A Design Of The Closed-loop Control System For Sensor-less Brushless DC Motor

Drones have many advantages.They are easy to control and have good maneuverability.Recently,the application of drones is becoming increasingly popular.The technology is undergoing rapid development as well.The driving system of drones is the guarantee for the drones to complete the navigation task,while its dynamic performance and its steady-state accuracy determine the performance.Along with the continuous development of drones,higher requirements are put forward for the driving system.However,closed-loop speed regulation designs are quite rare in the current motor driver schemes.Therefore,the performance of the system cannot be guaranteed.In this paper,a dual closed-loop motor driving system for drones is designed.The control algorithm and the anti-disturbance performance are analyzed.The main contents are as follows:(1)In order to get the whole picture of the brushless DC motor driving system,the fundamental principles of the sensor-less brushless DC motor are analyzed.Also,the differences between driving mode in sine wave and square wave are introduced.Then the mathematical model of sensor-less brushless DC motor in square-wave driving mode is established.(2)The system is simulated and analyzed by MATLAB software to evaluate the feasibility of the design first.According to the mathematical model of sensor-less brushless DC motor,a dual closed-loop driving system is designed.The speed loop is designed with fuzzy PID controller and adaptive integral sliding mode controller respectively while the current loop is designed with PID controller.Then a Simulink scheme based on the above controllers is built and simulated.Torque disturbance of estimated wind disturbance is added to the simulation process.By adjusting PID parameters and weakening chattering phenomenon in sliding mode control using reaching law and switching function replacement,the dynamic performance and the steady-state accuracy of the system are improved.Simulation results of the two controllers are compared,and it turns out that adaptive integral sliding mode control has better anti-disturbance performance.(3)According to the overall design requirements,the hardware and the software design of the motor driving system are completed.The design of hardware includes power module,control circuit module,inverter module and sampling module.In the selection of devices,devices with good performance and small size are selected,and corresponding peripheral circuits are carefully designed.The design of software includes startup program,back-EMF commutation program,closed-loop control program and sampling program.Furthermore,the closed-loop control program includes fuzzy PID controller and adaptive integral sliding mode controller.The ideas and the flow charts of each subsystem are introduced in detail.(4)On the basis of hardware and the software design,an experimental platform is built.Several phenomena in the test design circuit are analyzed,and relevant improvements are made to further improve the system.Experiments under different controllers,blades and wind velocities are carried out and it turns out that the system is stable in the fourth level wind field and the experiments verify the feasibility of the system.