Real-time Digital Control of Time-delay Systems: from Smith Predictor to MPC

Many processes in industry exhibit time-delay in their dynamic behavior. Time-delay is mainly caused by the time required to transport energy, information or mass, but it can be caused by processing time as well. The typical process with time delay is a heat exchanger that is a specialized device that assists in the transfer of heat from one fluid to the other. This paper deals with design of universal digital controller algorithms for control of a great deal of processes with time-delay. The first algorithm is realized by the digital Smith Predictor (SP) based on polynomial approach - Linear Quadratic (LQ) method. The second algorithm utilizes Model Predictive Control (WPC) approach with the possibility of measurable disturbance compensation. Both control principles were tested by a real-time control of an experimental laboratory heat exchanger.