Optimal Pole Research Articles

Switched Reluctance Motor Design and Optimization

In the field of electric vehicle engineering, Switched Reluctance Motors (SRMs) are progressively drawing the attention of developers for their streamlined structural design, superior torque output, economical cost-benefit, and excellent energy efficiency ratios. This paper takes a four-phase 8/6-pole switched reluctance motor as an example, with a rated power of 7.5Kw and a rated speed of 1500r/min. According to the basic design requirements of the SRM, the SRM parameter design flow is designed, and a Matlab calculation program is written for the preliminary calculation of the SRM parameters, and the detailed design of its motor structural parameters is carried out. After that, the stator and rotor pole arc coefficients of the SRM are parametrically analyzed using Maxwell2D tool according to the design experience, and the optimal stator and rotor pole arc coefficients are selected. The simulation results show that the design optimization scheme can effectively reduce the SRM torque pulsation.

Declining Cogging Torque Technique of an Integral Slot Number for Permanent Magnet Machines

The existence of cogging torque in electric equipment has been considered undesirable. This kind of friction in the air-gap impacts the alignment of flux and the stator slots, resulting in the observed outcome. Consequently, the imposition of restrictions on the rotation of the rotor is employed to generate electrical energy. This research endeavor primarily aims to mitigate the cogging torque of electrical machinery. The current utilization involves employing a total of 3 permanent magnet synchronous machines, often known as inset PMMs, which possess a slot count of 24 and a pole count of 8. The employed technique involves the integration of an optimal pole arc method in conjunction with the implementation of slots cut into the magnet's edge. The machine model under investigation has two fundamental variants, namely Models 1 and 2. These models are equipped with 1one-step slotted (OSS) and 2two-step slotted (TSS) edges on each magnet, in addition to pole arc optimization. The simulation was conducted using the Finite Element Method Magnetics (FEMM) 4.2 software together with LUA scripts, with a focus on rotor rotation ranges of 1 degree. Model 2 exhibited a decrease in cogging torque of 0.01 Nm, whereas Model 1 demonstrated a reduction of 0.015 Nm, and the basic model had a decrease of 0.02 Nm. When implementing a dual-layered cutting edge on a magnet and attempting to optimize its pole arc, it is imperative to consider that the cogging torque's peak magnitude becomes substantially diminished or entirely eliminated.

Multi-parameter optimization of ferrofluid seal pole teeth based on magnetic-flow coupling and taboo genetic algorithm

Ferrofluid seals are a high-performance seal technology. Rational pole tooth structure and size can enhance the performance of ferrofluid seals. However, most current methods for optimizing pole tooth structure and size ignore the influence of the flow field. Therefore, this paper presents a pole tooth optimization method based on magnetic-flow coupling and considers the shaft rotational speeds. Combining this method with the taboo genetic algorithm establishes the mathematical model and simulation model of magnetic pole tooth size optimization. The optimal pole tooth size at different rotational speeds is obtained through optimization. Additionally, the effects of rotational speed and pole tooth parameters on pressure capacity are studied. The results show that both the rotational speeds and the parameters of the pole teeth significantly affect pressure capacity. The rotational speeds also influence the parameters of the pole teeth.

Research on cogging torque reduction method for permanent magnet synchronous motor accounting for the magnetic pole edge effect

AbstractDue to the existence of the magnetic pole edge effect, the actual cogging torque of the existing segmented step skew motor does not reach the theoretical minimum. Thus, a method for suppressing cogging torque of permanent magnet synchronous motor considering the magnetic pole edge effect is proposed. The magnetic pole edge effect is creatively converted into the amplitude and phase offset of the cogging torque generated by each pole segment. On this basis, an optimization problem is constructed in which the fundamental component of cogging torque is zero and the total harmonics is minimum. The optimal magnetic pole length and skew angle parameters of each segment are obtained by solving the optimization problem quantitatively. The results can provide theoretical guidance for motor design, which can minimize the cogging torque of step skew structures. The effectiveness of the proposed method in weakening the cogging torque of the step skew motor is demonstrated by theoretical calculation, 3D finite element analysis, and experimental results.

Design Optimization of Combined Function Accelerator Magnet Using Truncated Singular Value Decomposition

The Japan Proton Accelerator Research Complex (J-PARC) is a world-class accelerator facility for particle and nuclear physics experiments such as the rare kaon decays experiment (KOTO), the T2K long-baseline neutrino experiment, and future projects such as COMET. A new stretcher ring (SR) comprising a combined function superconducting magnet is proposed to run all of the facilities at the same time, which can improve beam efficiency and increase operating time. In order to achieve the field quality requirements on the magnet aperture, it is critical to identify an optimum pole shape. Dipole, quadrupole, and sextupole fields are required for the combined function magnet. To find the best design parameters for this analysis, we employed singular value decomposition. The singular value decomposition (SVD) technique resulted in a solution to the desired parameters and a quick process to obtain a 2D pole profile.

Modelling the influence of beach building pole heights on aeolian morphology and downwind sediment transport

Buildings on beaches either sit directly on the sediment surface or are placed on poles. These structures alter near-bed airflow around them. To quantify the influence of pole height on airflow, resulting bed morphology around these buildings and sediment fluxes passing these buildings towards the dunes, three-dimensional simulations were performed. To compute airflow, we used the open-source computational fluid dynamics software OpenFOAM. For sand transport and bed level changes, we used the Exner equation combined with Bagnold's sediment transport flux formulation, and a newly-developed model that couples the airflow model with the sediment transport model AeoLiS. In the simulations, we modelled a row of ten full-scale beach buildings on a flat/smooth sandy bed, with a constant gap size between neighbouring buildings, varying the pole heights between simulations. Our findings showed that elevated buildings affect the wind speed in a larger region, both upwind and downwind, compared to buildings without poles. The model simulations showed that airflow accelerated both underneath the elevated buildings and through the gaps between the buildings. Moreover, besides flow acceleration underneath the buildings, the elevated buildings induced slightly higher flow acceleration through the gaps between buildings. Depending on pole height to building width ratio, elevated buildings could both decrease and increase the downwind sediment flux compared to an undisturbed situation. For ratios between 0 and 0.5, downwind fluxes were reduced in a zone between 5 and 40 m behind the buildings, while for ratios above 1.3, downwind fluxes were observed to increase in a zone up to 20 m behind the buildings. Also, this study emphasizes the importance of selecting an optimal pole height to maximize the benefits of beach buildings in terms of passing on sediment transport towards the dunes.

Estimation of Kautz Poles in Wiener-Volterra Models Using Levenberg-Marquardt Algorithm

This work approaches the problem of estimating the Kautz optimal poles in kernel expansion in Wiener-Volterra models. The analytical solution for the suboptimal case is already established in the literature. However, the solution for the two parameters that compose the poles is still open. In this paper, an optimization strategy using the Levenberg-Marquardt is presented. This algorithm is used to find kernel expansion parameters, with the same base for all dimensions. The construction of bases using digital filter is considered. To validate the implemented algorithm, data collected from the excitation of an electrically coupled drive system was used to analyze the impact of the search space thresholds and the behavior of Levenberg-Marquardt’s parameters. It was also analyzed the impact on the model accuracy, as the number of functions in the base is increased. As a result, the models determined have achieved better results than the works found in the literature.

Analysis of linear permanent magnet switched reluctance motors with modular and segmental movers

AbstractHere, the authors propose two new Permanent Magnet (PM) embedded linear switched reluctance motors; one is a modular linear hybrid reluctance motor (MLHRM), and the other one is a segmental linear hybrid reluctance motor (SLHRM). Both structures employ PMs between the side teeth of the modules/segments. The main contribution of the PMs is to increase the air‐gap flux density, which results in an enhanced thrust, and decrease the magnetic saturation in iron parts. The magnetic equivalent circuit model is used to demonstrate the positive effect of inserting PMs in the MLHRM and SLHRM compared to their PMless counterparts. The optimal pole number and design procedure are illustrated. The simulation results are obtained in terms of static thrust, flux linkage, flux density distributions, and steady‐state current and thrust. The results show that the proposed MLHRM and SLHRM offer a higher thrust and lower current compared to their PMless form. Also, the PMs decrease the root mean square (RMS) current under the steady‐state performance of the motors, in which a higher thrust is produced with a lower RMS current. Finally, the MLHRM and SLHRM are fabricated and the test results are obtained and compared with the simulations, which illustrate a satisfactory agreement.

Research on Torque Ripple Optimization of Permanent Magnet Synchronous Motor for Electric Vehicle Based on Modular Poles

AbstractAbstract in order to study the torque ripple of permanent magnet synchronous motor for electric vehicle, the method of modular poles instead of single pole is adopted to reduce the torque ripple. The modular poles consist of three kinds of permanent magnets with different remanence and are arranged in a sinusoidal distribution. The pole arc length and position of each magnetic pole are calculated according to the cutting area of sinusoidal air gap flux density wave. By changing the cutting area of sinusoidal air gap flux density wave, the optimal pole arc coefficient of each permanent magnet was determined, and the magnet pole combination with the smallest torque ripple value is obtained. The results show that the sine degree of back electromotive force is improved obviously, the cogging torque is decreased greatly, and the motor with modular poles has obvious effect on torque ripple suppression. The torque of the motor with different kinds of magnetic pole combination is more stable than that of the motor with the same kind of magnetic pole combination. In this paper, the method of using modular poles instead of single pole to reduce torque ripple is of positive significance, which provides a reference for the subsequent performance optimization of electric vehicle motor. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Disturbance Observer Based on Fixed Time Sliding Mode Control and Optimal State Observer for Three-Phase Three-Level T-Type Inverters

This paper presents the advanced control method together with the disturbance rejection method with the aims to obtain the low of total harmonic distortion (THD). The expectation of the paper is that the output voltage is satisfied the requirements of the EN 62040 with the THD is less than 5%. Therefore, this paper proposes a new disturbance observer (DOB) without the requirement of the information of the first derivative disturbance for the three phase three level (TPTL) T-type inverter system. The proposed DOB is based on the information of the measurable states, which are used such an inversed model of T-type inverter to find the information of real disturbance. First, the DOB was designed based on the given measured and estimated states. However, to design the DOB, the state observer is required. Therefore, second, the state observer (SOB) was designed based on linear matrix inequality (LMI) to identify the optimal poles of the state-tracking error function. Third, the estimated states were used to construct the fixed time (FT) sliding mode control (SMC) to control the T-type inverter system. Fourth, the Lyapunov condition was used to verify the correction of the proposed method. The performance of the proposed control strategy is validated by simulations and experiments during steady-state, transients caused by load change, and unbalanced grid conditions. The estimated states precisely tracked the measured states. The output signals precisely converged to the predefined trajectories in a predefined time and the tracking errors are small. The obtained results showed that the proposed control method provided excellent steady-state and good performances with low THD in the line currents, zero steady-state error in the output voltage, and a very fast dynamic response.

Optimal Pole Ratio of Spoke-type Permanent Magnet Vernier Machines for Direct-drive Applications

Due to magnetic gearing effects, spoke-type permanent magnet vernier machines (ST-PMVMs) have the merit of high torque density, where an extra torque amplification coefficient, i.e., pole ratio (the pole-pair ratio of PMs to armature windings) is introduced. However, different from surface-mounted PMVM, the variation of torque against pole ratio in ST-PMVMs is non-linear, which is increased at first and then decreased. This article is devoted to identify the optimal pole ratio of ST-PMVMs by equivalent magnetic circuit model. It is found that except the P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> air-gap magnetomotive force (MMF) harmonic having the same pole-pair of PM, the Pa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> air-gap MMF harmonic having the same pole-pair of armature winding is also induced due to the modulation of doubly salient air-gap structure. The P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> MMF harmonic produces positive torque, while Pa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> MMF harmonic produces negative torque. With the increase of pole ratio, the proportion of Pa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> MMF harmonic as well as negative torque is increased, which reduces the advantages of high pole ratio coefficient. Further, the influence of dimension parameters on the performance of ST-PMVMs under different pole ratio are investigated. Results show that ST-PMVMs with pole ratio 2.6 have high torque density, low cogging torque and high power factor simultaneously. Finally, a prototype is manufactured to validate the analysis.

Research on the Control Method of Force Servo System of Liquid Hydrostatic Guide Oil Film Thickness Test Bench for Machine Tools

The test bench was designed to solve the problem of measuring the oil film thickness of the liquid hydrostatic guideway of machine tools. And based on the fast overshoot of the classical PID control, introducing the self-antidisturbance control algorithm, this study established a mathematical model of the test bench electro-hydraulic servo control system. At the same time, this paper also designed a specific structure of the self-turbulence controller, which adopts optimal quadratic control, pole configuration, PID control, and self-turbulence control to study the control methods of the test bench electro-hydraulic servo system, respectively, and uses the SIMULINK module to establish the system simulation model of the above-mentioned four control methods of the test bench. Simulation results of the test bench control system show that the response speed of the self-turbulence control is 0.4 seconds, 0.2 seconds, and 4.4 seconds faster than PID control, pole configuration, and optimal quadratic control, respectively, and the overshoot is significantly reduced. Finally, the test bench was built to complete the experiments, and the experimental results showed that the followability of the loading force and thickness detection accuracy of the test bench were better after adding the self-turbulence control algorithm and the stability of the oil film thickness was significantly improved by the test bench electro-hydraulic servo control system.

Intelligent Optimization of Switched Reluctance Motor Using Genetic Aggregation Response Surface and Multi-Objective Genetic Algorithm for Improved Performance

In this paper, a thorough framework for multiobjective design optimization of switched reluctance motor (SRM) is proposed. Selection of stator and rotor pole embrace coefficients is an essential step in the SRM design process since it influences torque output and torque ripple in SRM. The problem of determining optimal pole embrace is formulated as a multi-objective optimization problem with the objective of optimizing average torque, efficiency and torque ripple, and response surface models were obtained based on the genetic aggregation method. The results obtained by genetic aggregation response surface (GARS) and the non-dominated genetic algorithm (NSGA-II) were validated with the finite element method (FEM) model of the initial SRM. The optimized model displayed better efficiency profile over a wide speed range. The initial and optimized models recorded maximum efficiencies of 85% and 94.05%, respectively, at 2000 rpm. The efficiency values of 93.97–94.05% were achieved for the three pareto optimal candidates. The findings indicate the viability of the suggested strategy and support the use of GARS and NSGA-II as useful methods for addressing SRM key challenges.

Inversed Model-Based Disturbance Observer Base on Adaptive Fast Convergent Sliding Mode Control and Fixed-Time State Observer for Slotless Self-Bearing Motor

The slotless self-bearing motor (SSBM) is a motor with its self-bearing function. The mechanical structure of the motor is six symmetrical hexagonal shapes. The main control problem for this motor is disturbance and uncertainty rejection. Therefore, this paper proposes a new disturbance observer (DOB) based on an optimal fixed-time state observer (OFTSOB) and adaptive sliding mode control (SMC) for the motor. Firstly, the optimal state observer was used to construct to obtain the information of the states of the bearing-less motor system. Second, a new disturbance observer base on the fast speed reaching law is proposed for estimating the unknown dynamics and unpredicted uncertainty of the motor system. Third, the adaptive fast-reaching law-sliding mode control is designed to control the positions and rotational speed. Fourth, the proposed control system is proved via the Lyapunov theorem. Finally, the corrections of proposed method once again tested by using MATLAB simulation. The obtained results figured out that the proposed method is good at rejection disturbance and uncertainty and precision in control the movement and rotation. The novelties of the proposed method are that the gains of fixed-time observer were met by the support of optimal pole placement method, the disturbances were mostly rejected by a new reaching law of unknown input observer.

Design and analysis of 12 MW offshore wind turbine

Permanent magnet synchronous motors are widely used in various fields for the advantages of high power density, high efficiency and high reliability. This paper analyzes the cogging torque of generators with different slot and pole coordination, and selects the optimal pole–slot ratio. Then, this paper analyzes the structural differences between the outer rotor and the inner rotor of permanent magnet synchronous motor, and selects the structural form of the outer rotor for analysis. Based on the electromagnetic design parameters of the motor, a two-dimensional finite element model is established in Maxwell to simulate and analyze the performance at no-load, rated load and short-circuit. The internal magnetic field, the distortion rate of voltage waveform, torque and short circuit current of the motor are studied, and the demagnetization of the permanent magnet under the worst operating condition is investigated. The simulation results show that the design scheme meets the design objectives.

Effect of Pole Shaping on Torque Characteristics of Consequent Pole PM Machines

Consequent pole (CP) permanent magnet (PM) machines offer scope for reducing the quantity of PM material and hence cost compared to more conventional PM machine topologies of the same rating. In this type of machine, the rotor pole arc is usually optimized to realize the largest output torque with pole shaping methods used to reduce torque ripple. However, such approaches tend to be limited by constraints imposed on the pole shapes. It is a common practice to adopt similar PM and iron pole shapes, an approach that does not fully account for the different characteristics of PM and iron poles in CPPM machines, often leading to large even order harmonics in the airgap flux density. This article proposes a shaping method with a variable rotor profile and pole arc span being established by means of optimization by Genetic Algorithm. It is demonstrated that for a fixed quantity of PM material, different PM and iron pole shapes in combination with optimal PM and iron pole arc spans are essential for ensuring both maximum output torque and lower torque ripple when the due account is taken of flux leakage. It also demonstrates that since the flux density in the region under a PM pole is governed by the magnetic potential produced by magnets while it is governed by magnetic reluctance under iron pole, different PM pole and iron pole shapes are necessary to reduce the even-order harmonics in a CPPM machine and consequently to reduce torque ripple. The performances of optimized and more conventional CP machines are compared by finite-element method on 12-slot/8-pole prototype motors.

Globally optimal shape and spin pole determination with light-curve inversion

ABSTRACT Light-curve inversion is an established technique in determining the shape and spin states of an asteroid. However, the front part of the processing pipeline, which recovers the spin pole and area of each facet, is a non-convex optimization problem. Hence, any local iterative optimization scheme can only promise a locally optimal solution. Apart from the obvious downsides of getting a non-optimal solution and the need for an initialization scheme, another major implication is that it creates an ambiguous scenario – which is to be blamed for the remaining residual? The inaccuracy of the modelling, the integrity of the data, or the non-global algorithm? We address the last uncertainty in this paper by embedding the spin pole and area vector determination module in a deterministic global optimization framework. To the best of our knowledge, this is the first attempt to solve these parameters globally. Specifically, given calibrated light-curve data, a scattering model for the object, and spin period, our method outputs the globally optimal spin pole and area vector solutions. One theoretical contribution of this paper is the introduction of a lower bound error function that is derived based on (1) the geometric relationship between the incident and scattered light on a surface and (2) the uncertainty of the gap between the observed and estimated brightness at a particular epoch in a light curve. We validated our method’s ability in achieving global minimum with both simulated and real light-curve data. We also tested our method on the real light curves of four asteroids.

Evaluation index and performance structure optimization of magnetic field uniformity of complex multiphase flow electromagnetic flowmeter

The uniformity of the excitation magnetic field is an important factor affecting the measurement accuracy of the electromagnetic flowmeter and its adaptability to different flow states of the complex multiphase flow. The main purpose of this paper is to improve the measurement accuracy of electromagnetic flowmeter by improving the uniformity of magnetic field excitation of electromagnetic flowmeter sensor. Firstly, an evaluation index system based on area weight magnetic field deviation degree is established, and the concept of flow state adaptability is put forward. According to this evaluation system, the excitation structure of the conventional electromagnetic flowmeter sensor is improved and optimized, and an excitation model with high uniformity is designed. Meanwhile, the ANSYS software is used for numerical simulation, and normalized standard deviation is used to compare between the new and the traditional electromagnetic flowmeter models. Finally, according to the requirements of the index function, the magnetic pole detection angle of the improved excitation model is simulated and analyzed, and the optimal magnetic pole detection angle is determined to be 45°. On this basis, a new electromagnetic flowmeter is designed for complex multiphase flow at oil wellhead. The field test proves that the measurement error of this flowmeter can reach less than 5%. Compared with the traditional electromagnetic flowmeter, the measurement accuracy has been greatly improved.

An Inductor Current Sensorless Control Strategy Based on Modified VSG Method for Single-Phase Microgrid Application With Seamless Transfer Capability

This paper proposes an inductor current sensorless control strategy based on modified virtual synchronous generator (VSG) method for single-phase inverter-interfaced microgrid application. Firstly, the outer power loop with Q-U integral term is presented for output reactive power enhancement, and an inner voltage regulation loop based on luenberger state observer is proposed to reduce the inductor current sensor. Meanwhile, in order to improve the response speed of the observer, the luenberger observer is designed based on the optimal pole assignment method. Secondly, a seamless switching strategy based on the modified VSG method is proposed, which can realize the seamless transition between the island mode and grid-connected mode. Finally, a single-phase 3kW VSG prototype is built, and the effectiveness and correctness of the proposed control strategy is verified by the simulation and experimental results.

Electromagnetic Torque Improvement of Doubly Salient Permanent Magnet Machine Using Pole Ratio Adjustment Technique

This paper introduces the pole ratio adjustment technique to improve the torque characteristics of the doubly salient permanent magnetic machine (DSPM). The electrical characteristics of the machine, namely the magnetic field distribution, flux linkage, back-electromotive force (EMF), and cogging torque, were obtained under open-circuit conditions. The electromagnetic torque and ripple torque were examined under the loaded condition. The simulations, based on the 2D-finite element method, show that the optimal pole ratio for the DSPM structure is with 18 stator teeth and 15 rotor poles. This optimal structure achieves a larger phase back-EMF than the conventional structure, as well as had a better magnetic flux path with a reasonable cogging torque. The on-load test also confirmes that the proposed optimal structure can produce a significantly higher electromagnetic torque than the conventional machine while maintaining a satisfactory torque ripple. Furthermore, an experimental prototype of the DSPM structure having 18/15 stator/rotor poles was fabricated and tested to verify the simulations. The experimental results were in good agreement with the simulations. The design technique and the fabricated prototype demonstrate the DSPM utilization for low-speed/high torque applications.