Robust adaptive PI controllers for processes with large dead-time

This paper presents a technique of adaptive PI controller for processes with large dead-time. With the process input and output data of normal operation in the control loop, the important frequency responses of process are estimated with signal decomposition and analysis, and then a first-order plus dead-time transform function is identified for the processes with large dead-time. Finally PI control parameters are calculated to satisfy both phase and amplitude margins. The adaptive procedure of PI controller doesn´t need any prior knowledge of the process and the control loop is still in the normal operation. Simulation examples are given to show both effectiveness and feasibility of the adaptive controller.