Sensorless Field-Oriented Control of High-Speed Low-Inductance Motors for Small Unmanned Quadcopters

This paper presents an application of sensorless field-oriented control (FOC) for high-speed, low-inductance motors used in small, unmanned quadcopters. The motors in such applications are usually high pole count BLDC motors with an outrunner rotor. The electronic speed controllers (ESC) generally adopt a sensorless six-step commutation algorithm based on the back-EMF zero crossing. While simple and computationally inexpensive, this type of algorithm has numerous issues such as low efficiency, increased torque ripple, issues at low speed and more. This in turn leads to reduced flight time, noisy operation and increased losses due to heating of the motor. The goal of this work is to implement a sensorless field-oriented control algorithm and study its performance.