Permanent Magnet Linear Synchronous Motor Research Articles

Vertical Dynamic Response Analysis of HTS Maglev Vehicle Excited by a Designed Coreless-Typed PMLSM

High-temperature superconducting (HTS) pinning maglev has the potential for high-speed application because of its advantages of passive self-stabilization, energy conservation, environmental protection, and no inherent magnetic resistance along the forward direction. The HTS pinning maglev can realize non-contact levitation and guidance. Permanent magnet linear synchronous motor (PMLSM) is suitable for HTS pinning maglev to realize non-contact drive. However, in addition to the longitudinal driving force for the HTS pinning maglev train, the PMLSM also produces the normal force which will cause additional excitation on the maglev train and affect its levitation height and vertical dynamic response. In this paper, a coreless-typed PMLSM is designed for HTS pinning maglev driving system, and the driving force and normal force characteristics of the motor under different air gaps are calculated. Then, a vertical dynamic model of the HTS pinning maglev vehicle is established. The vertical dynamic response of the HTS pinning maglev vehicle excited by the normal force of PMLSM and permanent magnet guideway (PMG) irregularity is simulated and analyzed. This work can provide a reference for the study of the electromechanical coupling effect between the HTS pinning maglev levitation system and linear motor driving system.

Suppressing the Eddy Current Damping of the Permanent Magnet Linear Synchronous Motor by Setting the Toothed Cooling Plate

To enhance the linear motor thrust density, scholars have focused extensively on cooling systems. Conventional cooling plates induce eddy current damping in the time-varing magnetic field, decreasing the dynamic characteristics of the motor. Therefore, a toothed cooling plate is proposed, which effectively reduces the metal water-cooled plate’s eddy current damping and has good heat dissipation capacity. The layered model is used to determine the damping of the cooling plate covered on the armature, and the factors affecting the damping are concluded. Eddy currents on the cooling plate are vectorized in this structure via laser cutting. On the basis of the model, a scheme with a secant spacing of 1/3 pole pitch is chosen, then a comparison of three different structural types follows. The variation characteristics of their damping are described in detail. Finally, the thermal network model analysis and the temperature rise experiment are conducted to summarize the heat dissipation characteristics of the toothed cooling structure.

Optimal force control of a permanent magnet linear synchronous motor with multiple shuttles

Using permanent magnet linear synchronous machines for transportation tasks offers a higher flexibility in production plants compared to conventional conveyor solutions. In this context, passive transportation devices (shuttles) with permanent magnets are commonly used. When multiple shuttles are operated in close vicinity, disturbances due to magnetic interaction can occur. To allow for high-speed operation of the motor with high position control accuracy, these coupling effects must be considered. This paper presents a model-based control strategy that is based on a magnetic equivalent circuit model which is able to describe the nonlinear magnetic behavior at low computational costs. A framework is derived for the model calibration based on measurements. An optimal control scheme for the multi-shuttle operation is derived that allows to accurately track the desired tractive forces of the shuttles while minimizing the ohmic losses at the same time. The control concept is experimentally validated on a test bench and compared to a state-of-the-art field-oriented control concept typically used in industry.

Analysis of Permanent Magnet Linear Synchronous Motor Made by Oriented Silicon Steel Sheet

A novel structure of the permanent magnet linear synchronous motors (PMLSMs) is proposed in this paper, in which oriented silicon steel sheet (OSSS) instead of traditional non-oriented silicon steel sheet (NOSSS) is used as the mover core material. Based on the characteristics of longer tooth magnetic circuit of the PMLSMs with similar number of poles and slots structure, the rolling direction of the OSSS is set to be consistent with the magnetic circuit direction of the teeth, so that the motor can improve the magnetic permeability and anti-saturation ability. The operating condition of OSSS in PMLSMs is derived through thrust formulae and magnetic circuit calculations. The thrust performance and saturation of two PMLSMs with different silicon steel sheets are compared and analyzed by finite element simulation, and related prototypes are produced. The simulation and experimental results show that the use of OSSS as the mover core material can increase the electromagnetic thrust and overload capacity.

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.

Back EMF-Based Dynamic Position Estimation in the Whole Speed Range for Precision Sensorless Control of PMLSM

Back EMF-based sensorless control strategies for permanent magnet linear synchronous motor (PMLSM) have the potential to simplify the mechatronic system, reduce the cost and prolong the service life. However, the poor performance in the low-to-zero speed region limits their application range. In this paper, a novel back electromotive force (EMF)-based mover position estimator is proposed to achieve consistent good accuracy in the whole speed range including high speed, medium speed, low speeds, temporary standstill, and speed reversals. The three-phase flux linkages are obtained by directly calculating the integration of back EMF. To overcome the curve drift caused by the integrator, this paper proposes a jumping correction algorithm (JCA) and a uniform correction algorithm (UCA). The mover position is calculated from the corrected flux linkages. This paper also realizes a closed-loop sensorless trajectory tracking control system using the proposed position estimator. Experimental results on a PMLSM demonstrate that the proposed position estimator can guarantee stability and accuracy in the whole speed range. Compared with existing back EMF-based methods working only well in high-speed region and usually with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$mm$</tex-math></inline-formula> -level accuracy, the proposed method achieves an accuracy of sub-200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu m$</tex-math></inline-formula> regardless of the reference trajectory, and has exciting prospect in industrial applications.

Adaptive super-twisting-based nonsingular fast terminal sliding mode control of permanent magnet linear synchronous motor

In this study, to reduce the impact that permanent magnet linear synchronous motor (PMLSM) servo system on the sensitivity of external and internal interferences, an adaptive super-twisting-based nonsingular fast terminal sliding mode control (AST-NFTSMC) scheme is put forward. First of all, the mathematical model of PMLSM contains uncertainties is set up, and the control law is established to make position signal converge to given state asymptotically. Second, by introducing the super-twisting algorithm, the chattering caused by nonlinear switching function in traditional method is weakened. However, in actual industrial situations, it is difficult to determine the boundary of lumped disturbance, which makes the switching gains in super-twisting algorithm cannot be accurately selected. Therefore, an adaptive law is introduced to adjust the switching gains online, so that the gains can be dynamically adjusted within a limited range during operation, so as to further weaken chattering. Finally, the practicability of AST-NFTSMC is proved in theory and verified by system experiments. The experimental results prove that AST-NFTSMC can significantly weaken chattering, and result in robust control performance.

An improved global fast terminal high-order sliding mode control strategy based on novel reaching law for improving PMLSM dynamic performance

Due to its better power density and efficiency, permanent magnet linear synchronous motor (PMLSM) is ideal for generating electricity with wave power device (WPD). Nevertheless, when the PMLSM for the WPD control system is impacted by changes in motor characteristics and interference from the outside environment, it typically is unable to deliver high-quality dynamic performance on schedule. Although sliding mode control (SMC) has been introduced to improve the robustness of the system greatly in recent decades, traditional methods still have problems such as slow dynamic response, poor anti-disturbance performance, large chattering amplitude, and phase delay. To solve the above defects in SMC, an improved global fast terminal high-order SMC strategy based on novel reaching law for improving PMLSM dynamic performance is proposed in this paper, as well as the sliding mode surface and control law of the speed controller is designed based on this control strategy. The proposed strategy would not only shorten the dynamic response time but also weaken the chattering magnitude in the sliding mode stage, improving the dynamic performance of both speed and current. The simulation results demonstrate that in comparison to the traditional PI and SMC control methods, the improved strategy proposed in this paper can further enhance the control performance of the linear motor, demonstrating the method’s enormous potential in the double closed-loop vector control system of PMLSM for WPD.

A novel magnetic circuit and structure for magnetic levitation ruler

The single axis linear displacement measurement system of CMM is composed of grating ruler, servo motor and linear motion mechanism. Although the measuring accuracy of grating ruler is high, the accuracy of servo motor and linear motion mechanism is low. Therefore, the complex structure limits the measurement accuracy of the linear displacement measurement system. This paper introduces a novel linear displacement measurement system named magnetic levitation ruler. According to the working principle of grating ruler and the characteristics of magnetic levitation technology, the magnetic circuit design and structural design of magnetic levitation ruler are completed in this paper. The mover core of the magnetic levitation ruler is in the stable working magnetic field provided by the stator yoke. The horizontal control coil wound on the mover core can obtain more stable ampere force to improve the control accuracy of the mover core displacement. Therefore, the mover core can be moved in step mode, and the length of each step is fixed. Each step is the minimum scale of the magnetic levitation ruler. Therefore, the mover core can implement displacement measurement while moving in a linear motion. This paper analyzes the working principle of levitation, horizontal motion, and displacement measurement of magnetic levitation ruler, and determines the structural materials and parameters of magnetic levitation ruler with the help of finite element analysis software. The simulation results show that the levitation force of the magnetic levitation ruler is proportional to the current passing through the levitation coils, and the thrust of the horizontal control coil is less disturbed by the magnetic field. Compared with the linear displacement measurement system with rotational servo motor or permanent magnet synchronous linear motor as the core, the magnetic levitation ruler has stable magnetic field, strong controllability, high integration, and is easier to achieve high-precision control.

Diffeomorphism-Based Robust Bounded Control for Permanent Magnet Linear Synchronous Motor With Bounded Input and Position Constraints

This article develops a diffeomorphism-based robust bounded control (DRBC) for the permanent magnet linear synchronous motor system subject to inequality constraints (i.e., bounded input and position constraints) and uncertainties. The uncertainties, including parameter uncertainties and external disturbances, are potentially nonlinear and fast time varying. The bound of the uncertainty is described by a fuzzy set. To overcome the bounded input constraint, a robust bounded control is proposed based on a novel input diffeomorphism scheme, which is in a deterministic form and not if–then rule based. Furthermore, to overcome the bounded position constraint, a transformed system is formulated by a state diffeomorphism scheme, which transforms the bounded state-constrained system to an unconstrained one. Thus, the output of the controlled system can be restricted to a prescribed range. The DRBC guarantees both the uniform boundedness and the uniform ultimate boundedness of the transformed system. A fuzzy performance index, which combines the steady-state performance (the average fuzzy performance) and control effort, is then established based on the fuzzy description of uncertainty. As a result, the design parameter optimization can be solved by minimizing the performance index. Experimental results demonstrate that the DRBC is of superior tracking performance and robustness without violating the prescribed inequality constraints.

A Novel Robust Adaptive Nonsingular Fast Integral Terminal Sliding Mode Controller for Permanent Magnet Linear Synchronous Motors

To realize the high-precision tracking control of permanent magnet linear synchronous motor (PMLSM) in complex working conditions, a control system with strong robustness must be equipped for PMLSM, so this article proposes a novel robust adaptive nonsingular fast integral terminal sliding mode control (ANFITSMC) strategy. First, a dynamical mathematical model of PMLSM is established to describe the thrust and unknown uncertainty in the motion process. Second, considering that the uncertain factors, such as external disturbances and high-frequency noises in the system, may cause the degradation of position tracking accuracy, a nonsingular fast integral terminal sliding mode control (NFITSMC) method that only requires position and velocity information to estimate the lumped uncertainty of the system is designed. Meanwhile, the adaptive control algorithm is used to estimate the lumped uncertainty dynamically in real time, thus weakening the chattering and improving the tracking accuracy. Also, the stability of this control system is proven by utilizing the Lyapunov stability theory. Finally, the high-precision positioning experimental platform is used to carry out experimental tests with different position trajectory commands. The experimental results show that the proposed ANFITSMC method not only enables the system to have higher control accuracy but also ensures a more robust performance.

Mathematical Model to Predict Thrust Ripple in Double Salient Flux-Modulated Linear Permanent for Five-Axis Gantry Robot Under Field Oriented Control

This article proposes a detailed mathematical <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dqn</i> axes dynamic modeling of a double saliency flux modulated permanent magnet linear synchronous motor used as the linear actuator for the five-axis gantry robot system to study thrust ripple characteristics. To derive the model, the machine double saliency is considered by analyzing the effect of the cross-coupling inductances into the dynamic voltage equation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dqn</i> axes. The electromagnetic performances such as the electromagnetic thrust and the thrust ripple is formulated to check the maximum limit of the thrust ripple at the initial design stage using the derived model. The whole process is validated using 2-D, 3-D finite element analysis, and manufactured prototype under driving conditions.

Adaptive Model Predictive Current Control for PMLSM Drive System

This article proposes an adaptive model predictive current control (AM-MPCC) for surface-mounted permanent magnet linear synchronous motor systems to simultaneously enhance the robustness against permanent magnet flux, inductance, and resistance mismatches. First, the conventional continuous control set model predictive control is analyzed, illustrating that parameter variations will inevitably deteriorate the current regulation performance. Then, an adaptive predictive model, which involves a disturbance term and an optimized current change rate coefficient, is proposed. The optimal coefficient is estimated using a steady-state incremental model and the steepest descent method at each control period. A discrete-time sliding mode disturbance observer is devised based on the adaptive model with updated coefficients to achieve the disturbance term. Finally, an exponential reaching law-based-reference trajectory is defined for the cost function of AM-MPCC to adjust the current approach trajectory. Experimental results verify the excellent robustness performances of the proposed method.

Trajectory-Regulation-Based Segmented Control for Dead Center Positions Tracking of Free-Piston Linear Generator

Free-piston linear generator (FPLG), as a novel energy converter, has attracted wide attention due to its unique operating characteristics. However, the high-precision and robust tracking of the dead center positions in the presence of frequent combustion variation is still a tricky problem. In this respect, in this article, we present a trajectory-regulation-based segmented control (TRBSC) to actively control the linear electric machine (LEM) of FP LG. The target stroke is divided into the high-speed zone and low-speed zone, where active tracking of the input reference trajectory of LEM and free damped motion are performed separately. Especially, the input trajectory is selected as a variable sinusoidal reference velocity profile, which is adjusted by the combinations of the dead center errors. The segmented control decouples the specific interaction between the dead center positions and velocity curve, reducing the heavy dependence of the algorithm on speed tracking accuracy. A full theoretical analysis is provided with emphasis on the regulation rules of the reference speed profile based on the modeling of the displacement profiles. The performance of the TRBSC is experimentally verified on an 18 kW permanent-magnet linear synchronous motor setup in motoring mode.

A Novel Design of Permanent Magnet Linear Synchronous Motor with Reduced End Effect

In response to the end effect of the permanent magnet linear synchronous motor, this paper proposes an improved modular motor structure. To compute its electromagnetic characteristics, a subdomain model that converts the Cartesian coordinate system into a polar coordinate system through coordinate transformation is further formulated, thus significantly reducing programming difficulty. The analytical results are compared with those of the finite element method and indicate that the subdomain model can accurately consider the effects of end and flux barriers. Moreover, the magnetic field distribution inside the motor is applied to explain the end force abatement, and the suggested flux barrier width is obtained. Finally, the modular structure is applied to a 9-slot, 10-pole permanent magnet linear synchronous motor. The simulation results show that the modular structure can effectively suppress the end effect of the linear motor, and the proposed subdomain model applies to the design of the modular motor.

Comparative investigation and optimization of a direct cooling structure for the primary core and windings in permanent magnet synchronous linear motors

The permanent magnet synchronous linear motors with high acceleration and high thrust density are favored in many applications, but accompanied by a rapid temperature rise. This paper investigates a novel direct cooling structure for the primary core and windings, integrated with the advantage of a filler with high thermal conductivity. It can greatly reduce the thermal resistances between the heat source and the coolant and thus improves the cooling performance. Detailed numerical calculations and analysis are carried out to reveal the electromagnetic performance and thermal benefits of the direct cooling structure compared with the traditional back yoke cooling structure. In addition, an improved thermal network model is proposed with the help of numerical model. It can not only improve the calculation accuracy of the average winding temperature, but also predict the maximum temperature without additional computational burden. Furthermore, the improved thermal network model can be an initial design model to quickly optimize the direct cooling structure. Finally, experiments are conducted on a prototype to verify the excellent cooling performance of the proposed cooling structure and the effectiveness of the improved thermal network model.

A stochastic configuration networks-based nonsingular fast terminal sliding mode control approach for indirect matrix converter-driven permanent magnet linear synchronous motors

To further improve the fast and stability of the control system of an indirect matrix converter (IMC) driven permanent magnet linear synchronous motor (PMLSM), a nonsingular fast terminal sliding mode control (NFTSMC) algorithm based on the disturbance observer of stochastic configuration networks (SCNs) is proposed. The NFTSMC algorithm is used to design the outer loop controller, which can reduce the influence of the IMC by the power supply voltage and high-frequency harmonics generated by switching. To further reduce the disturbance of IMC-PMLSM during operation, in this paper, a nonlinear disturbance observer based on SCNs is constructed, which solves the drawback that the traditional disturbance observer needs to adjust the parameters frequently under different working conditions. Finally, a simulation model is established on the MATLAB/Simulink platform to verify the effectiveness and advantages of the proposed control method.

Analysis of linear motor with symmetrical EMF vector for household elevator application

&lt;span lang="EN-US"&gt;Linear permanent magnet synchronous motor (LPMSM) has emerged as a viable alternative to other linear motors for higher thrust lifting action. With the advancement of permanent magnets, LPMSM could contribute to energy conversation while also being suitable for applications requiring higher thrust, such as elevator. However, because the existing LPMSM is larger in size, it requires more space to be equipped with a household elevator. To address this issue, a new LPMSM with increased thrust capability has been proposed. The new LPMSM is modelled and analyzed in terms of back EMF and force in this paper. For improved performance, a symmetrical EMF vector is applied to the new LPMSM. In terms of back EMF and force, 4 LPMSM models are studied. According to the results, 6 slot 4 pole has the highest back EMF when compared to the others. As a suitable combination of slot and pole, a symmetrical EMF vector is the suggested LPMSM at the end of this research. &lt;/span&gt;

Integrated Sliding Mode Velocity Control of Linear Permanent Magnet Synchronous Motor with Thrust Ripple Compensation

In this paper, a compound sliding mode velocity control scheme with a new exponential reaching law (NERL) with thrust ripple observation strategy is proposed to obtain a high performance velocity loop of the linear permanent magnet synchronous motor (LPMSM) control system. A sliding mode velocity controller based on NERL is firstly discussed to restrain chattering of the conventional exponential reaching law (CERL). Furthermore, the unavoidable thrust ripple caused by the special structure of linear motor will bring about velocity fluctuation and reduced control performance. Thus, a thrust ripple compensation strategy on the basis of extend Kalman filter (EKF) theory is proposed. The estimated thrust ripple will be introduced into the sliding mode velocity controller to optimize the control accuracy and robustness. The effectiveness of the proposal is validated with experimental results.

Improved Position Sensorless Control for PMLSM via an Active Disturbance Rejection Controller and an Adaptive Full-Order Observer

Position and speed information are very important to realize the efficient control for permanent magnet linear synchronous motor (PMLSM). In order to obtain more accurate position estimation signals, this article investigates an improved position sensorless control method for PMLSM by combining an active disturbance rejection control (ADRC)-based speed controller and an adaptive full-order observer (AFO)-based position estimator. The AFO is constructed based on model reference adaptive system (MRAS), which can obtain more accurate position estimation signal by introducing a current error feedback gain matrix. However, there are lots of thrust fluctuations existing in PMLSM caused by end effect, which will affect the estimation accuracy. Since it is difficult to reduce the influence of thrust fluctuation by only improving the observer itself, an ADRC-based speed controller is designed to improve the anti-interference ability of control system, thereby improving the position estimation accuracy. For the ADRC controller, an second-order linear extended state observer (LESO) is designed to observe the thrust fluctuation and an nonlinear state error feedback (NLSEF) control law is introduced to compensate the observed disturbance. The effectiveness and superiority of the proposed method have been verified by simulation and experimental results.