A novel two degree-of-freedom Smith predictor for multivariable systems with multiple time delays

In this paper, a recently proposed multivariable Smith predictor scheme is modified, which leads to the remarkable improvement of regulatory capacity for both servo and regulatory performance. In the proposed scheme, a disturbance estimator is utilized to construct the closed-loop between the plant inputs and outputs for load disturbance rejection. As a result, the nominal set-point responses are decoupled from the load disturbance responses and both of which can be optimized independently. Since there is an open-loop control for the nominal set-point tracking, the nominal system stability can be easily identified. At the same time, robust stability analysis for the proposed control structure is provided in the presence of the process multiplicative uncertainties. Simulation example is included to demonstrate the superiority of the proposed control scheme.