An Industrial Adaptive PID Controller

This paper presents a new industrial adaptive PID controller. The controller has the PID structure, with dual rate sampling, which means that the sampling rate for the PID controller is significantly higher than the sampling rate in the parameter estimator. The controller differs from conventional parametric adaptive controllers because it is based on estimation of transfer function properties. For normal industrial process control the adaptive controller can be used without any prior information about the process dynamics, such as sampling period, closed loop pole assignments etc. This is achieved by using a relay auto-tuner to initialize the controller. The auto-tuner determines a point on the Nyquist curve where the phaselag is close to 180°. This point on the Nyquist curve is then tracked by the parameter estimator.