An efficient observer model for field oriented induction motor control

An observer is needed in field-oriented induction motor control as the phase angle of rotor magnetising current or m.m.f. vector in a standard induction motor cannot be measured by direct means. Two types of observers (linear and non-linear) are used in field-oriented induction motor control schemes as can be found in literature. The reduced-order linear model of the observer is easy to implement in real time, but it does not give an accurate estimation of m.m.f. vector angle, β, since the induction motor operates in the region of saturation. The non-linear model which incorporates this effect of magnetic saturation of the induction motor cannot be practically implemented as it takes too long a time to estimate the angle β. This paper presents a real-time computationally-efficient observer based on artificial neural networks (ANN) which takes into account the effect of saturation and estimates the angle β in a few microseconds which is well within the real time deadline