Abstract
As the technology advances along with civilization, electric motors has gained increasing applications in our lives; meanwhile, because brushless DC motors (BLDCM) are so advantageous compared to conventional motors together with advent of new design and material technology, the costs of BLDCM has reduced significantly so that many commercial products have adopted BLDCM today. But, Hall sensors, serving as the key magnetic pole detection devices in BLDCM, have been assessed with comments for low sensitivity and high temperature drifts. On the contrast, magneto-resistance sensors have high magnetic sensitivity so that the location of sensors can be selected for lower working temperature. In this thesis, we want to assess the applicability of replacing hall sensors with magneto-resistance sensors under the condition of not modifying the motor drivers. First, we have tested the characteristics of commercially available GMR sensors for qualifying the specification of the sensors. After validating the characteristic of the GMR sensors, we have measured the magnetic flux of a BLDCM rotor via the GMR sensors. Then, by numerical simulations for the motor rotor, we confirmed the experimental results are agreeable to the simulations. Finally, we have finished the design of signal processing circuits and proved the feasibility of driving BLDCM with GMR sensors as the rotor position detectors.