Mingna Ma

Analysis and Design of Moving-Magnet-Type Linear Synchronous Motor for Electromagnetic Launch System

The replacement of steam catapults with electromagnetic ones is becoming an overwhelming trend in aircraft launch systems. Recently, the double-sided linear launcher has attracted more and more attention from researchers. This paper presents the design and analysis of the moving-magnet-type permanent-magnet linear synchronous motor (PMLSM). The thrust density is the most important indicator for a powerful motor, so an analytical expression of the thrust-density coefficient is derived from basic electromagnetic force laws. Based on the analytical results, the thrust and the thrust ripple are analyzed using the finite element method in different conditions. In order to modularize easily, the ring windings have been applied in the double-sided PMLSM, and then, the design features and parameter optimization of the windings are discussed. This paper can provide references to select the suitable type of motor for the launch systems and accomplish the fundamental work for the design of a prototype.

Analysis and Optimization of Slotless Electromagnetic Linear Launcher for Space Use

As the exploitation of astrospace deepens, many new types of space-based electromagnetic launchers (EMLs) have aroused wide attention and discussions. Compared with traditional slotted electromagnetic linear launchers, a slotless-plate permanent-magnet linear synchronous motor can easily meet demands such as flexible structure, light weight, and high control precision for space use. This paper analyzes the magnetic field of the slotless inverted-U structure based on the equivalent-magnetizing-current method. The validity of this technique for integral-slot configuration is confirmed with finite-element analysis. Then, the influence of the main design parameters is investigated, and design optimization guides are established for the selection of the key design parameters. To reach the suitable air-gap flux density here, some new constructional optimization details are discussed. Design optimization is also performed to fulfill enough thrust for the EML system.

Design and analysis of ironless linear electromagnetic launcher with high thrust density for space platform

As further research on space exploration and space platform technology, space-based electromagnetic launchers (EML) have aroused widespread attention and interest. This paper presents analysis and optimization of ironless permanent magnet linear synchronous motor (ILPMLSM) which easily meet requirements such as fast response, light weight, small volume and high precision positioning for space-based EML. Electromotive thrust and thrust per volume of ILPMLSM with non-overlapping and overlapping air-cored windings are compared based on the analysis of the magnetic field. It is shown that the overlapping winding machine has certain important advantages compared to the non-overlapping winding machine for space platform. Further, we propose a design optimization to improve thrust density and thrust ripple simultaneously by optimizing structure and dimensions of magnets and windings.The design optimization is verified by 2-D Finite Element analysis.

Influence of Longitudinal End-Effects on Electromagnetic Performance of a Permanent Magnet Slotless Linear Launcher

Longitudinal end-effects seriously affect the electromagnetic performance of linear motor especially for large volume devices such as electromagnetic launchers. So, the purpose of this paper is to study longitudinal end-effects in a permanent magnet (PM) slotless linear launcher and proposes some measures for improvement. The longitudinal end-effects induced by finite length of PM mover can give rise to two mechanisms, uneven airgap magnetic field and partial saturation. The splitting edge magnets method is used to improve the uniformity of flux distribution, and it is also beneficial for enhancing thrust. In addition, we focus on asymmetrical phase characteristics stemming from finite stator part with distributed windings. Its influence on thrust and thrust ripple are investigated based on symmetrical component and energy method. The comprehensive analyses are established to aid initial design and assessment of performance for PM slotless linear launcher.

A position error compensation way for sensorless linear motor drive using high frequency injection

This paper presents a method of improving sensorless control based on the high frequency injection (HFI) for linear motor. The d- and q-axis incremental self- and mutual-inductance are determined by finite element analysis. The estimated mover position error caused by the cross-coupling magnetic saturation between the d- and q-axis is quantitatively analyzed. The error caused by filters in a HFI system is analyzed based upon filter group delay theory. A simple-to-design on-line compensation method is proposed based upon filters and cross-coupling magnetic saturation in a HFI system, which minimizes the position error. Finally, the simulation and experiment show a significant improvement in the accuracy of the mover position estimation.

Influence of longitudinal end effects on electromagnetic performance of an permanent magnet slotless linear launcher

Linear motor has the distinctive feature of structurally limited primary and secondary length, which causes longitudinal end effects in actual operation. And this phenomenon will seriously affect the electromagnetic performance of linear motor especially for large volume devices such as electromagnetic launchers. So the purpose of this paper is to study longitudinal end effects in an interior permanent magnet (PM) slotless linear launcher and proposes some measures for improvement. The longitudinal end effects induced by finite PM secondary can give rise to two mechanisms, uneven airgap magnetic field and partial saturation. The splitting edge magnets method is used to improve the uniformity of flux distribution, and it is also beneficial for enhancing thrust. In addition, we focus on unbalanced phase characteristics stemming from finite primary part in slotless motor with distributed windings. The influence of unbalance inductance on thrust and thrust ripple are investigative based on symmetrical component and energy method. The comprehensive analyses are established to aid the initial design and assessment of performance for PM slotless linear launcher.

Electromagnetic force characteristics in long-stator PM linear launcher with non-ideal mechanical air gap condition

The designs of long-stator permanent magnet (PM) linear launcher are widely adopted modular segments to simplify system and reduce energy losses. The assembled segments structure causes non-ideal mechanical air gap condition inevitably, and it brings significant effects on electromagnetic performance. Hence, this paper investigates electromagnetic force characteristics in long-stator PM linear motor with non-ideal mechanical air gap condition. First, the non-ideal mechanical air gap conditions are categorized, and then corresponding calculated models by finite element method are proposed. The influence of non-ideal air gap conditions on electromagnetic thrust, detent force and normal force characteristics are analyzed respectively. These studies can provide references to operational analysis and assembly process of electromagnetic launcher based on long-stator PM linear motor.

Design, simulation and testing of multi-segmented plate permanent magnet linear launcher

This paper presents a detailed description of downsized multi-segmented plate permanent magnet linear launcher, which puts emphasis on modular stator structure. For multi-segmented stator launcher with concentrated winding, specific topology and slot/pole number combinations are discussed. Considering different end boundary, back electromotive force (EMF) and inductance parameter of the starting and middle segments are investigated by finite element method (FEM), and then the accuracy of numerical solutions are verified by experimental results. Based on parameters characteristics analysis at transition, dynamic electromagnetic thrust is evaluated by energy method. Finally the combined simulated model with currents tracking scheme is built for multi-segmented system.

Thrust analysis and optimization for the segmented armature type permanent magnet linear synchronous motor

Recently double-side long primary type linear launcher has attracted more and more attentions for the electromagnetic launch system (EMLS). This paper analyzes the influence of segmented armature and presents a segmented double-side plate permanent magnet linear synchronous motor (PMLSM) in which the new ring windings are engaged. The calculation is described using analytical and two-dimensional finite-element methods. For the segmented motor with double-layer windings, single-phase inductance shows regular variation but three-phase inductances appear unbalanced; the thrust exhibits modification in expression because magnetic coupling occurs between d-axis and q-axis. Then the comparative analysis on thrust harmonics and the parameter optimization of the motor with ring windings are carried out. The main advantage of this system is to section the primary armature conveniently, and in the meantime the results show that the stable thrust can be achieved well by double-side multiple stage PMLSM.