Research On Sensorless Control Algorithm Of Brushless DC Motors

In response to the national call for carbon peaking and carbon neutrality to save energy and reduce emissions,brushless DC motors will be more widely used in the industry due to their high watt density and outstanding efficiency.The best control of the brushless DC motor requires the use of its rotor angle information.In household appliances and power tool products,Hall sensors are usually installed in the brushless DC motor to obtain the position information of the motor,which increases the cost of the motor,and In the harsh environment of high temperature or high humidity,the Hall sensors is easily broken,which reduces the reliability of the system.Therefore,the sensorless control technology of the brushless DC motor can reduce the system cost,improve the reliability,and expand the application scope of the brushless DC motor.Compared with the square wave control technology,the vector control technology of the brushless DC motor has the advantages of lower control noise and smaller torque fluctuation and vibration.However,due to its complex control algorithm,it requires high processor computing power,which limits its use in home appliances,power tools,etc.In recent years,with the rapid development of the domestic semiconductor industry,low-cost,high-performance MCUs have emerged one after another,expanding the application field of vector control technology.Based on the vector control of the sensorless brushless DC motor,this thesis deduces and simulates the sensorless control algorithm,builds an experimental platform to test and verify the effectiveness of the algorithm,and analyzes the error brought by the motor parameters inaccuracy to the rotor position observer and gave a solution.Mainly complete the following work:（1）Analyze the mathematical model of the brushless DC motor,and the derivation of the coordinate transformation of the model in the static coordinate system and the rotating coordinate system,analyze the vector control system of the brushless DC motor,and develop the controller of a surface-mounted brushless DC motor By using the vector control strategy with =0.（2）Derive the extended back EMF equation of the brushless DC motor,and design the PI-type extended back EMF observer of the motor in the rotating coordinate system,and obtain the speed and rotor position information of the motor by operation through the observer.The effectiveness of the observer is verified by simulink simulation.（3）For the theoretical and simulation analysis of the observer,build an experimental platform,design the major hardware circuit modules of the motor driver,write the electric vector control program and the observer algorithm in the MCU,and use a 1000 W garden tool low-voltage motor to verify the algorithm,and the angle observation effect is good under the working conditions of low speed,high speed and sudden load change.（4）Aiming at the problem that the motor parameter inaccuracy will affect the observer results,a method for off-line and on-line identification of motor inductance and resistance parameters is designed,and the correctness of the results is verified by simulation.