EXPERIMENTAL NONLINEAR TORQUE CONTROL OF A PERMANENT-MAGNET SYNCHRONOUS MOTOR USING SALIENCY

In this paper, a new nonlinear control strategy is proposed for a perm anent-magnet salient-pole synchronous motor, This control strategy sim ultaneously achieves accurate torque control and copper losses minimiz ation without recurring to an internal current loop nor to any feedfor ward compensation. It takes advantage of the rotor saliency by allowin g the current (i(d)) to have nonzero values. This, in turn, allows us to increase the power factor of the machine and to raise the maximum a dmissible torque. We apply input-output linearization techniques where the inputs are the stator voltages and the outputs are the torque and a judiciously chosen new output. This new output insures a well-defin ed relative degree and is linked to the copper losses in such a way th at, when forced to zero, it leads to maximum machine efficiency. The p erformance of our nonlinear controller is demonstrated by a real-time implementation using a digital signal processor (DSP) chip on a perman ent-magnet salient-pole synchronous motor with sinusoidal flux distrib ution. The results are compared to the ones obtained with a scheme whi ch forces the i(d) current to zero.