Adaptive PID controllers with specifications on phase and amplitude margins

This paper presents a new technique of adaptive PID controller with specifications on phase and amplitude margins. 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 both phase and amplitude margins. 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.