Torque control of brushless DC motors applied to electric vehicles

This paper presents a high-performance torque control system for brushless DC motors applied to electric scooters, with the aim of achieving similar output characteristics to that of continuously variable transmissions. Due to the fact that brushless DC motors applied to electric vehicles requires a wide range of operating speeds, phase advance control and field weakening control techniques are adopted in this paper. For the practical application of electric scooters, the control scheme uses only one current sensor to measure the DC bus current to achieve torque control, instead of two current sensors for three phase currents. Also three position Hall sensors are used to perform phase advance control and field weakening control, instead of an expensive encoder. Both the theoretical derivation and experimental verification for the proposed control scheme are presented in this paper, where the hardware implementation is carried out based on a three phase permanent magnet motor and a TI TMS320F240 digital signal processor.