On-line retuning of PID controllers with fixed threshold samplers.

The appearance of limit cycle oscillations in control systems with fixed threshold based samplers degrades the performance of the control loop, accelerates the wear out of actuators, and introduces an unnecessary communication overhead in distributed control systems. In this paper, the role of the input signals to the control loop is taken into account when analyzing the existence of limit cycles induced by fixed threshold samplers. With this analysis, a methodology to re-tune PID controllers while running to avoid limit cycle oscillations generated by ramp-like excitation signals is presented. Implementation guidelines and several examples to illustrate the usefulness of the method are provided. • Biased limit cycle oscillations induced in a kind of fixed sampled loops are studied. • A methodology to retune the controller to correct the bias effect is proposed. • The robustness assured by the original controller is granted after the retuning. • The method is applicable to the most commonly found controllers in industry. [ABSTRACT FROM AUTHOR]