Initial Rotor Position Detection For BLDCM Based On Coupling Injection Of High-Frequency Signal

Because of its simple structure,reliable operation and high efficiency,brushless DC motors(BLDCM)has been widely used in aerospace,rail transit,automotive electronics and household appliances.The determination of the initial rotor position is the basis of stable starting without reversing,and directly affects the maximum starting torque and the minimum starting time of the motor.If the initial rotor position can not be accurately detected,it will lead to motor inversion,excessive starting current,starting failure and so on.In order to detect the initial rotor position when the motor is at rest,this paper proposes an initial rotor position detection method based on high frequency signal coupling injection,using the relationship between three-phase winding inductances and the rotor position.This method detects the relationship of three-phase winding inductances by injecting high-frequency detection signals into the motor windings in a coupled way,and the rotor position can be determined into two sectors with 180 degrees electric angle difference.Then,the polarity of the permanent magnet rotor is determined by applying two opposite voltage vectors to motor windings,so that the initial rotor position is determined into a unique sector,and the positioning accuracy is 30 degrees electric angle.Compared with the existing methods,the proposed method breaks through the limitations of fixed DC voltage and limited switching frequency of inverters by coupling injection,thus significantly reduces the amplitude of the detection signal while increases its frequency.Therefore,the electromagnetic torque generated in the process of position detection can be effectively reduced while accurately detecting the initial rotor position,and the possibility of misrotation of the rotor in the process of initial position detection can be reduced.Finally,an experimental platform with DSP and FPGA as the main controller is built,and the proposed method is verified experimentally under different rotor positions.The experimental results show that the proposed method can accurately detect the initial rotor position under different conditions.