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In this article, a high-precision equivalent magnetic circuit (EMC) model is first proposed for slotted permanent-magnet (PM) limited-angle torque motor (LATM) with nonuniform teeth, which leads to potential application in swing system substituting a lower torque density of the slotless structure. By the proposed relatively fine division method of magnetic reluctance in the stator tooth-tip segments, air-gap regions, and PM poles, the proposed EMC model can fully consider armature reaction and magnetic saturation problem. Subsequently, a multiobjective optimization method based on the EMC model is proposed to improve torque performance. Finite-element analysis is employed to validate the EMC model and optimization results. Following that, a curved nonwounded tooth shape is carried out and further optimized to decrease magnetic saturation of stator teeth and significantly improve symmetry of torque profile about stable equilibrium point, compared with the traditional straight tooth shape. Finally, the slotted LATM with curved teeth is prototyped, and its experimental results are presented and discussed. The simulation and experimental data show better accuracy of torque profile improvement.

Due to stator magnetic saturation and inherent cogging torque, the slotted limited angle torque motor (LATM) performs large torque ripple within its operation range, resulting in vibration noise and complex control problem. The novelty of this article is to not only first to apply 1J22 soft magnetic alloy (SMA) in the LATM but also to propose a multiobjective optimization method to improve the torque performances including torque ripple, cogging torque, and output torque, based on genetic algorithm (GA). First, 1J22 SMA is applied to the LATM to reduce the torque ripple caused by magnetic field saturation. Then, through the sensitivity analysis, weight coefficients of the related parameters of stator tooth for the optimization process are obtained. Besides, in order to optimize torque performances, the multiobjective optimization process is carried out and the GA is used to obtain the desired objective. Finally, the finite-element analysis (FEA) is used to validate the optimization design.

Nonlinear mathematical model (NMM) of limited-angle torque motor (LATM) is rarely studied at present because its operating principle is different from conventional rotating electrical machines. In this article, inspired by the NMM of rotating electrical machines, a high-fidelity and computationally efficient model of LATM is proposed, which can completely consider the nonlinear effects, including the electromagnetic torque, flux linkage, and inductance variation with current and rotor position due to magnetic saturation in the stator core. Different from the field-circuit coupling approach (FCCA) considering nonlinear effects, the proposed model exhibits higher computational efficiency since a finite element analysis (FEA) is not involved in the time-stepping simulation. Based on the high-fidelity model, an LATM position-tracking system model is built to simulate the real operation of the LATM system, which provides an accurate means of assessing the position-tracking performance without the actual test platform. The high fidelity of the proposed LATM model is validated by both the FCCA and experimental results.

Although conventional slotted limited-angle torque motors (LATMs) have a high torque density, its fatal shortcoming of non-uniform torque profile makes it difficult to apply for precise positioning systems. This paper presents a novel radial-flux slotted LATM with asymmetrical teeth for the torque performance improvement including average output torque and angular operation range. A magnetic equivalent circuit (MEC) for radial-flux slotted LATMs is first derived and implemented in the design process. Then, the finite-element analysis is utilized to validate the related analytical equations and to make the comparison of the torque performance between the radial-flux conventional and proposed LATMs. Finally, a prototype machine of the proposed LATM is accomplished, and its torque characteristic experiment is carried out to confirm the torque performance improvement. The related experimental results are presented and discussed.

This paper proposes an improved analysis method in consideration of the relationship between temperature rise and electromagnetic performance. The heat sources of the motor can be investigated by electromagnetic analysis. And the calculation results of electric power losses are brought into the fluid-thermal field analysis as the heat sources. Using iterative computations, the relevant parameters of the motor are updated according to the results of thermal field calculation until the calculation errors of the torque and temperature rise meet the requirements. In order to investigate the accuracy of the proposed analysis method, a 16 poles-24 slots interior permanent magnet (IPM) motor with water cooling is analyzed by finite element method. The results indicate that the coupling method can evaluate and predict the performances of the motor accurately.

Magnetic saturation problems and cogging torque normally result in a weak torque performance of conventional slotted limited-angle torque motors (LATMs). This paper presents a novel radial-flux slotted LATM with a tapered tooth-tip to improve the torque performance including average output torque and angular operation range. Firstly, the topology of tapered tooth-tip is analyzed and illustrated. Then, finite-element analysis is employed to compare the proposed LATM with the conventional slotted LATM. The comparisons of two topologies are concentrated in the air-gap flux density, cogging torque, back EMF, and output torque. Moreover, the influence of armature reaction on output torque is investigated. Finally, both conventional and proposed slotted LATMs are designed and prototyped. Torque characteristic experiments are carried out to confirm the torque capacity improvement of the proposed slotted LATM. Related experiment results are presented and discussed.

This paper presents a novel limited-angle torque motor (LATM) with a moving coil for oscillating mirror system. The proposed LATM has a constant torque coefficient over its operation range, rapid dynamic response, and easy mounting oscillating mirror owing to a special structure of the stator and the rotor. In design process, some design equations are derived to analyze toque coefficient, moment of inertia, and other parameters of the LATM. A novel optimization approach is carried out to obtain the maximum torque/moment of inertia ratio in consideration of the stator outer diameter and volume limitations. Coil parameters have also been optimized by this method so that a less time constant can be obtained. In addition, 3-D finite-element analysis is performed for verifying the proposed optimization method. Finally, a prototype machine is accomplished and its experimental results are presented and discussed. Meanwhile, a conventional position closed loop system of the LATM is established to validate the dynamic performance of the LATM.

This paper focuses on the study of torque model for permanent magnet synchronous machines (PMSMs). An improved torque model is derived strictly according to the assumption of ideal machines. In order to investigate the accuracy of the model, the previous and improved models are studied on a fractional slot concentrated winding (FSCW) 20-pole/24-slot and a distributed winding (DW) 20-pole/60-slot inset-SPM machines by finite element method (FEM). The two kinds of machines are analyzed on stator MMFs and inductances to study the differences between them. Furthermore the linear, nonlinear and zero-consequence problems are investigated. It can be concluded that the torque model is more suit for the DW PMSMs with more slots operating without zero-consequence current.

This paper presents an analytical method for estimating the maximum angular operation range (MAOR) in a permanent-magnet slotted limited-angle torque motor (LATM). The operating principle of three topologies is analyzed and discussed, including a toroidal LATM, a slotted LATM with common pole/slot combination, and a slotted LATM with special pole/slot combination. The analysis indicates that no effective methods have been proposed to estimate the MAOR for a slotted LATM with special pole/slot combination. Hence, this paper is focused on solving this problem. The results obtained from the analytical method are validated by a finite-element (FE) method. The average time of the proposed method takes far less than that of an FE method, so that the design cycle of LATMs can be shortened. Finally, two prototype machines are manufactured, and their experimental results are presented and discussed. The FE and experimental results validate the accuracy of an analytical method.

This paper presents a novel slotless limited-angle torque motor (LATM) for reaction wheels torque measurement system. The proposed slotless LATM has a uniform torque profile during its operating range, constant torque coefficient owing to avoiding saturation in back iron core. The slotless LATM has been designed and optimized using both magnetic circuit method and 2-D FE method. A scheme of magnetic pole spliced by three segments is proposed to improve flat width of air-gap flux density and torque performance. Finally, a prototype machine is established and its experimental results are presented and discussed. The theoretical and numerical results are validated with the experiments in the same operating conditions.