A Unified Frequency Domain Method for Designing Robust Decentralized Controllers

The paper presents a unified frequency-domain methodology for designing robust continuous-and discrete-time controllers for both MIMO and SISO uncertain systems. The generalized design procedure is based on the Equivalent Subsystems Method (ESM) – a frequency-domain decentralized controller design method guaranteeing required performance for the full system. Plant-wide performance specification in terms of maximum overshoot and settling time is translated into frequency domain performance measures (phase margin and bandwidth frequency). Generating equivalent subsystems allows applying independent design of the resulting decentralized controller for both SISO and MIMO systems. Robust stability conditions are integrated in the ESM. The design procedure is applied to design a discrete-time robust decentralized PID controller for a non-minimum phase system.