Design And Implementation Of FOC Control System For Sensorless Brushless DC Motor

BLDCM(Brushless DC motor),because of its high running speed and good reliability,does not generate sparks due to electronic commutation,and is currently widely used in different fields such as civil and military.The control technology of brushless DC motors without position sensor reduces the system hardware cost,simplifies the design,and allows the sensorless motor to be used in a high temperature and high humidity environment,improving the reliability of the motor operation and greatly expanding the brushless DC motor Scope of application.The sensorless control technology of the brushless DC motor can be divided into two parts: the sensorless start of the motor,the FOC(Field oriented control)control technology,the performance of the sensorless start and the detection accuracy for the rotor position in the FOC control system.The better the starting performance and the higher The better starting performance and the higher accuracy of the rotor detection can improve the operation performance of motors.In this paper,based on the vector control of sensorless brushless DC motor,the motor control system of automatic lawn mower is designed to realize the function of controller start and FOC control without Hall sensor.Mainly complete the following work:(1)Selection of non-inductive BLDCM motors: Brushless DC motors need to choose the appropriate model motor according to different application environments.This application is a lawn mower,so the motor with a power of 500 W and a rated current of 13 A is the most Suitable.(2)Start-up scheme for brushless DC motors without induction: BLDCM is different from BLDCM with brushless DC motors.The motor itself does not have a Hall sensor or encoder.The startup parameters need to be designed according to the characteristics of the motor.The designed software model achieves the purpose of starting.(3)Non-inductive FOC design: FOC control strategy can greatly reduce the noise of the motor,improve the stability of the motor operation,and increase the effective power of the motor.The speed/current double closed-loop design of the non-inductive FOC control strategy,the detection of the non-inductive BLDCM speed position and the establishment of the space vector pulse width modulation(SVPWM)model.(4)Computer simulation: simulate the motor design algorithm.The design of the program was carried out before the software was written.The implementability of the program needs to be verified by simulation.After the code is completed,the software code is revised in conjunction with the simulation results in order to achieve the desired effect of motor control during actual execution.(5)Control hardware design: The hardware design of the control system is the basis of software design.The core circuit in hardware design includes power module,inverter bridge,inverter drive module,current sampling,hardware overcurrent protection and other functional module design;the rationality of hardware circuit design is more important than the design of PCB,according to the application object and Control needs to select key components.(6)Control software design: According to the design idea of high cohesion and low coupling,the software design needs to reasonably write functional module code to reduce the code coupling degree between each module.The software of the control system mainly includes the design of the following modules: sensorless start algorithm design,motor position estimation,FOC control algorithm,and design of speed closed-loop function code according to the requirements of the lawn mower.Combined with the lawn mower to debug the hardware and software of the motor,complete the start-up and speed regulation of the non-inductive BLDCM,so that the control can meet the control needs of the lawn mower.