Sayeed A. Mir

PI and fuzzy estimators for tuning the stator resistance in direct torque control of induction machines

Direct torque control (DTC) of induction machines uses the stator resistance of the machine for estimation of the stator flux. Variations of stator resistance due to changes in temperature or frequency make the operation of DTC difficult at low speeds. A method for the estimation of changes in stator resistance during the operation of the machine is presented. The estimation method is implemented using proportional-integral (PI) control and fuzzy logic control schemes. The estimators observe the machine stator current vector to detect the changes in stator resistance. The performance of the two methods are compared using simulation and experimental results. Results obtained have shown improvement in DTC at low speeds.

Fuzzy controller for inverter fed induction machines

A fuzzy logic controller for direct self-control of an induction machine is presented. A response faster than that of the conventional direct self-controller during startup and during a step change in torque is achieved. To improve the system performance at low speeds a fuzzy resistance estimator is proposed to eliminate the error due to the change in stator resistance. At constant flux and torque commands any change in stator resistance of the induction machines causes an error in stator current. This error is utilized by the fuzzy resistance estimator to correct the stato resistance used by the controller to match the machine resistance. Both fuzzy controller and fuzzy resistance estimator are simulated for a 3 hp induction motor. The simulation results demonstrate good performance.<<ETX>>

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.

Fuzzy implementation of direct self-control of induction machines

A system with fast torque response is very beneficial in applications where direct torque control is highly desirable. The response of direct self control is slower during start-up and during change in command torque. Fuzzy control is used for the implementation of direct self control to improve its slow response. Experimental implementation of the fuzzy logic controller was carried out to verify the behavior of the controller. The controller was implemented with a single board computer that uses a TMS320C14 DSP. The experimental results with fuzzy control are compared with those of the conventional direct self controller. The starting flux and torque response and the responses to step changes in command torque with fuzzy implementation showed a considerable improvement over the conventional control. The steady state response for both controllers are the same. >

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.

Controller-induced parasitic torque ripples in a PM synchronous motor

PM synchronous machines with a sinusoidal back EMF are ideally capable of torque-ripple-free operation. However, parasitic torque ripples can still be induced from motor design and controller implementation. This paper focuses on a systematic analysis of possible torque ripples in a PM synchronous machine drive resulting from limitations in the motor controller. It takes into account the effects of finite encoder resolution, controller CPU word length, current sensing errors and inverter PWM switching. Approaches for analyzing and calculating torque ripples from each of those sources have been developed. Characteristics of the various parasitic torque ripples are discussed. Experimental and simulation data to verify important results are also presented.

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 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.

Evaluation of acoustic noise and mode frequencies with design variations of switched reluctance machines

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 four-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 SRM is designed following the low-noise design guidelines. The other one, labeled as conventional SRM is designed following the conventional design methodology. The mode frequencies and noise pressure 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.