Control of Stable Processes with Dead Time for Deterministic Disturbance Rejection

This paper proposes a new modified discrete Smith predictor control scheme for stable processes with dead time. The processes are assumed to be of stable first order with time delay, which are commonly used in process industry. The present scheme consists of two parts: predictive disturbance observer (PDOB) and Smith predictor structure. The PDOB scheme exhibits the property of DOB structure which can push the real plant to the nominal plant. Moreover, the PDOB based on DOB structure has an additional predictive filter which can eliminate the time delay of estimated disturbance, so that the control scheme could compensate deterministic disturbances in dead-time processes. Meanwhile, the Smith predictor structure in the outer loop is utilized to suppress the effects of time delay. In order to demonstrate the results, different simulation examples for periodic disturbance rejection are shown. The results illustrate that the performance of proposed scheme is better than the recent study for periodic disturbance rejection. Keywordsdead time; Smith predictor; PDOB; periodic disturbance; robust stability;