A 12-Step Sensorless Drive for Brushless DC Motors Based on Back-EMF Differences

Samuel Wang, An-Chen Lee

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


This paper presents a new 12-step sensorless drive for brushless dc motor based on back-electromotive force (back-EMF) differences, which are estimated from 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 from 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 the motor in lower speed, and performs better under different speed and load torque as compared with the conventional method.

Original languageEnglish
Article number6975137
Pages (from-to)646-654
Number of pages9
JournalIEEE Transactions on Energy Conversion
Issue number2
StatePublished - 1 Jun 2015


  • Back electromotive force (back-EMF) detection
  • back electromotive force differences
  • brushless dc motor (BLDC)
  • delay compensation
  • disturbance observer (DOB)
  • sensorless control
  • torque ripple

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