Iqbal Husain

Minimization of torque ripple in SRM drives

The torque pulsations in switched reluctance motors (SRMs) are relatively higher compared to sinusoidal machines due to the doubly salient structure of the motor. The magnetization pattern of the individual phases together with the T-i-/spl theta/ characteristics of the motor dictate the amount of torque ripple during operation. Both machine design and electronic control approaches have been used to minimize the torque ripple in SRMs. This paper presents an extensive review of the origin of torque ripple and the approaches adopted over the past decade to minimize the torque ripple. A hybrid torque-ripple-minimizing controller that incorporates the attractive features of some of the techniques developed in the past decade is presented along with simulation and experimental results.

Online Parameter Estimation and Adaptive Control of Permanent-Magnet Synchronous Machines

This paper focuses on the benefits of adaptive control for permanent-magnet synchronous machines; a novel method of online parameter estimation for such machines has been developed. Two recursive least square algorithm segments, a fast and a slow one, are uniquely combined in real time with rich enough data from the machine to estimate all four machine parameters instead of a subset of these. Simulation and experimental results demonstrate the effectiveness of the proposed method.

Torque ripple minimization in switched reluctance motors using adaptive fuzzy control

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.

Modeling, Simulation, and control of switched reluctance motor drives

This paper presents the modeling, simulation, and control aspects of four-quadrant switched reluctance motor (SRM) drives. The design of SRM drive systems must be focused on application-based appropriate control and engineering solutions needed to overcome the practical issues. A complex model is described for the physical motor simulation to incorporate the important dynamics of the SRM. A simpler, but quite accurate, model is presented for the SRM controller. Various practical limitations have been incorporated in the simulation model to make it closer to the experimental setup. The SRM control parameters are chosen based on torque-per-ampere maximization requirement. Experimental results for a 1.0-kW SRM obtained on a digital platform are presented along with useful guidelines for prototype implementation.

New modulation encoding techniques for indirect rotor position sensing in switched reluctance motors

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.<<ETX>>

Analytical Model for Predicting Noise and Vibration in Permanent-Magnet Synchronous Motors

This paper analyzes the noise and vibration in permanent-magnet synchronous motors (PMSMs). Electromagnetic forces have been identified as the main cause of noise and vibration in these machines, rather than the torque ripple and cogging torque. A procedure for calculating the magnetic forces on the stator teeth based on the 2-D finite-element (FE) method is presented first. An analytical model is then developed to predict the radial displacement along the stator teeth. The displacement calculations from the analytical model are validated with structural finite-element analysis (FEA) and experimental data. Finally, the radial displacement is converted into sound power level. Four different PMSM topologies, suitable for the electric power steering application, are compared for their performances with regard to noise and vibration.

Torque ripple minimization in switched reluctance motor drives by PWM current control

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.<<ETX>>

Unbalanced force calculation in switched-reluctance machines

This paper presents a detailed analytical model for computing the radial magnetic forces that arise in switched reluctance machines (SRMs). The model is general and includes iron saturation, displacements of the rotor from its center location, and arbitrary angular rotor positions. The force between an individual stator pole and its corresponding rotor pole is calculated. The model is used to calculate the unbalanced magnetic forces on the SRM rotor, due to the rotor being displaced from its center location, by calculating the difference in the radial magnetic forces on opposite stator poles. The calculation of the unbalanced magnetic rotor forces requires an especially accurate model for the radial magnetic forces since the unbalanced forces are the difference between the two large radial forces on opposite sides of the rotor. The side pull created by the unbalanced forces will stress the bearings of the motor. The detailed analytical model presented here will simplify the bearing system design and will be especially useful if less stiff magnetic bearings are being employed. Finite-element analysis is used to validate the detailed analytical model. This same model for calculating the radial magnetic forces can be used as the input to a calculation of stator yoke ovulation due to radial magnetic forces and of the resulting acoustical noise production.

Tuning the stator resistance of induction motors using artificial neural network

Tuning the stator resistance of induction motors is very important, especially when it is used to implement direct torque control (DTC) in which the stator resistance is a main parameter. In this paper, an artificial network (ANN) is used to accomplish tuning of the stator resistance of an induction motor. The parallel recursive prediction error and backpropagation training algorithms were used in training the neural network for the simulation and experimental results, respectively. The neural network used to tune the stator resistance was trained on-line, making the DTC strategy more robust and accurate. Simulation results are presented for three different neural-network configurations showing the efficiency of the tuning process. Experimental results were obtained for one of the three neural-network configurations. Both simulation and experimental results showed that the ANN have tuned the stator resistance in the controller to track actual resistance of the machine.

Energy-efficient C-dump converters for switched reluctance motors

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 some of the switching devices in the proposed converters are reduced to the supply voltage (V/sub dc/) level compared to 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 requirements, and allow the motor phase current to freewheel during chopping mode. Simulation and experimental results of the converters are presented and discussed.