Tubular Permanent Magnet Linear Motor Research Articles

An analytical model for a coaxial electromagnetic recuperator considering end effect

A coaxial electromagnetic recuperator (CER), leveraging the principle of tubular permanent magnet linear synchronous motor, has been introduced to mitigate the shortcomings of the traditional recuperator, including low reliability and uncontrollable counter-recoil motion. Firstly, the layout and structural scheme of the CER are presented, with the maximum recuperator force determined through a force analysis of the recoil process. Subsequently, by incorporating a virtual permanent magnet area at both ends of the permanent magnet array, a precise CER analysis model is developed. This model adeptly accounts for the end effect due to magnet length limitations and formulates expressions for air gap flux density, back electromotive force, and electromagnetic thrust. The analytical model’s accuracy is then validated against a finite element model. Finally, the key parameters influencing CER performance were improved, and the overall structure of the CER was refined, significantly enhancing its thrust capabilities.

Improved Adaptive Terminal Sliding-Mode Reaching Law for Speed Control of TPMLSM With Disturbance Observer

This paper investigates the speed regulation issue of the tubular permanent magnet linear synchronous motor (TPMLSM) control system based on sliding-mode control (SMC) and disturbance compensation technology. By introducing the terminal attractor on the basis of exponential reaching law, an improved adaptive terminal sliding-mode reaching law (IATSMRL) is proposed to ensure the state variables of the control system to reach their equilibrium points quickly and suppress the chattering effectively. Based on the IATSMRL, the sliding-mode speed controller is designed to improve the dynamic performance of the TPMLSM control system. To further compensate the lumped disturbance in the TPMLSM control system, the paper utilizes an extended sliding-mode disturbance observer (ESMDO) to obtain the estimated lumped disturbance. Then an anti-disturbance sliding-mode speed controller is designed to strengthen the disturbance rejection capability of the TPMLSM control system and further improve the dynamic performance. The stability of the controller is proved by the Lyapunov stability theory. Comprehensive simulation and experimental results have been carried out to demonstrate the superiority of the proposed method.

Multi-Objective Optimization of Tubular Permanent Magnet Linear Motor Based on Improved NSGA-II

Multi-Objective Optimization of Tubular Permanent Magnet Linear Motor Based on Improved NSGA-II

Structural design and performance prediction of novel modular tubular permanent magnet linear synchronous motor

The limitation of the primary core length of the tubular permanent magnet synchronous linear motor (TPMSLM) causes large thrust ripples during operation. To end this, a modular TPMSLM with two units is proposed. The principle of its suppression of end effects is derived, and utilization of the three-phase winding is improved using the star vectograms of the back electromotive force (EMF). Afterward, an equivalent subdomain method is adopted to analyze the above structure. This method combines the subdomain and the equivalent magnetic circuit (EMC) model, and the comparison with nonlinear FEM verifies its effectiveness. Using this integrated approach, reasonable structure parameters are selected. Finally, the experimental platform of the two-unit modular TPMSLM prototype is built with the selected structural parameters. Good agreement between the simulation and the experiment on the back EMF, detent force, and the prototype's static thrust verifies the new structure's feasibility.

Study on dynamic characteristic and forging capacity of the direct drive press with symmetrical toggle booster mechanism driven by TPMLM

Compared with the conventional servo press, the direct drive press even has no transmission mechanism, so it has advantages in controllability, precision and energy management. But, the forging capacity of the direct drive press is limited by the power of the linear motor. In this paper, a novel press driven by a tubular permanent magnet linear motor (TPMLM) is presented, and a symmetrical toggle booster mechanism is specially proposed to enhance the forging capacity. The mathematical model of the toggle booster mechanism is established, The TPMLM is designed, and the experimental prototype of the novel press is manufactured. The forging capacity and dynamic characteristics of the press are studied theoretically and experimentally. The results show that the introduction of the symmetrical toggle booster mechanism enriches the dynamic characteristic curve of the press and enhances the forging capacity. Therefore, the structural parameters of the toggle mechanism and the working position of the slider can be adjusted to meet different technological requirements. In addition, based on the research work, three directions are proposed to improve the forging capacity of the novel press. The research contributes to the performance optimization and development of direct drive press.

Improvement of the slotless tubular permanent magnet linear motor with lighter mover mass for punching applications

The slotless tubular permanent magnet linear motor (STPMLM) offers obvious advantages when it is applied to the punching system, such as space saving and controllable impact strength. Herein, the mechanical and electromagnetic coupled differential equations were established to present a comprehensive analysis of the relationship between mover mass and motor performance in the punching system. The travel time of the punching movement was expressed analytically under the condition of the mover obtaining the same impact kinetic energy, and the relationship between the mover mass and the resistive energy consumption in one punching process was also deduced under the same condition. Then the analytical results were validated by a numerical model. The studies show that a lighter mover mass can contribute to less resistive energy consumption and faster dynamic response in the punching applications. Based on that, a STPMLM with special-shaped yoke was designed for lighter mover mass. Moreover, prototype experiments including static thrust characteristic and dynamic performance were conducted. The experimental results proved that the proposed permanent magnet linear motor with special-shaped yoke can improve the dynamic performance and reduce resistive energy consumption while ensuring that the electromagnetic performance is not affected.

Analysis and Research on the Comprehensive Performance of Vehicle Magnetorheological Regenerative Suspension

Magnetorheological (MR) regenerative suspension system can not only achieve excellent comprehensive suspension performance but also effectively recover and utilize vibration potential energy, which has been a research hotspot in the field of vehicle engineering. In this paper, for the 1/4 vehicle’s MR regenerative suspension system parallel with a tubular permanent magnet linear motor (TPMLM), the dynamic model of the MR semi-active suspension system and the TPMLM finite element model are established separately to form a joint simulation platform. The simulation analysis of the comprehensive suspension performance and regeneration performance under different road excitations is performed. The results show that installing TPMLM does not change the natural resonance frequency of the suspension system, which ensures good driving comfort and handling stability. At the same time, it has considerable regeneration power. This research can provide a reference for the stability analysis and popularization of the vehicle’s MR regenerative suspension system.

Design Optimization of Improved Halbach Tubular Permanent Magnet Linear Synchronous Motor with Less Permanent Magnet

To reduce the permanent magnet (PM) usage and cost, the improved Halbach tubular permanent magnet linear synchronous motor (IH-TPMLSM), which has unequal thickness of the radial and axial magnetized PMs located in the mover, is developed in this paper. Taking the maximum average thrust as the optimization objective, the single-step optimization method based on sensitivity analysis is used to optimize motor under the same current density by finite element (FE) analysis. The influence of the pole-pitch τ on the detent force is analyzed. According to the comparison of optimized TPMLSMs, the results show that when pole-pitch τ = 30.5mm and the full-pitched winding disposition τs = 31.5mm, the detent force is reduced by 55.87%. Finally, the open-circuit back EMF, air gap flux density, the thrust of the IH-TPMLSM and the quasi Halbach TPMLSM (QH-TPMLSM) are compared. The quantity of PMs of the IH-TPMLSM is 15.27% lower and the average thrust is 4.01% higher than that of QH-TPMLSM. Meanwhile the thrust ripple is reduced by 36.12%.

Design and Experimental Verification of a High Force Density Tubular Permanent Magnet Linear Motor for Aerospace Application

<div class="section abstract"><div class="htmlview paragraph">This paper presents the design and construction of a high force density tubular permanent-magnet (PM) linear motor. A strut structure of a tubular PM linear motor developed to improve resistance to impurities and structural rigidity is described.</div><div class="htmlview paragraph">In the design, computationally efficient two-dimensional finite-element analysis is used to estimate the motor force density. The motor’s design is optimized for the major pole number/slot number combinations of 8/24, 16/24, 20/24, 28/24, 32/24, and 40/24. The optimized motor design of a three-phase 16/24 combination with one-layer winding achieved the highest force-to-mass density. The force-to-mass density of the designed motor is higher than that of the first prototype motor by a factor of 5. The validity of the proposed design method and the expected drive characteristics are experimentally verified using the prototype.</div></div>

Flux Characteristics Analysis of a Single-Phase Tubular Permanent Magnet Linear Motor Based on 3-D Magnetic Equivalent Circuit

This paper gives a way to analyze the flux characteristic of a single-phase tubular permanent magnet linear motor (TPMLM) based on the 3-D magnetic equivalent circuit (MEC) method. By studying the flux tubes of this single-phase TPMLM with the finite-element analysis software—FLUX, a 3-D MEC model of this motor can be constructed, and the flux linkage of the single-phase TPMLM can also be calculated. The static and dynamic performances of the single-phase TPMLM calculated with the 3-D MEC model are compared with the 3-D finite-element model and experimental results, which verify the correctness of the proposed 3-D MEC model.

Modeling and Optimization of a Tubular Permanent Magnet Linear Motor Using Transverse-Flux Flux-Reversal Topology

In this paper, a novel tubular transverse-flux flux-reversal linear motor for long stroke applications is proposed. The proposed motor not only has the low-cost advantage of the existing flux-reversal permanent magnet (PM) linear motor (PMLM) by combining both PMs and armature winding in short primary, but also address the problem of complicated structure in conventional tubular PMLM by using the manufacturing process of the rotary motor. First, in order to reduce circumferential magnetic flux leakage and improve the utilization ratio of PM, the motor structure with the alternating distribution of double N poles and double S poles in the circumferential direction is designed, and the operating principle of the motor is presented. Then, the equivalent magnetic circuit model of the unit motor is established to derive the expressions of the back electromotive force (EMF) and the electromagnetic thrust. Third, the equivalent two-dimensional (2-D) finite-element method (FEM) is used to optimize the structural dimensions and analyze the static characteristics including the back EMF, the detent force, and the thrust. Meanwhile, the three-dimensional FEM verify the validity of the equivalent 2-D FEM. Finally, the experimental results verify the validity and the correctness of the topology structure and the design method of the motor.

Research on the Thrust Characteristics and Temperature Rise of Slot-less Tubular Linear Motor for Active Vehicle Suspension

This paper presents a Slot-less Tubular Permanent Magnet Linear Motor (ST-PMLM), which does not have the cogging structure in the stator. Meanwhile, its lateral stator core doesn’t split, so the motor only has longitudinal edge effect. Since the ST-PMLM is supposed to be used as the active damper for vehicle suspension system, this paper focus on two aspects: increasing the output thrust and restraining the thrust fluctuation of the motor. Firstly, the equivalent magnetic circuit model of the ST-PMLM is established. The influences of structural parameters, including the thickness of the magnetic pole, the length of the air gap, the thickness of primary iron core and the thickness of primary winding, on the air gap flux density and the output thrust are analyzed. Then, the distribution of the magnetic field at the end of the primary iron core is observed. Length compensation in the end of primary iron core is adopted in order to reduce the thrust fluctuation. Finally, the prototype of ST-PMLM is developed and the experiment test bench is built. Based on the no-load test of the prototype, the effectiveness of the primary core length compensation in suppressing end effects and inhibiting fluctuations are verified.

Structural Parameter Optimization of a Tubular Permanent‐Magnet Linear Machine for Regenerative Suspension

The regenerative suspension can effectively recover the vibration potential energy of the vehicle suspension, thus has broad prospects in application. In this paper, a tubular permanent‐magnet linear motor (TPMLM) with the Halbach array magnetic pole is analyzed. The magnetic field analysis method of the excitation source separation is proposed, and then, the transient analytical model of output electromagnetic force and the external circuit characteristic under displacement excitation is established. A modified particle swarm optimization algorithm is further adopted to optimize the structural parameters of TPMLM. By comparing with the finite element analysis, the correctness of the proposed analytical model and the optimization are verified. This work lays the theoretical foundation for extensive application of the regenerative suspension.

Design Principles of a Phase-Shift Modular Slotless Tubular Permanent Magnet Linear Synchronous Motor With Three Sectional Primaries and Analysis of Its Detent Force

This paper investigates a modular slotless tubular permanent magnet linear synchronous motor, which includes several sectional motors by setting flux barriers and rearranging windings. It focuses on the design method of the different combinations with small detent force. The detent force models of the sectional and whole modular motor are established analytically in terms of a Fourier expansion and verified by a prototype. Then the design principles of the sectional motors are analyzed. On the basis of the models, the schemes whose flux barriers’ widths equal to one-third of the pole pitch are selected, followed by the comparison of two kinds of different sectional combinations. Their detent-force characteristics are then described in detail. The conclusions about the different combinations are drawn.

Sectional Combinations of the Modular Tubular Permanent Magnet Linear Motor and the Optimization Design

To overcome the disadvantage that the detent force of the permanent magnet linear synchronous motor (PMLSM) with short primary is large, a scheme of the modular PMLSM with flux barriers is proposed in this paper. First, the detent force model is established and verified. The phase-angle characteristics of the harmonics in the detent force waveforms are analyzed. Then, the design principles of the scheme with different sectional combinations are analyzed, and two series of the combinations are demonstrated. The detent force and thrust characteristics of these combinations are subsequently compared. In addition, to improve the thrust density, the auxiliary teeth set at the ends of the sectional primary cores are proposed. Finally, the corresponding conclusions obtained by comparing the modular motors with the traditional motor are presented.

Erratum: Cogging force reduction for tubular permanent magnet linear motor by slots with different sizes

Erratum: Cogging force reduction for tubular permanent magnet linear motor by slots with different sizes

Flux Characteristics Analysis of Single-Phase Tubular Permanent Magnet Linear Motor

The flux characteristics of a single-phase tubular permanent magnet linear motor (TPMLM) are analyzed with a magnetic equivalent circuit (MEC) method in this paper. First of all, the single-phase TPMLM is mainly divided into five parts, including stator sleeve, stator yoke, air gap, the permanent magnetic part of mover, and the ferromagnetic part of mover. In consideration of saturation, the flux linkage of the single-phase TPMLM at four special mover positions can be calculated with the help of the magnetic tube method and Gauss–Seidel iteration. The nonlinear relationship between flux linkage, mover position, and current can be mapped utilizing a high-order Fourier series with the flux linkage data obtained from the MEC method. It is consistent with a three-dimensional finite element method and experimental data. What is more, the simulated dynamic and static performance of the TPMLM are also consistent with experimental data, which verifies the effectiveness of the proposed MEC method.

Cogging force reduction for tubular permanent magnet linear motor by slots with different sizes

Reduction of cogging force is one of the main concerns of tubular permanent magnet linear motor (TPMLM). In this paper, an analytical calculation of air-gap magnetic density is derived. In addition, an analytical calculation of cogging force is deduced by the energy method. The impact of slots with different sizes on the Fourier coefficients of relative air-gap permanence function is demonstrated. When the nz/4p is the integer, it will produce the cogging force. Therefore, it is practical to reduce the cogging force by changing the Fourier coefficient smaller. The effectiveness of the theoretical analysis is validated by experimental results.

Analysis of Tubular Linear Motors for Different Shapes of Magnets

This paper presents the analysis of tubular linear motors for different shapes of magnets. The appropriate option for refrigeration applications is the single-phase tubular permanent magnet linear motor (TPMLM), which provides high efficiency, high thrust force, and low cogging force. Three design variants of TPMLMs with moving magnet and quasi-Halbach magnetization have been proposed, and their finite-element analysis (FEA) models have been established. Accordingly, analytical methods using Fourier series and Maxwell’s equations have been created for the three proposed designs, and the results have been compared. It is found that the results from the analytical method are in good agreement with the FEA results.

Minimization of Eddy-Current Loss in a Permanent-Magnet Tubular Linear Motor

This paper presents a minimization of eddy-current loss (ECL) in permanent-magnet (PM) of three tubular linear PM motors (TLPMMs). Three-dimensional Finite-Element Analysis has been used for the simulations. The ECL component is usually not taken into consideration in conventional PM motors. In present technologies, ECL is generated inside magnets of PM motors, due to both the high conductivity of the rare-earth magnets and the harmonics of the slot. This loss can increase the temperature inside the magnets and that may deteriorate their magnetic properties and potential risk of thermal demagnetization. Therefore, in the translator, segmented magnets has been used, because the cancelation of the ECL with this technique is possible as illustrated by the FEA results. Meanwhile, for the stator core of the three proposed motors, soft magnetic composite (SMC) material, Somaloy 700 has been used for its low cost and approximately zero ECL.