Hybrid Speed Control of Sensorless Brushless Dc Motor with Fuzzy-Based Estimation

This paper describes a simple way to control the Brushless DC (BLDC) motor for electrical applications. To control this machine, it is generally required to measure the speed and position of the rotor by using the sensor, because the inverter phases acting at any time must be commutated depending on the rotor position. Encoders and resolvers have been used for sensing the rotor position with respect to the stator. These sensors, however, make the motor system more complicated and mechanically unreliable. A method for the estimation of the speed and rotor position of a BLDC motor is presented in this paper. Fuzzy-based back-EMF observer is employed to estimate the speed by using measurements of the stator line voltage and line current. Most existing sensorless methods of the BLDC motor have low performance in a transient state or low-speed range and occasionally require an additional circuit. To overcome this problem, the estimation of back-EMF is carried out by fuzzy logic techniques to improve the performance of the system. This method proposes a back-EMF observer based on fuzzy function approximation and the system state equation of the BLDC motor and describes a fuzzy logic approach to design a Hybrid Controller (HC) for variable speeds of a BLDC motor. Here, Proportional Integral (PI) controller is tuned by the fuzzy logic technique. The fuzzy logic tuner is used to adjust the two gains of the PI controller. In this approach, the fuzzy tuning of the gains of a conventional PI controller is achieved through fuzzy rules deduced from many simulation tests applied to BLDC motor, for a variety of operating conditions. Experimental results show that the proposed fuzzy-tuning PI controller is better than the controller with fixed gains in terms of robustness and speed rise time even under great variations of operating conditions and load disturbance