Search

A four-quadrant sensorless switched reluctance machine (SRM) controller has been developed using a model based on the Fourier series expansion. The sensorless controller combines two different methods both of which are based on the Fourier model. At zero and low speeds, a pulse injection position estimation method is used to estimate the rotor position in all four quadrants. At high speeds, a sliding mode observer (SMO) based position and speed estimation is used. The use of the SRM Fourier model in the sensorless algorithms provides position estimation with high degree of accuracy. Experimental evaluation demonstrated the superiority of the Fourier model over the models developed in previous research.

A novel invertible generalized flux/current switched reluctance machine (SRM) model based on the Fourier series expansion is presented. This model, derived from machine geometry and materials properties, is accurate enough to be used for actual machine representation, and can also be simplified for real time controller applications. Simulation and experimental results illustrate that the proposed modeling approach provides better representation of the SRM than other existing techniques

Rotor position information is critical to proper operation of a switched reluctance motor (SRM). In this paper two methods of indirect rotor position detection are presented that are compatible with alternative switching topologies. These methods are both based on amplitude modulation of an injected signal according to the phase inductance variation. An analysis of these methods along with experimental results is presented in this paper.

The development of sustainable, clean and efficient transportation systems is a critical factor for the improvement of overall air quality, and to reduce the nation's dependence on diminishing domestic resources and imported fuels. Transportation accounts for one-third of all energy use and carbon emissions in the US, primarily from personal vehicles, constituting one of the biggest challenges for reducing emissions of greenhouse gases. This paper presents the development issues for an innovative fuel cell electric vehicle infrastructure and bi-directional grid connection, derived from renewable and clean energy sources.

The concept of paramagnetic rotor bars to improve the starting performance of squirrel cage induction motors is presented in this paper. Although the induction machines are popular for their ruggedness and simplicity, their starting torque is low and the starting current is 5 to 8 times higher than the rated current. A simple solution to this problem is the introduction of new rotor-bar material with paramagnetic properties, which in turn improves the starting power factor due to enhanced skin effect. Relevant electromagnetic theory supporting this are presented in this paper. A computer simulation also produced expected results. A one horse power induction machine has been tested to verify the proposed methodology.

Supersonic mixing or in other words the mixing of two streams flowing at different speeds has been studied a lot in the past pertaining especially to the effect of high speed stream flow mixing with a slow stream. The various techniques developed have always had the drawback of high pressure losses sustained along-with other losses to obtain optimum mixing between the two streams. It is a continuing source of study to understand the underlying physics inherent in this phenomena. Confined Supersonic Mixing is beset with complex phenomena that usually consist of the following - shear-layer formation, shear/boundary-layer interaction, shock/shear-layer interaction etc. which makes the study of such phenomena a complex task. The aim of this work is to further the understanding of the effects pertaining to confined mixing of different speeds i.e. one high speed and one slow speed or in other words a supersonic and a subsonic speed stream. Further enhancing this mixing process is the ultimate aim of the present work. This is done with the help of techniques to force stream mixing in the shortest distance possible with minimum pressure loss. Every active technique would be actually giving rise to a pressure loss because of the intrusive nature of the technique involved. A compromise between the enhancement of mixing obtained to the maximum acceptable pressure loss is the aim of this work. This is carried out using the wedge and the wedge/cavity combination which is in itself an active/passive source of introducing further complexity to the problem to be studied. The study is carried out both experimentally and numerically with the help of various techniques and a comparison of the two methods gives us an insight into the interaction that is characteristic of this process. The enhancement of the mixing process between the two streams with acceptable supersonic pressure recovery is the main result of this work. This would further our understanding of the complex processes taking place in this phenomena.

The steady two-dimensional stagnation point flow of a non-Newtonian Walters' B' fluid with slip is studied. The fluid impinges on the wall either orthogonally or obliquely. A finite difference technique is employed to obtain solutions.

A design methodology is described here for switched reluctance machines (SRM) to obtain an optimal thermal response. The method optimizes the SRM design to meet the specific maximum power, torque and speed range requirements, while minimizing temperature, envelop dimension and noise and maximizing torque density. Based on the geometrical dimensions and parameters, a lumped parameter model is used to predict the steady state and transient thermal characteristics of this motor. The effect of various parameters and design ratios on the maximum temperature rise of the machine is studied using the model. The lumped parameter model results are compared with temperature predictions from finite element analysis for validation.

The paper presents an analytical and experimental evaluation of observer-based methods for estimating the position and speed for switched reluctance motor (SRM) drives. Two observers, the sliding mode observer (SMO) and the standard state observer (SSO), are both found to provide good position and speed estimations. The resolution and reliability of the position estimation scheme are analyzed in detail. Error analysis is carried out under various operating conditions using estimated position and speed in the controller. The results demonstrate the applicability of observer-based sensorless controller for SRM drives.

A four-quadrant controller for switched reluctance motor (SRM) drives with optimal turn-on and turn-off angles for each operating quadrant is presented in this paper. The firing angles are chosen to maximize the average torque produced by the motor, which requires the optimization of the area of the energy conversion loop. The four-quadrant SR controller developed with the chosen optimization criterion gives fast motoring response as well as fast braking response. The underlying contribution of this paper is the development and solution of an optimal control problem to provide the best control strategies. The paper also provides the specific guideline to switch the firing angle position when the motor operation changes from one quadrant to another. The developed four-quadrant controller has been applied to control the linear displacement of a highly dynamic actuator load.

This paper presents an analytical method for calculating the radial force and predicting the acoustic noise in switched reluctance machines (SRMs). The main source of acoustic noise in an SRM is the radial magnetic force inducing resonant vibration with circumferential mode shapes of the stator. An analytical relationship between radial force and radial vibration is determined, which can be used to predict the noise power level at the frequency of operation. The vibration and sound are functions of machine dimensions, material properties, and rotational speed. The knowledge of the circumferential mode shapes of vibration, the natural mode frequencies of the stator, and the frequency spectrum of the radial magnetic force can be effectively utilized to design SRMs with minimal noise through geometrical design variations. The effect of the number of stator and rotor poles on acoustic noise can also be analyzed with the model presented in this paper. Magnetodynamic simulation by finite-element analysis software has also been carried out to verify the calculation of radial force using the proposed analytical model.

Rotor speed and position estimations in permanent magnet synchronous motors (PMSM) suffer from accuracy due to variations of machine parameters such as torque constant, stator resistance and inductance, especially at low speeds. Also, conventional linear estimators are not adaptive. In this paper, two neural network-based model reference adaptive systems (MRAS) for position and speed estimation are presented for PMSM drives. The first network estimates the rotor speed and adapts online to any change in stator resistance. The second network estimates the rotor position and adapts online for any changes in the torque constant. A q-axis model for stator inductance based on current is used. In both cases, the MRAS adjusts the neural weights to give optimal performance over a wide speed range. Simulation results showed the estimation adjusts well to changes in the motor operating points.

The switched reluctance machine (SRM) is uniquely reliable for its fault tolerance capabilities. More has been discussed in the literature about fault tolerance of switched reluctance machine than has actually been analyzed. This paper presents a model for various fault analyses which is general enough to be applied to any type of SRM drive as an evaluation tool. The post-fault performance characteristics of the SRM are presented here in terms of torque and speed ripples to show its fault-tolerance capabilities.

This paper describes a new method of indirect rotor position sensing for switched reluctance motor (SRM) drives. The principle is based on measuring the mutually induced voltage in an inactive phase which is either adjacent or opposite to the energized phase of an SRM. The mutual voltage in the "off" phase, induced due to the current in the active phase, varies significantly as the rotor, corresponding to the energized stator, moves from its unaligned position towards complete alignment. This mutually induced voltage variation is captured by a simple electronic circuit and then processed in a microcontroller to determine the commutation instants, thereby eliminating the need for direct rotor position sensors in an SRM. Successful operation of a four-phase SRM drive has been demonstrated in the laboratory using the mutual voltage (MV) technique of indirect rotor position sensing. The theoretical aspects of mutually induced voltages in an SRM and the relevant experimental results are presented in this paper. >

Two novel indirect switched reluctance motor (SRM) rotor position (RP) sensing schemes based on winding current amplitude and phase modulation are presented. An off phase is supplied with a stiff sinusoidal carrier voltage from the sensing circuit to be modulated by an RP dependent phase inductance function. The modulated signal is decoded to obtain the information signal and is calibrated to obtain the RP angle continuously. A combination of phase modulation and amplitude modulation encoder techniques was designed and tested on a 5 hp three-phased 6-4 SRM over a wide range of speed. The position detection scheme kept excellent track of the rotor angle continuously under both load and no-load conditions. This scheme is extremely robust to switching noise present in the sensing phase due to mutually induced voltages. >

The authors review the SRM (switched reluctance motor) drive technology. They present some of the simplified technology which has been developed in the lab and elsewhere. The emphasis is on elimination of discrete rotor position sensors and discrete current sensors. The theoretical apsects of the different methods of position sensing and the relevant experimental results are also presented. >

A sliding mode control strategy is proposed for a third order Cuk converter. Conventional switching surfaces for DC-DC converters of order greater than two contain one state variable set equal to a constant. This paper analyzes switching surfaces that are a linear combination of up to three state variables. These switching surfaces allow much more flexibility in controlling the output voltage and produce a response with small overshoot and a reduced reaching time period, as compared to the conventional surfaces used in earlier studies. Simulation and experimental results are reported. The results verify that the output voltage can be controlled and maintained at the desired level using the sliding mode control schemes developed.

This paper describes the efficiency and performance analysis of a dual-decay converter for star-connected switched reluctance motor drives in low-voltage applications. Proper turn-on and turn-off time are proposed in order to improve the efficiency. Drive performance is analyzed and the selection procedure of the appropriate dump resistor is discussed. The results are compared with those of the suppression resistor converter. Experimental results are presented to verify the capabilities of the dual-decay converter. >

In this paper a second order sliding mode observer is proposed for state estimation in a switched reluctance machine (SRM). The estimated rotor position obtained from the observer is used for the electronic commutation of the machine phases. The proposed sliding mode observer provides a robust method of indirect rotor position sensing using terminal measurements of phase voltage and currents. The paper includes detailed simulations of a closed loop controller based on the proposed sliding mode observer. >

Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives, which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance. >

It is noted that rotor position information is essential for the operation of the switched reluctance motor (SRM) drive for generating the phase current switching signals. The accuracy of this position information dictates the efficiency and smoothness of the drive. The authors present the results of an accuracy analysis of a novel indirect SRM position sensing scheme, the FM (frequency modulated) encoder. The technique can be used to detect the rotor position with an error of 1 degrees electrical. The analysis breaks down the position error to its fundamental sources in the position sensing system. The same basic approach can be used to evaluate other SRM rotor position sensing schemes. The results are helpful in comparing the various sensing schemes as well as focusing improvement efforts on the right component in the system. >

The switched reluctance motor can be viable for various applications in the hostile environment of the automotive. The absence of shoot-through problems and simple unipolar power converter requirements give SRMs a definite edge over other type of motors. The absence of cogging torque in SRM is also a definite plus. A simple SRM drive system that can be used in automotive applications is presented. An indirect position sensing scheme that eliminates the need for discrete position sensors is the basis of this drive system. A frequency modulated (FM) encoder is developed to convert the inductance variation into a frequency encoded signal which is further processed in a microcontroller to generate the converter gating pulses. >

The inverse dual converter (IDC), suitable for high-power DC-DC conversion applications, is presented. The IDC is a voltage source converter with an AC link and has been derived from an inductor converter bridge. This capacitor commutated converter is capable of continuous voltage step-up or step-down control over a wide range without the need of a transformer. In addition to high-frequency switching the converter is characterized by soft switching techniques, reducing constraints on the ratings of the switches. The average model developed with the help of gyrator theory provides sufficient information for control strategies and design considerations. The results of gyrator modeling and computer simulation are compared with experimental results obtained from a prototype IDC. >

AC/DC switching converters are highly nonlinear. Therefore they draw a nonsinusoidal current with a low power factor. Conventional linear controllers used for power factor correction of these converters do not offer a wide dynamic range. Neural network controllers (NNC) are nonlinear, which learn, adapt and provide wider dynamic range. This paper presents the use of NNCs in power factor correction of AC/DC switching converters. The NNC replaces the conventional current mode controller (CMC) of the high power factor AC/DC converter. Both the direct and indirect NN control schemes are used. Comparisons are made between the simulation results of the NNC and those of the CMC under normal and dynamic operations. The results demonstrate that NNCs can effectively control the high power factor AC/DC switching converter. The NNC performance is comparable, and in some cases better than the CMC. The NN controllers perform better with parameter variations compared to the fixed gain CMC. The fault tolerance capability of the NNC shows excellent results.

A neural network based estimator for torque constant and stator resistance in permanent magnet synchronous motors (PMSM) is presented. The neural weights are initially chosen randomly and a model reference algorithm adjusts those weights to give the optimum estimations. The q-axis inductance is modeled offline according to q-axis stator current. The neural network estimator is able to track the varying parameters quite accurately at different speeds with consistent performance. The neural network parameter estimator has been applied to slot and flux linkage torque ripple minimization of the PMSM. The drive system is insensitive to these parameter changes. Simulation results justifying the claim are presented.

A self-tuning controller for switched reluctance machines is presented. A torque ripple minimizing controller is implemented with the on-line system identification and adaptation technique. The controller uses a nonlinear model of the machine which is updated on-line using a recursive identification algorithm. The real-time approach improves the overall robustness of the system. Experimental results are presented to validate the self-tuning algorithm.

A torque-ripple minimization technique for switched reluctance motors (SRMs) is presented. The technique is particularly suitable for applications requiring wide speed range of operation. A new, simple, yet efficient commutation strategy is proposed. The commutation algorithm is speed dependent and uses a real-time approach instead of precalculated stored data. The model used for the SRM in the controller can also be updated in real time. Simulation and experimental results verify the feasibility of implementing the proposed control algorithm in real time.

A nonlinear model with on-line parameter estimation using recursive identification for switched reluctance motors is presented. The model is robust towards parameter variations in the motor or any system disturbances. The parameters of the model are adjusted to account for errors in rotor position, which allows the use of crude inexpensive position sensors. The proposed modeling approach allows self-tuning of SRMs in a production unit. The model has been tested through simulation and experimentation, which demonstrated the accuracy of estimation of the model.

An adaptive fuzzy control scheme for torque ripple minimization of switched reluctance machines (SRM) is presented. The fuzzy parameters are initially chosen randomly and then adjusted to optimize the control. The controller produces smooth torque upto the motor base speed. The torque is generated over the maximum positive torque producing region of a phase. This increases the torque density and avoids high current peaks. The controller is robust towards errors in the rotor position information which means inexpensive crude position sensors can be used. Detailed simulation and experimental results are presented. The controller shows good response in both cases.

In this paper, a methodical development of DC-DC converter topologies from the basic three-terminal models are discussed. Principle of operation and circuit analysis of soft-switching high-power, zero-voltage switching (ZVS) and zero-current switching (ZCS) DC-DC converters are presented.

A modification of the (n+1) switch power converter topology for star-connected switched reluctance motor drive applications is proposed, which is suitable for low speed as well as high speed operation. A freewheeling circuit with a dual time constant has been designed to reduce the current tail in decreasing inductance region, which reduces the negative torque and improves the system efficiency. The different modes of operation of the power converter is discussed, and a comparison is made with the (n+1) switch power converter topology. >

The stator mode frequency as well as the intensity of acoustic-noise generated by magnetic radial force, is related to the geometry, configuration and material properties of the switched reluctance machine (SRM). Two different 4-phase, 8/6 SRMs with similar specifications, torque-speed requirements and envelope dimensions have been designed and built for experiments related to noise intensity and stator mode frequencies. One of these two SRMs, labeled as low-noise SRMs is designed following the low-noise design guidelines. The other one, labeled as a conventional SRM is designed following the conventional design methodology. The mode frequencies and noise power levels for both the SRMs have been calculated using the analytical-models. Acoustic-noise data collected from a test bench are analyzed to correlate the experimental and theoretical results.

A switched reluctance motor (SRM) drive optimized to achieve sensorless operation over wide-speed range with lowered torque-ripple is presented in this paper. Wide-speed range is obtained by phase advancing between two extreme critical rotor angles; lowered torque-ripple is obtained by effective torque sharing of adjacent phases; and sensorless operation is achieved through a sliding-mode observer (SMO) based algorithm. The research reveals the method of determination of critical rotor angles from machine geometry and material properties and suggests the design considerations to optimize the control parameters. The research also defines the phase advancing strategy between the critical rotor angles and the torque sharing mechanism by introducing a natural commutation period. The integrated SRM drive with simulation and experimental results using TMS320C30 DSP are presented for verification.

Stator vibrations due to magnetic radial force are the dominant source of acoustic noise in the switched reluctance machine (SRM). The intensity of this noise is related to stator mode frequencies, operating speed and magnetomotive force (amp-turns) of the machine. The higher the dominant mode frequencies, the lower is the noise intensity. The factors related to noise generation in the SRM are functions of machine geometry, configuration and material properties. A set of guidelines to select configuration, geometry, internal dimensions and stator pole shapes to reduce acoustic noise is presented with supporting simulations. The proposed design considerations have been applied to a 4-phase, 8/6 (1-repetition) and a 3-phase, 12/8 (2-repetition) 1.0 kW SRM with low acoustic noise requirement. The static and magneto-dynamic finite element analysis (FEA) have been made to compare the results of the two low-noise SRM designs.

Switched reluctance motor (SRM) drives can be used in all types of adjustable speed applications, including high performance servo drives. An important technique used for obtaining high performance from an SRM drive is determination of rotor position. A shaft position transducer is often used for this purpose. However, it is highly desirable to employ indirect position sensing methods which avoid using a transducer. This article reviews existing indirect position detection techniques such as waveform detection and model based estimators. Then, modulation encoding technique which presents a simple alternative to the mentioned methods is described. Various modulation techniques that can be used for position detection are discussed along with their advantages and disadvantages. Some special applications of SRM drives are also presented.

Two energy-efficient converter topologies, derived from the conventional C-dump converter, are proposed for switched reluctance motor (SRM) drives. The proposed topologies overcome the limitations of the conventional C-dump converter, and could reduce the overall cost of the SRM drive. The voltage ratings of the dump capacitor and the switching devices in the proposed converters are reduced to the supply voltage (V/sub dc/) level compared to being twice the supply voltage (2V/sub dc/) in the conventional C-dump converter. Also, the size of the dump inductor is considerably reduced. The converters have simple control that allows the motor phase current to freewheel during chopping mode. Simulation and experimental results of the converter are presented and discussed.

Switched reluctance machines (SRMs) are a prime candidate for aerospace starter/generators and various automotive applications. The choice of SRMs for the starter/generator application is driven largely by the perceived reliability and fault tolerance of the machine and its electronics. An analysis of the switched reluctance generator's (SRG) faults and excitation requirements is essential to utilize the full fault tolerance capability of the machine in this application. Thus, research has been undertaken to identify, analyze and simulate the various fault modes of the SRG. This research included an investigation of the generator's excitation requirements with and without faults. The investigation makes it possible to determine the size of the excitation source required during the initial build up of the generator's output voltage and under fault conditions. The SR machine, controller, EMI filter, excitation source, and load were all modeled and integrated into a Matlab-Simulink model in order to analyze the SR generator system.

The authors investigate the open-loop gyrator behavior of a class of DC-DC converters that are characterized by double bridges. If the switching frequency of the double bridge converter is high enough with respect to its natural frequencies, the converter can be viewed as a gyrator from its terminals. Unlike other gyrator modeling approaches for converters, the double bridge converters naturally behave as gyrators without any extra control circuits. >

This article presents an overview of electronic braking systems using SR (Switched Reluctance) machines. The advantages presented by this structure when compared to the conventional hydraulic systems are discussed. A justification for the choice of the SRM as a valid candidate is provided, with a detailed analysis of its control structure and performance. Experimental results obtained using a digital signal processor are also presented.