Control And Its Implementation Of Brushless DC Motor Without Position Seneor

DC motor has a better starting performance and good speed performance, brushed DC motor starting torque, speed mother’s line voltage changes linearly, high output efficiency, but there is a mechanical noise in the rotation, easy to produce a spark, the need for regular maintenance and other shortcomings. Brushless DC motor commutation electronically, without commutation brushes, high power density, long life, low electrical noise and mechanical noise, has recently become a hot research.Brushless DC motor, the rotor position information from the position sensor through a specific physical transformation, for converting the position information of the rotor into an electrical signal to the controller in order to achieve commutation, but this inevitably increases the motor size and the manufacturing, processing costs, while the installation position of the sensor have higher requirements; Especially in some special work environments such as high temperature, freezing, high humidity, corrosive environments, air pollution and vibration, high speed, etc.The position sensor reliability and safety will be greatly reduced, thereby directly affecting the operation of the motor. In these two factors to consider and weigh, research Brushless DC motor control to a certain necessity and inevitability. In these two factors to consider and weigh, research Brushless DC motor control to a certain necessity and inevitability.Thesis describes the background and the value and significance of the research selection of brushless DC motor control, the current domestic and international research status and future trends do further exploration to determine the objectives and requirements and design specifications of this project.Secondly, the paper focuses on the composition of the structure of brushless DC motor body and how it works, the establishment of a mathematical model and operating characteristics of the equation.Brushless DC motor rotor by the permanent magnet, the stator windings from, frame, etc., by conducting different power tube, so that the internal motor armature to form a rotating magnetic field of the permanent magnet rotating traction;Through analysis, the establishment of a physical model of a brushless DC motor, a list of its voltage equation, the back-EMF equation, speed equation current equation electromagnetic torque equation, mechanical equations of motion, and write the transfer function;Meanwhile thesis of brushless DC motor operating characteristics, focusing on the fundamental issues of the motor starting characteristics, operating characteristics, mechanical properties, speed characteristics and load characteristics were studied.Again, the paper describes the brushless DC motor control starter motor, the motor using electronic commutation replace brush commutation, detection and treatment using the back-EMF detection signal to obtain the equivalent rotor position, current and speed dual-loop control algorithm implementation and the five core issues, such as failure analysis and processing encountered during motor operation,Starter motor which uses "three-step" approach, using the back-EMF commutation zero crossing detection method, the speed detection by calculating two zero crossing intervals to determine the size of its speed, the current detected by the test sample resistance measurement of the current bus dual closed-loop control, the inner current loop, using the speed of outer ring, in the protection of the main design of the attempts to prevent the transfer, overcurrent, overheating and other measures.Finally, the paper used by the US Microchip microcontroller ds PIC33FJ16MC204 built hardware circuits. Experiments proved that the motor can run stable, fast start, wide speed range, speed stability, achieved without sensor control, to achieve the design requirements.