INTRODUCING A NOVEL AUTO-TUNER AS AN EDUCATIONAL TOOL

This paper presents 2 student projects regarding a recently developed extension of the widely used relay-feedback PID auto-tuner. The proposed method consists of two steps: process identification and controller design. First, a non-iterative procedure is suggested for identification of two points on the process Nyquist curve. A second-order-plus-dead-time model is obtained and then used for PID controller design based on the internal model principle (IMC). For the identification of the two points on the Nyquist curve a pure relay in the feedback loop (as used in standard auto-tuning) and a relay which operates on the integral of the error are used. The method is illustrated on two applications: a continuous stirred tank reactor and a boost DC-DC converter. These examples are relevant for the students following the basic course in control engineering. The influence of changing a design parameter — the desired closed loop behaviour — is shown. The several tuning options lead to changes in the performance, making the method a useful tool in control education.