Electromagnetic Thrust Research Articles

An analytical model for a coaxial electromagnetic recuperator considering end effect

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

Electromagnetic Characteristics Analysis and Thrust Fluctuation Optimization in Integrated Propulsion, Levitation, and Guidance Systems

Electromagnetic Characteristics Analysis and Thrust Fluctuation Optimization in Integrated Propulsion, Levitation, and Guidance Systems

Air‐gap field prediction in tubular doubly sided surface magnet machine using Bessel–Fourier series

Abstract2‐D air‐gap magnetic field distribution is the essential prerequisite of electrical machine analysis. Because of the natural periodicity of rotary machines, Fourier analysis is a suitable choice for air‐gap field prediction. However, due to the end‐effect, periodicity is not present in linear machines and the Fourier series is not appropriate. In engineering mathematics, a rigorous method of solving partial differential equations is the separation of the variables method (SVM) which is based on the hypothesis that the field solution is in the form of the product of two functions of orthogonal directions; for example, in an axisymmetric structure, a longitudinal harmonic function (LHF) and a radial harmonic function (RHF). A particular case of these functions is trigonometric functions, which result in the Fourier series. SVM is imposed in a different manner, where RHF is approximated by the Bessel–Fourier series and consequently LHF has a (piecewise) exponential behaviour. This choice of basis functions not only serves the purpose of modelling the end‐effect but also removes the Gibbs phenomenon, that is, it precisely models discontinuities of flux density at the surface of PMs. A numerical case‐study of a slotless double‐sided linear tubular surface‐PM machine shows that the piecewise exponential approximation can attain 1% error while utilising only three harmonics, whereas the trigonometric approximation, due to the Gibbs phenomenon, slowly arrives at 20% error with 100 harmonics for approximating flux density. Results of both methods were validated using the finite element method (FEM). Additionally, it was discovered that the computational complexity of the model is independent of varying position; therefore, the analytical method could yield the back electromotive force and electromagnetic thrust force for a number of 320 positions at merely 0.2 s while the FEM software required 5 min.

Improved performance of linear induction motors based on optimal duty cycle finite-set model predictive thrust control

Linear induction machines (LIMs) find widespread adoption in various applications, owing to their inherent advantages such as low noise, compact turning radius, and excellent climbing capability. LIMs are extensively utilized in linear metro applications. However, in practical operations, the output thrust shrinks with the increase in speed, which is attributed to end effects. This phenomenon leads to a reduction in efficiency. In addition, fluctuations in the normal force impact system stability, posing disturbances to the suspension system. To address these challenges, this paper suggests a finite-set model predictive thrust control (FS-MPTC) for a drive system employing a linear induction motor (LIM). The FS-MPTC optimizes the duty cycle for the active voltage vector and allocates the remaining period to one of the zero voltage vectors. The selected zero voltage vector reduces the switching transition between it and the active voltage vectors. The duty cycle is calculated for the six voltage vectors by incorporating the deadbeat concept and the derivative value for the electromagnetic thrust. In the prediction stage of the FS-MPTC, the computed duty cycle and the corresponding voltage vector are used simultaneously and repeated for the six voltage vectors. The cost function comprises two terms: the error between the reference thrust and predicted thrust value as the first term and the error between the rated primary flux linkage and its predicted value as the second term. The reference thrust is generated from the outer speed control loop. To validate the effectiveness of the proposed control approach, Japanese 12000 linear induction machine parameters are employed for verification. Comparative analysis of the performance between the suggested control method with the optimal duty cycle and the same process with a fixed duty cycle demonstrates superior performance when utilizing the optimal duty cycle. Finally, the proposed FS-MPTC with the optimal duty cycle offers a promising solution to enhance the operational efficiency of the LIM-based drive systems.

Study on the Selection of Coil Energization Directions in Multistage Synchronous Induction Coil Launcher

In order to enhance the initial velocity and energy conversion efficiency of multi-stage synchronous induction coil launchers, the direction of coil energization for the drive coils is studied. There are typically two energization methods for multi-stage launching devices: (1) PP (Positive-Positive), where positive current is applied to all drive coils, and (2) PN (Positive-Negative), where currents in opposite directions are alternately applied to the drive coils. A finite element model of a four-stage coil launcher is established in ANSYS2022R2, and the acceleration effects of the armature under different inter-stage distances are analyzed for two energization methods. The study reveals that the PN configuration does not always result in higher armature velocities compared to the PP configuration under different inter-stage distances. The theoretical explanation is provided for the variations in the forces exerted by the previous and next drive coils on the armature during the acceleration process. It is found that the magnitude of the induced current in the previous and next drive coils during the launch process is influenced by the inter-stage distance, which in turn affects the electromagnetic thrust coupled with the armature. Thus, the method of determining the direction of current in the launching device coil is obtained.

Analysis and Optimization Design of U-Shaped Ironless Permanent Magnet Linear Synchronous Motor

The working speed of the U-shaped ironless permanent magnet linear synchronous motor is determined by the frequency and pole pitch. When the motor’s working speed is required to be constant, different combinations of frequency and pole pitch can be chosen. This article mainly discusses the influence of the pole pitch on the motor performance when other parameters are kept constant. First, the magnetic field of the motor permanent magnet is analyzed using the equivalent magnetizing current method to discuss the relationship between the pole pitch and the motor air gap magnetic field. Then, the finite element method is used to analyze the influence of the pole pitch on the motor air gap magnetic field, transverse edge effect, and electromagnetic thrust considering the saturation effect of the magnetic yoke. The research shows that under the conditions of constant motor basic structural parameters and speed, and the same amount of permanent magnet material, both the air gap magnetic density and the motor thrust line density have maximum values as the pole pitch changes. The research results have certain guiding significance for the design of this type of motor.

A Critical Review on Superconducting Semi-Cryogenic Fuels for Advanced Space Propulsion and Deep Space Missions

The exploration of deep space necessitates revolutionary propulsion technologies to overcome the vast distances involved. This review critically evaluates the potential of superconducting semi-cryogenic fuels as a game-changing approach for spacecraft propulsion. Superconductors, exhibiting zero electrical resistance at low temperatures, offer significant advantages for efficient electromagnetic thrust generation. However, achieving the ultra-low temperatures typically required for superconductivity presents logistical challenges for spacecraft. This review explores the use of semi-cryogenic fuels like liquid hydrogen and methane, enabling operation at more manageable temperatures while leveraging the benefits of superconductivity. The review delves into the challenges of boil-off loss and analyzes various mitigation techniques like multilayer insulation, 3M glass bubbles, active cooling systems, and Zero Point Boil Off (ZBO). Furthermore, it highlights the potential performance gains of superconducting semi-cryogenic propulsion systems, including significant weight reduction and improved efficiency. Critical considerations such as radiation exposure and the need for further research in high-temperature superconductors and computational modeling are discussed. Overall, this review underscores the promising path that superconducting semi-cryogenic fuels offer for advancing deep space exploration.

Space Harmonics Effects on Performances of Linear Induction Motors: Modelization and Characterization

This article presents the impact analysis of space harmonics’ presence on a single-sided three-phase linear induction motor, along with a comprehensive parametric investigation. The presence of space harmonics often reduces the linear induction motor’s performance. The electromagnetic phenomena are governed by Maxwell’s equations. The chosen mathematical model uses a 2D formulation with magnetic vector potential. The model implementation is performed using the finite element method on the free Gmsh-GetDP platform. The electromagnetic thrust is calculated in the current excitation case using two numerical models of the finite element method with and without term-generating space harmonics in order to highlight their effect. The adaptation to voltage supply operation is obtained via equivalent electric circuits through the calculation of the operational impedance. The choice of the machine’s parameters by the designer in order to enhance its performance or reduce energy consumption is a difficult task. The analysis and the determination of the dependence of the parameters and the performance are necessary. The main objectives of this study are to determine this dependency and to analyze the space harmonic impact of the linear induction motor’s parameters on its performances. A comparative exploration of space harmonics’ presence using two numerical models (single and multiharmonics) and an assessment of the parametric effect of space harmonics’ presence on various machine characteristics such as thrust, efficiency, and power factor have been carried out. The motor’s characteristics (i.e., thrust, efficiency, and power factor) strongly depend on parameters such as the pole pair number and conductivity. Improving the operation and maximizing the performance of such a machine for a given specification requires the use of optimization algorithms. Motor characteristics (thrust, efficiency, and power factor) are highly dependent on parameters such as the number of pole pairs and conductivity.

Novel Virtual Winding Current Controller for Suppression of Linear Permanent Magnet Machine Electromagnetic Thrust Ripple

Thrust force ripple, including no-load detent force and electromagnetic thrust ripple, worsens the precision of linear permanent magnet machine (LPMM) control system. Asymmetrical current injection algorithm has been proposed for the suppression of electromagnetic thrust ripple, and the key point of the algorithm is positive- and negative-sequence (PNS) current closed-loop control. To achieve better steady-state and dynamic performance, a novel high-bandwidth current controller is proposed in this paper. A dual three-phase control system composed of three-phase virtual winding and the three-phase LPMM is introduced. According to the dual three-phase topology, PNS components are decoupled by a novel coordinate transformation, and the proposed controller avoids the use of filters or sophisticated algorithms for extraction of PNS currents. Experimental results based on a linear vernier permanent magnet machine (LVPMM) are presented. It verifies that the asymmetrical current control strategy based on the novel PNS current controller reduces electromagnetic thrust ripple by more than 60% compared with symmetrical three-phase current control.

Accurate Modeling and Optimization of Electromagnetic Forces in an Ironless Halbach-Type Permanent Magnet Synchronous Linear Motor

In order to solve the electromagnetic force optimization problem of a high-power-density ironless Halbach-type permanent magnet synchronous linear motor, this paper adopts an electromagnetic force optimization method based on magnetic field analysis, electromagnetic force modeling, and genetic algorithm optimization: Firstly, the magnetic field of the Halbach permanent magnet array is solved by the combination of the equivalent magnetization strength method and the pseudo-periodic method, which takes into account the influence of the edge effect of the secondary magnetic field, and the magnetic field of the primary winding is solved by Fourier series expansion method. Secondly, the Maxwell tensor method is used to establish the functional relationship between the electromagnetic thrust and the main structural parameters of the unilateral motor. Finally, based on the parameter sensitivity analysis of the optimized variables and the response surface calculation, the optimal combination of the optimized variables to meet the optimization objective is found by a genetic algorithm. This method of the accurate modeling and optimization of an electromagnetic force can accurately calculate the motor air gap magnetic field and electromagnetic thrust, and the optimization speed is fast, which can greatly save time. The optimization results show that, under the premise of constant input power, the unilateral average thrust of the motor is increased by 18.75%, the peak value of thrust fluctuation is decreased by 30.27%, and the results match well with the finite element results, which verifies the correctness of the optimization results of the electromagnetic force and the reasonableness of the optimization method.

Electromagnetic analysis and detent force minimization of a linear vernier motor

This paper proposes a new dual-sided linear permanent magnet vernier motor (LPMVM). The advantages of high thrust density, low thrust ripple, positive force elimination and structural stability are introduced in detail. The double-sided structure and toroidal winding proved the novelty of the machine tool, which is suitable for high definition digital control machine tools. Firstly, the basic structure and working principle of the engine are introduced. Through theoretical analysis, the expressions of electromagnetic thrust and detent force are derived. Thirdly, basic characteristics of permanent magnetic magnet flux coupling, backless electromotive force, detent force and electromagnetic drive are analyzed by using a a simplified three-phase model with symmetric boundary in 3-D finite element analysis. Finally, the thrust density and the detent force of the designed motor are calculated and analyzed. The results show that the designed motor is superior to the linear permanent magnet synchronous motor.

Inductance Gradient in Electromagnetic Launcher Under Channel Cooling Condition

Avoiding the ablation on the rail surface and obtaining large enough electromagnetic thrust to push the armature forward to high speed are two core contents of the electromagnetic launch technology. Reducing the ablation on the rail surface as much as possible can effectively extend the service life of the electromagnetic launcher (EML). The greater the electromagnetic thrust, the greater the initial velocity of the armature launched by the EML. The ablation on the rail is closely related to the temperature of the rail surface, and the electromagnetic thrust is proportional to the inductance gradient in the rails. The water flowing through cooling channels in rails can take away most of the heat generated by megaampere current flowing through the rails and armature in a few milliseconds. In this way, serious ablation on the rail can be avoided. Although the cooling channels are very helpful to reduce the ablation on rails, if the location distribution of the cooling channels in rails is not appropriate, the inductance gradient in the rails will be affected. This will affect the electromagnetic thrust in the EML. Therefore, the expressions of the inductance gradient in the rails with or without cooling channels are deduced and verified by the FEA in this article. The influence of the position distribution of the cooling channel on the inductance gradient in rails is analyzed. The results show that, with the increase of frequency, the influence of cooling channels on the inductance gradient in the rails diminishes gradually; if the distance between the cooling channels and the surface of the rails is greater than a certain value, the inductance gradient is no longer influenced by the cooling channels. At last, the relationship among <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} ^{\prime} $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\mathbf {1}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L} _{\mathbf {2}}$ </tex-math></inline-formula> are fit in this article. It can be used to find the rail parameters that meet both thermal management and electromagnetic driving force requirements.

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.

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.

Optimization and Experimentation of Fault-Tolerant Field Excited Linear Flux Switching Machine With Concentrated and Toroidal Windings for Rail Transportation System

In this article two double-sided Field Excited Linear Flux Switching Machines (FELFSM) are analyzed. Both machines share the same robust and compact stator structure with a modular mover design having different winding configurations namely concentrated and toroidal. The proposed machines have a low-cost owing to the lack of rare earth materials, a high fault-tolerant capability due to the modular construction of the mover, and flux controllability due to field current variation. The initial designs are optimized through a genetic algorithm using JMAG software ver. 20.1. to maximize the thrust force and minimize thrust force ripples ratio. After optimization, the average thrust force in Machine I and Machine II is increased by 31.96% and 32.31%, respectively. Additionally, a mathematical model is developed to compute electromagnetic thrust force and fault-tolerant capability. The electromagnetic performance of both machines are compared through 2D FEA. Both analytical and FEA-based designs are verified through experimental validation on the developed prototype. Finally, a coupled electromagnetic-thermal study is carried out, with the temperature of the prototype being visualized experimentally using a Fluke VT04 IR thermometer.

Novel Dynamic Microactuation Method for Tracking-Error Reduction of Permanent Magnet Linear Synchronous Motors

A permanent magnet linear synchronous motor (PMLSM) is susceptible to system uncertainties and external disturbances, resulting in a tracking error that is difficult to eliminate. To effectively reduce the tracking error of a PMLSM, this article presents a novel dynamic microactuation (DMA) method through a microactuation unit (MAU)-assisted dual-stage system. In this article, we reduce the tracking error dynamically through MAU-based actuation and use the PMLSM mover as the working end of the dual-stage system. The proposed DMA method finalizes the actuation mechanism of the MAU. Therefore, the method can dynamically actuate the MAU to act on the PMLSM mover with the appropriate actuation amount, and thus, reduce the tracking error of the motion system. Moreover, to avoid the coupling effect of MAU-based actuation on the PMLSM controller, the DMA method modifies the feedback error of the PMLSM controller by adding the actuation amount to the position error such that it remains unchanged. Thus, the stability of the electromagnetic thrust of the PMLSM can be maintained for its output. After finalizing the actuation mechanism and modifying the feedback error, the tracking error of the PMLSM can be reduced dynamically and the coupling effect of the MAU-based actuation on the PMLSM controller can be avoided. The performance of the proposed DMA method is analyzed theoretically and validated experimentally. The results show that the proposed method can effectively reduce the tracking error of a PMLSM system.

Electromagnetic Characteristics Analysis of Quadrupole Compound Orbital Electromagnetic Launcher with Different Configurations

During the operation of the Quadrupole Compound Orbital electromagnetic launcher, the current is easy to gather in the armature and the rail contact surface. Serious turn and arc ablation can occur, causing damage to the rail and the armature and affecting the life of the launcher. To better solve the thermal ablation problem of the armature and the rail, three different configurations of the rail and the armature are established, and the current density, magnetic field distribution and electromagnetic force of the rail and the armature are compared and analyzed using the finite element method, and the effect of concave and convex values of the armature rail on current distribution and electromagnetic force is discussed. The results show that the planar armature can effectively reduce the maximum current density and mitigate thermal damage. The concave elliptical rail produces the largest electromagnetic thrust and the smallest radial electromagnetic force, and the armature is more stable during firing. The maximum current density and magnetic field strength are negatively correlated with the concave and convex values; the electromagnetic thrust applied to the concave elliptical armature is negatively correlated with the concave value, while the electromagnetic force applied to the convex elliptical armature is positively correlated with the convex value.

Electromagnetic Design and Analysis of Permanent Magnet Linear Synchronous Motor

Since permanent magnet linear synchronous motors are widely used in fatigue testing, in this paper, the thrust of a permanent magnet linear synchronous motor (PMLSM) is amplified more than 10 times by the method of resonance. Firstly, the air gap magnetic field is analyzed by the equivalent magnetization current method (EMC), the electromagnetic thrust is calculated, and the expression is given by the Maxwell tensor method. The vibration analysis of the whole machine is used to obtain the conditions under which the motor resonates. The dynamic and static characteristics of the motor are analyzed through finite element simulation, the results of the motor design are judged to be reasonable, and the theoretical calculation results are compared with the simulation results to verify the accuracy of the theoretical calculation. The accuracy of the simulation results is verified by static force experiments. Finally, the rated thrust of the motor was enlarged more than 10 times by resonance experiments.

Analysis of Electromagnetic Characteristics of a Novel Toroidal Acceleration Linear Motor

A high thrust density linear motor, which adopts a novel toroidal structure, applying to load acceleration in confined space is proposed. The basic structure of the toroidal acceleration permanent magnet synchronous linear motor (TA-PMLSM) is depicted, both with its parameters listed. The main characteristics such as air gap magnetic density and electromagnetic thrust are discussed by establishing the electromagnetic field equation in the cylindrical coordinate system. And simulation comparison between the Halbach permanent magnet array and the classical radial one is also made to get a higher density of the magnetic and electromagnetic thrust. Compared with the conventional radial permanent magnet array, results show that the amplitude of back EMF of ring motor under the action of Halbach permanent magnet array has a better sinusoidal, the magnetic density of the air gap increases by 1.3 times, the thrust density increases by 1.42 times, and the main harmonic content of the two referred physical quantity decreases significantly.

Analysis of electromagnetic characteristics of the proposed composite four-rail electromagnetic launcher

Abstract In the existing composite four-rail electromagnetic launcher (CFREL), the armature and rail contact surface produces significant heat and bears considerable wear, thereby reducing the potential amount of electromagnetic thrust to be generated. To eliminate the damage caused by the thermal effect of the rail contact surface and to meet the electromagnetic thrust demand of the load, a CFREL is proposed. The proposed CFREL model is constructed, and the launcher’s electromagnetic characteristics are simulated and compared using the finite element method. The current density, distribution of magnetic flux density, and electromagnetic thrust characteristics are analysed. The results showed that the proposed CFREL reduced the maximum current density of the contact surface and effectively eliminated the current concentration of the armature and rail contact surfaces. Effective magnetic field shielding is realised with a larger range, which can better meet the requirements of the intelligent load’s magnetic field environment and provide stronger electromagnetic thrust for the load, hence solving the problem of insufficient thrust.