Extended Kalman Filter is an exceptional observer which offers optimal filtering of noises in measurement and inside system if the covariance's of these noises are known. Also, initial rotor position is not necessary for start-up. By a proper compensation in observer equation, other unexpected equivalent points of observer are moved off. Motor can start up successfully from any unknown position.It provides an effective way of improving robustness of control system against parameter variation, load disturbance and measurement error due to its simple structure and fast response. It...