Direct synthesis based tuning of the parallel control structure for integrating processes

A controller tuned for servo/regulatory application gives significant performance degradation when used for regulatory/servo purpose. The degradation in the overall performance can be minimised by a two degree-of-freedom control structure. The parallel control structure reported recently decouples set-point tracking from disturbance rejection. In the present work, the two controllers of parallel control structure are designed using direct synthesis approach to achieve robust closed-loop performance for a class of integrating processes. Simulation examples show that improved servo and regulatory performances are achieved by the proposed method as compared to the recently reported strategies when the controllers are tuned to have the same degree of robustness.