Position Sensorless Brushless Dc Motor Speed Control System

Since science and technology change with each passing day, the high performance MCU and digital signal processors (DSP) have made great development at full speed and their cost-performance ratio have been rising constantly. The high performance MCU and DSP have already been applied to the Brushless DC Motor (BLDCM) speed-variable system. BLDCM has good mechanical characteristic and wide range of speed-variable and overcomes the shortcomings generated by the existence of mechanical commutator in conventional Brush DC Motor so that BLDCM has been widely used in the all fields of national economy. The use of sensorless control reduces the size of BLDCM, lowers its costs and reinforces its interference immunity, thereby widening its application areas. As a consequence, the research on position-sensorless control for BLDCM has been a hot spot all along in recent years.This thesis designs a speed-variable system for Permanent Magnet BLDCM with no sensor. Based on Sunplus high performance 16-bit MCU SPMC75F2313A, this system detects the rotor position by using the method of back electromotive force (EMF) to implement the control for position-sensorless BLDCM.At the beginning of this thesis, the development and status of BLDCM and its control is introduced. The basic structure, the operational principle and characteristics of BLDCM is also illustrated. Then this thesis discusses the control for sensorless BLDCM and decides to use the method of back-EMF to detect the rotor position based on analyzing the advantages and disadvantages of various control methods. Afterwards, the method of back-EMF zero crossing point and the confirming of commutation point is explained in detail.In the part of design for hardware, the structure is introduced which includes the MCU main control module and the IPM inverter module. The MCU main control module whose core is Sunplus SPMC75F2313A generates the PWM drive signal for motor and harmonizes the whole control system. EPM inverter module is in charge of power-invert and power supply, which include EMI filter and commutator circuits, switching power circuits (using TOP233Y), IPM inverter and IPM drive circuits (using FSBB20CH60), back-EMF detecting circuits, and high voltage and drive current circuits. The design for main circuits and the selection of important component is illustrated fully and clearly.The software and hardware of control scheme is debugged by μ'nSP IDE ofSunplus. The flowcharts of main routine and interrupt service subroutine are also shown.In the end of this thesis, the control scheme is verified validity by the analyzing the experimental waveforms. The conclusion part of this paper presents the scarcity and limitation of the system and shows the direction for future research work.