To solve problem of difficulty of rotor position observation under the sensorless control of fan load at low speed

the impedance matrix of the controlled motor in the rotating synchronous coordinate system is deformed symmetrically according to the characteristics of fan load. The brushless DC motor is used to reconstruct the mathematical model in the two-phase static coordinate system. According to the back-EMF of the motor at low speed both correlate with the differential value of the motor speed and stator current differential value

the sliding mode observer based on saturation function is designed to realize the observation of rotor angle and velocity information at low speed. Combined with the fan load characteristics

control system and rotor position observer

the system simulation is carried out

and the hardware driver controller is made based on STM32 F302 C8 T6 chip. After experiment

the results are analyzed

and the feasibility of the control system is verified.