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Nowadays, linear induction motors (LIM) are most used in applications such as transportation, liquid metal pumping, material handling, etc. These applications require large forces and high constant speed under changes in load. The LIM suffers from change in speed as a result of the force loads applied to it instantaneously, which causes high ripple in the force response and not constant speed. This research proposes solutions to these problems by designing an intelligent controller to improve the response variable-speed with different forces. LIM was represented by d-q model using MATLAB/Simulink based-on equivalent circuit equations for LIM and study dynamic performance of this machine. The motor was operated at different speeds and loads; the speed change was observed when the load changed. a PI-controller was designed to control velocity of the machine and keeping its velocity constant at load changes. the values of gains (Kp,Ki) was taken manually by using Ziegler method and this requires a long time as tuning the gain values at every reference speed. An intelligent self-tuning fuzzy-PI controller was prepared to select best values of gains and compared with PI-controller. The simulation outcomes display that fuzzy-PI controller has improved speed and force moving performances machine than PI-controller since we obtained least ripple in the force response. The results obtained in the simulation are interesting, given that the Fuzzy-PI controller designed has nonlinear behavior that achieves wide range of speeds operation for the machine at variable forces compared with traditional PI-controller, and this gave clear improvement in the engine's performance. [ABSTRACT FROM AUTHOR]

In order to improve the performance of a Proportional-Integral-Derivative (PID) controller used in the control of Linear Induction Motor (LIM) V/f speed, this research presents a bio-inspired meta-heuristic soft computing approach. A PID controller specifically designed for the LIM system is described in detail, with a focus on how to optimize the controller using an evolutionary strategy that makes use of the Nutcracker Optimizer. Settling time, rise time, maximum overshoot, and ITAE (Integral-Time Absolute Error) are examples of transient response specifications that are achieved in MATLAB/Simulink by using a step input to the LIM and the optimal set of PID parameters chosen from the optimization. In order to determine the most effective technique for obtaining the optimum response in LIM, these outcomes are then contrasted with outcomes from other soft computing techniques.

In order to solve the problem of lacking velocity feedback information in the velocity closed-loop control system for linear induction motors (LIM) after cancelling the velocity sensor, a velocity observer based on the extended Kalman filtering algorithm has been implemented, considering the end edge effect of LIM. Firstly, based on the mathematical model of three-phase linear induction motor considering edge effect, an extended Kalman filter observer with appropriate gain and covariance update matrix is derived. Based on the vector control system of LIM, the speed parameters identified by the observer are fed back to the speed closed-loop system. Then, the vector control system model of linear induction motor with speed observer is built in Simulink, and the identification speed of observer is compared with the actual speed of motor. Finally, the results show that the closed-loop control using the identification speed can ensure the stable operation of the system. Under three kinds of loads, the error between the predicted speed and the actual speed of the observer is form 0.51% to 2.34%. The various dynamic performance of the system reveals that the LIM vector control system based on the extended Kalman filter observer increases prediction velocity error and decreases thrust error with increasing load. However, the magnetic flux amplitude error slightly increases. Therefore, considering the end-edge effect, the observer based on the extended Kalman filter can replace the velocity sensor to achieve three-phase LIM control under both unloaded and loaded conditions.

Ten years ago, the concept of the hyperloop vacuum train promised to revolutionize transportation by offering a fast, inexpensive, and eco-friendly alternative to traditional modes of travel. The key components of the hyperloop are a vacuum tube, magnetic levitation, and linear electric propulsion technology, which are envisaged to achieve surface velocities approaching the speed of sound. This paper presents the functionalities of an ideal hyperloop transportation system (HTS) with a low-cost track and lightweight hyperloop capsule. It is shown that this ideal system is indeed difficult to achieve in reality. Despite the potential benefits, hyperloop technology lacks experimental evidence at subsonic speeds to reach a higher level of technological readiness. Taking one step back, the hyperloop has lessons to learn from the maglev research and experiments in the 1970s. In fact, there are many unresolved challenges associated with maglev technologies, even at moderate speeds, that need to be recognized before reaching the whole way into the subsonic speed domain. This paper provides a status update after ten years of hyperloop research and development.

To realize the omni-directional steering function of urban micro electric vehicle and avoid the defects of traditional multi-degree-of-freedom (multi-DOF) drive, a multi-DOF spherical induction motor (SIM) as hub motor is presented, which is used to replace the conventional wheel and steering system to drive vehicles directly. SIM is mainly composed of three arc-shaped stators and one spherical rotor. And torque is directly output from the surface of the spherical rotor. The structure parameters of SIM are determined based on the design methodology of linear induction motor (LIM), and a finite element model (FEM) is established. Meanwhile, the field-oriented control (FOC) system of SIM is designed, and a multiple physics field co-simulation platform is constituted. By electromagnetic transient simulation and co-simulation, the effectiveness of structure parameters and FOC system are verified systematically. To realize the multi-dimension drive of SIM, the torque model is analyzed, and a multi-DOF drive control strategy is proposed, which is realized by mathematical modeling. The results indicate that SIM can achieve two rotational DOF drive without the angle limitation, and the control system has appropriate dynamic and tracking performances. The design scheme and control strategy proposed are reasonable. [ABSTRACT FROM AUTHOR]

Nowadays, with the growing population, demand for efficient public transportation systems has increased. Magnetic levitation (maglev) trains are one of the best choices for the future. There are three separate systems in a classical magnetic train to achieve desirable performance. Hence, several control systems and sensors are essential for train operation. Accordingly, the classical maglev trains include complex structures and they are so expensive. This paper presents the design, optimization, and control of a combined magnetic train structure with the integrated performance of suspension and guidance and a complementary propulsion system. These combined topologies provide a simple design, enure a more convenient movement, and reduce construction and operation costs. [ABSTRACT FROM AUTHOR]

Background and Objectives: Linear Induction Motors (LIMs) are favorite machines utilized in various industrial applications. But, due to the end effect phenomena, control of a LIM drive is more complicated than rotational machine drives. Therefore, selecting the proper control strategy for a LIM drive has been a significant challenge for the researchers. Methods: This paper concentrates on a new Model Predictive Control (MPC) of LIM drives which considers the end effect. Accordingly, the discrete-time model of the LIM with end effect is extracted, and the required flowchart used for the MPC of LIM drive has been presented in this paper. Results: To study the effectiveness of the suggested strategy, simulation results of a LIM drive with MPC are presented and compared to the traditional Indirect Field Oriented Control (IFOC) of LIM drive. Simulations have been carried out using Matlab. The end effect has been considered in the LIM model and control strategies. Conclusion: Simulation results validate that the suggested MPC of LIM drive yields excellent dynamic characteristics such as fast speed response with no overshoot. Moreover, in comparison to the traditional IFOC method, the suggested MPC strategy offers lower current ripple and lower electromagnetic force ripple, and therefore, it is suitable for industrial drive applications. [ABSTRACT FROM AUTHOR]

Background and Objectives: The principal aim of this paper is to show an independent vector control of two five-phase Linear Induction Motors (LIMs) that are supplied from a single VSI. Methods: The LIMs are running at the same speed but with different load conditions. This concept can be especially beneficial in long trains with distributed power. To achieve excellent control characteristics and to reduce the undesirable tension forces between the train mechanical couplers, Fuzzy Logic Controllers (FLCs) have been utilized.Results: As a result, the fault occurrence of the train control systems decreases, and the system reliability increases. The results prove the electrical independence in control of a five-phase two-LIM drive supplied with a single VSI. Furthermore, in the presence of the train mechanical couplers and connections, the application of FLC offers excellent control characteristics and reduces the undesirable tension forces. Furthermore, to obtain a more worthwhile validation of the theoretical results, an experimental set up has been constructed and results have also been presented.Conclusion: According to the results, the undesirable tension forces imposed on train couplers are reduced. Consequently, it leads to higher system efficiency, lower deterioration of the train couplers and connections, greater system reliability, and higher passenger safety and comfort.

This article proposes a new input–output feedback linearization control (FLC) technique of linear induction motors (LIMs), taking into consideration both the dynamic end-effects and the iron losses. Starting from a previously conceived dynamic model, including the dynamic end-effects and the iron losses, all the theoretical framework of the FLC has been developed. The proposed FLC improves a previous version of FLC in accounting also the iron losses, which in LIMs with fixed-secondary sheet play a pivotal role more than in rotating induction motors (RIMs). The proposed FLC has been experimentally tested on a suitably developed test setup, and experimental comparisons between the proposed FLC, the classic field-oriented control and a previously developed FLC, not accounting for the iron losses, have been shown in variable flux working conditions. [ABSTRACT FROM AUTHOR]

This article presents an efficient multi-objective optimization model for linear induction motors (LIMs) with a novel approximation and prediction strategy. The proposed method can realize the optimization design with speediness and accuracy, while reducing the calculation complexity of eddy current analysis. The sample data in this model are obtained by 3-D finite-element method (FEM) considering the skin effect and edge effect. Then, the Latin hypercube sampling (LHS) method is adopted to extract dimensional data including every structural parameter of the secondary. Based on these samples, a multiple analysis model is established using eXtreme Gradient Boosting (XGBoost) method. By employing this analysis model, several optimization structures are provided satisfying the limitation and rationality of designing structure and performance requirements. The precisions of the thrust force, vertical force, eddy current, and copper loss of optimal structures are validated by FEM. [ABSTRACT FROM AUTHOR]

This article investigates the influence of power converters and linear induction motor (LIM) without energy storage system on an axial-flux permanent magnet synchronous generator (PMSG) based on electromagnetic field characteristic analysis. First, the axial-flux PMSG and the LIM are introduced with characteristic analysis results, and their verification is addressed by a finite element method (FEM) and experiment. The axial-flux PMSG is double-side rotor type with slotless structure for cogging torque reduction, and rare-Earth permanent magnets are employed for high power density. On the other hand, since the LIM has an overhang structure in the secondary plate, the transverse edge effect is considered in the analysis to determine the overhang length of the secondary structure, and the optimized length is verified by the results of thrust force and equivalent circuit parameters. In this study, manufactured machines are connected with power converters, and relevant experiments are performed to measure the current according to various operating conditions of LIM as a load. By analyzing the power losses, the influence of the LIM operation on the axial-flux PMSG is discussed in this study. [ABSTRACT FROM AUTHOR]

Background and Objectives: The principal aim of this paper is to show an independent vector control of two five-phase Linear Induction Motors (LIMs) that are supplied from a single VSI. Methods: The LIMs are running at the same speed but with different load conditions. This concept can be especially beneficial in long trains with distributed power. To achieve excellent control characteristics and to reduce the undesirable tension forces between the train mechanical couplers, Fuzzy Logic Controllers (FLCs) have been utilized. Results: As a result, the fault occurrence of the train control systems decreases, and the system reliability increases. The results prove the electrical independence in control of a five-phase two-LIM drive supplied with a single VSI. Furthermore, in the presence of the train mechanical couplers and connections, the application of FLC offers excellent control characteristics and reduces the undesirable tension forces. Furthermore, to obtain a more worthwhile validation of the theoretical results, an experimental set up has been constructed and results have also been presented. Conclusion: According to the results, the undesirable tension forces imposed on train couplers are reduced. Consequently, it leads to higher system efficiency, lower deterioration of the train couplers and connections, greater system reliability, and higher passenger safety and comfort. [ABSTRACT FROM AUTHOR]

Background and Objectives: Despite superior privileges that multiphase motors offer in comparison with their three-phase counterparts, in the field of multiphase linear induction motors (LIMs) few studies have been reported until now. To combine the advantages of both multiphase motors and linear induction motors, this paper concentrates on multiphase LIM drives considering the end effects.Methods: The main contributions of this paper can be divided into two major categories. First, a comparative study has been conducted about the dynamic performance of Fuzzy Logic Controller (FLC) and Genetic-PI controller for a seven-phase LIM drive; and second, because of the superior performance of the FLC method revealed from the results, the harmonic pollution of the FLC based LIM drive has been studied in the case of supplying through a five-level Cascaded H-bridge (CHB) VSI and then compared with the traditional two-level VSI fed one.Results: The five-level CHB-VSI has utilized a multiband hysteresis modulation scheme and the two-level VSI has used the traditional three-level hysteresis modulation strategy. Note that for harmonic distortion assessment both harmonic and interharmonic components are considered in THD calculations.Conclusion: The results validate the effectiveness of the proposed FLC for seven-phase LIM drive supplied with five-level CHB-VSI and guarantee for perfect control characteristics, lower maximum starting current, and significant harmonic and interharmonic reduction.

This article presents the design and innovative test of a linear induction motor (LIM) to be used in the urban superconducting magnetic levitated vehicle named MagLev-Cobra. This levitation method, based on the flux pinning property of high-temperature superconductors in the proximity of rare-earth permanent magnets, has constraints related to the lifting forces. This issue is even more critical as there is no control of the levitation gap, which changes according to the load. The motor design is based on analytical equations and computational simulations by finite element methods. An innovative workbench for tests was developed to measure values of interest, such as end effects, forces, electrical currents, magnetic flux densities, and others. Numerical and experimental results support the desired performance of the proposed LIM. [ABSTRACT FROM AUTHOR]

In power electronics and power systems, the dual-phase-locked loop (DPLL) is a well-accepted approach to maintain zero steady-state errors when subjecting to a frequency ramp input. This distinctive characteristic of the DPLL may make it as a promising candidate for speed estimation in speed-sensorless drive systems. Considering this issue, a DPLL-based speed estimation scheme for linear induction motor speed-sensorless drive systems is presented in this article to achieve accurate speed estimation. The basics of the DPLL and the direct application of the DPLL scheme are provided. However, in practice, the direct application of the DPLL scheme may degrade the performance of the entire system, which includes the nonidealities in the secondary electromotive force (EMF) signals, such as harmonics and parameter variations. Accordingly, the prefilter and the amplitude normalization scheme are employed to mitigate the effect of nonidealities. Meanwhile, the small-signal model of the proposed DPLL scheme is presented, enabling the analysis of the dynamic performance and the comparison of the synchronous reference frame phase locked-loop scheme. In addition, a parameter tuning guideline of the proposed DPLL scheme is detailed by using the derived small signal model. The performance of the proposed DPLL scheme is investigated by experimental tests. [ABSTRACT FROM AUTHOR]

This article presents a new method for combined levitation and propulsion control in maglev/Hyperloop systems by selectively applying AC and DC modes of operation to a group of asymmetric double-sided linear induction motors (ADSLIMs). Although adjusting the AC current magnitude of lower and upper primary windings in ADSLIMs allows simultaneous control of thrust and lift forces, the limitation of this current balancing technique prohibits them from producing a high lift force while operating with low thrust force. To overcome this limitation and to simultaneously control the thrust and lift forces of the ADSLIMs with high efficiency under different operating conditions, a combination of AC and DC modes of operation is proposed. AC mode of operation consists of feeding different AC current amplitudes to the upper and lower ADSLIM primary windings to produce and control the required thrust and lift forces. The DC mode of operation consists of controlling one or several ADSLIMs to operate with DC excitation to realize the desired lift force at lower thrusts which otherwise cannot be achieved by operating in AC mode alone. The concept of the new combined control strategy is studied using two-dimensional finite element (FE) electromagnetic simulations and compared with an Inductrack permanent magnet (PM) based passive magnetic levitation system.

This is the second part of an article, divided into two parts, dealing with the definition of a space-vector dynamic model of the linear induction motor (LIM) taking into consideration both the dynamic end-effects and the iron losses as well as the offline identification of its parameters. This second part is devoted to the description of an identification technique that has been suitably developed for the estimation of the electrical parameters of the LIM dynamic model accounting for both the dynamic end-effects and iron losses. Such an identification technique is strictly related to the state formulation of the proposed model and exploits genetic algorithms for minimizing a suitable cost function based on the processing of both the primary current and speed estimation errors. The proposed parameters’ estimation technique has been validated experimentally on a suitably developed test set-up. It has been further validated by a finite element analysis model of the LIM. [ABSTRACT FROM AUTHOR]

This is the first part of the article, divided into two parts, dealing with the definition of a space-vector dynamic model of the linear induction motor (LIM) taking into consideration both the dynamic end-effects and the iron losses and its offline identification. This first part specifically treats the theoretical formulation of this model, which has been expressed in a state form, so to be, in perspective, suitably adopted for developing novel nonlinear control techniques, nonlinear observers as well as electrical losses minimization techniques. Besides the formulation of the dynamic model in space-vector state form, a steady-state analysis is proposed, highlighting the combined effects of the dynamic end-effects and the iron losses on the main electrical quantities of the LIM. [ABSTRACT FROM AUTHOR]

Due to the large air gap length, severe end effects, and the light load operating conditions during cruising, the efficiency of linear induction motors (LIMs) applied in urban transit, i.e., linear metro, is usually quite low. In order to overcome this drawback, this manuscript makes a comprehensive efficiency optimization to LIM efficiency from both motor design and control aspects. On the one hand, by analyzing the effects of different parameters on LIM performance, eight main parameters are selected as the optimization variables to achieve the optimal design of LIM through genetic algorithm (GA), so as to realize higher efficiency at rated operation point. On the other hand, considering the LIM still with low efficiency under light load, an optimal efficiency control (OEC) based on an integrated loss model, which contains both motor and inverter losses, is presented to promote the operating efficiency of LIM drive system in the whole operation area. Finally, the comprehensive efficiency optimization results are validated by related experiments on basis of one 3 kW prototype. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In order to fast calculate the thrust force and normal force of linear induction motor (LIM) for low-speed maglev train under overall conditions including traction and braking, this paper proposes an improved equivalent circuit (EC) method. Firstly, the improved equivalent circuit model is proposed based on the traditional one by adopting a precision correction factor, which can accurately consider the transverse edge effect of cap-shape secondary conducting sheet. Moreover, the permeability of back-iron and magnetic inductance are amended considering the saturation effect. The corresponding calculation procedure is given out. Then, the precise correction factor is investigated based on 2D finite element (FE) model. By comparison with the traditional Russell and Norsworthy correction factor (RNF), the precision correction factor is proved to be more suitable to LIM with wide-range slip frequency. Finally, the thrust force and normal force of LIM with different slip frequency are predicted under braking and traction conditions by improved EC method. The predicted results and the proposed method are validated by 3D FE method and experiment results. [ABSTRACT FROM AUTHOR]

Flux estimation is of great importance for high-performance linear induction motor (LIM) drives. However, due to the end effects of LIMs, range of variation in mutual inductance and secondary resistance is quite high with the change in operating condition, and the flux estimation suffers from these LIM parameter variations. To alleviate the influence of these parameter variations, this paper proposes a new flux estimation algorithm based on two improved extended state observers (ESOs) with expanded bandwidth for observing disturbances. One of them is especially designed to observe the ac disturbance at certain frequency. Taking advantage of the improved ESOs, the robustness of the flux observer to parameter deviations can be significantly strengthened, and the vector control strategy based on this new flux observer can achieve better dynamic performance. Finally, the effectiveness of the proposed method is validated by both simulation and experimental results on an LIM prototype. [ABSTRACT FROM AUTHOR]

This paper presents a speed estimation scheme by combining a second-order sliding-mode observer (SMO) with the model reference adaptive system (MRAS) in the sensorless-vector-controlled linear induction motor (LIM) drives for medium-low speed maglev applications. A state space-vector model of the LIM considering the dynamic end effects is rearranged in order to be represented by the form of the super-twisting algorithm (STA). Then, an STA-SMO-based stator current observer of the LIM with Popov's hyperstability theory is designed, which is used to replace the reference model of the MRAS-based scheme. Correspondingly, the actual stator current model is regarded as the adaptive model of the MRAS for speed estimation. Meanwhile, because the variation of stator resistance associated with stator temperature may lead to a large estimated error and even system instability, a parallel stator resistance on-line identification scheme is adopted in the proposed speed estimation scheme to reduce the speed error and improve the stability of the sensorless control system. Compared to the speed estimation schemes based on the Luerberger observer with MRAS and the single-manifold SMO, the proposed speed estimation scheme exhibits better estimated performance. The effectiveness and feasibility of the proposed speed estimation scheme have been verified by simulation and hardware-in-the-loop tests. [ABSTRACT FROM AUTHOR]

The traction characteristics of a linear induction motor (LIM) are quite different from those of a rotary induction motor (RIM) due to the parameters variations caused by longitudinal end effect, transversal edge effect, and so on. The conventional indirect field-oriented control (IFOC) scheme of the LIM based on flux attenuation compensation is not suitable for high-power traction drives due to the deviation of current and thrust characteristics. In this paper, the traction characteristics of the LIM and RIM are compared from different perspectives. The performance of different control schemes of the LIM is discussed with consideration of the output limitations of the inverter. The IFOC scheme based on optimized slip frequency for the LIM is proposed. By dynamically adjusting the d- and q-axis reference currents and corresponding closed-loop control, the output thrust of the LIM is shifted close to the peak operation point. The average output thrust of the LIM can be increased without increasing the primary current, which can reduce the influence of end and edge effects on thrust performance. The effectiveness of the proposed scheme is verified by both simulation and experiments on an LIM metro vehicle. [ABSTRACT FROM AUTHOR]

This paper discusses the traction performance of a single-side linear induction motor and a single-side coreless Halbach permanent magnet linear synchronous motor (PM-LSM) for the mid- and low-speed maglev train. Based on a typical midand low-speed maglev transit system, the overall performance of the two kinds of propulsion motors was analyzed by the finite element method. By comparing the performance of the single-side coreless Halbach PM-LSM at different magnetization direction of the PMs of the Halbach array, the optimal angle between the magnetization direction of two adjacent PMs was found. In order to achieve the higher propulsion efficiency of the single-side coreless Halbach PM-LSM, various cross-sectional shapes of the conductor were analyzed. The analytical results indicate that the coreless Halbach PM-LSM is more suitable for the mid- and low-speed maglev train in urban rail transit system. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) is widely used for accurate design and analysis of electric machines; however, it suffers from long execution time. In this paper, for the first time hardware acceleration of two-dimensional FEM for a single-sided linear induction motor on the field programmable gate array (FPGA) is proposed. The nonlinearity of the iron core as well as the movement are taken into consideration. A new sparse solver is proposed based on left-looking Gilbert–Peierls algorithm for the system of linear equations of FEM that need to be solved in different iterations and time steps. Implementation of the model is performed in a massively paralleled and deeply pipelined hardware architecture using VHDL coding with single precision floating-point number representation. The proposed emulation was performed at various time steps resulting in significant average speedup of 9.73 times in comparison with JMAG-Designer as a commercial finite element software, and the overall hardware latency of each time step for the emulation was 49.2 ms in average with minimum achievable FPGA clock of 5.59 ns. [ABSTRACT FROM PUBLISHER]

This paper proposes the theoretical framework and the experimental application of the active disturbance rejection control to linear induction motors. Such a nonlinear control (ADRC) technique can be viewed as a particular kind of input–output linearization control, where the nonlinear transformation of the state is not computed by means of the model, but it is estimated online. Such an approach permits to cope with unmodeling dynamics, as well as uncertainty in the knowledge of the model parameters and exogenous disturbances. The effectiveness of the proposed ADRC control law has been verified both by numerical simulations and experimentally on a suitably developed test setup. Moreover, the results have been compared with those achievable with the model-based feedback linearization control. [ABSTRACT FROM AUTHOR]

The disk electrodynamic suspension device (DEDSD) features stable suspension capability, simple structure, low cost, and no mechanical rotation. For analysis and design optimization of the DEDSD, an accurate whole space harmonic force model utilizing magnetic vector potential (MVP) is developed in this paper. The DEDSD is unfolded along the circumference direction and equivalent into a special linear induction motor (LIM). Then, a 2-D MVP method for the equivalent LIM is derived where the longitudinal discrete distribution of coils is represented by longitudinal space harmonics. The 2-D MVP method is further expanded to a 3-D MVP method where new boundary conditions are derived and the transverse edge effect is represented by transverse space harmonics. Consequently, a whole space harmonic force model of the DEDSD is obtained from the 3-D MVP method. Characteristics of the whole space harmonics are analyzed and proper orders are chosen. Finally, the proposed model is verified by experiments on a prototype. [ABSTRACT FROM PUBLISHER]

We devised a linear induction motor (LIM) that uses the close-ended coated superconductor coils as the secondary to explore the potential solutions of enhancing the thrust performance at large clearance, which is generally required for the linear propulsion of transit systems. In this proposal, the coated superconductor coils are embedded into a ferromagnetic yoke whose function is to guide and concentrate the travelling fields generated by the three-phase conventional stator. To make a preliminary study before the laboratory demonstration, we built a numerical model of this proposal by resorting to the finite-element software of MagNet, a recognized professional tool to simulate the electrical machines in the scientific community. Through a treatment of the power law, the developed numerical model has included the nonlinear constitutive law of superconductor, which is currently thought to be difficult in the MagNet environment. This general treatment takes a step forward toward the use of the professional software to perform complex simulations of the superconducting machines. Based on the numerical model, we carried out a set of transient studies on the proposed LIM to observe the distributions of travelling flux, the starting characteristics, and the time evolutions of thrust and speed. The achieved results clearly display that the proposed LIM has advantages over the conventional type and could be thereby regarded as a candidate for developing high thrust linear LIM with large clearance. [ABSTRACT FROM PUBLISHER]

The linear induction motor (LIM) has been used in urban rail transit systems in China and other parts of the world. However, specialized specifications for design or assessment of bridges in urban rail transit systems have not yet been established. The electromagnetic force of LIM complicates vehicle-bridge interaction. In this paper, a typical bridge on the Guangzhou metro line 4 is evaluated both experimentally and theoretically to determine vehicle-bridge interaction characteristics. The LIM vehicle is represented by a model of secondary suspension with 6 degrees of freedom, and the bridge is modeled using standard beam elements. The coupled motion equation is formulated using the principle of total potential energy with stationary value in an elastic system and solved by using the Newmark-β method. Field dynamical tests were also performed on the bridge. The calculated and experimental vertical displacement time-histories for LIM trains crossing the bridge were obtained and dynamic factors were developed. A formula for determination of the dynamic factor, which can provide an engineering basis for design and evaluation of bridges in urban rail transit system, is proposed.

Linear induction machines are widely used in transportation systems due to their many advantages. Design and prototyping of electric machines are an expensive and time-consuming process; hardware-in-the-loop simulation provides an efficient alternative. In this paper, a field-programmable gate array-based real-time digital emulation of single-sided linear induction motor with the drive system is proposed. Implementation of the model is performed in both fixed-point using Xilinx system generator and floating-point number representations using a handwritten VHSIC Hardware Description Language code. Then, an evaluation in terms of real-time step-size and accuracy as well as hardware resource utilization is provided. The whole design was fully paralleled, which resulted in a considerable reduction of model execution time. The minimum time step of 2.3 and 0.8 \mu \texts was achieved for floating-point and fixed-point implementations, respectively. The results of the real-time simulation are verified by the experimental results as well as a 2-D finite-element simulation in JMAG software. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis and results obtained with the regenerative braking technique applied to the linear induction motor used for the traction of MagLev-Cobra, an urban transportation vehicle. The motor, with a special geometry, the converter, with bidirectional power flow, and the drive control are reported. An improvement on the motor secondary side was proposed and tested. Traction an attraction forces are measured. An analytical development showed the optimal velocity profile for regenerative braking. Finally, experimental results validated the analyses and showed the weakness of tests on a small track.

In this paper, a study of the performance and experimental results for a low-speed linear induction motor (LIM) with toroidal winding is presented. The main idea behind the proposed winding is to provide better performance and efficiency in space-constrained applications where a LIM with much higher primary length in comparison with the primary width is required. The LIM with toroidal winding in this case enjoys the advantage of short end-connection length, which can provide more superior performance than a distributed winding linear induction motor (DWLIM). Also, as the motor is designed to operate at low speed, the output power, and thus efficiency, would be low, and then the performance of such machines cannot be evaluated in terms of output power or efficiency. However, an improvement in performance, and thus efficiency, may be achieved when the low-speed motor is fed from a low-frequency supply. This paper mainly focuses on the design optimization, prototyping, and performance evaluation of a low-speed LIM with toroidal winding, and also provides a detailed comparison between the LIM with toroidal winding and a DWLIM. [ABSTRACT FROM AUTHOR]

This paper deals with model reference adaptive system (MRAS) speed estimators based on a secondary flux for linear induction motors (LIMs). The operation of these estimators significantly depends on an adaptation mechanism. Fixed-gain PI controller is the most common adaptation mechanism that may fail to estimate the speed correctly in different conditions, such as variation in machine parameters and noisy environment. Two adaptation mechanisms are proposed to improve LIM drive system performance, particularly at very low speed. The first adaptation mechanism is based on fuzzy theory, and the second is obtained from an LIM mechanical model. Compared with a conventional PI controller, the proposed adaptation mechanisms have low sensitivity to both variations of machine parameters and noise. The optimum parameters of adaptation mechanisms are tuned using an offline method through chaotic optimization algorithm (COA) because no design criterion is given to provide these values. The efficiency of MRAS speed estimator is validated by both numerical simulation and real-time hardware-in-the-loop (HIL) implementations. Results indicate that the proposed adaptation mechanisms improve performance of MRAS speed estimator. [ABSTRACT FROM AUTHOR]

Based on the operating principle of linear induction motor (LIM), this paper has analyzed the performance of the LIM consisting of a long sectioned transverse flux stator and a short flat aluminum mover, proposed the basic requirements and working modes of this special type of a catapult, described the optimal design methods of the LIM and discussed in detail some important parameters affecting the operating performance, such as the slot width, pole pairs, and the thickness of the mover. Then, the optimal system design and the discussion of performance are carried out based on the T-type equivalent circuit model with the covered and uncovered sections. The phase current, phase voltage, power capacity, and height are 11359 A, 3000 V, 409 MVA, and 1.73 m, respectively. The launch profile is also derived from the model. To verify the electromagnetic compatibility of the LIM, the 3-D magnetic model is established. The results show that the magnetic fields fall to the earth’s ambient level at 1 m above the stator, which cannot bring low-frequency electromagnetic interference to the environment. [ABSTRACT FROM PUBLISHER]

This paper presents a closed-loop model reference adaptive system (CL-MRAS) speed observer developed for linear induction motor (LIM) drives. Starting from the structure of the CL-MRAS speed observer developed in the literature for rotating induction motors, a corresponding speed observer for LIMs has been developed here. It is based on the LIM dynamic model taking into consideration its dynamic end effects. In particular, the following aspects are original: 1) It employs the voltage and current models of the LIM considering its dynamic end effects, 2) it proposes a net thrust model including the braking force caused by the dynamic end effects; 3) it models the friction load of the LIM drive experimentally obtained with off-line tests. The proposed sensorless technique has been tested on a purposely developed experimental set-up. Results show that the CL-MRAS observer permits the drive to operate down to the speed of 0.01 m/s, i.e., about 0.15% of the rated speed, which is about 20 times lower than the minimum working speed achieved with other observers implemented on the same LIM drive, such as the total least squares (TLS) MRAS observer, the TLS EXIN full-order Luenberger observer, the extended Kalman filter, and, finally, the TLS EXIN Kalman filter. [ABSTRACT FROM AUTHOR]

A variable pole pitch linear induction motor (VPPLIM) is proposed as a new member of the family of electromagnetic aircraft launch system (EMALS). With proper designing of the variation of the pole pitch, the VPPLIM could accelerate the aircraft almost uniformly at the condition of the usual ac supply, avoiding the use of large-scale power electronic converters. Special considerations in the design of VPPLIM, such as the structure topology, the variation of the pole pitch, and the winding arrangement are discussed in detail in this paper. The acceleration performance of the VPPLIM fed by a constant-voltage constant-frequency supply is analyzed by means of the quasi-steady-state 2-D magnetic field model and the difference model of mover’s dynamics. A two-stage method is proposed to simulate the acceleration performance of the VPPLIM based on a 2-D thrust table of the motor achieved by the finite-element method. The calculated features of the prototype VPPLIM consist well with those expected for EMALS. [ABSTRACT FROM PUBLISHER]

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This first part of a paper, divided into two parts, deals with the theoretical formulation of the input–output feedback linearization (FL) control technique as to be applied to linear induction motors (LIMs). Linear induction motors, differently from rotating induction motors (RIMs), present other strong non-linearities caused by the so-called dynamic end effects, leading to a space-vector model with time-varying inductance and resistance terms and an additional braking force term. This paper, starting from a dynamic model of the LIM taking into consideration its dynamic end effects, previously developed by the same authors, defines a feedback linearization (FL) technique suited for LIMs, since it inherently considers its end effects. It further emphasizes the role of the LIM dynamic end effects in the LIM control formulation, highlighting the differences with respect to the corresponding technique for RIMs. It describes the control design criteria, taking also into consideration the constraints on the control and controlled variables, arising from the application of such control technique in a real scenario. The second part of this paper describes the set of tests, both in numerical simulations and experiments, performed to assess the correctness of the proposed control technique. [ABSTRACT FROM AUTHOR]

This is the second part of a paper, divided in two parts, dealing with the application of the input–output feedback linearization (FL) control technique to linear induction motors (LIMs). The first part has treated the theoretical formulation of the input–output feedback linearization control technique as to be applied to linear induction motors. This second part describes the set of tests, both in numerical simulations and experiments, performed to assess the validity of the control technique. In particular, it addresses the issues of the sensitivity of the FL control versus the LIM electrical parameters’ variations and the improvements achievable by considering the LIM dynamic end effects in the control formulation. The proposed FL technique has been further compared, under the same closed-loop bandwidths of the flux and speed systems, with the industrial standard in terms of high performance control technique: field oriented control (FOC). [ABSTRACT FROM AUTHOR]