Position estimator for a brushless‐DC machine using core saturation and stator current slopes

Abstract

Purpose -This paper is devoted to the investigation of position estimation for a brushless DC machine using only their stator currents. The first application is for a hybrid electric vehicle, where the generator will be used as a motor to start the internal combustion engine (ICE). Design/methodology/approach -This paper describes how to estimate the rotor position of a brushless DC (BLDC). Two different strategies, both based on stator currents, will be used: one for low speeds to start the ICE, and one for normal speeds for future applications in a pure electric vehicle (EV). The first one uses an estimation method based on core saturation and the second one is based on the determination of the current slopes on two of the three phases. The algorithms proposed neither needs to measure any machine parameters, nor the back emf. The methods use the information contained in the current magnitudes and slopes, and the machine mechanical speed. The system was implemented using a Digital Signal Processor (TMS320F241), which controls the phase currents and makes all the calculations required for position estimation. Additionally, the PWM signals are transmitted through a fiber optic link to minimize noise production and error on commutations. Findings -The papers shows how an internal combustion engine can start using this approach in a brushless motor and keep it synchronized. Research limitations/implications -This work is being applied to a hybrid electric vehicle. Originality/value -The paper proposes a new way to start the internal combustion engine for hybrid vehicle applications through the estimation of the magnet's position. It also shows a way to estimate the position at other speeds for battery charging of the vehicle.