Incorporating control trajectories with the direct torque control scheme of interior permanent magnet synchronous motor drive

Interior permanent magnet (IPM) synchronous machines have gained increased attention for applications in electric vehicle, variable speed wind turbine, industrial drives, etc., because of their high torque density, wider speed range and compact construction. The authors present a detailed analysis and modelling of control trajectories and incorporate those trajectories in the direct torque control (DTC) scheme of an IPM synchronous motor drive, for constant-torque and constant-power operating regions. The control trajectories are implemented on a real-time digital signal processor. Because the inputs to the inner torque control loop of DTC are the references for the torque and the amplitude of the stator flux linkage (λ_s), they are transformed in the T-λ_s plane, than in the i_d - i_q plane in the indirect control. The modelling and experimental results are presented. Results show very good dynamic and steady-state performances of direct torque controller, incorporating these control trajectories.     

High-performance current control for switched reluctance motors based on on-line estimated parameters

To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-performance current controller is necessary. This study presents a high-performance current controller for SRM drives. A Bspline neural network is used to model the non-linearity of the SRM and estimate back electromotive force (EMF) and incremental inductance on-line in real time. The on-line modelling scheme does not require a priori knowledge of the machine?s electromagnetic characteristics. Based on the on-line estimated parameters, a current controller with adjustable PI gains and back-EMF decoupling is implemented. The performance of the current controller has been demonstrated in simulation and experimentally using a four-phase 8/6 550 W SRM drive system.     

Experimental Investigations on Computer-Based Methods for Determination of Static Electromagnetic Characteristics of Switched Reluctance Motors

Because of the doubly salient structure of the switched reluctance motor (SRM) and its intentional operation in deep magnetic saturation for higher power density, its static electromagnetic characteristics are highly nonlinear functions of rotor position and phase current. This makes the accurate experimental measurement/determination of these characteristics a difficult task. This paper presents a comprehensive discussion and analysis on the different (most practiced) computer-based methods for the determination of these characteristics for a typical SRM. A digital signal processor (DSP)-based completely automated SRM drive system has been used for these studies. For all the offline computations, user-friendly MATLAB/Simulink-based models have been developed. The experimental methods, computational models, measurement results, and appropriate postmortem discussions for the determination of static flux linkage, inductance, and electromagnetic torque characteristics for an 8/6 four-phase SRM are reported.      

Direct torque and flux control of an IPM synchronous motor drive using a backstepping approach

A novel direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive using an adaptive backstepping technique is presented. Closed-loop regulation of the speed, torque and stator flux linkage is achieved by a non-linear controller. Using Lyapunov analysis, the stability of the controller is guaranteed. The reference voltage vectors are generated by a space vector modulation (SVM) unit, which replaces the switching table in the conventional direct torque control (DTC) scheme. While retaining its main advantages, the proposed backstepping controller features reduced torque and flux ripples as compared to the classical DTC. On the one hand, a comparison with the proportional-integral (PI) direct torque and flux control (DTFC) scheme shows that the proposed approach is superior. Experimental results confirm the effectiveness of the proposed method.     

Modeling switched-reluctance Machines by decomposition of double magnetic saliencies

This paper presents a novel analytical model for a switched-reluctance machine (SRM) based on decomposition of its inherent double joint magnetic saliencies due to rotor and stator salient poles and saturation of magnetic field at high stator currents. With this method, the magnetic characteristics of the motor, such as flux linkage and incremental inductance, are decomposed to vector functions of rotor position and phase current. Dynamic state and torque equations for the SRM are derived on the basis of this representation. The proposed model is appropriate for online identification and for sensorless position control algorithms. It is easy to implement and computationally efficient. Comparison of the predicted motor magnetic characteristics to machine data from finite-element analysis verifies the accuracy of the model.     

分布式驱动用永磁同步电机电磁转矩的解析计算

针对分布式驱动电动汽车车身阶次振动和车内噪声的主要振源—外转子表贴式永磁同步电机6k阶（ ）转矩波动,提出了一种分布式驱动用永磁同步电机电磁转矩的解析计算方法。基于永磁同步电机磁场畸变,对永磁磁极在均匀气隙中的径向分量进行了傅里叶级数分解,通过磁链、电压的计算,最终得到电磁转矩的解析解,为永磁同步电机的阶次振动与振源识别提供了理论基础。当不考虑电流谐波的影响时,对电磁转矩做了阶次分析,论证了由永磁体磁场谐波引起的电磁转矩波动频率是电源频率的6k倍频。最后,通过有限元计算验证了该解析计算结果。     

Direct instantaneous torque control of switched reluctance machines using 4-level converters

Direct instantaneous torque control (DITC) of switched reluctance machines (SRMs) using a novel 4-level converter is presented. The described DITC control strategy proposes detailed torque control regions and suitable control schemes. Using the 4-level converter, DITC can overcome voltage limitation of asymmetric converters and has a fast magnetisation and demagnetisation to improve dynamic performance and efficiency. For integrated advantages of DITC and 4-level converters, a suitable control scheme is described and analysed. Finally, the proposed DITC method of SRM drive systems using the 4-level converter is verified by simulation and comparative experiments.     

A fast‐built flux‐linkage model for switched‐reluctance motors

Abstract

This paper presents a simplified and fast‐built model for the analytical representation of the flux linkage of a switched‐reluctance motor (SRM). Presently, most conventional methods require numerous flux‐linkage‐current‐position data to build a model; however, this is time‐ineffective. In the proposed model, the flux linkage is represented by a limited number of Fourier series terms. The coefficients of the Fourier series are determined by the values of the flux linkage at the aligned position, unaligned position and a midway position. At either the aligned or the midway position, the non‐linear relationship between the flux linkage and the phase current is represented by a simplified function, which is derived from a linear relationship — the product of flux linkage and phase current versus phase current — in the saturated region. The proposed model can be built with only five data points of static characteristics, which are simply obtained through finite‐element analysis (FEA); this allows for easy implementation and high computational efficiency. The accuracy of the proposed model is verified via comparison to measurements of the steady‐state voltage and phase current waveforms of the machine as well as several characteristic curves. The proposed model is shown to have a good degree of accuracy.     

A Sliding Mode Flux-Linkage Controller With Integral Compensation for Switched Reluctance Motor

A novel flux-linkage controller using sliding mode technique with integral compensation (SM-I) is proposed for torque ripple minimization of a switched reluctance motor (SRM). The proposed SM-I controller inherits the advantages of proportion–integration (PI) and conventional SM controller. These make it feasible for the flux-linkage controller to reduce torque ripple by correctly selecting the flux ramps in the limit of available dc-link voltage. Moreover, since the controller is not model-based, it avoids the complexity of mathematical modeling and is easily implemented. Experimental results demonstrate that the proposed controller performs better and can be used as an alternative for nonlinear SRM drive systems.      

Real-Time Verification of AI Based Rotor Position Estimation Techniques for a 6/4 Pole Switched Reluctance Motor Drive

This paper presents real-time verification of an artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) based rotor position estimation techniques for a 6/4 pole switched reluctance motor (SRM) drive system. The techniques estimate rotor position by measuring the three-phase voltages and currents and using magnetic characteristics of the SRM, with the aid of an ANN and ANFIS, in real-time environments. The rotor position estimating techniques are used in a high-performance sensorless variable speed SRM drive. A digital signal processor, TMS320F2812, executes the rotor position estimation. To verify the performance of the ANN and ANFIS based rotor position estimation techniques, a rotor position sensor is mounted with the drive system. The experimental results show that the ANN and ANFIS based rotor position estimation techniques provide good performance at different operating conditions.     

Multiobjective optimization method based on a genetic algorithm forswitched reluctance motor design

In this paper, a novel multiobjective optimization method based on a genetic-fuzzy algorithm (GFA) is proposed. The new GFA method is used for optimal design of a switched reluctance motor (SRM) with two objective functions: high efficiency and low torque ripple. The results of the optimal design for an 8/6, four-phase, 4 kW, 250 V, 1500 r.p.m. SRM show improvement in both efficiency and torque ripple of the motor     

DSP-Based Automated Error-Reducing Flux-Linkage-Measurement Method for Switched Reluctance Motors

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus, it has become a popular research topic in the field of variable-speed drives as well as servo drives. Research on SRMs mainly includes their design, modeling and performance analysis, control, as well as applications. However, for verification of design, performance prediction, as well as development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate and fully automated digital method for the measurement of the magnetic characteristic of SRMs, which includes online offset-error removal and winding resistance estimation. In this method, a digital-signal-processor-based virtual instrumentation for measurement of flux linkage is developed. Then, the results of the measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing with that found via a magnetic analyzer. Finally, the various sources of errors and their contributions to the errors are discussed. The scheme can also be used, in general, for transformers or inductors.     

A novel switched reluctance motor with C-core stators

This paper presents a novel switched reluctance motor (SRM) design in which the stator is simply formed from C-cores. Unlike conventional SRMs, the windings of the new motor can be individually wound into the stator cores without complex winding equipment. Because of the inherent axial field distribution, this type of SRM requires a three-dimensional (3-D) finite-element analysis (FEA) model for detailed flux analysis. This paper proposes an approximated two-dimensional FEA model to speed up computational time. In addition, since the proper current that ensures operation in the saturated region (to maximize torque and efficiency) is often hard to determine systemically, the paper proposes a simple method to determine the optimum operating current so that one can easily decide the rated current and also obtain the maximum motor efficiency. Finally, the paper compares some characteristics of a traditional SRM with those of the proposed SRM. The comparison shows that the proposed SRM performs well in terms of torque and efficiency, and provides a higher degree of flexibility in winding design.     

Improved direct torque control of induction motor with dither injection

In this paper, a three-level inverter-fed induction motor drive operating under Direct Torque Control (DTC) is presented. A triangular wave is used as dither signal of minute amplitude (for torque hysteresis band and flux hysteresis band respectively) in the error block. This method minimizes flux and torque ripple in a three-level inverter fed induction motor drive while the dynamic performance is not affected. The optimal value of dither frequency and magnitude is found out under free running condition. The proposed technique reduces torque ripple by 60% (peak to peak) compared to the case without dither injection, results in low acoustic noise and increases the switching frequency of the inverter. A laboratory prototype of the drive system has been developed and the simulation and experimental results are reported.     

An indirect test method for the characterization of variablereluctance motors

The determination of the characteristics of the variable reluctance motors (both in static and dynamic conditions) represents a quite critical point, due to the heavy nonlinearity of the motor magnetic paths, to the high distortion of the supply voltage from the converter, and to the high level of saturation of the magnetic paths in normal working conditions. This creates a great difficulty in the accurate measurement of the motor magnetic characteristics (saturation curves or flux linkage versus current curves) and consequently in the determination of the mechanical characteristics (static torque versus current and static torque versus rotor position) which are directly related to the saturation curves. The paper proposes an original digital method that, starting from the measurement of the flux linkage in the motor magnetic paths, determines the saturation curves, evaluates the coenergy versus current curves and then the motor torque characteristics in static conditions. It is then shown how the availability of a fast and accurate method for the measurement of the flux linkage allows the determination of the electromagnetic torque in dynamic conditions, too     

On-line mechanical unbalance estimation for permanent magnet synchronous machine drives

An on-line mechanical unbalance estimation for permanent magnet synchronous machine (PMSM) drives is presented. At high speeds, either rotor or mechanical load unbalance generates vibration that can cause mechanical failure such as a defect of a bearing or shaft. To prevent failure and minimise mechanical vibration, the amount of the rotating unbalance should be detected in real time. The information of the estimated unbalance can be utilised to manage an operation to achieve the durability of mechanical parts. The dynamic nature of a mechanical system with a PMSM with regard to unbalance is investigated. From this examination, the models of the stator current in time and frequency domains for PMSMs are presented to develop a robust real-time unbalance estimation scheme. Based on the modelling and analysis of a rotating mechanical system using a PMSM drive, a compact unbalance estimation algorithm is proposed. The algorithm is combined with an open-loop torque observer and an unbalance estimator using a filter. Experimental results show the validation of the developed model and the proposed on-line unbalance estimation scheme.     

Switched Reluctance Motor Design Using Neural-Network Method With Static Finite-Element Simulation

The paper describes a neural network method for optimal design of a switched reluctance motor (SRM). The approach maximizes average torque while minimizing torque ripple, considering mainly the stator and rotor geometry parameters. Before optimization takes place, an experimental validation of the SRM model, based on the finite-element method, is performed. The validation predicts average torque and torque ripple characteristics for several motor configurations while stator and rotor pole arcs are varied. The numerical results are highly nonlinear, and a function approximation of the data is therefore difficult to implement. We therefore interpolate the data by using a neural network based on a generalized radial basis function. The computed results allow us to search for optimum motor parameters. The optimum design was confirmed by numerical field solutions.     

A Novel Flux Linkage Measurement Method for Linear Switched Reluctance Motors

The magnetic characteristics of a linear switched reluctance motor (LSRM) are important in its performance prediction and verification. Owing to the complicated magnetic paths, the measurement of the flux linkage for this type motor has drawn many researchers' attentions. In this paper, a new flux linkage measurement method for LSRMs is proposed to obtain the flux linkage characteristics of LSRMs using an online winding resistance estimation technique. Both the theoretical derivation and the actual implementation of the proposed method are addressed in this paper. In comparison with the search coil scheme and the static resistor scheme, experimental results confirm the validity and accuracy of this method. In short, the proposed method is simple, effective, and easy to be implemented. It is a practical solution for flux linkage measurement of LSRMs and other motors.     

A Novel Universal Steganalysis Algorithm Based on the IQM and the SRM

The state-of-the-art universal steganalysis method, spatial rich model (SRM), and the steganalysis method using image quality metrics (IQM) are both based on image residuals, while they use 34671 and 10 features respectively. This paper proposes a novel steganalysis scheme that combines their advantages in two ways. First, filters used in the IQM are designed according to the models of the SRM owning to their strong abilities for detecting the content adaptive steganographic methods. In addition, a total variant (TV) filter is also used due to its good performance of preserving image edge properties during filtering. Second, due to each type of these filters having own advantages, the multiple filters are used simultaneously and the features extracted from their outputs are combined together. The whole steganalysis procedure is removing steganographic noise using those filters, then measuring the distances between images and their filtered version with the image quality metrics, and last feeding these metrics as features to build a steganalyzer using either an ensemble classifier or a support vector machine. The scheme can work in two modes, the single filter mode using 9 features, and the multi-filter mode using 639 features. We compared the performance of the proposed method, the SRM and the maxSRMd2. The maxSRMd2 is the improved version of the SRM. The simulated results show that the proposed method that worked in the multi-filter mode was about 10% more accurate than the SRM and maxSRMd2 when the data were globally normalized, and had similar performance with the SRM and maxSRMd2 when the data were locally normalized.     

高性能模糊控制裹包机的感应电动机驱动系统的设计与实现

针对接缝式裹包机的交流调速系统控制精度较差的问题,提出了具有模糊控制器的有限周期控制的感应电动机驱动.由于转矩和磁通是由有限周期控制技术调节,能达到极快转矩响应.将模糊控制器应用于速度控制反馈环节中,使该驱动系统具有高自适应能力,且对参数和工作条件改变是非常的不灵敏.