A Novel and Simple Hybrid Fuzzy/PI Controller for Brushless DC Motor Drives

A novel speed controller for the trapezoidal three-phase Brushless DC (BLDC) Motor Drive is proposed using a hybrid fuzzy logic/proportional plus integral (PI) control. The structure of the fuzzy logic controller is different from conventional fuzzy logic implementations such that it only uses three simple rules based on speed error being either in the positive, negative or zero regions. The controller outputs a reference current, that is enforced through the motor phases by pulsewidth modulation (PWM) control. The proposed fuzzy logic controller can be used individually in applications requiring lower computation load and tolerating small steady state offset. For high performance applications requiring offset free tracking, a PI controller is augmented with the fuzzy logic controller and a simple switching scheme is devised based on error variance to select the active controller based on operating conditions. The response of the drive system under the proposed composite control structure is compared with the conventional PI based and the sliding mode controllers to demonstrate its improved performance. Simulations studies using detailed models in MATLAB/Simulink's SimPowerSystems toolbox are carried out to show the validity of proposed control.