Fast, real-time monitoring of rotating machines using digital motion control coprocessors

This paper describes the use of methods and techniques that have been developed for high-performance control of relatively small and slow turning industrial machines and extend these techniques to the more demanding regime of AC machines used for kinetic energy storage and fast AC servos for military applications. In particular this paper describes a technique for fast monitoring of the output voltage of AC generators. To accomplish fast monitoring, the (sinusoidal) AC output voltage is converted to a DC quantity that represents the instantaneous amplitude. This is achieved through the use of a rotational transformation. This transformation, also called "vector rotation," can be used for very fast observation of the momentary amplitudes of all electrical machine quantities, such that averaging of the AC value (to determine "momentary average" rms amplitude) is not necessary. The procedure is implemented by tightly integrating a digital motion control coprocessor into the memory map of a 16-bit microcontroller.