Abstract-The zero crossing detection is essential in twelve sensorsless control using back-EMF. To increase output power of Brushless DC motor (BLDCM), traditional twelve step control has extended active angular period. It has drawback which become unstable the performance of the drive system in rated load condition because a period for detecting zero crossing point of terminal voltage is reduced. To solve this problem, this paper proposes the advanced twelve step sensor-less control of a BLDCM using field oriented control (FOC), which combines the traditional twelve step sensor-less drive scheme and single shunt three phase current reconstruction algorithm. The effectiveness of this proposed control is verified by the simulation and experiment result according to the comparison of the output characteristics between the traditional and proposed control.

In electric power steering (EPS), spoke type brushless ac (BLAC) motors offer distinct advantages over other electric motor types in terms torque smoothness, reliability and efficiency. This paper deals with the shape optimization of spoke type BLAC motor, in order to reduce cogging torque. This paper examines 3 step skewing rotor angle, optimizing rotor core edge and rotor overlap length for reducing cogging torque in spoke type BLAC motor. The methods were applied to existing machine designs and their performance was calculated using finite-element analysis (FEA). Prototypes of the machine designs were constructed and experimental results obtained. It is shown that the FEA predicted the cogging torque to be nearly reduce using those method.