Optimal speed control of synchronous motors based on feedback linearization

The authors propose a linearizing speed control of synchronous motors with constant excitation. The proposed control scheme involves, nonlinear feedback and position-dependent coordinates transformation, which decouple the nonlinear interaction between the d and q axes and takes a model of the synchronous motor into a linear time invariant system. A design method for a speed controller based on the linearized system is discussed. The authors apply the linear quadratic optimal regulator theory with integral action in order to obtain high dynamic performance. It is shown that the linearizing control makes it possible to utilize the advantage of the quadratic optimal regulator. The authors implemented the proposed control scheme as a fully digitalized software servo system by using a digital signal processor. The superior performance of the proposed control method is confirmed through experiments