Design Of Control System For BLDC Motor In Smart Home Products

With the rise of smart home products in recent years,related technologies of electric motors as their core power supply units have also become research hotspots.This paper is based on the use environment and use characteristics of smart home products,namely low noise,low energy consumption,small size and high safety.A brushless DC motor(BLDC)is selected as its power unit.Based on the unattended characteristics of smart home,the control algorithm of brushless DC motor is optimized,and the scheme is verified by simulation and implementation.In order to design a more reasonable control scheme,this paper briefly analyzes the structure and principle of the brushless DC motor.The brushless DC motor uses an AC motor body internally,so the inverter bridge circuit is required to perform DC power conversion AC power.However,considering that the brushless DC motor is often used in fixed-frequency AC mains,a rectifier circuit is required at the front end of the inverter.Through the stepwise research on the three modules of rectifier circuit,inverter circuit and control circuit,this paper analyzes the operating principle of brushless DC motor and further compares the sine wave motor and square wave motor which belong to the brushless DC motor.Similarities and differences,the motor type for a smart home product is a square wave brushless DC motor.Before the detailed design of the control algorithm,this paper analyzes the brushless DC motor and obtains the key variables related to speed and torque control.The control algorithm design can be divided into three parts,namely PI speed control part,PWM signal control part and gating signal calculation part.Based on the above control algorithm,this paper optimizes the basic control scheme by proposing a rotor position detection technology at low speed.The optimized design is carried out from both the start and brake directions.Considering the unattended nature of smart homes,the motor may start under a certain load.Therefore,this paper combines pre-positioning start and inductance detection to ensure that the motor can be started quickly without load,and can be successfully started under load conditions,improving the ability of the motor to start successfully.On the other hand,in view of the occurrence of an emergency,the motor should have the ability to brake quickly to reduce damage.Therefore,this paper designs a dual-mode braking scheme by combining reverse braking and short-circuit braking,which improves the braking efficiency of the motor and prevents the motor from reversing.The experiment was carried out by MATLAB/Simulink software.The system simulation mainly designed four modules,namely PI speed controller module;threephase inverter module;detection module and gate signal module.Through the analysis of the simulation program,the hardware implementation of the control system is designed to verify the effect of the optimized control scheme.The hardware-implemented control program design can be divided into four sub-programs,namely the main control program;the startup sub-program;the interrupt update sub-routine;and the brake sub-program.Through the program verification,the startup scheme designed in this paper can complete the load start situation.The braking scheme designed in this paper can improve the braking efficiency and reduce the braking time from 1.1 seconds to 0.7 seconds.