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The purpose of this paper is to reduce the torque ripple but not to decrease the average torque of synchronous reluctance machines by using one step or more than two axially laminated rotors with asymmetric flux-barrier.

A 24-slot four-pole synchronous reluctance machine with overlapping windings and asymmetric flux-barrier in the rotor is, first, described and designed by finite element (FE) method for maximizing average torque. The dimensions of asymmetric flux-barrier including the pole span angle and flux-barrier angle will be optimized to minimize the torque ripple and its influence on the average torque is also investigated by FE analysis. The impact of current angle on the average torque and torque ripple are also analysed. The step laminations together with the asymmetric flux-barrier are employed for further torque ripple reduction which can consider the both rotation directions.

The torque ripple of synchronous reluctance machine can be significantly reduced by employing asymmetric flux-barrier but the average torque is not reduced.

The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application. The 24-slot/four-pole synchronous reluctance machine with single-layer flux-barrier has been employed in this analysis, but this work can be continued to investigate the synchronous reluctance machine with multilayer flux-barrier. This asymmetric flux-barrier can be easily applied to permanent magnet (PM)-assisted synchronous reluctance machine and the interior PM machine with flux-barrier in the rotor, since the space which is used for PM insertion is the same as the SynRM machines.

This paper has analysed the torque ripple and average torque of synchronous reluctance machines with asymmetric flux-barrier and step laminations with asymmetric flux-barrier. The torque ripple can be reduced by this flux-barrier arrangement. The difference of this technique with the other techniques such as stator/rotor skew is that the average torque can be improved.

The purpose of this paper is to investigate a new cause of torque ripple in interior permanent magnet (IPM) alternating current (AC) motors, which is common but has hardly been studied. The paper also proposes a new method to suppress the total torque ripple.

Besides the well-known cogging torque and mutual torque ripple, a new ripple which exists in the reluctance torque is found. It is verified with both analytical model and finite element analysis. Also, a novel method is proposed to reduce the reluctance torque ripple, with experimental validation.

It is usually said that the winding inductances of an IPM AC motor vary sinusoidally with the rotor position, thus, the d-axis and q-axis inductances are constant, whilst the reluctance torque is smooth. However, in most practical motors, the inductances vary irregularly, causing a significant ripple in the reluctance torque. Moreover, in machine design, it is always desirable to suppress the cogging torque as much as possible. However, in this paper, it is proved that the cogging torque can remain and be used to cancel the reluctance torque ripple.

Torque ripple in the IPM AC motors is usually reduced by suppressing the cogging torque and making both back electromotive forces and currents sinusoidal. However, this paper reveals the new cause of the torque ripple due to the irregular variation of winding inductances. Moreover, the paper gives a new method to cancel the reluctance torque ripple with the cogging torque.

The purpose of this paper is to investigate torque ripple and magnetic force on the teeth in interior permanent magnet (IPM) machines over a wide range of speed operation for electrical power steering (EPS) applications.

The flux-weakening capability of IPM machines has been analysed by finite element method considering the effect of cross-coupling between d- and q-axis current. The traditional method of analysing torque ripple is based on constant torque and flux-weakening region. However, the cross-coupling need to be considered when applying this technique to flux-weakening region. Meanwhile, the torque ripple with current amplitude and angle and with different speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth due to the separated teeth with stator yoke is also investigated during the constant torque and flux-weakening region.

The torque ripple and magnetic force on teeth in IPM machine are dependent on current and current angle. Both the lowest torque ripple and magnetic force on teeth exist over the whole torque-speed region.

The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple and magnetic force on teeth are not considered in this application. The 12-slot/10-pole IPM machine has been employed in this analysis, but this work can be continued to investigate different slot/pole number combinations.

This paper has analysed the torque ripple and magnetic force on the teeth in IPM machines for EPS application over a wide range of operation speed, which are the main cause of vibration and acoustic noise. The variation of torque ripple with current amplitude and angle as well as speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth is also investigated over the whole torque-speed region.

The purpose of this paper is to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of synchronous reluctance machine with emphasis on output torque capability and torque ripple.

AC synchronous reluctance machine (SynRM) or permanent magnet assisted SynRM presently receives a great deal of interest, since there is less or even no rare-earth permanent magnet in the rotor. Most of SynRM machines employ a stator that is originally designed for a standard squirrel cage induction motor for a similar output rating and application, or the SynRM machine with 24-slot, four-pole are often directly chosen for investigation in most of the available literature. Therefore, it is necessary to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of SynRM machine with emphasis on output torque capability and torque ripple.

The average torque decreases with the increase of the pole numbers but remain almost constant when employing different stator slot numbers but with the same pole number. In addition, the torque ripple decreases significantly with the increase of the stator slot number. The machine with double-layer flux-barrier in the rotor has the biggest average torque, while the machines with three- and four-layer flux-barrier in the rotor have almost the same average torque but their value is slightly smaller than that of machine with double-layer flux-barrier. However, the machine with three-layer flux-barrier has the lowest torque ripple but the highest torque ripple exists in the machine with double-layer flux-barrier.

The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application.

This paper has analyzed the torque ripple and average torque of SynRMs with considering slot/pole number combinations together with the flux-barrier number.

The purpose of this paper is to describe a new method for sensorless hysteresis direct torque control (HDTC) algorithm for permanent magnet synchronous motor to minimize torque ripple and electromagnetic interference (EMI) noises.

The design methodology is based on space vector modulation of electrical machines with digital vector control. MATLAB simulations supported with experimental study under C++ are used.

The simulation and experimental results of this proposed algorithm show adequate dynamic torque performance and considerable torque ripples reduction as well as lower current ripples, lower EMI noise level as compared to traditional HDTC.

This research is limited to PMSM, however the research can be extended to include induction motor as well. In addition, the actual mathematical relation between the torque ripple and flux ripple can be studied to set the flux and torque bands width in reasonable value, and this relationship can be used to select switching time of the active selected vectors.

The implementation of the proposed algorithm in microcontroller embedded systems is described. It requires no PI controller in the torque control loop In addition, based on existence direct torque control equipment, it is only required to change the software switching algorithm, to provide smooth torque, given that the switching frequency of the inverter module is more than or equal to 15 kHz and the system is supplied with timers.

The algorithm used in this work utilizes the output of two hysteresis controllers used in the traditional HDTC to determine two adjacent switching vectors per one sample time. The algorithm also uses the magnitude of the torque error, magnitude of the flux error and stator flux position to select the switching time for the selected vectors to control the applied average voltage level in such a way that the torque ripple is minimized. The selection of the switching time of the selected active vectors utilizes novel table structure which reduces the complexity of calculation. This work is directed to designers of ac motor drive system who seek smooth torque performance as well as low EMI noise level.

The paper aims to provide an adaptive neural network controller for permanent magnet synchronous motor (PMSM) under direct torque control (DTC) algorithm to minimize the torque ripple and EMI noise.

The design methodology is based on vector control used for electrical machines. MATLAB simulations supported with experimental study under C++ are used.

The simulated and experimental results show that considerable torque ripple as well as current ripple and EMI noise reduction can be achieved by utilizing adaptive neural switching algorithm to fire the inverter supplying the PMSM.

This research is limited to PMSM, however the research can be extended to include other AC motors as well. In addition, the following points can be studied: the effects of harmonics in control signals on the torque ripple can be analyzed; the actual mathematical relation between the torque and flux ripple can be studied to set the flux and torque bands width in reasonable value; different neural network algorithms can be applied to the system to solve the similar problems.

Based on existing DTC control system, it is only required to change the software switching algorithm, to provide smooth torque, given that the switching frequency of the inverter module is more than or equal to 15 MHz and the system is supplied with timers. In addition a relatively higher DC voltage may be required to achieve higher speed compared with the traditional DTC.

In this paper, the stator flux position, and errors due to deviations from reference values of the torque and stator flux are used to select two active vectors while at the same time the absolute value of the torque error and the stator flux position are used neural network structure to adapt the switching of the inverter in order to control the applied average voltage level in such a way as to minimize the torque ripple, so instead of fixed time table structure, a neural network controller is used to calculate the switching time for the selected vectors and no PI controller is used as the case in the traditional space vector modulation. This work is directed to motor drive system designers who seek highly smooth torque performance with EMI noise reduction.

The paper seeks to provide an adaptive fuzzy logic controller for permanent magnet synchronous motor (PMSM) under direct torque control (DTC) algorithm to minimize the torque ripple.

The design methodology is based on vector control analysis. MATLAB simulations supported with experimental study under C++ are used to execute the proposed work.

The results show that considerable torque ripple reduction as well as considerable current ripple reduction can be achieved by utilizing adaptive fuzzy switching algorithm to fire the inverter supplying the PMSM.

This research is limited to PMSM, however the research can be extended to include other AC motors as well. In addition, the following points can be studied, the effects of harmonics in control signals on the torque ripple. Digital and active filters as solution to these harmonics can be also addressed. The actual mathematical relation between the torque ripple and flux ripple can be studied to set the flux and torque bands width in reasonable value.

Based on existence DTC control system, it is only required to change the software‐switching algorithm, to provide smooth torque, given that the switching frequency of the inverter module is more than or equal to 15 kHz and the system is supplied with timers. In addition, a relatively higher DC voltage may be required to achieve higher speed compared with the traditional DTC.

In this paper, the stator flux position, and errors due to deviations from reference values of the torque and stator flux are used to select two active vectors while at the same time the absolute value of the torque error and the stator flux position are fuzzified to adapt the switching of the inverter in order to control the applied average voltage level in such a way as to minimize the torque ripple, so instead of fixed time table structure, a fuzzy logic is used to calculate the switching time for the selected vectors and no PI controller is used as the case in the traditional‐space vector modulation. This work is directed to motor drive system designers who seek highly smooth torque performance with fast response.

The torque ripple and fault-tolerant capability are the two main problems for the switched reluctance motors (SRMs) in applications. The purpose of this paper, therefore, is to propose a novel 16/10 segmented SRM (SSRM) to reduce the torque ripple and improve the fault-tolerant capability in this work.

The stator of the proposed SSRM is composed of exciting and auxiliary stator poles, while the rotor consists of a series of discrete segments. The fault-tolerant and torque ripple characteristics of the proposed SSRM are studied by the finite element analysis (FEA) method. Meanwhile, the characteristics of the SSRM are compared with those of a conventional SRM with 8/6 stator/rotor poles. Finally, FEA and experimental results are provided to validate the static and dynamic characteristics of the proposed SSRM.

It is found that the proposed novel 16/10 SSRM for the application in the belt-driven starter generator (BSG) possesses these functions: less mutual inductance and high fault-tolerant capability. It is also found that the proposed SSRM provides lower torque ripple and higher output torque. Finally, the experimental results validate that the proposed SSRM runs with lower torque ripple, better output torque and fault-tolerant characteristics, making it an ideal candidate for the BSG and similar systems.

This paper presents the analysis of torque ripple and fault-tolerant capability for a 16/10 segmented switched reluctance motor in hybrid electric vehicles. Using FEA simulation and building a test bench to verify the proposed SSRM’s superiority in both torque ripple and fault-tolerant capability.

High torque ripple is the significant challenge of the synchronous reluctance machine in household electric appliances, electric vehicles and so on. This paper aims to present an optimized design of a synchronous reluctance rotor structure to reduce the torque ripple with improving the average torque by the particle swarm optimization (PSO) algorithm.

The optimization of rotor geometries has been investigated. Most of the rotor parameters such as the width of iron parts, the width of barriers along d and q axes and the endpoint angle of barriers are optimized by a new method using the PSO algorithm. After optimization, the resulted optimum design along with the initial design is simulated by two-dimensional finite element method and results are compared. At the end, a prototype is constructed and tested. Results of the experiment are compared with the simulation results where acceptable adoption is yielded.

Minimizing the torque ripple without losing the average torque is an important achievement of the synchronous reluctance motor (SynRM) optimization; furthermore, the finite element analysis and experimental results indicate that the torque ripple of the SynRM with the optimized rotor is reduced significantly. Also, increasing the number of optimization parameters can effectively obtain an accurate shape of the SynRM barrier.

Because of the high number of parameters in synchronous reluctance rotors, the majority of proposed optimizations did not use all geometric parameters of the rotor and tried to simplify the optimization by ignoring several optimization parameters or reducing the number of flux barriers. In this optimization, most of the rotor parameters have been used to achieve the precise barrier shape with the aim of reducing the torque ripple in SynRM.

During the design process of synchronous reluctance motors (SynRMs), one crucial step, after its main dimensioning, is optimizing the rotor geometry for maximum average torque and minimum torque ripple. However, because of the complexity of rotor flux-barrier layers geometry, the number of rotor geometrical parameters is high and this step could be quite complex and time-consuming. To obtain a good performance, one needs a robust algorithm to optimize the rotor geometry. The purpose of this paper is to present a sequential iterative method for rotor shape optimization in SynRMs based on the per-unit rotor model to maximize the average torque and minimize the torque ripple.

In the presented method, at first, rotor geometrical parameters are classified into several groups based on their geometrical similarities, and then optimization is done on these individual groups iteratively. The method starts with an arbitrary feasible rotor geometry and proceeds to optimize it. Because the method’s performance depends on initial rotor geometry, different cases are studied to investigate the convergence and robustness of the method. The MATLAB software is used to implement the optimization algorithm, and the ANSYS Maxwell software is used for the finite element analysis.

The performance of the proposed method is studied on a three-phase 0.75 kW-1,500 rpm permanent magnet assisted SynRM. The results show that the method improves the average torque while reducing the torque ripple. Even if the method starts with an inappropriate initial rotor geometry, it is robust enough and converges within an acceptable number of iterations.

The value of this paper is in introducing a per-unit rotor model. When the authors optimize the rotor geometry for a specific motor rating, it can be scaled up or down for other ratings with little effort. In this work, the number of rotor poles is four and the number of rotor flux-barrier layers per pole is three. Other combinations could be analyzed in future studies.