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Research on the EMC and Cogging Torque of a Small Moment Gyroscope

Author: LiGuoZhong
Tutor: ShaoKeRan
School: Huazhong University of Science and Technology
Course: Motor and electrical
Keywords: Electromagnetic compatibility Inductance model Cogging torque Artificial neural network model
CLC: TN03
Type: Master's thesis
Year: 2011
Downloads: 41
Quote: 0
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Abstract

With the wide application of the electromagnetic equipment, the pollution caused by electromagnetic is very serious. We are also facing the problem of coexist with the electromagnetic equipment and nature. The energy people use on the research on the electromagnetic compatibility and electromagnetic interference is increasing, and the EMC problem of modern electromagnetic equipment has become one of the questions that the electromagnetic device designers have to consider. In this paper, we consider the EMC problem of a small moment gyroscope. In this small moment gyroscope, the structure is compact, the internal electromagnetic environment is complex, the wires of the signals for control motor and current for motor’s power supply are fixed together, and the electromagnetic interference exists between each other. The main work of the paper is to analyze the electromagnetic interference between these wires. The electromagnetic interferences between the wires are generally classified into two kinds, radiation and conduction. Because the insulation among the wires is perfect and the transmission interference is very small, we mainly concern the radiated interference between the wires. To analyze the radiated interference between the wires, we establish the inductance model and the current model. With these models, we can calculate the induction emf on the wires, and then get the mutual interference of the wires.Because some current waveform of the wires is irregular, we cannot directly get the function of current changing with time. Instead we can only get a series of dots through the experimental method. To establish the current model, we have to use the function fitting. This paper used a BP artificial neural network to fit the current function, analyzes 3-spline interpolation, BP neural network and RBF neural network three fitting methods, and use this three methods to fit the sine function and the current function, compares the advantages and disadvantages of these three fitting methods.Since the high performance energy density and the high coercive force permanent magnetic materials have been found, the application scope of permanent magnet motor has been expanding unceasingly. Brushless dc permanent magnet motor has many advantages, such as good start-up performance, wide working speed range, good speed regulation performance, small volume, simple structure, high efficiency, low noise and so on. Thus brushless dc permanent magnet motor has been widely used. However, the brushless dc permanent magnet motor inevitably has the faults of torque ripple that main permanent magnet motor also have, and the existence of the cogging torque is the main reason the torque ripple. At present, many researches have been applied to find the method of decreasing the cogging torque of permanent magnet motor. Based on the empirical formula and the previous works, this paper introduces several methods of decreasing the cogging torque. Basis on finite element commercial software-ANSYS, we analyzed cores grooving method, changed extremely arc width method and reduce slit width method, verified the performance of these three methods in reducing the cogging torque, and analyzed the existing problems with using these three methods.

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