of the PMLM can be minimized to quite a low extent. In comparison with the original design, the 2 ^nd -order force ripple factor of the novel topology has been suppressed from 0.4% to less than 0.03% in the case study. Such a technique has provided a new way of force ripple minimization, and is applicable to other types of linear motors or actuators with appropriate changes.

This paper presents the theoretical analysis, numerical modeling and experimental verification of a novel limited angle torque motor (LATM) with an irregular slot number. Based on the magnetic circuit, analytical equations are derived for predicting the torque-angle characteristic of the LATM, including both the constant torque region and linear region. By these equations, the relationship between the performance and leading parameters is established, providing a reference for the quick design of LATM. The idea of utilizing the linear region to expand the angular operation range of LATM is then proposed. It is shown that by active control of the winding current, the linear region can be reasonably used. Due to larger cogging torque in the integral-slot LATM, an irregular slot number topology is proposed to suppress the cogging torque. The results are validated by finite element analysis, and further verified by experimental measurements on a prototype machine.

In the development of more-electric aircraft, the motors with high torque density and specific power are required within the weight restriction. In this article, a novel hybrid axial transverse flux permanent magnet motor (HATF-PMM) is proposed with compound permanent magnet (PM) rotor, which exhibits great torque capacity to satisfy the requirement in more-electric aircraft. The method of electromagnetic characteristic superposition is highlighted in this article for the first time to decouple the magnetic field and reduce dimensionality. Considering the calculating time and accuracy, an analytical model based on the subdomain method is utilized to calculate the magnetic field of the proposed HATF-PMM and further obtain the electromagnetic characteristics, which is verified by finite-element analysis (FEA). Then, the HATF-PMM is optimized with the objective of high specific power by using the analytical model. In the end, the analysis results and performance of the proposed HATF-PMM are validated by the prototype experiment, which proves that the HATF-PMM has great potential in the application of more-electric aircraft.

A modified model of a limited‐angle torque motor (LATM) with irregular slot numbers is proposed for developing an operational range extension method for LATMs. The modified model is derived by considering the effects of the asymmetrical winding structure and magnetic flux leakage, which are validated by finite element analysis and experimental measurements. Based on the modified model, accuracy and time consumption of the simulation can be improved. For the operational range extension method, extended angle range selection theory and constraint conditions are proposed, and the relationship between the sinusoidal tracking characteristic and leading parameters is established by theoretical analysis. A simulation and a prototype machine experiment on an LATM using the new method are carried out. The results show that the proposed operational range extension method can reduce the weight and volume of the LATM without changing sinusoidal tracking characteristics, which proves the feasibility of applying the new method in the oscillating scan system to realize lightness and miniaturisation of the system.