Discrete smith predictor design and performance improvement of PID tuning
This paper presents a realization of a PLC-based Smith predictor control scheme on the Siemens S7 platform. The Smith predictor consists of a process model and a pure dead time element. The process model represents a first order plus dead time – FOPDT approximation of the actual process dynamics. Many technological processes can be approximated reasonably accurately with a FOPDT dynamic model. Even if the process to be controlled is not first order in its nature a FOPDT Smith predictor still can be used to provide better loop response. Advanced control structures are seldom used in processes controlled by a single PLC. Significant improvements can be made in the quality of the final products in manufacturing by reducing process performance variability.