Rotor position estimation in a bldc motor at low speed using g-functions and extended state observers

This article presents a rotor position estimation scheme for a brushless direct current motor. This strategy is based on the construction of the so-called G functions, which fulfill the same objective of the commonly used Hall effect sensors, which is determine the switching logic to operate BLDC motors as a simple DC motor. Since these new switching pulses, derive from the G-functions processing, can ideally be determined independently of the motor speed, thus a good low speed performance is achieved. Additionally, this methodology is improved using extended state observers to avoid problems associated with the calculation of derivatives of the phase to phase motor currents.