SELF-TUNING CONTROLLER

Apparatus and method for adapting the control parameters of a self-tuning controller. The apparatus detects a closed-loop response to a naturally occurring, unmeasured disturbance and determines two characteristics, the attenuation and the period of the response. The attenuation and the period provide sufficient information to partially identify the characteristic equation of the closed-loop system. The apparatus constructs from the partially identified characteristic equation a process model that represents the general behavior of the process. The apparatus generates new control parameters more appropriate for the identified process model, and appropriately updates the controller.