Simulation Study of Sensor Less Speed Control for Brushless DC Motor

This paper proposes a mathematical modeling approach for the Back-Electromotive force (Back-EMF) observer and its implementation on Matrix Laboratory (MATLAB) to address the challenge of predicting the back EMF spectrum for Brushless Direct current (BLDC) motors driven under light load conditions. The observer uses the trapezoidal back EMF of BLDC motors to determine the rotor position, which is estimated through an unknown input observer. The sensor less speed control of the BLDC motor is achieved using this input observer. The paper describes the Back-EMF scheme, Back-EMF observer, commutation function, speed, and position estimation, as well as the structure of the entire system. The simulation results validate the observer, and it is shown to be useful in understanding the behavior of a permanent magnet brushless DC motor in terms of state variables, inputs, and outputs. Study and analysis shows that the method can be easily incorporated into software systems for simulating and controlling motors. Its real time implementation can offer significant advantages, including high efficiency, cost- effectiveness, and the elimination of non-realizable heating issues.