Avoki M. Omekanda

Robust torque and torque-per-inertia optimization of a switched reluctance motor using the Taguchi methods

This paper presents the use of Taguchi methods in optimizing a switched reluctance motor (SRM) for applications requiring fast actuation. In these applications, the SRM is designed to provide a high electromagnetic torque-to-inertia ratio required for high rates of mechanical acceleration. This is accomplished using two simultaneous robust optimizations of an SRM, namely: 1) an optimization of the motor torque and 2) an optimization of the torque per inertia (mechanical acceleration). The Taguchi two-step optimization method and the zero-point-proportional dynamic response were used successfully in the double optimization. Two orthogonal arrays were used to lead the design of experiments (DOE). Finite-element analysis was used to compute the performance of the motor designs generated by the Taguchi DOE.

Four-quadrant and zero-speed sensorless control of a switched reluctance motor

A four-quadrant sensorless controller for switched reluctance motor (SRM) drives is presented in this paper. The drive system with appropriate turn-on and turn-off angles for each operating quadrant delivers excellent dynamic performance over a wide speed range including zero speed. The problems associated with practical implementation especially at low and zero speeds have been addressed and overcome with engineering solutions. Experimental results for a 1-kW SRM obtained on a dSPACE-based system are presented along with useful guidelines for practical implementation.

Winding short circuits in the switched reluctance drive

The switched reluctance drive is known to be fault tolerant, but it is not fault free. This paper takes an in-depth look at winding short circuits in this particular machine. Modeling and testing complement a theoretical analysis. Two cases need to be distinguished, one where a complete pole is shorted, and one where a few turns are shorted. Pole short circuits lead to torque reduction that can be easily compensated for with increased current. With few turns shorted, the impact on overall torque may actually be negligible, however, significant currents may circulate through the shorted turns, the worst case being with a single turn shorted with a zero resistance. These results are discussed with a view toward possible remediation schemes aside from simply turning off the faulted phase.

A new technique for multidimensional performance optimization of switched reluctance motors for vehicle propulsion

This paper presents a new and simple search technique to determine the optimum control parameters, such as turn-on and turn-off angles, current set level, etc., of a switched reluctance motor drive. Thanks to this new technique, several drive performance quantities such as efficiencies, torque ripple, energy consumption, torque per ampere, etc., can be optimized simultaneously over the entire torque- or power-speed operation range of the drive. In prior art work, these performance quantities were sequentially optimized, one at a time. This despite reported evidence that improving one performance quantity, such as efficiency, can have a negative impact on others, such as torque ripple. The technique was successfully used off-line to determine the optimum firing angles for achieving highest drive efficiency with lower torque ripple in a 102-kW SRM drive intended for electric vehicle propulsion. The performance prediction and test results are found in good correlation.

Classification and remediation of electrical faults in the switched reluctance drive

The switched reluctance drive is known to be fault tolerant, but it is not fault free. The goals of this study are the systematic classification of all electrical faults, short-and open-circuits, in the switched reluctance drive (excluding the controller itself), and the investigation of fault patterns and possible remediation. Each situation is analyzed via finite element analysis, and/or experiments. The transient effects during the faults are described. Possible remediation schemes other than disabling the faulted phase are explored. There is a particular focus on switch short-circuit for which new results are presented.

A new technique for multi-dimensional performance optimization of switched reluctance motors for vehicle propulsion

This paper presents a new and simple search technique to determine the optimum control parameters, such as turn-on and turn-off angles, current set level, etc., of a switched reluctance motor drive. Thanks to this new technique, several drive performance quantities such as efficiencies, torque ripple, energy consumption, torque per ampere, etc., can be optimized simultaneously over the entire torque- or power-speed operation range of the drive. In prior art work, these performance quantities were sequentially optimized, one at a time. This despite reported evidence that improving one performance quantity, such as efficiency, can have a negative impact on others, such as torque ripple. The technique was successfully used off-line to determine the optimum firing angles for achieving highest drive efficiency with lower torque ripple in a 102-kW SRM drive intended for electric vehicle propulsion. The performance prediction and test results are found in good correlation.

Four-quadrant control of a switched reluctance motor for a highly dynamic actuator load

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.

Four-quadrant pulse injection and sliding mode observer based sensorless operation of a switched reluctance machine over entire speed range including zero speed

The objective of this paper is to present a sensorless position estimation technique for switched reluctance machines (SRM) operating in constant dynamic mode over a wide speed range including zero speed. The technique combines two different methods to deliver high resolution position information over the wide speed range. At zero and low speeds, a voltage pulse injection method is used to estimate the rotor position in all four quadrants. For higher speeds, a sliding mode observer (SMO) based algorithm is used and combined to work with the low speed algorithm. Experimental results demonstrate the effectiveness of this new combined technique that has four-quadrant operation capability.

Robust torque- and torque-per-inertia optimization of a switched reluctance motor using the Taguchi methods

This paper presents the use of Taguchi methods for optimizing a switched reluctance motor (SRM) for applications requiring fast actuation. In these applications, the SRM is designed to provide a high electromagnetic torque to inertia ratio required for high rates of mechanical acceleration. This is accomplished through two simultaneous robust optimizations of a switched reluctance motor; that is, an optimization of the motor torque and an optimization of the torque-per-inertia (mechanical acceleration). The Taguchi two-step optimization method as well as the zero-point-proportional dynamic response were used successfully in the double optimization. Two orthogonal arrays (OA) were used to lead the design of experiments (DOE). Finite element analysis (FEA) was used to compute the performance of the motor designs generated by the Taguchi DOE

Acoustic Noise of Switched Reluctance and Permanent Magnet Motors: A Comparison in the Context of Electric Brakes

It is held as fact that Permanent Magnet (PM) brushless motors are less noisy than Switched Reluctance (SR) motors, and many methods have been published to reduce the noise of SR drives. This paper provides a systematic experimental comparison of both drives, and of proposed noise- mitigation strategies, in the context of a specific mass-market application: Automotive Electro Mechanical Brakes (EMB). The two motors were designed to fit into the same envelope and to produce similar dynamic performance for the brake system. Sound pressure levels produced by the two motors at key torque-speed points were measured through dynamometer tests under identical conditions. The influence of the hysteresis current and PWM control methods on the acoustic noise was also studied. The acoustic noise was then measured with the EMB systems assembled with the PM and SR motors. Though the measured acoustic noise of the SR motor with dynamometer tests was higher compared to that of the PM motor, the acoustic noise levels of the two EMB systems were found to be similar with only a slight advantage to the PM based system.