Sensorless Control based on Sliding Mode Observer for PMSM drive

An ideal sensorless drive gives accurate speed information and control of speed, ranging from zero to the highest for all operating conditions irrespective of the uncertainties or disturbances present. Mechanical sensors which are used for tracking rotor position makes the system costly and less reliable. Therefore in high-performance drives, sensorless control methods are used for estimation or observation of speed and position. As hall effect sensors are used for measuring the stator currents, its actual value and estimated value can be used for adaptation. Stator current are used to estimate the correct speed and error of the drive. By using a continuous switching function called sigmoid (in place of signum function), chattering is reduced considerably. A Lyapunov function is constructed to analyze the stability of the proposed SMO. Extensive simulations are carried out and an SMO based sensorless drive is proved to be robust against parameter fluctuations and uncertainties.