Abstract—This paper presents a new 12-step sensorless drive for

brushless dcmotor based on back-electromotive force (back-EMF)

differences, which are estimated the disturbance observer

(DOB) structure. Availability of rotor position information with

a resolution of 30° and commutation without phase shift are the

advantages of using the back-EMF differences. Unlike the conventional

methods that obtain part of the back-EMF signal the

manipulation of three phase voltages, the proposed DOB structure

can access the entire back-EMF profile. By designing a proper

low-pass filter in the DOB structure, the back-EMF difference can

be well detected with lower sensor noise. Compensation of delay

commutation introduced by the filter is also discussed. Experiment

results showed that the proposed sensorless drive is capable of running

themotor in lower speed, and performs better under different

speed and load torque as compared with the conventional method.-Abstract—This paper presents a new 12-step sensorless drive for

brushless dcmotor based on back-electromotive force (back-EMF)

differences, which are estimated　the disturbance observer

(DOB) structure. Availability of rotor position information with

a resolution of 30° and commutation without phase shift are the

advantages of using the back-EMF differences. Unlike the conventional

methods that obtain part of the back-EMF signal　the

manipulation of three phase voltages, the proposed DOB structure

can access the entire back-EMF profile. By designing a proper

low-pass filter in the DOB structure, the back-EMF difference can

be well detected with lower sensor noise. Compensation of delay

commutation introduced by the filter is also discussed. Experiment

results showed that the proposed sensorless drive is capable of running

themotor in lower speed, and performs better under different

speed and load torque as compared with the conventional method.