Double-loop control structure for oscillatory systems: Improved PID tuning via multi-scale control scheme

Systems that exhibit oscillatory behaviours are commonly encountered in practice. The stabilization and good control performance of highly oscillatory systems are difficult to achieve using the single-loop feedback control structure. This paper presents a simple design procedure based on a double-loop control structure for the highly oscillatory systems. The double-loop control system consists of two controllers: (a) a damping controller which converts an underdamped system to an overdamped system, and (2) a main controller which is tuned to achieve specified performance-robustness. An advantage of the proposed control scheme over some other existing schemes lies in its simplicity and robust performance.