Design of digital control systems with two-time-scale motions

The problem of digital controller design is discussed. The design method is based on the formation of two-time scale motions in the closed loop system. It is shown that, if a sufficient time-scale separation between the fast and slow modes in the discussed closed loop system and stability of fast modes are provided, then slow modes have the desired form. Thus, the output transient performance indices are insensitive to external disturbances. Relationships for control accuracy analysis and choice of the sampling period are obtained. Finally, an example with simulation results is presented.