Torque Ripple Reduction Method Research Articles

A Novel Harmonic Current Control Method for Torque Ripple Reduction of SPMSM Considering DC-Link Voltage Limit

A Novel Harmonic Current Control Method for Torque Ripple Reduction of SPMSM Considering DC-Link Voltage Limit

Electromagnetic Characteristics Analysis and Torque Ripple Reduction for Doubly Salient PM Machine

In this paper, the air-gap field modulation analysis and torque ripple reduction method for doubly salient permanent magnet motor (DSPMM) are presented. Based on the flux linkage distributions in the motor, the equivalent magnetic circuit models for permanent magnet (PM) and armature winding excitations are built, respectively. The air-gap magnetomotive forces (MMFs) caused by PM MMF and armature MMF can be obtained by combining the air-gap permeance and equivalent magnetic circuit models. The electromagnetic properties of the DSPMM are investigated from the perspective of air-gap field modulation principle. It is revealed that multiple field harmonics contribute to torque generation, and the torque ripples of the DSPMM are mainly caused by the cogging torque. To reduce the torque ripples, the 5th or 7th harmonic currents can be injected into the armature winding to compensate the cogging torque, and their analytical formulas will also be given. The finite element simulations and experiments are carried out to verify the results of theoretical analysis and the effectiveness of the proposed control method.

Torque-Ripple Reduction of Permanent Magnet Synchronous Machine Drives Based on Novel Speed Harmonic Control at Low-Speed Operation

Torque ripple reduction methods based on harmonic current injection for PMSM drives have been widely discussed, while the performance of torque-ripple-model (TRM) based methods are limited due to model accuracy as well as the rotor position errors, and the speed harmonic control based methods still cannot get rid of the impact of the phase information of speed harmonics, which results in remaining torque ripples and the difficulty in designing speed harmonic controller. In this paper, the unique relationships between the quadrature magnitudes of speed harmonics and harmonic currents are derived considering the minimal conduction copper loss by the harmonic currents. Based on that, a novel torque ripple reduction method based on speed harmonic control is proposed, wherein a novel speed harmonic controller is presented to regulate the quadrature magnitudes of speed harmonics, so that the phase of speed harmonics is avoided in the speed harmonic controller. Also, the proposed speed harmonic controller aims to generate harmonic current references. The proposed methodology is evaluated by experiments and is verified to reduce torque ripples of PMSM drives effectively.

An Online Torque Sharing Function Method Involving Current Dynamics for Switched Reluctance Motor Drives

This article proposes an online torque sharing function (TSF) method for torque ripple reduction in switched reluctance machines (SRMs). The proposed TSF takes the current dynamics and induced electromotive force (EMF) into account by establishing a new online current profile generation technique. First, a primary phase current reference derived from the torque reference is applied to the SRM. Then, the decaying phase current after the turn-off angle is sampled and it is used to update the current reference. A new online optimization strategy is performed to shape the current reference during the operation of the machine. Due to the proposed current profile generation technique, the optimization process is decoupled to independently minimize the torque ripple by optimizing the turn-on angle and minimizing copper losses by optimizing the turn-off angle. Compared to the conventional TSFs and existing optimization-based TSFs, the proposed TSF achieves accurate torque control, improved torque–speed capability, reduced torque ripple, and better current tracking performance. Simulations and experiments are performed on a three-phase 12/8 SRM under various operating conditions to validate the proposed online TSF method.

A Review of Torque Ripple Reduction Design Methods for Radial Flux PM Motors

Nowadays the efficient use of energy is a major issue in applications such as electric vehicles. However, there are some phenomena that affect electric vehicle performance. One of those phenomena is the torque ripple of electric motors, which interferes with traction and the suspension system (causing vibration that stresses this system), and it can also introduce electric current harmonics into the battery, reducing its life, since torque ripple is partly a consequence of non-sinusoidal back EMF. For those reasons this is a topic worth investigating. The torque ripple of permanent magnets (PM) motors can be reduced in design or through control. Since control techniques have been reviewed and design methods have not, this paper presents a comparison of several design techniques to reduce torque ripple by different approaches and categorize them to show the characteristics of each group. A discussion is then made about the advantages and disadvantages of the designs, in general, as well as some comments about the missing, but important information, in the papers, such as the effects on efficiency. The study shows that a combination of methods provide the best results, although it complicates fabrication and suggests that this is a promising line of future investigation on torque ripple reduction methods.

Torque Ripple and Cogging Torque Reduction Method of IPMSM Using Asymmetric Shoe of Stator and Notch in Stator

Torque Ripple and Cogging Torque Reduction Method of IPMSM Using Asymmetric Shoe of Stator and Notch in Stator

A torque ripple reduction method using field current injection for doubly salient motor

Doubly salient motor (DSM) is widely used owing to attractively in high-speed operation capability. However, there is a shortcoming of torque ripple for the non-sinusoidal nonlinear structure, for the purpose of solving this problem, this paper presents a torque ripple reduction strategy by field current injection for doubly salient motor. Initially, the armature current control method of the DSM adopts the multi-sine superposition (MSWS) driving scheme, combined with finite element and Fourier analysis methods to establish the output torque and torque ripple model, where the torque of the DSM is mainly composed of the 1st, 2nd, and 4th harmonic component, and the torque ripple is mainly composed of 3rd harmonics component. Then, a field current injection approach is presented, and calculate the magnitude and phase of the injected component, which serves as a quantitative analysis foundation for torque ripple suppression. Finally, the experimental results illustrate the superiority of the presented method in torque ripple optimization.

A torque sharing function with online compensation of excitation current control method for torque ripple reduction in electric excitation auxiliary switched reluctance motor drives

A torque sharing function with online compensation of excitation current control method for torque ripple reduction in electric excitation auxiliary switched reluctance motor drives

Torque Ripple according to The Number of Permanent Magnet Poles of Magnetic Gear

The power transmission of magnetic gears, based upon the at-tractive force of magnets, does not involve direct contact between the power transmission shafts. Thus, vibration or noise, due to friction, can be reduced. However, magnets and iron cores, which are the main components of magnetic gears, generate cogging torque. This increases torque ripples that are the cause of the noise and vibration of permanent-magnet (PM) machines. In this study, a torque ripple reduction method, using the combination of number of poles and number of pole pieces was proposed. This method uses the structural characteristics of magnetic gears only. This method was suggested instead of the existing torque ripple reduction methods for PM machines to reduce the torque ripples of magnetic gears. Furthermore, the correlation between the numbers of poles, pole pieces, and torque ripples was analyzed. From this analysis, a design guideline that minimizes torque ripples in the initial design of magnetic gears was proposed.

An Injected High Frequency Current Reference Generation Method for Torque Ripple Reduction in PMSM

An Injected High Frequency Current Reference Generation Method for Torque Ripple Reduction in PMSM

Coupling Harmonic Voltages Considered Harmonic Currents Injection Method for Torque Ripple Reduction

Coupling Harmonic Voltages Considered Harmonic Currents Injection Method for Torque Ripple Reduction

Investigation on the Torque Ripple Reduction Method of a Hybrid Electric Vehicle Motor

Owing to the development of electric vehicles (EVs), research and development are underway to minimize torque ripple in relation to vibration and noise in EV motors. Although there are various ways to reduce torque ripple, this study analyzes the torque ripple, cogging torque, total harmonic distortion (THD), and magnetic flux density distribution for the three rotor shapes of interior permanent magnet synchronous motors, which are widely employed in EVs. To reduce the torque ripple while retaining the required average torque, the barrier shape is optimized, and wedge skew is applied. First, regarding the rotor barrier shape, torque ripple is primarily reduced by designing the rotor barrier shape with the response surface method, which is an experimental design method. Additionally, the wedge skew shape considering the bidirectional rotation and fabrication was applied to the stator shoe as a step and analyzed using three-dimensional finite element analysis. When designing the wedge skew, the layer subdivision according to the axial length, wedge skew diameter, and wedge skew position was analyzed and improved. The torque ripple reduction method in this paper can be applied not only to motors for EVs or Hybrid EVs (HEVs) but also all types of permanent magnet synchronous motors.

Deadbeat Harmonic Current Control of Permanent Magnet Synchronous Machine Drives for Torque Ripple Reduction

This article proposes a torque ripple reduction method based on speed ripples for permanent magnet synchronous machine (PMSM) drives. The torque ripples are first estimated based on speed harmonics at low speed. Based on that, the optimal harmonic current reference is then derived to fully compensate for the estimated torque ripple with minimum stator resistive loss. An extended state observer (ESO)-based deadbeat harmonic current controller (DHCC) is also presented in the rotor reference frame (RRF) to inject the optimal harmonic currents with good performance in steady state and transients. To extract the harmonic currents for harmonic current control and speed harmonics for torque ripple estimation with fast convergence and good accuracy, an adaptive linear neural (ADALINE) network-based filter is implemented in this article. Simulations and experiments are carried out to show the validity and performance of the proposed torque ripple reduction method.

Torque Ripple Reduction Method for Permanent Magnet Synchronous Machine Drives With Novel Harmonic Current Control

Torque ripple reduction has become an active research area for permanent magnet synchronous machine (PMSM) drives. This paper presents a novel torque ripple reduction method based on harmonic current control. In the proposed method, the optimal harmonic current solution based on the torque ripple model with minimum stator resistive loss is derived in the rotor reference frame (RRF). The optimal harmonic currents are injected by the proposed harmonic current controller (HCC), wherein the magnitude of harmonic currents are defined as controller variables. To estimate the harmonic currents, the proposed method also utilizes the least mean square (LMS) based adaptive filter (AF), wherein the coefficients are defined as feedback to the proposed HCC. The proposed methodology is demonstrated using both simulations and experiments and is verified to reduce torque ripples of PMSM drives over a wide range of speeds.

PMSM Current Shaping for Minimum Joule Losses While Reducing Torque Ripple and Vibrations

This paper presents a current shaping method for torque ripple and mean air-gap radial force-shape harmonics reduction, under minimum Joule losses, used for air-born and structure-born vibration reduction in 3-phase PMSM electric drives. The main source for structure-born noise in electric powertrains is the torque ripple, while the main source for air-born noise are the radial air-gap forces. The proposed method uses a Fourier-decomposed LUT model obtained from updating the 2D electromagnetic FE model using test-bench results. Modal testing is used to update the structural model, and the vibration response on the machine full RPM range is determined using the vibration-synthesis method. The proposed current shaping algorithm is deterministic and can be used on any topology of 3-phase PMSMs. The torque and mean air-gap force harmonics that are intended for reduction can be arbitrary selected and their minimization can be fully completed if the maximum current and voltage constraint are respected. On the machine under test, vibration reduction is accomplished, especially for the mechanical orders that interact with the second mode-shape.

Design and Optimization of a Fault Tolerant Modular Permanent Magnet Assisted Synchronous Reluctance Motor With Torque Ripple Minimization

This article proposes a new asymmetric modular permanent magnet assisted synchronous reluctance motor (PMaSynRM) to offer low torque ripple and high reliability. First, the stator is segmented into three modules without magnetic coupling. The influence of flux gaps between modules is investigated on torque performance. For the torque improvements, the multilevel optimization strategy is conducted, which simultaneously enhances the fault-tolerant capability. Besides, the torque ripple reduction methods are proposed with the asymmetric rotor and shifted end-slots. The analytical formulae of asymmetric flux barrier angle are derived. Then, the asymmetric flux barrier is designed to reduce the 12th harmonic, and the end-slots are shifted to minimize the additional 2nd harmonic component caused by flux gaps. Finally, the enhanced fault-tolerant capability of the proposed modular PMaSynRM is also evaluated. The effectiveness of the proposed approach is verified by both simulation and experiment.

A Novel and Simple Torque Ripple Minimization Method of Synchronous Reluctance Machine Based on Torque Function Method

Synchronous reluctance machine (SynRM) has been studied widely in order to reduce its high torque ripple and improve its low power factor. This article proposes a torque ripple reduction method for SynRM by defining a novel parameter-torque function. With the help of torque function, the optimal currents aiming to compensate torque harmonics are obtained. The advantage of the proposed method is that torque function can be obtained easily and torque ripple reduction can be achieved by a simple control method. For the purpose of verifying the proposed method, both simulations and experiments are performed. Finally, the influence of power supply and parameter uncertainty on the proposed method has also been discussed.

Enhanced Model Predictive Direct Torque Control Applied to IPM Motor With Online Parameter Adaptation

This paper presents an improved model-based predictive direct torque control (MPDTC) to improve torque accuracy and reduce torque ripples which is a major issue in conventional direct torque control (DTC). Hysteresis controllers and traditional DTC switching tables are replaced by a model predictive controller to achieve an online optimization for voltage space vector selection and optimal duty ratio modulation method for torque ripple reduction. In order to provide an accurate motor model for MPDTC, novel offline and online motor parameter estimation methods are proposed to improve performance of the proposed MPDTC. The proposed parameter estimation adopts Popov's hyper stability theorem to estimate accurate motor parameters, such as stator resistance, stator inductance and rotor flux linkage, which are critical for torque and flux estimation. The parameter adaptive MPDTC is verified by a hardware in the loop emulation platform, and experiment result is demonstrated using a dynamometer test bench, which therefore proves the feasibility of the proposed method.

Investigation on Contribution of Inductance Harmonics to Torque Production in Multiphase Doubly Salient Synchronous Reluctance Machines

This paper investigates the contribution of each order inductance harmonic to the torque (both average torque and torque ripple) of multiphase doubly salient synchronous reluctance machines (DS-SRMs). Such machines are similar to switched reluctance machines but supplied with sine wave currents. The investigations in this paper are as follows. First, a general analytical torque model based on Fourier series analysis of inductances has been built for machines with different phase numbers, slot/pole number combinations, and also winding configurations. The instantaneous torque for DS-SRMs with any given phase number can then be accurately predicted. Using such model, contribution of each order inductance harmonic to torque can be investigated separately. It is found that the torque ripple frequency of the DS-SRM only depends on phase number. For example, for an m-phase machine, there will be m $\times $ kth-order torque ripple if mod(mk, 2) = 0, where m is the phase number and k is a natural number. This paper also explains why certain phase numbers inherently produce lower torque ripple than others. The findings in this paper provide a future direction for potential torque ripple reduction methods either from machine design or advanced control. The simulations have been validated by experiments using a six-phase DS-SRMs.

Torque Ripple Reduction in Five-Phase IPM Motors by Lowering Interactional MMF

This paper proposes a torque ripple reduction method for a five-phase interior permanent magnet (PM) motor by shifting asymmetrical rotor poles. The key of this method is to consider the PM torque ripple, reluctance torque ripple, and cogging torque simultaneously from two aspects. First, the main interactional harmonic, contributing to PM torque ripple, between stator magnetic motive force (MMF) and rotor MMF is developed. Then, the appropriate combination of unequal pole arcs is adopted to eliminate the main interactional harmonic. Second, the asymmetrical rotor pole-pair is selected as a repeating unit which produces cogging torque and reluctance torque with consistency in waveforms and phases. Then, three methods for shifting asymmetrical rotor pole-pair are proposed showing that the torque ripple can be reduced greatly and the lower-order harmonics of radial force is acceptable when the shifting angle of the repeating unit is 4.5 mechanical degrees. Through theoretical analysis and experimental test, it is verified that the proposed motor can offer lower torque ripple even under deep flux-weakening region.