Design of Cascade-Smith Hybrid Control Structure for Pressure Control

Abstract

A new hybrid-control structure for the compensation of the volume-delay negative effect in the mixed-gas pressure control is designed. The volume-delay mechanism is discussed. A Smith predictor is used in the primary loop of a cascade control system where the secondary loop has a negligible delay while the primary loop has a significant and variant delay. To deal with the sensitivity of Smith predictor to modeling error, the gas pipe model for the Smith predictor can be updated by measuring the gas pressure and choosing the model characteristics through a lookup table. The results show that the proposed control structure brings together the best merits of a cascade control and the Smith predictor structure, and it can provide a better performance than the traditional cascade control.