Intelligent Control of High-Speed Sensorless Brushless DC Motor for Intelligent Automobiles

Abstract

For the last decade, the need for electric driven vehicle has risen rapidly due to the global warming problem. A high efficient motor need to be developed to replace traditional engine. In this paper, the authors present a fuzzy logic controller (FLC) for sensorless brushless dc (BLDC) motor. The proposed FLC is based on the terminal voltage measurement as the sensorless method for BLDC motor control. There are two modules designed in the speed control of BLDC motor, i.e. command and regulating modules. Command module is to find and issue commutation period and PWM duty cycle to the BLDC motor for desired speed. The regulating module is designed by applying a FLC with sensorless tenchnology and is used to regulate the speed of BLDC motor under various disturbances, such as loading effect. Two resistances are adopted to detect the zero-crossing point (ZCP) of back-EMF signal on the unexcited phase instead of using the expensive Hall sensors. The regulating module can regulate accurately and quickly the PWM duty cycle by fuzzy reasoning which makes the BLDC motor rotate smoothly at desired rotation speed even there exists an external disturbance. In order to reduce the computational load of realtime FLC for the microcontroller C8051F330, we can perform the FLC computation off-line to cover nearly all cases. These data will be recorded and organized as a Look-Up Table (LUT). This paper shows that a regulating module designed by FLC is better than a none regulation module or a regulating module with a P controller.