Adaptive PID controllers with robustness specifications

This paper presents a new technique of adaptive PID controller with gain- phase margin or sensitivity specification. On the basis of process input and output data of normal operation in the control loop, the important frequency responses of process are estimated with signal decomposition and Laplace analysis, and then a second-order plus dead-time transform function is identified as well. Finally PID control parameters are calculated to satisfy gain-phase margin or sensitivity specification. The adaptive procedure of PID controller does not need any prior knowledge of the process and previous controller while the control loop is still in the normal operation. Simulation examples are given to show both effectiveness and feasibility of the adaptive PID controller.