High Torque Ripple Research Articles

Intelligent Bearing Fault Diagnosis of Switched Reluctance Motor Using Hilbert-Huang Transformation and Region-Based Convolutional Neural Network

With the widespread trend of transportation electrification, much research has been focused on switched reluctance motor (SRM) because of its robustness and wide speed range. Though the SRM has a promising electric fault tolerance, the rotor support bearings subjected to mechanical friction are vulnerable to brinelling and corrosion. Furthermore, traditional bearing fault diagnosis approaches adopted for conventional motors are not well suited for SRM bearings because of its high torque ripples and noisy operation. Aiming at offering an efficient solution, this work proposes a novel technique by fusing the Hilbert-Huang transformation of vibration signal with region based Convolutional Neural Network. The core idea of the method is to decompose the vibration signal and employ a new kind of offline region generation algorithm for the detection of fault characteristics. The effectiveness of the designed model is tested and evaluated by a series of experiments. The results show that the proposed method achieved a remarkable diagnosis accuracy of 99.6%. Conclusively, a systematic comparison of the proposed model with the other state of the art models is carried out.

EFFECTS OF ASYMMETRICAL STATOR STRUCTURE ON BLDC MOTOR PERFORMANCE FOR HOUSEHOLD APPLIANCES

Brushless direct current motors (BLDCM) have been frequently preferred in the industry, especially in home appliances, due to their advantages such as long life, high efficiency, low maintenance costs and ease of control. In addition to these advantages, the main disadvantages of these motors are known to be high torque ripple and vibration levels. In this study, alternative asymmetric designs are realized in the stator tooth structure of the BLDCM designed for home appliances, and comparative analyses of the effects of the non-uniform air gap caused by the asymmetric tooth structure on the motor performance are presented. Two different asymmetric structures, namely the model with clockwise asymmetric design (CW) and the model with counterclockwise asymmetric design (CCW) in the stator tooth structure, are determined in the stator design. With these alternative designs, improvements are made in terms of torque ripple and cogging torque when compared with the reference motor; notably, the CCW-2 model achieves the lowest ripple at 19.4% compared to 23.1% for the reference motor, and a 42% reduction in cogging torque. The design of the motor models is made in ANSYS EDT program as two dimensional (2D) and analyzed with the Finite Element Method (FEM). In the analysis results, air gap flux density, torque, torque ripple and cogging torque are examined, and the flux density and torque spectrum obtained by Fast Fourier Transform (FFT) are presented comparatively

Improved Active Vector Optimization Strategy‐based Model Predictive Torque Control for Matrix Converter‐Fed PMSM With Reduced Torque and Flux Ripples

ABSTRACTThe Matrix Converter‐fed Finite Control Set‐Model Predictive Torque Control (FCS‐MPTC) technique has superior potentiality in the control of electrical drives due to its availability of increased number of voltage vectors with compact topology. On the other side, the FCS‐MPTC technique suffers a major drawback of high computational complexity and processing time. This major drawback has degraded the attention of the FCS‐MPTC technique in high‐power industrial applications because it needs expensive and high‐rating processors for the functioning of the control algorithm. In this regard, this paper proposes an efficient active vector optimization concept by formulating a switching table for the optimal voltage vector selection. This approach reduces the available 18 active vectors to three, thereby decreasing the execution time of the cost function (CF). In addition, to mitigate the high torque and flux ripple problems associated with the existing FCS‐MPTC method, a modified switching table is proposed. The effectiveness of the proposed approach is evaluated by conducting various test loadings using the MATLAB Simulink, and the results are further validated in real time using the OPAL‐RT laboratory setup.

Precise Excitation of a Switched Reluctance Machine under Regenerative Mode in High-Speed Operation

The implementation of electric machines in electric and hybrid electric vehicles offers some advantages, including the ability to operate in regenerative mode. Switched reluctance (SR) machines have been alternative solutions due to their characteristics. Operating an SR machine in propulsion mode requires high torque and minimal torque ripple, while producing optimal output power in regenerative mode is required. In high-speed operation, when the back electromotive force is greater than the DC link voltage, single pulse-based methods are often used. Torque ripple problems can be neglected due to rotor inertia. In this paper, a single pulse-based control for SR machines in high-speed operation under regenerative and discontinuous conduction modes is analyzed. Excitation to magnetize the rotor and generation process to produce output power are compared to determine the effectiveness of energy saving during regenerative mode. By using a simple control strategy, precise excitation angles can be obtained to turn the machine on and off. Experimental work has been done to support the analysis. They show that by using proper excitation angles, the optimal output power can be generated.

Influence of Winding Configurations and Stator/Rotor Pole Combinations on Field Back-EMF Ripple in Switched Flux Hybrid Excited Machines

Similar to armature back electromotive force (armature back-EMF), the back-EMF also exists in the field winding of hybrid excited machines. However, the existence of field back electromotive force (field back-EMF) is harmful to the safe and stable operation of machine systems, e.g., higher losses, lower efficiency, higher torque ripple, and reduced control performance. This paper systematically investigates the influence of armature/field winding configurations together with stator/rotor pole combinations on the field back-EMF ripple in hybrid excited machines with switched-flux stators. The two-dimensional (2D) time-stepping finite element modeling and prototyping experiments are used for the research. The investigated field and armature coil pitches equal to 1, i.e., non-overlapped windings. The influential factors that are investigated in this paper mainly include the number of layers of field/armature windings, the number of field/armature coils, and the stator/rotor pole combinations. The results show that the field back-EMF’s harmonic order and peak-to-peak value are closely associated with field/armature winding configurations and stator/rotor pole combinations under various conditions. Finally, for validation of the results predicted by the finite element method, a prototype machine is built and tested. Overall, non-overlapped double-layer armature and field windings are recommended for the hybrid excited switched flux machines with various stator/rotor pole combinations to realize relatively lower field back-EMF under different conditions.

Further Application Of Automatic Control Based On Servo Motor In Smart Grid

The paper summarize the advantages and applications of servo motor. As a kind of equipment that can replace manual long-distance inspection, the intelligent inspection device for overhead transmission lines can significantly improve inspection efficiency and reduce labor intensity. The servo motor with high power density and low torque ripple can guarantee the high precision and stable operation of the intelligent inspection device in line inspection, which provides a certain practical intelligent application significance for transmission line inspection.

Dynamic overmodulation strategy based on torque and flux optimal tracking for DTC‐SVM of surface‐mounted PMSM drives

AbstractDirect torque control with space vector modulation has been increasingly attracting emphasis for permanent‐magnet synchronous machine control, benefiting from a high dynamic response and low torque ripple. However, the rapid tracking performance of torque and stator flux linkage is gradually deteriorating as the machine enters the overmodulation region because of the output‐voltage limitation of the inverter. Therefore, to enhance the system tracking performance in the overmodulation region, an innovative overmodulation method based on torque and flux optimal tracking is proposed. In contrast to the conventional overmodulation method where only one of the torque and stator flux linkage tracking is considered, the proposed strategy first constructs the weightless cost function to achieve a trade‐off control between the torque and stator flux linkage. Then, by using an equivalent geometric path to intuitively express the weightless cost function, the minimum cost function can be easily solved and the optimal output voltage vector can be determined correspondingly, to achieve the fast‐tracking of both the torque and stator flux linkage. Additionally, the voltage utilization of different overmodulation schemes is also analysed. Finally, the experimental results demonstrate the efficiency and practicality of the proposed strategy.

An improved finite set model predictive control of SRM drive based on a voltage vectors strategy for low torque ripple

The robust rotor structure and fault-tolerance characteristics of the Switched Reluctance Motors (SRMs) are the best choice for next-generation Electric Vehicle (EV) applications. This machine has few restraints like high torque and flux ripples. However, the existing Model Predictive Control (MPC) using multiple control objectives and maximum sectors in the switching table results in high torque ripples due to the improper sector partition, Voltage Vectors (VVs) and weight factor (K1) selection. This paper proposes a Finite Set-Model Predictive Control (FS-MPC) for an analytical model of a non-linearity SRM machine to analyze the torque ripple performance. The proposed VVs are derived using sector partition based on the rotor position. The control is designed as a single cost function with the weighting factor contributing to smooth torque by selecting optimal control signals. Simulation studies and experiments with a four-phase 8/6 SRM drive verifies the enhanced FS-MPC for real-time implementation. The dynamic speed and ripple values of SRM Drives are measured using a mixed signal oscilloscope and the sensor probes. The laboratory outcomes calculate the analytical equations to validate the findings. The calculated value of torque ripple is 9 % through this FS-MPC. The study reveals that the proposed method is well suited for torque ripple reduction than flux ripples.

A High Torque Density Dual-Stator Flux-Reversal-Machine with Multiple Poles Halbach Excitation on Outer Stator

This paper proposes a high torque density dual-stator flux-reversal-machine with multiple poles Halbach excitation (MPHE-DSFRM), which uses two pole pairs’ numbers (PPNs) of PM excitation on one outer stator tooth, and one PPN of PM excitation on one inner stator tooth. The introduction of different PPNs of PM excitation on the outer and the inner stators can optimize magnetic circuit and airgap flux density. A Halbach array is formed by inserting three pieces of circumferentially magnetized PMs into four pieces of radially magnetized permanent magnets (PMs) on the outer stator, which aims to further enhance torque density, and reduce torque ripple. Based on the flux modulation effect, the analytical modeling of the proposed MPHE-DSFRM is established, together with the evolution process, and the working principle is presented. Then, the key design parameters of MPHE-DSFRM are optimized to achieve high torque density and low torque ripple for high torque quality. Three representative DSFRMs and a conventional FRM are designed and analyzed, and they share the same design key parameters, including PM usage, outer radius of the outer stator, and active airgap length. The electromagnetic performances, including airgap flux density, back electromotive force (back-EMF), and torque characteristics, are analyzed and compared by finite element analysis (FEA). The calculated results show that the proposed MPHE-DSFRM can provide high torque density and high PM utilization.

Experimental analysis of enhanced finite set model predictive control and direct torque control in SRM drives for torque ripple reduction

The magnet-less switched reluctance motor (SRM) speed-torque characteristics are ideally suited for traction motor drive characteristics and its advantage to minimize the overall cost of on-road EVs. The main drawbacks are torque and flux ripple, which have produced high in low-speed operation. However, the emerging direct torque control (DTC) operated magnitude flux and torque estimation with voltage vectors (VVs) gives high torque ripples due to the selection of effective switching states and sector partition accuracy. On the other hand, the existing model predictive control (MPC) with multiple objective and optimization weighting factors produces high torque ripples due to the system dynamics and constraints. Therefore, existing DTC and MPC can result in high torque ripples. This paper proposed a finite set (FS)-MPC with a single cost function objective without weighting factor: the predicted torque considered to evaluate VVs to minimize the ripples further. The selected optimal VV minimizes the SRM drive torque and flux ripples in steady and dynamic state behaviour. The classical DTC and proposed model were developed, and simulation results were verified using MATLAB/Simulink. The proposed model operated in SRM drives experimental results to prove the effective minimization of torque and flux ripples compared to the existing DTC.

CONTRÔLE DIRECT DU COUPLE AVEC MODULATION VECTORIELLE SPATIALE UTILISANT DES RÉGULATEURS À LOGIQUE FLUUSE DE TYPE 2 À INTERVALLE D'UNE MACHINE À INDUCTION À DOUBLE ÉTOILE ALIMENTÉE PAR DEUX ONDULEURS À POINT NEUTRE À TROIS NIVEAUX SERRÉS

This paper introduces a direct torque control (DTC) method with space vector modulation (SVM) using interval type-2 fuzzy logic regulators for a dual-star induction machine fed by two three-level neutral point clamped inverters. The conventional DTC drive utilizes a pair of hysteresis comparators, which can lead to issues such as high torque ripple and variable switching frequency. As a result, we introduce several alternative methods, including DTC-SVM. We replace the hysteresis comparators with two Proportional-Integral (PI) regulators to enhance DTC performance, which generates the direct and quadrature voltage components in the d-q frame. The intricacy of the control system can make adjusting the PI regulator parameters difficult. To address this challenge, we propose using an interval type-2 fuzzy logic regulator for PI parameter adjustment in this paper. Our simulation results demonstrate the robustness and efficiency of the IT2FLC regulator.

Torque Ripple Suppression in the 6/4 Variable Flux Reluctance Machine with Open Winding Configuration by Using Harmonic Injection

High torque ripple can be observed with a 6/4 variable flux reluctance machine (VFRM). In order to minimize the torque ripple in VFRMs, this paper presents a harmonic injection method for 6/4 VFRMs with an open-winding configuration. By analyzing the impact of harmonics on VFRMs, the method involves detecting the third harmonic using a first-order low-pass filter (FLPF). Subsequently, the extracted harmonics are controlled and shifted to counteract the voltage harmonics in both inverters without inducing phase imbalance or overvoltage. With the proposed method, the torque ripple can be significantly reduced by about 50% under load conditions. The effectiveness of the harmonic injection method is validated through a prototype VFRM.

Design and shape optimization of interior permanent magnet synchronous machine based on hybrid cores

By designing stator teeth using grain-oriented sheets (GO) and other parts still with non-grain-oriented sheets (NGO), the electromagnetic performance of the interior permanent magnet synchronous machine (GO-IPMSM) can be improved greatly. As the stator core of the designed GO-IPMSM is a hybrid core that is composed of two different silicon sheets, both the electromagnetic and mechanical performances are affected by the stator joint shape between GO and NGO sheets. Meanwhile, with the adoption of GO, the torque ripple of GO-IPMSM is increased though the average torque is increased as well. For reducing the torque ripple, optimizing the rotor barrier shape is an effective way. In this paper, the piecewise linear interpolation method is employed for establishing the stator joint shape between GO and NGO sheets, and the polynomial method is proposed to establish the rotor barrier shape. Through the analysis, it can be seen that the stator joint shape plays a strong role in affecting the mechanical performance of the GO-IPMSM, while the effect on the electromagnetic performance is weak. The genetic algorithm is used to optimize the rotor barrier shape for achieving high average torque and low torque ripple. Lastly, a quick and accurate efficiency map calculation method based on the Kriging model is proposed for GO-IPMSM with less finite element method (FEM) samples are required.

Fuzzy Super-Twisting Sliding Mode Controller for Switched Reluctance Wind Power Generator in Low-Voltage DC Microgrid Applications

There is limited research focused on achieving optimal torque control performance of Switched Reluctance Generators (SRGs). The majority of existing studies tend to favor voltage or power control strategies. However, a significant drawback of SRGs is their susceptibility to high torque ripple. In power generation systems, torque ripple implicates fluctuations in the generated power of the generator. Moreover, high torque ripple can lead to mechanical vibrations and noise in the powertrain, impacting the overall system performance. In this paper, a Torque Sharing Function (TSF) with Indirect Instantaneous Torque Control (IITC) for SRG applied to Wind Energy Conversion Systems (WECS) is proposed to minimize torque ripple. The proposed method adjusts the shared reference torque function between the phases based on instantaneous torque, rather than the existing TSF methods formulated with a mathematical expression. Additionally, this paper introduces an innovative speed control scheme for SRG drive using a Fuzzy Super-Twisting Sliding Mode Command (FSTSMC) method. Notably robust against parameter uncertainties and payload disturbances, the proposed scheme ensures finite-time convergence even in the presence of external disturbances, while effectively reducing chattering. To assess the effectiveness of the proposed methods, comprehensive comparisons are made with traditional control techniques, including Proportional–Integral (PI), Integral Sliding Mode Control (ISMC), and Super-Twisting Sliding Mode Control (STSMC). The simulation results, obtained using MATLAB®/SIMULINK® under various speeds and mechanical torque conditions, demonstrate the superior performance and robustness of the proposed approaches. This study presents a thorough experimental analysis of a 250 W four-phase 8/6 SRG. The generator was connected to a DC resistive load, and the analysis focuses on assessing its performance and operational characteristics across different rotational speeds. The primary objective is to validate and confirm the efficacy of the SRG under varying conditions.

Influence of flux estimation in performance of direct torque control of PMSM

Permanent magnet synchronous motors (PMSMs) are extensively used in high-performance industrial applications. High dynamic response can be achieved by means of direct torque control (DTC). The main advantage of DTC is that coordinate transformations and pulse width modulation (PWM ) generation are not needed, however, classical DTC produces high torque ripple. This paper presents a comparison of different flux estimation methods to implement DTC drive systems, and shows the influence of the choice of estimation method on torque ripple.

A new flux and multilevel hysteresis torque band DTC with lookup table‐based switched reluctance motor drive to suppress torque ripple

SummaryThe switched reluctance motor (SRM) is a prominent electrical machine drive with low cost and good performance in different drive applications. This machine's main drawbacks are torque ripple and flux ripple. However, the existing SRM‐operated direct torque control (DTC) Voltage vectors (VVs) give high torque ripples due to improper sector division and minimum selection of VVs switching states. On the other hand, a two‐level hysteresis torque band can result in torque ripples. Therefore, this paper proposed DTC using 16 partitions, active small and large VVs, and a multilevel hysteresis torque band (MHTB) strategy to mitigate the torque ripple further. More active VVs (i.e., 16) are employed in the modified sector‐based switching tables, suppressing the torque ripples. The proposed strategy is verified and validated using MATLAB/Simulink. The detailed result discusses the response of torque, flux, and speed of SRM. The DTC‐operated SRM drive experimental results prove the effective minimization of torque ripples in the proposed DTC compared to the existing DTC.

Design of a segmented switched reluctance drive for a light electric vehicle

The light electric vehicle market requires better performance motors with less or even without permanent magnets. Switched reluctance motors (SRM) are among the best placed to meet this goal, despite they have lower power density, higher torque ripple, and are noisier than synchronous permanent magnet motors. Segmented stator switched reluctance motors (SSSRM) can reduce these drawbacks of conventional SRMs due to their modular construction and shorter flux paths. This paper presents a procedure for designing an SSSRM for a light electric vehicle. First, the output torque equation is derived from a simplified non linear energy conversion loop, and then guidelines for its design are given. Once the preliminary sizing of the SSSRM has been carried out, simulation using electromagnetic finite element analysis is performed. Then, the complete drive is simulated and validated using Matlab-Simulink and some results of the definitive finite element analysis (magnetization curves and static torque curves).

Design Modeling and Prototyping of a 55 Watts Surface Mounted PM Machine With High Torque and Low Torque Ripple for Cooling Fan Application

Design Modeling and Prototyping of a 55 Watts Surface Mounted PM Machine With High Torque and Low Torque Ripple for Cooling Fan Application

GWOPID-MRAS based Speed Estimation and Speed Control of Sensorless Induction Motors

Sensorless AC motor drives have grown in popularity recently in a variety of applications, from industrial to domestic electrical equipment. FOC and DTC are popular control methodologies in contemporary alternating current (AC) structures. They can achieve good performance for AC motor drives by creating a decupled flux and torque control. However, both have limitations and drawbacks, such as the vector control's dependence on machine parameters and DTC's high flux and torque ripples. This paper proposes a new control method, in which the speed of an induction motor is controlled by Grey Wolf Optimizer (GWO) based PID controller. This method utilizes both FOC, DTC and MRAS observer. The GWOPID controller receives the inputs from MRAS observer, the parameters of PID controller are optimized using GWO algorithm by minimizing the speed deviations of an Induction Motor (IM). The proposed method is implemented in MATLAB/Simulink environment and the performance is compared with IFOC speed control method. Findings demonstrated that the proposed method is effectively reducing the speed deviations as compared with IFOC method under different load conditions.

Enhanced Low-Speed Characteristics With Constant Switching Torque-Controller-Based DTC Technique of Five-Phase Induction Motor Drive With FOPI Control

The Classical hysteresis controller-based DTC (C-DTC) of an induction motor is a simple control scheme with better dynamics and steady-state characteristics when compared with the flux-oriented control (FOC) scheme. The major drawbacks of the C-DTC scheme are variable switching frequency and high average torque ripple under different rotor speeds. In this paper, the two-level five-leg inverter-controlled five-phase induction motor drive with constant switching torque controller-based DTC (PI-CST-DTC) scheme is introduced to improve the steady-state performance with constant switching frequency under various operating speeds. However, the proposed PI-CST-DTC exhibits slower torque and slower speed dynamics w.r.t C-DTC which is due to the periodic occurrence of zero vectors under transients. These slower dynamics are improved with the help of the proposed fractional order PI (FOPI) constant switching torque controller-based DTC (FOPI-CST-DTC) method. With the help of the hardware results, it has been verified that the proposed FOPI-based CST-DTC exhibits improved low-speed steady-state and dynamic performance of the five-phase induction motor drive. The proposed CST-DTC techniques with PI and FOPI controllers are compared with C-DTC for torque ripple reduction and %THD analysis and dynamics through hardware results.