| As a newly designed product, Brushless DC motor has gained great development in recent years. By means of power electronics circuit to control over commutation instead of traditional mechanical methods, Brushless DC motor has advantages of both Brush DC Motor and AC Asynchronous Motor and has been widely used, especially after the attachment of sensorless control.After make a comprehend view of the development and present situation of position detection techniques for Brushless DC motor, the dissertation discusses how to location the position of rotor by means of Back Electromagnetic Force (BEMF), which aims to analysis the compensation and possible error of motor position, as well as restrain the commutation torque ripple during commutation for the ideal BEMF waveform with 120° platform width. That is to say, the paper concentrates on how to decrease the commutation torque ripple.The thesis first expounds the basic components, running principles of Brushless DC Motor as well as the basic principles and methods of sensorless commutation detection based on back electromagnetic force (BEMF). Secondly the thesis gives a detail dissertation of the realization of motor position detection based on back electromagnetic force (BEMF) and it's error, then analysis of the commutation torque ripple during commutation in Chapter 3 and Chapter 4. Chapter 3 first discuss the algorithm of motor position detection based on back electromagnetic force (BEMF), and bring forward "Leading 90° commutation " to overcome the phase deviation caused by this method. Then discuss the rotor position error caused by armature reaction, calculate the phase angle, and brought forward the compensation measures. Chapter 4 explains the reasons for torque ripple during commutation and calculate its values, then bring forward the methods to reduce the torque ripple by delaying the on-off time. These two chapters have been proved by the simulation result of MATLAB/SIMULINK... |
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