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 (MPC) approach with the possibility of measurable disturbance compensation. Both control principles were tested by a real-time control of an experimental laboratory heat exchanger.