Research And Development On The Control System Of Single-phase BLDC Motor For Cordless Vacuum Cleaner

Compared with three-phase brushless DC motor,single-phase brushless DC motor has fewer applications,but in some cases,single-phase brushless DC motor has unique advantages.Compared with multiphase brushless DC motor,single-phase brushless DC motor has simpler mechanical structure and lower production cost,so it has a good application value in some products requiring lower motor control accuracy.This thesis designs a control system for a single-phase brushless DC motor for hand-held cordless vacuum cleaner,which is used as a fan in the vacuum cleaner according to the actual needs of vacuum cleaner enterprises.The subject requires that the control system can make the motor drive the blade to run stably at super high speed,the maximum speed is more than100,000 r/min,to provide strong suction for the vacuum cleaner;Motor speed grading is adjustable to meet the requirements of different working scenarios;Low vibration and noise during motor operation,improve user experience;The system can run safely and reliably,and stop the machine in time when any abnormal situation occurs.Based on the above requirements,the main research work of this thesis is as follows:Firstly,the working principle of permanent magnet single-phase brushless DC motor is analyzed.To solve the problem of starting dead point of single-phase motor,the air gap of the motor is designed as an uneven structure,so that the motor has an eccentric torque when it is stationary,and the rotor can start successfully.The working principle of each component of single phase brushless dc motor is analyzed and the working process of single-phase brushless DC motor is studied.The simplified mathematical model of motor is derived to establish a theoretical basis for the formulation of motor control strategy.Secondly,the commutation strategy of single-phase brushless DC motor is studied and analyzed.The motor system designed in this topic has three speed modes,namely high speed mode,medium speed mode and low speed mode.According to different speed modes,different control strategies need to be adopted.In the high speed mode,because the traditional control mode of single-phase brushless DC motor can not meet the performance requirements of the high speed motor used in the cordless vacuum cleaner,this thesis proposes a control method that combines the advance commutation with the freewheeling zone,which makes the motor speed exceed 100000r/min.Aiming at the problem that the motor will have a large current peak when it is running in medium and low speed mode,a method was proposed to insert a short freewheeling zone in the winding conduction zone to smooth the current waveform and reduce the torque fluctuation when the motor is running.Thirdly,the hardware scheme of permanent magnet single-phase brushless DC motor is designed.Based on the functional requirements of the motor system,the overall design and chip selection of the hardware system are completed.According to the overall design of the hardware system,the power supply circuit,program download and reset circuit,H-bridge inverter circuit,current sampling circuit,Hall signal detection circuit,current amplification and overcurrent protection circuit and other circuit modules are designed to complete the development of the motor control system hardware circuit.Then,the software scheme of permanent magnet single-phase brushless DC motor is designed,and the software development of each functional module of the motor system is carried out.According to the characteristics of motor operation in high,medium and low speed modes,the corresponding electronic reversing flow is designed.Constant power is realized by fixing the conduction Angle and PI adjustment of the advance angle,so as to ensure that the motor system can maintain constant output power under the dynamic changes of voltage and load.In order to optimize the starting performance of the motor,the control mode of starting the motor with low duty cycle PWM is designed,so that the motor starts with low current and speed first.After the motor starts successfully and runs stably for a period of time,the control strategy is switched to a different speed mode.Finally,the experimental platform was built,and various tests were carried out on the designed motor system.Experiments are carried out on the control mode of PWM starting motor with low duty cycle,which proves that the starting mode can start the motor safely and reliably with small current.The constant power control strategy of the motor is tested,and it is proved that the motor can run stably at the designed constant power under various speed modes,and the constant power control effect is good.The designed motor system is installed in the vacuum cleaner,and the performance of the vacuum cleaner is tested.The experimental results show that the motor system studied in this thesis can provide strong suction for the vacuum cleaner when applied to the vacuum cleaner,and it’s performance has reached the commercial standards.