Back-EMF-Based Sensorless Control Using the Hijacker Algorithm for Full Speed Range of the Motor Drive in Electrified Automobile Systems

This paper presents an open-loop control strategy, dubbed the Hijacker algorithm, which governs startup from standstill, low-speed operation in open-loop, the transition to closed-loop, and sensorless motor control. The goal of the Hijacker is to eliminate the torque ripple encountered by a sudden switch from the open to closed loop operation, providing a smooth transition between the two control mechanisms and reliable operation over the motor's entire speed range without the use, or added cost of speed/position sensors. Implementation of the Hijacker exhibits extreme simplicity, so as not to add heavy computational loads on the processor. The algorithm, along with its development and justification, is then validated through both simulation and the test bench using a 1.4-kW/4500 rpm brushless dc motor.