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.     

Young's modulus for laminated machine structures with particular reference to switched reluctance motor vibrations

The switched reluctance motor (SRM) has a disadvantage of higher acoustic noise, caused by stator vibrations. Techniques for noise reduction require knowledge of the modal frequencies, which depend on mechanical shapes and dimensions as well as material properties, for example, Young's modulus, Poisson's ratio, mass density, etc. It is found that the generally accepted value of Young's modulus is not valid for a machine with laminations and no frame. This paper introduces a simple and nondestructive method for the measurement of Young's modulus; it is then used in a finite-element (FE) program to determine the resonant frequencies of SRM stator vibration. The effects of mass density and Poisson's ratios are also discussed. The FE results are validated by vibration tests, which show good accuracy.     

Switched reluctance and permanent magnet brushless motors in highly dynamic situations: a comparison in the context of electric brakes

Electromechanical brake (EMB) systems offer the potential for enhanced vehicle control while simplifying the car assembly as well as recycling process. This article offers a comparison of two motor technologies, switched reluctance (SR) and permanent magnet (PM) brushless, motor in highly dynamic situations, in all four quadrants of their torque-speed operating regions, for an EMB application and also describes the motor designs and their static characteristics, before examining in depth their dynamic behavior, in particular special control adaptations to enable the SR motor to reverse rapidly when needed. A 20% longer SR motor provided overall similar dynamic performance, but only if the SR motor is fitted with a speed limit. A method to choose such a speed limit was developed, and the software algorithm implementation was found to be simple and successful.     

Prediction of electromagnetic forces and vibrations in SRMs operating at steady-state and transient speeds

Although some research has been conducted on vibrations in switched reluctance motors (SRMs), the response during transients, which may occur during sudden load changes or braking, has not received much investigation. In this paper, a simulation model to predict the transient vibration of SRMs is developed. The vibration prediction model is built based on the detailed normal force versus phase current and rotor position lookup table using finite-element calculations. The model is then verified by a running motor test, which shows acceptable accuracy. The results reveal that there are abundant harmonics of transient force during transients and, thus, resonance may be excited. This model allows the possibility of improved design of SRMs from a vibration and acoustic noise point of view.     

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 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 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 offline to determine the optimum firing angles for achieving highest drive efficiency with lower torque ripple in a 102-kW switched reluctance motor 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 (SR) 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, for short and open circuits, in the SR 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 the switch short circuit for which new results are presented.     

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.     

Vibration prediction in switched reluctance motors with transfer function identification from shaker and force hammer tests

A vibration prediction model for the switched reluctance motor is constructed in this paper. Shaker and force hammer tests for vibration measurement are used for measuring crucial parameters like modal frequency and damping ratio for the transfer function. A detailed lookup table of normal force versus phase current and rotor angle is constructed based on finite-element calculations. The model is then verified by experiments, with acceptable accuracy.     

Low-vibration design of switched reluctance motors for automotive applications using modal analysis

The search for low-noise switched reluctance motor designs has encouraged this research to focus on the effects of different lamination shapes on vibration. Five different shapes are considered, with one emerging as the best candidate for the 12/8-pole combination considered. The implications of using different phase numbers in the design are also explored from a vibration and noise point of view. A prototype motor is manufactured and used for a force hammer test. The test result validates the finite-element calculations of resonant frequencies.     

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 operating in dynamic modes 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-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