Linear Flux-switching Permanent Magnet Motor Research Articles

Interior Profile Accuracy Assessment Method of Deep-Hole Parts Based on Servo Drive System.

Dimensional and profile measurements of deep-hole parts are key processes both in manufacturing and product lifecycle management. Due to the particularity of the space conditions of deep-hole parts, the existing measurement instruments and methods exhibit some limitations. Based on the multi-axis, highly precise servo drive system, a novel measuring device is developed. The laser displacement sensors are fed by the flux-switching permanent magnet linear motor, and the part is rotated by the servo motor. On this basis, the assessment methods of roundness, straightness, and cylindricity are proposed by employing the least square method (LSM). Additionally, considering the axial center deviation between the sensors and the part, the rotating center coordinate is optimized by the gradient descent algorithm (GDM). Then, the measurement system is constructed and the experiment study is conducted. The results indicate favorable evaluation error of the LSM fitting and GDM iteration. Compared with the coordinate measuring machine (CMM), the measured results show good consistency. In the error analysis, the angle positioning error of measured point is less than 0.01°, and the axial positioning error is less than 0.05 mm. The proposed system and assessment method are regarded as a feasible and promising solution for deep-hole part measurements.

Comparative Analysis of Normal Force Characteristics and Dynamic Influence of Linear Flux-Switching Permanent Magnet Motor for Rail Transit

Comparative Analysis of Normal Force Characteristics and Dynamic Influence of Linear Flux-Switching Permanent Magnet Motor for Rail Transit

Investigation On High Temperature Superconducting Linear Flux-Switching Motors With Different Mover and Stator Pole Pitch Ratios For Urban Railway Transit System

Linear Induction Motors (LIMs) are popular as driving motors in urban railway transit systems due to their simple and robust stator structures. However, the efficiency and power factor of LIM are lowered because of its eddy effect. As a promising alternative, Linear Flux Switching Permanent Magnet (LFSPM) motor offers high electromagnetic performance while keeping its stator simple. Despite these merits, the adoption of Permanent Magnets (PMs) of LFSPM motors influences their flux-weakening ability, thus leading to narrow speed range. To solve this problem, it is feasible to use High Temperature Superconducting (HTS) coils to replace PMs, forming HTS Linear Flix Switching Motor (HTS-LFSM). Among various parameters that influence the performance of HTS-LFSM, ratio of primary and secondary pole pitches is a leading parameter. Aim at investigating the relationship between pole pitch ratios and electromagnetic performance, different typical pole pitch ratios are compared against each other based on several common principles. The merits and drawbacks are analyzed with the help of Finite Element Method (FEM), and some conclusions are drawn.

Reduction of Thrust Force Ripple of High Temperature Superconducting Linear Flux-Switching Motors using Asymmetry Mover Structure

Compared with traditional linear motors, such as Linear Permanent Magnet Motors (LPMs) and Linear Induction Motors (LIMs), Linear Flux-Switching Permanent Magnet (LFSPM) motors have the merits of high efficiency, power density, with simple and robotic secondary structure. Despite these advantages, the flux-weakening ability of LFSPM motor is limited and thus the speed range of it is not ideal. As a promising choice, it is feasible to replace the PMs of LFSPM motors with coils made with High Temperature Superconducting (HTS) tapes. By using HTS material, High Temperature Superconducting Linear Flux-Switching Motors (HTS-LFSMs) have good flux-weakening ability while inheriting the edges of LFSM motors. Since the existence of HTS coils, the cooling system has a minimum size and has to take up certain room of the motor. When it comes to applications where the volume of motor is strictly restrained, there may not be enough room for a basic pattern of typical pole pitch combinations for HTS-LFSM, such as 12-7 or 12-9, leading to large thrust ripple. To solve this problem, a method of reducing thrust force using asymmetry mover structure is proposed based on a 9-5 pole pitch ratio. The mechanism and working principle are analyzed and the validation is verified with the help of Finite Element Method (FEM).

Analysis of a New Flux Switching Permanent Magnet Linear Motor

A novel flux switching permanent magnet linear motor (FSPMLM), which has the advantages of high thrust density [the ratio of average thrust to permanent magnet (PM) volume] and low cost for long-stroke application, is proposed and investigated in this article. The topology of the novel FSPMLM with 12 slots is introduced and the basic operating principle is analyzed first. The optimal geometric parameters are selected by using the layered orthogonal optimization method. Then the electromagnetic performance of the motor is investigated by the analytical method based on the equivalent magnetic network model (MNM). Finally, a scheme of setting auxiliary teeth in the primary component is adopted to suppress the unbalance of the three phase flux linkages.

Investigation of High Temperature Superconducting Linear Flux-Switching Motors With Different Secondary Structures

Compared with Linear Induction Motor (LIM), which is widely adopted for urban railway transit system, Linear Flux-Switching Permanent Magnet (LFSPM) motor has the merits of high efficiency, power factor and simple secondary structure. Therefore, LFSPM motor is claimed to be promising for urban railway transit system. However, research shows that speed range of LFSPM motor is limited due to Permanent Magnets (PMs). But for Linear Wound Field Flux-Switching (LWFFS) motor, electromagnetic performance is influenced by the large airgap. To incorporate the merits of LWFFS motor and LFSPM motor, High Temperature Superconducting Linear Flux-Switching Motor (HTS-LFSM) is proposed. However, it remains unknown which secondary structure of HTS-LFSM is suitable for urban railway transit. Hence, two HTS-LFSMs of slotted and segmented secondaries are designed, optimized, compared and analyzed in this paper. Finite Element Method (FEM) is adopted to calculate their performance.

Comparative Study of Permanent Magnet Assisted Linear Switched Reluctance Motor and Linear Flux Switching Permanent Magnet Motor for Railway Transportation

Linear switched reluctance motor (LSRM) has been investigated and supposed as a good candidate in railway system. Recently, permanent magnet assisted switched reluctance motor (PMA-SRM) has attracted extensive attention because of the high torque, robust structure and low cost. However, all these researches focus on the application of small air gaps. How does PMA-SRM perform in large air gap? No research has been conducted until now. As we know, there are many similarities between linear flux switching permanent magnet (LFSPM) motor and permanent magnet assisted linear switched reluctance motor (PMA-LSRM) such as similar primary iron, winding structure, robust secondary and a small amount of permanent magnets. In this case, what are the similarities and differences between these two kinds of motors in terms of electromagnetic characteristics? This paper will compare these two kinds of motors based on the volume of rail transit from the following aspects: thrust force, thrust ripple, efficiency. First, the topology, operation principle of the two LSRMs are introduced and designed. Then, the electromagnetic performance of LSRM is optimized through two dimensional finite element analysis (FEA) based on ANSYS software. The optimization objectives of PMA-LSRM are to maximize the thrust and to minimize the ripple at the given dimensions and the rated condition. The comparison of electromagnetic characteristics between LFSPM motor and PMA-LSRM is completed. Finally, it is concluded that the permanent magnets are not conducive to improving the power of LSRM. And the PMA-LSRM is not outstanding compared with LFSPM motor under the condition of large air gap for rail transit.

Comparison Between Linear Induction Motor and Linear Flux-Switching Permanent-Magnet Motor for Railway Transportation

Linear induction motors (LIMs) have been extensively adopted in urban railway transportation given their nonadhesion thrust and simple stator structure. However, these LIMs undergo unfavorable power factor and efficiency considering their copper and eddy losses. Recently, linear flux-switching permanent-magnet motors (LFSPMs) have attracted the attention of researchers due to their high power density, simple structure, easy heat dissipation, high efficiency, and high power factor. However, so far, no quantitative comparison exists between LFSPMs and LIMs of the size 1:1 to prove the feasibility of LFSPMs to be used in railway transit systems. Therefore, a comparative analysis between the two motors is conducted in this paper. First, this paper investigates the LIMs for railway transit using the finite element method (FEM). Second, the LFSPMs for railway transit is designed and optimized. Third, the electromagnetic performance of the two motors is compared and analyzed through the FEM. Finally, a small-sized prototype of the LFSPMs is constructed to validate the FEM results. It is concluded that LFSPMs offer a favorable thrust force, have high efficiency, and high power factor but have large normal force and force ripple. Therefore, applying LFSPM requires a reliable supporting device and a shock absorber.

Sensorless Control of Linear Flux-Switching Permanent Magnet Motor Based on Extended Kalman Filter

Linear flux-switching permanent magnet (LFSPM) motors have drawn extensive concern for rail transit drive systems because permanent magnets and armature windings are all located on the short primary, whereas the long secondary is made up of iron only. Thus, the LFSPM motor with low cost and high efficiency is an excellent choice for urban rail transportation system. However, the installation of linear encoders that are expensive and unreliable along with the long stator will bring about increased costs and reduced reliability. To overcome the shortcomings and fully exert the advantages of LFSPM motors, extended Kalman filter (EKF) is adopted to achieve sensorless control of LFSPMs for its better stability, robustness, and low requirements for working environment in this article. An improving tracking performance can be obtained using EKF considering the end effects of LFSPMs and the presence of noise. Both simulation and experimental results indicate that the motor can run reliably from standstill without position sensors, which is advantageous compared with other sensorless control methods based on electromotive force.

Comparative Study on Modular Longitudinal and Transverse Flux-Switching Permanent Magnet Linear Motor

Based on similar single-phase flux-switching permanent magnet linear motor (FSPMLM), a comparable modular longitudinal FSPMLM (LFSPMLM) and transverse FSPMLM (TFSPMLM) are presented and investigated in this article. The modular LFSPMLM and TFSPMLM have no magnetic coupling among modules. Single-phase piecewise-linear inductance models of LFSPMLM and TFSPMLM are proposed, and corresponding comparative studies are conducted. Comparative calculation results show that an optimized design scheme is established, and a set of structural parameter is proposed. The results of finite element analysis (FEA) show that the LFSPMLM has higher efficiency than TFSPMLM. However, the TFSPMLM has a small detent force, and controlling its thrust force performance is feasible. Prototype experiments of no-load detent force and average thrust force are performed, and the experimental results agree with the FEA results. This finding further verifies the conclusions of comparative investigation on characteristics between the proposed LFSPMLM and TFSPMLM.

Reduction of the Detent Force in a Flux-Switching Permanent Magnet Linear Motor

In this paper, the detent force caused by the end effect in a flux-switching permanent magnet linear motor (FSPMLM) with six slots and five poles is investigated and reduced by two different methods. First, the detent force is diminished by adjusting the position of end teeth of primary side and injecting compensation current into compensation windings wound around the end teeth. Based on the linear relationship between compensation current and compensation force, the proper compensation current is derived and analyzed. Then, to avoid the magnetic coupling between compensation windings and phase windings, a novel compensation module with independent magnet circuit is presented and attached to the primary side of FSPMLM. Third, the two detent force reduction methods are compared with each other, and the compensation module is proved to be more effective. Finally, a prototype of FSPMLM with compensation modules is manufactured and tested to validate the proposed compensation method.

Servo X-Y biaxial feed system of flux switching permanent magnet linear motor.

As both magnets and coils are arranged in the motor primary, a short primary long secondary flux switching permanent magnet linear motor (FSPMLM) is favorable to construct a feed system, especially for long distance, multi-axis applications. A novel FSPMLM with a complementary primary module and end-PM topology is proposed to directly drive a biaxial feed system, and the whole structure is presented. To consider the influence of temperature raise on motor performance, magnetic-thermal coupling finite element analysis is employed, and then, the motor dimensions are optimized by the response surface method. With the same 500 N rated force and 1.5 m/s rated speed of the two FSPMLMs, the biaxial prototype is fabricated. Considering the two-axis synchronization, the control system is constructed by using a commercial motion controller and servo drivers. Monoaxial and biaxial feeding experiments are carried out simultaneously. Both X and Y axes exhibit sufficient force capability for well dynamic response, and the positioning error is less than 0.14 mm. Biaxial diamond and circular trajectories are conducted, and the contour errors are less than 0.88 mm. It can be seen that the proposed FSPMLM feed system is featured with favorable performance and competitiveness for applying in various industrial applications.

Feeding Apparatus Directly Driven by Optimal Topology Flux Switching Permanent Magnet Linear Motor

For both magnets and coils are arranged in motor primary, short primary, and long secondary flux switching permanent magnet linear motor (FSPMLM) is extremely appropriate to long distance applications. A novel FSPMLM is developed to construct a feeding apparatus in this article. The magnetic field is analyzed by equivalent magnetic circuit (EMC), which indicates that the longitudinal end effect can be weakened by adjusting the width of the end-PMs. Then finite element analysis (FEA) and response surface methodology (RSM) are applied to optimize the force performance. The whole construction of the proposed FSPMLM feeding apparatus is designed and the prototype is manufactured. A commercial servo amplifier is used to control the prototype and the experiment setup is built to demonstrate the prototype performance. 500 mm feeding distance is conducted with the rated speed 1.5 m/s and the acceleration 10.0 m/s2, which indicates the high speed and high acceleration capacity. Then 10 kg and 20 kg weights are loaded on the prototype with the speed 200 mm/s and 100 mm/s, respectively. Well force response performance is exhibited, and the position error is sufficient low. It can be seen that the proposed FSPMLM feeding apparatus can be employed competitively in various machine tools.

A Novel Method to Reduce of Cogging Force in a Linear Flux-Switching Permanent Magnet Brushless AC Machine

The primary linear flux-switching permanent magnet (LFSPM) motor has the merits of high speed, high response, and direct drive. However, the presence of the cogging force in LFSPM motors compromises position and speed control accuracy, which can be particularly troublesome at low speeds. A novel approach of suppressing the slot effect cogging force for LFSPM is proposed according to repetitive control of time-varying periodic signals. The time-varying periodic thrust disturbance in t-domain is transformed to the signals defined in the x-domain, and a repetitive controller is designed. Furthermore, a series of specific harmonic currents are added into q-axis reference current, resulting in additional force components to counteract the end effect cogging force. Finally, experimental evaluations of the control strategy are performed on an AD5435-controlled LFSPM drive platform. The simulations and experiments verify that the proposed method can suppress the thrust ripple effectively.

Sliding‐mode observer based sensorless vector control of LFSPM motor for long‐distance drive system

A new series of linear flux-switching permanent magnet (LFSPM) motors has elicited considerable attention. This series incorporates the merits of the high efficiency of permanent magnet linear motors and the low cost of linear switched reluctance motors for a long-distance drive system. However, the vector control of the LFSPM motor requires an expensive and unreliable linear encoder, which must be as long as the entire railway (or at least the whole linear motor). Such a large encoder will lead to extra costs and will even weaken the benefit of the motor performance. Thus, developing its sensorless control for engineering applications is necessary. Sliding-mode sensorless control has the advantage of strong robustness to parameter variations and external disturbances, as well as high dynamic performance, which is important for long-distance drive systems. The proposed algorithms can extend the minimum operating speed, thereby enabling the motor to work at a lower speed. Both simulation and experimental results are provided for verification.

Design Optimization and Performance Comparison of Two Linear Motor Topologies With PM-Less Tracks

Linear Permanent Magnet Synchronous Motor (LPMSM) topology is the preferable choice for a linear motor in terms of high force density and good overall performance. However, its main drawback is the relatively high price caused by the extensive usage of rare-earth materials in the track. This factor is critically important, especially when this type of motor has to be used in a long-stroke application, such as storage or airport transportation lines where the main prerequisite is a low-cost, passive and robust track. Therefore, Linear Induction Motor (LIM) and Linear FluxSwitching Permanent Magnet Motor (LFSPMM) are two possible alternatives suitable for long-stroke applications. Considering only the price of the track, LIM topology, with its flat aluminum secondary is most attractive. Nevertheless, the absence of rare-earth materials limits the propulsion force generated by the LIM. Another attractive alternative is the LFSPMM topology, which also has a passive secondary, but it incorporates a limited amount of rare-earth materials in its mover, improving its force generation capabilities. As a relatively new topology, the research on LFSPMM is still limited [1], [2]. The existing design solutions for LIM having relatively small volume, have lower force density [3], compared to the designs having much larger overall dimensions [4]. Therefore, a direct comparison between LIM and LFSPMM is very difficult. Based on the volume of a benchmark LPMSM topology, in this paper, a comparison between LIM and LFSPMM is performed. To obtain optimal designs within this volume, a fast converging, semi-analytical methods are used for modelling both topologies and the results are used to compare LIM and LFSPMM topologies.

A novel double-sided flux-switching permanent magnet linear motor

This paper proposes a novel double-sided flux-switching permanent magnet (PM) linear (DS-FSPML) motor which is suitable for low speed and high thrust force applications. In order to balance the normal force, the motor adopts double-sided arrangement in which the mover is sandwiched between two stators. The mover teeth alternately located on both sides of the mover are composed of laminated iron core segments between which the axially magnetized PMs of alternate polarity are inserted. Similar to conventional flux-switching PM (FSPM) motor, the 3-phase concentrated windings are employed. And the stator is designed as a double-sided simple iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed motor are analyzed and compared with the conventional single-sided FSPM linear motor.

Analysis of Linear Flux-Switching Permanent Magnet Motor Using Response Surface Methodology

This paper focuses on the performance analysis of linear flux-switching permanent magnet (LFSPM) motor. The analysis of electrical machines is mostly done by finite element method (FEM) and analytical method. However, it is time-consuming to determine the effects of the design parameters on the motor performance with FEM. It is also difficult to utilize the analytical technique for the intricate structure of LFSPM motor. In this paper, the response surface methodology in conjunction with FEM is proposed to analyze the LFSPM motor efficiently. As a demonstration, the influence of design parameters on the motor net thrust force is analyzed with the proposed method. Analysis of variance and comparison between the fitted response and results obtained from FEM all confirm the validity of the proposed method.

Optimization of the Thrust Ripple of a Tubular Flux-Switching Permanent Magnet Linear Motor

The effective optimization methods are needed to reduce the thrust ripple for the tubular flux-switching permanent magnet linear motor (TFSPMLM), which is significant for reducing the vibration, and improving the reliability. The auxiliary teeth and core bridge are set and analyzed for the bipolar and single-polar winding structures. On this basis, this paper focused on a new method of the secondary pole pitch fine-tuning which can overcomes the disadvantages of increasing the volume, decreasing the average thrust, adding the cost, and so on. The influences of tuning the secondary pole pitch on the average thrust and the thrust ripple for the different winding structure motors are calculated and analyzed. The conclusion can provide reference for the application of the method of tuning secondary pole pitch to the TFSPMLM for different background demands.

Influence of Leading Design Parameters on the Force Performance of a Complementary and Modular Linear Flux-Switching Permanent-Magnet Motor

This paper investigates the influence of some leading design parameters on the force performance of a new complementary and modular linear flux-switching permanent-magnet (LFSPM) motor. The originality of the proposed structure is that each phase consists of two “E”-shaped modules, whose positions are mutually 180 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> electrical degrees apart. Also, there is a flux barrier between the two modules. First, the structure and influence of some leading design parameters on the force performance of the complementary and modular LFSPM motor are analyzed. Then, a conventional LFSPM motor obtained directly from a rotary FSPM motor is optimized and compared with the complementary and modular LFSPM motor based on finite-element method. The results reveal that the proposed motor has sinusoidal and symmetrical three-phase back electromotive force waveforms and smaller cogging force and force ripple than the existing motors. Moreover, a prototype of the proposed motor is built to validate the study.